KARAKTERISTIK ALTERASI -MINERALISASI ENDAPAN EPITERMAL SULFIDASI TINGGI DAERAH KARANGGANDU DAN SEKITARNYA, KECAMATAN WATULIMO, KABUPATEN TRENGGALEK

Abstract

The research location is located in the Karanggandu area and its surroundings, Watulimo subdistrict, Trenggalek Regency, with an area of 4 x 4 at coordinates 8º17’45’’ South Latitude - 8º20’0’’ South Latitude and 111º41’0’’East Longitude - 111º43’0’’ East Longitude. The aim of this research is to identify geological conditions and characteristics of alteration and mineralization in the research area. The methods used in this research are field mapping (geomorphology, geology, hydrothermal alteration), petrography, mineralography, X-ray diffraction (XRD), and atomic absorption spectrophotometers (AAS). Based on the results of the analysis, it was identified into 3 geological units, namely the andesite lava unit, andesite intrusion unit, and dacite intrusion unit with five alteration zoning zones with the help of the X-Ray Diffraction (XRD) analysis method in the research area, namely, vuggy quartz alteration zone, alteration zone advanced argillic (quartz + alunite + diaspor + pyrophyllite), intermediate argillic alteration zone (quartz + illite + kaolinite ± pyrite - chalcopyrite), argillic alteration zone (illite + kaolinite + quartz ± pyrite), and propylitic alteration zone (chlorite ± epidote + quartz ± pyrite). This alteration zone falls into the type of high sulfidation epithermal deposit with characteristic features of overprinting porphyry and vuggy quartz. Based on the mineralization pattern that develops from mineragraphic observations, it shows a special texture in the form of a disseminated texture in the sulfide minerals pyrite and chalcopyrite, an intergrowth/simultaneous texture, and a replacement texture in the covellite, bornite, pyrite, and chalcopyrite minerals replaced by oxide minerals such as hematite, goethite, and jarosite, which characterize the zone change from the hypogene zone to the supergene zone. In the geochemical analysis of the ore using the Atomic Absorption Spectrophotometry/AAS method on 2 samples LP 95 and LP 93, the Au element content value was 1148 (ppb) and 146 (ppb), the Ag element was 6 (ppm) in both samples, and for the element Cu, it was 140 (ppm) and 215 (ppm).