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British Geological Survey

TECHNICAL REPORT WC/95/20 Overseas Geology Series

CHARACTERISATION OF GOLD FROM THE RAUB AREA, PAHANG, MALAYSIA

P J Henney, M T Styles, P D Wetton and D J Bland

A Report prepared for the Overseas Development Administration under the ODA/BGS Technology Development and Research Programme, Project 92/1

OD.4 Classification Subsector: Geoscience Theme: G1 Promote environmentally sensitive development of non-renewable natural resources Project Title: Alluvial Gold Characterisation in Exploration Planning Reference number: R5549

Bibliographic reference: P J Henney, M T Styles, P D Wetton and D J Bland 1995

Characteristation of Gold from theRaub area, Pahang, Malaysia BGS Technical Report WC/95/20

Keywords: Gold, alluvial, soil, bedrock mineralogy, electron microprobe, Rauh, Malaysia,

Front cover illustration: Bedrock gold with pyrite inclusions, Rauh. Sample MA99

CNERC 1995

Keyworth, Nottingham, British Geological Survey, 1995

TABLE OF CONTENTS

List of plates

List of figures

List of tables

EXECUTIVE SUMMARY

1. INTRODUCTION

1.1 Geology of the Raub gold deposit

2. SAMPLE COLLECTION

3. BEDROCK SAMPLE STUDIES.

3.1 Sample descriptions 3. I . I Hand specimens 3.1.2 Thin section stm@

3.2 Electron microprobe analysis 3.2. I Quantitative electron microprobe analysis 3.2.2 Accessory mineralogy 3.2.3 Summary

4. ALLUVIAL GOLD GRAINS

4.1 Gold morphology study for Raub samples 4. I . I SEM characterisation. 4. I . 2 Size & shape analysis.

4.2 Electron microprobe analysis 4.2. I Quantitative electron microprobe analysis 4.2.2 Inclusions in gold grains 4.2.3 Summary

5. COMPARISON OF BEDROCK AND ALLUVIAL GOLD

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8

8

9

10

10 10

10

11

11 12

12

13

13

13

15

18

18

2 1

22

22

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5.1 Comparison of gold compositions

5.2 Comparison of mineral inclusions

5.3 Morphology

6. SUMMARY AND CONCLUSIONS

7. ACKNOWLEDGEMENTS

8. REFERENCES

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23

23

24

25

26

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Plate captions

Plate 1

Plate 2

Plate 3

Plate 4

Plate 5

Plate 6

Plate 7

Plate 8

Plate 9

Plate 10

Open pit at Raub mine.

Quartz veins in low-grade metasedimentary host rocks at Raub.

Gold at the contact of vein quartz and a graphitic shale inclusion. Field of view approx. 5mm. Sample MA 25.

Pyrite inclusion in gold. Field of view approx. 3mm. Sample MA 99.

Gold and pyrite within vein quartz. Field of view approx. 2mm. Sample MA 127.

Gold at the contact of quartz and scheelite. Field of view approx. 1.6mm. MA2.

Alluvial gold grain showing complex microdendritic surface features. Sample MA 86-28.

Alluvial gold grain showing rounded surface features. Sample MA 86-17.

Alluvial gold grain showing rounded and porous surface features. Sample MA 88-24.

Alluvial gold grain showing flattened, abraded and rounded surface features. Sample MA 102-6.

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Figure Captions

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Map showing location of Raub deposit.

Map showing simplified geology and alluvial gold sample sites in the Raub area.

Bedrock gold “S” curve for the Raub area.

Comparison of alluvial and bedrock “S” curves for the Raub mine area.

Alluvial gold “S” curves for the Raub area.

Comparison of alluvial and bedrock “S” curves for the Raub area.

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List of Tables List of samples from the Raub area. Table 1

Table 2 EPMA data and “S” curve for bedrock sample MA la/ lb.

Table 3 EPMA data and “S” curve for bedrock sample MA 2a/2b.

Table 4 EPMA data and “S” curve for bedrock sample MA 25.


Table 6 EPMA data for bedrock sample MA38.



Table 9 Shape data, FSHAPE and area “S” curves for alluvial samples MA 86 & 87.

Table 10 Shape data, FSHAPE and area “S” curves for alluvial sample MA 88.


Table 12 Shape data, FSHAPE and area “S” curves for alluvial samples MA 90 & 91.

Table 13 Shape data, FSHAPE and area “S” curves for alluvial samples MA 92, 93, 94 & 95.



Table 16 Shape data, FSHAPE and area “S” curves for alluvial

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sample MA 101.


Table 18 EPMA data and “S” curve for alluvial sample MA 23.


EPMA data and “S” curve for alluvial sample MA 87. Table 20




Table 24 EPMA data for alluvial sample MA 91.










Tables 34 EPMA data & composition of mineral inclusions from &35 Raub alluvial gold.

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EXECUTIVE SUMMARY This study of gold from the Raub area, forms part of a wider study of gold from Malaysia and elsewhere carried out under ODABGS Technology Development and Research (TDR) project "Alluvial Gold Characterisation in Exploration Planning" (Project 92/1, R5549). The TDR Programme is a contribution to the British Government programme of aid to the developing countries. At Raub, gold is found in quartz veins in Carboniferous shales and phyllites, a style of mineralisation found in several areas in Malaysia. Bedrock samples were collected largely from drillcores with a few surface samples from the Raub gold mine. Alluvial samples were mainly from streams and rivers within a few km of the mine. Laboratory studies were made to characterise the bedrock and alluvial gold and to check which features of the alluvial gold were inherited from the bedrock source and which had been changed. Studies of size and shape of proximal alluvial gold show, as expected, that the gold is probably derived from a single source. The low degree of deformation is consistent with a local provenance from nearby bedrock mineralisation.

The bulk compositions of the bedrock and alluvial gold from the mine site are very similar, particularly the limited range of Ag contents, between 1 and lOwt % for the majority of the grains. The minor variations observed in the Ag contents of a small number of alluvial grains (including the presence of gold-rich rims and the formation of silver-rich tracks) can be attributed to minor recrystallisation of gold grains due to weathering processes in the surface environment. These data demonstrate that the proximal alluvial gold is derived from the bedrock mineralisation. The occurrence of alluvial gold from sites several kilometers to the north and south of the mine area is compositionally distinct (in Ag content and minera linclusions) and indicates the presence of gold from a source other than the type found at the Raub mine.

Microscopic mineral inclusions in alluvial gold grains are dominantly pyrite with lesser arsenopyrite and gersdoflite and minor chalcopyrite and tetrahedrite. These minerals occur in the sulphide mineralisation associated with the bedrock gold and as rare inclusions within the gold. Only gersdorffite occurs as an 'exotic' mineral species found only as inclusions in the alluvial gold but not described from the bedrock mineralisation assemblage.

Studies of gold from Raub confirm that the alluvial gold preserves many of the mineralogical, compositional and morphological features of its bedrock source and demonstrate that different sources can be distinguished. The relationships demonstrate that detailed studies of alluvial gold can be used to characterise the bedrock source and provide important constraints on gold exploration programmes.

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1. INTRODUCTION

This reDort contains the results of work carried out on the ODA/BGS Technology Development and Research project 92/1 , R5 549 entitled Alluvial Gold Characterisation in Exploration Planning. The TDR Programme is part of British Government technical assistance to developing countries. The aim of the project is to characterise gold grains from bedrock and associated alluvial deposits to establish whether variation in bedrock gold is inherited by the alluvial gold. Further, if this is the case features found in alluvial gold might be used to identie possible source terrains. This study involves sample collection and laboratory study of gold from various developing countries and includes the examination of morphological features such as size and shape, chemical composition and mineral inclusions within the gold.

