metamorphic hosted low sulphidation epithermal gold … 20120205.pdfmajalah geologi indonesia, ......

Majalah Geologi Indonesia, Vol. 27 No. 2 Agustus 2012: 131-141

131Naskah diterima: 02 Januari 2012, revisi terakhir: 03 Agustus 2012, disetujui 06 Agustus 2012

Metamorphic Hosted Low Sulphidation Epithermal Gold Systemat Poboya, Central Sulawesi: A General Descriptive Review

Sistem Emas Epitermal Sulfidasi Rendah dalam Batuan Metamorf di Poboya, Sulawesi Tengah: Tinjauan Deskriptif Umum

Muhammad Farid Wajdi, STJ. Budi Santoso, Damar Kusumanto, and Sumardiman Digdowirogo

Bumi Resources Minerals, Wisma Bakrie 2, 15th Floor Jln. H.R. Rasuna Said Kav. B-2 Jakarta 12920

ABSTRACTPoboya Prospect is located in Block I of PT. Citra Palu Minerals Contract of Work Generation VI, 12 km northeast of Palu City, Central Sulawesi. The prospect was discovered in 1993 by Rio Tinto. It occurs on the east margin of a major pull-apart basin related to the Palu Koro sinistral strike slip fault system that forms part of the Neogene Northern Sulawesi Island Arc. Mineralization at Poboya is interpreted as a low sulphidation epithermal gold system hosted in/by metamorphic rock units. The vein Zona system comprises a series of gently southwest dipping sheet-like, low sulphidation epith-ermal quartz-carbonate vein Zona. Mineralised quartz-carbonate Au-Ag vein Zona shows epithermal textures such as colloform-crustiform banding, bladed calcite pseudomorphs, chalcedonic quartz, to cocks comb banded quartz with evidence of multiple fluid phases and brecciation. With no volcanics associated and study on alteration assemblages, it is suggested that the best possibility for mineraliza-tion in this area rests with the retrogressive chlorite stage which is likely to have generated its own hot water circulation system as the heat source cooled. The extensive development of low to intermediate grade mineralization Zonas associated with some minor banded chalcedonic quartz-carbonate stock-works with commonly grey sulphide lines at the edge of the veinlets are regularly found adjacent to the main veins and interpreted formed in the same (?) mineralization stage. Further more comprehen-sive exploration work is required and now being undertaken by CPM to get better understanding of mineralization regard to structure, validate the ore bodies model, and reliable resources estimation.Keywords: low sulphidation, epithermal gold system, Poboya, Central Sulawesi

SARIProspek Poboya terletak di Blok I Daerah Kontrak Kerja Generasi VI PT. Citra Palu Mineral, 12 km timur laut kota Palu, Sulawesi Tengah. Prospek itu ditemukan pada tahun 1993 oleh PT. Rio Tinto, dan berada di tepi timur cekungan besar tarik-pisah yang berkaitan dengan sistem sesar mendatar mengiri Palu-Koro yang membentuk bagian busur kepulauan Sulawesi Utara pada Neogen. Mineral-isasi di Poboya ditafsirkan sebagai sistem emas epitermal sulfida rendah yang berinduk pada satuan batuan metamorf. Sistem zona urat terdiri atas serangkaian zona urat karbonat-kuarsa epitermal sulfida rendah berbentuk lembaran yang agak miring ke barat-daya. Zona urat Ag-Au termineralisasi karbonat-kuarsa memperlihatkan tekstur-tekstur epitermal seperti colloform-crustiform banding, bladed calcite pseudomorphs, chalcedonic quartz, hingga cocks comb banded quartz sebagai bukti adanya fasa-fasa fluida berulang dan breksiasi. Ketidakhadiran asosiasi vulkanik dan studi tentang kekerabatan alterasi, menunjukkan bahwa kemungkinan terbaik untuk mineralisasi di daerah ini ter-letak pada tahap retrogresif klorit yang agaknya telah menghasilkan sistem sirkulasi air panas sendiri sebagai sumber panas yang mendingin. Perkembangan zona-zona mineralisasi derajat rendah yang ekstensif hingga menengah berkaitan dengan beberapa jaringan minor urat berupa banded chalcedonic quartz-carbonate yang umumnya bergaris-garis sulfida abu-abu pada ujung-ujung urat-urat halus dan biasanya ditemukan berdekatan terhadap urat-urat utama. Hal ini diinterpretasikan terbentuk dalam tahapan mineralisasi yang sama. Selanjutnya, pekerjaan eksplorasi yang lebih komprehensif


