indonesian journal on geoscience v1 n1 april/may 2014
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Gold Phytomining: A New Idea
for Environmental Sustainability in Indonesia
B D K1andC A2
1University of Mataram, Indonesia; International Research Centre for Managementof Degraded and Mining Lands (IRC-MEDMIND)
2Massey University, New Zealand; International Research Centre for Managementof Degraded and Mining Lands (IRC-MEDMIND)
Corresponding author: [email protected] received: December 3, 2012, revised: December 13, 2013, approved: March 20, 2014
Abstract- New technology isneededto protect the safety andhealth of communitiesandthe environment at ASGMlocations inIndonesia. Thistechnology mustbesimple, cheap, easyto operate, andnancially rewarding. A provenoption that shouldbepromoted isphytoextraction, afarming activity that could develop agriculture asan alternativelivelihood inASGM areas. This isa technology where plants areusedto extract metals from waste rock, soil, orwater. These metals can berecoveredfrom the plant in its pure form, then be sold orrecycled. Gold phytoextrac-tion isacommercially available technology, while an international research hasshown that phytoextraction willalso work for mercury. In the context of this idea, tailings would be contained in farming areas and croppedusing phytoextraction technology. Gold andmercurywouldbeextracted inthe crops, with the remaining mercuryburdenof the tailingsbecoming adsorbedto soil constituents. The system would be nancially rewarding to gold
farmers. The economic value of thisscenario could facilitatethe clean-up and management of mercurypollution,reducing the movement of mercury from tailings into soil, water, and plants, thereby mitigating environmentalandhuman risk in the mining areas. The goal of the described research isto promote agriculture as an alterna-tive livelihood in ASGM areas. The gold value of the phyto remediation crop should provideacash incentiveto artisanal farmerswho develop this new agricultural enterprise. The benets will be social, environmental, andeconomic, as opportunities for education, employment, new business, the containment of toxic mercury, foodsafety and security, and revenue are all realized.
Keywords: gold, phytomining, tailing, new business, phytoremediation, agriculture
Introduction
Gold is a precious metal on earth that millionsof people depend their life on this metal. Despite
of the prosperity target, beneath it many issues are
related to gold mining, such as an environmental
issue. However, science is always developing
to cope with the issues, in order to minimize
the environmental impact and targeting people
prosperity.
Modern gold mining operations conducted in
Indonesia by multinational mining companies,
like in most countries, are regulated and efcient.
Mined ore is leached with cyanide through a
Carbon In Pulp (CIP), Carbon In Leach (CIL),
or heap leach circuit to extract gold from the
rock in the majority of these operations. Plansare generally in place to contain contaminated
waste, and to rehabilitate the mining area once
an operation nishes.
Past mining operations, however, environ-
mental risk in the form of chemicals, heavy met-
als, and sediment discharged from waste areas
and interact with ecosystems is present. Runoff
and leakage from tailings and waste rock can
pollute streams owing out of the mining area,
causing widespread damage downstream. This
has a direct affect on communities and people
Indonesian Journal on Geoscience Vol. 1 No. 1 April 2014: 1-7
INDONESIAN JOURNAL ON GEOSCIENCEGeological Agency
Ministry of Energy and Mineral Resources
Journal homepage: hp://ijog.bgl.esdm.go.idISSN 2355-9314 (Print), e-ISSN 2355-9306 (Online)
IJOG/JGI (Jurnal Geologi Indonesia) - Acredited by LIPI No. 547/AU2/P2MI-LIPI/06/2013, valid 21 June 2013 - 21 June 2016
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who depend directly on goods and services
provided by ecosystems, and the quality of, and
their access to, natural resources. An increase
in wealth generated by commodities can be
offseted by a decrease in wealth attributed tonatural capital destroyed through the commod-
ity production cycle (specically the average
persons ecosystem). The result is a population
that is poorer, despite an apparent increase in
gross domestic product. Any rise in GDP in this
context is at the expense of an average persons
natural asset.
Contamination at a historic mining site is not
necessarily bad. It is the scenario of this con-
tamination interacting with soil, plants, animals,
and people that must be mitigated or managed.
Professional assessment is therefore essential
to diagnose environmental risk, and to dene
a remediation plan. Some of the worst mining
pollution around the world that is seen today, is
due to historic operations where no environmen-
tal risk assessment or rehabilitation procedures
were put in place upon the conclusion of mining
operations.
The category of mining that causes the greatest
level of environment damage in Indonesia is ar-tisanal mining. This term describes an informal
and unregulated system of small-scale mining
prevalent in many of the worlds poorest countries
and communities. Artisanal miners do not make
large prots; they strive to make sufcient money
to support their immediate family. Many metals
and minerals are mined using artisanal methods,
but high value commodities such as precious
metals and gemstones provide the greatest return.
In the context of gold mining, the term artisanal
and small-scale gold mining (ASGM) is used todescribe this practice.
What Is Phytomining?
Phytomining is the production of a crop of a
metal by growing high-biomass plants that accu-
mulate high metal concentrations (Brooks et al.,
1998). A phytomining operation would therefore
entail planting a crop over a low-grade ore body or
mineralized soil, implementing appropriate land
management techniques to ensure metal uptake,
and then harvesting and incinerating the biomass
to produce a commercial bio-ore (Brooks et
al., 1998).
Phytomining offers several advantages over
conventional mining (Brooks et al., 1998), which
include (a) the possibility of exploiting ore bod-ies or mineralized soils otherwise uneconomic to
develop, (b) its environmental impact is minimal
when compared with the erosion caused by open-
cut mining, (c) the operation would be visibly
indistinguishable from a commercial farming op-
eration, (d) a bio-ore has a higher metal content
than a conventional ore and thus needs less space
for storage, and (e) because of its low sulphur
content, smelting a bio-ore does not contribute
signicantly to acid rain.
Phytomining is actually a subset of a larger
eld of research known as phytoextraction, the
process of using plants to benecially absorb
mineral species from soils, sediments, and
groundwater. It involves the cultivation of tolerant
plans that concentrate soil contaminants in their
above-ground tissues. At the end of the growth
period, plant biomass is harvested, dried or in-
cinerated, and the contaminant-enriched material
is deposited in a special dump or added into a
smelter. The distinction between phytoextractionand phytomining is that in phytomining, the metal
accumulated by plants is sufciently valuable to
economically justify the recovery of this metal in
pure form. To date, phytomining has been trialled,
to varying degrees of success, for nickel and gold.
The more common application of phytoextrac-
tion is phytoremediation, where non-naturally
occurring contaminants are recovered for disposal
or reuse. Phytostabilisation is used to describe a
land-management technique where contaminant
species are immobilized in situvia plant action.In contrast to phytoremediation, the objective in
phytomining is to recover a mineral (metallic)
commodity for commercial gain. Consequently,
phytomining almost always refers to the recovery
of heavy metals.
Phytoremediation and phytomining are being
developed as commercially viable environmental
technologies by many groups around the world.
Massey University has an international reputation
for conducting novel and important phytoreme-
diation research at historic and active mine sites
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in New Zealand, Australia, Fiji, China, USA,
Mexico, Brazil, and South Africa. Massey Uni-
versity scientists have many years of experience
in the design and application of phytoremedia-
tion projects. A New Zealand company that hasa research relationship with Massey University
has proprietary expertise in the processing of
plant biomass to recover metals, including gold.
Research in New Zealand has investigated a
system where gold and mercury are recovered by
the same crop of plants from soil or tailings at an
ASGM location elevated in both of these metals
(Moreno et al., 2005).
How Does Phytomining Work?Phytomining works through phytoextraction,
thus hyperaccumulator plants. Many extensively
studies on hyperaccumulators have been done
by researchers including using Thlaspi sp. to hy-
peraccumulate Cd, Ni, Pb, and Zn. For example,
Thalspi caerulescens could remove as high as
60 kg Zn/ha and 8.4 kg Cd/ha (Robinson et al.,
1998), due to specic rooting strategy and a high
uptake rate resulting from the existence in this
population of Cd-specic transport channels or
carriers in the root membrane (Schwartz et al.,2003).
Hyperaccumulators efciently extract metals
from the metalliferous soils and then translocate
metals to above ground tissues. After sufcient
growth, plant is harvested and left for drying.
Dried plant material is reduced to an ash with or
without energy recovery, which is further treated
by roasting, sintering, or smelting methods, whichallow the metals in an ash or ore to be recovered
according to conventional metal rening meth-
ods such as acid dissolution and electrowinning
(Figure 1) (Robinson et al., 1999).
Plants have shown several response patterns
to the presence of high metal concentration in
the soils. Most are sensitive to high metal con-
centrations and others have developed resistance,
tolerance, and accumulate them in roots and
above ground tissues, such as shoot, ower, stem,and leaves. The current denition of a hyperac-
cumulator is a plant that is able to accumulate
metal to a concentration that is 100 times greater
than normal plants growing in the same envi-
ronment. Sheoran et al.(2009) stated that metal
hyperaccumulation was a complex and rare phe-
nomenon that occurs in plant species with high
metal uptake capacity. The mechanism of metal
hyperaccumulation involves several steps (Figure
2), which are:
1. solubilization of metal from the soil matrix,2. root absorption and transport to shoot, and
3. distribution, detoxication, and sequestrian
of metal ion.
