The Sangkaropi Massive Sulphide Deposit District, South Sulawesi

Majalah Geologi Indonesia, Vol. 27 No. 2 Agustus 2012: 109-119
The Sangkaropi Massive Sulphide Deposit District, South Sulawesi:
Its Implications for Genesis and Exploration
for Kuroko-type Deposits
Kawasan Cebakan Sulfida Masif Sangkaropi, Sulawesi Selatan:
Implikasinya terhadap Genesis dan Eksplorasi
untuk Cebakan tipe-Kuroko
Yaya Sunarya1), Tetsuo Yoshida2), Koswara Yudawinata1),
Rusman Rinawan1), Hartono1), and Bronto Sutopo1)
2)
1)
PT Antam (Persero) Tbk
Department of Mining, Kyushu University, Fukuoka 812, Japan
ABSTRACT
The Sangkaropi massive sulphide deposit district, including the Sangkaropi (Batu Marupa), Rumanga,
and Bilolo deposits occur in the central part of western Sulawesi, Indonesia. The area is located in the
western Sulawesi arc which at that time acted as a volcanic arc. The volcanic activity seems to have
been almost contemporaneous with that in the Japanese “Green Tuff” region in Miocene, where all
Kuroko-type deposits in Japan are distributed in a relatively narrow zone. The formation deposits are
closely associated with the extensive submarine volcanism. The deposits are composed of stratiform
or broken stratiform and stockwork ore bodies with no gypsum ore. In the Sangkaropi district, the
stratiform ore bodies are mostly covered with a thin layer of barite at the top. Sulfide minerals of the
ore deposits are sphalerite, galena, chalcopyrite, pyrite, tetrahedrite, bornite, chalcocite and covellite
with quartz, barite, and clay minerals. A colloform texture is frequently observed in the fine-grained
stratiform ore of the Sangkaropi deposits. The filling temperatures of fluid inclusions in sphalerite
and quartz from druse and vein range from 160o to 346oC.
Keywords: massive sulphide deposit, submarine volcanism, Kuroko-type, Sangkaropi, South
Sulawesi
SARI
Kawasan cebakan sulfida masif Sangkaropi, yang meliputi Cebakan Sangkaropi (Batu Marupa),
Rumanga, dan Biloko terletak di bagian tengah Sulawesi bagian barat barat, Indonesia. Daerah ini
berada di busur Sulawesi bagian barat, yang pada saat itu merupakan suatu busur vulkanis. Kegiatan
vulkanik ini rupanya hampir bersamaan dengan yang terjadi di Jepang kala Miosen yaitu kawasan
“Green Tuff”, tempat cebakan tipe-Kuroko di Jepang yang tersebar dalam suatu zona sempit. Pembentukan cebakan tersebut berasosiasi dengan vulkanisme bawah-laut yang ekstensif. Cebakan ini
berupa stratiform atau broken stratiform dan tubuh bijih stockwork tanpa bijih gipsum. Di kawasan
Sangkaropi, tubuh bijih stratiform umumnya ditutupi oleh suatu lapisan tipis barit. Mineral sulfida
cebakan bijih terdiri atas sfalerit, galena, kalkopirit, tetrahedrit, bornit, kalkosit, dan kovelit dengan
kuarsa, barit, dan mineral lempung. Tekstur colloform sering ditemukan di dalam bijih stratiform
berbutir halus, cebakan Sangkaropi. Temperatur pengisian oleh inklusi fluida dalam sfalerit dan
kuarsa dari druse dan urat berkisar antara 160o - 346oC.
Kata kunci: cebakan sulfida masif, vulkanisme submarin, tipe Kuroko, Sangkaropi, Sulawesi
Selatan
Naskah diterima: 01 Oktober, revisi terakhir: 30 Juli 2012, disetujui: 06 Agustus 2012
109
Majalah Geologi Indonesia, Vol. 27 No. 2 Agustus 2012: 109 -119
INTRODUCTION
GEOLOGIC SETTINGS
The Sangkaropi district is situated in the
southwest Sulawesi, near the Rantepao town
in Tana Toraja (Figure 1). It is about 330 km
from Ujung Pandang to Rantepao through
Makale, the capital of Tana Toraja region.
