Ore Characteristics and Fluid Inclusion of the Base Metal Vein Deposit in Moncong Bincanai Area, Gowa, South Sulawesi, Indonesia

Asmariyadi, R. Langkoke, A. Maulana, I. Nur, and W. Astaman

ABSTRACT

This paper is dealing with ore characteristics and fluid inclusion of the Moncong Bincanai, Biringbulu Subregency of Gowa Regency, South Sulawesi Province, Indonesia. The mineralization is a vein type, with the orientation of N170^oE /65^oSW, hosted in open-space filling within basalt. The mineralization consists of galena, sphalerite, chalcopyrite, and pyrite. Vein thickness ranges from 5 - 17 cm, showing a crustiform banding texture, with a sequence from outer to centre: quartz, carbonate (siderite), sulphide. The quartz displays primary growth textures such as comb, crystalline, saccharoidal, and colloform. Analytical methods applied include AAS and fluid inclusion microthermometry. Chemical composition of the vein indicates an average of Pb = 47.92%, Cu = 1.27%, Zn = 1.02%, and Fe = 9.46%, which shows a significant concentration of Pb. Fluid inclusion microthermometry results indicate a range of formation temperature of 240^o - 250^oC and salinity of the responsible hydrothermal fluid of 2.1 - 2.5 wt.% NaCl eq. The deposit is categorized into low-sulfidation epithermal deposits, which was formed within a range of 410 - 440 m below paleosurface.

Keywords: epithermal vein, base metal, ore mineralization, fluid inclusion.

SARI

Tulisan ini membahas karakteristik bijih dan inklusi fluida pada daerah Moncong Bincanai, Kecamatan Biringbulu, Kabupaten Gowa, Provinsi Sulawesi Selatan, Indonesia. Tipe mineralisasi berupa urat dengan orientasi N1700 ^oE/65 ^oW yang terdapat sebagai pengisi retakan dalam basal. Mineralisasi terdiri atas mineral galena, sfalerit, kalkopirit, dan pirit. Tebal urat antara 5 - 17 cm. Tekstur urat yaitu symmetric crustiform banding, dengan urutan dari luar ke dalam: kuarsa, karbonat (siderit), dan lapisan sulfida yang didominasi galena. Kuarsanya memperlihatkan tekstur pertumbuhan primer yaitu dari tekstur comb, kristalin, saccaharoidal, dan colloform. Metode analisis yang digunakan yaitu AAS dan mikrotermometri inklusi fluida. Berdasarkan hasil analisis pada percontoh urat, kadar rata-rata unsur Pb = 47,92%, Cu = 1,27%, Zn = 1,02%, dan Fe = 9,46%. Hal ini menunjukkan konsentrasi mineralisasi Pb yang cukup potensial. Dari hasil pengamatan inklusi fluida pada urat kuarsa didapatkan kisaran temperatur 240 - 250^oC serta salinitas antara 2,1 - 2,5 wt.% NaCl eq. Endapan tersebut termasuk dalam lingkungan epitermal sulfidasi rendah yang terbentuk pada kedalaman sekitar 410 - 440 m di bawah permukaan purba.

Kata kunci: urat epitermal, logam dasar, mineralisasi bijih, inklusi fluida

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