Figure 1. Integrated process for bioharvesting of metals by phytomining.
Potential of phytomining of areasunable to be exploited by conventionalmethods: Metaliferous soils Low grade ore Mill tailings
Reclaimed soil product Small volume of bio-ore
Smelt metal
Bioxtraction/phytoextraction ofmetal for commercial gain:CroppingHarvestingDrying
Ashign
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Method Gold Hytomining
Theory and Practice
A review of pyhtomining (Sheoran et al.,
2009) has stated that gold has been suggested as
a potential candidate for phytomining. Tailing
areas usually contains residual gold in very low
concentrations, whereas the relatively high con-
centrations found in heap leach pads and waste
dumps. Plants normally do not accumulate gold;
the metal must be made soluble before uptake can
occur. The residual gold could be extracted using
induced hyperaccumulation if the substrates were
amenable to plant growth. The concentration of
gold that can be induced into a plant is dependant
upon the gold concentration in the soil on which
the plant is growing.
Anderson et al. (2005) has showed that ap-proximately 2 mg of gold per kg of soil is needed
by considering a soil prole of 20 cm depth to
achieve 100 mg/kg of plant dry mass. Many re-
searches have shown that uptake of gold can be
induced using lixiviants such as sodium cyanide,
thiocyanate, thiosulphates. In an induced hyperac-
cumulation operation of gold, the geochemistry of
the substrate (pH, Eh, and chemical form of gold)
will play a rule of the solubilizing agent necessary
to affect the uptake of the precious metal. For
low-pH sulde tailings, gold is made soluble by
thiocyanate, and for high-pH unoxidised sulde
tailings gold is soluble with thiosulphate (Ander-
son et al., 1999).
Result and Discussions
In the last decade, there have been many re-ports of gold accumulation by plants, in particular
Figure 2. General mechanism of metal hyperaccumulation by plants.
Root absorption and compartmentation
Transporters
Channels or membrane pumpCytoplasmic chelators
Bio-activation ofthe metals inthe rhizosphere
H+ secretion
Organic acids
Enzymes. Root microbe interaction
Xylem transport
Symplast loading
Ion exchange etc.
Distribution, Detoxificationand Sequestration(Cell wall binding,vacuole sequestration,cytoplasmic chelation)
Total metal fractionin soil solution
availablepotentiallyavailable
unavailable
M2+
M2+
M2+
M2+
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trees. Work conducted over 30 years in Canada
showed that common conifers could accumulate
up to 0.02 mg/kg gold over gold mineralization.
In addition, Dunn (1995) reported a background
level of gold in plants of 0.0002 mg/kg dryweight, although this author stated that values up
to 0.1 mg/kg could be found.
Hyperaccumulation of gold was dened in
1998 as accumulation greater than 1 mg/kg, this
limit being based upon a normal gold concentra-
tion in plants of only 0.01 mg/kg (Anderson et al.,
1998a,b). Anderson et al. (1998b) induced Indian
mustard (B. juncea) with ammonium thiocyanate
at the rate of 0, 80, 160, 320, and 640 mg/kg dry
substrate weight in pots containing an articial
5 mg/kg nely disseminated gold rich material,
analogous to a natural, oxidized, nonsuldic ores.
Hyper-accumulation of Au was achieved above
a thiocyanate treatment level of 160 mg/kg and
yielded up to 57 mg/kg Au.
A similar experiment withB. juncea grown in
a medium containing 5 mg/kg Au prepared from
nely powdered native Au (44 lm) and treated
with ammonium thiocyanate at an application
rate of 250 mg/kg also supported the results (An-
derson et al., 1999b). Anderson et al. (2005) alsoestimated that a harvested crop of 10,000 kg/ha
biomass (dry) with gold concentration of 100 mg/
kg, which would yield 1 kg of gold/hectare could
be economically viable. They experimented with
B. juncea (Indian mustard) and Z. mays (corn)
induced with sodium cyanide and thiocyanate
grown on oxidized ore pile containing 0.6 mg/
kg gold. They reported thatB. junceashowed the
best ability to concentrate gold giving an average
of 39 mg/kg after sodium cyanide treatment. The
highest individual gold concentration determinedthrough an analysis of selected biomass was 63
g/kg (NaCN treatment of B. juncea) (Anderson
et al., 2005).
Gold phytomining has also been reported by
Msuya et al.(2000) with ve root crops (carrot,
red beet, onion, and two cultivars of radish) grown
in articial substrate consisting of 3.8 mg/kg gold,
and concluded that carrot roots yielded 0.779
Au kg/ha, worth US$ 840; by adding chelaters
ammonium thiocyanate and thiosulphate carrot
roots yielded 1.45 Au kg/ha of nal worth US$
7,550. Lamb et al. (2001) induced plant species
B. juncea, B. coddii, and Chicory with thiocyanate
and cyanide solutions to determine gold concen-
tration in different parts of plants. The ashed plant
material was dissolved in 2 M HCl, followed bysolvent extraction of the gold into solvent methyl
isobutyl ketone (MIBK). Addition of the reduc-
ing agent sodium borohydride to the organic
layer caused a formation of black precipitate at
the boundary between the two layers and heat-
ing this precipitate to 800oC caused formation of
metallic gold. Gold concentrations ranged from
negligible in the leaves ofB. coddii induced with
thiocyanate, to 326 mg/kg Au dried biomass in
the leaves ofB. juncea induced with cyanide. The
chemical additives KI, KBr, NaS
2O
3, and NaSCN
were also used with theB. juncea and Chicory.
The results showed varying degrees of hyper-
accumulation with all chemical treatments. Cya-
nide again gave the best results with 164 mg/kg
Au dried biomass measured in the Chicory plant.
NaS2O
3, KI, and NaSCN gave maximum results
of 51, 41, and 31 mg/kg Au dried biomass, re-
spectively. Gardea-Torresdey et al. (2005) have
reported that C. linearis (desert willow - a com-
mon inhabitant of Mexican Chihuahuan Desert)is a potential plant for gold phytomining. Desert
willow seedlings grew very well in the presence
of NH4SCN concentration lower than 1x10-4
mol/ L. It has been reported that shoot elongation
was also not affected by either the Au or NH4SCN
concentrations. In addition when using NH4SCN
at a concentration of 10-4mol/L with 5 mg Au/L,
Au uptake was enhanced by approximately 595,
396, and 467 percentages in roots, stems, and
leaves, respectively, compared with gold uptake
by plants grown in only 5 mg Au/L. Their stud-ies also showed that this plant produced Au (0)
nanoparticles with an approximate radius of 0.55
nm. Mohan (2005) recommended phytomining
to be a novel cost-effective technology to extract
gold from larger residual dumps (mounds of tail-
ings) and from low-grade ores at KGF (Kolar
Gold Fields) in Karnataka. Continuous conven-
tional mining has depleted the level of gold up
to 3 mg/kg, hence union government closed the
mine. Committees worked over closed mine,
proposed a scheme to recover gold from larger
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residual dumps (mounds of tailings) that had ac-
cumulated over the years. Studies have shown
that there are about 33 million tonnes of dumps
accumulated over the years with a concentration
of gold 0.7 - 0.8 mg/kg, which may be a sourceof 24,000 kg of gold.
Economic Viability of Gold Phytomining
The general target for a gold phytomining
operation is to yield 0.5 kg of gold from ever
hectare (unit area) of operation. This gold yield is
possible through harvesting 5 t/ha of dry biomass
containing an average gold concentration of 100
mg/kg (this unit is the same as g/t). At a gold price
of US$ 1,500 an ounce, 0.5 kg of gold is worth
US$ 24,113. The modelled costs to grow, tend,
treat, and process 5 tonnes of plant material are
approximately US$15,000. This generates a gross
prot of just over US$ 9,000 per hectare. Increased
biomass per hectare will lead to an increased yield
of gold and increased gross prot. An average gold
concentration in the biomass above or below 100
mg/kg will also change the expected gross prot.
The limiting factor for the gold concentration
in plants is the total gold concentration in the soil
(tailings or waste rock), and the fraction of this totalgold that can be made available for plant uptake.
There must be a gold concentration in the soil of 0.5
g/t or greater for a pre-feasibility study to be war-
ranted. The cash value of the crop is not the only
positive economic parameter. The gold phytomin-
ing process will also remove certain contaminants
from the soil (e.g. copper, arsenic, mercury) or
will degrade contaminants within the plant root
zone (cyanide). Several years of successive gold
cropping will reduce contaminant levels, reduc-
ing environmental risk and remediating the site.The gold value of the gold crop will subsidize or
outright pay for complete site remediation.
The Projects
An early research of gold phytomining in
Sekotong of West Lombok District was con-
ducted in 2011. A plot of four different species
which were cassava, corn (Zea mays),Brassica
juncea, and Sunower directly planted on cya-
nidation tailing (Figure 3). The Au concentration
on the cyanidation tailings was in the range of
0.58 - 6.58 ppm. The source of material used in
cyanidation process is from amalgamation tail-
ings, and the Au concentration of amalgamation
tailings is between 1.75 - 14.71 ppm.
