Kant, Win
Geological Engineering Department Universitas Gadjah Mada

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Fluid Inclusion Study Of The Polymetallic Epithermal Quartz Veins At Soripesa Prospect Area, Sumbawa Island, Indonesia Kant, Win; Warmada, I Wayan; Idrus, Arifudin; Setijadji, Lucas Donny; Watanabe, Koichiro
Journal of Applied Geology Vol 4, No 2
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3344.355 KB) | DOI: 10.22146/jag.7199

Abstract

The Soripesa prospect area is located at Maria village, Wawo district, Bima region in the eastern part of Sumbawa Island, Indonesia. This area is a part of Cenozoic Calc-alkaline volcanic inner Banda-Sunda Arc. The dominant lithology of Soripesa prospect area are a lithic-crystal tuff of andesitic and dacitic composition and bedded limestone. There have five main polymetallic epithermal quartz veins in the Soripesa prospect area, namely, Rini vein, Jambu air vein, Dollah vein, Merpati vein, and Arif vein. Those quartz veins are hosted mainly in andesitic volcaniclastic rocks. Fluid inclusion study on those quartz veins is vey important to know the condition of hydrothermal fluids and their origin. Fluid inclusion study is conducted at the laboratory of Earth Resources Engineering Department, Kyushu University, Japan. Homogenization temperature, freeze temperature, eutectic temperature, and melting temperature can be known from fluid inclusion study. Based on fluid inclusion study, formation temperatures of all veins are between 250–260◦C. Melting temperature is between -0.2 to -3◦C. Based on the melting temperature, salinity (wt.% NaCl equiv.) of fluid inclusions is calculated by using Bodnar’s equation. Paleodepth of formations and pressure of trapping are also estimated by using formation temperature and salinity. Based on Hass (1971) diagram, estimated paleodepths of formations are 270 m for Merpati vein, 400 m for Dollah vein, 480 m for Rini vein, 570 m for Arif vein, and 680 m for Jambu Air vein, respectively. Pressure of trapping can also be estimated from depth of formation, density of lithostatic overburden, and gravity; 72 bars for Merpati vein, 106 bars for Dollah vein, 127 bars for Rini vein, 151 bars for Arif vien, and 180 bars for Jambu Air vein, respectively. Keywords: Soripesa, polymetallic quartz veins, homogenization temperature, salinity.
ORE MINERALOGY AND MINERAL CHEMISTRY OF PYRITE, GALENA, AND SPHALERITE AT SORIPESA PROSPECT AREA, SUMBAWA ISLAND, INDONESIA Kant, Win; Warmada, I Wayan; Idrus, Arifudin; Setijadji, Lucas Donny; Watanabe, Koichiro
Journal of Applied Geology Vol 4, No 1
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (3683.914 KB) | DOI: 10.22146/jag.7191

Abstract

The Soripesa prospect area is located at Maria village, Wawo district, Bima region in the East Sumbawa Island, Indonesia. Lithology is dominantly composed of a lithic-crystal tuff of andesitic and dacitic composition and bedded limestone. The polymetallic epithermal quartz veins are hosted by andesitic volcaniclastic rocks. Within these veins, multiphases, colloform-crustiform, bedding to massive textures with pyrite, sphalerite, galena, chalcopyrite, chalcocite, azurite, and malachite are observed. Selected samples were analyzed by using ore microscopy and SEM-EDX. Ore minerals show replacement, ex-solution, colloform, and zonal textures. The paragenesis diagram was made from a careful study of polished sections and thin sections. Textures of ore minerals such as banded, exsolution, replacement, and zone, have been interpreted to correspond to the order of deposition. In pyrite, the average content of Co (0.45 wt.%) is higher than Ni content (0.14 wt.%) and it means that their origin may be hydrothermal origin. Average content ratio, Co:Ni is 2.81. Galena shows a low Ag content of 0.07 %in average. But they show a high Au content of 1.48 %in average. Sphalerite shows a low Fe content of 1.04 %in average and occasionally chalcopyrite inclusion/disease also occurred. Ga and Ge contents are also high in sphalerite. Co>Ni in pyrite, low content of Ag in Galena, low content of Fe and mole % FeS in sphalerite, high content of Ga and Ge, and log (Ga/Ge) in sphalerite, show that pyrite, galena, and sphalerite from Soripesa prospect area were formed under low temperature condition of hydrothermal fluid. Keywords: Ore textures, paragenesis, deposition, hydrothermal fluid, low temperature