Five areas have been studied in Malaysia and all work has been in close collaboration with the Geological Survey of Malaysia (GSM) - BGS (ODA Technical Co-operation) Gold Sub-programme. The particular aim of the work in Raub was to study bedrock and closely related eluviaValluvial gold and also to make comparisons with alluvial gold from a slightly wider area but probably derived from a similar type of bedrock mineralisation. Similar studies have been carried out in Zimbabwe, Ecuador and Fiji.

1.1 Geology of the Raub gold deposit The Raub area in the western part of Pahang State in Peninsular Malaysia has a long history of gold mining. Small scale operations have produced gold for centuries and systematic mining started in 1889 when the Raub Australian Gold mine was established. Extensive underground mining took place and this continued to 1985 during which time the mine at Raub produced nearly 1 million ounces, 85% of the production of Peninsular Malaysia. Mining is now by open pit methods (Plate l), working a mixture of deeply weathered overburden and bedrock (Plate 2).

The geology of the Raub area and working at the mine has been described in detail by Richardson (1939) and a more recent synthesis given by Gunn et a1 1993. Onlv a brief summary will be given here. Raub is situated close to the western margin of the central belt of Peninsular Malaysia (Figure I), a fault bounded tract of marine and continental margin sediments of Palaeozoic age between the western and eastern granite ranges of Triassic age. These belts have recently been interpreted as microplates by Cobbing et a1 (1992). Hutchison (1989) regarded the western margin of the central belt, the Raub-

as a suture, the site of a former subduction zone,

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The Raub mine is situated in the Raub Group, a series of calcareous shales and siltstones with minor limestones. The shales have been intruded by a later granite and some of the alluvial samples were in an area that drained from the granite area. The rocks are highly folded and have undergone low-grade metamorphism to form fissile shales and slates. The rocks are extensively faulted and there are abundant quartz veins along the fault or shear zone that passes through the area of the mine. Gold usually occurs in quartz veins, in some places associated with minor carbonate veins and ofken associated with graphitic lamina. The sulphide content of the veins is low, less than 5% and there is no general correlation between gold content and sulphide abundance.

2. Sample Collection.

A suite of bedrock, soil and alluvial samples was collected in the RaUb area; a list Of

samples is given in Table 1 and the locations of Several are Shown on Figure 2. All the

bedrock gold samples are from the Kim Chuan mine, the current name for the mine at Raub. Bedrock samples are mostly from drillcores from the mine area and also from hand specimens from the working pit. All these samples were donated or collected with the pemission of the mine manager. Many of the samples were actually collected as part of the GSM-BGS Gold Sub-programme, during which complementary studies on the samples were carried out (Gunn et al. 1993).

The mine manager also donated smali samples of table concentrate, one of which (MA 23) was of weathered near-surface ore and is considered a soil sample rather than bedrock gold.

Alluvial samples were collected in the immediate vicinity of the mine for comparison with the bedrock gold. Samples 86-88 were collected close to the mine and samples 96 and 97 about 2 km from the mine (but these were from streams draining into the mine area). Samples 90 and 91 were fiom streams draining away from the mine.

Samples were also collected from localities in the vicinity where gold had been reported in the GSM stream sediment geochemicai survey. The first of these (MA 92-95) was in the Kelau valley, about 15 km south of Raub but in a similar structural setting in the Raub-Bentong fault zone. The second (MA 100- 102) was about 10 km to the north of

Raub. They were collected to compare the gold with that from the Raub area,

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recovered,

3. BEDROCK SAMPLE STUDIES.

Gold was found in all but one bedrock sample. However not all gold-bearing samples could be sectioned in such a way as to ensure that the gold was preserved on the oolished thin section, and therefore only seven samples were selected for detailed I

mineralogical and electron microprobe studies.

3.1 Sample descriptions

3. I . I Hand specimens Hand specimens were obtained from both drillcore and mindpit exposures and are composed dominantly of vein quartz containing visible gold. The gold is most commonly associated with thin stylolitic structures, defined by thin bands and laminae of graphitic shale, in some places with sparse sulphide mineralisation and in others associated with Fe-Mn bearing carbonates (Plates 3-6).

3. I .2 Thin sectioii/;llolished block stu&

MA1 Gold occurs as irregular grains and rounded blebs, up to 0.5 mm in size, within massive vein quartz close to the contact between quartz and a graphitic shale xenolith. Pyrite and arsenopyrite are also present but not intimately associated with the gold.

MA2 Gold occurs as irregular grains and rounded blebs within massive vein quartz close to contact between quartz and a graphitic shale xenolith and also at the contact between quartz and scheelite. Pyrite and arsenopyrite are also present but not intimately associated with the gold.

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MA 36 Gold occurs as randomly distributed irregular grains and rounded blebs, up to 0.2 mm in size, within fractures and pores in massive vein quartz. Pyrite and arsenopyrite occur in discrete veinlets cross-cutting the massive quartz.

MA 38 and MA 39 Gold occurs as irregular and rounded grains and aggregates in fractures, minor dislocations and veinlets cutting massive vein quartz, some of which also host pyrite and arsenopyrite.

MA 127 Gold occurs as rounded grains along with abundant arsenopyrite within a graphitic veinlet cutting massive vein quartz.

3.2 Electron microprobe analysis

3.2. I Quantitative electron microprobe analysis Quantitative analyses have been made on over 50 gold grains and associated minerals using the CAMECA SX50 with a wavelength dispersive system, with a 30 kV accelerating voltage and 20 nA beam current. Sixteen elements were analysed for each point. The in-house standards used were mostly pure metals apart from: pyrite for S , arsenopyrite for As, HgTe alloy for Hg and Te, and PbF2 for Pb. The main impurity in

the gold is silver and the variation in silver content for each sample is shown as a variant of a standard “S” curve, produced by plotting the values in ascending order of silver content. Different populations are shown by changes in slope of the curve. The results of the gold analyses and “S” curve for each sample are presented in Tables 1-8.

Trace element contents in the gold are generally low, at or below detection limits, but some Bi (up to 0.17% ), Cu (up to 0.13% ), As (up to 0.17% ), Hg (up to 0.43%), Te (up to 0.11% ), Fe (up to 0.17% ), S (up to 0.17% ), Zn (up to 0.12% ) was detected. Fineness values range from 914.54 up to 985.40.

MA1 28 analyses were obtained of gold from two different sub-samples. The Ag “S” curve shows the two distinct populations, one with 3.24-3.55 and the other with 5.12-6.18 wt% Ag.

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M A 2 13 analyses were obtained from Au in this sample. The Ag “S” curve again shows two distinct populations, one with 4.45-5.17 and the other with 6.99-7.43 wt% Ag.

MA 25 34 analyses were obtained from gold in this sample. The Ag “S” curve again shows two distinct populations, one smaller, with only 3 points, with 7.44-7.48 and the other with 7.73-8.32 wt% Ag and Fineness values range from 914.54 up to 923.55.

M A 36 22 analyses were obtained from Au in this sample . The Ag “S” curve again shows two distinct populations, one with 4.62-4.87 and the other with 5.79-7.33 wt% Ag.

M A 38 Only 3 analyses were obtained from Au in this sample and no “S” curve was plotted.

MA 39 Only 6 analyses were obtained from Au in this sample. An “S” curve was plotted but cover a narrow range in Ag values (1.50-1.87 wt%).

M A 127 16 analyses were obtained from gold in this sample. The Ag “S” curve shows three distinct populations, one point with value 4.40, a group at 4.71-4.95 and another at 5.13-5.16 wt% Ag.

3.2.2 Accessory mineralogy The main sulphide accessory minerals associated with the gold mineralisation at Raub are pyrite and arsenopyrite with minor stibnite, sphalerite, pyrrhotite and chalcopyrite. Trace molybdenite, tetrahedrite, galena and tellurides, as inclusions in the pyrite and arsenopyrite, are also present (Gunn et al. 1993). Scheelite is also a minor component in the Au bearing quartz veins and the gold is also associated with Fe-Mn carbonates.