After three months of growing, it showed that
corn and cassava survived in the extreme growth
medium. A week before harvesting, the plants was
treated by CN and fresh/dry biomass collected
for further laboratory analysis. The samples were
analyzed in an analytical laboratory of Mataram
University, and the results are showed in Table 1.The results indicate that there was a high prospect
of using these local plants for gold phytomining.
Andersons current study has showed that
gold phytomining is being actively developed
in Mexico, a country with a long history of gold
mining and a legacy of contaminated mining sites.
Many historic mining locations have tailings with
a gold grade in excess of 1 g/t. Gold phytomining
eld trials have been conducted in Mexico for a
number of years. These trials have involved col-
Table 1. Au Concentration on Plant Samples
Figure 3. Four spesies growth at cyanidation tailings from
ASGM Sekotong, West Lombok, Indonesia.
Time ofharvesting
Sample type Au (ppm)
1 Dry corn leaves 3.40
1 Dry brassica 1.94
1 Dry cassava leaves 1.96
2 Fresh cassava leaves 2.17
2 Dry cassava leaves 1.493 Fresh cassava leaves 1.80
3 Fresh cassava leaves 1.41
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laboration between the Universidad Autonoma
de Sinaloa (Mexico) and the New Zealand bio-
mass processing company, Tiaki International
Ltd. (with Anderson).
In early 2012 a trial was conducted at a minesite with surface tailings of approximately 3
ha at an average gold grade in excess of 1 g/t.
Sunowers were grown on this mine waste and
treated to induce gold uptake. The average gold
concentration in the plant material at harvest
was greater than 20 g/t with the maximum gold
concentration in excess of 30 g/t. This biomass is
currently being processed. However, taking the
international market value of gold in 2012 into
account, the observed gold concentration in the
plants is considered to be economic. This aver-age gold concentration was not considered to be
optimal. Future trials will seek to considerably
increase the gold concentration accumulated by
the eld- harvested plants.
Conclusion
Gold phyotmining is a promising technology
to be used on gold tailings in Indonesia. The
success and sustainability of gold phytomining
will require a balance between the economic
incentives to recover this precious metal and
environmental sustainability in the eld.
Acknowledgment
The paper has been presented in MGEI meet-
ing 2012, carried out in Malang, East Java.
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INDONESIAN JOURNAL ON GEOSCIENCEGeological Agency
Ministry of Energy and Mineral Resources
Journal homepage: hp://ijog.bgl.esdm.go.idISSN 2355-9314 (Print), e-ISSN 2355-9306 (Online)
Indonesian Journal on Geoscience Vol. 1 No. 1 April 2014: 9-19
Some Key Features and Possible Origin of the Metamorphic
Rock-Hosted Gold Mineralization in Buru Island, Indonesia
A I1, S P2, H. G H3, F I3, E4,F4, M4, andI S5
1Geological Engineering Department, Gadjah Mada University, Yogyakarta2PT. AGC Indonesia, Jakarta
3Geological Engineering Department, STTNas Yogyakarta4Center for Geological Resources, Geological Agency, Bandung
5Geotechnology Research Centre, LIPI, Bandung
*Corresponding author: [email protected] received: February 10, 2014, revised: March 10, 2014, approved: March 28, 2014
Abstract - This paper discusses characteristics of some key features of the primary Buru gold deposit as a tool for a
better understanding of the deposit genesis. Currently, about 105,000 artisanal and small-scale gold miners (ASGM)
are operating in two main localities, i.e.Gogorea and Gunung Botak by digging pits/shafts following gold-bearing
quartz vein orientation. The gold extraction uses mercury (amalgamation) and cyanide processing. The eld study
identies two types/generations of quartz veins namely (1) Early quartz veins which are segmented, sigmoidal, dis-
continous, and parallel to the foliation of host rock. The quartz vein is lack of suldes, weak mineralized, crystalline,
relatively clear, and maybe poor in gold, and (2) Quartz veins occurred within a mineralized zone of about 100 m
in width and ~1,000 m in length. The gold mineralization is strongly overprinted by an argillic alteration zone. Themineralization-alteration zone is probably parallel to the mica schist foliation and strongly controlled by N-S or NE-
SW-trending structures. The gold-bearing quartz veins are characterized by banded texture particularly colloform
following host rock foliation and sulphide banding, brecciated, and rare bladed-like texture. The alteration types
consist of propylitic (chlorite, calcite, sericite), argillic, and carbonation represented by graphite banding and carbon
akes. The ore mineralization is characterized by pyrite, native gold, pyrrhotite, and arsenopyrite. Cinnabar, stibnite,
chalcopyrite, galena, and sphalerite are rare or maybe absent. In general, sulphide minerals are rare (
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1994; Idrus et al.,2007). Many current discover-
ies of placer (secondary) and primary gold min-
eralization genetically occur in association with
metamorphic rocks, for instance, Awak Mas me-
sothermal (Querubin & Walters, 2011), PoboyaLS-epithermal (Wajdi et al., 2011) and Bombana
orogenic gold deposits in Sulawesi (Idrus & Pri-
hatmoko, 2011). Gold-bearing quartz veins are
also recognized in Derewo metamorphic belt at
northern and northwestern part of Central Range
Papua. Some exploration reports categorized the
Derewo metamorphic-related quartz veins into
mesothermal gold deposit type.
The latest development, in January 2012, local
people in Buru Island discovered gold nuggets
in Gunung Botak and Gogorea areas, Wamsait
Villiage, Waeapo District, Buru Regency, Ma-
luku Province, Indonesia. Until November 2012,
about 100,000 artisanal and small-scale miners
have operated in Gunung Botak and about 5,000
traditional miners operating in Gogorea area. The
genetic type of the Buru Island gold mineralization
is still debatable. This paper is written on the basis
of a short site visit and preliminary study of the
primary gold mineralization to discuss some ob-
served geological characteristics and limited labo-
ratory analyses of restricted samples. This aims
to a better understanding of the possible genesis
of the metamorphic-hosted gold mineralization.
Regional geology
Buru is the third largest islandafter Seram and
Halmahera within Maluku Islandsof Indonesia.
The island belongs to MalukuProvince and in-cludes the Buru and South Buru Regencies. Buru
is shaped as an oval elongated form from west
to east. The maximum length is about 130 km
from east to west and 90 km from north to south.
The highest point on the island (2,700 m) is the
peak of Mount Kapalatmada. The relief is mostly
mountainous, especially in central and western
parts. With the length of about 80 km, Apo is the
largest river of Buru. It ows nearly straight to
the north-east and empties into the Kayeli Bay.
Buru Island constitutes one of the islands inthe Banda Islands, Central Maluku, Indonesia.
Geologically, it is part of the outer Banda Arc of
non-volcanics (Guntoro, 2000). Buru Island pro-
vides a key example of the processes involved in
mountain building and continental collision. So
far, it is generally accepted that Buru Island is a
microcontinent derived from Australian continent
that had been detached during the Mesozoic. The
emplacement of Buru Island to the present posi-
tion is still subject to debate. Figure 1 shows that
presently Buru Island is tectonically situated at the
fore arc of western-eastern trending Sunda-Banda
magmatic arc, which is terminated in the east at
the Banda Islands (Carlile and Mitchell, 1994).
Figure 1. Regional geological map of Indonesia. Some major gold-copper mineralizations are indicated. Major Tertiary
magmatic-arcs are also shown (Carlile and Mitchell, 1994). Buru Island is part of outer Banda arc (nonvolcanic) situatedat the fore arc of the western-eastern trending Tertiary-Quaternary Sunda-Banda magmatic arc.
Quaternary
Recent Volcanic Formation
Cenozoic Formation
Mesozoic Formation
Paleozoic Formation
Plutonic Rocks
Metamorphic Rock
REGIONAL GEOLOGY OFINDONESIA
(Darman & Sidi, 2000)
Papua Arc
Sunda - Banda Arc
Sulawesi Arc
HalmaheraArc
Kalimantan Arc
500 km
o10 N
o
10 S
o
100 Eo
110 Eo
120 Eo
130 E
Jakarta
Sunda Shelf
Sahul Shelf
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Some Key Features and Possible Origin of the Metamorphic Rock-Hosted Gold Mineralization
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11
Geology of Buru Island
The description of geological framework
of Buru Island is based on Geological Map of
Buru Island sheet, Moluccas (Tjokrosapoetro etal., 1993). Stratigraphically, the lithologies of
the Buru Island from the oldest to the youngest
are successively occupied by Wahlua Complex
(Pzw), Rana Complex (Pzr), Ghegan Formation
(Tg), Dalam Formation (Td), Tm (Mefa Forma-
tion), Kuma Formation (MTk), Wakatin Forma-
tion (Tmw), Hotong Formation (Tmh), Leko
Formation (Tpl), and Qa (Alluvium). The Wahlua
Complex (Pzw) mostly comprises moderate grade
metamorphic rocks ranging from green schist to
lower amphibolites, phyllite, slate, meta-arkosicsandstone, quartzite, and marble. The complex
is widely distributed in the eastern part of the
Buru Island (Figure 2). The Rana Complex (Pzr)
occupies the central part of the island around the
Rana Lake. This rock complex is composed of
phyllite, slate, meta-arkose, meta-greywacke, and
marble. The Ghegan Formation (Tg), Dalam For-
mation (Td), Kuma Formation (MTk), Wakatin
Formation (Tmw), Hotong Formation (Tmh), and
Leko Formation (Tpl) are mostly characterized
by carbonaceous clastic sediments and widely
extended in the western part of the Buru Island.The Mefa Formation (Pm) is typied by basaltic
lava and tuff and the presence of pillow structure
and diabase intrusion in the easternmost of the
island. Quaternary sediments are represented
by lake deposit in Rana (Qd), reef limestone
(Qt), and Quartenary alluvial deposit (Qa). Qa is
characterized by fragments, gravel, sand, silt, and
mud, which are distributed within the valley of
rivers and along the stream. Studied area is situ-
ated in the Wahlua metamorphic complex (Figure
2), which is of Upper Carboniferous until Lower
Permian in age.
