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Mineral paragenesis and fluid inclusions of the Bincanai epithermal silver-base metal vein at Baturappe area, South Sulawesi, Indonesia Nur, Irzal; Idrus, Arifudin; Pramumijoyo, Subagyo; Harijoko, Agung; Imai, Akira
Journal of Applied Geology Vol 3, No 1
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2830.054 KB) | DOI: 10.22146/jag.7179

Abstract

The Baturappe prospect located at southern part of Sulawesi island, Indonesia, is a hydrothermal mineralization district which is characterized by occurrence of epithermal silver-base metal deposits. The mineralization is hosted in basaltic-andesitic volcanic rocks of the late Middle-Miocene Baturappe Volcanics. More than 20 units of quartz – base metal veins are distributed in the area, and one of the most significant is the Bincanai vein. This study is aimed to characterize the mineral paragenesis and to elucidate the physicochemical conditions of the formation of the deposit on the basis of mineral assemblage and fluid inclusion mictrothermometry. Sulphide assemblages in the vein indicate an intermediate sulfidation state epithermal; beside galena and sphalerite as the early stage minerals, chalcopyrite, tennantite, and tetrahedrite are also identified as the later stage. Microthermometric study of fluid inclusions in quartz indicates formation temperature of the vein ranges from about 230 to 280°C Histogram of homogenization temperature suggests that there are two generations of hydrothermal fluid responsible for the ore mineralization in the vein; the higher temperature range represents formation temperature of the base metal (galena, sphalerite), while the lower temperature range is correlate with the precipitation of the rest relatively lower temperature sulphides (chalcopyrite, pyrite, tetrahedrite, tennantite, polybasite, and Bi-Ag-Cu-Fe-bearing sulfide). The sequence is also consistent with the mineral paragenetic. The mean of salinity (2.0–2.5 wt.% NaCl eq.) indicates that fluid responsible for the mineralization in the Bincanai vein is relatively low-salinity fluid.
INTERPRETASI SEBARAN MINERALISASI LOGAM EMAS BERDASARKAN NILAI RESISTIVITY MENGGUNAKAN METODE GEOLISTRIK KONFIGURASI WENNER Malik, Maulana; Nur, Irzal; Ilyas, Asran
Jurnal Penelitian Geosains Vol 10, No 2 (2014)
Publisher : Jurnal Penelitian Geosains

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Abstract

The limitation of data and information about distribution of gold mineralization based on the value of resistivity in the hosted rock on WIUP exploration PT. Indi Karya Anugerah which is located in Long Iram, West Kutai, East Borneo becomes the background of this study. The purpose of this study is expected to find the indications of gold mineralization anomalies based on the geophysical data of geoelectrical resistivity value hosted rock, rock contacts, mineralization and the sub-surface distribution. Vertical geoelectrical resistivity inversion using Wenner configuration for eight line of one with the position of the potential electrode and current electrode arranged from C1-P1-P2-C2. Based on the result of resistivity interpretation using software RES2Dinv showed that the lowest resistivity value of materials is 1.23Ωm till the highest one is 119085Ωm with rocks encountered indicated as Latite which was exposed, had a high resistivity. Outcrop of alteration area was found with relatively low resistivity and based on its physical characteristics as well as indication of gold occurrences in rock samples with grade of 2.01 ppm on line 01-line 02 and 2.27ppm on line 08 which were the analysis result in laboratory.Keywords: Survey review, alteration, resistivity, software RES2Dinv, anomalies
THE METAMORPHIC ROCK-HOSTED GOLD MINERALIZATION AT BOMBANA, SOUTHEAST SULAWESI: A NEW EXPLORATION TARGET IN INDONESIA Idrus, Arifudin; Fadlin, Fadlin; Prihatmoko, Sukmandaru; Warmada, I Wayan; Nur, Irzal; Meyer, Franz Michael
Jurnal Geologi dan Sumberdaya Mineral Vol 22, No 1 (2012): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Abstract