3.2.3 Summary Individual samples show narrow ranges in composition but when all the sample data are combined, multiple populations are discernible. An “S” curve of Ag content for all the bedrock gold samples from the Raub deposit (Figure 3) has a complex shape with gaps and inflections in the curve suggesting that at least six distinct populations are present with Ag contents ranging from minimum of circa 1.5 wt% up to a maximum of circa 8.8 wt%. This suggests that the mineralisation history in the Raub deposit is

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different and relatively complex compared to that of similar deposits elsewhere in Malaysia (e.g. Lubuk Mandi, Penjom). The overall trend is relatively narrow but with locally complex variations. This may reflect variations in the temperature of the mineralisation through the deposit or possibly multiple mineralisation events. The variations in Ag content do not show any correlation with trace element abundances within the samples studies here, which have abundances close to the detection limits of the WD-EPMA technique in most cases.

4. ALLUVIAL GOLD GRAINS

The alluvial samples were hand-picked under a binocular microscope to separate the gold from other heavy minerals present in the heavy mineral concentrate produced &er superpanning the bulk sample. These grains were placed on double sided black carbon tabs that were mounted on a glass slide for examination of surface features, by scanning electron microscopy (SEM). Grains <10 microns in size were mounted directly onto epoxy resin on a glass slide and were not studied by SEM. Samples of alluvial gold from seven localities were examined using optical petrography, SEM and image analysis techniques using a KONTRON system for measurements of size and shape of the grains. This was carried out prior to polishing the grain mounts for EPMA. Some of the differing characteristics and morphologies of the alluvial grains are illustrated in Plates 7 - 10.

4.1 Gold morphology study for Raub samples

The alluvial gold grains sampled for EPMA were characterised morphologically by the use of two methods. The visual morphology of a selection of the grains from each sample was studied by SEM techniques utilising a Cambridge Stereoscan 250 instrument. Dimensional morphology characterisation was produced using a semi- automated Image Analysis program, developed for this project, and performed using a Kontron IBAS image analysis system.

4. I . I SEM Characterisation

Luie River - MA 97. Grains fkom this location are mainly irregular nugget forms with some elongated examples. Some of the grains show rounded grain shapes whilst all show folding and rounding of delicate edge sections. Grain surfaces show minor plastic deformation at high magnification and are irregular in nature though sponge-like or dendrite based

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secondary growth surface features are absent. The morphology seen is consistent with gold close to its source with minor deformation during transport in the river.

Raub Valley -MA 86, MA 88, MA 89, MA 90.

Samples MA 87 and MA 9 1 contained insufficient grains for analysis.

Gold from sample MA 86 displays irregular grain forms tending towards flat nuggets. The majority of the grains show rounding and folding of their edges though the surface textures of the grains vary more widely. Plate 7 and Plate 8 show the two contrasting surface forms present, the former being a complex structure of micro-scale dendrites whilst the latter shows a more smoothed and deformed surface. The figures also show two extremes of grain shape ranging from flat regular nuggets to more rounded elongated forms. Sample MA 88 shows a smaller range of grain forms based around irregular nuggets with complex morphologies. Rounding and folding of the grains is more widespread than in the previous sample and surfaces show fine scratching and smoothing in all cases. Plate 9 shows a grain with a complex morphology, where originally protruding growths have been folded back onto the main grain body this contrasts with the flat, regular forms seen in grains from MA 86.

Sample MA 89 consists of equant nuggets and elongated grains with irregular forms. Surface structures are irregular but show little evidence of dendritic or sponge-like textures seen previously and are taken to represent original surfaces forms. Deformation is present as rounding and folding of edge sections whilst high magnification shows evidence of minor smoothing having occurred. Sample MA 90 contains grains with irregular forms dominant and remnant surfaces textures apparent in most cases. Grains show crystal imprints and impingement structures alongside the usual dendrite derived textures. All these samples lie in close proximity to the Raub mine and the preservation of fine surface detail seen is typical of alluvial gold close to its original source. The difference in morphology seen in sample MA 88 relative to the others may indicate two morphological populations within the deposit.

20 km south of Razib - MA 93, MA 94, MA 95

Sample MA 92 contained insufficient gold for analysis.

Gold sampled from this region shows similar morphological characteristics across all the samples obtained. Grains are typically irregular nuggets with rounding and folding of edges a common feature. Gold from MA 93 differs from the other samples in that

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the grains show some relict structures at high magnification and around half the grains show trapped or embedded minerals within them. These features are not seen in gold from the other two samples though the surfaces are irregular at high magnifications. High magnification reveals all the grains sampled to show smoothing of surface features, though to a lesser extent in MA 93. The gold morphology seen in these samples is typical of gold at considerable distances from its origin. The overall form is tending towards rounded nuggets where the surfaces have been smoothed of protrusions and surfaces features by prolonged abrasion, as the grains are carried downstream.

10 km north of Raub -MA 100, MA 101, MA 102

Gold from these samples shows a wide range of elongate and nugget grains with irregular forms. Grains seen in MA 100 are predominantly elongate in form, with most grains being folded and showing sub-rounding of protrusions. The gold shows crystalline shapes retained in the surface where grains have impinged on other minerals during growth, and grain surfaces are smooth at high magnification where deformation is absent. The gold from sample MA 10 1 shows a higher level of deformation than MA 100 and is a mixture of elongate and nugget forms, some of which show surface coatings of iron oxides. Deformation is higher among the nugget shaped grains which show rounded and folded edges and flattening of their vertices. Grain surfaces are irregular throughout and surface deformation has removed most original surface features. Sample MA 102 shows the highest level of deformation seen for this region with many grains being flattened and having high levels of surface deformation. The grain forms show high levels of rounding and abrasion as seen in Plate 10. This elongate grain has a rounded perimeter, with folding of thin edge sections with flattening and abrasion of the grain surface evident. These features indicate gold at some distance from its source.

4.1.2 Size and shape analysis.

Measurement of the size characteristics of the samples was performed using a petrological microscope coupled to a video camera to capture images for input to the image analyser. The samples were mounted on microscope slides and the microscope operated in transmitted light mode to provide silhouettes of the grains for image analysis purposes. The grains were mounted such that their two major axes lay in the image plane of the microscope so as to present the largest possible cross-section to the analyser. This was done to maximise the validity of data obtained by a 2-dimensional technique operating upon 3-dimensional subjects. The image analysis routine

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developed features individual grain identification, allowing size and shape data to be cross-referenced to results obtained by EPMA. It is then possible to explore correlations between sample populations suggested by chemical and morphological techniques. Results are listed in Tables (9-17).

The size characterisation was made by measuring area, DMAX, DMIN, perimeter, FCIRCLE and FSHAPE for each grain in the sample. These are segregated into primary measurements which are taken directly from the grain and derived measurements, calculated from the primary measurements.

DMAX and DMIN are the maximum and minimum diameters of a grain automatically selected from 32 measurements of the grain diameter made at an angular resolution of 5.7”. FSHAPE is a simple aspect ratio for the grain arrived at by division ofthe minimum diameter by the maximum diameter of the grain. Objects with low values of FSHAPE have elongate shapes whilst high values signifL objects which are equant. The function FCIRCLE is a measure of the circularity of the grain, defined by the equation

FCIRCLE =AzAREA

PERIM~

where a circle returns the value 1. In addition to indicating the circularity of the object, FCIRCLE is also a function of the edge roughness. This plotted against FSHAPE provides a basic morphological characterisation. For example consider a set of grains where the aspect ratio (FSHAPE) remains approximately constant but the value of FCIRCLE decreases. This behaviour represents a population where the general shape of the grains remains the same but the irregularity of their perimeters is increasing.

