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All Journal IJOG : Indonesian Journal on Geoscience Jurnal Geologi dan Sumberdaya Mineral (Journal of Geology and Mineral Resources) Jurnal Geologi dan Sumberdaya Mineral (Journal of Geology and Mineral Resources)
Rum Yuniarni, Rum
Centre for Geological Survey Jln. Diponegoro 57 Bandung 40122
Chemistry Earth & Planetary Sciences Education Energy Engineering Environmental Science

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Genesis of Pb-Zn-Cu-Ag Deposits within Permian Carboniferous-Carbonate Rocks in Madina Regency, North Sumatra Harahap, Bhakti Hamonangan; Abidin, Hamdan Zainal; Gunawan, Wahyu; Yuniarni, Rum
Indonesian Journal on Geoscience Vol 2, No 3 (2015)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (9477.449 KB) | DOI: 10.17014/ijog.2.3.167-184

Abstract

DOI:10.17014/ijog.2.3.167-184Strong mineralized carbonate rock-bearing Pb-Zn-Cu-Ag-(Au) ores are well exposed on the Latong River area, Madina Regency, North Sumatra Province. The ore deposit is hosted within the carbonate rocks of the Permian to Carboniferous Tapanuli Group. It is mainly accumulated in hollows replacing limestone in the forms of lensoidal, colloform, veins, veinlets, cavity filling, breccia, and dissemination. The ores dominantly consist of galena (126 000 ppm Pb) and sphalerite (2347 ppm Zn). The other minerals are silver, azurite, covellite, pyrite, marcasite, and chalcopyrite. This deposit was formed by at least three phases of mineralization, i.e. pyrite and then galena replaced pyrite, sphalerite replaced galena, and pyrite. The last phase is the deposition of chalcopyrite that replaced sphalerite. The Latong sulfide ore deposits posses Pb isotope ratio of 206Pb/204Pb = 19.16 - 20.72, 207Pb/204Pb = 16.16 - 17.29, and 208Pb/204Pb = 42.92 - 40.78. The characteristic feature of the deposit indicates that it is formed by a sedimentary process rather than an igneous activity in origin. This leads to an interpretation that the Latong deposit belongs to the Sedimentary Hosted Massive Sulfide (SHMS) of Mississippi Valley-Type (MVT). The presence of SHMS in the island arc such as Sumatra has become controversial. For a long time, ore deposits in the Indonesian Island Arc are always identical with the porphyry and hydrothermal processes related to arc magmatism. This paper is dealing with the geology of Latong and its base metal deposits. This work is also to interpret their genesis as well as general relationship to the regional geology and tectonic setting of Sumatra.
PROSPECT OF MINERAL DEPOSITS IN THE CENTRAL FLORES ISLAND, EASTERN INDONESIA Harahap, Bhakti H; Abidin, Hamdan Z; Utoyo, Harry; Djumhana, Duddy; Yuniarni, Rum
Jurnal Geologi dan Sumberdaya Mineral Vol 16, No 1 (2015): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (416.551 KB)

Abstract

Field data on the Central Flores Island, Eastern Indonesia (Sikka and Ende Regencies) together with chemical analyses allow us to discuss the prospect of mineral occurrences in this inner arc volcanic zone. Geologically, the area is dominated by Tertiary-Quaternary volcanic and sedimentary rocks, sitting unconformably on the siliceous sedimentary basement of Pre-Tertiary ages. The Tertiary volcanic rocks referred to as Kiro Formation consist of tuff, andesite lava, breccia and green tuff, while the sedimentary rocks are dominated by sandstone and claystone. The Pre-Tertiary basement rocks and the Kiro Formation were intruded by Late Miocene granite, granodiorite, diorite and andesite resulted in hydrothermal alteration and mineralization. The identified hydrothermal alteration includes chlorite, zeolite, kaolinite, jasper and silica. Ores deposits are represented by iron ore, manganese, gold, base metal and iron sands. Style of mineralization is disseminated features, cavity filling, replacement and veins. In general, quartz veins show vuggy, comb and bossa / bladed pseudomorph calcite texture. Sample analyses from quartz veins show that gold (Au) value ranges from 3 - 39 ppm, copper (Cu) : 15-133 ppm, lead (Pb) : 9 - 123 ppm, Zinc (Zn) : 7 - 31 ppm. Within silicified rocks, gold value ranges from <2 - 5 ppm, Cu : 6-546ppm, Pb : 28 - 1181 ppm, Zn : 18-3906 ppm. In contrast within altered rocks, Au : <2-55ppb, Cu : 9-199 ppm, Pb : 24 - 54 ppm, Zn: 40 - 142 ppm. The content of iron within ore veins range from 45.55 - 60.41%; manganese ranges from 231-8330 ppm (altered rock) and iron sands range from 4.22 - 50.83% magnetite. The result of the preliminary works in the area has been revealed that the Sikka and Ende Regencies could be traced for several mineral deposits occurrences such as epithermal, porphyry, skarn and volcanogenic massive sulfide of Kuroko type. Keyword : sikka, green tuff, skarn, volcanogenic, porphyry, epithermal
Ciri Petrologi dan Geokimia Batuan Terobosan Gunung Sepikul, Trenggalek, Jawa Timur Yuniarni, Rum
Jurnal Geologi dan Sumberdaya Mineral Vol. 25 No. 2 (2024): JURNAL GEOLOGI DAN SUMBERDAYA MINERAL
Publisher : Pusat Survei Geologi

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33332/jgsm.geologi.v25i2.742

Abstract

Gunung Sepikul di bagian selatan Jawa Timur berkaitan dengan proses magmatisme yang berumur Miosen. Maksud penelitian ini untuk mengetahui karakteristik petrologi dan geokimia batuan beku Gunung Sepikul. Tujuannya mengungkapkan gambaran tektonik dan melengkapi data petrologi lajur magmatisme Jawa bagian selatan. Singkapannya berupa stock terdiri atas diorit dan granodiorit. Percontoh batuan dianalisis menggunakan metode petrografi, XRF dan ICP-MS. Data lapangan dan hasil analisa laboratorium berupa komposisi mineral serta geokimia batuan dapat menunjukkan proses magmatisme batuan Gunung Sepikul. Batuan diorit berwarna kelabu, tekstur inequigranular terdiri atas mineral plagioklas, kuarsa, piroksen, hornblenda dan mineral opak. Batuan granodiorit berwarna kelabu cerah, tekstur porfiritik dengan fenokris plagioklas, hornblenda, kuarsa dan mineral opak pada masadasar feldspar dan kuarsa. Berdasarkan analisa geokimia, batuan terobosan ini berafinitas magma Medium-low K series yang berhubungan dengan magmatisme di lingkungan tektonik orogenic. Kata Kunci: terobosan, stock, diorit, granodiorit, magmatisme
Co-Authors Bhakti H Harahap, Bhakti H Bhakti Hamonangan Harahap, Bhakti Hamonangan Duddy Djumhana, Duddy Hamdan Z Abidin, Hamdan Z Hamdan Zainal Abidin, Hamdan Zainal Harry Utoyo, Harry Wahyu Gunawan