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Potensi sumber daya geologi di daerah Cekungan Bandung dan sekitarnya Bronto, Sutikno; Hartono, Udi
Indonesian Journal on Geoscience Vol 1, No 1 (2006)
Publisher : Geological Agency

DOI:Â 10.17014/ijog.vol1no1.20062aGeologically, Bandung Basin and the surrounding area comprise volcanic rocks; therefore, originally the geological resources, such as energy, environmental geology and mineral were generated from past volcanic activities. Energy resources having been utilized or in the exploration stage are water energy (Saguling Electrical Hydro Power) and geothermal energy (Darajat, Kamojang, Wayang-Windu and Patuha Geothermal Fields). Potency of hydrocarbon energy is considered due to the presence of Tertiary sedimentary rocks under Bandung volcanic rocks. Environmental resources include water, soil, land, and natural panorama that mostly are already used for living, tourism, industry etc. Mineral resources cover metals and non metals. Mineral explorations, particularly for gold, have been conducted in the southern Bandung area. Recently, Center for Geological Survey itself has found a new mineral resource in the northern Bandung, i.e. Cupunagara Village, Cisalak Sub-Regency, Subang Regency - West Jawa. Â Â

The origin of Cihara granodiorite from South Banten Hartono, Udi; Syafri, Ildrem; Ardiansyah, Reza
Indonesian Journal on Geoscience Vol 3, No 2 (2008)
Publisher : Geological Agency

http://dx.doi.org/10.17014/ijog.vol3no2.20085Petrographical and geochemical characteristics of the Late Oligocene Cihara Granodiorite from South Banten are presented. Data show that the rock was originated from magma of a continental origin formed at a subduction zone environment. Fractional crystallization involving plagioclase, hornblende, pyroxene, and magnetite was the main process responsible for the geochemical variation of the rocks from the Cihara Granodiorite. There are two possibilities of parental magmas to the Cihara Granodiorite, i.e. the basaltic/ or andesitic magma of the Cikotok Formation or crustal melting magma from a subduction process. Some trace element data of the basaltic rocks from the Cikotok Formation are needed to support the first interpretation. Alternatively, heating of the Jawa lower crust by magma from either mantle or subducted slab melting caused the crustal melting to produce intermediate parent magma. Some degree of mixing between those two differ- ent magma sources during the fractionation may be involved in the petrogenesis. Â Â

Petrogenesis of The Sintang Intrusives and Its Implications for Mineralization In Northwest Kalimantan Hartono, Udi
Jurnal Geologi dan Sumberdaya Mineral Vol 16, No 4 (2006): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Arc magmatism is a direct response to tectonic and chemical processes operating in subduction zones. The Sintang Intrusives consist of microdiorite, microgranodiorite, granite/ microgranite, quartz diorite, dacite, andesite, and minor rhyolite and rhyodacite (dacite predominant). Depletion of Nb relative to K and La concentrations are characteristics of the rocks, implying the magma was generated in a subduction zone environment. However, different from magma of other “normal” arcs that were derived from mantle wedges, the magma of the Sintang Intrusives was generated from subducted oceanic crust melting. The result of a careful study of trace element data show that the rocks are of adakite type, characterized by high Sr/Y and Zr/Sm ratios, moderate to strong fractionation of heavy rare earth elements (HREE) and absence of Eu anomalies suggesting melt extraction from garnet-amphibolite sources. By considering the tectonic development in the South China Sea and northwest Kalimantan, it is believed that the magma was probably originated from the melting of previously subducted South China sea oceanic crust (dead slab or fossil subduction) beneath Kalimantan continent in the Late Oligocene - Early Miocene. A compressive tectonic regime in Middle Oligocene, and possibly until Late Oligocene, led to crustal shortening and thickening that facilitated entrapment of arc magma in the Kalimantan crust. The fluid released caused by amphibole breakdown and may have been expelled from older amphibolebearing plutons during compressional tectonics would be significantly important for mineralization. Keywords : Kalimantan, Sintang Intrusives, oceanic crustal melting, mineralization

CONTRIBUTION OF ARC MAGMATISM STUDIES IN EARLY STAGE MINERAL EXPLORATION Hartono, Udi
Jurnal Geologi dan Sumberdaya Mineral Vol 19, No 5 (2009): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Indonesia contains at least 15 volcano-plutonic arcs with total length of approximately 9,000 km. The eight arcs contain known mineral deposits, while the rest may have mineral deposit prospects. The discovery of new mineral resources depends on research into the genesis of ore deposits and improved methods of finding them. In order to reduce a high exploration cost, knowledge of arc magma genesis is very important in mineral exploration before further study on mineral deposit genesis. Review on a number literatures suggests there is no linear correlation between potential porphyry-Cu/ epithermal mineralization and a single petrological/ geological factor. Mineral deposit formation is a product of interplay of magmatism, tectonics, volcanism, and fluid processes. Keywords : arc magma genesis, ore deposits, exploration