Analysis of the size data obtained was made by plotting the data sets in the form of “S” curves, constructed by plotting the data in ascending value order for each of the samples. Interpretation of these was based upon different populations within a sample plotting as lines of different slope.

Luie River & Raub Valley - MA 97 & MA 86-91.

Gold from the Luie River location (Table 14) is fine grained with a size range of

0.022 - 0.08 3 mm2 with the majority in a single population with a few larger grains. The plot of aspect ratio against circularity shows a wide spread of grain morphologies

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from equant to elongate (FSHAPE < O S ) , with the majority of the grains showing irregular perimeters. The samples from nearby Raub Valley all show a similar main

size range from 0.017 mm2 to approximately 0.10 mm2. Each sample is dominated by grains from this range, with less than 10% having larger sizes. The aspect ratio/circularity plots for these locations show similar trends throughout and the data spread is close to that seen for the Luie River sample. Thisc;Msistenr,y 0 k r i u u l q . x s s e e n i n t h e d a t a v e of thes;la s € q x m m & y ~ ~ d s m ~ m m

m t h e r m d t h t d l a w c l o s e to theirsnurr;e j n t i C X W Z l S e % h B - sit.

20 km south of Raub - MA 92, M A 93, MA 94, MA 95

The gold sampled from these distal locations is very fine with a size range across the

samples of 0.010 - 0.090 mm2, within which approximately 95% of the grains have

areas below 0.060 mm2. The size data plots show evidence of two differing grain size populations present with a minor population of larger grains. The aspect ratio/circularity plot shows a distribution of grain forms lying in the equant to mildly elongate zone of the plot (FSHAPE values >0.5) and ranging from smooth to irregular outlines. This spread of points is more constrained than that seen for the alluvial sites closer to the mine location. The smaller spread of points seen in the shape data for the distal grains represents erosion of the individual characteristics of the grain shapes and the imposition of a general rounded, equant morphology by the mechanical effects of the alluvial transport.

I0 km north of Raub MA 100, MA 101, M A 102

The size data for the gold sampled from these locations shows differing size populations present within locations and three possible populations present for the

region. Sample MA 102 contains the smallest grains, with average size 0.02 mm2 and

size range 0.012 - 0.066 mm2. The average grain sizes of samples MA 100 and MA

101 are 0.07 mm2 and 0.08 mm2 respectively and both are dominated by grains with

areas < 0.1 mm2 despite having respective ranges of 0.026 - 0.134 mm2 and

0.03 3 - 0.2 13 mm2. The sample populations seen within the region split into three major ranges if the datasets are combined on a single plot (not shown here). The lowest size range is composed mainly of grains from sample MA 102 whilst the middle and upper ranges are composed evenly of grains from the two remaining sites. This may indicate a geographical control on the gold deposited at the sites within the region

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as it is unlikely to be a bias in sampling between locations towards differing grain sizes as all samples were collected by the same panners.

The aspect ratio/circularity data for the samples show three significantly different data spreads. The MA 100 data points show trends generally seen in alluvial samples: points pass from the lower edge of the ‘equant & smooth’ quadrant of the plot into the ‘elongate & irregular’ quadrant. The point distribution for sample MA 10 1 is biased towards equant forms with moderately irregular perimeters with the majority of grains having FSHAPE >O. 5 . Data for sample MA 102 show two shape populations present. The first is clustered in the centre of the upper half of the plot similar to that seen for MA 101 whilst the second is clustered in the ‘elongate & irregular’ quadrant showing a population of elongated grains. Combining the datasets shows the data for MA 100 and MA 10 1 to overlap indicating similar populations whilst the data for MA 102 show little overlap with these but links into the lower end of the combined curve to form a continuous grain-size series. The combined dataset (not shown here) has inflections at

approximately 0.04 mm2 and 0.10 mm2 suggesting three size populations for gold grains in this area.

4.2 Electron microprobe analysis

An analysis was made in the core of each gold grain and, if a rim or other feature such as a white patch could be distinguished optically once the grain had been carbon coated, this was also analysed. Any sulphide, selenide and telluride mineral inclusions were also analysed. Silicate inclusions, principally quartz but also orthoclase and rutile, were observed and their identities checked by qualitative analysis but these inclusions were not quantitatively analysed.

4.2. I Quantitative electron microprobe analysis The results of the gold analyses for each sample are presented in Tables 18-33. The gold analyses from each sample are plotted as an “S” curve of the silver content. The alluvial gold grains have been analysed for a range of elements and the only major constituent apart from gold is silver. No systematic pattern of minor element variation has been detected.

Mine mea Trace element contents in the gold are generally low, at or below detection limits, but some Bi (up to 0.14% ), Cu (up to 0.26 ), As (up to 0.21% ), Sb (up to 0.88% ), Te

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(up to 0.25% ) and S (up to 0.15%), were detected. Hg contents are also generally <1 .O wt% but one point, from the rim of a grain in sample MA 88, gave a value 33.70 wt%, most probably reflecting anthropogenic Hg contamination from alluvial mining. Fineness values range from 846.44 up to 1000.

MA 23 This is a table concentrate of weathered overburden ore and hence similar to soil gold 35 analyses were obtained from gold in this sample. The Ag “S” curve shows three distinct populations, one with 1.49-2.54, another 3.25-4.91 with and the third with 6.42-8.19 wt% Ag. This near surface oxidised ore shows no evidence of very pure (<0.5 wt % Ag) secondary gold formation despite some grains showing Fe oxide coatings resulting from supergene processes.

MA 86 25 analyses were obtained from gold in this sample. The Ag “S” curve again shows three distinct populations, one with 1.17-2.79, another 3.36-4.77 with and the third with 5.54-9.77 wt% Ag.

MA 87 10 analyses were obtained from gold in this sample. The Ag “S” curve shows one main population, with 3.69-4.04 wt% Ag, together with 2 other samples showing lower values of 0.27 and 2.63 wt% Ag respectively, the former indicating secondary gold formation.

MA 88 18 analyses were obtained from gold in this sample. The Ag “S” curve again shows three distinct populations, one with 1.3 1-1.74, another 2.94-7.19 with and the third with two samples of 9.23 and 15.21 wt% Ag.

MA 89 18 analyses were obtained from gold in this sample. The Ag “S” curve again shows three distinct populations, one with 0-1.68, another 3.04-5.76 with and the third with 6.96-8.69 wt% Ag. Low Ag contents most probably reflect secondary alteration and gold precipitation.

MA 90 18 analyses were obtained from gold in this sample. The Ag “S” curve shows two main populations, one with 0-0.73, and the other with 3.46-4.66 wt% Ag. A third sub- population with two samples of 1.20 and 2.07 wtY0 Ag is also present. Low Ag

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contents most probably reflect secondary alteration and gold precipitation and this is the only sample from Raub with significant secondary gold.

MA 91 Only two analyses were obtained from this sample.

MA 97 13 analyses were obtained from gold in this sample. The Ag “S” curve shows three main populations, one with 2.36 - 3.68, the second with 4.45 - 5.40 and the third with 7.26 - 9.26 wt% Ag.

MA 98 11 analyses were obtained from gold in this sample. The Ag “S” curve shows one main population, with 6.35 - 9.1 1 wt% Ag. One sample point gives a much lower Ag content of only 1.52 wt%.

South of Raub mine area Trace element contents in the gold are generally low, at or below detection limits, but some Hg ( up to 0.61% ), As (up to 0.21% ), Te (up to 0.17% ) and S (up to 1.12%), were detected. Fineness values range from 610.3 up to 1000.

MA 92 8 analyses were obtained from gold in this sample. The Ag “S” curve shows three main populations, one with 0-7.52, another with 14.25-16.4 and a third with two samples of 32.43 and 38.72 wt% Ag although the wide range of compositions and small number of samples makes interpretation difficult.

