STUDY ALTERATION, MINERALISATION, AND GEOCHEMISTRY OF EPITHERMAL LWO SULPHIDATINO SYSTEM, CGD PROSPECT, MOUNT PONGKOR, BOGOR, WEST JAVA

• Main Author: Abdullah Marzuqi, Sayyid
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/52609
• Institution: Institut Teknologi Bandung

Epithermal deposit is one of the main deposit for producing precious metal. Indonesia has more than one valuable epithermal deposit which is Pongkor Mountain is one of them, Gunung Pongkor is epithermal low sulphidation deposit type. Data collecting has done by detailed underground mapping and core logging of three drillhole with the aim for describe geology, alteration, texture variations and mineralization. Fire assay analysis has done to estimate Au - Ag grade in three borehole and multi-element ICP-OES in one borehole. These area consist of three main lithology, it is acrretionary lapili tuff, tuff breccia, and lapili tuff. Geological structure in Pongkor Area has dominated by conjugate strike – slip with main orientation is NW – SE and NNE – SSW which is controlled the mineralization. There are four alteration zone; zone of silica + illite + smectite ± chlorite, smectite + illite ± chlorite, smectite + chlorite ± illite, and chlorite + smectite ± calcite ± illite. There are four mineralization vein facies in the study area and one post-mineralisation vein facies. There are three main phase of mineralization concluded by probabillity curve analysis, phase one is CQ facies that have been formed dominantly distributed in the south block of prospect which has the lowest grade, and dominantly replacement vein texture. In the second pase, facies MOQ and BOQ have been formed predominantly at the north block of prospect, which has well developed banded vein texture. And the third mineralization phase is GSQ facies that have been formed in the southwest prospect, which has dominantly banded texture like crustiform – colloform and ginguro as known as fingerprint for boiling proses. And the post-mineralization vein facies is LGQ facies with vuggy silica texture. Based on the result of elemental correlation analysis on pathfinder it was obtained that Au – Ag – Pb – Zn element was correlated, which maybe can be found in grey sulphide band.