From Rantepao to Sangkaropi district is
about 17 km long and is only accessible by a
four-wheel-drive car through the rough road.
General Geology of Sulawesi
125o E
124o E
122o E
121o E
o
120 E
119o E
This paper describes the result of studies on
the geology, mineral assemblages, and fluid
inclusions of ores in these Kuroko-type ore
deposits of the Sangkaropi district.
i) The oldest rocks in the West Sulawesi
Province are basement complexes of preTertiary polymetamorphic consisting of
gneiss, schist, and ultrabasic rocks. Sediments unconformably overlying the basement were deposited in the deep trough
which was caused by Tertiary subduction.
Intensive volcanism and plutonism were
accompanied with the subduction process.
The submarine volcanism was widespread
during the Miocene. The Quartenary volcanics were deposited subaerially on hills
123o E
Historically, copper ore was mined on a
small scale at the Sangkaropi deposits during the World War II. Subsequently, a further
exploration work was started in 1974 and
since 1979 the work has been carried out
by PT Antam (Persero) Tbk. intensively in
the district, including the Sangkaropi, Rumanga, and Bilolo pros\pects.
The general geology of Sulawesi summarized as shown in Figure 1, is chronologically divided into the following three geological Provinces in roughly aging order:
i) West Sulawesi Province, ii) East Sulawesi
Province, and iii) Bangai-Sula Province
(Sukamto, 1975).
-1o S
-2 S
o
Banggai
Island
Sula
Island
Sangkaropi
-3o S
Gulf
of
Bone
Legend
Q
Qv
Ts
Tv
Ti
Mi
Ms
Pm
U
Gs-S
-4o S??
N
Makassar
0
50
100 Km
Figure 1. Geologic map of Sulawesi (modified from Sukamto, 1975). Note: Q-Quaternary sedimentary rocks
including lake deposits and coral limestone; Qv-Quaternary volcanic rocks; Ts-Tertiary sedime tary rocks; TvTertiary volcanic rocks; Ti-Tertiary intrusive rocks; Ms-Mesozoic sedimentary rocks; Mi-Mesozoic volcanic
and intrusive rocks; Pm-Paleozoic metamorphic rocks, Gs-S - Gneiss and Schist unknown in age; U-Ultrabasic
rocks unknown in age. Tertiary volcanic and intrusive rock is highlighted in red and green color for the Kurokohosted unit.
110
The Sangkaropi Massive Sulphide Deposit District, South Sulawesi: Its Implications for Genesis and
Exploration for Kuroko-type Deposits (Y. Sunarya et al.)
and valleys. Intrusive rocks from granite to
diorite (1.62 to 31.0 ma) (Sukamto, 1975)
intrude the Miocene and older rocks of the
province.
An important system of faults and associated
fold trends NNW parallel to the inferred
trend of the Tertiary through.
ii) The East Sulawesi Province and the west
Sulawesi one is bordered with a fault zone
(the Browe Median Line, after Radja, 1970)
running from north to south in the central
part of Sulawesi. The province is underlined
mainly by basic to ultrabasic igneous rocks
and schistose metamorphic rocks although
Mesozoic carbonates and clastics associated with radiolarian cherts and Neogene
sedimentary rocks are also distributed in
the province. Paleogene sedimentary rocks
are distributed at a restricted area in the
northern part.
iii) The Banggai-Sula Province is characterized by a continental basement consisting of
Paleozoic metamorphic rocks intruded by
granites of Triassic and Permian age. Triassic and Permian effusive rocks are locally
distributed on basement complexes and are
overlain by Mesozoic sedimentary rocks.
The geological structure and history of
Sulawesi have been interpreted in terms of
plate tectonics (Sukamto, 1978; Katili, 1975,
1978). It is divided into two major tectonic
units namely the Sulawesi Arc, corresponding to the non-volcanic outer are which
comprises eastern Sulawesi, the submarine
Mayu Ridge and the Talaud Island, and
the western Sulawesi Arc, corresponding
to the volcanoplutonic which continues to
the Sangihe Islands and further north to the
Philippines.
