some new thoughts ocean boundariesocean boundaries in agso’s sights april 2000 issue no. 57 pp...

Oceanboundariesin AGSOrsquos sights

APRIL 2000 ISSUE No 57

PP

25

50

03

00

04

8

Mineral provincessome new thoughts

Also Sun activity peaks perfect zircon found great new CD plus much more

Taiwanrsquos BIG shock

RABAUL VOLCANOESf ire passion

AusGEO news (APRIL 57) 22500 303 PM

A U S G E O N e w sApril 2000 issue no 57

Editor Julie Wissmann

Graphic Designer Karin Weiss

Photographer Brett Ellis

This publication is issued free ofcharge It is published six times a yearby the Australian Geological SurveyOrganisation

The views expressed in AUSGEONews are not necessarily those ofAGSO or the editor and should not bequoted as such Every care is taken toreproduce articles as accurately aspossible but AGSO accepts noresponsibility for errors omissions orinaccuracies

copy Commonwealth of Australia 2000

ISSN 1035-9338

Printed in Canberra by National Capital Printing

Australian Geological SurveyOrganisationGPO Box 378Canberra ACT 2601Australia

cnr Jerrabomberra Ave amp Hindmarsh DrSymonston ACT 2609Australia

Internet wwwagsogovau

Chief Executive OfficerDr Neil Williams

SubscriptionsDave HarrisPhone +61 2 6249 9333Fax +61 2 6249 9982E-mail daveharrisagsogovau

AGSO productsJudy Kley Chris ThompsonPhone +61 2 6249 9519Fax +61 2 6249 9982E-mail salesagsogovau

Editorial enquiriesJulie WissmannPhone +61 2 6249 9249Fax +61 2 6249 9984E-mail juliewissmannagsogovau

AUSGEO News is available on the web at wwwagsogovauinformationausgeonews

Minerals Open Days3Orientation change gives Broken Hill new prospects 3

Mineral provinces crustal geometry subject of major seismic research 4

Yilgarn mapping provides golden opportunity 6

Gravity properly planned is a precision tool 8

Mineral resources and advice activities AGSOrsquos role extended 15

FeaturesSurges blackouts but glowing skies as sun activity peaks 9

Seabed images off south-east Australia a first 22

Picture builds for Australiarsquos eastern limits 24

Speakers10Big earthquake rouses Taiwan 10

Rabaul volcanoes fire 30-year passion 12

Around the divisions 18

Workshops and seminars 26

Events calendar28

Product news29

Lord Howe Island in sight AGSO scientists arebusy mapping Australiarsquos eastern seabedjurisdiction Photo taken from the deck of Frenchresearch vessel LrsquoAtalante See article page 22

Photo Peter Hill leader of the AUSTREA-1 cruise

CONTENTS

AusGEO news (APRIL 57) 22500 303 PM Page 2

M I N E R A L S O P E N D A Y S

There are two major barriers to exploration in the Broken Hill-Olaryregion says Dr Gibson commonly held beliefs about the regional structureand interpretations of the aeromagnetics

The Broken Hill region known for its silver lead and zinc deposits isdominated by structures formed during two deformational events (D2 andD3) This deformation sequence is superimposed upon an earlier historyof basin formation and contemporaneous bimodal magmatism at 1710ndash1690 million years ago

Moreover while sedimentation happened at a higher level mafic andfelsic magmas were intruded at deeper levels Later this basin invertedeither during D1 or D2 deformation D2 structures in the northern part ofBroken Hill region are shallow dipping and verge towards the north-eastmdashabout 90 degrees to that commonly believed

At a later stage (c 1580ndash1570 Ma) these structures are overprinted bynorth-west verging D3 shear zones and thrust faults that overprint theshallower dipping D2 structures The D3 deformation is thus more or lessorthogonal to earlier D2 structures

For years many thought most shear zones around Broken Hill dippedtowards the north-west Through seismic surveys and detailed structuralmapping Dr Gibson and the BHEI team tested this interpretation Resultsconfirm a south-east dip for the D3 shear zones diametrically opposite topreviously held viewpoints

Dr Gibson believes that this new information about the orientation ofmajor structures is important because some shear zones in the Broken Hillregion (eg Apollyon Valley shear zone) are associated with significantbase-metal mineralisation

lsquoWe believe that many of these shear zones are high-temperaturestructures that focused fluid flow and most were subsequentlyreactivatedrsquo he says

lsquoBut the important point is that they dip towards the south-east and inbetween you can see flat structures that we think represent bedding or theearlier D2 regional fabricrsquo

Dr Gibson says there has been a lot of emphasis on stratabound orstratiform mineralisation He believes mineral exploration companies mighthave further success if they lsquobroaden their horizonsrsquo

Edi tor rsquos noteMinerals Open Days heldDecember 7ndash8 last year were aprime opportunity for participantsfrom industry and State Surveys tomeet staff and influence thedirection and types of projectsundertaken by AGSOrsquos MineralsDivision in coming years

As promised in this issue welook at further presentations fromthose two days

You may have noticed that twomajor projects have not beencoveredmdashGilmore and NABREThey will be larger articles incoming issues

OR

IEN

TATI

ON ORIENTATION CHANGE

gives Broken Hill newprospects

George Gibson projectmanager of the Broken Hill

Exploration Initiative offers acouple of new ideas to those

looking for further world-classore bodies in Australiarsquos

Curnamona province

Figure 1Shallow-dippingD2 structuresoverprinted bymore uprightD3 folds

AUSGEO News 57 Apri l 2000 3


lsquoSome of the mineralisation at Broken Hill is shear controlledalthough whether the line of lode is similarly shear-hosted remainsuncertainrsquo he says

lsquoMany of the zinc anomalies for example seem to fall on the trail ofstructures with the same north-east trend as the D3 structuresrsquo

Shear-hosted copperndashgold mineralisation occurs at Copper Blow southof Broken Hill and silver lead and zinc in the Allendale region to thenorth

lsquoAnd if we take this one step further and argue that the line of lodefor Broken Hill is structurally controlledmdashbecause in the open pits we seea lot of shearing in the line of lodemdashwhere could we look forcontinuation of line of lodersquo Dr Gibson asks

He suggests searching on the other side of the Stephens Creek shearzone because this region is underlain by a synformal structure cored bygranitic gneiss very similar to that observed in the Broken Hill synform

lsquoSo if the rationale holds namely that the line of lode sits along thewestern margin of a synform cored by granitic gneiss then this is wherewe should start searchingrsquo he says

In regard to aeromagnetics Dr Gibson says that it cannot be assumedthat they are all stratiform

lsquoSome are stratiform and some sit within melt rocks (pegmatites) Alarge number however are structurally controlled particularly the morelinear north-east trending anomaliesrsquo

He adds that a lot of the linear magnetic anomalies displayed by theaeromagnetics sit in the D3 fabrics and a few lie in D2 high-strain zones

The BHEI started up in 1994 in response to industry predictions thatthe Broken Hill ore deposit would be exhausted within 12 years Miningcompany Pasminco shuts its last major mine in Broken Hill in 2006Economic prosperity for Broken Hill looks grim unless governmentagencies such as AGSO alert mineral exploration companies to otherpossibilities in the region

The BHEI is a CommonwealthndashState government venture involvingAGSO the New South Wales Department of Mineral Resources and SouthAustraliarsquos Department of Primary Industries and Resources

For more detailsphone GeorgeGibson on +61 2 6249 9727or e-mailgeorgegibsonagsogovau

4 Apri l 2000 AUSGEO News 57

Figure 2 Simplifiedgeological map of theBroken Hill regionshowing BHEI seismiclines (Modified fromNSW Department ofMineral Resources 1100 000 map)

ORIENTATIONM I N E R A L S O P E N D A Y S

Take a thousand kilometres ofreflection data add refraction andgravity data and you probably have$3 million worth of data aboutAustralian mineral provincesgathered by the AustralianGeodynamics Cooperative ResearchCentre (AGCRC) over the last sevenyears The AGCRC ceases operationthis year but not before it demon-strates its province and continental-scale syntheses at a couple ofworkshops

lsquoWe have been trying to get abetter understanding of the crustalgeometry in some mineralprovinces and in the long termlook at potential plumbing systemson a regional scalersquo says RussellKorsch AGCRC ResearchCoordinator

Seismic resul tsAGCRC work focuses on mineralprovinces around Australiaspecifically the Yilgarn Craton MtIsa Inlier Broken Hill westernVictoria and the eastern part of theLachlan Orogen

YilgarnIn the Yilgarn Craton the AGCRChas done some geodynamicmodelling of the Kalgoorlie areaData is being compiled from threeseismic surveys (1991 1997 and1999) The survey in September lastyear focused on the highly mineral-ised Bardoc Shear It was carriedout as a grid of five lines to build athree-dimensional picture of thecrust in the Kalgoorlie area Data isstill being interpreted but it appearsthe greenstones have a thrustndashstackgeometry and the Moho occurs at adepth of 35 kilometres The first-pass interpretation of data will bepresented at a workshop inKalgoorlie on May 2ndash3

Mt IsaDeep seismic reflection datarefraction data and geologicalmapping along a seismic transectwere used to produce a crustal-scaled depth section of the Mt IsaInlier For the refraction survey six

crustal geometrysubject of majorseismic research

MINERAL PROVINCES




explosions were let off in one daymdashthreetonnes at either end of the transect andfour single-tonne blasts in the centre

lsquoYou need that sort of oomph to putenough energy into the ground for the p-waves to travel 500 kilometres to wherewe were recording datarsquo says Dr Korsch

The crust is very thick in Mt Isa It isabout 55 kilometres compared with 35kilometres in the Yilgarn There are twohigh-velocity lens-shaped bodies in thelower and middle crust that are mafic toultramafic in composition The Mt IsaFault is part of a group of west-dippingfaults One of these the Adelheid Faultis a highly reflective zone in the seismic data

Broken Hil lThe main aim of AGCRC work in theBroken Hill area was to look at theTasman Line in western New SouthWales The Tasman Line is defined asthe boundary between surface outcropsof Proterozoic and Palaeozoic rocks inAustralia When the Tasman Line wasdefined there were no knownProterozoic or Archaean rocks on thesurface east of it

In 1997 a 350-kilometre north-westto south-east refraction line was shotacross the Broken Hill block (see figure1) Again six shots were fired in a single day

Figure 2 Data from a seismic reflectiontransect across the boundary of the Lachlanand Delamerian Orogens shows east-dipping (west-directed) thrust faultsdominate the Delamerian

Figure 1 A 350-kilometre north-west tosouth-east refraction line shot across theBroken Hill block The six shots were firedin a single day

lsquoIt is effectively a very simple crustal structure in the Broken Hillareamdasha two-layered crustrsquo says Dr Korsch

lsquoThe Moho is about 35 kilometres on the east and west and dipsdown to roughly 43 kilometres under Broken Hillrsquo

The lower crust maintains a constant thickness of about 14kilometres There is no evidence of a mid-crustal body that might havesourced mafic dykes and no evidence of an underplated lower crustallayer

lsquoThe Tasman Line as defined on the surface is marked by the DarlingRiver lineamentrsquo says Dr Korsch

lsquoBut the real boundary between the Tasman Line or between theBroken Hill block and the rocks in the east shows up in the seismic as achange from east-dipping structures to a series of west-dippingstructuresrsquo he says

Western VictoriaA seismic reflection transect across the boundary of the Lachlan andDelamerian Orogens was part of a study into geodynamic factorscontrolling gold mineralisation in western Victoria

The orogens are divided by the east-dipping Moyston and PleasantCreek faults East-dipping (west-directed) thrust faults dominate theDelamerian while the Lachlan Orogen is dominated by a west-dippingfabric (see figure 2) The Escondida Fault is overlain by the youngerpost-Ordovician Grampians Group

Eastern LachlanThe initial work in 1997 was done in the area between Canberra andDubbo in New South Wales It comprised a 350-kilometre north-southrefraction survey along the Molong volcanic belt As well in 1997 and1999 a total of 290 kilometres of reflection data were acquired in theOrange and Forbes-West Wyalong districts

The main aim of the refraction survey was to look at the differencebetween the Ordovician turbidites and Ordovician volcanics Again sixshots were fired and the blasts produced a lsquonoticeable wigglersquo on theseismometer in the AGSO building

lsquoThe crustal geometry under the Lachlan Transfer Zone continuingnorth through Ordovician volcanics is quite different to the southernpartrsquo says Dr Korsch

lsquoThe Moho goes from a thickness of about 46 kilometres in the southand gradually thins to about 40 kilometres in the northrsquo he says

Ordovician volcanics underlie the Hill End and Cowra troughs thatflank the Molong volcanic belt East-dipping faults cut the Molongvolcanic belt

A summary of results from last yearrsquos seismic work that was lookingat an igneous complex near Lake Cowal in the eastern Lachlan Orogenwill be presented towards the end of the year at a workshop in Orange

Geological informat ion systemData gathered by the AGCRC is held in PREDICT It is a geologicalinformation system accessed by a single web interface Through Netscapeusers can interrogate templates or a series of events tables to comparetectonostratigraphic histories

lsquoWersquove also developed a petroleum information management systemwith tables that look at plays organic-rich rocks or source rocksreservoirs seals traps and the maturation and migration of thehydrocarbonsrsquo says Dr Korsch

lsquoEventually based on the petroleum system we hope to develop aminerals information system and a predictive system for mineralsrsquo

Research groupThe AGCRC is an unincorporated venture involving AGSO CSIROExploration and Mining the universities of La Trobe Melbourne andMonash and Compaq Computers

