Geochemistry and Mineralization Characteristic of Sungai Mak Deposit in Gorontalo, Northern Sulawesi, Indonesia

Abstract

This study reports geochemistry and mineralization characteristics of Sungai Mak deposit in Gorontalo, Northern Sulawesi, Indonesia. SiO₂ and K₂O+Na₂O (Total Alkali Silica or TAS diagram) show that the intrusive rock found in this deposit are granodiorite. Ore minerals consist of chalcopyrite, pyrite, bornite, digenite and covellite which were confirmed by microscopy and SEM-EDS analysis of polished section. Gold mineralization was confirmed by X-ray Fluorescence Analysis. The result of plotted gold grade and copper grade show a positive relationship showing a similarity to another porphyry copper deposit in Tombolilato Distrit located in the southern part of the studied area. By characteristic of combination of ore minerals, there is boundary of primary sulfide zone and intrusive rock in around 160 m from surface. As a result of measurement of the gas-liquid two-phase fluid inclusions that were contained in quartz stock work (width 1 - 3cm), salinity is 2.4-17.8%, homogenization temperature is 282-326ºC (mode value 320ºC). The alteration mineral of intrusive rock was identified by thin section observation and XRD was quartz, chlorite, illite and pyrophyllite. From observation of thin section, hornblende and plagioclase was confirmed as rock forming mineral and these show porphyritic structure.