sam permanadewi, sam
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CEBAKAN NIKEL LATERIT DI PULAU GAG, KABUPATEN RAJA AMPAT, PROVINSI PAPUA BARAT Permanadewi, Sam
Buletin Sumber Daya Geologi Vol 12, No 1 (2017): Buletin Sumber Daya Geologi
Publisher : Buletin Sumber Daya Geologi

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Abstract

Pulau Gag, yang terletak terpencil di deretan kepulauan Raja Ampat, merupakan pulau yang memendam sumberdaya mineral yang berlimpah.  Sumber daya tersebut  berupa cebakan bijih nikel laterit (Ni, Co, Fe) yang menempati ± 2/3 dari pulau tersebut. Secara geologi, 2/3 bagian Pulau Gag ditempati oleh komplek ofiolit yang terdiri atas batuan ultramafik (serpentinit, harzburgit, dan piroksenit) sedangkan sisanya ditempati oleh batuan gunungapi. Komplek ofiolit di Pulau Gag ini diduga sebagai kerak samudera yang secara tektonik tersungkup di tepi benua dan busur kepulauan akibat adanya pergerakan Benua Australia kearah utara. Laterit nikel terbentuk akibat adanya proses pelapukan kimia yang terjadi  pada batuan ofiolit yang telah mengandung nikel. Bijih nikel sekunder berupa garnierite diendapkan kembali dalam horizon tanah penutup, limonit dan saprolit setelah mengalami pengayaan oleh proses pelapukan. Berdasarkan hasil analisa contoh, menunjukkan bahwa kandungan Ni dalam laterit adalah 1,2% Ni, >30% Fe (lapisan limonit); 1,2% Ni, <15% Fe (lapisan saprolit).   
Mineralogi dan Geokimia Tuf Berumur Tersier dan Kuarter di Daerah Cibadak, Sukabumi, Jawa Barat Permanadewi, Sam; Maryanto, Sigit; Subandrio, Joko
Jurnal Geologi dan Sumberdaya Mineral Vol 18, No 4 (2017): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

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Abstract

Fine-grained pyroclastic rocks  found in the Cibadak area, Sukabumi divided into two groups, namely Tertiary tuff composing of Jampang Formation and Quarternary tuff as the result of  young volcanic eruptions. The relationship between mineralogy and geochemistry of those tuffs are discussed in this paper. Laboratory testing was conducted on fifty rock samples taken from the field. A kind of mineralogy composing the rock can be identified by the XRD (X-Ray Diffraction) mineralogy test, while the major oxide of the rock can be calculated with the XRF (X-Ray Fluorescence) geochemistry test. The XRD mineralogy test shows  two secondary mineral that becomes the differentiation between the two tuffs are zeolites and clay minerals. The zeolites present at most of the Tertiary tuffs as a result of the rock alteration which involves an increasing in formation temperature and pressure. Clay minerals are mostly present at the Quarternary tuffs as a result of rock wheathering on the surface. The zeolite and clay minerals are associated with almost all chemical oxides of the rocks. The chemical oxides including SiO2, Al2O3, Fe2O3, MgO, K2O, TiO, and MnO. The XRF rock-chemically characters show there are no differences of the chemical oxide components on both of these pyroclastic rock groups. Keywords: mineralogy, geochemistry, tuff, Tertiary, Quarternary.
Karakteristik Minyak Bumi di Blok Bula dan Blok Oseil, Pulau Seram, Maluku Wahyudiono, Joko; Adlan, Ryandi; Permanadewi, Sam; Gibran, Akhmad Khahlil
Jurnal Geologi dan Sumberdaya Mineral Vol 19, No 4 (2018): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

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Abstract

Oil that produced in a petroleum system must have specific characteristics depend on the source rocks. These characteristics are able to be understood by analyses of organic geochemistry. Gas Chromatography - Mass Spectrometry (GC-MS) is a very accurate tool for determining the characteristics of oil and gas. This research shows the evidence that oil samples taken from Bula Block and Oseil Block, Seram Island have the same source.Keywords: petroleum system, organic geochemistry, Bula, Oseil, Seram Island
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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Abstract

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
INDIKASI BATUAN ADAKITIK DI PACITAN, JAWA TIMUR Baharuddin, Baharuddin; permanadewi, sam
Jurnal Geologi dan Sumberdaya Mineral Vol 22, No 4 (2012): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Abstract