For further information phone Russell Korsch on +61 6249 9495 ore-mail russellkorschagsogovau



The Australian Geodynamics CRC will be hosting a two-day workshop on the2ndash3 May 2000 to coincide with the early release of seismic reflection datafrom the AGCRCrsquos 1999 Yilgarn seismic survey

Researchers will present the results to date of the seismic reflectiontraverses and three-dimensional fluid flow modelling The workshop will bean opportunity to discuss implications of this research with the earth sciencescommunity and get feedback from interested parties Researchers from AGSOCSIRO and the Geological Survey of Western Australia will givepresentations

Seismic surveyThe seismic project involved the collection of a grid of deep seismic reflectiondata within the Kalgoorlie terrane Eastern Goldfields Complementary gravitydata was also collected along each of the traverses

The five new seismic traverses are providing new information on the three-dimensional geometry of the Eastern Goldfields The first results from theseismic data indicate there are significant variations in structure within theregion

Fluid f low model l ingThe numerical modelling project has produced further models of theKalgoorlie region based on the deep seismic data These address the potentialfor lateral fluid flow and fluid mixing proposed in recent studies and theinfluence of thermal structure on fluid production and migration

Yilgarnresults focusof upcomingseismicworkshop2ndash3 May 2000WMC ConferenceCentre Kalgoor l ie

For more details phone Lindsay Saker on +61 2 6249 9766 or e-mail lindsaysakeragsogovau

Think of the Yilgarn and you think of goldmdashKalgoorlie gold There is much more to theYilgarn than Kalgoorlie however and a push ison to find large resources of the precious metalelsewhere in the craton

Since 1990 AGSO and the Geological Surveyof Western Australia have carried out a majorgeoscientific program in the Eastern GoldfieldsProvince (see figure 1) This work involvedmapping results of geology geochemical andisotopic studies carrying out seismic reflectionsurveys and interpreting the newly acquiredgeophysical data

Ongoing complementary regional studies ofgeophysical and geochemical data put NGMAproject work in a craton-wide context andprovide insights for exploration opportunity

Of the forty-two 1100 000 sheets mapped inthe northern Eastern Goldfields AGSO wasintimately involved in 26

The Eastern Goldfields National GeologicalMapping Accord (NGMA) Project winds upthis year Project manager Alan Whitakeroffers a snapshot of what geologists foundin this mineral-rich province of theArchaean Yilgarn Craton

YILGARN MAPPINGprovides golden opportunity

Figure 1 Eastern Goldfields NGMA project area





Workshop focusThe workshop content includes thefollowing

bull regional geology and structure ofthe region

bull timing of deformation eventsbull a crustal cross-section for each

traversebull near-surface structure for each

traversebull seismic signature of key

structures including shear zonesdetachment surfaces and domes

bull geometry of granitesbull weathering profilesbull implications for regional

tectonics andbull thoughts on mineralisation and

fluid pathways within the crust

FeesRegistration costs $135 (students $45) The price includes a copy of workshop proceedingslunch and morning and afternoon tea

lsquoOut of that work we believethere was early extension anddoming of granitoids bringing high-grade greenstones up largely inconcordant contact with the granitedomesrsquo says Mr Whitaker

lsquoWe also believe thatdeformational sequence in thenorthern Eastern Goldfields is thesame as that in the southern partand should have similar goldexploration potentialrsquo he says

Mr Whitaker says that studies inthe Leonora area indicate that earlyD1 structures were mineralised withgold Therefore there was an earlygold event which is contrary to thebelief that gold mineralisation onlyoccurred in a single event late inthe structural history at about 2630million years ago

Geophys ical data Fourteen 1250 000 sheets of gravitywere acquired over the EasternGoldfields generally at four-kilometre spacing with some two-kilometre spacing over some of thegreenstones Aeromagnetic data at400-metre flight line spacing wasacquired over a dozen 1250 000sheets in and adjacent to theprovince with more being addedthis year (see Stanley Youanmi andRobert in product news this issue)

These data show that thecraton is generally composed of

granitoid (80) Two main types of structures dislocate the geology brittle-ductile shears that are strike extensive (+80 km) and define structuralcorridors five to 10 kilometres wide and shorter (generally lt40 km) narrowbrittle overprinting faults and fractures that caused only minor dislocations

Five geophysical rock units are inferred undivided gneiss-migmatite-granite sinuous gneiss parallell-banded gneiss greenstone and discretegranite plutons The greenstones of the Eastern Goldfields are quitedislocated and disrupted relative to greenstone in provinces farther westGranite plutons are far more abundant in the greenstone belts of theEastern Goldfields than in the extensive regions of granitoid between thebelts Many of the plutons are spatially associated forming intrusivecorridors Parallel-banded gneiss is found along the margins of the gneiss-migmatite-granite domains and commonly includes small enclaves ofhighly metamorphosed greenstone

Seismic workRoughly 200 kilometres of east-west seismic reflection data were acquiredin the Kalgoorlie region Interpretation of the seismic data shows thegreenstone belts are four to seven kilometres thick and that the crustalthickness under western granitoids is roughly 33 kilometres Under thegreenstones the crust thickens to about 38 kilometres A detachment zoneis inferred at the base of the greenstones

lsquoOne of the major things to come out of the seismic work was thediscovery of major deep crust penetrating faults or shearsrsquo says Mr Whitaker

lsquoThese structures possibly provided the plumbing for mineralisingfluidsrsquo he says

Granite geochemistryThere are five main granite types in the northern Eastern Goldfields Twotypes dominate Intrusion occurred from more than 2720 to less than 2630million years ago but the major reworking of the crust was between 2675and 2640 Almost all dated granites are of similar age or younger than thegreenstones The implication from their geochemistry is that the granitesdeveloped from pre-existing felsic crust They are not melts of thegreenstone belts

Granite-related gold is dominantly associated with two of the fivegranite typesmdashthat is mafic granites and syenitesmdasheven thoughmineralisation appears to post-date intrusion of these granite types

In terms of gold exploration opportunities there are several locatedaway from traditional mining centres

In the north of the craton greenstone is inferred under thinBangemall Basin cover adjacent to outcropping Archaean (interpreted)granite on the Nabberu and Stanley sheets

Mr Whitaker says that having seen some of the aeromagnetic data in thesouth-east of the craton and interpreted the Rason-Throssell data to thenorth he believes there is another 30 to 50 kilometres of craton east fromthat area of subcrop at readily explorable depths (generally lt50 m cover)

lsquoTherersquos also potential for gneiss-hosted gold for example in thenorthern Southern Cross Province where a major shear system runs north-north-west and cuts sinuous gneissrsquo he says

For more details phone Alan Whitaker on +61 2 6249 9702 or e-mailalanwhitakeragsogovau

Correction This figure shouldhave appeared on page 13 of theFebruary issue in the article lsquoSignsof oil and gas off Lord Howersquo It isa map of a large part of theFairway Basin showing thedistribution of the largest lsquosaltrsquodomes and ridges and of thelsquobottom simulating reflectorrsquorepresenting gas hydrates inrelation to water depths




If Alice Murray leader ofAGSOrsquos National GravimetryProject has her way gravity

will not be auxiliary togeological interpretations but

used systematically in projectsfrom the start

lsquoGravity is not something yougrab like a map to verify yourprevious interpretationsrsquo says

Ms Murray

lsquoIt is a precision tool that withproper planning offers much

more than background regionalinformationrsquo

Project funct ionsThe National Gravimetry Project maintains the National Gravity DatabaseFundamental Gravity Network and national gravity standards

The National Gravity Database contains data from more than 900thousand point gravity observations derived from over a thousand surveysdating back to 1937 Currently the database is being translated from an in-house system to an Oracle-based one Gravity will be integrated into AGSOrsquoscorporate database and into the multi-disciplinary geophysical processingsystems

The Fundamental Gravity Network comprises roughly a thousandmarked and documented gravity reference points at 300 localities aroundAustralia Systematically over the years companies and the State Surveyshave been basing their surveys on these AGSO reference stations

lsquoThat means we have a consistent continent-wide coverage without theproblem that arose in the airborne surveys where wersquove got a mismatchbetween individual surveys and we had to micro-levelrsquo says Ms Murray

Providing national standards for gravity is a very important function MsMurray says because gravity is an expensive tool if it is usedindiscriminately

lsquoIt costs roughly $60 a station for pure land work and $100 a station forhelicopter work so for a quarter million sheet at about four-kilometrespacing yoursquore talking about $1050rsquo says Ms Murray

lsquoYou really canrsquot afford blanket coverage of the whole continentrsquo

GRAVITY properlyplanned is a PRECISION TOOL

Continued page 14

Figure 1 Location ofAustraliarsquos Fundamental

Gravity Networkstations



SURGESBLACKOUTS

glowing skiesas Sun activity peaks

unspots are areas on the Sunrsquos surface that arecooler and so darker than their surroundingsThey are areas of complex contortions of theSunrsquos magnetic field and are a good indicator theactivity of the Sun as a whole

The Sun exhibits an 11-year cycle of activity(approximately) the last maximum of which(Cycle 22) occurred in 1989 The chart below

shows the sunspot numbers since 1986 the beginning of Cycle 22 Thecurrent cycle (number 23) began in 1996 when activity was at aminimum once again

Coincident with the occurrence of numerous sunspots is theincreased likelihood of solar flares These are observed as a suddenbrightening within an active region on the Sunrsquos surface They lastroughly up to an hour During this time high energy electromagneticradiation and particles are ejected from the Sun If directed towards theEarth they can result in disturbances to the ionosphere and thegeomagnetic field causing a number of unusual and hazardous effects

Coronal holesSolar activity builds up to a maximum much more quickly than thedecline afterwards (see the chart) In the declining phase there is anincreased frequency and longevity of coronal holes These regions inthe solar corona are of relatively low density and low temperature andare sources of high-energy enhancements to the solar wind (Theidentity of coronal holes was discovered by Skylab Prior to their properidentification they were called M-regions)

A coronal hole can persist for as long as 18 months Ionosphericand magnetic disturbances on Earth caused by a coronal hole tend torepeat every 27 daysmdashthe apparent rotation period of the Sun

DisturbancesThe combined effect of solar flares andcoronal holes brings about a peak inoccurrence of ionospheric andgeomagnetic disturbances some timeafter the sunspot maximum andgenerally before sunspot minimum

If the predictions for Solar Cycle 23eventuate expect a relatively highsunspot number at solar maximum ashas been the case for the two mostrecent cycles

During strong disturbances orstorms the radiation that bombards theEarth will cause changes in theionosphere These changes will affectradio communication paths resulting infreak propagation conditions Largeelectric currents will flow in theionosphere creating a rapidly changingmagnetic field that will induce largecurrents in long conductors such aspipelines and power lines This willbring about accelerated corrosion of theformer and surges in the latter that canresult in damage to transformers andblackouts

During the most active phases ofmagnetic storms expect to see auroras(or the southern and northern lights)much further towards the equator thanusual Displays may be visible from NewSouth Wales (and further south) usuallyas a diffuse deep red glow low in thesouthern night sky

Satellites are particularly exposedand vulnerable to the hazards thataccompany solar activity Chargedparticles can cause a build-up of electricpotential on these craft resulting indamage to sensitive electronicinstruments Atmospheric heating resultsin increased satellite drag and thedegradation of their orbits Highlyenergetic charged particles due to solaractivity pose a serious hazard toastronauts

AGSOrsquos Geomagnetism Sectioncontinuously monitors the geomagneticfield at observatories in Australia andAustralian Antarctic Territory In collab-oration with the IPS it produces indicesof geomagnetic and ionosphericdisturbance that are used to assist in themitigation of any adverse effects of highsolar activity

For further information telephonePeter Hopgood on +61 2 6249 9359or e-mail peterhopgoodagsogovau

The Sunrsquos activity measured by the average number ofsunspots is expected to peak this year based on projections by

the Ionospheric Prediction Service (IPS) Department ofIndustry Science and Resources

0

50

100

150

200

1986 2006

Sunspot Number Solar Cycles 22 and 23

1988 1990 1992 1994 1996 1998 2000 2002 2004

ObservedYearly SmoothedPredicted Smoothed

SS

Top left The Sun observed in He II 304 nm light at 0719 on February 22 2000Flare activity is seen at the limb on the left of the picture The bright areas orplages indicate active regions out of which flares are born Photo courtesy of Solaramp Helioscopic Observatory


SPEAKERS

Top left Ninety-nine Mountains(translated) with vegetation peeled backdue to the September 21 1999 earthquakein central Taiwan Photo Songfa Liu

Top right A public school not far from thesmall town of Chi Chi very close to theepicentre of the September 21 1999earthquake Photo Songfa Liu

What a home coming formarine geoscientist and

seismologist Dr Chao-ShingLee Just three hours after his

return to Taiwan from workwith AGSO in September 1999

an earthquake magnitude of73 on the Richter scale sent

shock waves through hishomeland The big earthquake

ruptured much of Taiwandestroyed some 20 thousand

buildings and killed anestimated 2500 people


Since that fateful day Taiwanrsquos government and National Science Councilare channelling what will amount to approximately A$200 million towardscommunity awareness and scientific research such as deep crustal and rockchemistry studies airborne surveys and determining the history of Taiwanrsquosearthquakesmdashtheir frequency locations and extent of lsquogeohazardrsquo

lsquoWe need at least several thousand years of earthquake history not just arecord of the last 100 yearsrsquo Dr Lee says

lsquoTaiwan sits in a very active area but until the big one the devastatedregion had been quiet for a long time

lsquoNow is the perfect case (sic) for studying the so-called seismic gaprsquo he says

