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KARAKTERISTIK ENDAPAN EMAS EPITERMAL SULFIDASI TINGGI DAN HUBUNGANNYA DENGAN MINERAL LEMPUNG HASIL ANALISA SPEKTRAL, DAERAH CIJULANG, KABUPATEN GARUT PROVINSI JAWA BARAT Purwanto, Sigit Heru; Verdiansyah, Okki
Jurnal Ilmiah MTG Vol 6, No 2 (2013)
Publisher : Magister Teknik Geologi Program Pascasarjana UPN ”Veteran” Yogyakarta

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Abstract

Eksplorasi mineral bijih terutama emas saat ini memiliki target eksplorasi pada berbagai tipe endapan.Mineralisasi regional daerah Jawa Barat terdiri dari berbagai tipe endapan seperti endapan emas epitermal sulfidasi rendah (Cikotok, Cikidang, Pongkor), endapan porfiri (Cihurip, Jampang), vein epitermal Au–Zn,Pb,Cu (Arinem), tipe sulfidasi tinggi (Cibeureum, Cijulang).Geologi daerah Cijulang terdiri dari satuan andesit, crystalline tuff, phreatomagmatic breccia, juvenile rich phreatomagmatic breccia, dan microdiorite yang merupakan anggota Formasi Koleberes dan Formasi Jampang berumur Miosen akhir yang tertutup oleh satuan vulkaniklastik muda berumur Pleiosen.Endapan sulfidasi tinggi daerah Cijulang memiliki alterasi advanced argillic, argillic, propilitic, dan silisifikasi (massive quartz – vuggy quartz) dan mineralisasi terbentuk pada 3 fase yaitu pembentukan silika-pirit, enargit-kalkopirit, dan enargit-tenantit-kalkopirit-sfalerit-galena-stibnit.Analisa Terraspectral geology dominan yang dijumpai adalah kaolinit, dikit, pirofilit, sedangkan alunit hanya setempat dijumpai.Pola geokimia endapan emas high sulfidation epithermal daerah Cijulang berasosisasi dengan alterasi silifikasi (massvie quartz), dengan hubungan positif terhadap keberadaan mineral kaolinite-dickite yang berasosiasi oleh kehadiran pyrrophillite sebagai mineral penciri pathway mineralisasi emas. Pada alterasi advanced argillic terlihat terdapat juga anomali kehadiran emas (<0.2 ppm Au), yang berasosiasi dengan kehadiran pyrrophillite-kaolinite-dickite.Model lithocap Cijulang merupakan tipe cebakan sulfidasi tinggi yang berhubungan dengan tipe porfiri, yang berkembang pada tubuh diatrem.
A DESKTOP STUDY TO DETERMINE MINERALIZATION USING LINEAMENT DENSITY ANALYSIS AT KULON PROGO MOUNTAINS, YOGYAKARTA AND CENTRAL JAVA PROVINCE, INDONESIA Verdiansyah, Okki
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.
Caldera of Godean, Sleman, Yogyakarta: A Volcanic Geomorphology Review Hartono, Hill Gendoet; Sudradjat, Adjat; Verdiansyah, Okki
Forum Geografi Vol 31, No 1 (2017): July 2017
Publisher : Universitas Muhammadiyah Surakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23917/forgeo.v31i1.2821

Abstract

Godean hills is located approximately 10 km westward from the Yogyakarta City. The landscape of Godean hills and plains is affected by various factors, such as lithology, geological structure, and sub-aerial process. The purpose of this study was to reveal the landscape of Godean. The method consisted of field study, morphological variables assessment, rock sampling, and laboratory analysis. The results of field mapping indicated that the landscape of Godean  is an isolated hill with a steep slope of >40° and an elevation of +231 m a.s.l, passed by the rivers flows from northeast to southwest that disembogue into the west part of Kulon Progo. The morphologhy of Godean hills varies including G. (Gunung/Mountain) So (+173 m amsl), G. Gede (+218 m a.s.l), G. Wungkal (+187 m a.s.l), G. Butak (+154 m a.s.l), and G. Berjo ( + 175 m a.s.l), dominated by the lithology of igneous rock, which is composed of porphyry andesite-microdiorite, pumice lapilli, and quartz rich lapilli-tuff. In addition, most of the igneous rocks have weathered and have been altered to clays, while the deposition from Merapi volcano formed a landscape with an altitude between +100–+150 m a.s.l surrounding Godean hills. Sentolo Formation was found in Kembang, Bantul, which is located approximately ±5km in the south of the study area N93ºE/12º,  while the distribution in the southwest and northeast relatively covers the Godean hills in curve shape. The results of the analysis provide information related with Godean landscape that it is the remains of the volcanic caldera, with various igneous rock types and volcaniclastics deposits, as well as endured the occurrences of hydrothermal alteration and mineralization. Further geophysical research is required to determine the configuration of igneous rocks under the earths surface.
FLUID INCLUSION STUDIES OF THE EPITHERMAL QUARTZ VEINS FROM SUALAN PROSPECT, WEST JAVA, INDONESIA Tun, Myo Min; Warmada, I Wayan; Idrus, Arifudin; Harijoko, Agung; Verdiansyah, Okki; Watanabe, Koichiro
Journal of Applied Geology Vol 6, No 2
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (952.327 KB) | DOI: 10.22146/jag.7218