MA 93 15 analyses were obtained from gold in this sample. The Ag “S” curve shows four main populations, one with 4.60 - 5.03, another with 6.59 -7.54, a third with two samples of 10.95 and 11.09 and a fourth also with two samples of 12.27 and 12.41 wt% Ag.

MA 94 8 analyses were obtained from gold in this sample. The Ag “S” curve shows two populations, one with 11.12 - 16.9, the other with 32.62 - 33.69 wt% Ag.

20

MA 95 7 analyses were obtained from gold in this sample. The Ag “S” curve shows two main populations, one with 24.24 - 24.52, the other with 28.12- 28.46 wt% Ag as well as a single grain with 14.78 wt% Ag.

North of Raub mine area Trace element contents in the gold are generally low, at or below detection limits, but some Hg ( up to 0.47% ), As (up to O.% ), Te (up to 0.16% ) and Cu (up to 0.18%), were detected. Fineness values range from 710.5 1 up to 1000.

MA 100

23 analyses were obtained from gold in this sample. The Ag “S” curve shows three main populations, one with 0 - 0.71, the second with 3.20- 4.92 and the third with 7.02 - 10.30 wt % Ag. A single grain with 10.30 wt% Ag is also present.

MA 101

6 analyses were obtained from Au in this sample. The Ag “S” curve shows only one population with 5.19 - 7.78 wt % Ag.

MA 102 49 analyses were obtained from Au in this sample. The Ag “S” curve shows up to seven possible separate populations: 1) 0 - 0.76 wt%, 2) 2.01- 2.35 wt%, 3) 3.89 - 4.99 wt%, 4) 6.62 - 8.41 wt%, 5 ) 9.80 - 11.48 wt%, 6) 13.42 - 18.14 wt% and 7) 27.99 - 29.03 wt%. These can be simplified into three main groups, < I wt% Ag, 1-10 wt% Ag and>lO wt% Ag.

4.2.2 Inclusions in gold grains Analysis of inclusions in the gold grains presented problems due to their small size, often less than 5 microns in diameter. When the electron beam of the microprobe hits the inclusion it penetrates to a depth of several microns and generates X-rays from a volume that can be larger than the inclusion being studied. It has been assumed that all of the gold is contamination and from these analyses a corrected analysis has been calculated using the gold : silver ratio determined in the core analysis of the same grain. The appropriate amount of silver has been subtracted from that measured and any remaining amount has been shown in the column labelled Ag. resid. Atomic proportions of the inclusion analyses have been calculated and are given in Table 34. The EPMA analysis are listed in Table 35. These tables also include possible mineral identifications derived from the atomic proportions. Wherever possible, “common” minerals have been assigned to the inclusion analyses. Inclusions are not common in

21

the Raub alluvial gold and only a few grains from samples MA 86, 88, 89, 92, 100 and 10 1 yielded inclusions for analysis. The majority of the inclusions were pyrite (52%), followed by arsenopyrite and gersdorffite (1 7.5% each) and minor chalcopyrite and tetrahedrite (6% each).

4.2.3 Summary The combined Ag “S” curve plots for the three alluvial gold areas are shown in Figure (5) . The samples from the area around the Raub mine show a generally flat slope, with numerous inflections indicating sub populations, with a maxima of about 10 wt% Ag except for two grains with higher Ag contents. The bulk of the samples however have Ag contents < l O w t %. The data for the sites north of the Raub mine have a steeper, but similarly inflected, slope than the mine alluvial gold and extend to a higher maximum value of circa 30 wt % Ag. Again the bulk are less than 10% similar to the mine gold with a population of samples with Ag contents > 10%. The samples from south ofthe Raub mine area show the steepest slope with over two thirds of the samples having Ag contents > 10%, up to a maxima of nearly 40 wt %, distinctly different from the mine area. The samples from the north have many similarities to the mine area with a distinct additional Ag-rich componant that is dominant in the gold to the south.

The samples from north and particularly those to the south of the Raub mine area are clearly derived from a source with a much broader range of Au compositions than the samples Prom the vicinity of the mine itself This most probably indicates the increasing incorporation of gold from a source distinct from the Raub mineralisation, in the area to the south of the existing mine. A minor component of this “high Ag” style of Au mineralisation is also present in the drainage to the north of the Raub mine area. As in the bedrock gold, there is no obvious correlation between trace element abundances and Au composition although some of the alluvial samples do have high Hg contents, possibly related to anthropogenic contamination associated with alluvial mining. Inclusion suites are dominated by pyrite with minor arsenopyrite, chalcopyrite and tetrahedrite. Gersdorffite is only found as multiple inclusions within one grain.

5. COMPARISON OF BEDROCK AND ALLUVIAL GOLD

5.1 Comparison of gold compositions The silver contents of the bedrock and alluvial gold samples from the mine area are compared by use of cumulative frequency “S” curves, illustrated in Figure (4). The most striking feature is the close similarity in both the shape, inflections and values of silver content for both the bedrock and alluvial gold from the main Raub mine area. The minor discrepancies in Ag content between bedrock and alluvial samples can be

22

explained by the presence of late stage Au rich rims and Ag rich tracks in the alluvial grains as were also observed in samples from Lubuk Mandi (Henney et al. 1994). It is clear that the majority of analyses from both alluvial and bedrock gold from the mine area are very similar. The data in Tables 18-33 show that there is a slight enrichment in Hg content in the alluvial grains compared to the bedrock, this most probably reflecting anthropogenic Hg contamination in the stream environment as observed in other areas (Callahan et al., 1994). The Ag “S” curve data for samples from drainage basins to the north (MA 100-1 02) of the mine area, although showing a preponderance of compositions broadly similar to the Raub mine samples, do include a component of Au with higher Ag contents. The samples from drainage systems to the south (MA 92-95) of the Raub mine with the majority of samples of alluvial gold from this area containing high Ag gold, show little similarity to the samples from the mine area. This indicates a source of Au and style of Au mineralisation, particularly in the south, which is distinct from that observed at Raub mine.

5.2 Comparison of mineral inclusions Sulphide inclusions in gold are not abundant in the Raub area. The main sulphide mineral inclusions found within the bedrock gold are arsenopyrite and pyrite which are also the most common within the alluvial gold samples. Gersdoflite, tetrahedrite and chalcopyrite are also found in the alluvial gold. Gersdoflite has not yet been observed as inclusions in the bedrock samples and was only found in one grain taken from a stream draining into the mine area, thus it must be assumed that this grain must be derived from another mineralisation source outside the Raub mine. Experience elsewhere suggests gersdoflite is found in gold associated with mafichltramafic rocks, suggesting another minor source in the Raub area.

5.3 Morphology As detailed in section 4.1, the alluvial grains collected from sites proximal to the mine have a wide range of morphologies, but no systematic differences are apparent between sample sites. The more distal grains collected from sites south of the mine site are generally smaller in size and show greater rounding and deformation consistent with increased transport distances in the fluvial system. Data for grains from sites 10 km north of the mine site do show some evidence for three size populations but these do not appear to correlate with compositional variations and may reflect local variations bedrock gold morphology and fluvial transport mechanisms.

6. SUMMARY AND CONCLUSIONS

1. Samples of bedrock gold were collected from the Raub deposits. Complementary

23

samples of alluvial gold were collected from sites up to several km away from the primary source. This provided good material to test which features of alluvial gold are inherited from the bedrock source and which are altered during weathering and erosion in the tropical rain forest environment of Peninsular Malaysia.

2. Alluvial gold grains close to the mine show a generally elongate morphology with highly irregular edge profiles and complex shapes reflecting their original forms within the bedrock deposit. The low level of deformation seen in the samples is typical of alluvial gold in close proximity to the bedrock source. Gold grains collected from more distal sites, up to 20 km away from the mine, are generally smaller and more rounded.