Several Kuroko-type and porphyry copper deposits are situated in the western Sulawesi Arc. A major orogenic event in the
western arc took place towards the end of
the Cretaceous and was followed by calc-
alkaline volcanism. At the beginning of the
Middle Miocene, a second major orogenic
event occurred and was accompanied by
andesitic volcanism and granite intrusion
(Taylor and Van Leeuwen, 1980). Kurokotype mineralization in the western Sulawesi
is seem to have been closely related to the
latter volcanic activity.
Geologic Setting of Sangkaropi District
The Tertiary rocks in the Sangkaropi district
are divided into eight members as follows:
(1) Granitic rock, (2) Andesitic tuff breccia,
(3) Dacite, (4) Acidic tuff, (5) Rhyolitic
pyroclastic and lava, (6) Basalt and clay,
(7) Calcareous shale, and (8) Andesitic lava
and pyroclastics. Geologic map of the Sangkaropi area is shown in Figure 2.
1. The Granitic rock member crops out
only in the northern part of Sangkaropi
deposits. It is light to dark grey in color,
massive and phaneritic in appearance.
It consists of quartz, alkali feldspar,
plagioclase, and some mafic minerals.
It is cut by some quartz veinlets altered
by argillitization, sericitization, and
chloritization. Importantly, there is no
contact metamorphism was observed in
rocks adjacent to the granite.
2. The andesitic Tuff Breccia Member consists mainly of andesitic tuff breccia and
lapili tuff with intercalations of sandy
tuff, fine tuff, claystone or mudstone and
silicified rocks. The unit member is light
to dark green in color. It usually shows
poor sorting, but the core samples from
drilling in the area near the Rumanga
ore deposits show a graded bedding
structure.
3. Dacite Member is commonly green and
altered. The unit is distributed on the
top of the Acidic Tuff Breccia Member
as flow layers.
4. The Acidic Tuff Member is composed
of acidic tuff, tuff breccia, breccia, and
clay which is grey to light green in co111
Majalah Geologi Indonesia, Vol. 27 No. 2 Agustus 2012: 109 -119
N
Legend:
Sangkaropi
Figure 2. Geological map of the Sangkaropi district. Note: 1 - Granitic rock; 2 and 3 - Andesitic tuff breccia
and Dacite lava; 4 - Acidic tuff; 5 - Rhyolitic pyroclastics and lava; 6 - Basalt and Clay; 7 - Calcareous shale;
8 - Andesitic lava and pyroclastics; 9 - Kuroko-type ore body.
lour. The acidic tuff breccia and breccia
consist of fragments of dacite, granite,
andesite, and pumice.
5. The Rhyolitic Pyroclastics and lava
Member is light grey to dark grey in color. It is massive and mainly composed
of rhyolitic to dacitic tuff, breccia, and
lava. It is difficult to distinguish rhyolitic
lava from rhyolitic pyroclastics in the
field, because of their alteration to silicified rocks. It is about 80 m in maximum
thickness.
6. The Basalt and Clay Member crops out
only around the Sangkaropi deposits.
The fresh basalt is dark green to black
in colour, while altered basalt is dark
brown. Claystone is grey to dark grey
in colour. Silicification and brecciation
are observed in claystone in contact with
ore deposits like in the Sangkaropi
deposits.
7. The Calcareous Shale Member comprising shale and clay is grey in color and
112
contains a small quantity of calcareous
material. Foraminifera fossils are found
in brownish clay intercalated with shale.
8. The Andesitic Pyroclastics and Lava
Member is composed of andesitic lava
and pyroclastics. Andesite lava is green
in colour and massive. Andesitic pyroclastic rocks consist of volcanic breccia
and tuff breccia with small amounts of
clay and silicified rocks.
