Garuda - Garba Rujukan Digital

Petrography and Mineral Chemistry of Magmatic and Hydrothermal Biotite in Porphyry Copper-Gold Deposits: A Tool for Understanding Mineralizing Fluid Compositional Changes During Alteration Processes Idrus, Arifudin
Indonesian Journal on Geoscience Vol 5, No 1 (2018)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.5.1.47-64

DOI: 10.17014/ijog.5.1.47-64This study aims to understand the petrography and chemistry of both magmatic and hydrothermal biotites in porphyry copper-gold deposits, and to evaluate the fluid compositional changes during alteration processes. A total of 206 biotite grains from selected rock samples taken from the Batu Hijau porphyry Cu-Au deposit was analyzed. Detailed petrography and biotite chemistry analysis were performed on thin sections and polished thin sections, respectively, representing various rocks and alteration types. A JEOL JXA-8900R electron microprobe analyzer (EMPA) was used for the chemistry analysis. The biotite is texturally divided into magmatic and hydrothermal types. Ti, Fe, and F contents can be used to distinguish the two biotite types chemically. Some oxide and halogen contents of biotite from various rocks and alteration types demonstrate a systematic variation in chemical composition. Biotite halogen chemistry shows a systematic increase in log (XCl/XOH) and decrease in log (XF/XOH) values from biotite (potassic) through chlorite-sericite (intermediate argillic) to actinolite (inner propylitic) zones. The y-intercepts on the log (XCl/XOH) vs. XMg and log (XF/XOH) vs. XFe plotted for biotite from potassic and intermediate argillic zones are similar or slightly different. In contrast, the y-intercepts on the log (XCl/XOH) vs. XMg and log (XF/XOH) vs. XFe plotted for biotite from inner propylitic zone display different values in comparison to the two alteration zones. Halogen (F,Cl) fugacity ratios in biotite show a similar pattern: in the potassic and intermediate argillic zones they show little variation, whereas in the inner propylitic zone they are distinctly different. These features suggest the hydrothermal fluid composition remained fairly constant in the inner part of the deposit during the potassic and intermediate argillic alteration events, but changed significantly towards the outer part affected by inner propylitic alteration. High halogen content, particularly Cl, in hydrothermal biotite may portray that copper and gold were transported in mineralizing fluids in the form of chloride complexes CuCl2- and AuCl2-, respectively.

Geochemical Characteristics of Limestone of Wonosari-Punung Formation, Gunungkidul Regency, Yogyakarta, Indonesia Atmoko, Didik Dwi; Titisari, Anastasia Dewi; Idrus, Arifudin
Indonesian Journal on Geoscience Vol 5, No 2 (2018)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.5.2.179-197

DOI: 10.17014/ijog.5.2.179-197A geochemical study was carried out to determine the geochemical characteristics of limestone in Wonosari-Punung Formation, and to suggest its depositional conditions and the source of rare earth elements. The study was conducted at Ponjong Area, Gunungkidul Regency, Daerah Istimewa Yogyakarta, Indonesia. White limestone which contains more abundant calcite is characterized by the highest CaO concentration. Red limestone which is associated with impure minerals such as siderite, rodochrosite, hematite, and titanite is typified by depleted CaO but higher SiO2, Fe2O3, MnO, and TiO2 concentrations. Grey limestone characterized by depleted CaO and higher MnO contents is considered to be influenced by the presence of impure minerals of manganite (Mn2O3.H2O) and/or pyrolusite (MnO2). Depletion of Sr concentration in the coloured limestone indicates that the diagenetic process increases from the white limestone to the coloured limestone. The process possibly occurred post-deposition of the limestones. The limestones show positive Mn* values (2.46 - 2.95) and authigenic U values (0.89 - 3.38) that suggest an oxidative environment. The Ce/Ce* values (0.57 - 0.80), Eu/Eu* values (1.04 - 1.88), high Y/Ho ratio, and low LaN/YbN ratio are indications that the rare earth elements in the limestones were derived from terrigenous materials. The positive Eu anomaly and enrichment of Cr and Mn of the limestones are indications of hydrothermal fluid activity taking place in the studied area. Based on the geochemical characteristics of the Punung-Wonosari limestones, the depositional environment and the source of rare earth elements of the limestones were therefore influenced by a combination of hydrothermal fluid activity with small amount of terrigenous material input and post depositional diagenetic process.