132

diperlukan dan saat ini PT. Citra Palu Mineral sedang melakukannya untuk mendapatkan pemaha-man yang lebih baik mengenai mineralisasi dalam kaitannya dengan struktur, memvalidasi model tubuh bijih, dan mengestimasi sumber daya yang terpecaya.Kata kunci: sistem emas epitermal sulfidasi rendah, Poboya, Sulawesi Tengah

INTRODUCTION

PT Citra Palu Minerals Minerals (PT CPM) Contract of Work (CoW) is located in Su-lawesi, Indonesia (Figure 1), covering a re-tained total contract area of 138,889 hectares made up of five blocks in Central Sulawesi and one block in South Sulawesi. Block I where the Poboya occurs, is the focus of the exploration beside several regional and pros-pect scale exploration programs undertaken by the company. Poboya is administratively situated in Palu Timur Subregency, Palu Regency, Central Sulawesi Province.

REGIONAL GEOLOGICAL SETTING

Sulawesi is situated in the northern Indo-nesian archipelago that is associated with the interaction complex of the Southeast Asian, Pacific, and Indian-Australian plates (Kavalieris et al., 1992). The numerous oc-currences of several precious and base-metal porphyry and epithermal mineralization in Sulawesi are associated with this tectonic setting. The eastern margin of the South-east Asian Plate was involved in at least three major subduction events, which has contributed to the evolution of Sulawesi. The earliest Early Cretaceous event (110 Ma) is represented by basement complexes preserved in southern and central Sulawesi (Kavalieris et al.,1992). The second mid-Oligocene event (28 - 31 Ma) is attributed to blueschist and ophiolite complexes in Eastern Sulawesi (forming the east and southeast arms of the island). In Central Sulawesi, basaltic and andesitic volcanics of the Tinombo Formation, and potentially

coeval basaltic dykes, are also related to this subduction event. The third subduc-tion event during the Lower Miocene (16 - 24 Ma) produced calc-alkaline magmatic intrusions and associated porphyry and epi-thermal mineralization in North Sulawesi (Figure 2).

Carlile (1983) divides Sulawesi into two dis-tinct Zonas; eastern and western geological Zonas.The western Zona is dominated by calc-alkaline volcanic and intrusive rocks of the Miocene magmatic arc. The eastern Zona, including the east and southeast island arms, is characterized by metasediments and ultrabasic units, and obducted ocean floor ophiolites, predominantly related to the second event above. The company’s project areas are located in the western Zona which include the north and south arms of the island and the ‘neck’ of Sulawesi. This Zona hosts several well mineralized porphyry Cu-Au, Mo-Cu and epithermal Au-Ag type mineralizations. On regional scale, the deposition of gold mineralization at the Poboya prospect is likely to have been associated with the early history of the Palu Fault; a sinistral transfer fault.

HISTORY AND CURRENT EXPLORA-TION OVER THE BLOCKS

Prior to the 1990s, exploration of Central and Northern Sulawesi focussed on the po-tential for porphyry copper-gold style min-eralization. The neck of Central Sulawesi around Palu received little exploration attention as previous explorers considered that the active Palu-Koro fault system and

Metamorphic Hosted Low Sulphidation Epithermal Gold Systemat Poboya, Central Sulawesi: A General Descriptive Review (M. F. Wajdi et al.)

133

Contact of Work Map

Ow9 tt< >- R1-11102201

Drawn : EAP

Author : MFW Date : 22'10/2011

Ofice : Palu

Scale :1:1,500,000

Revised : Date :

WGS 84 Enetno

0 20 40 60 80 100

N

Kilometers

o120

Block I

Block II

Block III

Block IV

Block V

Block VI

TOTAL PERMIT AREA

15.390 Ha

28.420 Ha5.009 Ha

36.380 Ha

37.020 Ha

16.670 Ha

138.889 Ha

PT CITRA PALU MINERALS

o-2

o-1

o 0

o121

o120

o0

o-1

o-2

o121

Figure 1. Tenement location map of PT. Citra Palu Minerals CoW areas.


