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All Journal Indonesian Journal of Geography Jurnal Geomine Prosiding Seminar Nasional Rekayasa Teknologi Industri dan Informasi ReTII
Okki Verdiansyah
Institut Teknologi Nasional Yogyakarta
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A Desktop Study to Determine Mineralization Using Lineament Density Analysis at Kulon Progo Mountains, Yogyakarta and Central Java Province, Indonesia Okki Verdiansyah
Indonesian Journal of Geography Vol 51, No 1 (2019): Indonesian Journal of Geography
Publisher : Faculty of Geography, Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1638.446 KB) | DOI: 10.22146/ijg.37442

Abstract

A geological study was conducted in Kulon Progo and its surrounding areas (Kulon Progo and Purworejo Regency). It focused on regional geology, tectonic configuration, geodynamics and magmatism, lithology and volcanology, and mineralization. Although there has been considerable research of mineralization in the area—particularly in Kokap (Kulon Progo Regency), Bagelen (Purworejo Regency) and Gupit (Magelang Regency), the potential of precious metals has not been determined due to data limitations. The study combined qualitative and semi-quantitative methods using a desktop geologic analysis, which facilitates lithology interpretation, volcanic boundary system, and lineament density assessment. The geology of the region is composed of an ancient volcanic complex of the Old Andesite Formation formed during the Late Oligocene-Miocene, and the mineralization in Kokap, Bagelen, and Gupit is epithermal. Based on the analysis results, the mineralization occurs in the central to proximal facies of the paleo-volcano, and the system ranges from 2.2 to 3.8 km in diameter. The manual analysis of the lineament density showed that the main direction of the lineaments was SE-NW with a maximum density of 2025.9 m/km2 and an anomaly limit of >1800 m/km2. In the combined semi-automatic analysis, the maximum density was 8.3 km/km2. The target area of mineralization included four anomalous areas, namely Bagelen-Kokap, Salaman, Kaligesing, and Loano, associated with the central and proximal facies of each small paleo-volcano.
Karakteristik Mineralisasi Endapan Emas Epitermal Sulfidasi Rendah di Daerah Mekarbakti, Kecamatan Bungbulang, Kabupaten Garut, Provinsi Jawa Barat Rangga Bintang Ardaraja; Eddy Winarno; Arifudin Idrus; Okki Verdiansyah; Satriadi Satriadi
Jurnal Geomine Vol 10, No 2 (2022): Edisi Agustus 2022
Publisher : Universitas Muslim Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33536/jg.v10i2.1198

Abstract

The southern mountains of western Java have been known to have large gold deposit potential. The Mekarbakti area, located in Garut regency, is known to have gold-bearing quartz veins, but the distribution and characteristics of these veins are not well recorded. The purpose of this study is to determine the geological conditions of the deposits and the characteristics of the epithermal deposits in the study area, in term of alteration, ore mineralization, vein texture, and ore geochemistry. Field work includes random sampling of veins from surface outcrops and cores. Laboratory analysis includes mineragraphic, geochemical analysis by means of Fire Assay Atomic Absorption Spectrophotometry (FA-AAS) and Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). The lithology of the Mekarbakti area is composed of volcanic rocks including andesite lava, andesite intrusion and pyroclastic rocks such as breccia and tuff. The mapping results show that the hydrothermal alteration that developed is divided into three zones of alteration type, namely the silicification zone (silica + - clay), the argillic zone (kaolinite + - smectite - illite) and the propylitic zone (chlorite - smectite - epidote - illite). Quartz texture is generally dominated by brecciated, colloform, comb, lattice bladed and cockade textures. The texture interpretation of the veins shows a crystalline quartz zone, which is enriched in base metals such as galena, sphalerite and chalcopyrite and a crustiform – colloform zone which usually contains gold and silver. Veins in the study area contain the elevated grades of 3.21 ppm Au and 75.5 ppm Ag.
Studi awal inklusi fluida pada fenokris kuarsa di Hargorojo, Bagelen, Purworejo, Jawa Tengah okki verdiansyah
Retii 2022: Prosiding Seminar Nasional ReTII ke-17
Publisher : Institut Teknologi Nasional Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar

Abstract

The research focuses on dacite intrusion, in the Hargerejo area in the southern Kulonprogo Mountains and administratively in the Begelen District, Purworejo Regency, Central Java Province. The presence of a hydrothermal system in the Kulon Progo area is in the form of low-medium sulfidation epithermal in Kokap, Epithermal - Lithocap in Bagelen, and high-sulfidation epithermal in Menoreh (Magelang). In the case of the Bagelen intrusion, it is suspected that it is part of the hydrothermal system that forms the Au-Ag hydrothermal system. The research uses geological mapping methods and surface sampling on dacite rocks and laboratory observations with polarization and ore microscopy. This study focuses on the character of quartz and the presence of fluid inclusions by using the qualitative concept of fluid inclusion petrography. The lithology of the Bagelen area consists of volcanic breccias, andesite intrusions, dacites, and alluvial deposits. Petrographic analysis of dacite samples showed a porphyritic texture with 55-76% phenocrysts in the form of quartz (8-22%), hornblenda (3-11%), plagioclase (40-55%), surrounded by a bottom mass of volcanic glass and feldspar microlites. , as well as opaque minerals in the form of pyrite and residual magnetite as much as 2-5% and the base mass undergoes diagenesis and is changed to silica. Quartz is divided into types 1 and 2, indicating the presence of primary and pseudosecondary inclusion types. Quartz type 1 (qz-1) shows an irregular distribution and pseudosecondary trail with Type I, II, III inclusions. In type 2 quartz, it is seen that the inclusions are dominated by type II & III or L<V and L>V biphase, with low to high vapor densities. Inclusions in type 2 quartz show a primary pattern and are similar to the general epithermal vein fluid on the surface. The presence of fluid inclusions in the magmatic quartz at Bagelen, indicates the existence of a hydrothermal system formed due to changes in silicate character, and affects the fluid character from magmatic to hydrothermal. Epithermal or related mineralization is more influenced by the presence of type 2 quartz, and subsequent hydrothermal processes. The type of mineralization affected is intermediate sulfidation with a characteristic presence of disseminated pyrite-chalcopyrite in dacite. The fluid that affects mineralization is dominated by the epithermal system. Keyword : Exploration, Fluid, Copper, Gold, Kulon Progo
Co-Authors Arifudin Idrus Eddy Winarno Rangga Bintang Ardaraja Satriadi Satriadi