Earthquake his toryTaiwanrsquos paleohistory will be reconstructed by collecting sediment samplesfrom drill holes along active faults It is hoped data gathered offers insightsinto earthquake cycles and seismic gaps In addition seismometers as well asstrain groundwater and GPS detectors will be permanently buried instrategic places along known faults to monitor current activity

Taiwanrsquos geology shows a number of faults Those in the centre andsouth are thrust-type faults while those further north tend to be strike andextensional During the September 1999 earthquake a 100-kilometre longreverse thrust-type fault caused large ruptures that raised the ground by upto five metres

Dr Lee says that after this earthquake a lush mountainous area looked asif someone had peeled off the skin As well due to the earthquake amountain moved one river became a permanent dam and another that hadan even unremarkable flow now has a five-metre waterfall

lsquoNow we really have a lot of work to dorsquo he says lsquoOur surveying people have to re-measure because Taiwan has changed

the land has been extended in some areas and shortened in others becauseof the earthquakersquo

Most buildings near the fault line fell down particularly any built onunconsolidated conglomerates and liquefied sandy soils But Dr Lee tells ofone lucky resident

Before the earthquake the residentrsquos two-storey house was on a levelroad Now the house stands about four metres above what remains of theroad The neighboursrsquo homes are gone The house was designed to be five

BIG EARTHQUA


subducts underneath the Philippines platelsquoOur region is becoming very hot because there could be more than 100

submarine volcanoesrsquo says Dr Lee lsquoThat is why the French and Japanese arevery interested in studying the arearsquo

In May Dr Lee will be a guest on board a Japanese submarine thatsurveys the lsquosearsquos mountainsrsquo

But in the meantime Dr Leersquos geology students in Taiwan have askedhim to send them an e-mail before he leaves Australia this timemdashjust in case

Dr Chao-Shing Lee works for the Institute of Applied GeophysicsNational Taiwan Ocean University He presented this information as a guestspeaker at AGSO in February

S P E A K E R S

storeys high to accommodate a sonand his soon-to-be wife But theson changed his mind aboutmarriage and a two-storey homewas built on foundations designedfor a much higher building

lsquoThis may be the way for ourfuture building code particularlynear any active faultrsquo says Dr Lee

Mountain bui ld ingTaiwanrsquos crustal movement is abouteight centimetres per year in thesouth and gradually reduces to thenorth For a small area there is adifference of roughly 11 thousandmetres from the highest mountainin the centre of Taiwan to a deep-sea trench There are a number ofsedimentary basins from Taiwan tothe Chinese coast As well Dr Leeclaims there are about 68submarine volcanoes in the areathat scientists know of to date

Dr Lee says that throughoceanic crust subduction and thenthrust Taiwanrsquos mountains arebeing formed beginning from thesouth He believes that evidence ofsubsidence lies in the very lownorthern part of Taiwan and ingravity data that show there aresubmarine canyons offshore

He believes the Philippinesplate subducts to the northunderneath the Eurasian plate andthat part of the Eurasian plate

Location map of Taiwanshowing basins

and ridges From thehighest mountain in the

centre of Taiwan to the sea trenches is

roughly 11 000 km

rousesTaiwan


UAKE


Top Rabaulrsquos naturalharbour caused by a calderacollapse In the backgroundis Tavurvur and part ofRabaul destroyed by the1994 eruption

Middle Ash loading fromTavurvurrsquos 1994 eruptiondestroys buildings roads andvegetation

Bottom The landscape leftlifeless and monochromaticfrom Tavurvurrsquos ash

Few would know New Britainrsquos volcanoes like AGSOrsquos Dr WallyJohnson and none could be more passionate about themparticularly about those that destroyed the town of Rabaul in 1994With more than 30 yearsrsquo experience researching this volatile areain Papua New Guinea Dr Johnson gave a glimpse of the attractionfor him and other volcanologists at a recent AGSO lecture

610 am September 19 1994 Rabaul New Britain Tavurvur erupts Onehour and 10 minutes later Vulcan on the opposite side of the harbourspews rock and ash high into the air The simultaneous eruption of twovolcanoes on the island of New Britain in the eastern end of the Bismarckvolcanic arc is a repeat of events of 1937 and 1878

Rabaul once a tropical paradise is devastated Most damage happenedin the first 24 hours Roofs collapsed with ash loading roads were blockedpower and communication lines came down and all vegetation disappearedThe damage bill reached $300 million Australian (1994 values) There werefour deaths

Tavurvurrsquos eruption was wet Dark ash (and accretionary lapilli) wasdriven over the town by the strong south-east trade winds at that time ofyear If the eruption had taken place during the north-west monsoon seasonthe town would have remained intact

Vulcan was a drier eruption It belched pumice and ash and produced aplinian plume that rose more than 20 kilometres During its ascent the plumecaught winds of different speed and directions that spread it wide over theBismarck Sea Part of the cloud turned south over mainland PNG and theneast and into Fijian airspace It comprised mainly ice crystals but also smallparticles of ash Only small amounts of sulphur dioxide and sulphuric acidaerosols were in the cloud

Expert i se enl i s tedThe eruptions showed there was a dire need for a much betterunderstanding of the deep interior of Rabaul volcano and of how the magmasystem lsquoworksrsquo there Monitoring also needed to be stepped up at other high-risk volcanoes in PNG

Australiarsquos aid agency AusAID has invested A$65 million instrengthening the PNG volcanological service AGSO managed that projectwhich is drawing to a close after three and a half years Much has beenlearned but a lot is still unknown because of the complexity of activityaround Rabaul

Structural understanding PNG and the western part of the Solomon Islands is an area of great currenttectonic activity It is quite unique because of its complexity There may beas many as four minor plates sandwiched between the Indo-Australian andPacific plates with the Solomon plate being subducted beneath the SouthBismarck plate at about 70 degrees Volcanoes are associated with most ofthe plate boundaries The main volcanological feature in PNG is theBismarck volcanic arc (about 1000 km long) Rabaul on the island of NewBritain sits at the north eastern end of the arc

A diverse range of magma compositions is found throughout the NewBritain area The magmas differ in composition depending on the positionof the volcanoes above the dipping slab of Solomon Sea plate underlying


RABAUL VOLCANOESfire 30-year passion

S P E A K E R S


before a basalt injection causes a further eruption Basalt injections seem tobe a common eruptive mechanism at Rabaul and may explain the origin ofthe many large volume (10 km3 or greater) eruptions there including thelarge ignimbrite deposit Interestingly recent argon-argon results suggest thatthere may have been more large-scale eruptions at Rabaul in the last 20thousand years than in earlier times

The third component is the largely submarine Tavui caldera some 10kilometres wide and more than a kilometre deep The Raluan pyroclasticsformed as recently as 7000 years ago may have originated from Tavui

Magma reservoir beneath RabaulCurrent ideas point to there being two separate mantle sources beneath theRabaul areamdashone that feeds the Tavui volcano and another for the WatomTurangunan (WT) zone and Rabaul caldera

Preliminary seismic tomography results indicate there is a low velocityanomaly that underlies the seismic annulus in the Rabaul area A similarbody has not been found beneath Tavui to date but the tomography surveywas designed for a depth of only 10ndash12 kilometres

The roof of the reservoir beneath Rabaul caldera is about three or fourkilometres deep The velocities involved show that this body could not be100 per cent magma but most likely is a mixture of solid and magmaticmaterial The WT magmas are injected into this main magma reservoirbeneath Rabaul and the mixed magmas come up the ring fault and formvolcanoes such as Tavurvur

The basalt magma injection at the intracaldera volcanoes in the east attimes could have been sufficiently robust to reactivate the whole of thedactic magma reservoir Proper monitoring therefore must be continued atRabaul to avoid devastating consequences for the population of the Rabaul area

Present dayRabaul is not a place for people Civilisation exists there only by geologicalconsent After the 1994 eruptions the PNG government moved residents toKokopo a safer place than Rabaul because it is outside the active calderaKokopo however is still an area with geological hazards

The volcanoes of PNG have caused hundreds of fatalities over the last150 years The vulnerability of communities is increasing because of agrowing population and increased investment particularly in coastal areasResponsibility for hazard and risk management now rests with the PNGgovernment and its scientists But AusAID is currently considering how itsinvestment can be sustainedmdashparticularly how to continue the vital work ofthe Rabaul Volcanological Observatory

Dr Johnson is the Chief of AGSOrsquos Geohazards and GeomagnetismDivision He was presented with the Harold Raggatt Award for thislecture the first of the AGSO Distinguished Lecture series for this yearIn forty-five minutes he presented only a small aspect of 30 yearsrsquoresearch For further information telephone Dr Johnson after April onhis return from PNG on +61 2 6249 9377 or e-mailwallyjohnsonagsogovau

Map showing the location of Rabaulits volcanoes and the W-T zone


New Britain At the volcanic front(over where the dipping SolomonSea plate is quite shallow) themagmas have high uranium tothorium ratios and extremedepletions in tantalum niobiumand rare earths The uraniumenrichment event is quite oldmdashatleast 100 thousand years

The rocks at the volcanic frontalso show an abundance ofberyllium 10 and boron Both areeffective tracers of sedimentrecycling and neither has beenfractionated from one anotherduring fractional crystallisation orpartial melting Beryllium 10 has ahalf-life of about 15 million yearsmdashjust long enough for the berylliumto form be absorbed by sedimentstaken down into the subductionzone and erupted It is thought thatthe cause of the high beryllium is aseparate process from that of theuranium enrichment

Ring s tructures atRabaulRabaul volcano is only one ofseveral young calderas in the NewBritain area It had an unusualseismic annulus up until the 1994eruption identified as a result ofmany years of earthquakemonitoring Cross-sectionaldiagrams show that the earthquakescut off at a depth of about fourkilometres possibly representingthe top of the main magmareservoir around Rabaul There hasbeen a series of caldera collapseevents at Rabaul and sometime inthe not-too-distant past the calderasystem was breached by the seaand formed a natural harbour

Three different volcanic systemscan be identified in the Rabaularea The first is the series oflsquonestedrsquo calderas making up Rabaulvolcano itself and enclosing eightsmaller volcanoes most of themwithin one kilometre of the seismicannulus The magmas of thesevolcanoesmdashincluding Tavurvur andVulcanmdashare thought to comedirectly up to the surface from ringdykes

The second volcanic system ismade up of a line of strato-volcanoes extending from WatomIsland in the north-west toTuranguna (South Daughter) in thesouth-east making up the lsquoWatom-Turanguna zonersquo

Many of the magmas of Rabaulare mixed magmas They representmixing of different magma batchesand the retention of magmas forsubstantial periods in reservoirs

S P E A K E R S


Ms Murray says that forethought into which areas warrant gravitycoverage or additional coverage is important She says those planning asurvey should be clear about the results and benefits they want before theystart planning and suggests keeping these questions in mind

bull Why do we want to do the surveybull Is it economic or scientificbull For what are we lookingmdashwhat is the shape size and density of the

geological bodybull What is the prevailing trend direction in the areabull What coverage do we already havebull Can it be supplemented by doing in-fill in particular restricted areasbull Do we want uniform coverage or can we define smaller areas of more

detailed coveragebull How much money can we spend (That determines the number of

stations and how much detail can be added)

Another part of the standards is ensuring that all work is based on thefundamental network and all surveys have been properly levelled together

lsquoOtherwise if you pass a filter over the whole country yoursquoll end up withlines all over the place that are caused by differences in datum rather thangeological featuresrsquo she says

Scient i f ic survey planningMs Murray says that you can get much more than is initially obvious out offor example a four-kilometre gravity dataset (depending on the orientationof the things you are looking for)

lsquoIf you are looking for dykes and lineaments if you incline your surveygrid at a low angle to the strike you can get more definition in the directionyou want than the four-kilometre spacings would implyrsquo she says

lsquoIf you do it at 45 degrees to the strike you are going to get a resolutionof 25 kilometres and you can pull that down to less than one by doing it ata fine anglersquo

However Ms Murray warns that by going too fine the body you arelooking for can be missed altogether

Ms Murray says the project has been quite successful in the southerngoldfields of Western Australia because they were targeting on the basis ofknown geology She says it was the first gravity survey she has seen thatshowed such an extensive series of dykes (The coverage for three sheetswas four kilometres and in the greenstone areas the coverage was twokilometres)



lsquoWe are beginning to gain a lotmore geological knowledge bydoing a survey in a plannedscientific wayrsquo she says

Project futureIn the past the project was verybusy reacting to loads of datacoming in Nowadays they areconcentrating on national standardsand information exchange MsMurray says they plan to increasethe accuracy of the base networkand increase the speed at whichstations are established They arealso looking into optimal griddingof the continent and hope toproduce a composite grid that is200 metres over the whole ofAustralia Isostatic and terraincorrections will be applied Withinthe decade they hope to useairborne gradiometry to solvegeological problems

lsquoIn the past wersquove very muchbeen the data-gathering project justproducing postage stamp maps anddoing routine processingrsquo says Ms Murray

lsquoBut we want to work moreclosely with geological projects andbe an advisory centre because wehave the expertise that can solvequite a few problemsrsquo

For more details phone AliceMurray on +61 2 6249 9264 or e-mail alicemurrayagsogovau

Figure 2 Gravity can pickup very fine details (even ingreyscale) This is amicrogravity grid of theBroken Hill area The areabeing mined is easilydistinguished

Continued from page 8


Nowadays the governmentgrapples with a lsquotriple bottomlinersquomdashthe community expects abalance between economicenvironmental and social valuesTransparent and well-informedland-use decisions are demanded