RESULT OF INVESTIGATION AND
DISCUSSION
Ore Deposits
In the Sangkaropi district, the ore deposits
of Kuroko-type are found mainly at the base
of Ryholitic Pyroclastics and Lava Member and in the upper part of Andesitic Tuff
Breccia Member. Study of the Sangkaropi,
Rumanga, and Bilolo deposits shows a linear
The Sangkaropi Massive Sulphide Deposit District, South Sulawesi: Its Implications for Genesis and
Exploration for Kuroko-type Deposits (Y. Sunarya et al.)
stratigraphical correlation from southwest to
northeast. The ore deposits are divided into
two types: (i) syngenetic stratiform massive
type and (ii) epigenetic vein and stockwork
type. Stratigraphical column is shown in
Figure 3.
(i) The stratiform massive and fragmental
ore bodies are concordantly distributed
within the silicified claystone overlying
stratiform silicified ores at the Sangkaropi
deposits (Figure 4). The diameter of fragmental ores sometimes measures up to
several meters in maximum. They are
composed mainly of sphalerite, galena,
and barite accompanied with chalcopyrite
and pyrite. Small amounts of gold and
silver detected (Nishiyama et al., 1981). In
general, the top of ores is covered by a thin
layer of barite which can be seen in outcrop
of the Sangkaropi, Rumanga, and Bilolo deposits. Yellow ore consists mainly of pyrite
and chalcopyrite, which gypsum which is
typical in Japan is not found in th deposits.
(ii) The stockwork ore bodies occur below the horizon of stratiform ores. They
consist of veins of pyrite, quartz vein with
pyrite, chalcopyrite, sphalerite and galena
and stockworks of sulfide minerals. They
crop out in the Sangkaropi and Rumanga
deposits.
Paragenesis of Ore and Gangue Mineral
Minerals in ores collected from the Sangkaropi (Sangkaropi, Rumanga, and Bilolo
prospects) district are as follows: sphalerite, galena, pyrite, chalcopyrite, bornite,
tetrahedrite, chalcocite, covelline, quartz,
barite, sericite, interstratified sericitemontmorillonite, chlorite, and intersatisfied
chlorite-saponite.
Ores of the Sangkaropi deposits show black
colour and sometimes porous. They consist
mainly of sphalerite, galena, and chalcopyrite with barite, pyrite, tetrahedrite, quartz,
sericite, and chlorite. Sphalerite is the main
constituent of the ores. Sphalerite contains
fine-grained pyrite and chalcopyrite showing framboidal texture which is 10 to 50 µm
in diameter (Figure 5a). The central part or
a part of the framboidal pyrite-chalcopyrite
is replaced by sphalerite or left vacant
(Figure 5b). Sphalerite also contains many
inclusions of chalcopyrite dots and small
tetrahedrite grains. Tetrahedrite is not so
abundant but commonly found.
Ores from Rumanga deposits are of stockwork consisting mainly of sphalerite, pyrite, chalcopyrite, bornite, tetrahedrite, and
chalcocite with small amounts of galena,
covelline, quartz, sericite, interstratified
sericite-montmorillonite, chlorite and interstratified chlorite-saponite. Figure 5c
shows stratiform galena ore association
with fine-grained chalcopyrite.
Ores collected from a prospecting tunnel
shows characteristically chalcocite-tetrahedrite veins with bornite or their fine-grained
aggregates in sphalerite. Chalcocite also
occurs in the form of veinlets in bornite and
chalcopyrite sometimes with tetrahedrite.
Pyrite crystals are large (0,8) and subhedral. Many chalcopyrite dots are observed
in sphalerite. A large sphalerite (5 to 6 mm)
cut by chalcopyrite are observed around
them in sphalerite. Chalcocite veinlets with
euhedral or subhedral pyrite crystals are
observed in chalcopyrite. Small amounts
of covellite and tetrahedrite are found in
and around chalcopyrite. Figure 5d shows
simple locking intergrowth pyrite, bornite,
sphalerite, and chalcopyrite, while Figure
5e shows pyrite fracturing filled by bornite,
galena, and covelite.