134

Block II

Block III

Block I

Block VI

Block IVBlock V

0 10 20 40 60 80km

N

Contract of Work

Regional Geology

RecentAge

Pliocene - PleistoceneL Miocene - E. Pliocene

? Pliocene

? Pliocene

Upper Miocene - ? Pliocene



U. Oligocene - M. MioceneMiddle Late Miocene

Eocene OligoceneM. Eocene - U. Oligocene

Upper CretaceousCretaceousCretaceous

LEGEND

Rock Unit

Contrack of Work

Thrust Fault

FaultRiverPompangeo MetamorphicsToboli MetamorphicsLamojang Formation

Papayato VolcanicsTalaya - Tineba Rampi Volcanics

Tinombo Formation

Wobodu BrecciaOngka VolcanicsDendo Kamarora IntrusivesLempelero Ukn Potassic Volcanics High - K - Diorite and SyeniteGarnet - Peridote Lariang Bone - Bone SedimentsMolasseAlluvium

o119,5o120 o120,5

o121o121,5 o122

o119,5 o

120 o120,5

o121 o121,5

o122

o1

o0,

5o 0

o0,

5o

-1o

-1,5

o-2

o-2

,5

o 1o

0,5

o0

o0,

5o

-1o

-1,5

o-2

o-2

,5

PT CITRA PALU MINERALS

Figure 2. Regional geological map of northern and central parts of Sulawesi (Sukamto et al. 1973, and Ratman 1976).

apparent absence of any related volcanic activity made this area less favourable.

However in 1992, Rio Tinto undertook re-gional bulk leach extractable gold (BLEG) Au/Ag sampling across accessible areas of Central Sulawesi and identified the Poboya area for follow-up sampling, based on a 27ppb Au, 51ppb Ag BLEG anomaly. The Poboya Prospect was discovered in 1993, when a large clay alteration area was outlined and quartz vein outcrops in the Palu river valley were chip sampled returning highly elevated gold grades including 55 m at 47 ppm Au and 115 m at 15 ppm Au.

Summary of what have already been under-taken are:• Ground magnetic and orientation induced

polarisation (IP) surveying in 1993.• Evaluation of the Palu mineralization

with 11 diamond drill holes completed for 2.861m in 1996. Additional mapping, sampling and ground magnetic surveying were also carried out.

• A 22 diamond drill holes campaign to-talling

• 4494 m, were carried out in 1998, leading to preliminary resource estimations for the Poboya mineralization.


135

• Controlled source audio-magneto tel-luride (CSAMT) surveying was also conducted over the Poboya Prospect, with 18 lines totalling 27 km collected). This survey resulted some highly poten-tial for such mineralization type down dip from the existing Zona.

Since Bumi legally took control PT CPM, the company has conducted several explora-tion activities. These include:• Relogging of the Poboya drilled holes

in Block I; for better understanding of lithology, alteration, and mineralization at Poboya prospect.

• Light Detected and Ranging (LIDAR) surveying in over area of the Block I and IV, to get an accurate elevation and topography contouring.

• Desktop study on the deposit including resource calculation and come up with more conservative numbers than the one claimed by previous company.

• Induced Polarization survey (IP) cover-ing epithermal gold prospect Anggasan in Block IV.

• Follow up ground mapping, grid soil sampling in Block IV and V.

• Regional surface geology mapping and geochemistry sampling over Block I, II, IV and V.

While the systematic resource and reserve delineation drilling campaign at Poboya was started on early September 2011 and is planned to be completed in the mid 2012.

METHODOLOGY

This paper is the result of a review and evaluation of the data that has been available since the prospect of Poboya was discov-ered. The data used comes from a variety of field activities and laboratory analysis; mapping of alteration / mineralization, geo-chemical analysis and geophysical analysis, and drilling program.

POBOYA PROJECT

Location and Property Background

Poboya Prospect is located in Block I of PT CPM CoW Generation VI, 12 km northeast of Palu, Central Sulawesi. In general, Cen-tral Sulawesi forms a thin north-south trend-ing mountain range with rugged topography and elevations ranging from 1470 to 1764 m above sea level. Steep, short rivers directly flow into the ocean.

The prospect was discovered by Rio Tinto in 1993, explored and drill tested in 1994, 1996, and 1998. Rio Tinto decided to divest the project in 1999 and Newcrest Mining put forward a proposal to purchase PT CPM hopeful that it could gain access for both ex-ploration and future mining. However, New-crest also divested the project in late 2004 due to the concentration of the resouces to the new discovery in Halmahera, having completed very limited exploration, none of which was associated with the Poboya Prospect. PT. Bumi Resources Tbk, lately converted to PT Bumi Resources Minerals Tbk (Bumi) acquired the project at this time and is now seeking to advance exploration.