Research methods
This preliminary study has been carried out
through several approaches including desk study,
Figure 2. Geological map of Buru Island (modied from Tjokrosapoetro et al., 1993). Gunung Botak and Gogorea are oc-
cupied by Pzw (Wahlua metamorphic rock complex). Note: Brief description of rock formation abbreviation is mentionedin Chapter 3 (Geology of Buru Island).
127 30 E126 00 E
3
00
S
3
00
S
4
00
S
4
00
S
127 30 E126 00 E
oo
o o
o o
oo
Gogorea
Gn Botak
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Some Key Features and Possible Origin of the Metamorphic Rock-Hosted Gold Mineralization
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13
4c).Bladed-liketexture is also observed, but it is
rare (Figure 4d). Those textures more likely devel-
oped in classic LS epithermal vein deposits. How-
ever, a few anomalies from shallow gold systems
in the Yilgarn Block of Western Australia are no-table. Comb, cockade, crustiform, and colloform
textures at the Racetrack deposit, Australia, de-
posited from CO2-poor uids in lower greenschist
facies rocks are also recognized (Gebre-Mariam
et al., 1993). Similar textures at the Wiluna gold
deposits in subgreenschist facies rocks, as well
as 18
Oquartz
measurements as light as 6 - 7 per ml,
provide some of the strongest evidence of meteoric
water involvement in some of the mesothermal
hydrothermal systems (Hagemann et al., 1992,
1994). Although it is uncommon, pseudomorphbladed carbonate texture could be present in
orogenic quartz veins/reefs if the hydrothermal
uids forming the ore deposit have the right phase
separation condition (personal communication,
Richard J. Goldfarb, 2011).
Alteration and Ore Mineralogy
Hydrothermal alteration style is identied ac-
cording to the eld observation and petrographic
analysis. As outlined above, the gold mineraliza-
tion zone is intimately associated with argillic-altered mica schist delineating an obvious high
Au grade zone of about 100 m width and 1,000 m
length. Clay mineral types characterizing argillic
alteration zone are unknown. The petrographic
analysis shows host rock is also propyllitically
altered typied by the presence of chlorite, cal-
cite, and sericite. Carbonation alteration style
represented by graphite banding (Figure 4a) and
carbon akes (Figure 5a,b) is a typical alteration
type occurring in metamorphic-related hydrother-
mal ore deposits.The eld observation and ore microscopic
analysis indicate that the ore mineralization is
characterized by pyrite, native gold (Figure 6a
& b), pyrrhotite, and arsenopyrite (Figure 6c).
However, cinnabar, stibnite, chalcopyrite, ga-
Figure 4. Photographs of gold-bearing quartz veins. (a) Handspecimen of the second quartz vein type with banding (collo-
form texture quartz vein following foliation), graphite, and sulphide banding, (b) The microphotograph of graphite banding
(dark) and sulphide banding (light) identied as arsenopyrite with white-grey colour and strong anisotropy, (c) Outcrop
of brecciated quartz vein and silicied mica schist in Gunung Botak, and (d) Handspecimen of highly oxidized/limoniticquartz vein with bladed-like texture. indicating a boiling condition.
Sulphide band
Graphite
6 cm 0.1 mm
1 cm
a b
c d
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14
lena, and sphalerite are rare or maybe absent. In
general, sulphide minerals are rare (
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Indonesian Journal on Geoscience, Vol. 1 No. 1 April 2014: 9-19
16
the two types of quartz veins. Summarized mi-
crothermometric data of analyzed uid inclusions
is shown in Table 2.
The data show that Tm of uid inclusions
hosted by rst type of quartz veins (that arecrystalline, clear, weak mineralized, and parallel
to the foliation) tend to have Tm ranging from
-0.1 to -0.3 C (average -0.22 C) corresponding
to salinity ranging from 0.18 to 0.53 wt.% NaCl
eq.(average 0.36 wt.% NaCl eq.), relatively lower
than those of second quartz vein type (Tm = -0.2
to 0.3 C; average -0.27 C) which correspond
to salinities of 0.36 to 0.54 wt.% NaCl eq., av-
eraging 0.48 wt.% NaCl eq. The temperature
of homogenization (Th), interpreted to be the
formation temperature of the rst type of quartz
vein varies from 234 to 354 C, that are relatively
lower than those of second quartz veins type (Th
= 321 to 400 C).
The petrographic study indicates that uidinclusions in both quartz vein types consist of
four phases including L-rich, V-rich, L-V-rich,
and L1-L2-V (CO2)-rich phases (Figure 7a).
In addtion, Sample B05VB is characterized by
abundant V-rich and L-rich inclusions (Figure
7b) which may imply a boiling condition with
an elevated temperature of 400 C. In fact, this
sample was taken from Gunung Botak where
the artisanal and smal-scale mining (ASGM) are
situated.
Table 2. Microthermometric Data of Fluid Inclusions within Two Quartz Vein Types associated with Primary Gold Miner-
alization in Buru Island, Maluku, Indonesia
No Sample Code Vein Tipe M Tm Th Salinity
1 B01 V First 123456789
-0.2-0.2-0.2-0.2-0.1-0.2-0.3-0.2-0.2
234.7242.8239323.7354325.6338.1350300
0.360.360.360.360.180.360.530.360.36
2 GK 01 First 123456
-0.3-0.3-0.2-0.2-0.3-0.2
319.5322.7285278308.6281.4
0.530.530.360.360.530.36
3 B05 V(B) Second 12345678
-0.3-0.3-0.2-0.2-0.3-0.3-0.3-0.3
354348389400400400400400
0.530.530.360.360.530.530.530.53
4 GB 01 Second 123456789
1011121314
-0.3-0.2-0.3-0.3-0.3-0.2-0.3-0.2-0.3-0.2-0.2-0.3-0.3-0.3
398384372398400331.8387349.7400325.8332.5361.2349.7321.3
0.530.360.530.530.530.360.530.360.530.360.360.530.530.53
Notes:
M = measurement number, Tm = Temperature of melting (oC)Th = Temperature of homogenization (oC) and Salinity (wt.% NaCl eq.)
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Some Key Features and Possible Origin of the Metamorphic Rock-Hosted Gold Mineralization
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17
Conclusions
According to the preliminary study, in this
section the authors would like to summarize
some observation parameters including host
rock type, mineralized quartz vein type and
geometry, structural control, quartz vein/ore
texture, alteration and ore mineralogy as well as
uid chemistry, temperature and salinity.
Host rock: Buru gold mineralization is hosted
by mica schist, which is composed of muscovite,
chlorite, and sericite. Thus this metamorphicrock is grouped into green schist facies.
Quartz vein type and geometry: First quartz
veins are typically segmented, sigmoidal, dis-
continous, and parallel to the foliation of the
metamorphic rocks. The quartz vein geometry
varies from cm to half a meter. Second quartz
veins occur within a mineralized zone of
about 100 m in width and ~1,000 m in length.
Gold mineralization is associated with argillic
alteration zone. The mineralized quartz vein is
probably parallel to the mica schist foliation.
Structural control: The mineralized zone
is generally brecciated and overprinting with
argillic alteration zone with N-S or NE-SW
orientation. Mineralized zone may strongly be
controlled by N-S or NE-SW-trending strike-
slip faults.
Quartz/ore texture: The second quartz vein
texture is characterized by brecciated, banding
texture such as colloform following foliation,
sulphide banding, and occasionally bladed-like
texture.
Figure 7. Microphotographs of uid inclusion petrography: (a) Carbonic (CO2-rich) uid inclusions, and (b) abundant
L-rich and V-rich uid inclusions in quartz veins from Gunung Botak, Buru Island. The carbonic inclusion indicates that
metamorphic uid is responsible for the formation of the gold mineralization, whereas the abundance of monophase L-rich
and V-rich inclusion is one of the important indications of boiling condition.
Alteration & ore mineralogy: The host rockis altered to propylitic, argillic, silicication, and
carbonation. Carbonation is shown by graphite
banding and carbon akes associated with quartz
banding. Typically, sulphide minerals are rare
(
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Some Key Features and Possible Origin of the Metamorphic Rock-Hosted Gold Mineralization
in Buru Island, Indonesia(A. Idrus et al.)