3 . The bedrock gold from Raub is characterised by Ag contents between 1.5 and 9

wt% with multiple populations in some cases within a single sample. Some samples have higher mean Ag contents which may reflect some small compositional variation within the deposit. Trace element contents are generally low, although there is some variation in Hg, As, Cu, S , Sb, Bi, Te and Fe contents above the detection limits (c. 0.1%). This may be due to (i) Hg solid solution in gold and (ii) micro inclusions of sulphides within the gold.

4. Ag contents in alluvial gold range up to 40 wt%, but the majority of samples from both the mine area and drainage systems to the north have values 4 0 wt%. Samples from drainage systems to the south of the mine area show a significant number of grains with higher Ag contents which are distinct from those recorded from Raub. These are most probably derived from a source distinct from the Raub mineralisation suggesting that hrther Au mineralisation may exist to the south of the Raub area. The small population of higher Ag values within the Raub mine samples are possibly due to the presence of late stage or secondary Ag-rich tracks along subgrain boundaries within the gold. The small population of low Ag values are found in Au-rich rims and films within and around the grains, indicating minor deposition of pure secondary gold in the near surface environment. The presence of high Hg values in rims on some of the alluvial grains indicates the influence of alluvial mining where mercury is used for gold extraction. Some mercury has been released from these workings and has modified the composition of some of the alluvial grains.

5. Studies of the micro-inclusions in alluvial gold show that pyrite is the most abundant inclusion comprising 52% of the population. Arsenopyrite (1 7.5%),

gersdoflite (17.5%), chalcopyrite (6%) and tetrahedrite (6%) are also present. Pyrite, arsenopyrite and chalcopyrite are typical of mesothermal shear zone deposits, while

24

tetrahedrite is a particular feature of the Raub deposit. The presence of gersdoflte in one sample suggests a minor component derived from a source associated with mafic rocks.

6 . At Raub the mineralogical, chemical and morphological characteristics of the bedrock gold are largely preserved through the weathering cycle and are inherited by the alluvial gold recovered from sites close to the bedrock deposits. Gold recovered from sites 20km to the south show an input from a more Ag-rich style of gold mineralisation distinct from that observed at Raub, possibly a lower temperature “epithermal” type of mineralisation.

7. Further transport in the alluvial system will modi@ the shape of gold grains and possibly cause some change in composition to the outer rims. Many features such as internal composition and micro-inclusions that are protected by the gold are unlikely to be substantially changed. Therefore the characteristics of alluvial gold from more distant sites can still be used to characterise the bedrock source as well as reveal inputs from other styles of Au mineralisation.

8. The composition of gold and minerals associated with the gold mineralisation can be identified from the alluvial gold grains. Firstly this information can be used to deduce if more than one source is represented in the alluvial gold population. Secondly, in broad terms, the type of gold deposit can be recognised from the included minerals and from this possible source areas in the major catchment can be identified from known geology. In the case of the Raub mineralisation this is a shear-zone type deposit and structural features will be a major factor in the control of gold mineralisation.

7. ACKNOWLEDGEMENTS We would like to thank Mr A G Gunn and the ODA GSMBGS gold project for assistance in planning, conduct and discussions connected with this work. We thank Mr Rohimi bi Che Wan and staff from GSM Kuantan for guidance and extensive support for the field sampling programme. We thank the manager of the Kim Chuan gold mine, Raub, for access to the mine and providing us with many bedrock gold samples.

25

8. REFERENCES

Callahan , J.E., Miller, J.W. & Craig, J.R. 1994. Mercury pollution as a result of gold extraction in North Carolina, U.S.A. Applied Geochemistry. v.9, p235-242.

Cobbing, E.J., Pitfield, P.E.J., Darbyshire, D.P.F. and Mallick, D.I.J. 1992. The granites of the South East Asian tin belt. Overseas Mem. Brit. Geol. Surv. No. 10.

Groen, J.C., Craig, J.R. & Rimstidt, J.D. 1990. Gold-rich rim formation on electrum grains in placers. Canadian Mineralogist .v.28, p207-229.

Gunn, A.G., Halim bin Hamzah, Ab. and Ponar Sinjeng, P. 1993. Geochemical and mineralogical studies at the Kim Chuan gold mine, Raub, Pahang, Malaysia. Geological Survey of Malaysia - British Geological Survey Gold Sub-Programme Report 93/3 pp46.

Henney, P.J., Styles, M.T., Wetton, P.D. and Bland, D.J. 1994. Characterisation of gold from the Lubuk Mandi area, Terengganu, Malaysia. British Geological Survey Technical Report WC/94/2 1.

Hutchison, C.S. 1989. Geological evolution of South East Asia. 368pp (Oxford: Clarendon Press).

Richardson, J.A. 1939. The geology and mineral resources of the neighbourhood of Raub, Pahang, Federated Malay States, with an account of the geology of the Raub Australian Gold Mine. Geol. Surv. Dept. Fed. Malay States, Memoir 3.

26

granitoid %> .... >... . . .

0 SINGAPORE 1

Figure 1 . Map of peninsular Malaysia showing the locations of the Raub area and other primary gold occurrences.

7,- -

- - a

\

I ! 42900

LEGEND RAUB GROUP (Triassic)

Mining area Shale, siltstone

BENTONG GROUP (Devonion

0 Sandstone and older)

Conglomerate

Road

+ Sample site

0 1 Chert

U kilometre

BUKlT W A N G FORPHYW (Triassic)

Granite porphyry

Figure 2. Simplified geological map of the Raub area showing alluvial gold sample sites.

s 3 c

m a

8 -

7 -

6 -

5 -

9 1

4 - i

0 0 2 5 5 0 7 5 1 0 0 1 2 5

Number Figure 3. Bedrock gold "S" curve for the Raub area.

1 2

1 0

8

6

4

0 Raub Mine Bedrock

0 Raub Mine Bedrock

Raub mine Alluvial

0 2 5 5 0 7 5 1 0 0 1 2 5 Number

Figure 4. Comparison of alluvial and bedrock "S" curves for the Raub mine area.

4 0

3 0

s 4- 2 0 3 m a

10

0

L4 A 0 A

0

Number Figure 5. Alluvial gold "S" curves for the Raub area.

4 0

3 0

s 3 2 0 CI

m a

1 0

0

A A A

0

0 0 2 5 5 0 7 5 1 0 0 1 2 5

Number

0 Raub mine alluvial

0 South Raub alluvial

A North Raub alluvial

Raub Mine Bedrock

0 Raub mine alluvial

0 South Raub alluvial

A North Raub alluvial

Figure 6. Comparison of bedrock and alluvial "S" curves from the Raub area.

Table 1 SAMPLES FROM THE RAUB AREA

Ag "S" curve

: I l ! i i l , 0

0.00 5.00 10.00 15 .00 20.00 25.00 30.00

Number

Table 2 EPMA data and "S" curve for bedrock samples M A l d l b

8.00

6.00 7.00 i p 3.00

1 .oo 0 . 0 0 2.00 0.00 L 1 1 1

5.00 10.00 15.00

Number

Table 3 EPMA data and "S" curve for bedrock samples MA2d2b

Ag "S" curve

8 . 4 0 T

+ 7.40 I 7.60 tnoo I I

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00

Number

Table 4 EPMA data and "S" curve for bedrock sample MA25

8.00

7 .00

6.00

F :::: m a 3.00

2.00

1 .oo 0.00

Ag "S" curve

0 n O 0

0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0.00 5.00 10.00 15.00 20.00 25.00