Ores from the Bilolo deposits are compact
and black and in part yellow in color. They
are composed of galena, sphalerite, pyrite,
chalcopyrite, bornite, tetrahedrite, and coveline with barite. Barite is also associated
with microgranular silica (Figure 5f). The
113
Majalah Geologi Indonesia, Vol. 27 No. 2 Agustus 2012: 109 -119
1
2
Bilolo
Rumanga
Sangkaropi
4
3
5
6
7
8
9
10
11
Figure 3. Stratigraphical corelation of the Sangkaropi, Rumanga , and Bilolo deposits. Note: 1 - Foraminifera
limestone; 2 - Foraminifera marl; 3 - Dacitic tuff; 4 - Basalt showing pillow structure; 5 - Barite and pumice
tuff; 6 - Mudstone and massive sulfide ore; 7 - Silicified zone with stockwork ore; 8 - Silicified dacitic tuff
breccia with veins; 9 - Black shale; 10 - Dacitic tuff breccias and 11 - Granitic rock.
N
1200 m
1150 m
S
1100 m
0
1
2
3
4
5
6
7
8
9
20 m
10
Figure 4. Cross section of one of the ore bodies in the Sangkaropi deposits. Note: 1 - Basalt; 2 - Claystone; 3
- Dacitic tuff breccia; 4 - Fragmental ore and silicified claystone; 5 - Silicified ore; 6 - Rhyolitic tuff breccias;
7 - Granitic rock, intruded into rhyolitic tuff breccias; 8 - Stockwork ore, 9 - Fault, 10 - Drill hole.
banded structure consisting of fine- and
coarse-grained minerals is observed in stratiform ores. The fine-grained part is mainly
composed of galena and sphalerite, while the
coarse-grained is of pyrite and chalcopyrite.
Chalcopyrite fills the spaces between broken
pyrite grains. The fine-grained galena shows
a flow-like structure. Covellite, sphalerite,
and tetrahedrite occur in the band of the fine114
grained galena. Covellite, chalcocite, and
bornite are frequently observed in gangue
of barite with small amounts of chalcopyrite
and tetrahedrite. Sphalerite is also associated
with framboidal chalcopyrite in gangue
mineral (Figure 5g). Bornite is frequently
observed with chalcopyrite, covelite, and
sphalerite (Figure 5h).
The Sangkaropi Massive Sulphide Deposit District, South Sulawesi: Its Implications for Genesis and
Exploration for Kuroko-type Deposits (Y. Sunarya et al.)
A
B
cpy
Py-f
py
Py-an
gn
0,05 mm
C
0,2 mm
D
cpy
bn
py
gn
gn
sph
cpy
0,05 mm
0,5 mm
F
E
msi
cv
bn
ba
gn
py
0,1 mm
op
0,5 mm
H
G
sph
cv
sph
cpy
cpy
0,05 mm
bn
0,1 mm
Figure 5. Microphotographs of the ores from the Kuroko-type deposits in the Sangkaropi district. A) Framboidal pyrite (py-f) associated with anhedral pyrite (py-an) in gangue mineral (Sangkaropi deposits);
B) Chalcopyrite (cpy) associated with frambiodal pyrite (py) and deformed galena (gn) (Rumanga deposits);
C) Stratiform galena (gn) ore associated with fine grained chalcopyrite (cpy) (Rumanga deposits); D) Simple
locking intergrowth pyrite (py)-bornite (bn)-sphalerite(sph)-chalcopyrite (cpy) (Rumanga deposits); E) Pyrite
(py) fracturing filled by bornite (bn)-galena (gn)-covelite (cv) (Rumanga deposits); F) Barite (ba) associated
with microgranular silica (msi) and opaque (op) mineral (Bilolo deposits); G) Sphalerite (sph) associated with
framboidal chalcopyrite (cpy) in gangue mineral (Bilolo deposits); H) Bornite (bn) associated with chalcopyrite (cpy), covelite (cv), and sphalerite (sph) (Bilolo deposits)
115
Majalah Geologi Indonesia, Vol. 27 No. 2 Agustus 2012: 109 -119
Fluid Inclusion
Small fluid inclusions were observed from
minerals of sphalerite, quartz, and barite.