19
Idrus, A. and Prihatmoko, S., 2011. The meta-
morphic rock-hosted gold mineralization
at Bombana, Southeast Sulawesi: A new
exploration target in Indonesia,Proceedings
of The Sulawesi Mineral Seminar, Manado28-29 November 2011, p. 243-258.
Meldrum, S.J., Aquino, R.S., Gonzales, R.I.,
Burke, R.J., Suyadi, A., Irianto, B., and
Clarke, D.S., 1994. The Batu Hijau porphyry
copper-gold deposit, Sumbawa Island, Indo-
nesia.Journal of Geochemical Exploration,
50, p.203-220.
Mertig H.J., Rubin, J.N., and Kyle, J.R., 1994.
Skarn Cu-Au ore bodies of the Gunung Bi-
jih (Erstberg) district, Irian Jaya, Indonesia.
Journal of Geochemical Exploration, 50,
p.179-202.
Querubin, C.D., and Walters, S., 2011. Geol-
ogy and Mineralization of Awak Mas: A
Sedimentary Hosted Gold Deposit, South
Sulawesi, Indonesia. Proceedings of The
Sulawesi Mineral Seminar, Manado 28-29
November 2011, p. 211-229.
Tjokrosapoetra, S., Budhitrisna, T., and Rus-mana, E., 1993. Geological Map of Buru
Quadrangle, scale 1:250.000. Geological
Research and Development Centre, Band-
ung.
Wajdi, M.F., Santoso, S.T.J., Kusumanto, D.,
and Digdowirogo, S., 2011. Metamorphic
Hosted Low Sulphidation Epithermal Gold
System at Poboya, Central Sulawesi: A Gen-
eral Descriptive Review,Proceedings of The
Sulawesi Mineral Seminar, Manado 28-29
November 2011, p. 201-210.
Yardley, B. W. D., 1989. An introduction to
metamorphic petrology. Longman Scientic
& Technical, Essex, 247pp.
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Limestone Microfacies of Baturaja Formation along Air Rambangnia Traverse, South OKU, South Sumatra (S. Maryanto)
23
Figure 2. Geological map of Muaradua area, South Sumatra (Gafoer et al., 1993) and locations of Air Rambangnia traverse
(Maryanto, 2007a and 2008).
Tomt
Tmg
Tma
Tmpm
Qa
Qtk
Qhv
Qhv
TpokTmg
Tma
Qtk
Tmb
Tmb
Tpok
Tmg
TmaQtk
Qtk
Tmpm
Tma
Tmb
Tmpm
TmaTmg
Tmb
Tpok
Qtk
.
Kjgv
KjgvTpok
Pct
Kgr
Tpokc
Tpokc
Tmg
Qv
Qv
Qtr
QtrQtr
QtrQtr
QtrTma
Tma
Qa
Tmb
Tmpm
Tmg
Tmb
Tmpm
TmgTmpm
Qa
Qa
Qa
Kgr
Pct
Kgr
Kgr
PCt
Tmb
Qa
Kjgv
Kjgv
Km
KJg
Kjg
Qtr
Qtr
Qtk
Qtk
Tmb
KJgs
Pct
Kjgs
Tpok
Qa
Tmb
Tomt
Tpokc
Tomt
Qa
Kgr
Tmpm
Tmb
Tomt
Tma
Pct
Tomt
AirKi
ti
Air Kura-kura
AirB
uluh
AirTe
bangka
AirLa
hat
AirSaman
AirLengkajap
AirTamb
a
AirSubanB
esar
AirLaja
AirKem
u
AirG
ilas
AirSa
ka
AirB
atu-ba
tu
A
irNa
palan
AirRamba
ngnia
AirM
alau
AirSaka
AirSelabu
ng
AirKom
ering
Tpok
10
15
15
10
25
17
19
12
15
15
15
15
13
17
24 10
15
15
BATURAJA
Batuiputih
Negerisindang
Kungkilan
Penyandingan
Sundan
Sukoraja
Sagarakembang
Negeriratu
Sabahlioh
Tanjungkurung Simpang
Karangagung
Baturaja
Tanjungbringin
Negeriagung
Kotakarang
Sukaraja
Kotamarga
Gedong
MUARADUA
Umbulantelok
Umbulanmeliku
Airbungin
MehangginSaungnaga
Qhv
0
04
06S
0
04
35S
0
04
35S
0
04
06S
0103 54 E
0103 54E
0104 15E
0104 15 E
INDEX MAP
EXPLANATION:
Alluvium
Tuff Volcanic Unit
Volcanic Unit
Kasai Formation
Ranau Formation
Muaraenim Formation
Airbenakat Formation
Gumai Formation
Baturaja Formation
Talangakar Formation
Kikim Formation
Cawang Mem. Kikim Fm.
Melange Complex
Garba Formation
Insu Mem. Garba Fm.
Situlanglang Mem. Garba Fm.
Garba Granite
Tarap Formation
Air Rambangnia Traverse
Tmb
Tmg
Tma
Tmpm
QTk
QTr
Qhv
Qv
Qa
Tomt
Tpok
Tpokc
Kgr
KJgs
KJgv
Kjg
Km
Pct
0 10 Km
N
PRE-TERTIARY
PALEO
GENE
MIOCENE
QUARTERNARY
SUMATERA
oatstone intercalations are found containing some
coral skeletons. Stylobed is interlayering between
wackestone-packstone with marl ended the deposi-tion of the lower part of Baturaja Formation.
The middle part of Baturaja Formation is
composed of oatstone (Figure 6), of which later
evolved into argillaceous wackestone. Interlayersbetween oatstone with wackestone-packstone
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dominated the sequence, which are later ning
upward onto sometimes argillaceous wacke-
stone-mudstone. The next lithology is found as
oatstone.
The upper part of Baturaja Formation begins
with the presence of wackestone-mudstone lay-
ers. Stylobedded and or siliceous concretional
bedding reaches 80 cm in size are often found in
these layers (Figure 7). The concretional bedding
sometimes has a parallel direction to the bedding
(forming lens) and it shrinks to the upper part.
The above concretional beddings are overlain
by gradational and planar cross-bedding grain-
stones (Figure 8). Carbonate rock sequences in
this traverse is ended by wackestone-packstone
sometimes with dissolving porosities.
The carbonate rocks of Baturaja Formation
partially do not crop out along Air Rambang-
nia traverse, especially between sites 306-213.
Among that locations, the clastic sedimentary
rocks from Muaraenim Formation are exposed in
the form of claystone containing limestone boul-
ders. The sedimentary rocks are preserved dueto a tectonic strike-slip fault in N33oE direction.
Petrography
Based on a detailed petrography analysis,
the limestone types recognized are wackestone,
packstone, sandy packstone, grainstone, and oat-
stone. Each of these rocks, including the number
and type of the rock components would later be
used as the basis for microfacies determination
(Table 1).
Wackestone
Wackestone group also includes sandy
mudstone-wackestone, which is present as an
intercalation. The rocks are generally massive
with ne-grained fragmental bioclastic texture.
Bioclast always occur and comprises diverse type,
size, and amount of fossil. Nevertheless, fossil
types composing the rock can be identied, such
as red algae, mollusks, and foraminifera. Rarely
intraclast or extraclast arepreserved in the rocks,
the same as the presence of pellets. Terrigenous
materials are still observed in some rock samples
with limited amounts, scatteredly, and uneven.They are composed of quartz, feldspar, volcanic
Figure 3. Detailed stratigraphic measured map along Air Rambangnia traverse (Maryanto, 2007a and 2008) and sample
locations.
0 400 m
N
305
05SM305
EXPLANATION:
Outcrop location
Strike and dip
Fault (predicted)
Number of site
Sample location
River flow direction
10
301
302
303304
305 306
307308
309
310
311
312
313
314315
316
317
318
319
320
321
322
323 324
325326
327
24
108 7
15
128
10
8
10 12 10
SM301ASM302A
SM302B
SM303A
SM303B
SM304A
SM304B
SM304C
SM304D
SM305A
SM305B
SM305C
SM309
SM310
SM314ASM314B
SM315A
SM315B
SM316A
SM316B
SM317A
SM317B
SM318A
SM318B
SM320A
SM320B
SM321A
SM321B
SM323A
SM323B
SM323CSM323D
SM323E
SM324A
SM324B
SM324C
SM325A
SM325B
Volcanic breccia andsandstone withmudstone andlava intercalations
Conglomeratic sandstone overlainby packstone
Argillaceous wackestone withfloatstone intercalations
Bedded wackestone sometimes argillaceous
Clayey sandstone
Argillaceous wackestone
Carbonaceousmudstone andsandstone
Floatstone
Floatstone and wackestonesometimes argillaceous
Bedded floatstone withargillaceous packstone-wackestone
Bedded floatstone with argillaceouspackstone-wackestone
Argillaceous wackestone-mudstoneThick bedded floatstone
Argillaceous wackestone-mudstoneArgillaceous wackestone-mudstone
Argillaceous wackestone-mudstonewith lot of concretions
Argillaceous wackestone-mudstonewith concretion bedding
Argillaceous wackestone-mudstoneoverlied by grainstone
Grainstone, wackestone and packstone
Bedded wackestone-packstone
A B
Section A - B
AlluviumKikim Formation Baturaja Formation
B
A
To Muaradua
To Baturaja0S 04 25 11,30
E 104 08 40,0
0S 04 25 08,5
0E 104 09 30,5
0 0S 04 25 10,0, E 104 09 02,6
SM326
196 m
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and sedimentary rock fragments, unidentied
rock fragments, phosphate, and glauconite. Car-
bonate mud matrix often have changed into mi-
crosparite, some even have recrystallized to formpseudosparite together with carbonate grains.