Number

Table 5 EPMA data and "Sv curve for bedrock sample MA36

Table 6 EPMA data for bedrock sample MA38

3.: i 3

U 1.5

0.: { 0

0

Ag "S" curve

0 U 0 0

0 0

1 , I 1 + i 1 2 3 4 5 6

Number

Table 7 EPMA data and "S' curve for bedrock sample MA39

Ag "S" curve

5.30

5.20 5.10

5.00 $ 4.90 c,

3 4.80 P 4.70

4.60 4.50 4.40

4.30

-

~~

--

--

0 --

--

~~ n o o n -~

--

--

I a----

Number

-a--- 15 20

Table 8 EPMA data and "S" curve for bedrock sample MA1 27

I MA86.22 10.027 I 0.263 10.167 I 0.861 I 0.460 I 0.634 I

10 MA86 0 MA87 1

0.35 0'40 I - E 0.25 0.30 t g 0.20 +

0.15

0.10

0.05

0.00

a

0

0

0

0

0 10 20 30 40

Count

0.8

0.6

0

0 10 20 30 40

Count

0.60 i E 0.50 E - 0.40

0.30 a

0

cd" 0

0

0.20

0.10

0.00 ~ i

0 10 20 30 40

Count

1 .o

0.8 1' 2 0.4 !i O ' I

Equant &

0

0.2 + I Elongate & I

0.0 0.0 0.2 0.4 0.6

FCIRCLE

- 0.8 1.0

Table 9 Shape data, FSHAPE and area "S" curves for

alluvial samples MA86 & 87

DMAX I DMlN I PERlM 1 FCIRCLE I FSHAPE NAME I AREA I DMAX 1 DMlN I PERlM I FCIRCLEI FSHAPE

0.31 4 10 .224 I 1 .I 1 8 I 0 .452 I 0.71 3

0.401 10.21 4 I 1.431 I 0 .347 I 0 . 5 3 4

0.472 10.250 I 1.545 I 0.41 0 1 0 .529

0 .433 10.333 I 1 .563 I 0.41 3 I 0.769

MA88.13 10.049 10.306 10.232 10.91 1 I 0 . 7 4 4 I 0.757

MA88.14 IO.091 10.519 10.283 1 1 .686 I 0 .404 I 0.546

MA88.29 10.051

MA88.30 I 0 . 0 5 8

0 .394 10.21 9 I 1.265 1 0 .399 I 0.557

0.368 10 .264 I 1 .470 I 0.335 I 0.71 9

MA88.15 10.076 10.535 10.21 0 I 1.401 I 0.485 I 0 .392

MA88.16 10.065 10.347 10.278 I 1 .224 I 0.544 I 0 .802

0 . 3 1 9 ~ 0 . 2 4 8 ~ 1 . 1 3 1 I 0.505 1 0 .779

0.31 1 10.238 10 .968 I 0.602 I 0 .765

MA88.17 10.068 10.367 10.265 I 1 .482 I 0.391 I 0 .724

MA88.18 10.052 10.357 10.223 I 1 .I 15 [ 0 .527 I 0 . 6 2 3

MA88.19 10.052 10.338 10.228 I 1 . 1 13 I 0 .532 I 0.675 MA88.20 10.079 10.456 10.256 I 1 .269 I 0.616 I 0 .561

I MA88.21 10.056 10.428 10.222 I 1 .277 I 0.431

0 .20 0.80 0

0.15 0.60 E E E

E

U I P

- 0.40 & 2 0.10

m 0

G 0 .05 T 0.20 1

0.00

0 10 20 3 0

Count

40

__

0 1 0 20 3 0 40

Count

0.5 T

t 0 .2 1 Elongate &

0.

FClRCLE

0.0 L- 1 I

0 10 20 3 0

Count

i

40

Table 10 Shape data, FSHAPE and area "S" curves for alluvial sample MA88

MA89.18 10.076

0.326 10.284 I 1 . I76 I 0.595 I 0.871 0.479 I0 .310 12.674 I 0.125 I 0.648 0.547 10.220 I 1.761 I 0.306 I 0.402

0.10

0.08 - E E 0.06 U -

0.04 a

0.02

0.00

P #

@n

P

0 10 20 30

Count

0.40

0.30 - E E

z -

0.20

E 0.10

D

0.00

0 10 20 30

Count

MA89.29 10.041 10.341 MA89.30 10.056 10.338

- DMlN 0.135 -

0.269

0.219

0.205 0.208

0.164 0.199 0.246

- - - - - -

MA89.31 0.039 0.368 0.179

MA89.32 0.033 0.239 0.194 MA89.33 0.039 0.264 0.210

MA89.34 0.032 0.344 0.139

0.50 o'60 T

0.00 O . I 0 L 0 10 20 30

Count

1 .o

0.8

0.6 P

U) i

0.4

0.2

0.0

Elongate & Irregular

0.0 0.2 0.4 0.6 0.8 1.0

FCIRCLE

Table I 1 Shape data, FSHAPE and area "S" curves for alluvial sample MA89

NAME MA90.1

MA90.13

MA90.14 MA90.15 MA90.2 MA90.3 MA90.4

MA90.10 MA90.5 MA90.6 MA90.7 MA90.8 MA90.9

MA90.11 MA90.12 MA91.1

- AREA 0 . 1 7 6

0.021 0 . 0 1 6

0 . 0 0 4

0.272 0.040 0.037 0.030 0.033

10.071

E 0.20 0'30 I h

U v) v

0

0

m

a

-~ - ._ 0.00 O . I 0 L 0 10

Count

--I

20

0.4 0.5 _I

E

z n

0.1 4

0

0

0.0

0 1 0 20

Count

0.80 5 0 0

A

E E 0 . 6 0

X v

2 n 0.40 0.20 If""' 0.00 0-

0 1 0

Count

1

20

.. ~

Irregular 0.8

0 n

"93

0.0 0.0 0.2 0.4 0 .6 0.8 1.0

FCIRCLE

Table 12 Shape data, FSHAPE and area "S" curves for alluvial samples MA 90 & 91

0.08

I

0 10 20 30 40 5 0

Count

0'3 0.3 I B U

I

- 0.0 c-+-+- 0 10 20 30 40

Count

i

50

0.50

0.40 E E 0.30 - :: 0.20 E n

0.10

0.00 0 10 20 30 40

Count

Equant 8 Irregular

1.

0.6 I 2 0.4

0.2

o, irregular

a

Elongate 8

I

0.0 0.2 0.4 0.6 0.8 1.0

FCIRCLE


alluvial samples MA92, 93, 94 8 95

t?Y?Y? MA97.9 0 059 0 371

MA97.15 10.083 I 0 498

MA97.24 10 022 I 0 215

DMlN I PEWM I FCIRCLE I FSHAPE

0 268 1 2 4 4 0 730 0 138 1 040 0 335 0 2251 1 257 I 0 460 1 0 540 0 1921 1 1 1 1 I 0 4 3 7 I 0 5 0 8 0 2821 1 774 I 0 330 I 0 565 0 2301 1 500 I 0.338 I 0.498 02541 1 1 7 5 I 0 5 8 6 I 0 7 2 0 0 3081 1 267 I 0 590 I 0 805 0 1961 0 866 I 0 589 I 0 631 0 2281 1 125 I 0 532 I 0 663 0 1951 1 374 I 0 425 I 0 376 -1 0 145 0 627 0 706 0 677 0 2331 1 447 I 0 360 I 0 556

0 2001 1 189 I 0 350 I 0 496 02181 1 0 1 1 I 0 4 7 1 I 0 7 8 9 02281 1 1 2 9 I 0 4 9 8 I 0 6 9 5 0 235 0 966 0 580 0 852 0 2201 1 0 1 2 I 0 5 0 9 I 0 7 5 6 I

T 0 08

E 5 0 06

(II 0 04 E!