Identification of Adakite from The Sintang Intrusives In West Kalimantan Hartono, Udi; Suyono, Suyono
Jurnal Geologi dan Sumberdaya Mineral Vol 16, No 3 (2006): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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The Sintang intrusives are widely exposed in West Kalimantan, and as reported by previous workers, consisting of high level intrusives of stocks, plugs, dykes and sills of microdiorite, microgranodiorite, granite/ microgranite, quartz diorite, dacite, andesite, and minor rhyolite and rhyodacite. However, a careful study of published geochemical data gives a result that the rocks are of adakitic type. Considering the tectonic development of the South China Sea and northwest Kalimantan, the adakite was probably originated from magma as a result of melting of the subducted South Cina sea oceanic crust beneath Kalimantan continent. The subduction started in the Late Oligocene when the crust was still young. Keywords : adakite, Sintang, intrusive, Late Oligocene

Posisi Stratigrafi dan Petrogenesis Intrusi Pendul, Perbukitan Jiwo, Bayat, Kabupaten Klaten, Jawa Tengah Surono, Surono; Hartono, Udi; Permanadewi, Sam
Jurnal Geologi dan Sumberdaya Mineral Vol 16, No 5 (2006): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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The Pendul Intrusion consists of andesite, diabas, diorite, and gabbro; that are widely distributed within the Jiwo Hills, south of Klaten, Central Jawa. K/Ar datings of 4 rock indicate that there are two magmatism episodes; Middle Eocene - Early Oligocene (39,82 - 30,04 Ma) and Middle Miocene (17,22 - 13,85 Ma). Trace element concentrations of the Pendul rocks characterize that the magma was originated from subduction environment as a result of mantle wedge melting. The rocks are characterized by low Nb relative to K and La contents. The rare earth element signatures indicate that the Pendul magmas might have come from defferent parent magmas. The Middle Eocene - Early Oligocene parent magmas posses lower rare earth element concentrations than those of the Middle Miocene ones. Keywords: Bayat, Pendul Intrusion, two magmatism episodes, stratigraphy

IDENTIFIKASI GUNUNG API PURBA DI DAERAH SAPAYA, SULAWESI SELATAN PADA DATA INDERAAN JAUH Sidarto, Sidarto; Hartono, Udi
Jurnal Geologi dan Sumberdaya Mineral Vol 19, No 6 (2009): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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In Tertiary, the South Arm of Sulawesi Island is a volcanic arc represented by Camba Formation having a relatively wide distribution. Integration of landsat and IFSAR images is able to visualize volcanic morphological features, lithology and volcanic structures that are used to identify ancient volcanoes in Sapaya area and surroundings. The result of geological interpretation on the images indicated there were two ancient volcanoes in this area, involving Sapaya and Bantoloe Volcanoes. The Middle Miocene - Pliocene Sapaya Volcano shows eroded cone feature, consisting of breccia volcanic (proximal facies), tuff (medial facies), and conglomerate (distal facies) units, and the vokanic structures are caldera, and radier intrusion basalts; while the Pliocene Bantoloe Volcano is identified by an eroded cone morphology, consisting of volcanic breccia of Bentoloe (proximal facies), lava Bantoloe (central testes), and diorite showing a deep seated intrusion (central facies). The Sapaya Volcano might be controlled by Tithyan type subduction showing a collision between micro continental which is part of Australian Continent and Eurasian Continent Plates. Keywords: South Arm Sulawesi, morphology, lithology, volcanic structure, ancient volcanoes, landsat and IFSAR Images

ORIGIN OF CRETACEOUS HIGH MAGNESIAN ANDESITES FROM SOUTHEAST KALIMANTAN Hartono, Udi; Isnu H. Sulistyawan, Raden
Jurnal Geologi dan Sumberdaya Mineral Vol 20, No 5 (2010): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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High magnesian andesites are found in the Cretaceous Haruyan volcanics in Southeast Kalimantan. The rocks have Mg# 67 – 69, but low concentrations of Ni (44 – 60 ppm), Cr (37 – 411 ppm) and, except two samples of 95UH23C and 96UH23, ratios of Sr/ Y are also low. Geochemical and tectonic studies show that the high magnesian andesites were originated from a subduction zone-type magma similar to that of the most “normal” Haruyan volcanics. Two possible origins of the Cretaceous high magnesian andesites are proposed. First, melting of the mantle wedge above the slab to produce a basaltic magma followed by crystal fractionation, especially olivine and pyroxene, during magma ascent to the surface resulted in a derivative magma with low Ni and Cr concentrations. A collision between the pre-Mesozoic Paternoster platform (microcontinent ?) and the Sundaland continent in the Upper Cretaceous-Lower Miocene might cause the magma ascent to pool immediately in the lower crust-upper mantle boundary. The impending magma then reacts with hot mantle peridotite to produce the high magnesian andesites. Secondly, the high magnesian andesite may resulted from a reaction between silicic magma and hot mantle peridotite. The collision may also cause lower crust melting resulted in granitic magma (? The Hajawa Granite), which then reacts with hot mantle peridotite to produce the adakite-type high magnesian magma, such as samples 95UH23C and 96UH23.Keywords : high magnesian andesites, Southeast Kalimantan, origin

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