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)

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Indonesian Journal on Geoscience, Vol. 1 No. 1 April 2014: 1-7

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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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Gold Phytomining: A New Idea for Environmental Sustainability in Indonesia (B.D. Krisnayanti and C. Anderson)

3

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.

References

Anderson, C., Moreno, F., and Meech, J., 2005.

A eld demonstration of gold phytoextrac-

tion technology.Minerals Engineering, 18,

p.385-392.

Anderson, C.W.N., Brooks, R.R., Chiarucci, A.,

LaCoste, C.J., LeBlanc, M., Robinson, B.H.,

Simcock, R., and Stewart, R.B., 1999. Phy-

tomining for nickel, thalium and gold.Journalof Geochemical Exploration, 67, p.407-415.

Anderson, C.W.N., Brooks, R.R., Stewart, R.B.,

and Simcock, R., 1998a. Harvesting a crop of

gold in plants.Nature, 395, p.553-554.

Anderson, C.W.N., Brooks, R.R., Stewart, R.B.,

and Simcock, R., 1998b. Gold uptake byplants. Gold Bulletin, 32 (2), p.48-51.

Brooks, R.R., Chambers, M.F., and Nicks, L.J.,

1998. Phytomining. Trends in Plant Science,

3, p.359-362.

Dunn, C.E., 1995. Biogeochemical prospecting

for metals,In: Brook, R.R., Dunn, C.E., and

Hall, G.E.M. (Eds.), Biological systems in

mineral exploration and processing, Ellis

Horword, Hemel Hemtead, p.371-426.

Gardea-Torresdey, J.L., Peralta-Videa, J.R., de

La Rosa, G., and Parsons, J.G., 2005. Phy-

toremediation of heavy metals and study of

the metal coordination by X-ray absorption

spectroscopy. Coordination Chemistry Re-

views, 249, p.1797-1810.

Lamb, A.E., Anderson, C.W.N., and Haverkamp,

R.G., 2001. The extraction of gold from plants

and its applications to phytomining. Chemistry

in New Zealand, 3, p.1-33.

Mohan, B.S., 2005. Phytomining of gold. Current

Science, 88 (7), p.1021-1022.

Moreno, F.N., Anderson, C.W.N., Stewart, R.B.,

Robinson, B.H., Ghomsei, M., and Meech,J.A., 2005. Induced plant uptake and transport

of mercury in the presence of sulfur-contain-

ing ligads and humic acid.New Phytologist,

166 (2), p.445-454.

Msuya., F.A., Brooks, R.R., and Anderson,

C.W.N., 2000. Chemiccally-induced uptake

of gold by root crop: its signicance for phy-

tomining. Gold Bulletin, 33 (4), p.134-137.

Robinson B.H., Leblanc M., and Petit, D., 1998.

The potential of Thlaspi cearulescens for

phyto-remediation of contaminated soils.Plant Soil, 203, p. 47-56.

Robinson, B.H., Brooks, R.R., and Clothier, B.E.,

1999. Soil amendments affecting nickel and

cobalt uptake by Berkheya coddii: potential

use for phytomining and phytoremediation.

Annals of Botany, 84, p.689-694.

Schwartz, C., Echevarria, G., and Morel, J.I.,

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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


11/63

Some Key Features and Possible Origin of the Metamorphic Rock-Hosted Gold Mineralization

in Buru Island, Indonesia(A. Idrus et al.)

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


12/63


13/63



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


14/63


14

lena, and sphalerite are rare or maybe absent. In

general, sulphide minerals are rare (


15/63


16/63


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.)


17/63



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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19/63



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


23/63


24

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


24/63


25/63


26

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.


26/63


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


27/63


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



Brachiopods

Moluscs

Ostracods

Sponge-spicules

Bioturbation

Unidentied fossils


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


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


28/63


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



Brachiopods

Moluscs

Ostracods

Sponge-spicules

Bioturbation

Unidentied fossils


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


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


29/63


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


30/63


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


31/63


32

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


Bay

Tidal Flat

Basin

Lagoon

Tidal Channel

River

INVESTIGATED AREA

Slope

BASEMENT ROCKS

N

LOWER PART


Bay

Tidal Flat

Basin

Lagoon

Tidal Channel

River

Regression

INVESTIGATED AREA

Slope

BASEMENT ROCKS

N

BASEMENT ROCKS


Basin

Lagoon

River

Stable landfollowed by erosion

INVESTIGATED AREA

Slope

Figure 13. Photomicrograph of grains

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Indonesian Journal on Geoscience V1 N1 April/May 2014

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