Geology

The Poboya Prospect is located on the east margin of a major pull-apart basin related to the Palu-Koro sinistral strike-slip fault sys-tem that forms part of the Neogene Northern Sulawesi island arc (Kavalieris et al., 1992). This basin and associated infilled with mo-lasse-style conglomerates largely occurs to the southeast of Palu, possibly related to the termination of a releasing bend in the fault system (Marten, 1999). The local geology is complex, represented by the Tinombo For-mation sediments and metavolcanics to the west of vein and gneissic and metamorphic rocks of the Toboli Complex to the east. Structural observations interpreted that the the Poboya vein system formation is along


136

gently SW dipping normal fault that most likely formed in the transtensional stress regime associated with the opening of the Gulf of Palu. The fault is interpreted to be postdated the mineralization event.

Mineralization at Poboya is interpreted as a low sulphidation epithermal system hosted in/by metamorphic rock units. The vein system was formed within a north-northwest trending belt of Toboli meta-morphic rocks to the east of the Palu Fault. The Toboli Complex comprises gneissic and metamorphic rocks, including biotite gneisses intercalated with schists. These have been intruded by granodiorite, feld-spar porphyry, and monzonite to form the basement (Figure 3) which makes up the highlands along the spine of the northern arm of Sulawesi (Muhardjo and Kaschul, 1999). The prospect itself is interpreted to be located close to the base of the uplift essen-tially at the molasse unconformity (Figure 4). Clasts of vein material are noted within the molasse suggesting mineralization is

at least in most part, pre-molasse in timing (Marten, 1999). Interestingly, the Poboya Prospect is notable in its absence of volca-nic or sub-volcanic rocks that are normally closely associated with epithermal systems. Instead the vein Zona, which do show clas-sical low-sulphidation epithermal textures, are generally hosted by biotite gneiss, fore-most in lithology contact Zona with schist as underlie rock (Figure 5). The Poboya vein Zona system comprises a series of gently southwest dipping sheet-like, low sulphida-tion epithermal quartz-carbonate vein Zona. Our current relogging over historic drill holes concluded with general agreement with the geology interpreted of previous workers particularly related to alteration and mineralization. Moreover, beside the better known LS epithermal highly mineralized main quartz vein from the re-logging we identified quite extensive development of low to intermediate grade mineralization Zonas associated with some minor banded chalcedonic quartz-carbonate stockworks Zona with commonly grey sulphide lines at

826000 827000 828000 829000

826000 827000 828000 829000

99

06

00

09

90

50

00

99

04

00

0

Poboya ProspectInterpretative Geology and Drill Hole Location

Legend

N

Gravels & sands

Gravels, sand & muds

Molasse

Hydrothermal Breccia

Reef

Granodiorite

Clay altered rock

Porphyroid Rock

Biotite schist & amphibolite

Fault

Landslide

River

Tahura Boundary

Drill Hole

CSAMT Resistivity

Monzonite

99

06

00

09

90

50

00

99

04

00

0

0 250 500 1,000

M

Figure 3. Poboya geological interpreted map (modified from RTI).


137

Figure 4. Photograph of Palu discovery outcrop, showing multiple phases of quartz veining, silicification, and brecciation at Poboya River.

Legend

Lithology :

Vein

Gneiss

Vein

Gneiss

Schilst

Fault Breccia

Borehole Lithology :

Alluvial

Fault Breccia

Vein

Gneiss

Hydrothermal Breccia

Mollase

Monzonite

Schist

Assays :

< 0.0

0.0 to 1.0

1.0 to 4.0

4.0 to 7.0

7.0 to 10.0

10.0 to 20.0

20.0 to 30.0

30.0 to 40.0

40.0 to 50.0

50.0 to 75.0

>= 100.0

75.0 to 100.0

Figure 5. Typical cross section of mineralization at Poboya prospect.

the edge of the veinlets (Figure 6). The minor veins and veinlets are in the range of 1 cm to 5 cm in thickness and 0.60 g/t to 3.8 g/t gold

in grade. The Zonas are commonly found/mapped adjacent to the main veins. The Zonas could reach up to 20 meters beyond


138

Stockworks

Au mineralization associated withquartz-carbonate stockworks, shownweakly banded quartz-carbonate vein,locally found multiphase veining.Chloritised shist as wallrock.

