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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.
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.
KARAKTERISTIK ENDAPAN EMAS EPITERMAL SULFIDASI TINGGI DAN HUBUNGANNYA DENGAN MINERAL LEMPUNG HASIL ANALISA SPEKTRAL, DAERAH CIJULANG, KABUPATEN GARUT PROVINSI JAWA BARAT Sigit Heru Purwanto; Okki Verdiansyah
Jurnal Ilmiah MTG Vol 6, No 2 (2013)
Publisher : Jurusan Teknik Geologi Fakultas Teknologi Mineral 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.
Caldera of Godean, Sleman, Yogyakarta: A Volcanic Geomorphology Review Hill Gendoet Hartono; Adjat Sudradjat; Okki Verdiansyah
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 earth's surface.
Co-Authors Adjat Sudradjat Adjat Sudradjat Agung Harijoko Arifudin Idrus Heru Sigit Purwanto Hill Gendoet Hartono I Wayan Warmada Koichiro Watanabe, Koichiro Tun, Myo Min