Clay mineral matrix in general is inseparable with
carbonate mud matrix. The cement material is
always present with very limited quantities, par-
ticularly as orthosparite, iron oxides, authigenic
clay minerals, and silica.
Packstone
Packstone is generally massive with ne- to
medium - grained fragmental bioclastic texture.
Bioclast is composed of diverse type, size, and
amount of fossil, however, it is predominatedby red algae, mollusks, and foraminifera. Intra-
clast or exstraclast is present on the coarser size
of limestone fragments, spread unevenly, and
consists of coralline, bioclastic, and argillaceous
limestones. Less amount of very ne pellet some-
times changes into microsparite. Sparsely, terrrig-
enous materials are still present sporadically dis-
tributed, or sometimes excessively inuence the
rock name to become sandy. The rock matrix is
mainly preserved as carbonate mud, which often
changes onto microsparite and/or is recrystallized
to form pseudosparite together with carbonate
grains. Cement materials are always present in the
rocks as various amount of orthosparite calcite,
and rarely of iron oxides.
Grainstone
Grainstone is generally massive with medium-
to coarse - grained fragmental bioclastic texture.
Bioclast is quite dominant consisting of various
kind, size, and amount of fossil. Intraclast or
extraclast is observed unevenly in some coarse-
Figure 5. Massive marl contains a lot of mollusk mouldics,
this point is as the lower part of the Baturaja Formation.
Photographed in the 303 site of the Air Rambangnia traverse.
Figure 6. Very poorly sorted oatstone composing of the
middle part of Baturaja Formation. Photographed in the 314
site of the Air Rambangnia traverse.
Figure 7. Outcrop of wackestone-mudstone containing
siliceous concretions, is a constituent of the upper part of
Baturaja Formation. Photographed in the 322 site of Air
Rambangnia traverse.
Figure 8. Grainstone overlying mudstone-wackestone, pres-
ents as a constituent of the upper part of Baturaja Formation.
Photographed in the 324 site of Air Rambangnia traverse.
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Limestone Microfacies of Baturaja Formation along Air Rambangnia Traverse, South OKU, South Sumatra (S. Maryanto)
27
Table 1. Petrography Analysis Summary of the Limestones from Baturaja Formation along Air Rambangnia Traverse, South
Sumatra (Maryanto, 2007a)
SAMPLE CODE
DESCRIPTION
SM
302B
SM
303A
SM
303B
SM
304A
SM
304C
SM
304D
SM
305A
SM
305B
SM
305C
SM
314A
SM
314B
SM
315A
SM
315B
Structure m m o m m m m m f m o f m m m m o mTexture bf bf bf bf bfc bfc bf bf bf bf bf bf bf
Sorting m p p p p p p p p vp p vp vp
Fabric c c c o o o o o o o o o o
Av. grain size (mm) 1.80 0.70 1.40 0.30 0.20 0.20 0.20 0.80 0.20 0.80 0.80 1.20 1.80
Grain shape sr sr sr sr sr sr sr sr sr sr sr sr sa
Grain contacts p l c p l c p l c f f f f p f f f p f f p f p l
Percentages
Carbonate Grains
Green algae
Red algae
Bryozoans
Echinoderms
Coral
Benthic foraminifera
Planktonic foraminifera
Brachiopods
Moluscs
Ostracods
Sponge-spicules
Bioturbation
Unidentied fossils
Intraclasts / extraclasts
Pellet / peloids
Oolite / oncolite
-
1.67
4.33
2.67
4.67
6.00
1.33
2.00
15.00
-
-
-
8.33
5.33
-
-
10.67
1.33
-
4.00
-
3.00
-
1.33
16.33
-
-
-
6.33
-
-
-
-
1.33
0.67
-
-
4.00
-
-
7.33
-
-
-
24.67
2.67
0.67
-
-
0.33
-
1.33
-
8.00
-
-
5.33
-
-
-
2.00
-
-
-
-
-
0.33
-
-
0.67
-
-
4.00
-
-
-
9.67
-
-
-
-
0.33
-
-
-
0.67
-
-
1.67
-
-
-
9.67
-
-
-
-
0.67
0.67
4.67
-
5.67
1.00
1.00
4.33
2.67
-
-
5.00
1.33
-
-
-
-
1.00
1.33
0.67
7.33
-
0.67
5.67
0.67
-
-
3.67
1.67
-
-
-
1.67
-
0.67
-
1.67
-
0.67
5.00
0.33
-
-
3.33
-
-
-
-
0.67
0.67
1.00
-
1.67
-
1.33
6.00
-
-
-
5.00
-
-
-
-
1.67
2.33
1.33
1.33
0.67
-
1.33
13.00
1.67
0.67
-
5.33
5.67
-
-
-
0.67
1.33
1.33
3.33
6.33
0.67
1.33
4.00
1.67
0.67
-
6.00
3.33
1.33
-
-
2.33
1.67
1.33
8.33
5.00
0.67
2.00
4.67
2.33
-
1.00
3.00
4.33
1.00
-
Terrigenous Grains
Quartz
Feldspar
Rock fragmentsGlauconite
Phosphate
Opaque minerals
Carbon
1.33
-
1.33-
-
0.67
-
4.67
0.33
6.33-
-
0.67
-
3.33
1.33
10.33-
-
1.33
-
2.67
0.67
2.00-
-
-
-
1.00
-
1.33-
-
-
-
-
-
--
-
-
-
0.67
-
3.00-
-
0.67
-
1.00
0.67
1.67-
0.67
0.67
-
0.67
0.33
1.33-
-
-
-
3.67
2.33
2.00-
1.00
0.67
0.67
1.00
0.33
1.33-
-
-
-
1.67
0.33
--
-
1.33
-
0.33
-
--
-
-
0.67
Matrix
Carbonate mud
Clay minerals
-
-
3.33
32.33
-
4.67
22.00
-
-
-
-
-
50.33
3.00
10.33
-
15.00
-
6.00
-
26.67
-
34.00
6.00
39.33
-
Cementing Materials
Orthosparite
Iron oxides
Authigenic clays
Silica
9.67
2.67
-
-
-
3.00
-
-
-
1.67
2.00
-
0.67
0.67
-
1.33
-
1.00
-
-
2.00
0.67
2.33
2.67
1.67
3.33
-
0.33
4.00
2.33
0.67
-
3.00
1.67
-
-
4.00
1.33
1.67
2.67
3.33
3.67
-
-
8.00
1.67
-
-
6.33
1.67
-
1.00
NeomorphismsMicrosparite
Pseudosparite
Dolomite
Micritized mud
Pyrite
16.33
6.33
7.00
1.33
0.67
-
-
-
-
-
-
26.00
6.00
1.00
-
52.33
-
-
-
-
-
21.67
59.33
-
-
-
24.00
51.67
-
-
5.67
2.00
-
0.67
-
20.33
5.00
28.00
-
-
9.00
1.00
51.33
0.67
-
17.00
8.33
28.33
2.33
-
7.33
3.33
16.00
1.00
-
8.00
3.00
-
0.67
2.67
5.67
4.00
-
1.33
0.67
Porosities
Intraparticle
Mouldic
Vuggy
Intercrystal
Shelter dan fenestrae
Fracture
-
-
1.33
-
-
-
-
1.00
1.67
-
2.33
1.33
-
-
1.00
-
-
-
-
-
0.67
-
-
-
-
-
-
1.00
-
-
-
-
4.33
-
-
-
-
-
1.00
-
-
0.67
-
0.67
1.67
-
-
0.67
-
-
2.00
-
1.67
-
-
-
1.67
-
-
-
-
-
1.00
-
-
-
-
-
0.67
-
-
-
-
-
1.33
-
-
-
Rock Name G SP SP W W W W W W W W W W/F
SMF / FZ 11/6 12/6 12/6 10/7 19/8 19/8 10/7 10/7 19/8 10/7 10/7 10/7 5/4
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28
Table 1. .............continued (Maryanto, 2007a)
SAMPLE CODE
DESCRIPTION
SM
316A
SM
316B
SM
317A
SM
317B
SM
318A
SM
318B
SM
320A
SM
320B
SM
321A
SM
321B
SM
323A
SM
323B
SM
323C
Structure m m o m m m m m f m m f m o m o m p m
Texture bf bf bf bf bf bf bf bf bf bf bf bf bfSorting vp p p p p p p p p p p p p
Fabric c c c o c o c c o o o c o
Av. grain size (mm) 1.40 1.45 1.40 0.70 1.60 0.70 1.40 0.40 0.20 0.15 0.15 0.35 0.15
Grain shape sr sr sr sr sr r sr sr r sr r r r
Grain contacts p l c p l c p l c f p l c f p l c p l c f f f p l p l c f p l
Percentages
Carbonate Grains
Green algae
Red algae
Bryozoans
Echinoderms
Coral
Benthic foraminifera
Planktonic foraminifera
Brachiopods
Moluscs
Ostracods
Sponge-spicules
Bioturbation
Unidentied fossils
Intraclasts / extraclasts
Pellet / peloids
Oolite / oncolite
-
2.33
1.67
1.33
4.67
16.33
0.33
0.67
5.67
0.67