Edukasi Teknik Penambangan Emas yang Ramah Lingkungan pada Tambang Rakyat Skala Kecil di Daerah Soripesa, Kecamatan Wawo, Kabupaten Bima, Nusa Tenggara Barat Idrus, Arifudin
International Journal of Community Service Learning Vol 5, No 1 (2021): February 2021
Publisher : Universitas Pendidikan Ganesha

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23887/ijcsl.v5i1.30557

Tambang emas rakyat merupakan kegiatan penambangan emas yang dilakukan oleh masyarakat secara tradisional dalam skala kecil. Tambang rakyat ini umumnya tidak memiliki ijin pertambangan rakyat (IPR) seperti diisyaratkan oleh UU No. 3 Tahun 2020. Dalam prakteknya, penambangan tersebut sering dilakukan tidak mematuhi kaidah penambangan yang baik (good mining practices) seperti yang terjadi di daerah Soripesa, Kabupaten Bima, Provinsi Nusa Tenggara Barat. Tulisan ini bertujuan menguraikan edukasi teknik penambangan emas tradisional terhadap endapan emas tipe urat epitermal sulfidasi rendah yang ramah lingkungan dan mempraktekan kaidah good mining practices tersebut. Kegiatan dilakukan dengan metoda ceramah dan diskusi interaksi baik di kelas maupun di lokasi tambang Soripesa tersebut. Ada 5 aspek yang ditekankan dalam kegiatan ini yaitu (a) teknik penambangan terhadap keselamatan kerja para penambang rakyat, (b) teknik pembuatan jalur terowongan, (c) teknik penggalian batuan yang mengandung emas, (d) teknik pengangkutan dari dalam ke luar area tambang, dan (e) pengolahan emas yang aman.

SOSIALISASI PENGENDALIAN KERUSAKAN LAHAN AKIBAT PERTAMBANGAN RAKYAT DI KABUPATEN BANTUL, PROVINSI DAERAH ISTIMEWA YOGYAKARTA Idrus, Arifudin; Rahmah, Yuyun Prihatining
Jurnal ABDI: Media Pengabdian Kepada Masyarakat Vol 7, No 1 (2021)
Publisher : Universitas Negeri Surabaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26740/ja.v7n1.p12-17

Kerusakan lingkungan akibat kegiatan pertambangan rakyat di Indonesia, termasuk di Kabupaten Bantul, Provinsi Daerah Istimewa Yogyakarta sudah cukup mengkhawatirkan. Kerusakan lahan tersebut terutama diakibatkan oleh penambangan tanah liat pada sawah atau tegal produktif untuk pemenuhan bahan baku batu bata dan juga penambangan sirtu pada badan atau teras/bantaran sungai. Berlatarbelakang hal tersebut, Dinas Lingkungan Hidup (DLH) Kabupaten Bantul bekerjasama dengan Pusat Studi Lingkungan Hidup Universitas Gadjah Mada (PSLH UGM) menyelenggarakan Kegiatan Sosialisasi Pengendalian Kerusakan Lingkungan Hidup akibat kegiatan pertambangan rakyat yang dilakukan di seluruh kecamatan di Kabupaten Bantul. Metoda sosialisasi yaitu melalui Kegiatan Pendidikan Masyarakat berupa memberikan penyuluhan yang bertujuan meningkatkan pengetahuan, pemahaman serta kesadaran masyarakat terkait pentingnya pengendalian kerusakan lingkungan hidup untuk kehidupan yang lebih baik. Hasil kegiatan sosialisasi tersebut adalah pemahaman konsep-konsep penambangan yang baik dan benar (good mining practices), mulai dari tahap penyiapan lahan (pre-mining), tahap operasi penambangan dan tahap pasca penambangan. Pada tahap penyiapan lahan penambangan tanah liat misalnya harus mengamankan tanah pucuk (top soil), pada tahap menambangan perlu dilakukan dengan mempertimbangkan kesehatan dan keselamatan kerja (K3), meminimalisasi timbulnya berbagai dampak negatif terhadap aspek geofisik kimia biologi kesmas sosekbud yang berujung pada timbulnya konflik sosial, dan pada tahap pasca penambangan, lahan bekas tambang harus dilakukan penataan lahan (landforming), reklamasi dan revegetasi, serta direncanakan pemanfaatan lahan pasca tambangnya.