Placer gold has been discovered in Bombana, SE-Sulawesi, Indonesia. The placer gold is not associated with volcanic rock-related gold deposits. This paper discusses the primary gold mineralization as the source of the placer gold. The placer gold is possibly derived from gold-bearing quartz veins hosted by Pompangeo Metamorphic Complex (PMC). Pyrite, chalcopyrite, cinnabar, stibnite and tripuhyite are present. Sheared, segmented vein varies in thickness from 2 cm to 2 m. The veins contain erratic gold in various grades from below detection limit (0.005 g/t) to 134 g/t. At least three generations of veins are identified. The first is parallel to the foliations, the second crosscuts the first generation of veins/foliations, and the third is of laminated deformed quartz+calcite veins at the late stage. The first veins are mostly massive to crystalline, occasionally brecciated and sigmoidal, whereas the second veins are narrower than the first and relatively brecciated. Gold grades in the second and third veins are relatively higher than that in first veins. Fluid inclusion study of quartz veins indicates abundant H2O-NaCl and a small amount of H2O-NaCl-CO2 inclusions. Temperature of homogenization (Th) and salinity of the first vein vary from 184.7 to 245.3 ºC and 5.26 to 9.08 wt.% NaCl eq., respectively. The second generation vein was originated at Th of 132.1-283.4 ºC and salinity of 3.55-5.86 wt.%NaCl eq., whereas the third generation vein formed at lowest Th varying from 114 to 176ºC and less saline fluid at salinity range between 0.35 and 4.03 wt.% NaCl eq. Gold is mainly identified in the form of 'free gold' among silicate minerals. Mineralogically, gold is closely related to cinnabar, stibnite, tripuhyite and possibly minor arsenopyrite. Metamorphogenic gold deposits would be the new target of gold exploration in Indonesia.Keyword: Gold mineralization, orogenic-type, Bombana, Southeast Sulawesi, Indonesia
Metamorphic rock-hosted orogenic gold deposit style at Bombana (Southeast Sulawesi) and Buru Island (Maluku): Their key features and significances for gold exploration in Eastern Indonesia Idrus, Arifudin; Prihatmoko, Sukamandaru; Harjanto, Ernowo; Meyer, Franz Michael; Nur, Irzal; Widodo, Wahyu; Agung, Lia Novelia
Journal of Geoscience, Engineering, Environment, and Technology Vol 2 No 2 (2017): JGEET Vol 02 No 02 : June (2017)
Publisher : UIR PRESS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.24273/jgeet.2017.2.2.291

Abstract

In Indonesia, gold is commonly mined from epithermal-, porphyry-, and skarn-type deposits that are commonly found in volcanic belts along island arcs or active continental margin settings. Numerous gold prospects, however, were recently discovered in association with metamorphic rocks. This paper focuses on metamorphic rock-hosted gold mineralization in Eastern Indonesia, in particular the Bombana (SE Sulawesi) and Buru Island (Maluku) prospects. At Bombana, gold-bearing quartz-veins are hosted by the Pompangeo metamorphic complex. Sheared, segmented veins vary in thickness from 2 cm to 2 m. Gold is mainly present in the form of ‘free gold’ among silicate minerals and closely related to cinnabar, stibnite, tripuhyite, and in places, minor arsenopyrite. The gold distribution is erratic, however, ranging from below detection limit up to 134 g/t. At least three generations of veins are identified. The first is parallel to the foliation, the second crosscuts the first generation of veins as well as the foliation, and the late-stage laminated deformed quartz-calcite vein represents the third mineralization stage. The early veins are mostly massive to crystalline, occasionally brecciated, and sigmoidal, whereas the second-stage veins are narrower than the first ones and less subjected to brecciation. Gold grades in the second- and third-stage veins are on average higher than that in the earlier veins. Microthermometric and Raman spectrometric studies of fluid inclusions indicate abundant H2O-NaCl and minor H2O-NaCl-CO2 fluids. Homogenization temperatures and salinities vary from 114 to 283 ºC and 0.35 to 9.08 wt.% NaCl eq., respectively. Crush-leach analysis of fluid inclusions suggests that the halogen fluid chemistry is not identical to sea water, magmatic or epithermal related fluids, but tends to be similar to fluids in mesothermal-type gold deposits. In Buru Island (Gunung Botak and Gogorea prospects), two distinct generations of quartz veins are identified. Early quartz veins are segmented, sigmoidal discontinuous and parallel to the foliation of the host rock. This generation of quartz veins is characterized by crystalline relatively clear quartz, and weakly mineralized with low sulfide and gold contents. The second type of quartz veins occurs within the ‘mineralized zone’ of about 100 m in width and ~1,000 m in length. Gold mineralization is intensely overprinted by argillic alteration. The mineralization-alteration zone is probably parallel to the mica schist foliation and strongly controlled by N-S or NE-SW-trending structures. Gold-bearing quartz veins are characterized by banded texture particularly following host rock foliation and sulphide banding, brecciated and rare bladed-like texture. Alteration types consist of propylitic (chlorite, calcite, sericite), argillic and carbonation represented by graphite banding and carbon flakes. Ore mineral comprises pyrite, native gold, pyrrhotite, and arsenopyrite. Cinnabar and stibnite are present in association with gold. Ore chemistry indicates that 11 out of 15 samples yielded more than 1 g/t Au, in which 6 of them graded in excess of 3 g/t Au. All high-grade samples are composed of limonite or partly contain limonitic material. This suggests the process of supergene enrichment. Interestingly, most of the high-grade samples contain also high concentrations of As (up to 991ppm), Sb (up to 885ppm), and Hg (up to 75ppm). Fluid inclusions in both quartz vein types consist of 4 phases including L-rich, V-rich, L-V-rich and L1-L2-V (CO2)-rich phases. The mineralizing hydrothermal fluid typically is CO2-rich, of moderate temperature (300-400 ºC), and low salinity (0.36 to 0.54 wt.% NaCl eq). Based on those key features, gold mineralization in Bombana and Buru Island tends to meet the characteristics of orogenic, mesothermal types of gold deposit. Metamorphic rock-hosted gold deposits could represent the new targets for gold exploration particularly in Eastern Indonesia.
INTERPRETASI SEBARAN MINERALISASI LOGAM EMAS BERDASARKAN NILAI RESISTIVITY MENGGUNAKAN METODE GEOLISTRIK KONFIGURASI WENNER Malik, Maulana; Nur, Irzal; Ilyas, Asran
Jurnal Penelitian Geosains Vol 10, No 2 (2014)
Publisher : Jurnal Penelitian Geosains