Banded (Crustiform-colloform-bladed)

Au high grade mineralizationassociated with banded chalcedonicquartz- carbonate vein, dominantlycomposed by quartz (70%), shownstrong grey suphide line at the edgeof vein.

Bladed within weaklybanded

Au mineralization associated withbladed quartz-carbonate vein andweak stockworks, note show weakgrey sulphide at the edge of veinlet.Altered gneiss as wallrock.

Bladed within weaklybanded

Au mineralization associated withbladed-weakly banded quartz-carbonate vein and stockworks set insilisified monzonite.

DescriptionTexture

Banded (crustiform-colloform)-bladed

Au high grade mineralizationassociated with banded chalcedonicquartz - carbonate vein, show stronggrey sulphide line at the edge of vein.Note locally found multiphase veining.

Au mineralization associated withinchalcedonic quartz-carbonatestockworks, locally found greysulphide line at the edge of veinlet,sets in altered gneiss.

bladed-massive

DD96PA02 (117 - 118 cm)GRADE Au 0.63 ppm

DD96PA02 (122-123 ppmGRADE Au 0.56 ppm

DD96PA02 (120-125 cm)GRADE Au 2.5 ppm

DD96PA02 (116 - 117 cm)GRADE Au 0.69 ppm

DD96PA02 (120-121cm)GRADE Au 24-3 ppm

DD96PA02 (119-120 cm)GRADE Au 0.95 ppm

6

5

2

No.

4

3

1

Core Photo

Figure 6. Textures and mineralization showing at Poboya.


139

A

B

Figure 7. Photograph of quartz monzonite with albitisation of plagioclase, development of epidote in wispy fractures chlorite and garnet in vein (A); Showing the quartz monzonite with creamy white albite replacement of plagioclases, garnet, epidote, and chlorite are in crosscutting fractures (B).

the main vein and preliminarily interpreted formed in the same mineralization stage but could probably otherwise. There is no clear crosscutting relationship between those two and no specific dating undertaken to date.

Alteration

Petrology study (Lan Zhang and Ray Mer-chant, 1996) outlined the summary which are:• Four samples from one diamond drill-

hole into the Palu prospect, Central Sulawesi were studied (Figure 7)

• At the top of the hole, the rock is a quartz pyroxene monzonite and the three other samples downhole are mafic poor quartz monzonites

• The rocks have undergone an early al-bitisation which is well developed and probably relates to the deuteric or late

magmatic processes in the intrusive host rocks. In all of the samples, this is postdated by the development of contact metamorphism; the samples show the development of strain fabrics, shear-ing, and mineralogies typical of contact metamorphism. This sees the formation at 87.2 m of epidote, of allanite at 101.8 m, of garnet + allanite at 103.35 m, and of garnet + allanite + sphene at 117.3 m. This variation downhole suggests that the hole is drilled towards the source of the contact metamorphism.

• The prograde mineralogies are in most part replaced by retrogressive epidote and then retrogressive chlorite reflect-ing cooling of the system. Later stages see the development of relatively strong veining consisting of quartz + chlorite + pyrite, and later calcite, chabazite, and chlorite-smectite.

• It is proposed that the area was the site of original potassic intrusion and that there original subsequent reintrusion; this rein-trusion contact metamorphosed the older intrusives creating both prograde and then retrograde assemblages. This gave rise to retrograde observed replacement series of garnet-epidote -chlorite-calcite.

• It is suggested that the best possibility for mineralization in this area rests with the retrogressive chlorite stage which is likely to have generated its own hot wa-ter circulation system as the heat source cooled. The presence of quartz in this assemblage is testimony to the develop-ment of an aqueous system and, at the likely lower temperatures of this phase of the evolution, epithermal/ mesothermal mineralization could well have developed in the fracturing of this generation, clearly evident in these samples.

Mineralization

The main mineralization is hosted within a biotite gneiss. Surface alteration is not


140

well documented due to cover sequence of molasse obscuring much of the surface projection of the prospect. Several vein Zona areas are described termed the Hill Zona and River Zonas, they are:• Hill Vein Zona 1, strike length 2.5 km,

apparent width up to 200 m.• River Vein Zona, located 500 m south of

Hill Vein Zona 1 comprising two quartz vein Zonas.

• Hill Vein Zona 2, located 1.2 km north-east of Hill Vein Zona 1, with strike length of 1.5 km and slightly steeper dip.

