I. Setiawan, I.
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PARAGENESA MINERAL BIJIH SULFIDA HIDROTERMAL DI DAERAH KLUWIH KABUPATEN PACITAN JAWA TIMUR : PENDEKATAN BERDASARKAN MINERALOGI DAN INKLUSI FLUIDA Sudarsono, Sudarsono; Setiawan, I.
Jurnal Geologi dan Sumberdaya Mineral Vol 22, No 1 (2012): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Abstract

Hydrothermal activity in Kluwih, Tulakan Pacitan area East Java indicated by rock alteration zone, sulphide mineralization, and quatz vein NNE-SSW, NNW-SSE trend. Mineralization deposited at least in 6 stages, yaitu : 1st stage, pre mineralization deposited quatz (320°C), 2nd stage, deposited quartz + pyrite (290°C), 3rd stage, deposited quartz + pyrite + chalcopyrite + bornite ± galena ± sphalerite (260°C), 4th stage, deposited quartz + pyrite + cahalcopyrite + Tetrahedrite + bornite ± galena (220°C), 5th stage, deposited quartz + pyrite (200°C), and 6th stage or supergen stage, deposited secondary mineral (covellite, malachite, azurite) <100 °C. The hydrothermal system was able in Kluwih Pacitan and surrounding area interpreted as epithermal low suphidation system, or base metal horizon to precious metal horizon. Hydrothermal process initially by propilitic alteration and deposited of sulphides and quartz vein, then argilic alteration overprint both. Finally, surface erosion outcropted those deposits at surface.Key words : hydrothermal, mineralization, sulphide ore, Pacitan
KARAKTER DAN TIPE MINERALISASI HIDROTERMAL DI WILAYAH BOMBANA BERDASARKAN STUDI MINERALOGI DAN GEOKIMIA Setiawan, I.; Indarto, S.; Ismiyanto, AF.; Sudarsono, Sudarsono
Jurnal Geologi dan Sumberdaya Mineral Vol 22, No 3 (2012): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Abstract

Bombana gold mineralization occurs within metamorphic rocks hosted environment, and it's not yet reported having connection with magmatisme/volcanisme. Therefore most ore mineral deposits have to be related with volcanisme bearing metallic mineralization. The aim of this study is to explain the character and types of gold deposit using petrography, mineragraphy, fluid inclusions, AAS, and geochemistry methods.Bombana area formed by orogenic activities which is composed by metamorphic rocks mainly consists by greenschist facies and ultra mafic rocks. Petrographically rocks called as garnet glaukofane amphibol schist, peridotite, serpentinite, sandstone meta, limestone meta, andesite meta, and altered rocks. While based on major elements composition, their parent rocks has ultrabasic-acidic rocks composition, formed peridotite to andesite.Gold mineralization of Bombana area indicates an epithermal-mesothermal type, which is exhibited by hydrothermal evidences such as crosscut veins after foliation and alteration at vicinity of quartz/calcite veins. These indicate that mineralization resulted by hydrothermally process and formed after metamorphism. Ore minerals consisted of gold, pyrite, chalcopyrite, goethite, lepidocrocite and cinabar and commonly associated with quartz veins as mineralized fluids suggested as low salinity (0,18-1,78)% NaCl equivalent and water rich mineralized fluid, at (210-350)ºC temperatur ranges.Keywords: Bombana, volcanic rocks, epithermal, metamorphism
PERKEMBANGAN CEKUNGAN ANTAR-BUSUR DI DAERAH MAJALENGKA-BANYUMAS: SEJARAH TEKTONIK KOMPLEKS DI WILAYAH BATAS KONVERGENSI Permana, H.; Putra, P. S.; Ismiyanto, A. F.; Setiawan, I.; Hendrizan, M.; Mukti, M. M.
Jurnal Geologi dan Sumberdaya Mineral Vol 21, No 2 (2011): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Abstract

An intra-arc basin, Late Miocene to Pliocene in age in the region of Majalengka - Banyumas area has been an interesting theme to be discussed. The volcanoclastic sediments pathway in this basin showing different direction compare to the time equivalent sediments in the adjacent Bogor Trough. Bouguer anomaly analyses clearly imaged the E-W regional structural grains of Bogor – Bandung –Majalengka crosscut pair of NW-SE Gabon dan Pamanukan-Karangbolong strike slip fault that parallel with the postulated intra-arc basin. These NW-SE structural lineaments could be responsible for the development of sub-basins and volcanic products through splay or duplex fault or pull apart mechanism in context oblique plate subduction in Early Miocene. Study of Majenang sub-basin, whereas epiclastic rocks deposited as sediment-gravity flows and their pyroclastic, shows the significance variation, upper, middle slope to basinal plain within the deep sea submarine-fan complex of the Late Miocene-Pliocene age during the development of this basin. The source of sediment deposits was associated with calk alkalin back arc volcanic edifice that grown and separated the sub-basins and other volcanoclastic source from Southern Mountain (Old Andesite Formation). The development of this basin indicates complex history since this region is now inverted and built the mountain range. Therefore further tectonic reconstruction in this region is required for better understanding the geologic history merit further geological exploration prospect.Keywords: intra-arc basin, volcanoclastic, Bouguer anomaly, sediment-gravity flows, back arc volcanic, calk alkalin