Show Abstract | Download Original | Original Source | Check in Google Scholar

Abstract

The limitation of data and information about distribution of gold mineralization based on the value of resistivity in the hosted rock on WIUP exploration PT. Indi Karya Anugerah which is located in Long Iram, West Kutai, East Borneo becomes the background of this study. The purpose of this study is expected to find the indications of gold mineralization anomalies based on the geophysical data of geoelectrical resistivity value hosted rock, rock contacts, mineralization and the sub-surface distribution. Vertical geoelectrical resistivity inversion using Wenner configuration for eight line of one with the position of the potential electrode and current electrode arranged from C1-P1-P2-C2. Based on the result of resistivity interpretation using software RES2Dinv showed that the lowest resistivity value of materials is 1.23?m till the highest one is 119085?m with rocks encountered indicated as Latite which was exposed, had a high resistivity. Outcrop of alteration area was found with relatively low resistivity and based on its physical characteristics as well as indication of gold occurrences in rock samples with grade of 2.01 ppm on line 01-line 02 and 2.27ppm on line 08 which were the analysis result in laboratory.Keywords: Survey review, alteration, resistivity, software RES2Dinv, anomalies
Survei Geolistrik untuk Pengembangan Irigasi Air Tanah di Kelurahan Lamatti Rilau - Sinjai, Sulawesi Selatan Ramli, Muhammad -; -, Sufriadin; A, Aryanti V; Nur, Irzal; Thamrin, Meinarni; Widodo, Sri
JURNAL TEPAT : Teknologi Terapan untuk Pengabdian Masyarakat Vol 1 No 2 (2018): Improving Quality of Life within Society
Publisher : Faculty of Engineering UNHAS

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Abstract

Daerah Lamatti Rilau-Sinjai Utara merupakan daerah dengan bentang alam yang berbukit-bukit. Kondisi bentang alam tersebut menjadi kendala dalam pemenuhan kebutuhan air irigasi pertanian dengan pemanfaatan air permukaan. Oleh karena itu, diperlukan pengembangan air tanah untuk mensuplai kebutuhan air irigasi tersebut sebagai upaya peningkatan produksi. Pengembangan sumber daya air tanah terdiri atas beberapa tahapan, namun hal yang paling mendasar adalah identifikasi keterdapatan air tanah di bawah permukaan. Metode investigasi yang sangat popular adalah pengukuran tahanan jenis batuan. Nilai tahanan jenis batuan merupakan representasi dari variasi karakteristik fisik dan kimia batuan. Oleh karena itu, hubungan antara jenis batuan dan nilai tahanan jenis merupakan dua hal yang menjadi dasar analisis dalam kegiatan ini. Daerah Lamatti Rilau ? Sinjai Utara tersusun atas material batuan sedimen Formasi Walanae(Tmpw), Batuan Gunungapi Lompobatang (Qlv) dan Endapan aluvium dan pantai (Qac). Pengamatan lapangan menunjukkan sejumlah singkapan batupasir yang berpotensi sebagai lapisan pembawa air. Nilai tahanan jenis batuan tersebut bervariasi dari 2,0 ? 104,0 ohm-m. Variasi nilai tersebut menunjukkan bahwa pada kedalaman tertentu terdapat lapisan pembawa air tanah. Dari 3 titik investigasi geolistrik, titik GL-3 merupakan lokasi yang dapat lakukan pengembangan sumur produksi air tanah dengan kedalaman sumur 100 m.