Komatiitic Lamprophyre in West Sulawesi: First Evidence for >1350Â°C and 3.5 - 3.8 GPa Mantle Melts Godang, Shaban; Fadlin, Fadlin; Priadi, Bambang; Idrus, Arifudin; Sukadana, I Gde
Indonesian Journal on Geoscience Vol 8, No 1 (2021)
Publisher : Geological Agency

DOI: 10.17014/ijog.8.1.39-58The presence of lamprophyric lavas of Late Cenozoic in Talaya Volcanic Formation at the boundary between the subregencies of Mamuju and Tabulahan (Western Sulawesi) associated with the mantle enrichment rocks of the Adang Volcanics is the subject of this study. Petrologically, lamprophyre is composed of orthopyroxene (enstatite), clinopyroxene (augite), biotite, leucite, amphibole, magnetite, and autometasomatism of chlorite in grain minerals and groundmass. The lamprophyre is classified into monchiquite shoshonitic lamprophyre, and it has a komatiitic composition with the ratio of MgO/Al2O3 > 0.7906 (in wt %). The komatiitic monchiquite lamprophyre is characterized by high MgO (10.02 - 12.67 %), relatively low alumina (Al2O3= 10.98 - 11.70 %), SiO2= 46.43 - 47.8 %, TiO2 (0.84 - 1.00 %), FeOt (7.75 - 7.88 %), and relatively high content of alkaline (Na2O: 2.20 - 2.59 %; K2O: 1.58 - 2.45 %; Total alkali: 4.00 - 4.89 %, and CaO (9.29 - 10.71 %). The geochemical trace element plots using various diagrams suggests the geotectonic setting of the lamprophyric rock was formed in suprasubduction alkaline continental-arc, and the proposed source of magmatism comes from the suprasubduction activities from the east. The protolith of magma was originated from partial melting of depleted MORB mantle (DMM), composed of pyroxene-peridotite (garnet-lherzolite). The partial melting conditions are suggested to occur at high pressure (3.5 - 3.8 GPa) and the depth of ~120 km with melting temperature of >1350Â°C, and the magma is dominantly controlled by olivine fractional crystallization.

Geology, Vein Textures, and Fluid Inclusions of the Cibeber Low-Intermediate Sulfidation Epithermal Au-Ag Orefield, Western Java Dana, Cendi D. P.; Idrus, Arifudin; Setiawan, Iwan; Handayani, Esti; Yurniadi, Feddy; Meak, Ignas A.; Lai, Chun-Kit
Indonesian Journal on Geoscience Vol 8, No 2 (2021)
Publisher : Geological Agency

DOI:10.17014/ijog.8.2.157-175This paper describes the results of surficial geological and alteration mapping combined with several laboratory analyses, including petrography, ore microscopy, ore geochemistry, and fluid inclusion studies, aimed at establishing the nature of mineralization and alteration in the Cibeber area, West Java, Indonesia, and developing a genetic model. The area forms part of the Bayah Dome Complex, which hosts several gold-silver deposits. It is underlain by andesitic lava, tuff breccia, and subordinate sandstone. Its structural framework consists of joints, normal faults, NE-SW dextral strike slip faults, and NW-SE strike-slip faults. Hydrothermal alteration can be divided into four types, viz. silicification, clay-silica, argillic, and propylitic. Mineralization is mostly hosted in quartz veins showing a variety of textures, including massive, colloform-crustiform, breccia, lattice bladed, comb, and saccharoidal. Ore minerals consist of native gold and silver, pyrite, chalcopyrite, sphalerite, galena, tennantite-tetrahedrite, covellite, malachite, hematite, and goethite, while the gangue minerals quartz, illite, epidote, and calcite. Four stages of mineralization/veining are recognized: early, middle (the main ore forming stage), late, and supergene. The highest obtained metal grades are 8.17 ppm Au, 113.6 ppm Ag, 1.23% Cu, 1.28% Pb, and 1.2% Zn. Fluid inclusions from mineralized veins yielded temperatures of 222 - 280Â°C and salinities of 0.36 - 1.31 wt.% NaCl eq. The hydrothermal fluids are interpreted to have been largely of meteoric origin with the mineralization having formed at a depth of about 258 - 270 m below paleosurface. Both low-sulphidation and intermediate-sulphidation styles of mineralization are present.

Geochemistry Study of Cross-castic Magma Alkalinity Evolution Godang, Shaban; Priadi, Bambang; Fadlin, Fadlin; Leeuwen, Theo Van; Idrus, Arifudin
Indonesian Journal on Geoscience Vol 8, No 2 (2021)
Publisher : Geological Agency

