ZONATION OF ALTERATION AND GEOCHEMISTRY OF AU-AS ELEMENT IN SKARN AU DEPOSIT, WANAGON, ERTSBERG DISTRICT, PAPUA

• Main Author: KARTIKASARI (NIM : 12011078), LUCY
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/22924
• Institution: Institut Teknologi Bandung

Wanagon is one of Skarn-Au deposit in contract area of Freeport Indonesia Company with 0,96 ppm average content of Au. Wanagon is located in three kilometer westward of Grasberg, at coordinate 731520mT-732200mT and 9549140mU-9549620mU. This research has been done to determine the zonation of alteration, zonation of mineralization, and correlation of Au-As element by analyzing eleven wells, those are, WD31-01, WD31-02, WD31-03, WD31-04, WD27-02, WD27-05, WD23-03, WD23-04, WD19-01, WD19-04, and BGT-06 by <br /> <br /> macroscopic analysis, microscopic analysis (petrography and mineragraphy), NIR analysis, and geochemical assay analysis. Based on those analysis, stratigraphic of the research area consist of four unit lithology. Those are, Late Cretaceous Quartz Sandstone, Late Cretaceous <br /> <br /> Limestone, Paleocene Limestone-Dolostone, which is cut by Pliocene Andesite Intrusion. The research area had gone through hydrothermal alteration process and develop six zonation of alteration, they are the (1) Calcite-Andradite-Chlorite Zone, (2) Actinolite-Tremolite-Epidote Zone, (3) Chlorite-Biotite Zone, (4) Pyrophylite-Serisite-Quartz Zone, (5) Epidote-Chlorite-Kaolinite Zone, and (6) Calcite- <br /> <br /> Chalcedony-Montmorilonite Zone. While the mineralization zone divided by Pyrite Zone and Sphalerite Zone. Direct comparison Au-As in research area have 0,2174 correlation coefficient, that mean statistically those elements have no correlation at all. Yet those elements have spatial assosiation. Au with >4ppm content associate with >500ppm content of As. The dissemination of both elements following the orientation of Wanagon Mill Fault that the main structure in the research area. Alteration process in research area begin with forming the (1) Zone that <br /> <br /> equivalent with prograde process, then continued with forming of (2) Zone that equivalent with retrograde process. The (3), (4), (5), and then (6) Zone formed by <br /> <br /> decreasing temperature, pressure, and concentration of hydrothermal fluids. The forming of mineralization in research area associated with Calcite-Andradite Zone, <br /> <br /> Actinolite-Tremolite-Epidote Zone, and Epidote-Chlorite-Kaolinite Zone. Those zone associated with Pyrite and Sphalerite Zone with 10-40% percentage and become an economic Au zone which could be an Au mining target.