TY - JOUR
T1 - Geological and Geochemical Characteristics of Gold Mineralization in the Salu Bulo Prospect, Sulawesi, Indonesia
AU - Tuakia, Muhammad Zain
AU - Takahashi, Ryohei
AU - Imai, Akira
N1 - Funding Information:
We thank PT Masmindo Dwi Area (One Asia Resources Ltd.) for providing data and accommodation during the field work. Financial support was provided by a MEXT scholarship and the Leading Program of Akita University. We extend our thanks to Dr. Hinako Sato and Dr. Takuya Echigo for their support in the analyses. We are grateful to the Department of Geological Engineering, Hasanuddin University, for the logistic support. We also thank Editor-in-chief Prof. Ken-ichiro Hayashi and an anonymous reviewer for their review and comments that greatly improved this manuscript.
Publisher Copyright:
© 2018 The Society of Resource Geology
PY - 2019/4
Y1 - 2019/4
N2 - The Salu Bulo prospect is one of the gold prospects in the Awak Mas project in the central part of the western province, Sulawesi, Indonesia. The gold mineralization is hosted by the meta-sedimentary rocks intercalated with the meta-volcanic and volcaniclastic rocks of the Latimojong Metamorphic Complex. The ores are approximately three meters thick, consisting of veins, stockwork, and breccias. The veins can be classified into three stages, namely, early, main, and late stages, and gold mineralization is related to the main stage. The mineral assemblage of the matrix of breccia and the veins are both composed of quartz, carbonate (mainly ankerite), and albite. High-grade gold ores in the Salu Bulo prospect are accompanied by intense alteration, such as carbonatization, albitization, silicification, and sulfidation along the main stage veins and breccia. Alteration mineral assemblage includes ankerite ± calcite, quartz, albite, and pyrite along with minor sericite. Pyrite is the most abundant sulfide mineral that is spatially related to native gold and electrum (<2–42 μm in size). It is more abundant as dissemination in the altered host rocks than those in veins. This suggests that water–rock interaction played a role to precipitate pyrite and Au in the Salu Bulo prospect. The Au contents of intensely altered host rocks and ores have positive correlations with Ag, Ni, Mo, and Na. Fluid inclusions in the veins of the main stage and the matrix of breccia are mainly two-phase liquid-rich inclusions with minor two-phase, vapor-rich, and single-phase liquid or vapor inclusions. CO2 and N2 gases are detected in the fluid inclusions by Laser Raman microspectrometry. Fluid boiling probably occurred when the fluid was trapped at approximately 120–190 m below the paleo water table. δ18OSMOW values of fluid, +5.8 and +7.6‰, calculated from δ18OSMOW of quartz from the main stage vein indicate oxygen isotopic exchange with wall rocks during deep circulation. δ34SCDT of pyrite narrowly ranges from −2.0 to +3.4‰, suggesting a single source of sulfur. Gold mineralization in the Salu Bulo prospect occurred in an epithermal condition, after the metamorphism of the host rocks. It formed at a relatively shallow depth from fluids with low to moderate salinity (3.0–8.5 wt% NaCl equiv.). The temperature and pressure of ore formation range from 190 to 210°C and 1.2 to 1.9 MPa, respectively.
AB - The Salu Bulo prospect is one of the gold prospects in the Awak Mas project in the central part of the western province, Sulawesi, Indonesia. The gold mineralization is hosted by the meta-sedimentary rocks intercalated with the meta-volcanic and volcaniclastic rocks of the Latimojong Metamorphic Complex. The ores are approximately three meters thick, consisting of veins, stockwork, and breccias. The veins can be classified into three stages, namely, early, main, and late stages, and gold mineralization is related to the main stage. The mineral assemblage of the matrix of breccia and the veins are both composed of quartz, carbonate (mainly ankerite), and albite. High-grade gold ores in the Salu Bulo prospect are accompanied by intense alteration, such as carbonatization, albitization, silicification, and sulfidation along the main stage veins and breccia. Alteration mineral assemblage includes ankerite ± calcite, quartz, albite, and pyrite along with minor sericite. Pyrite is the most abundant sulfide mineral that is spatially related to native gold and electrum (<2–42 μm in size). It is more abundant as dissemination in the altered host rocks than those in veins. This suggests that water–rock interaction played a role to precipitate pyrite and Au in the Salu Bulo prospect. The Au contents of intensely altered host rocks and ores have positive correlations with Ag, Ni, Mo, and Na. Fluid inclusions in the veins of the main stage and the matrix of breccia are mainly two-phase liquid-rich inclusions with minor two-phase, vapor-rich, and single-phase liquid or vapor inclusions. CO2 and N2 gases are detected in the fluid inclusions by Laser Raman microspectrometry. Fluid boiling probably occurred when the fluid was trapped at approximately 120–190 m below the paleo water table. δ18OSMOW values of fluid, +5.8 and +7.6‰, calculated from δ18OSMOW of quartz from the main stage vein indicate oxygen isotopic exchange with wall rocks during deep circulation. δ34SCDT of pyrite narrowly ranges from −2.0 to +3.4‰, suggesting a single source of sulfur. Gold mineralization in the Salu Bulo prospect occurred in an epithermal condition, after the metamorphism of the host rocks. It formed at a relatively shallow depth from fluids with low to moderate salinity (3.0–8.5 wt% NaCl equiv.). The temperature and pressure of ore formation range from 190 to 210°C and 1.2 to 1.9 MPa, respectively.
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U2 - 10.1111/rge.12193
DO - 10.1111/rge.12193
M3 - Article
AN - SCOPUS:85057990246
VL - 69
SP - 176
EP - 192
JO - Resource Geology
JF - Resource Geology
SN - 1344-1698
IS - 2
ER -