#TITLE_ALTERNATIVE#

• Main Author: RIANA NUGRAHA (nim : 12012075), NURESA
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/29777
• Institution: Institut Teknologi Bandung

<p align="justify">The research area is administratively located in Lanut District, Modayag Subdistrict, Bolaang Mongondow Timur Regency, North Sulawesi Province, and geographically located at 662000 - 662400 mE and 74800 – 75250 mN with an area sized 400x450 meters. Riska is an open-pit mine of high-sulfidation epithermal gold deposit within the Contract of Work area of PT. J Resources. Riska pit had stopped producing since Desember of 2015. The purpose of this research is to determine geological condition, design an alterationmineralization zone and determine the correlation between Au-Cu-Ag grade and alterationmineralization zone. To achieve those goals, some methods such as geological and alteration mapping, detailed bore cores logging from 11 different wells, petrographic analysis of 24 samples, mineragraphic analysis of 9 samples, clay mineral analysis using ASD of 40 samples, and assay Au, Cu, Ag geochemistry analysis were used. Lithostratigraphic units of Western Riska pit that formed on Miocene consist of 3 units, they are Lapilli Tuff Unit, Pyroclastic Breccia-Breccia Tuff Unit and Andesitic Lava Unit respectively. All of those units had undergone alteration-mineralization processes on <br /> Pliocene. There are four alteration zones in this research location, they are Alunite-Dickite-Quartz Zone, Quartz-Kaolinite Zone, Smectite-Calcite-Illite±Quartz Zone, and Calcite-Chlorite- Felspar sekunder±Quartz Zone. In this research location, pyrite exist in all alteration zones, <br /> arsenian pyrite/arsenopyrite-enargite-chalcopyrite exist in Alunite-Dickite-Quartz Zone, and bornite-covellite-goethite-hematite exist as supergene minerals. Mineralization paragenesis can be subdivided into two phases: high sulfidation epithermal and supergene oxidation. Supergen mineralization only observed in fractured zone in Quartz-Dickite-Alunite zone at &#8805;680 msl. <br /> High-sulfidation epithermal deposit of Western Riska pit is controlled by geological structure such as ENE – WSW right lateral normal fault that was formed by Inobonto's <br /> regional sinistral faults. High concentration of Au-Cu-Ag ( > cut off grade of Au=0,1 ppm; Cu=1500 ppm; Ag=10 ppm) is associated with Alunite-Dickite-Quartz zone, hydrothermal breccia zone, and supergene zone.<p align="justify">