Transparent samples were collected for fluid
inclusion study from tiny fragments (less
than 0,3 mm thick) of ores consisting of
sulfide minerals, barite, and quartz.
Most fluid inclusions, except these of barite,
have two phases of vapor and liquid at room
temperature. Barite contains mono-phases
inclusions together with two-phase ones in
the same samples. Mono-phase inclusions
are more frequently observed than twophases ones.
Most fluid inclusions observed were too
small in size to measure the filling temperature as well as freezing temperature. Filling
temperature data for 18 fluid inclusions were
obtained from the Sangkaropi and Rumanga
deposits study. They range from 160o to 340o
C (Figure 6). Inclusions in barite from ores
of the Bilolo deposits were not measured
because of their small size.
Quartz containing fluid inclusions grows
in druse with the fringe of barite in the
stratiform ore of the Sangkaropi deposits.
Four filling temperatures for quartz in druse
show a range between 207 o and 276oC.
Both mono- and two-phase inclusions are
observed in barite collected from the same
specimen. Filling temperatures of these inclusions seem to be variable judging from
the observation.
Quartz and sphalerite in the stockwork ore of
Rumanga deposits have two different temperature range depending on the occurence.
Amethyst quartz in vein shows the higher
temperature range from 236 o to 346oC for
five inclusions. The other quartz as constituent of stockwork ore shows the lower
filling temperature range from 187o to 251oC
for five inclusions. Sphalerite measured is
brown in hand specimen and transparent
in thin section. Four filling temperatures
116
obtained from these sphalerites range between 160 oC and 184 oC. This temperature
range is very low as compared with that of
the Kuroko-type stockwork ores in Japan;
for instance the values obtained from the
Fukazawa deposits in the Hokuroku and
Iwami deposits in the Sanin districts range
from 246 o to 370oC (Yoshida and Mukaiyama,1982) and from 202o to 334oC (Yoshida,
1979) respectively.
The fluid inclusion data provided the maximum temperature of hydrothermal activity
in the area might have gone up to 350oC in
amethyst veins. However, the relationship
between amethyst veins and the main kuroko mineralization is not clear.
It was estimated on the stockwork ore
that these data of filling temperatures for
sphalerite (184o - 160oC) represent the main
stage of mineralization, the ore forming
temperature may be lower than that in the
Japanese kuroko-type deposits. However,
data from druse quartz in the stratiform ore
of the Sangkaropi deposits, located only
about two kilometers southwest of the Rumanga deposits, indicate the ore forming
temperatures from 280o to 200oC on the
seafloor. This temperature range is almost
the same as that of the stratiform kuroko
mineralization in Japan. Barite in druses
exhibits variable ratios of gas to liquid, from
two-phase (the high temperature state) to
mono-phase (the low temperature state).
Barite probably continued to precipitate in
temperature below 100oC.
Assuming that the maximum temperature of
mineralization was about 280oC, the seawater will be boiled at the depth of sea shallower than about 640 m. Consequently the
depth of sea at that time was not shallower
than 640 m because boiling phenomenon
of ore solution was not observed in fluid
inclusions.
The Sangkaropi Massive Sulphide Deposit District, South Sulawesi: Its Implications for Genesis and
Exploration for Kuroko-type Deposits (Y. Sunarya et al.)
Kuroko-type Deposits in Sangkaropi Area, Sulawesi, Indonesia
Druse quartz (Sangkaropi)
Vein quartz
Quartz
(Rumanga)
Sphalerite
150
200
250
300
350
Filling
Figure 6. Data of filling temperatures from the Sangkaropi and Rumanga deposits, excluding data from barite.
Implication of the Sangkaropi Kuroko
Discovery
The Sangkaropi Kuroko deposits are
hosted by the “Green Tuff Formation” of
the Tertiary submarine volcanic rocks (Tv)
and completely showing by the extracted
geological environment control in Figure
1. The Tertiary volcanic rocks unit occupied
large areas of the western area of the WestSouthern Sulawesi. The Green Tuff Formation developed in the Neogen Old Andesite
Formation. The title of Old Andesite Formation was given by Van Bemmelen (1949)
which is developed running and following
the belt of the Indonesia Island Arc.