Driven by the requirements ofgovernment policy areas andindustry needs AGSOrsquos role insupplying advice on Australiarsquosmineral resources has expanded toinclude issues concerning resourceaccess and land management AGSOis being asked to provide scientificinput to facilitate complex decisionson high profile (and often emotive)issues such as land use in areaswith conservation significance andland degradationmdashparticularlysalinity

lsquoWhile many land-use decisionsreside formally with the Statesrsquo saysIan Lambert Group Manager ofAGSOrsquos Resources and Adviceactivities lsquothe Commonwealth isgenerally involved where there aredecisions to be made on nationallysignificant issuesrsquo

Transparent and informed land-use decisions require integration ofgeoscientific information with otherdata It is here that AGSO with itsgeoscience and technical expertiseis playing an important role oftenworking with the States and otherinterested parties

lsquoWe use advanced GIS-baseddecision support systems (DSS) thatare very effective in guidingdecisions on land use and relatedissuesrsquo says Dr Lambert

Data such as mineral depositsgeology regolith propertiesearthquake risk wildernessendangered species forest valuesland tenure and agricultural landuse can be readily shown todecision makers and manipulatedin real time



Mineral resources and advice activitiesAGSOrsquos role extendedMuch less than one per cent of Australia is devoted to miningactivities yet from that small area the returns have been very highOnce that was a significant argument for allowing mining to takeplace almost anywhere

Dr Lambert notes that there are extensive prospective areas with nocurrently known mineral deposits He says that lack of known resources in aregion does not necessarily equate with lsquono potentialrsquo for future discoveriesof concealed mineral deposits and so this needs to be factored into land-useplanning

lsquoThe rationale is that while we cannot have a perfect picture at anygiven time we do the best we can based on existing data because decisionswill be made anywayrsquo says Dr Lambert

Figure 1 In the Regional Forest Agreement process AGSO has been preparing mineralpotential maps This is the weighted composite mineral potential map for Australiarsquossouthernndashmost state Tasmania


lsquoAnd they can be made in ignorance if we donrsquot factor in all of therelevant data that we haversquo he says

Dr Lambert says that information on known and potential mineralresources was important input for many land-use decisions AGSOrsquosparticipation in the CommonwealthndashState Regional Forest Agreement (RFA)process had established this

Regional Forest AgreementIn the RFA process AGSO has been preparing lsquomineral potential mapsrsquo forindividual styles of mineral deposits A weighting is done by a panel ofexperts who know the geology of the areas concerned as well as the relativeeconomic significance of the different types of deposits For example amassive sulphide style deposit in volcanics might be weighted nine out of 10whereas tin veins may score four These results are collated and displayed asmaps of various types (see figure 1) They are held in a GIS system thatenables them to be overlaid with other values in considering options forconservation reserves

Chris tmas Is landAnother important application of such decision support systems is illustratedby AGSOrsquos work on Christmas Island an Australian Indian Ocean territorywith a long history of phosphate mining (see figure 2) The island presenteda dilemma when the Commonwealth Government-owned mining operationceased in 1987 Mining re-commenced in 1990 following an employee buy-out of the Commonwealthrsquos operation A 21-year mining lease was grantedby the government in 1997 Mining mainly comes from the discardedstockpiles of the upper layers of phosphate that are valuable as direct-application phosphate in several Asian markets



lsquoPrior to granting this lease weassessed the remaining phosphateresources the viability of futuremining developed the miningschedule advised the governmenton royalty options recovered a lotof old hard-copy data and put allthe relevant data into a geographicinformation systemrsquo says DrLambert

With the GIS and orthophotosof the whole island and at a costof $200 000 instead of around $5 million for a traditional survey300 stockpiles were accuratelylocated In the phosphate-richenvironment many stockpiles hadbecome overgrown by densevegetation and were very oftenhard to recognise on the ground

Another problem on the islandwhere the GIS has helped concernsthe plight of the Abbotts booby anendangered seabird The GIS helpsprioritise areas for rehabilitationThese areas minimise the windturbulence that is causing thebooby chicks to plummet to the

Figure 2 Map of Christmas Island showing the national park and mining leases




A discussionof massattraction

discuss ion meet ing3ndash4 May 2000

Organised by AGSO the AustralianNational University and CSIROExploration amp Mining this meetingis for those who undertakeinvestigations in palaeomagnetismrock magnetism or environmentalmagnetism use or might use theresults of investigations or requirelaboratory and scientific services inthese areas It is a particularlyimportant meeting given theuncertain future of the majorlaboratory facilities providedtraditionally by CSIRO and AGSO

Those who have an interest inthe area or wish to learn about thecapabilities of methods used wouldalso find this meeting useful

ground on their first flight wherethey are eaten by crabs

The Christmas Island GIS andtechnical advice provided by AGSOhas facilitated a situation where theisland has been shipping up to 700 000 tonnes of phosphateannually This is being combinedwith maintenance of the environ-mental values in the islandrsquosextensive national park

The successful outcomes forthe islanders government industryand wildlife have led to furtherrequests for help with land-usedecisions The most recent arecurrent projects on Nauru andCocos Island

There was also an unexpectedoutcome Being near the equatorChristmas Island is an ideallaunching site for satellites

lsquoWith our high-quality digitalinfrastructure we were able to sitdown with the proponents andidentify the most suitable site forthe facility in a matter of hoursrsquosays Dr Lambert

lsquoWe rapidly found a site thatminimised sterilisation of phosphateore and many of the associatedproblems such as loss of livelihoodand compensation to the miningcompanyrsquo he says

lsquoIt also minimised earth worksrequirementsrsquo he added

Australian palaeomagnetism rock magnetism amp environmental magnetism

ScopeThe program will be informal and will combine the presentation of newresults discussion of problems and development of new initiatives Theemphasis will be on the applications of palaeomagnetism rock magnetismand environmental magnetism and their effectiveness for problem solvingUsers and potential users will have an opportunity to learn more about thetools employed and how they might be of benefit to them

StructureThe first day of the meeting will cover a range of topics and will include aninvited talk by Professor Chris Powell The second day will centre on adiscussion of the Palaeozoic apparent polar wander path for Australia

CostThe meeting is being held at the Australian Geological Survey Organisation inCanberra A registration fee of $30 covers the cost of light refreshments andminor benefits A dinner will be held on Wednesday evening (May 3) at acost not exceeding $35 per person

If you are interested in attending please phone Charlie Barton on +61 2 6249 9611 or e-mail charlesbartonagsogovau

The futur eAGSO will continue to develop and apply GIS-based DSS that can integrateweigh and model diverse data on known and potential mineral and petroleumresources and other geoscience values with environmental and other landvalues including those related to land and water degradation

lsquoCurrently we are collaborating with the Bureau of Rural Sciences to makea powerful and adaptable decision support system by combining the RFA GISsystem with the ASSESS system used to identify suitable sites for a national low-level radioactive waste sitersquo says Dr Lambert

lsquoWe will use this system to integrate and analyse detailed and diversedatasets at a range of scalesrsquo

Other important geoscience data layers that will be dealt with increasinglyin land use DSS include radiometric layers and airborne magnetics andelectromagnetics Radiometric layers can assess the distribution of naturalradioactivity and assist with geological regolith and soil mapping Airbornemagnetics and electromagnetics will be used more widely to help inunderstanding the extent and causes of land degradation including salinity andacid sulphate generation

Dr Lambert emphasised that collaboration and data sharing betweengeoscience land management and environmental agencies can only bebeneficial

In addition to these interesting decision support projects AGSOrsquos Resourcesand Advice activities encompass many other tasks These include publishingeach year a report on Australiarsquos known mineral stocks for all major and severalminor commodities contributions to the lsquoRed Bookrsquo on international uraniumresources and demand advice on on-shore and offshore exploration miningand processing as well as on metals and the environment

For further information phone Ian Lambert on +61 2 6249 9556 or e-mail ianlambertagsogovau



The Geological Society of Australia and theScience Educators Association (ACTdivisions) launched their Mentor andResource Link program at AGSOrsquos neweducation centre on March 13 At this stage itis a pilot program for what will most likelybecome a national scheme

Canberra is initiating the programbecause it has ideal conditions for itssuccess

lsquoIn Canberra you have the happycoincidence of a medium-sized population of300-odd thousand people 29 high schoolsand colleges and a very high concentrationof geoscientists at AGSO the Bureau of RuralSciences CSIRO and the universitiesrsquo saysGreg McNamara manager of AGSOrsquos EarthScience Education Centre

lsquoWersquove got the concentration of professionals that can mentor andmanageable numbers of teachers and students in need of that servicersquo

ACT Chief Minister Kate Carnell and ACT Education Minister BillStefaniak launched the program

Ms Carnell says that mentor programs like this one that provide a vitallink between education science and the Australiarsquos future are endorsed byher government

She says that given the importance of earth sciences to Australia she isvery lsquoproudrsquo that Canberra has been chosen to pilot the program

lsquoSince the gold rush of the 1850s Australiarsquos mineralexports have brought the country wealth and created a lot ofopportunities not only in geology and mining but also inresearch government tourism urban planning anddevelopmentmdashand the list goes onrsquo she says

lsquoAnd even though our export base is changing over timeto focus on such things as tertiary products and informationtechnology our mineral resources still contribute significantlyto the countryrsquos export earningsmdashand will continue to do sorsquo

She says that for the last 150 years those involved in earthsciencesmdashwhether it be in industry research or even teachingthe next generation of geoscientistsmdashhave played anenormous part in Australiarsquos development and its future

Mr Stefaniak thanked the ACT division of the GSA for itseducation policy that shows long-term commitment towardsimproving teaching and learning in scientific andenvironmental studies in Canberra

lsquoWe have a lot of students that are going to get enormousbenefit out of this programrsquo he says

AROUND the divisions

lsquoI give my whole-heartedsupport to this outreach programbecause it will not only giveteachers help when and where it isneeded but it will also motivatestudent involvement in earthsciences well beyond their years ofschoolingrsquo

The idea for the program wasfloated in Canberrarsquos geosciencecommunity in mid-1999 and 70scientists put their names forwardas possible mentors

The mentors are volunteeringto respond to teacher calls for helpThe type of help requested willvary But it can be as simple ashelping teachers find information ora book in a general library orAGSO library or lending somematerial from a personal collectionIt could also involve talking tostudents or being involved in asession at the Earth ScienceEducation Centre

Mentor details are held on adatabase in the education centreThe centre will also obtainquarterly and half-yearly feedbackfrom mentors and teachers whohave used the program

For more details phone GregMcNamara on +61 2 6249 9571or e-mail gregmcnamaraagsogovau

ACT Chief Minister Kate Carnell (centre) sharesanecdotes with guests at the launch of the Mentor andResource Link program (From left) Greg McNamaraPatrick Lyons (Secretary GSA ACT) Ken Lawrie (ChairGSA ACT) Sonia Cousins (GSA Promotions andEducation Manager) Neils Hider (Vice-presidentSEAACT) and ACT Education Minister Bill Stefaniak

Australian Capital TerritoryChief Minister Kate Carnelland Education Minister BillStefaniak thumb through someof the many resourcesavailable in AGSOrsquos EarthScience Education Centre

Happy coincidence idealfor nationalprogram pilot

On February 21 this year the Endeavour space shuttle on a voyage toacquire data on the Earthrsquos topography extended its mission by 10 minutesto include a final pass over Australia

All of Australia was covered with one pass and roughly 94 per cent with asecond pass The shuttle collected Australian data during its ascending orbits(south to north) and after reflector orientation changes during its descendingorbits Repeat passes were designed to improve the quality of elevation data

Approximately 123 million square kilometres of Earth were mappedduring the 11-day mission Most land surfaces between 60+- degrees latitude were mapped

DID YOUknow


Public awareness an essential element of the

Papua New GuineandashAustraliaVolcanological Service Support

(VSS) Project will be steppedup in late April with the release

of a new information kitlsquoDangerous volcanoes of

Papua New Guinearsquo prepared by AGSO and the

Rabaul Volcanological Observatory (RVO)

This kit is part of an ongoingcampaign directed at giving PNGrsquospeople accurate information aboutthe volcanoes they live with andensuring that valuable equipment isnot damaged or removed frommonitoring sites In the past thesevolcanoes killed people anddestroyed homes and crops

The campaign began threeyears ago in the Rabaul area priorto starting the Rabaul EarthquakeLocation and Caldera Structure(RELACS) survey This geophysicalsurvey of the Rabaul calderainvolved the temporary deploymentof many land and ocean bottomrecorders around the GazellePeninsula to increase what wasknown about the deep structure ofRabaul volcano

lsquoWe had a lot of recordersaround the Rabaul area and weknew very early in the project thatwe had to make sure theequipment was not damaged orstolenrsquo says project team memberShane Nancarrow


A R O U N D T H E D I V I S I O N S

Elevation data were acquired by special equipment on Endeavournamely radar electronics and antennas in the payload bay and once inspace a 60-metre mast with outboard antennas attached to its end Radarwas used because it operates day and night and penetrates cloud coverAntenna in two separate places on the shuttle produced two differentimages The difference between the two images is used to calculate surfaceelevation All mapping data were saved to recording devices onboard

The preliminary digital elevation maps available use data from a singlemapping pass and have not been calibrated or verified Precision productswill be generated over the next two years and eventually a comprehensivehigh-resolution three-dimensional map of Earth will be available

A research teamfrom AUSLIGAustraliarsquos nationalmapping agency willhelp validate theAustralian elevationdata

P N G V O L C A N O A W A R E N E S S I N C R E A S E DW I T H C A M P A I G N H E L P

The latest information kit lsquoDangerous volcanoes of Papua New Guinearsquo published in Pidgin English