0 0 2

Ill - I 0 0 0 ~ i

0 10 20 30

Count

0 40 7

0 30 1

E E - 0 20 z E

0

0.10 1 0 00

0 10 20 30

Count

0 60 T

0.00 O . I 0 i 0 10 20 30

Count

$ O 6 I 0 4

Elongate & Irregular

0 0 0 2 0 4 0 6 0 8 1 0

FCIRCLE


MAIO0.22 MA100.23 MA100.24

0.087 0.456 0.336 1.656 0.397 0.736 0.043 0.315 0.227 1.029 0.505 0.721 0.032 0.456 0.121 1.158 0.295 0.264

MAlOO.17 10.047 I 0.370 10.203 MA100.18 10.026 10.283 10.142 MA100.19 10.029 10.295 10.141 I 0.901 MA100.20 10.045 I 0.377 10.192 1 1.240

0.441 I 0.479 I 0.369 I 0.511 I

I MA100.21 10.106 10.550 10.2841 1.712 I 0.454 I 0.515 I

0.14

0.12

0.60

0.50

0 0

- 0.10 E E 0.08 P

2 0.40 E

0.30 - a 2 0.20

- 0.06

e a 0.04

0.00 0 5 10 15 20

Count

0.10

0.00 I

0 5 10 15 20

Count

1 .o 0.50 7

0.40 0

E 0.30

0.10

Irregular 0.0 0.00 ~ , ! I

0 5 10 15 20

Count

0.0 0.2 0.4 0.6 0.8 1.0

FCIRCLE


alluvial sample MA1 00

NAME I AREA I DMAX I DMlN I PERlM I FCIRCLE I FSHAPE I MAIO1.l 10.069 I 0.459 10.254 I 1.493 I 0.388 I 0.554 I

NAME AREA I DMAX DMlN I PERM I FCIRCLE I FSHAPE I MA1 01.20 0.078

0.050 0.051 0.100 0.060

- - - - -

0.448 0.321 0.346 0.507 0.348

- - - - -

0.2531 1.354 1 0.537 I 0.564 0.2281 1.106 I 0.510 I 0.711

0.4361 2.257 I 0.417 I 0.758 0.3051 1.597 I 0.472 I 0.669

0.078 0.072 - -

0.428 0.385

MAIOI.11 IO.112 I 0.546 10.3951 2.257 I 0.276 I 0.724 I I MA1 01.30 MA101.12 10.0841 0.383 10.3221 1.428 I 0.520 I 0.840 I I MA1 01.31

0.25

~ 0.20 T 0.80

0.60

0

I 0 E E 0.15

4 0.10 ?! U

U - - E

0 10 20 30 40

Count

0.05

0.00

I 0 10 20 30 40

I Count

0.50 1 .o

0.8

Equant 8

0

0

Irregular i

0.40

0.6 n 2 2 0.4

E 0.30

z I 0.20 Q

1

U

0 . 2

0.0

0.10

0.00 ' I

0 10 20 30 40

Count

Elongate 8

0.0 0.2 0.4 0.6 0.8 1.0

FCIRCLE

Table 16 Shape data, FSHAPE and alluvial samde MA1 01

area "S" curves for

1 MA102.19 10.019 I 0.226 10.146 I 0.815 1 0.352 I 0.643 I

0.07

0.06

0.05 - E E 0.04 U

0.03 -

0.02

0.01

0.00

2

0 10 20 30 40

Count

0.25 0.30 I

0'05 0 .00 L-+---- 0 10 20 30 40

Count

0.50

0.40

0.30 -

0 10 20 30 40

Count

Equant 8 Irregular

0 . 0

0.0 0.2 0.4 0.6 0.8 1.0

FCIRCLE


Ag "S" Curve

9

6 0

0 1 1 I

0.00 10.00 20.00 30.00 40.00

Number

Table 18 EPMA data and "S" curve for alluvial sample MA23

Ag "S" curve

0.00

9.00

8.00

7.00

6.00

5.00

4.00

3.00

2 . 0 0

-

--

--

--

~~

--

--

--

-- n o

0.00 I I

0 5 1 0 1 5 20

'.OO L Number

i

25


4.5

3.5 4 f s 2.5 3 4

0.5

0 0 I Ag "S" curve

0

0 1 1 1 1

2 4 6 8 10

Number


16.00

14 .00

12.00

10.00

8.00 s

6.00 2

4.00

2.00

0.00

Ag **S" curve

0

0

0 n o

0

0 5 10 15 20 Number

-~ ~-~


9.00

8.00

7.00

6.00

$$ 5.00

2 4 . 0 0

3.00

2.00

1 . o o

0.00 0 U

0 0

0

0 _____+

5

Ag **S" curve

0 0 0

0

0 0

_____t__

10

Number

1 1

15 20


I I Au

O r C O C i I I , I I I

lMA90/1 I 95.84

IMA90/3 MA90/6

IMA90/26 I 99.43 IMA90/28 I 96.13

lMA90/32 I 99.92

3.36 I I 0.08 I 0.39 I I I I 0.04 I I I I 0.20 I

3.84 0.21 0.07 3.46 0.06

0.30 0.06 0.13 I . . . I I

3.54 I I I 0.19 I I I I I I I I 0.08 I

0.30 I 0.03 I I I I I 0.33 I I 0.55 0.52 0.19 0.61 4.66 I I I 0.22 I I I 2.07 0.11 0.73 0.13

0.35 I I I I 0.07 I 0.08 I

#

€€ 5

4.5

4

3.5

m a 2

1.5

1

0.5

Ag "S" Curve

U

U

U

MA9112 MA9115

Table 24 EPMA data for alluvial sample MA91

Au Ag Fe Cu Hg S As Sb Te Bi Zn Total Fineness 96.94 1.19 0.1 1 98.24 987.88 99.50 0.34 0.1 2 99.95 996.58

MA9216 MA92110 MA92111 MA92115

40

65.80 32.43 0.58 0.12 98.98 669.86 99.40 0.1 7 99.57 1000.00 94.80 2.97 0.07 97.83 969.65 91.20 7.52 0.33 0.1 0 99.15 923.79

35

30

25

9 20 OI

a 1 5

10

5

0 0

Ag "S" curve

0 0

0

2 4 6

Number

a


14.00

12.00

10.00

2 6.00

4.00

2.00

0.00 0

0 n o

-+ 2

0

+ 4

Ag "S" curve

I I I 1 I I

6 8 10 12 1 4 16 Number

rable 26 EPMA data and "S" curve for alluvial sample MA93

35.00

30.00

25.00

E * O . O O

3 15.00

10.00

5.00

0.00

0

0

0

+ 2

Ag "S" curve

0 0 0

4

-

Number

I I

6 8 10 12


30.00

25.00

20.00

9 15.00

10.00

5.00

0.00

0.00

0 0

0

Ag "S" curve

0 0

0

0

I 1 I I I 1 I

1 .oo 2.00 3.00 4.00 5.00 6.00 7.00 Number

Table 28 EPMA data and"S" curve for alluvial sample MA95

10.00

9 .00

8.00

7.00

6.00

5.00

4 .00 3

3.00

2.00

1 .oo

0.00

0

Table 29

Ag "S" Curve

0 0

0

0 I

+ 2 + I 1 I I I

4 6 8 10 12 14

Number

EPMA data and "S" curve for alluvial samole MA97

10.00

9.00

8.00

7.00

6.00

5.00 ' 4 . 0 0

3.00

2.00

1 .00

0.00 0

Ag " S" cu we

U

, , , I I I i

2 4 6 8 10 12

Number


Ag "S" curve

1 1 I o u o o q ~

12.00

10.00

8.00

6.00 m a

4.00

2.00

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onno 000


8.00

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2.00

1 .00

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0

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0 0

U 0

0 1 2 3 4

Number

- 5 6


30 00

25 00

20 00

1 5 0 0

10 00

5 00

ae

2

Number

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d

0 0

0 00

0 00 10 00 20 00 30 00 40 00 50 00


a z > 0 0 C a

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british geological surveybritish geological survey technical report wc/95/20 overseas geology series...

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