Abstract

Sualan prospect is located at Talegong Sub-district of Garut Regency, West Java, Indonesia. The area constitutes calc-alkaline volcanic and volcaniclastic rocks of Tertiary age. The rocks have experienced regional propylitic and argillic alteration. Fluid inclusions from quartz veins were studied in order to constrain the nature, characteristics and evolution of fluids. Microthermometric measurements on fluid inclusion were carried out by freezing and heating experiment. Temperatures of homogenization (Th) and final melting of ice (Tm) were measured for primary, liquid-dominated, two-phase inclusions. The values of Th range from 160°C to 210°C and salinities range from 0.35 to 4.96 wt.% NaCl equiv. Formation temperature of the quartz veins are estimated at 180°C and 190°C and paleo-depth of formation are at 80m and 140m, respectively. Microthermometric data indicates that fluid mixing and dilution were important processes during the evolution of hydrothermal system. Based on fluid inclusion types, microthermometric data, trapping temperature, paleo-depth, texture of quartz and hydrothermal alteration types, quartz veins from prospect were developed under epithermal environment. Keywords: Quartz vein, fluid inclusions, microthermometry, salinities, formation temperature, paleo-depth, epithermal, Sualan prospect.
HIGH SULFIDATION EPITHERMAL MINERALIZATION AND ORE MINERAL ASSEMBLAGES OF CIJULANG PROSPECT, WEST JAVA, INDONESIA Tun, Myo Min; Warmada, I Wayan; Idrus, Arifudin; Harijoko, Agung; Verdiansyah, Okki; Watanabe, Koichiro
Journal of Applied Geology Vol 6, No 1
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (4446.559 KB) | DOI: 10.22146/jag.7215

Abstract

Cijulang is a high-sulfidation epithermal system hosted in the calc-alkaline rocks of andesite lava and lapilli tuff. Mineralization in the prospect is characterized by pyrite-enargite-gold and associated acid sulfate alteration. Studies on ore and gangue mineral assemblages and their mutual textural relationships were carried out in order to explore the paragenetic sequence of mineralization. Hypogene mineralization primarily occurs in the silicic core and the advanced argillic zone in the form of massive replacement, fracture-filling veinlets, vug-filling, patches and dissemination. Mineralization is apparently controlled by both lithology and structures. Common ore minerals include pyrite, enargite, luzonite, tennantite, chalcopyrite, covellite, galena, emplectite and Te-bearing minerals. The paragenetic study indicates that the epithermal prospect evolved from an early stage of intense acid leaching resulting in the formation of vuggy silica and advantage argillic mineral assemblage which was followed by the sulfides deposition. Two metal stages were identified during ore deposition: an early Fe-As-S stage and the later Cu-Fe-As-S stage. The former stage is char- acterized high-sulfidation state sulfides such as enargite/ luzonite+covellite whereas a later stage of Cu- Fe-As–S is represented by intermediate sulfidation state sulfides assemblage of tennantite+chalcopyrite. Gold is probably introduced in the early stage within the ore system and more abundant in the late stage. Keywords: Cijulang, high-sulfidation, acid sulfate, mineralization, enargite, paragenetic, metal stages
APLIKASI LINEAMENT DENSITY ANALYSIS UNTUK MEMBATASI POLA KALDERA PURBA GODEAN Verdiansyah, Okki
Jurnal Teknologi Technoscientia Vol 9, No 2 (2017): Vol 9 No 2 Februari 2017
Publisher : IST AKPRIND YOGYAKARTA