Armed with information brochures and a video produced by the VSS

Project titled The voice of Kaia RVO Community Liason Officer DonaldOkole and observatory staff visited villages schools and community groupsaround the Gazelle Peninsula area They built awareness of the RELACSsurvey and the importance of the work being performed Local people wereasked to care for the RELACS equipment and the extensive state-of-the-artnetwork that the RVO was using to forecast any future eruptions of thevolcanoes in the area As a result only a few minor incidents wereexperienced

The role of RVO staff was expanded to include regular visits to theRabaul community and to invite local people on observatory tours

lsquoVisiting the observatory that sits high up on the caldera wall was a bigstep for some localsrsquo says Mr Nancarrrow

lsquoHistorically local people would not go near the site and the observatorydid not encourage visitsrsquo

Since the campaign started many groups have visited and the theft andvandalism rate of the RVO network has been reduced

lsquoWersquore finding that local people have taken a real interest in theobservatory and are trying to be as helpful as they canrsquo he says



Perfectzircon forrock datingno fairytale

nce upon a time in apaddock 30 kilometres eastof the little country town

of Temora in New South Walessomething wonderful happened tocreate an intrusion of gabbroicdiorite housing almost pure-statezircon crystals that might soon beused worldwide as a standard fordetermining rocks ages

The zircon-containing rocksburied for 417 million years havebeen partly exposed in recent timesas civilisation reached the remotepaddock Road building telecom-munications cables and a farmerbulldozing his land brought someof them to the surface

lsquoWersquove been searching for 20years for zircon of this qualityrsquo saysDr Lance Black AGSO scientist andone of the geologists who broughtthe rock in for initial study

lsquoWe searched in South AustraliaSri Lanka Canada the United Statesand Europe for high-quality zirconthat would be suitable as astandard but all have had somesort of drawback and provenfrustratingly imperfectrsquo

Circumstance has made theTemora rocks and their zirconcrystals special


Due to the success of the Rabaul public awareness campaignactivities now will include the four other high-risk volcanoes associatedwith the projectmdashUlawun Karkar Manam and Lamington

The new information kit is printed in Pidgin English and EnglishmdashPNGrsquos two main languagesmdashand has a companion video a 30-minutedocumentary titled Living with volcanoes (also in the two languages)The kit is very pictorial because photos and cartoons will help RVO staffmembers tell villagers some of whom have low literacy levels abouttheir volcanoes the observatoryrsquos role and evacuation procedures

Mr Nancarrow says that the PNG Department of Mining the WestNew Britain Provincial Government and the National DisasterManagement Office have been very supportive of the campaign

lsquoFor a start the National Disaster Management Office supplied 17 500 kina towards producing this kitrsquo he says

Schools also have appreciated these materials In addition tocampaign materials last Christmas all 147 high schools in PNG weresent a teacher resource package by the project It contained textbooksand posters on volcanoes earthquakes and landslides

lsquoWersquove already had positive feedback from some schoolsrsquo MrNancarrow says lsquoTheyrsquove sent very nice letters to us the Australian HighCommission and the RVO expressing their thanksrsquo

The PNGndashAustralia VSS Project is funded by AusAID the AustralianGovernmentrsquos international development agency

In a paddock miles from anywhereAGSO scientists found this bouldercontaining extremely pure zirconcrystals that will allow scientistsaround the world to date rocks moreaccurately than has previously beenpossible

Letter of thanks to the VSS Projectfrom one PNG high school for thelearning materials they received last Christmas

M A J O R P R O G R E S S F O RG E O L O G I C A L U N I T S D A T A B A S EThe Australian Geological Units database was given a huge boost inJanuary-February when more than 600 bibliographic references andnew information on 13 000 geological units including about 1400 newnames were added to the database by 10 temporary staff employedduring university holidays

New geological references were indexed for stratigraphic namesand other geological unit data As well the data for many of theexisting units was upgraded to include information such as agegeological province and any changes to unit rank or relationships withother units Also updated were the indicators that show whichreferences contain the most information The boost to the database is inaddition to on-going indexing and the backlog project

The backlog project is gradually getting all old card-file datagathered prior to 1969 into the on-line database Most of theexplanatory notes from around Australia have been captured as well asalmost all of the Queensland references data that AGSO held on cardsData capture is well underway for the other States

The Australian Geological Units database can be queried on-line athttpwwwagsogovauinformationstructureisddatabasestratnameshtml

For further information phone Cathy Brown on +61 2 6249 9535or e-mail cathybrownagsogovau

O



Left buried and undisturbed for millions of years the rocks have notsuffered the extremes of surface temperature and weathering Theycrystallised high in the earth probably about two kilometres from thesurface and havenrsquot undergone any extreme geological event since theyformed As well the composition they inherited when they formed provesidealmdashthere is only one generation of zircon present

lsquoThese rocks are derived from the melting of rocks that didnrsquot havezircon in themrsquo says Dr Black

lsquoSo we donrsquot have the problem of zircon from the parent rockcontaminating the zircon of the new rock

lsquoSuch mixtures complicate working out how much lead or uranium hasbeen lost or gained from the zircon that actually crystallised in the rockrsquo

The scheme used to date rocks is based on the radioactive decay ofuranium Minute traces of uranium locked inside the zircon crystals havebeen decaying over aeons producing lead Scientists know that the decayoccurs at a fixed rate and how quickly it happens By measuring the relativeamounts of uranium and lead encased in the crystals scientists candetermine how old the rock is

But sometimes lead is lost from zircon crystals via processes such asweathering (if the rocks were exposed on the surface) or deformation andmetamorphism (if the rocks had crystallised deep in the earth and beensubjected to high temperatures and pressure) Hence the special nature ofthe Temora rocks

There are many other older zircon-containing rocks in Australia Theoldest zircon recorded on Earth about 4280 million years old was found inWestern Australia But its circumstancesmdashformed deep in the Earth crystalsdamaged by radioactive decay its long and complicated history and leadlossmdashmake the zircon unsuitable as a standard for dating rocks

Zircon dating allows scientists to get the relative (and more importantlyabsolute) ages of rocks when they canrsquot be determined by fossils or othermeans like stratigraphy The age of a rock helps scientists determine thesequence in which rocks formed and their relationship to each other Thisinformation leads to a better understanding of how the Earth formed andevolved and helps in predicting where ore bodies and petroleum could befound

There are different methods of dating zircon One involves chemicaldecomposition of the zircon crystal (thermal ionisation mass-spectrometry)and another is a micro-beam technique called lsquoSHRIMPrsquo (sensitive high-resolution ion micro-probe) The chemical decomposition method does notrequire a zircon standard and the zircon is dissolved in the process SHRIMPon the other hand is not particularly destructive and a beam of chargedoxygen makes a micron-deep crater in the crystal The zircon crystaltherefore can be dated many times and different parts individually analysed

SHRIMP dating was used for initial tests on the Temora rocks Then inDecember last year the sample was sent to the world-recognised authorityCanadarsquos Royal Ontario Museum for independent analysis and dating viachemical decomposition The museum confirmed the near perfect quality ofthe zircon and its age

Early this year Dr Black andscientists from the AustralianNational University (ANU) returnedto the paddock to recover anothertonne of Temora rock

From this 40 to 100 grams ofzircon crystals should be extractedSome of these crystals are under-going the same tests as the firstsample By September scientists willknow whether there is enough nearperfect Temora zircon to meet theworldrsquos geochronological demandsfor decades

If not there is enough from thefirst boulder to maintain a 10-yearlocal supply

Dr Black says that both fine-grained and course-grained varietiesof gabbroic diorite are found in thepaddock Current tests shouldresolve whether the considerablymore abundant zircon in the coarsephase is as ideal for dating as that inthe already proven fine-grained rock

The rocks were discovered on aroutine sampling trip as part of theLachlan mapping project It wasFriday afternoon and the last sitegeologists visited on that trip

lsquoThe rock looked nice and freshbut it did not have much silica in itand so we thought it was unlikely tocontain zirconrsquo says Dr Black

They had doubts about whetherthey should bother to take samples

lsquoHowever we did and when weseparated it in the lab we found thatnot only did it have zircon but itwas all of the same type

lsquoSo we talked to Dr IanWilliams leader of the SHRIMPgroup at ANU and it all progressedfrom therersquo

For more details phone LanceBlack on +61 2 6249 3125 or e-mail lanceblackagsogovau

Pictured with the 417 million-year-old rocks that caused much excitement are (from left) property ownerBarry Wiencke and the AGSO team Morrie Duggan Lance Black and Jon Claoue-Long



1st


While most Australianscelebrated Christmas and New

Year at home three AGSOscientists were at sea mappinga huge area of seafloor never

before surveyed off Australiarsquossouth-east coast

The AUSTREA-1 survey wasphase one of the first major

research program underAustraliarsquos $50 million Oceans

Policy a national plan aimedat protecting and managing

Australiarsquos oceans Leader ofthe four-week lsquocruisersquo AGSOrsquos

Peter Hill gives a run-down onphase one

Figure 1 The track of LrsquoAtalante during AUSTREA-1 showing survey areas betweenLord Howe Island and the Great Australian Bight AUSTREA-1 complementedexisting AGSO swath-mapping surveys (Tasmante 1994 Sojourn7 1997)

Figure 2 Lord Howe Island and Ballrsquos Pyramid lsquohot-spotrsquo volcanomdashthe 3D image isbased on the AUSTREA-1 multibeam data below 300 metres water depth Therugged terrain on the flanks of the seamount (flows canyons volcanic cones andpinnaclesmdashmany 200ndash300 metres high) suggests diverse ecosystems

Figure 3 Seafloor topography and canyonsystems of the Bass Canyon Complex off

Gippsland produced from AUSTREA-1swath data merged with data from AGSOrsquos

1997 Sojourn7 survey The view is to thenorth-west and shows an area about 150kilometres across The 2000 metre deep

15 kilometre wide Bass Canyon has been aconduit for sediment shed off the adjacent

land and shelves for at least the past 50million years The Gippsland oil fields are

located on the shelf immediately to thewest and the canyon heads are important

deep-sea fishing grounds

Seabed images

off south-east Australia a first


1st


O C E A N G O I N G

On January 11 the 85-metre French oceanographic and geoscience researchvessel LrsquoAtalante berthed in Hobart completing a successful seabed swath-mapping and geophysical survey that began in Noumea 25 days earlier

Commissioned by Environment Australia and the newly establishedNational Oceans Office the survey is the first of two AUSTREA geoscienceresearch cruises to be carried out by AGSO off south-east Australia this year

The cruises provide scientific information on bathymetry and seabedstructure for not only geological but also biological research Data gatheredwill be used for marine zone planning and management and assessingseabed living and non-living (petroleum and mineral) resources They are amajor step towards implementation of Australiarsquos Oceans Policy and itsMarine Science and Technology Plan

Area coveredAUSTREA-1 covered 11 thousand kilometres and mapped approximately 120thousand square kilometres of seabedmdashan area about 15 times the size ofTasmania (figure 1) Notable areas surveyed includebull the submarine volcanic slopes of Lord Howe Island (figure 2) and the

proposed marine protected area out to 12 nautical milesbull the rugged canyoned continental slope off the New South Wales south

coastbull offshore Gippsland Basin and the spectacular Bass Canyon complex

(figure 3) This extends the area swath-mapped by AGSO in 1997bull deep-sea fishing grounds and frontier petroleum basins off east south

and west Tasmania This extends the area swath-mapped by AGSO in1994 and 1997

bull submarine volcanoes south of Tasmania including the eastern part of theTasmanian Seamounts Protected Area Thirty new volcanic cones weremapped

bull deeply canyoned and generally sedimented continental slopes offnorth-west Tasmania south-west Victoria and Kangaroo Island

bull the Great Australian Bight Benthic Protected Area of the GAB MarinePark The research team found that this was generally a uniform slopebut that the gigantic Nullarbor Canyon crossing its south-eastern corneris gouged deeply into deformed Late Cretaceous to early Tertiarysediments

The maps and ideas generated by this and earlier geoscience cruises willbe the basis for follow-up biological sampling and seabed acoustic studiesearly this year

CSIROrsquos research ship Southern Surveyor will be used for a series oflinked research cruises involving AGSO CSIRO and the National OceansOffice The maps produced showing seabed shape character and habitatswill provide basic information needed by the Hobart-based National OceansOffice for development of the South-east Regional Marine Plan

The second phase of the AUSTREA surveys takes scientists to MacquarieIsland Marine Park and southern parts of Australiarsquos Exclusive EconomicZone A summary of this phase will be published in the June issue ofAUSGEO News

Research team andequipmentLrsquoAtalante pride of the Frenchresearch fleet is equipped withone of the most powerful multi-beam swath-mapping systems inthe world the Simrad EM12DAUSTREA-1 scientists used this anda wide range of other state-of-the-art geophysical and oceanographicsurvey systems including a six-channel GI-gun seismic a digital35 kHz sub-bottom profiler gravitymeters a magnetometer and anacoustic doppler current profilerWith this equipment they couldmap approximately 400 squarekilometres of seabed an hour andto ocean depths of more than 5000metres In addition the seismicequipment allowed them to analysesedimentary strata up to fivekilometres beneath the seafloor inthe Gippsland Sorell Otway andGAB Basins and off easternTasmania

On board LrsquoAtalante for phaseone were five Australian scientistsand 31 French crew engineers andtechnicians The lsquoAustralianrsquoscientific team comprised AGSOrsquosPeter Hill Nadegravege Rollet and DavidRowland as well as Clive Calver ofMineral Resources Tasmania andJonathan Bathgate of the Universityof Sydney