The volcano stratigraphy of the old Andesite
Formation should be investigated and studied for knowing the zonation of the subareal
and submarine volcanics which important
for delineating the submarine volcanic areas.
The distribution of the submarine volcanic
is the key for discovering the Kuroko type
deposits (Table 1). Those model type of the
deposits mention could be used as the assesment approach models for discovering the
more better and larger ore deposits in the
submarine volcanics hosted of the Indonesian Island Arc (Table 1). The discovery of
the Sangkaropi Kuroko ore type deposits
of PT Aneka Tambang in 1980 has given the
ideas for studying the volcano stratigraphy
and explore the Old Andesite Formation of
the whole belt of the Indonesia Island Arc.
This idea was strengthening by the following two areas discoveries of the Wetar and
Sangihe Island in 1994. DMR also organised
the join cooperation work with JICA/MMAJ
in West Java.
In 1987, PT. Prima Lirang Mining discovered the barite gold deposit in the Kuning
river, east of Lerokis, Wetar Island. In 1989,
PT. Meares Soputan Mining also discovered
the stratabound gold silver deposit in Binebase area of north Sangihe Island. This type
of deposit is similar to the Lerokis-Kali Kuning deposit in Wetar, both containing barite.
Starting from 1992, DMR continued investigation and explored the Java and Lesser
Sunda Islands by the very preliminary exploration method, many green tuff evidences
and mineralization were found at many
places of the island arc.
In 1995, DMR and JICA/MMAJ studied that
gypsum deposits of Cisasah and Cidadap
areas which being mined by the domestic
company has been improved as a the leading guides for finding the massive sulphite
Kuroko-type deposits in the projected area.
It is believable and should be organized that
the Old Andesite Formation is in promising
and potential for discovering such Kurokotype deposits.
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Majalah Geologi Indonesia, Vol. 27 No. 2 Agustus 2012: 109 -119
Table 1. Green Tuff Formation and the Kuroko-ore Type Occurrences developed in Indonesia.
NO
1
LOCATION
Ende
(Tanjung Ngalebu)
ROCK TYPE/FORMATION
• Dacite tuff breccia, lava and tuff
• Greyish to greenish grey, pillow
MINERALS ASSOCIATION
• Malachite, chalcopyrite, pyrite, barite layer and chert
• Fragmental ore
structure
Rock Formation: Upper Kiro, Tanahau
2
Riung
• Dacite tuff, greenish
(Torongpadang)
Rock Formation: Upper Kiro
• Barite layer, manganese, chert
3
Bima
• Tuff, lava and tuff breccia
• Greenish
4
Malang
(Southern part of Malang)
• Tuff, greenish Rock Formation: Mandalika
• Zeolite, manganese, chert
5
Tasikmalaya
• Dacite tuff, lava and tuff breccia
• Greenish
• Zeolite, manganese, barite bed, chert, gypsum, galena,
sphalerite, gold
(JICA-NMAJ and DMR, 1995
- 1996)
Rock Formation:
Bayah
• Tuff, greenish Rock Formation: Cimapag
• Zeolite
• Dacite and andesite breccia
• Gold, silver, pyrite, marcasite, chalcosite, bornite, chalcopyrite, enargite
• Barite vein (?), manganise, chert
Rock Formation: Dacite, tuff rock urut (Tmdt)
6
Upper Jampang (Genteng Member)
(West Java)
7
Wetar
(Lerokis,
Kalikuning, Meron)
• Barite sand and chert
Resources:
• Lerokis: 2.9 MT Au: 19 Ton Au Ag: 106 g/t
• Kalikuning : 2.2 MT
Au: 5.5 g/t; Ag: 146 g/t
• Meron: 0.3 MT Au: 3.5 g/t; Ag: 110 g/t
8
Sangkaropi
• Dacite tuff, lava, tuff breccia
Rock Formation:
• Galena, sphalerite, pyrite, chalcopyrite, covvelite, bornite
• Barite layer and chert
Dacitic
Resources:
• 2,500,000 T
pyroclastic formation (Makale?)
