KARAKTERISTIK ENDAPAN EMAS SEDIMENT-HOSTED REPLACEMENT DI DAERAH SIHAYO, KABUPATEN MANDALING-NATAL, SUMATERA UTARA

Nofiya Rahmat, Nayarudin (2013) KARAKTERISTIK ENDAPAN EMAS SEDIMENT-HOSTED REPLACEMENT DI DAERAH SIHAYO, KABUPATEN MANDALING-NATAL, SUMATERA UTARA. Masters thesis, UPN ''VETERAN'' YOGYAKARTA.

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Abstract

Lokasi penelitian terletak di Sihayo yang termasuk dalam wilayah Desa Hutagodang Muda, Kecamatan Siabu, Kabupaten Mandailing Natal, Propinsi Sumatera Utara. Secara astronomis daerah ini terletak antara 099° 25' 31.47" – 099° 26' 20.04" BT dan 00° 55' 0.23" – 00° 56' 4.98" LU. Daerah telitian tersusun atas tiga satuan batuan yaitu satuan batupasir volkanik, satuan batugamping dan satuan batupasir kuarsa; dengan empat bentukan lahan geomorfik yaitu Punggungan Pegunungan Homoklin pada Satuan Batupasir Kuarsa, Lereng Pegunungan Homoklin pada Satuan Batupasir Kuarsa, Lereng Pegunungan Terkikis Kuat pada Satuan Volkanik, dan Lereng Pegunungan Terkikis Kuat pada Satuan Batugamping dengan lereng miring hingga sangat curam. Hasil alterasi hidrotermal pada endapan emas sediment-hosted replacement yang terbentuk meliputi empat jenis yaitu silisifikasi, argilisasi, dekalsifikasi/ dolomitisasi, serta propilitisasi yang terutama dikontrol oleh jenis batuan samping dan struktur geologi. Kumpulan mineral bijih yang terbentuk yaitu meliputi pirit, markasit, pirit-arsenikal, markasit-arsenikal, arsenopirit, stibnit, orpimen, realgar, sinabar, pirargirit, hematit, limonit, dan gutit. Mineralisasi emas lebih umum hadir dalam batuan sedimen karbonat tersilisifikasi menjadi jasperoid oleh proses penggantian dan banyak mengandung mineral-mineral sulfida terhambur. Bentuk endapan bijih biasanya mengikuti lapisan batuan, zona breksi runtuhan, batas ketidakselarasan, zona breksiasi jalur sesar, dan endapan gua purba. Karakteristik alterasi dan mineralisasi secara normal hampir mirip menyerupai endapan epitermal namun endapan ini berbeda dalam batuan samping, tekstur maupun keadaan geologinya lainnya. Kata kunci: emas sediment-hosted, penggantian, host rock, dekalsifikasi, dolomitisasi, silisifikasi, jasperoid, sulfida terhambur The location of research is located at Sihayo, Hutagodang village, Siabu subdistrict, Mandailing Natal Regency, North Sumatra Province. Astronomically this area is located at coordinate between Longitude 099° 25' 31.47" – 099° 26' 20.04" E and Latitude 00° 55' 0.23" – 00° 56' 4.98" N. The area contains of three set of rocks, i.e. unit of volcanic sandstone, unit of limestone, and unit of quartz sandstone; with four geomorphic forms, these are ridge of mountain range of homocline on quartz sandstone unit, slope of mountain range of homocline on quartz sandstone unit, slope of mountain range of strongly denudation on volcanic unit, and slope of mountain range of strongly denudation on limestone unit with slope from moderate sloping to very steep. Hydrothermal alteration assemblage in sediment-hosted replacement gold deposit at Sihayo consists of four types of alterations, i.e. silicification, argillization, decalcification/dolomitization, and propilitization that mainly controlled by host rock and structure. The ore mineralogy assemblage is pyrite, marcasite, arsenical-pyrite, arsenical-marcasite, arsenopyrite, stibnite, orpiment, realgar, cinnabar, pyrargyrite, hematite, limonite, and goethite. Gold mineralisation commonly on silicified of calcareous rock become jasperoid with replacement processes and dissemination of sulphide minerals. The ore body forms at Sihayo generally follow statabound, collapse breccias, unconformity, fault zone (structural), and paleo-cave sediment. Characteristic of alteration and mineralisation normally almost similar with epithermal deposit, but the deposit at Sihayo is different in host rock, textures and other geological condition. Keywords: sediment-hosted gold, replacement, host rock, decalcification, dolomitization, silicification, jasperoid, disseminated sulphides

Item Type: Thesis (Masters)
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Divisions: Faculty of Engineering, Science and Mathematics > School of Engineering Sciences
Depositing User: Erny Azyanti
Date Deposited: 19 May 2016 07:53
Last Modified: 19 May 2016 07:53
URI: http://eprints.upnyk.ac.id/id/eprint/1727

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