Pustaka Ilmiah Universitas Padjadjaran

Abstrak

Studi Alterasi Hidrotermal Daerah Pangkal Jaya, Kecamatan Nanggung, Kabupaten Bogor, Provinsi Jawa Barat

The research area is located at Pangkal Jaya Region, Naggung Subdistrict, Bogor District, West Java Province. The broad of research area approximately 3 x 3 km2as well located in the area of PT. Antam.tbk which geographically located between longitude 106o 32′ 1.28″ BT to 106o 33′ 39.13″ BT and 6o36′ 14.72″ LS to 6o37′ 52.24″ LS. Object of this study was intended to determine the local geological conditions, the relationships and variations of each hydrothermal alteration of research area. The lithostratigraphic units are Andesite Lava Units (Tmlv), Andesite Breccia Units (Tmbx), Tuff Units (Tmt), Tuff Lapilli Units (Tmtl), and Alluvium Units (Qa). The geological structure of the study area is Sinistral Fault Cikaniki and Dextral Fault Cikaniki. The results of the observation and collecting data in the field, then performed petrographic analysis, mineragraphic analysis, PIMA (Analytical Portable Infrared Mineral Analyser) and obtained some of clay alteration mineral that remarked the hidrothermal alteration zone with reference to the Leach classification (in Corbett and Leach, 1996). The alteration zone can be devided into three groups, there are : Montmorilonite and Chlorite Zone.

Daerah penelitian terletak pada Daerah Pangkal Jaya, Kecamatan Nanggung, Kabupaten Bogor, Provinsi Jawa Barat. Luas daerah penelitian kurang lebih 3 x 3 km2. Daerah penelitian merupakan kawasan Eksplorasi Emas PT. Antam.tbk. Secara geografis daerah penelitian terletak diantara garis bujur 106o 32′ 1.28″ BT sampai 106o 33′ 39.13″ BT dan 6o36′ 14.72″ LS sampai 6o37′ 52.24″ LS. Tujuan penelitian dimaksudkan untuk mengetahui kondisi geologi daerah penelitian serta untuk mengetahui hubungan dan jenis ubahan hidrotermal daerah penelitian. Urutan litostratigrafi daerah Pangkal Jaya terbagi atas 4 yaitu Satuan Lava Andesit (Tmlv), Satuan Breksi Andesit (Tmbx), Satuan Tuf (Tmt), Satuan Tuf Lapili (Tmtl) dan Endapan Alluvium (Qa). Struktur geologi daerah penelitian terdiri atas Sesar Mendatar Sinistral Cikaniki dan Sesar Mendatar Dekstral Cikaniki. Hasil pengamatan serta pengambilan data di lapangan, selanjutnya dilakukan analisis petrografi, mineragrafi, beserta PIMA (Analytical Portable Infrared Mineral Analyser), dan didapat beberapa jenis mineral lempung yang menandakan adanya ubahan hidrotermal batuan yang mengacu pada klasifikasi Leach (dalam Corbett dan Leach, 1996). Zona ubahan dapat dibagi menjadi tigaa zona, yaitu : zona alterasi monmorilonit dan zona klorit.