For more information phonePeter Hill on +61 2 6249 9292 ore-mail peterhillagsogovauor contact Gordon Anderson ofthe National Oceans Office byphoning +61 3 6221 5009 or e-mailing gordonandersoneagovau

lsquoAustralianrsquo scientists (from left) Nadegravege Rollet Peter Hill David Rowland

and Clive Calver celebrate success at anend-of-cruise function on LrsquoAtalante



The FAUST-2 survey a 32-day program fromNovember 12 to December 13 1999 mappednearly 190 thousand square kilometres ofcomplex bathymetry between Norfolk Ridge inthe west and Three Kings Ridge in the east

It covered a unique part of Australiarsquosmarine jurisdiction that contains evidence forconvergent tectonism related to collision andsubduction along the eastern margin of theAustralia plate (figure 1) Several importanttectonic features were studied such as possiblesubduction-related island arcs and extensionalback-arc basins lying between major boundingfracture zones (the Cook and Veining-Meineszfracture zones)

The survey was carried out on board theFrench research vessel LrsquoAtalante It has amultibeam sonar Simrad EM12D swath-mapping system capable of producing contourmaps and reflectivity imagery of the sea-floorin a swath up to seven times as wide as thewater depth In addition high-speed seismicand potential field systems were used andthree dredge hauls obtained rocks frombasement scarps throughout the area surveyed

Approximately 13 300 kilometres of swathmultibeam data and 35 kHz echosoundergravity and magnetic data along generallynorth-north-east to south-south-west orientedsurvey lines were acquired (This equates to aswath coverage of an area more than 25 timesthe size of Tasmania) High-speed seismicreflection magnetic and gravity profiles wererecorded along most of the survey lines Thesedata represent a quantum leap in knowledgeof this poorly known area

Picture builds for

AUSTRALIArsquoSE A S T E R N L I M I T S

Australia is trying to confirm the extent of its seabedjurisdiction (extended continental shelf) east of the 200

nautical mile Australian Exclusive Economic Zonearound Norfolk Island

To get a clearer picture of the region the FAUST-2 cruisewith AGSO and French scientists on board set sail in

mid-November last year for an area of complexmorphology to the east of the Norfolk Ridge Results arestill being compiled but cruise co-leader Phil Symonds

outlines some of what was found

Figure 2 Colour-gridded hill-shaded bathymetric map of the FAUST-2study area based on the LrsquoAtalante swath-mapping data merged withpredicted bathymetry from satellite altimeter data FAUST-2 dredge sitesand the Australian Exclusive Economic Zone (AEEZ) are shown

Figure 3 Pseudo-3D perspective viewfrom the south of the FAUST-2

bathymetric data


O C E A N G O I N G


Resul tsThe survey has added to data from a 1997 Rig Seismic deep-seismicsurvey in the region conducted for marine zone definition purposes incollaboration with the New Zealand Ministry of Commerce

The results of the FAUST-2 survey are currently being interpreted inAustralia and France They will provide important new insights into thetectonic development and marine environment of this complex unusualand virtually unknown part of Australiarsquos marine jurisdiction Significantresults from the survey so far include the following

Large elongate and small clustered volcanic sea-mounts werediscovered to the east of the Norfolk Island platform on the saddle thatseparates the North and South Norfolk Basins (figures 2 amp 3) Some ofthese features are up to 30 kilometres in length and shallow (from about2250 to 800 metres depth) The largest sea-mount mapped occurs indeeper water further east It is about 50 kilometres long 28 kilometreswide and rises about 2800 metres above base level to a flat top at about660 metres water depth

Also found were several flat-topped sea-mounts that rise from thecrest of the Three Kings Ridge at about 2000 metres depth to within 500metres of sea level

There is a narrow (about 20 km) north-south trending trough thatvaries in depth from 2800 metres in the south to 4000 metres in thenorth It separates a smooth terrace-like area at about 2500 metres depththat forms the western flank of the Three Kings Ridge from a region ofmore complex bathymetry to the west This trough which appears tolink with the Cook Fracture Zone in the north shows evidence fornormal faulting on its western flank but possibly some compression onits eastern flank Dredging of an apparent tilt block on the westernmargin of the terrace in the south of the survey area (figure 2) produceda full chain-bag containing a variety of sedimentary rocks (figure 4)These included a large volume of conglomerate that contained sub-rounded pebbles and boulders of mainly basaltic composition

The most spectacular bathymetric feature in the FAUST-2 survey areais the 400 kilometre long Cook Fracture Zone that separates the Norfolk-Three Kings Ridge region from the northern part of the South Fiji Basin(figures 2 amp 3) The fracture zone is a very linear and complex strike-slipsystem that links the Three Kings Ridge in the east with the LoyaltyRidge in the west Many classic strike-slip features imaged within thefracture zone indicate that the most recent movement along it is left-lateral Dredging on the southern wall of the Cook Fracture Zone to thewest of Three Kings Ridge (figure 2) obtained a full chain-bag of mainlybasaltic rocks including tectonised pillow basalts

The new data show that there is a continuous but complexconnection between the Norfolk Island platform in the west and theThree Kings Ridge in the east that averages about 2500 metres deep andis nowhere deeper than 3200 metres In comparison the adjacent deeperareas of the South and North Norfolk Basins and South Fiji Basin varyfrom 3500 to more than 4000 metres deep

Four cruisesThe FAUST-2 survey was the result of an agreement between AGSO andIFREMER (Institute Francais de Recherche pour lrsquoExploitation de la Mer)to exchange Rig Seismic and LrsquoAtalante ship time

In October 1999 AGSO and IFREMER embarked on a major programof four seabed-mapping surveys off eastern and south-eastern AustraliaThe initial two cruises were conducted from October to December 1999The first over the northern Lord Howe Rise and Fairway Basin wasreported in the February 2000 issue of AUSGEO News FAUST-2 was thesecond cruise

The FAUST-2 cruise included 12 scientists and technicians fromIFREMER AGSO CNRS-INSU Universiteacute Pierre et Marie Curie (Paris)Services des Mines et de lrsquoEnergie (Noumea) University of LilleUniversity of Perpignan Institute de Physique du Globe de Paris and theUniversity of Sydney It was led by Alain Mauffret (Universiteacute Pierre etMarie Curie) and Phil Symonds (AGSO)

The other cruises (December 1999 to February 2000) were contractedby AGSO for the National Oceans Office These were carried out offsouth-east Australia (see article on AUSTREA-1 this issue) and south ofMacquarie Island

Figure 4 Deformed pillow basalts fromdredge site 3 (D3 figure on oppositepage) on the southern flank of the Cook Fracture Zone

For further information contactPhil Symonds by phone +61 26249 9490 fax +61 2 6249 9920or e-mail philsymondsagsogovau

Figure 1 Bathymetric map of the Norfolk-Three Kings Ridge region based onpredicted bathymetry from satellitealtimeter data This figure shows thelocation of the LrsquoAtalante FAUST-2 survey area Abbreviations CFZmdashCookFracture Zone NNB amp SNBmdashNorth andSouth Norfolk Basins VMFZmdashVeiningMeinesz Fracture Zone


Ever since it was noted in Scotland more than 200 years ago thatgranite dykes were intrusive into metamorphic rock controversyhas raged over the origin of granites

In the past the debate focused on whether granites are of metamorphicorigin or formed by the crystallisation of magmas Today the arguments areabout their source rocks and the reasons for compositional variation

Apart from a desire to answer such questions granites should be givenattention because they are an abundant rock and they have metallogenicimplications Answer the questions about granites wersquore told and wersquollknow more about the evolution of Earthrsquos crust and have a few more ideason where to look for ore bodies

WorkshopOn December 10 last year a Granite Workshop was held at AGSO forsponsors of the AMIRA (Australian Mineral Industries Research Association)project on Igneous Metallogenic Systems of Eastern Australia and othergeologists Two well-known granite aficionados presented the workshopProfessor Bruce Chappell from Macquarie University and Dr Allan Whitefrom the University of Melbourne

Sui tesBoth presenters emphasised assigning granites to lsquosuitesrsquo and lsquosupersuitesrsquoThey argued that the suite concept was a key to understanding thepetrogenesis of granites

A suite was defined as a group of granitic rocks with commonpetrographic mineralogical and compositional characteristics When granitesare assigned to a suite an assumption is made that the rocks of a singlemappable unit (referred to as a pluton) are co-magmatic Suites can comprisemore than one pluton and these plutons donrsquot necessarily come from asingle magma body What is important is that they have either the samecomposition or the same compositional trends

Supersuites are categories for granites with small compositionaldifferences that prevent them from being neatly grouped within a suite Inother words if a few elements differ then the rocks are members of thesame supersuite rather than the same suite

Granites produced millions of years apart that show small differenceswould be assigned to a supersuite The age of the rock therefore is probablynot relevant when assigning granites to suites The importance of isotopiccomposition when grouping granites is also questioned because granite canbe derived from heterogeneous source rocks

Composi t ionQuartz potassium feldspar and plagioclase are common to all granites Howmuch of each of these is present in the rock depends on its evolutionStrangely irrespective of the dispersion of composition fairly predictablevolumes of sodium potassium and silica are present in almost all felsic orlight-coloured granites (roughly 35 Na2O 45 K2O and 72 SiO2) Thecomposition of other granites is not as simple and eventually approaches thecompositions of the source rocks

Professor Chappell says that no matter how the granites evolvedrubidium is an index for the degree of evolution Granites with largeamounts of rubidium are more felsic more evolved and highly fractionatedand more likely to be mineralised

Variations in geochemical composition of suites in eastern Australiasuggest that different processes could have produced the granites Variousmodels have been put forward for the variation including magma mixing ormingling assimilation or contamination by lsquocountryrsquo rock fractionalcrystallisation restite crystal fractionation varying degrees of partial meltinghydrothermal alteration and variation in source rock composition


WORKSHOPSseminars

In the simplest suites ProfessorChappell suggests that the rockswere formed from magmas derivedby partial melting of quartzofelds-pathic rocks Variations within thesuite resulted from restite (solidmaterial) and melt fractionationThe granite therefore couldcomprise parent material productsof melt reactions and melt

Generally speaking low-temperature granites belong tosimple suites while high-temperature ones belong to morecomplex suites

Mineral i sat ionIn simple suites there is nomineralisation Therefore donrsquotexpect to find minerals in therestite-fractionated suites of easternAustralia The granites associatedwith mineralisation are high-temperature granites those thathave undergone extensive fractionalcrystallisation

One notable example ofmineralisation associated withhighly fractionated rock is the tin-bearing Ardlethan Granite in NewSouth Wales Other examples arethe tin deposits of England(Cornwall) Bolivia and Thailand

Dr White says that he has nodoubts that granites also produceporphyry copper

lsquoWhen you go to a bigporphyry copper deposit likeBingham Utah that has alsoproduced a thousand tonnes ofgold there is no doubt that themineralisation is directly derivedfrom the granitersquo he says

Granites of the porphyrycopperndashgold deposits are oxidisedand high in barium

lsquoOlympic Damrsquo Dr White sayslsquois a good example It is loadedwith bariumrsquo

Dr White has also often seenmolybdenum veins near porphyrycopper

lsquoFor example in Butte MontanaI went into the mines before theyclosed and beneath the porphyrycopper pit I saw a lot of ldquomollyrdquoveinsrsquo he says

Dr White suggests that depositsof these minerals are directly related

The biggest lsquomollyrsquo deposits heknows of are in the mineral belt ofColorado where the granite is

Mineralisation complexbut suite story in GRANITE


Twenty-four countries were represented at the third international conferenceon geoscience education (GeoSciEd III) held at the University of New SouthWales in Sydney from January 16ndash21 Although official delegate numberswere modestmdash174 in allmdashfor international conferences those participatingwere fired up about the importance and relevance of teaching geoscience

lsquoThe opportunity to share ideas and resources are limited for just aboutall geoscience educators because many do it as an adjunct to their regularjobs as geologistsrsquo says Gary Lewis Manager of AGSOrsquos GeoscienceAwareness and Marketing Unit

AUSGEO news 57 Apri l 2000 27

W O R K S H O P S S E M I N A R S

Mr Lewis says it was a greathonour for AGSO to be one of theconference conveners and he feltproud when Australia wasapplauded for its attention togeoscience education

GeoSciEd IV will be held inCalgary Canada in 2003

For more details phone GaryLewis on +61 2 6249 9570 ore-mail garylewisagsogovau

G E O S C I E N C E E D U C A T I O N O NI N T E R N A T I O N A L A G E N D A

On duty in the AGSO booth at the 3rd GeoSciEd international conference are (l-r)Cindy Trewin Gary Lewis and Greg McNamara from the Geoscience Awarenessand Marketing Unit

Are you on AGSOrsquos mailing list forthe quarterly report AustralianPetroleum Exploration andDevelopment Activity If yoursquore notthen you may not know that therewere 11 offshore and 11 onshorepetroleum discoveries in 1999 andthat there were significant discov-eries in the Carnarvon Basin offnorth-west Australia

The report lists the discoveriessummarises drilling and rig activityand outlines seismic survey activityNumerous tables and figures precissuch data as number and type ofwells metres drilled and thelsquosuccessrsquo rate over the last decade

The latest report whichsummarises activity to the end of1999 shows that the total of 51offshore exploration wells drilledlast year is on par with the averagenumber drilled over the last 10years There was a significantincrease in offshore explorationdrilling in the last quarter but adrop in onshore exploration drillingfor the year