DOI:10.17014/ijog.8.2.177-196The discrimination of magmatic alkalinity is a classic study that has never stopped for the past ninety years. Various methodologies have been developed since Shandâ€™s classification using the method of alumina saturation to approach silica saturation and the methodology without involving alumina and silica such as K2O vs. Na2O and others, while the aim is to find out the evolution of alkalinity during the magmatic differentiation. The classical magmatic alkalinity evolution has been known as a castic magma alkalinity evolution, where the initial magma in the form of magma-X(a) will evolve along the stages of differentiation and remain a derivative of the initial magma {magmaX(a)}. The same philosophy is also explained in the ternary AFM diagram. Is the magmatic differentiation, followed by fractional crystallization, always an evolution of alkalinity based on caste? This question often raises current debates. This study takes the example of cogenetic volcanic and albitites. The application of the cogenetic volcanic using the selected diagram, which is â€˜Three in one an overlaid diagramâ€™. The output of the diagram presents the differentiation of magma which based on the evolution of Mg-series and Fe-series in a discontinuous branch of Bowen 1922 that can take place the castic and cross-castic, e.g. (a) from Mg-series to Mg-series {castic}, (b) from Mg-series to Feseries {cross-castic}, (c) from high-Mg tholeiitic basalt to calc-alkaline series {cross-castic}, (d) from Fe-series to Fe-series {castic}. While the evolution of magmatic alkalinity based on the continuous branch and refer to Trapezoid model generally occurring a cross-castic, e.g. (A) from sodic calc-alkaline to sodic alkaline-calcic, (B) from sodic calc-alkaline to shoshonitic alkaline-calcic, (C) from sodic calc-alkaline to potassic calc-alkaline, (D) from potassic calc-alkaline to shoshonitic alkaline-calcic, (E) sodic alkaline-calcic to sodic alkaline/peralkaline, (F) shoshonitic alkaline-calcic to potassic/ultrapotassic alkaline-calcic (cross-castic in subalkaline), (G) shoshonitic/potassic alkalinecalcic to shoshonitic/potassic alkaline/peralkaline. In this study, Fossa delle Felci volcanics (Italy) shows the evolution of magma from Mg-series to Mg-series, but the evolution of alkalinity of magma reveals the cross-caste (from sodic calc-alkaline to shoshonitic alkaline-calcic). Salak volcanics (Western Jawa) shows the evolution of magma from the Mg-series to Fe-series (cross-castic), and also the cross-castic in the evolution of alkalinity from sodic calc-alkaline to alkaline-calcic. Gothara albitites (India) clearly reveal the sodic-rich alkaline, which the magma generates from the evolution of sodic alkaline-calcic to sodic alkaline without the presence of potassic.

Komatiitic Lamprophyre in West Sulawesi: First Evidence for >1350Â°C and 3.5 - 3.8 GPa Mantle Melts Godang, Shaban; Fadlin, Fadlin; Priadi, Bambang; Idrus, Arifudin; Sukadana, I Gde
Indonesian Journal on Geoscience Vol 8, No 1 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.1.39-58

DOI: 10.17014/ijog.8.1.39-58The presence of lamprophyric lavas of Late Cenozoic in Talaya Volcanic Formation at the boundary between the subregencies of Mamuju and Tabulahan (Western Sulawesi) associated with the mantle enrichment rocks of the Adang Volcanics is the subject of this study. Petrologically, lamprophyre is composed of orthopyroxene (enstatite), clinopyroxene (augite), biotite, leucite, amphibole, magnetite, and autometasomatism of chlorite in grain minerals and groundmass. The lamprophyre is classified into monchiquite shoshonitic lamprophyre, and it has a komatiitic composition with the ratio of MgO/Al2O3 > 0.7906 (in wt %). The komatiitic monchiquite lamprophyre is characterized by high MgO (10.02 - 12.67 %), relatively low alumina (Al2O3= 10.98 - 11.70 %), SiO2= 46.43 - 47.8 %, TiO2 (0.84 - 1.00 %), FeOt (7.75 - 7.88 %), and relatively high content of alkaline (Na2O: 2.20 - 2.59 %; K2O: 1.58 - 2.45 %; Total alkali: 4.00 - 4.89 %, and CaO (9.29 - 10.71 %). The geochemical trace element plots using various diagrams suggests the geotectonic setting of the lamprophyric rock was formed in suprasubduction alkaline continental-arc, and the proposed source of magmatism comes from the suprasubduction activities from the east. The protolith of magma was originated from partial melting of depleted MORB mantle (DMM), composed of pyroxene-peridotite (garnet-lherzolite). The partial melting conditions are suggested to occur at high pressure (3.5 - 3.8 GPa) and the depth of ~120 km with melting temperature of >1350Â°C, and the magma is dominantly controlled by olivine fractional crystallization.