Mineralised quartz-carbonate Au-Ag vein Zona shows epithermal textures such as colloform-crustiform banding, bladed cal-cite pseudomorphs, chalcedonic quartz, to cockscomb banded quartz with evidence of multiple fluid phases and brecciation (Figure 7). Gold mineralization is interpreted to be hosted within bladed and banded chalced-ony quartz-carbonate veins with variable thickness ranging from 1cm to >10 m and having a wide range of orientations (Figure 4) and grade. Mineralization textures and mineralogy are typical of low-sulphidation epithermal systems with elevated Ag, Sb (antimony), and As (arsenic) levels and low base metal values.

Gold occurs as anhedral crystals up to 50 microns in size and as inclusions in pyrite. Preliminary metallurgical testwork was un-dertaken by Rio Tinto, 1997 and the results indicated that there was general agreement between metallurgical and geological assays carbon in leach Au recoveries varied from 63 to 94%, with six of the 13 composites achieving Au recoveries >85%.

DISCUSSION AND CONCLUSIONS

The deposit characteristics of Poboya Pros-pect indicate the vein formed at low tem-perature and near netral pH condition, typi-

cally of low sulphidation epithermal deposit. Structurally, Palu-Koro Fault has formed a host structure and fluid conduits (pathways) for the mineralization. Metamorphic rocks of Toboli Formation is the dominant host rock of mineralization. The mineralised Zona is as-sociated with quartz-carbonate vein and vein breccia within dominantly banded, chalche-donic, and bladed textures. The vein contains multiple episode of quartz-carbonate phase.

With no volcanics associated and study on alteration assemblages, it is suggested that the best possibility for mineralization in this area rests with the retrogressive chlorite stage which is likely to have generated its own hot water circulation system as the heat source cooled. The presence of quartz in this as-semblage is evident to the development of an aqueous system at the likely lower tempera-tures of this phase of the evolution which in this environment of epithermal/mesothermal mineralization could well have developed in the fracturing of this generation

Significant additional potential in Poboya could be represented by the extensive devel-opment of low to intermediate grade miner-alization Zonas associated with some minor banded chalcedonic quartz-carbonate stock-works Zona with commonly grey sulphide lines at the edge of the veinlets. The Zonas are commonly found/mapped adjacent to the main veins and preliminarily interpreted formed in the same mineralization stage but could probably otherwise.

Further comprehensive exploration work is required to get better understanding of mineralization regard to structure, validate the ore body model, and reliable resources estimate.

AKNOWLEDGEMENT

May thanks to CPM management for use and publish the internal data, all of personnel at Block I who


141

have contributed and assisted in providing informa-tion and for all of my colleagues for the discussion and support.

REFERENCES

Carlile, J.C., 1983. Geology, Exploration Geochem-istry and Mineralization of the Tombolilato District, Sulawesi, Indonesia.

Kavalieris I, van Leeuwen, TM., and Wilson, M., 1992. Geological setting and styles of mineraliza-tion, north arm of Sulawesi, Indonesia. Journal of Southeast Asian Earth Sciences, 7, p. 113-129.

Marten, B.E., 1999. Report on a visit to the Palu Prospect, Central Sulawesi, Indonesia. In : Rio Tinto, 1999. Central Sulawesi of Contract Work. Report on Geology and Exploration of the Palu Prospect. Rio Tinto Internal Company Report by HP, Muhardjo and N Kaschul, dated September 1999.

Muhardjo and Kaschul, 1999. Central Sulawesi Con-tract of Work. Report on Geology and Exploration of the Palu Prospect. Rio Tinto Internal Company Report by HP, dated September 1999. Volume I and II only. Rio Tinto, unpublished.

Puhle, E., 1997. Palu Carbon in Leach Metallurgical Testwork. Rio Tinto Internal Company Report byRio Tinto, dated August 1997,unpublished.

Sillitoe, R.H., 1997. Characteristics and Controls of the Largest Porphyry Copper-Gold and Epithermal Gold Deposits in the Circum- Pasific Region. Aus-tralian Journal of Earth Sciences, 44, p. 373-388.

SRK Consulting, 2007. Geological Review Explo-ration Project in Sulawesi Indonesia. Confidential report to PT Citra Palu Minerals. Structural study of the Palu Gold Prospect, Central Sulawesi, Indonesia. Confidential report to CRA Exploration Pty Limited.

metamorphic hosted low sulphidation epithermal gold … 20120205.pdfmajalah geologi indonesia, ......

Documents