Without knowing what effecthigh crude oil prices will have onexploration budgets and drillingprograms this year the industryforecast is an average of 54exploration wells drilled offshoreand 59 onshore in 2000

AGSO gathers the reportrsquosstatistics from various sourcesincluding the petroleum explorationindustry and State and Territorymines departments

There is no subscription fee forthis report so if you want to be onthe mailing list contact AGSOrsquosSales Centre

For more on the informationcontained in the report phone Eugene Petrie on +61 2 6249 9270 or e-maileugenepetrieagsogovau

oxidised but more highly fractionated than in porphyry depositsDr White also mentioned that a number of big deposits occur in quartz

monzonitemdashButte Montana Bingham Utah The quartz monzonites andgranites have fractionated from monzonite magmas (shoshonites are the fine-grained equivalents of monzonite) He believes that a large magneticanomaly below Olympic Dam could be monzonite At Cripple CreekColorado gold occurs in an alkaline shoshonite complex

lsquoI wonder if the more monzonitic rocks produced all the goodiesrsquo he says

Ideas on mineralisation are controversial and the debate about the originof granites still rages No doubt the complexities will take time to unravel butthe suite concept may just hurry along the process

Stay updated withquarter ly petroleumexplorat ion report

lsquoSo there is a real hunger for teaching materials and contact with otherstrying to give geoscience the prominence it deservesrsquo he says

Mr Lewis says the delegatesrsquo enthusiasm for geoscience education wasevident in the fact that some of them had to raise funds to attend theconference

lsquoThis was especially true for delegates from developing countries such asthe Philippines Bangladesh and Mozambiquersquo

At one key meeting during the conference the International GeoscienceEducation Organisation (IGEO) was launched The IGEO aims to raise publicawareness of geoscience and promote geoscience education internationallyIts main function will be fostering communication worldwide amonggeoscience educators and geoscientists Membership of this organisation isfree

Another important part of the conference for geological and socialpurposes was a field trip to Prospect Park Water Reservoir the BlueMountains and the Jenolan Caves


EVENTScalendarCompiled by Steve Ross


Australian Science Festival

29 April to 8 May

Various venues Canberra

Contact Australian Science FestivalPO Box 193 Civic Square ACT 2608

phone +61 2 6205 0588

fax +61 2 6205 0638

wwwsciencefestivalcomau

AGSO Open Day

7 May

AGSO Building Canberra

Contact Steve Ross at AGSO

phone +61 2 6249 9263

fax +61 2 6249 9990

e-mail steverossagsogovau

2000 APPEA Conference andExhibition Innovations for theThird Millennium

Australian Petroleum Production andExploration Association

7 to 10 May

Convention amp Exhibition CentreBrisbane

Contact APPEA GPO Box 2201Canberra ACT 2601

phone +61 2 6247 0960

fax +61 2 6247 0548

e-mail lgordonappeacomau

Broken Hill Exploration Initiative5th annual conference

29 to 31 May

Field excursions 26 to 28 May 1 to 2 June

Entertainment Centre Broken Hill

Contact George Gibson at AGSO

phone +61 2 6249 9727

e-mail georgegibsonagsogovau

16th World Petroleum Congress

11 to 15 June

Calgary Canada

Contact 16th WPC CanadianOrganising Committee 1350 144Fourth Avenue SW Calgary AlbertaCanada T2P 3N4

phone 0011 1 403 218 2000

fax 0015 1 403 218 2002

e-mail cdnassocwpc2000comm

AGSO has released a first version of OZCHEM its whole-rockgeochemical database of major and trace element analyses of Australianrocks This database was previously known as ROCKCHEM

lsquoOZCHEM release 1rsquo features data from 29 547 samples fromAustralia and includes data from about 3438 new analyses Its highlightsinclude the geochemical data from analyses of1 Bottom-of-hole samples from the seismic traverse across the Mt Isa Inlier2 Bottom-of-hole samples from the seismic traverse across the Broken Hill Block3 Bottom-of-hole samples from the seismic traverse across Tasmania

(TASGO project)4 Samples from drillcore in the Gunnedah and Cranky Corner Basins

mostly of clastic sedimentary rocks5 Granites granodiorites and syenites (including gold values) from an

original study centred on the Granny Smith gold mine Western Australia6 Carbonates from an original study in the Amadeus Daly River

Hamersley and McArthur Basins and Mt Isa Inlier7 General whole-rock geochemical samples from NGMA mapping in

the North Pilbara Western Australia8 General whole-rock geochemical samples from NGMA mapping in

the Lachlan Fold Belt New South Wales

Like earlier releases the data have been packaged into a series ofregional and thematic data sets These and the new prices are tabulatedbelow

A 33 per cent discount applies to purchasers of the completedatabase which is available for $39 600 Previous purchasers of thecomplete database may purchase copies of updates (approximately 3438analyses) for roughly $4610 (plus postage and handling charges) Large(gt500 samples) customised datasets can be prepared on demand for a feeof $2 per analyses (plus postage and handling charges) Smallercustomised datasets attract an extra extraction fee of $500 in addition tothe $2 per analyses charge Customised data sets can be selected for a1100 000 sheet area 1250 000 sheet area geological provincestratigraphic unit or by rock type

The data are available in the following relational database formatsOracle export fixed-length relational ASCII and comma-delimited relationalASCII For those who do not have relational databases a fourth optionmdashstandard comma-delimited (non-relational) ASCII formatmdashwill be offered

For further information phone Anthony Budd on +61 2 6249 9574or e-mail anthonybuddagsogovau Data can be ordered on-linefrom the web at httpwwwagsogovauinformationstructureisddatabaserockchemhtml

E X P A N D E D W H O L E - R O C KG E O C H E M I C A L D A T A B A S ER E L E A S E D

Data set New Total Pr iceanalyses analyses ($)

North Queensland 2 3525 7050Mt Isa Inlier Georgina Basin 1281 4020 8040Pine Creek Inlier mdash 2627 5254Lachlan Fold Belt 680 3413 6826South Australian Proterozoic 131 678 1356Western Australian Proterozoic 123 1506 3012Musgrave Block mdash 65 1312McArthur Basin 267 1747 3494Arunta Block 34 1184 2368Tennant Creek 3 1657 3314Yilgarn Block 284 4757 9514Pilbara 633 2312 4624Alkaline Rocks of Australia mdash 914 1828Broken Hill mdash 551 1102Total 3438 29 547 $59 094

Approximate numbers only are given here For exact numbers of samples and pricing please see the web site



PRODUCTnews

Compilation pixel image mapsTMI colour $200TMI greyscale $175Both TMI colour and greyscale $350

Pixel image maps 1 250 000 sheet area

Colour $150Greyscale $125Both colour and greyscale $250Digital (BIL) in colour $300Digital (BIL) in greyscale $250

Contour maps of semi-detailed data 1 250 000 and 1100 000

Dyeline $40Transparency $120

Depth to basement mapsTransparency $120

Interpreted geology mapsHard copy $50Digital version $150

Magnetic anomaly map of Australia15 million scale edn 3 $50

Since our last issue a number of geophysical products focusing on WesternAustralian terrain have been released including the following

Magnetic anomaly map of Western Australia at 125 million scaleData from several high-resolution surveys not included in the MagneticAnomaly Map of Australia have been incorporated in this map It has a highlevel of detail and complements the Geological Map of Western Australia Itretails at $50 plus postage and handling

Various digital data and line maps for the Stanley Youanmi and Robert1250 000 sheet areas have been released by AGSO and the Geological Surveyof Western Australia as part of the National Geoscience Mapping Accord

A merging of a 1999 government survey and a 1986 private-companysurvey has allowed the compilation of high-quality digital airborne magneticgamma-ray spectrometric and elevation model data for the Stanley 1250 00sheet area in the Capricorn Orogen region

Magnetic and gamma-ray spectrometric point located data are availableon a per kilometre basis Elevation model data are available for the 1999survey area only and are included in any data purchase The full dataset (58 600 km) costs $8500 a partial dataset 15 cents per kilometre plus a set-up charge of $250 (minimum order $400 for 1000 line-km) Grids with a cellsize of 80 metres can be purchased in 1100 000 sheets ($400) or for theentire 1250 000 sheet area ($2000) Total magnetic intensity images are alsoan option Radiometric images however have not been produced as yet

Digital airborne magnetic gamma-ray spectrometric and elevation modeldata for the Youanmi 1250 000 sheet area in the Southern Cross Provincealso are available Data has been compiled from a 1999 government surveyand four private-company surveys flown between 1987 and 1997 Except forthe full dataset (80 500 km) which costs $12 000 the options and productprices are the same as that listed above for the Stanley sheet

An outcome of the geophysical mapping program undertaken in theEastern Goldfields was the release in March of various digital data and linemaps for the Robert 1250 000 sheet area Since then high-quality colour andgreyscale airborne magnetic pixel maps have been added to the list ofproduct options

In May two lsquointerpreted geologyrsquo maps of the Barlee and Jackson 1250 000 sheet areas will be released The maps show Archaean geologyplus magnetic units in overlying cover rocks

For the price of pixel image maps for 1250 000 sheet areas andinterpreted geology maps see lsquoCheck these map pricesrsquo in this issue

Copies of maps can be bought from the AGSO Sales Centre bycompleting the enclosed order form by phoning +61 2 6249 9519 ore-mailing salesagsogovau For point located data and grids phoneRobert Reitsma on +61 2 6249 9210 or e-mail robertreitsmaagsogovau

LATEST RELEASESgeophysical data on the West

C H E C K T H E S E M A P P R I C E SWersquove been getting phone callsabout prices of our airbornegeophysical maps So here they areUse the list below as a yardstickGenerally the prices listed areconsistent from area to area acrossAustralia Postage and handlingcharges are not included in theprices shown below


A new CD-ROM available fromAGSO referred to as lsquoVulcan onWebBuryrsquo presents interactivegeohistory models of the VulcanSub-basin and adjacent AshmorePlatform and Londonderry High inthe Timor Sea

The models are based on acomprehensive geohistory analysisundertaken by AGSO and PaltechPty Ltd to constrain the thermal andhydrocarbon expulsion history ofthe region and to quantify thethermal effects of Late Tertiary fluidflow events They are generated bythe WinBury 1D burial and thermalgeohistory modelling softwarewhich incorporates a simplifiedtransient heat pulse function tosimulate the thermal effect of hotfluid flow events

The steady state and transientthermal history models are con-strained by conventional vitrinitereflectance (VR) and limitedfluorescence data (VRF FAMM)together with apatite fission trackanalysis (AFTA) and fluid inclusionpalaeo-temperature data

The burial and thermal modelsare applied to two source units toconstrain the timing and relativevolumes of expelled liquidgaseoushydrocarbons Oxfordian marineshales of the Lower VulcanFormation and Lower-MiddleJurassic fluvio-deltaic shales andcoaly shales of the underlyingPlover Formation New kerogenkinetic data for these source faciesare used in the expulsion models

Contents of CDThe modelling package is dividedinto the following six sections

Wells This section presentsindividual geohistory models for 44wells and 18 depocentre sitesconstrained by sequenceinterpretation of AGSOrsquos high-resolution 1995 VTT Vulcan Sub-basin seismic survey Geohistorytemperature heatflow tectonicsubsidence maturity source rockand hydrocarbon generation plotscan be interactively selected for eachwell or depocentre site (figure 1a)

X-sections In this sectionwell-to-well cross-section geohistorymodels are displayed Temperaturematurity and hydrocarbonexpulsion overlays can beinteractively displayed on eachsection The cross-sections can beanimated through time for user-


specified time periodsmdashfor example 200 Ma to present day (figure 1b)Multi-well Multiple-well geohistory curves and basin-wide maps for the

modelled source units are found in this section Tectonic subsidence heatflowtemperature maturity and hydrocarbon generation and expulsion time-plotsand contoured maps can be interactively displayed including animationsthrough time and rate maps for user-specified time periods (figure 1c)

Seismic Interpreted seismic lines showing the regional structural settingof modelled wells and depocentre sites are found in this section Geohistorymodels for wells and depocentre sites also can be interactively selected fromthe seismic displays

Petroleum systems This section presents a schematic summary of theactive petroleum systems in the Vulcan Sub-basin and summarises therelative timing of modelled oilgas expulsion and major structural events(compression extension and reactivation)

Report This text-based section presents full details of the geohistoryanalysis including a discussion of charge history and implications forhydrocarbon prospectivity

Users can easily select multiple views and options within each sectionvia point and click buttons and drop-down windows No prior knowledge ofthe WinBury modelling software is needed A lsquohelp buttonrsquo providesadditional information to assist the user at any stage

Temporary modifications to existing data can bemade or new data can be added in the well models(eg stratigraphic unitsdepthsage maturity andfission track data alternative palaeo-bathymetryheatflow kerogen types etc) Thecorresponding maturity generation and expulsionmodels based on these changes can be viewed andprinted directly from the screen views but will notbe saved on exit from the well Current users ofWinBury modelling software can copy well datafiles from this package to their WinBury workingdirectories

Vulcan Sub-basin geohistory models on CD

Figure 1 Screen captures of Vulcan on WebBury showing well base map a Paqualin-1maturity plot b Cross-section Keeling-Octavius showing present-day oil (dark brown)and gas (red) expulsion c Maturity map of the Lower Vulcan Formation source unit atthe onset of oil expulsion (Late Eocene ~35 Ma)