Cu: 0.6 %
(JICA NMAJ and DMR-ANTAM, 1982)
9
Sangihe
• Andesite-dacitic volcanoclastic
Binabase
Rock Formation:
• Stratiform silica-pyrite minor Au
Miocene Taware volcanic
• Barite vein
• Gypsum with minor galena, sphalerite veining
Bawone
• Chalcosite vein
• Barite with gold
Resources:
• Bawone: 4.5 MT Au: 1.37 g/t
Ag: 8 g/t
Cu: 0.29%
10
Kajong (Flores)
• Kiro Formation of dacitic submarine volcanic
of Miocene age
JOGMEC test drilling result
a) 12.5 m massive ore containing: Zn 12%, Cu 2.2 %, Pb
0.03 %, Au
0.9 g/t, Ag 51 g/t
b) 2,05 m massive sulfide ore containing: Zn 56.5%, Cu 1.6
%, Pb 0.05%, Au 0.4 g/t, Ag 30 g/t
1.2 Mt ore reserved
(JOGMEC, 2008)
PT Antam (Persero) Tbk also took joint
venture with JOGMEC in the Flores Island,
started May 2004, resulting the Kuroko
deposits discoveries at Tehong and Kajong
areas.
118
CONCLUSION
Kuroko-type deposits of the Sangkaropi
district (Sangkaropi, Rumanga, and Bilolo
deposits) occur in the rhyolitic pyroclastic
The Sangkaropi Massive Sulphide Deposit District, South Sulawesi: Its Implications for Genesis and
Exploration for Kuroko-type Deposits (Y. Sunarya et al.)
rocks in the Green Tuff Formation of Miocene age. Stockwork ore bodies are typically
overlain by stratiform massive Kurokotype ore deposits and a barite layer. The
stratiform Kuroko-type ore body is often
brecciated in the outcrops. The typical Oko
(yellow ore) and gypsum ore have not been
not found in these deposits. The ores from
deposits consist of sphalerite, galena, chalcopyrite, pyrite, bornite, tetrahedrite, chalcocite and covelline with barite, quartz, sericite, interstratified sericite-montmorillonite,
chlorite, and interstratified chlorite-saponite.
A colloform texture is sometimes observed.
The filling temperatures of fluid inclusions
in sphalerite and quartz from druse and vein
range from 160o to 346oC. Thus, the feature
of ores mineral assemblages and filling temperatures of ore deposits in the Sangkaropi
area resemble to those of the Kuroko-type
ore deposits in Japan, excluding a marked
distinction of the absence of gypsum ore.
Those model type of the deposits and the
Green Tuff Formation could be used as the
assesment approach models for discovering
the more better and larger ore deposits in
submarine volcanics hosted of the Indonesian Island Arc.
ACKNOWLEDGMENTS
The authors wish to express their gratitude to the
committee of the Seminar of the Sulawesi Mineral
Resources, Manado 2011 for permission to present
the paper in the seminar. Moreover, to improve the
paper for the MGI-IAGI, some additional data and
correction have been done.
Katili, J. A. 1975. Volcanism and plate tectonics
in the Indonesian Island arcs. Tectonophysics, 26,
p.165 - 188.
Katili, J. A., (1978): Post and present geotectonic
position of Sulawesi, Indonesia. Tectonophysics,
45, p.289 - 322.
Nishiyama, T., Hikabe, Y., Minato, T., Rustiadi, and
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area, South Sulawesi, Indonesia. Abstract of the
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Japanese).
Sewell, D. M., et al., 1994. The Lerokis and Kali
Kuning submarine exhalative gold-silver- barite
deposits, Wetar Island, maluku, Indonesia. Journal
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forming process of the Iwami deposits, Shimane
perfecture, Japan. Mining Geology., 29, 21 - 31 (in
Japanese with English abstract).
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Hokuroku basin, Akita, Japan. Journal of Mining
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