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Abstract

Godean area, is an isolated hills that’s occurs on Yogyakarta basin. Volcano occurences in Godean have issued by morphology, lithology and volcanic concepts. Volcanisme and magmatisme on Godean interpreted have similarity with Gajahmungkur – Wonogiri with hydrothermal event occurs. Lineanment Density Analysis used for interpretating the specific pattern, for strength the morphology and geological that have interpreted before. The methods that we used is combining of quantitative and qualitative. Geology of Godean consist of igneous and sedimentary rock with margins of Kulon Progo hill in western side. Caldera morphology, commonly have circular or a half circular pattern, with limited by steep relief. Morphology of Godean have caldera pattern, as a concept and compare with others. LD analysis are using image from slope directional angle processing on SRTM and ASRTER image, and then extract to lineament. Result of lineament extraction there are 9490 lines. Range of density with length from 0 to 9173,21 m/km2 with high value > 2375 m/km2  and count of lineament from 0 to 23 line/km2 with high value > 8 line/km2. Godean have high density with range of length 1930 – 2996 m/km2 or range of counts 9 – 12 line/km2. Base on the pattern, its looks the Godean and surrounding it differ on 3 major sectors, that’s outer rim, secondary rim, and circular  of late central eruption. Diameter of this pattern is wide (8 – 15 km), that must be proven with others geological and geophysical subsurface research.
APLIKASI LINEANMENT DENSITY ANALYSIS UNTUK MEMBATASI POLA KALDERA PURBA GODEAN Verdiansyah, Okki; Hartono, Hill Gendoet
Jurnal Teknologi Technoscientia Vol 9 No 2 (2017): Vol 9 No 2 Februari 2017
Publisher : LPPM IST AKPRIND Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (840.785 KB)

Abstract

Godean area, is an isolated hills that’s occurs on Yogyakarta basin. Volcano occurences in Godean have issued by morphology, lithology and volcanic concepts. Volcanisme and magmatisme on Godean interpreted have similarity with Gajahmungkur – Wonogiri with hydrothermal event occurs. Lineanment Density Analysis used for interpretating the specific pattern, for strength the morphology and geological that have interpreted before. The methods that we used is combining of quantitative and qualitative. Geology of Godean consist of igneous and sedimentary rock with margins of Kulon Progo hill in western side. Caldera morphology, commonly have circular or a half circular pattern, with limited by steep relief. Morphology of Godean have caldera pattern, as a concept and compare with others. LD analysis are using image from slope directional angle processing on SRTM and ASRTER image, and then extract to lineament. Result of lineament extraction there are 9490 lines. Range of density with length from 0 to 9173,21 m/km2 with high value > 2375 m/km2  and count of lineament from 0 to 23 line/km2 with high value > 8 line/km2. Godean have high density with range of length 1930 – 2996 m/km2 or range of counts 9 – 12 line/km2. Base on the pattern, its looks the Godean and surrounding it differ on 3 major sectors, that’s outer rim, secondary rim, and circular  of late central eruption. Diameter of this pattern is wide (8 – 15 km), that must be proven with others geological and geophysical subsurface research.
PETROGENESA BATUAN INTRUSIF GUNUNG BERJO - BUTAK, DAERAH GODEAN BERDASARKAN DATA PETROGRAFINYA Verdiansyah, Okki
KURVATEK Vol 2 No 1 (2017): April 2017
Publisher : Institut Teknologi Nasional Yogyakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.33579/krvtk.v2i1.550

Abstract

Daerah Godean merupakan bagian dari vulkanisme Miosen, yang tersisa pada daerah Yogyakarta bagian tengah. Vukanisme pada daerah Godean, diperkirakan sebagai produk dari busur gunungapi kepulauan dengan diferensiasi yang terbentuk mulai dari andesit basaltik, andesit dasitik, dasit, riodasit, dan kembali menjadi andesit basaltik. Penelitian dilakukan pada batuan beku pada gunung Berjo, gunung Butak, batuan intrusi subvulkanik dengan orientasi sebaran selatan- timurlaut. Analisis data menggunakan petrografi sebanyak 17 sayatan tipis untuk melihat mineralogi dan tekstur khusus yang terdapat dalam batuan. Morfologi daerah penelitian berupa bukit terisolir dengan kelerengan 51 – 56 %, merupakan produk denudasional yang dikelilingi endapan kuarter dari fluvio-vulkanik gunung Merapi. Litologi pada gunung Berjo dan gunung Buthak terdiri dari andesit piroksen, dasit, andesit, basalt piroksen, yang merupakan batuan intrusi dangkal (subvolcanic intrusion) dengan tekstur utama berupa intersitial, mortar, porfiritik  yang diikuti tekstur khusus berupa oscilating zoning, sieve, dan miarolitic cavities terisi epidot-feldspar-kuarsa sebagai indikasi proses magmatic-hydrothermal pada suhu ± 200 - 400ºC diikuti alterasi hidrotermal berupa phyllic dan propylitic alteration yang terbentuk pada pH  4-5 dengan temperatur 200-3000C. Petrogenesa batuan gunung Berjo dan Butak diinterpretasi terbentuk sebagai batuan intrusi dangkal pada kedalaman 500 m dari permukaan purba, afinitas magma kapur alkali busur gunung api kepulauan dengan konten air tinggi, yang diikuti proses fraksinasi kristalisasi dengan pergerakan magma intrusi yang relatif melambat dan menerobos batuan sedimen karbonat. Petrogenesa daerah Godean masih perlu diperkuat dengan riset mineralogi lebih detil dan data lain yang mendukung.