P R O D U C T N E W S

1a

1b

1c



What models showThe geohistory models suggest thathydrocarbon expulsion in the VulcanSub-basin was restricted to Oxfordian-Kimmeridgian source rocks (LowerVulcan Formation) within the Swan andPaqualin grabens together with minorlate gas expulsion from the deepestportion of the Cartier Trough Due tothe high activation energies of thekerogens relatively high temperatures(145ndash160ordmC) are required to generatehydrocarbons from this source

Generation of hydrocarbonsoccurred mainly in the Late Jurassic toEarly Cretaceous but the main phase ofoil expulsion was compaction-drivenand did not occur until the mid-lateTertiary In contrast the main phase ofgas expulsion took place in the LateJurassic to Early Cretaceous coincidentwith the main phase of gas generationLater phases of compaction-driven gasexpulsion occurred in the early Tertiaryand Pliocene to Recent

Expulsion from shales and coalyshales within the Lower-Middle JurassicPlover Formation may also have occurredif the immature organic-rich faciesintersected in the Skua Trough extendwestward beneath the Swan andPaqualin Grabens and the Cartier Trough

The limited area distribution ofexpelled oil predicted by the modelssuggest that long migration pathways(longer than hitherto believed) arerequired to charge traps remote from theSwan and Paqualin source kitchens

The models indicate that lsquosalinersquo hot-flush events while important inunderstanding the fill-spill history ofshallow trap structures do not affect thetiming of generation and expulsion inthe depocentres However lsquonon-salinersquohot-flush events presumably relating tohydrocarbon charge may be responsiblefor elevated heatflows in shallow drilledstructures As a consequence mostexploration wells are not trulyrepresentative of the thermal regime ofnearby source kitchens

Usage requirementsThe package requires 30 Mb hard discspace Windows 9598 or NT operatingsystems and a standard web browser(Internet Explorer or NetscapeNavigator) The CD-ROM with theofficial title of Record 199940VulcanSub-basin Geohistory Modelling isavailable from the AGSO Sales Centrefor $350 plus postage and handling

For further information contact John Kennard on +61 2 6249 9204 or e-mail johnkennardagsogovau orphone Ian Deighton Paltech Pty Ltdon +61 2 6492 7201 or e-mailpaltechacrnetau

I N C R E D I B L E V A L U E F O RN O R T H Q U E E N S L A N D S T R E A M S E D I M E N TG E O C H E M I C A L D A T A

If you are looking for geochemical data on north Queensland thesetwo AGSO products should interest you new data on the Croydongoldfield area and AGSOrsquos entire north Queensland stream sedimentgeochemical data set

Croydon region982 samples analysed for Ag As Ba Be Bi Ce Co Cr Cu Fe Li MnMo Nb Ni Pb Rb Sn Th Ti U W Y and Zn

This is the first release of stream sediment geochemical datacovering most of the outcropping portion of the MesoproterozoicCroydon Province in north Queensland The province contains thesignificant Croydon goldfield The ASCII data filesmdashcontaining samplenumber sample site location (AMG in metres or latitudelongitude indegrees and decimal degrees) and element valuesmdashare available as MS-DOS files on 144 Mb disks The price for this data is $1000

North Queensland data set 8752 samples analysed for some or all of the following elements AgAs Au Ba Be Bi Cd Ce Co Cr Cu Fe Ga Ge Hf La Li Mn MoNb Ni P Pb Pd Pt Rb Sb Sc Se Sn Ta Th Ti Tl U W Y Zn and Zr

This is the single largest publicly funded stream sedimentgeochemical data set available in Australia The data set covers roughly80 thousand square kilometres of Proterozoic and Phanerozoic northQueensland and contains 235 914 analyses It has a replacement valueof more than $2 million

The ASCII data filesmdashcontaining sample number sample sitelocation (AMG in metres or latitudelongitude in degrees and decimaldegrees) and element valuesmdashare available as MS-DOS files on CDThe CD includes PDF files of accompanying data records and atlases ofcoloured image maps

The data (less the new Croydon data set) and associated reportsand atlases previously sold in nine separate data sets for a total ofmore than $36 500 With the newarrangements and at an incredibleprice of $8750 small explorers areoffered greater access to aninvaluable exploration data setand simultaneously streamlinedata handling in AGSOEventually when AGSO hasmoved to full e-commercecapability these data will beavailable on-line and clientswill be able to select andpurchase on a pro-rata basisjust the data required

For more informationphone John Bain on +61 2 6249 9282 or e-mailjohnbainagsogovauProducts will beavailable in June fromthe AGSO Sales Centreby phoning +61 2 6249 9519 or e-mailingsalesagsogovau




This 15 million scale map normallycosts you $1995 plus $5 postageand handling While stocks lastwersquoll let you have this lsquoElevationimage of Australiarsquo map for just$895 plus $4 postage and handlingThatrsquos roughly 50 per cent off theoriginal price

Major lakes river systems andother large-scale and subtle featuresof Australiarsquos topography are easilyrecognised on this gradient-enhanced colour map The mapwill interest a wide range of peopleincluding those wanting copies forland-use education and recreationpurposes

Donrsquot miss out on this genuinebargain Order your copy byphoning Dave Harris on +61 2 6249 9333 or e-mailing the AGSO Sales Centre onsalesagsogovau

bargain

Numerous diagrams and mapsappear throughout this 248-pagevolume An A1-sized colour chart oftransects of the Australiancontinental margin is included in acover sleeve

Copies of AGSO Journal 1756can be bought from the SalesCentre for $80 (plus postage andhandling) by phoning +61 2 6249 9519 or e-mailing salesagsogovau

The AJES is published byBlackwell Science for theGeological Society of AustraliaAGSO is responsible for onethematic issue this year

L A S T I S S U E B E F O R E J O U R N A LA M A L G A M A T I O N

The final issue of the AGSO Journal of Australian Geology and Geophysicshas just been printed From now on papers destined for the AGSO Journalwill be published in the Australian Journal of Earth Sciences (AJES)

Eighteen papers were included in the final issue (volume 17 number56) Unlike earlier issues this one does not focus on a single theme Insteadit features papers on Australian petroleum exploration environmentalimpacts in Australiarsquos coastal-marine zone and Antarctica in the Cainozoic Aprecis of article titles followsbull Seabed mapping using multi-beam swath-mapping systemsbull Architecture and evolution of the Australian continental marginbull Where is Australiarsquos petroleum and how long will it lastbull Undiscovered hydrocarbon resources of the Bowen and Surat Basinsbull The problem of inconsistency between thermal maturity indicators used

for petroleum explorationbull Sequence stratigraphy concepts and application to petroleum explorationbull Quaternary Antarctic ice-sheet fluctuations and southern ocean

paleoceanographybull The late Cainozoic East Antarctic ice sheetbull Paleocene-Eocene biostratigraphy and paleoenvironment of East

Antarcticabull Glacial-interglacial paleoceanography from Australian margin sedimentsbull Sedimentndashwater interaction in Australian coastal environmentsbull Use of sediments to assess environmental impact on a large coastal

catchment (Hawkesbury River)bull Aluminium and iron in acid runoff from acid sulphate soils (Richmond River)bull Impact of runoff on nutrient patterns in northern Port

Phillip Baybull Flushing of Australian estuaries coastal lakes and embaymentsbull Microbial nutrient cycling in seagrass sedimentsbull Contaminant dynamics in offchannel embayments of

Port Jacksonbull Methane anomalies in seawaters of the Ragay Gulf Philippines

What a bargain


A U S G E O N e w sApril 2000 issue no 57

Editor Julie Wissmann

Graphic Designer Karin Weiss

Photographer Brett Ellis

This publication is issued free ofcharge It is published six times a yearby the Australian Geological SurveyOrganisation

The views expressed in AUSGEONews are not necessarily those ofAGSO or the editor and should not bequoted as such Every care is taken toreproduce articles as accurately aspossible but AGSO accepts noresponsibility for errors omissions orinaccuracies

copy Commonwealth of Australia 2000

ISSN 1035-9338

Printed in Canberra by National Capital Printing

Australian Geological SurveyOrganisationGPO Box 378Canberra ACT 2601Australia

cnr Jerrabomberra Ave amp Hindmarsh DrSymonston ACT 2609Australia

Internet wwwagsogovau

Chief Executive OfficerDr Neil Williams

SubscriptionsDave HarrisPhone +61 2 6249 9333Fax +61 2 6249 9982E-mail daveharrisagsogovau

AGSO productsJudy Kley Chris ThompsonPhone +61 2 6249 9519Fax +61 2 6249 9982E-mail salesagsogovau

Editorial enquiriesJulie WissmannPhone +61 2 6249 9249Fax +61 2 6249 9984E-mail juliewissmannagsogovau

AUSGEO News is available on the web at wwwagsogovauinformationausgeonews

Minerals Open Days3Orientation change gives Broken Hill new prospects 3

Mineral provinces crustal geometry subject of major seismic research 4

Yilgarn mapping provides golden opportunity 6

Gravity properly planned is a precision tool 8

Mineral resources and advice activities AGSOrsquos role extended 15

FeaturesSurges blackouts but glowing skies as sun activity peaks 9

Seabed images off south-east Australia a first 22

Picture builds for Australiarsquos eastern limits 24

Speakers10Big earthquake rouses Taiwan 10

Rabaul volcanoes fire 30-year passion 12

Around the divisions 18

Workshops and seminars 26

Events calendar28

Product news29

Lord Howe Island in sight AGSO scientists arebusy mapping Australiarsquos eastern seabedjurisdiction Photo taken from the deck of Frenchresearch vessel LrsquoAtalante See article page 22

Photo Peter Hill leader of the AUSTREA-1 cruise

CONTENTS















OR

IEN

TATI






Curnamona province

























MINERAL PROVINCES




















































































Ms Murray











Continued page 14





SURGESBLACKOUTS

















0

50

100

150

200

1986 2006


1988 1990 1992 1994 1996 1998 2000 2002 2004


SS



SPEAKERS






















BIG EARTHQUA







S P E A K E R S









roughly 11 000 km

rousesTaiwan


UAKE
















S P E A K E R S



















S P E A K E R S



































































































DID YOUknow

















































O


























1st



















Seabed images



1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain















OR

IEN

TATI






Curnamona province

























MINERAL PROVINCES




















































































Ms Murray











Continued page 14





SURGESBLACKOUTS

















0

50

100

150

200

1986 2006


1988 1990 1992 1994 1996 1998 2000 2002 2004


SS



SPEAKERS






















BIG EARTHQUA







S P E A K E R S









roughly 11 000 km

rousesTaiwan


UAKE
















S P E A K E R S



















S P E A K E R S



































































































DID YOUknow

















































O


























1st



















Seabed images



1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain























MINERAL PROVINCES




















































































Ms Murray











Continued page 14





SURGESBLACKOUTS

















0

50

100

150

200

1986 2006


1988 1990 1992 1994 1996 1998 2000 2002 2004


SS



SPEAKERS






















BIG EARTHQUA







S P E A K E R S









roughly 11 000 km

rousesTaiwan


UAKE
















S P E A K E R S



















S P E A K E R S



































































































DID YOUknow

















































O


























1st



















Seabed images



1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain




















































































Ms Murray











Continued page 14





SURGESBLACKOUTS

















0

50

100

150

200

1986 2006


1988 1990 1992 1994 1996 1998 2000 2002 2004


SS



SPEAKERS






















BIG EARTHQUA







S P E A K E R S









roughly 11 000 km

rousesTaiwan


UAKE
















S P E A K E R S



















S P E A K E R S



































































































DID YOUknow

















































O


























1st



















Seabed images



1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain



SURGESBLACKOUTS

















0

50

100

150

200

1986 2006


1988 1990 1992 1994 1996 1998 2000 2002 2004


SS



SPEAKERS






















BIG EARTHQUA







S P E A K E R S









roughly 11 000 km

rousesTaiwan


UAKE
















S P E A K E R S



















S P E A K E R S



































































































DID YOUknow

















































O


























1st



















Seabed images



1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain


SPEAKERS






















BIG EARTHQUA







S P E A K E R S









roughly 11 000 km

rousesTaiwan


UAKE
















S P E A K E R S



















S P E A K E R S



































































































DID YOUknow

















































O


























1st



















Seabed images



1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain







S P E A K E R S









roughly 11 000 km

rousesTaiwan


UAKE
















S P E A K E R S



















S P E A K E R S



































































































DID YOUknow

















































O


























1st



















Seabed images



1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain
















S P E A K E R S



















S P E A K E R S



































































































DID YOUknow

















































O


























1st



















Seabed images



1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain



















S P E A K E R S



































































































DID YOUknow

















































O


























1st



















Seabed images



1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain



































































































DID YOUknow

















































O


























1st



















Seabed images



1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain

















































O


























1st



















Seabed images



1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain


























1st



















Seabed images



1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain


1st


O C E A N G O I N G


























Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain







Picture builds for









bathymetric data


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain


O C E A N G O I N G





























WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain














WORKSHOPSseminars













































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain
































29 April to 8 May



phone +61 2 6205 0588

fax +61 2 6205 0638


AGSO Open Day

7 May



phone +61 2 6249 9263

fax +61 2 6249 9990




7 to 10 May



phone +61 2 6247 0960

fax +61 2 6247 0548



29 to 31 May




phone +61 2 6249 9727



11 to 15 June

Calgary Canada


phone 0011 1 403 218 2000

fax 0015 1 403 218 2002




















PRODUCTnews








































1a

1b

1c

























bargain













What a bargain



PRODUCTnews








































1a

1b

1c

























bargain













What a bargain




















1a

1b

1c

























bargain













What a bargain

























bargain













What a bargain


some new thoughts ocean boundariesocean boundaries in agso’s sights april 2000 issue no. 57 pp...

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