-
1.33
4.67
9.33
0.67
-
-
2.33
1.33
1.33
2.67
17.00
2.33
1.33
13.67
1.67
-
-
2.00
1.33
0.67
-
4.00
4.33
2.33
1.33
5.33
7.00
0.67
1.00
21.67
0.33
-
1.00
5.00
4.00
1.33
-
-
1.33
-
1.00
4.00
3.33
0.67
-
4.67
-
-
-
3.00
-
-
-
2.67
3.67
1.33
1.00
4.00
9.67
0.67
2.33
19.33
-
-
0.67
3.00
3.00
2.67
-
-
1.00
1.00
1.33
2.67
1.67
-
0.67
7.67
0.33
-
-
6.00
-
1.33
-
0.67
5.33
5.33
1.33
2.67
7.67
0.67
1.00
12.33
-
0.33
1.33
6.33
7.33
0.67
-
-
1.67
4.33
1.67
1.67
4.33
2.67
2.33
9.67
1.00
-
0.67
5.00
4.00
1.67
-
-
1.67
1.00
1.33
-
4.67
1.00
1.67
8.00
-
-
-
6.00
-
-
-
-
1.67
-
1.33
-
4.00
2.67
-
2.33
-
-
-
6.33
-
5.00
-
-
0.67
-
5.33
-
1.33
16.33
-
7.33
-
-
-
6.00
-
-
-
-
0.67
0.67
2.33
0.67
1.33
19.67
4.00
10.33
3.00
-
-
6.00
2.67
-
-
-
0.67
-
4.67
-
2.33
8.33
1.67
7.33
2.33
-
-
6.00
-
-
-
Terrigenous Grains
Quartz
Feldspar
Rock fragments
GlauconitePhosphate
Opaque minerals
Carbon
1.33
0.67
2.33
-0.67
0.67
-
1.67
0.67
1.33
--
0.67
0.67
1.00
0.67
1.67
0.33-
0.67
-
0.67
-
0.67
--
-
-
2.00
0.67
1.33
--
0.67
-
0.33
-
-
--
-
-
0.67
-
-
--
-
-
1.67
0.67
4.67
-3.00
0.67
-
-
-
1.33
--
-
-
0.33
-
-
--
-
-
1.00
0.67
-
-1.00
-
-
1.33
-
-
--
0.67
-
0.67
0.67
-
0.67-
-
-
Matrix
Carbonate mud
Clay minerals
23.33
-
13.67
-
10.67
-
10.00
-
9.33
-
10.00
-
13.33
6.00
9.33
6.00
9.33
4.00
10.67
7.00
5.00
8.00
22.33
-
28.33
8.00
Cementing Materials
Orthosparite
Iron oxides
Authigenic clays
Silica
8.00
1.67
0.67
-
4.67
2.67
-
-
5.67
1.67
-
-
1.67
0.67
-
-
11.00
1.67
-
0.67
3.00
1.33
0.67
0.67
4.33
1.33
1.00
0.67
5.67
3.33
1.33
-
4.00
1.67
-
-
0.67
1.33
-
-
5.33
1.33
-
-
4.33
3.00
-
-
3.00
1.00
-
-
Neomorphisms
MicrosparitePseudosparite
Dolomite
Micritized mud
Pyrite
7.336.00
4.00
-
0.67
17.004.67
-
1.33
-
7.003.00
4.00
2.67
-
60.336.67
-
0.67
-
8.004.00
-
1.00
-
56.33-
-
1.00
-
10.673.00
-
0.67
-
7.005.00
6.00
1.67
-
20.6720.67
10.67
-
0.67
30.673.00
21.67
0.67
-
27.675.00
5.00
-
-
5.672.00
-
-
-
11.332.00
9.67
-
0.67
Porosities
Intraparticle
Mouldic
Vuggy
Intercrystal
Shelter dan fenestrae
Fracture
-
0.67
1.33
-
-
-
0.67
-
2.67
-
-
-
-
-
1.67
-
-
-
-
-
0.67
-
-
-
-
1.33
3.67
-
0.67
-
-
0.67
2.33
-
-
-
-
1.33
4.33
-
-
-
-
-
3.33
-
-
-
-
-
1.00
0.67
-
-
-
-
0.67
-
-
-
0.67
0.67
1.67
-
-
-
0.67
-
8.67
-
-
-
-
-
0.67
-
-
-
Rock Name P/F P P W P W P P W W W P W
SMF / FZ 5/4 10/7 5/4 10/7 5/4 10/7 5/4 10/7 10/7 19/8 3/3 10/7 10/7
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Limestone Microfacies of Baturaja Formation along Air Rambangnia Traverse, South OKU, South Sumatra (S. Maryanto)
29
Table 1.............continued (Maryanto, 2007a)
SAMPLE CODE
DESCRIPTION
SM
323D
SM
323E
SM
324A
SM
324B
SM
324C
SM
325A
SM
325B
SM
326EXPLANATION
Structure m m o m p m m m m p m
Structure:
m = massive
o = with grain orientation
p = with several pores
f = with joints and fractures
Texture:
bf = bioclastic fragmenter
cf = clastic fragmenter
nc = non-clactic
c = crystalline
Sorting:
vw = very well sorted
w = well sorted
m = moderately sorted
p = poorly sorted
vp = very poorly sorted
Fabric:
c = closed
o = opened
Grain shape:
va = very angular
a = angular
sa = sub-angular sr = sub-rounded
r = rounded
wr = well rounded
Grain contact:
f = oating
p = point
l = long
c = concave-convex
s = sutured
Rock name:
BW = Wackestone
BW/F = Wackestone/oatstone BP = Packstone
BP/F = Packstone/oatstone
BG = Grainstone
SBP = Sandy packstone
Microfacies:
SMF = Standard microfacies
(Flugel, 1982)
FZ = Facies zone
(Wilson,1975)
Texture bf bf bf bf bf bf bf bfSorting p p m m p p p p
Fabric c o c c c c c c
Av. grain size (mm) 0.30 0.15 1.20 1.60 1.10 0.80 0.30 0.35
Grain shape sr sr sr sr sr sr sr sr
Grain contacts p l f p p l c p l c p l c p l c p l c p l c
Percentages
Carbonate Grains
Green algae
Red algae
Bryozoans
Echinoderms
Coral
Benthic foraminifera
Planktonic foraminifera
Brachiopods
Moluscs
Ostracods
Sponge-spicules
Bioturbation
Unidentied fossils
Intraclasts / extraclasts
Pellet / peloids
Oolite / oncolite
-
5.67
0.67
4.67
-
2.67
7.67
2.67
9.33
2.67
-
-
6.33
4.00
3.33
-
-
4.67
-
5.00
-
0.67
4.00
2.67
6.33
2.67
-
-
4.67
-
6.00
-
-
5.33
3.33
10.33
2.67
22.00
0.67
2.00
17.00
-
-
-
-
3.67
0.67
-
-
3.33
2.33
9.33
1.33
19.67
1.33
1.67
30.33
-
-
-
-
6.00
0.67
-
-
4.67
1.67
6.67
3.33
14.00
4.67
4.00
23.00
0.67
-
-
4.33
5.33
0.67
-
-
4.67
2.00
3.33
4.00
11.33
2.67
2.67
14.00
1.33
-
-
4.00
2.33
0.67
-
-
4.33
1.67
2.00
3.00
10.33
5.67
2.67
6.33
1.33
0.67
-
6.00
-
-
-
-
2.67
3.33
4.67
3.33
29.00
0.67
2.00
11.33
0.67
-
-
2.67
3.33
1.00
-
Terrigenous Grains
Quartz
Feldspar
Rock fragments
GlauconitePhosphate
Opaque minerals
Carbon
-
-
-
0.670.67
-
-
1.00
-
-
-0.33
-
-
0.67
-
-
--
-
-
0.67
-
0.67
1.000.33
-
-
1.00
-
1.33
0.67-
-
-
1.33
-
-
0.67-
0.67
1.00
1.00
0.33
-
--
-
-
0.67
-
-
-0.67
1.33
-
Matrix
Carbonate mud
Clay minerals
9.33
5.00
17.33
4.00
-
-
-
-
-
-
6.00
-
12.33
5.00
12.67
5.67
Cementing Materials
Orthosparite
Iron oxides
Authigenic clays
Silica
2.67
1.33
-
13.00
1.00
1.67
-
6.67
14.00
1.67
1.33
-
7.67
1.33
1.00
-
9.00
1.33
0.67
-
4.33
1.33
1.00
0.67
4.67
6.00
-
-
3.33
2.67
-
-
Neomorphisms
MicrosparitePseudosparite
Dolomite
Micritized mud
Pyrite
6.003.00
7.33
-
-
5.673.33
14.00
-
-
-6.00
-
3.00
-
-6.67
-
1.00
-
-3.00
6.00
2.00
-
15.004.00
8.00
0.67
-
5.33-
7.67
2.67
-
6.333.00
4.00
2.67
0.67
Porosities
Intraparticle
Mouldic
Vuggy
Intercrystal
Shelter dan fenestrae
Fracture
-
-
1.33
-
-
-
0.67
1.67
3.33
-
2.67
-
-
-
5.67
-
-
-
0.67
0.67
2.33
-
-
-
0.33
-
1.67
-
-
-
-
-
2.33
-
-
-
0.67
-
10.33
-
-
-
0.67
-
1.00
-
-
-
Rock Name P W G G G P P P
SMF / FZ 10/7 19/8 12/6 12/6 12/6 10/7 10/7 10/7
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30
sized rocks, and consists of coralline, bioclas-
tic, and argillaceous limestones. Pellet is very
rarely preserved. A less amount of terrigenous
materials are present evenly at the upper part
of stratigraphic sequences. They are composedof quartz, feldspar, volcanic and argillaceous,
metamorphic, and unidentied rock fragments,
very rarely glauconite, phosphate, mica, and
opaque minerals. Cement materials are always
present in the rocks with a diverse number as
orthosparite, iron oxides, authigenic clays, and
silica. Most orthosparite is present from phreatic
meteoric environment, followed by marine and
burial environments. Small amount of iron oxides
lls cavities and fractures in the rock. Authigenic
clay minerals are preserved as pore-cavity ller.
