GEOLOGY AND GOLD MINERALIZATION OF MOUNT PONGKOR BOGOR REGENCY WEST JAVA IN SUPPORTING THE PLANNING OF GOLD MINING

• Main Author: Bounathone, Konethasine
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/77255
• Institution: Institut Teknologi Bandung

The Pongkor gold mining area is located geographically between 106 ° 31 '27 "- 106 ° 35' 56" East Longitude and 60 34 '30 "- 60 41' 47" south latitude. Administratively, included in Nanggung District, Leuwiliang and Cigudeg District, Bogor Regency, West Java Province. Research sites are located about 80 km southwest from Jakarta. Gold mining in this area applies the system of underground mine by cut and fill method. Stratigraphic study area is composed by four rocks of units. That is tuff breccia unit, The unit is correlated with the Old Andesite Formation of Early Miocene age; lapilli tuff unit, The unit is correlated with the Early Miocene Cimapag Formation; andesite unit, Based on its intrusive relationship with the Old Andesite Formation, Cimapag Formation and Middle Miocene Bojongmanik Formation a Middle Miocene age is assumed for the Andesite unit; breccias unit, where it forms the edge of the Tertiary window through the younger volcanic, they unconformably overlay the Bojongmanik Formation and Andesite unit, based on these relationships a Plio-Plistosen age is assumed. The purpose of the research was to determine the type of lithology and characterize the type of ore alteration and mineralization. Methodology used includes: Data Collection, Data Processing and Data Analysis. Several methods used for the analysis include petrography, mineragraphy, X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) rocks chemistry. Based on petrographic observations and XRD (X-Ray Difraction), it can be concluded that the lithologic constituent can be classified into igneous rocks of andesitic lava and pyroclastic tuff breccia, lapilli tuff, and quartz veins as well as carbonate vein. Inspired by the division of a set of mineral alteration zones, the areas of research can be grouped in three clusters of certain alteration minerals, that is clay mineral, chlorite, quartz, carbonate and sericite alteration zone, and chlorite, quartz, carbonate and epidote alteration zone, and clay mineral, opaque mineral. From the mineragraphy observation, opaque minerals contained in the study area obtained sulfide minerals, namely pyrite, chalcopyrite, sphalerite and digenite that are generally present as a smooth distribution of anhedral, subhedral, euhedral, filling cavities or inclusions in other minerals. Low and high grade gold in this study are not found. The absence of gold minerals in the mineragraphy analysis interpreted as the result of size that may be too subtle which can be associated with digenite or with other chalcopyrite set a sulphide minerals.