Volcanic and intrusive rocks from Pacitan area cropping out as lavas, dykes and stockworks, consist of basaltic - andesite to rhyolite in composition. Based on petrologic and geochemical analyses, the volcanic rocks consist of SiO2 55.79 – 72.19%, TiO2 0.07- 0.54%, Al2O3 15.43 – 19.46%, MgO 1.38 – 5.09. While trace element contents, especially Sr 78.25 – 845 ppm, Y 36.31 – 11.15 ppm, Yb 1.05 – 2.58 ppm dan Sr/Y 4.41 – 41.40 ppm. Discriminant diagram of SiO2 vs K2O Pacitan volcanic rocks are including the rocks into tholeiitic low – K series. Therefore in trace element spider diagrams show that the rocks are an island arc affinity except one sample relating with OIB. Several samples of Pacitan volcanics are adakitic like which have high Sr and low Y, Yb content.Key words: petrology, geochemistry, adakitic rocks, Pacitan
COOLING OF GRANITIC ROCKS IN THE PALU REGION, MIDDLE SULAWESI: ZIRCON AND APATITE FISSION TRACK CONSTRAINTS Permanadewi, Sam; Baharuddin, Baharuddin
Jurnal Geologi dan Sumberdaya Mineral Vol 22, No 3 (2012): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Abstract

Zircon and apatite fission track analysis has been employed to constrain a cooling episode of the Oligocene-Miocene granitic sequences in the Palu region, Middle Sulawesi. A fission track dating from five outcrops resulted in zircon ages ranging between 9.5±0.5 Ma and 29.5±2.1 Ma. These ages may represent the onset of crystallisation during magmatic emplacement. This interpretation is consistent with the corresponding K/Ar ages ranging between 8.6 Ma for biotite and 31 Ma for feldspar. All but one sample show apatite fission track ages younger than zircon ages. The apatite fission track ages range between 6.2±1.3 Ma and 29.3±2.5 Ma. Importantly, the oldest zircon and apatite crystals separated from the rock sample derived from pluton in the southern section suggest that the host sequence has not undergone a further cooling event since crystallisation in the Oligocene. However, the remaining apatite fission track ages from rock successions in the northern sector of the studied region reveal an episode of post-crystallisation rapid cooling of the Oligocene granitic pluton, possibly due to local-scale uplift in response to overthrust in the late Miocene.Keywords: cooling, fission track, granitic pluton, Sulawesi
Pentarikhan Jejak Belah Zirkon dan Implikasinya Terhadap Genesa Batuan Granitik Di Daerah Kayutanam, Padang Panjang, Sumatera Barat Permanadewi, Sam
Jurnal Geologi dan Sumberdaya Mineral Vol 19, No 2 (2018): Jurnal Geologi dan Sumberdaya Mineral
Publisher : Pusat Survei Geologi

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Abstract

The outcrop of granitic rocks at Kayutanam area, Padang Panjang, West Sumatera is known occured during Neogene. The fission track dating method can determine the absolute age of the granitic rock in this area and the intrusive period. Fission track analysis results the age of these granitic rocks is generated from 5.1 ± 0.5 to 19.9 ± 1.5 mys. Considering these dating result comprehend with petrographic analysis and the location of the granitic rocks it is suggested that the granitic intrusion occurred in three periods. The first granitic intrusion period took place in the Upper part of Early Miocene (19.9 mys). The second granitic intrusion period occured during the Lower - Upper part of Middle Miocene (15.0-11.2 mys). While the latest granitic intrusion is determined generated on the Lower part of Late Miocene- Early Pliocene (10.8-5.1 mys).Keyword : Fission track dating, petrography, granitic rocks, West Sumatera, Miocene. 
KECEPATAN PERGERAKAN MAGMA DASIT KE PERMUKAAN DI DAERAH PURWOREJO DAN SEKITARNYA, JAWA TENGAH Berdasarkan Analisis Penarikhan Jejak Belah Permanadewi, Sam; Saefudin, I.; A.Siregar, D.
Jurnal Geologi dan Sumberdaya Mineral Vol 18, No 4 (2008): Jurnal Sumber Daya Geologi
Publisher : Pusat Survei Geologi

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Abstract

Zircon fission track dating using zirkon of four dacite samples from Purworejo, yielded age of 12,6 ± 1,5 to 15,9 ± 1,0 m.a. One cooling phase of the dacite body at Purworejo area indicates an uplift velocity of 0.02 - 0.06 mm / year. Keywords : fission tracks, zircon, uplift, Purworejo