Silica in the form of quartz, feldspar, and zeolite
are preserved from the phreatic meteoric environ-
ment after cementation by the orthosparite calcite.
Floatstone
Floatstone is generally massive with coarse-
grained fragmental bioclastic texture, both with
closed fabric or opened fabric. Bioclast is made
up of diverse type, size, and amount of fossil. In-
traclast or extraclast is sporadically distributed in
a few samples, and is composed of coralline, bio-
clastic, and argillaceous limestones. Terrigenous
materials are preserved in a limited number and
spread out unevenly. Carbonate mud matrix often
has changed into microsparite. Cement materials
are present limitedly within inter and intra particle
pores.
Microfacies Interpretation
Wackestone generally has an inversion tex-
ture, i.e. coarse grains stuck in carbonate mud
matrix, well washed grains, and has various fos-
sils. Such limestone was generally deposited in
back reef down-slope (SMF10-FZ7). Limestone
facies type resides in this deposition environment
including argillaceous-rich limestone to some
packstone.
In addition to being in the back reef down-
slope, wackestone may also be formed in very
restricted bays and ponds (SMF19-FZ8). Specialcharacteristic of the limestone deposited in this
depositional environment is the presence of fe-
nestrae porosity type, as a result of a tidal activity
(Tucker and Wright, 1990).
Coarse-grained packstone can be deposited in
another deposition environment. In some cases,packstone can develop into grainstone with the
bioclast composed as well of coated and worn red
algae. This rock was usually deposited in slopes
and shelf edges (SMF12-FZ6). Abrading and
leaching of carbonate grains mark the grainstone
was deposited in winnowed platform edge sands
(SMF11-FZ6).
Packstone can be interpreted as reef-ank fa-
cies (SMF5-FZ4), characterized by the presence
of bioclasts mostly derived from the reef dwell-
ers and reef builders, such as coral and bryozoa
reefs (Read, 1985). Packstone and sometimes
oatstone with large amount of carbonate mud
matrix is interpreted as reef-ank deposits.
This microfacies interpretation can be done to
each limestone sample petrography tested. The
interpretation microfacies result can be used to
trace back the development of facies deposition of
a limestone formation, in this case is the Baturaja
Formation along the Air Rambangnia traverse.
Discussion
Based on petrographic data (Table 1), the
character of each sample can be known and traced
to order their stratigraphy. The volcanic rocks of
Kikim Formation are deposited unconformably
on the limestone of Baturaja Formation, while
clastic sedimentary rock of Talangakar Formation
is not exposed in this traverse (Sukandi et al.,
2006). The lowest part of the Baturaja Formation
preceded by grainstone was deposited in the win-
nowed platform carbonates, which is above the
wave base (SMF11-FZ6). This area is very close
to the beach characterized by the presence of ar-
gillaceous material from the transgression phase
(Andreeva, 2008), making it into the bay or pond
(SMF19-FZ8). The depositional environment of
the limestones repeated from very restricted pond
and bay (SMF19-FZ8; Figure 9) to back-reef local
slope (SMF10-FZ7; Figure 10) is due to regres-
sive and transgressive phases. These depositionalenvironments are characterized by the presence
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Limestone Microfacies of Baturaja Formation along Air Rambangnia Traverse, South OKU, South Sumatra (S. Maryanto)
31
Figure 10. Photomicrograph of wackestone (sample code
SM314A) with bioclasts of mollusks (mol) and large
foraminifera (for) distributed in carbonate mud matrix (lpr)
characterizing the SMF10-FZ7 on back-reef down-slope.
SM314A|----------| 0,5 mm
mol
for
lprpor
Figure 11. Photomicrograph of packstone/oatstone (sample
code SM316A) with various bioclasts of red algae (gang)
and large foraminifera (for) distributed in carbonate mud
matrix (lpr), typies the SMF5-FZ4 reef-ank area.
SM316A|----------| 0,5 mm
sem
for
lpr
for
gang
of wackestone-packstone interlayers some parts
of argillaceous and with oatstone intercalation.
Regression process affects sedimentation in
the middle part of Baturaja Formation, initiated
by oatstone from reef-ank facies (SMF5-FZ4;
Figure 11 and 12). The middle part of the BaturajaFormation is dominated by limestones from that
depositional environment. The depositional envi-
ronment repeated alternation with back-reef local
slope facies (SMF10-FZ7; Wilson, 1975) and their
lithology composed of wackestone-packstone.
The lithology from the back-reef local slope
(SMF10-FZ7) continued until the upper part of
the formation, and it was preceded by the presence
of wackestone-mudstone. Regressive phase led
the depositional environment to evolve into the
very restricted bay or pond (SMF19-FZ8; Flugel,
Figure 9. Photomicrograph of wackestone (sample code
SM305C) with very ne - grained size, characterizing the
SMF19-FZ8 on very restricted bay or pond.
SM305C|----------| 0,5 mm
Figure 12. Photomicrograph of packstone (sample code
SM318A) with various bioclasts of mollusks (mol) and large
foraminifera (for) distributed in carbonate mud matrix (lpr),
characterizing the SMF5-FZ4 on reef-ank area.
SM318A|----------| 0,5 mm
mol
for
lpr
for
mol
lpr
1982). Furthermore, transgressive phase led to be-
come the depositional environment of slopes and
shelf edges (SMF12-FZ6; Andreeva, 2008; Fig-
ure 13) composed of grainstone with graded and
planar cross-bedded structures (Bathurst, 1975;
Kendall, 2005). Finally, the lithology sequence
ended by the presence of wackestone-packstone
deposited at back-reef local slope (SMF10-FZ7;
Jones and Desrochers, 1992; Figure 14).
Paleogeographically, the reef complex is
located in the east of the researched area, thus
the highland is being in the west part (Maryanto,
2005). The Baturaja limestones were deposited,
with the inuence of a regional transgression,
on the Late Oligocene age. The development of
depositional environment between time forming
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Figure 14. Photomicrograph of packstone (sample code
SM325B) with abraded bioclasts of mollusks (mol), large
foraminifera (for), and echinoderms (ech) distributed in
carbonate mud matrix, characterizing the SMF10-FZ7 on
the back-reef down-slope.
BASEMENT ROCKS
N
N
2
3
4UPPER PART
Fore-reefBack-reefCore-reef Reef-flank
Bay
Tidal Flat
Basin
Local Basin
Local Basin
Local Basin
Lagoon
Tidal Channel
River
Regression
Transgression
INVESTIGATED AREA
1
Open Marine
CalcareousSiliciclastics
Slope
BASEMENT ROCKS
MIDDLE PART
Fore-reefBack-reefCore-reef Reef-flank
Bay
Tidal Flat
Basin
Lagoon
Tidal Channel
River
INVESTIGATED AREA
Slope
BASEMENT ROCKS
N
LOWER PART
Fore-reefBack-reefCore-reef Reef-flank
Bay
Tidal Flat
Basin
Lagoon
Tidal Channel
River
Regression
INVESTIGATED AREA
Slope
BASEMENT ROCKS
N
BASEMENT ROCKS
Fore-reefBack-reefCore-reef Reef-flank
Basin
Lagoon
River
Stable landfollowed by erosion
INVESTIGATED AREA
Slope
Figure 13. Photomicrograph of grains