Geology, Vein Textures, and Fluid Inclusions of the Cibeber Low-Intermediate Sulfidation Epithermal Au-Ag Orefield, Western Java Dana, Cendi D. P.; Idrus, Arifudin; Setiawan, Iwan; Handayani, Esti; Yurniadi, Feddy; Meak, Ignas A.; Lai, Chun-Kit
Indonesian Journal on Geoscience Vol 8, No 2 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.2.157-175

DOI:10.17014/ijog.8.2.157-175This paper describes the results of surficial geological and alteration mapping combined with several laboratory analyses, including petrography, ore microscopy, ore geochemistry, and fluid inclusion studies, aimed at establishing the nature of mineralization and alteration in the Cibeber area, West Java, Indonesia, and developing a genetic model. The area forms part of the Bayah Dome Complex, which hosts several gold-silver deposits. It is underlain by andesitic lava, tuff breccia, and subordinate sandstone. Its structural framework consists of joints, normal faults, NE-SW dextral strike slip faults, and NW-SE strike-slip faults. Hydrothermal alteration can be divided into four types, viz. silicification, clay-silica, argillic, and propylitic. Mineralization is mostly hosted in quartz veins showing a variety of textures, including massive, colloform-crustiform, breccia, lattice bladed, comb, and saccharoidal. Ore minerals consist of native gold and silver, pyrite, chalcopyrite, sphalerite, galena, tennantite-tetrahedrite, covellite, malachite, hematite, and goethite, while the gangue minerals quartz, illite, epidote, and calcite. Four stages of mineralization/veining are recognized: early, middle (the main ore forming stage), late, and supergene. The highest obtained metal grades are 8.17 ppm Au, 113.6 ppm Ag, 1.23% Cu, 1.28% Pb, and 1.2% Zn. Fluid inclusions from mineralized veins yielded temperatures of 222 - 280Â°C and salinities of 0.36 - 1.31 wt.% NaCl eq. The hydrothermal fluids are interpreted to have been largely of meteoric origin with the mineralization having formed at a depth of about 258 - 270 m below paleosurface. Both low-sulphidation and intermediate-sulphidation styles of mineralization are present.

Geochemistry Study of Cross-castic Magma Alkalinity Evolution Godang, Shaban; Priadi, Bambang; Fadlin, Fadlin; Leeuwen, Theo Van; Idrus, Arifudin
Indonesian Journal on Geoscience Vol 8, No 2 (2021)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17014/ijog.8.2.177-196

DOI:10.17014/ijog.8.2.177-196The discrimination of magmatic alkalinity is a classic study that has never stopped for the past ninety years. Various methodologies have been developed since Shandâ€™s classification using the method of alumina saturation to approach silica saturation and the methodology without involving alumina and silica such as K2O vs. Na2O and others, while the aim is to find out the evolution of alkalinity during the magmatic differentiation. The classical magmatic alkalinity evolution has been known as a castic magma alkalinity evolution, where the initial magma in the form of magma-X(a) will evolve along the stages of differentiation and remain a derivative of the initial magma {magmaX(a)}. The same philosophy is also explained in the ternary AFM diagram. Is the magmatic differentiation, followed by fractional crystallization, always an evolution of alkalinity based on caste? This question often raises current debates. This study takes the example of cogenetic volcanic and albitites. The application of the cogenetic volcanic using the selected diagram, which is â€˜Three in one an overlaid diagramâ€™. The output of the diagram presents the differentiation of magma which based on the evolution of Mg-series and Fe-series in a discontinuous branch of Bowen 1922 that can take place the castic and cross-castic, e.g. (a) from Mg-series to Mg-series {castic}, (b) from Mg-series to Feseries {cross-castic}, (c) from high-Mg tholeiitic basalt to calc-alkaline series {cross-castic}, (d) from Fe-series to Fe-series {castic}. While the evolution of magmatic alkalinity based on the continuous branch and refer to Trapezoid model generally occurring a cross-castic, e.g. (A) from sodic calc-alkaline to sodic alkaline-calcic, (B) from sodic calc-alkaline to shoshonitic alkaline-calcic, (C) from sodic calc-alkaline to potassic calc-alkaline, (D) from potassic calc-alkaline to shoshonitic alkaline-calcic, (E) sodic alkaline-calcic to sodic alkaline/peralkaline, (F) shoshonitic alkaline-calcic to potassic/ultrapotassic alkaline-calcic (cross-castic in subalkaline), (G) shoshonitic/potassic alkalinecalcic to shoshonitic/potassic alkaline/peralkaline. In this study, Fossa delle Felci volcanics (Italy) shows the evolution of magma from Mg-series to Mg-series, but the evolution of alkalinity of magma reveals the cross-caste (from sodic calc-alkaline to shoshonitic alkaline-calcic). Salak volcanics (Western Jawa) shows the evolution of magma from the Mg-series to Fe-series (cross-castic), and also the cross-castic in the evolution of alkalinity from sodic calc-alkaline to alkaline-calcic. Gothara albitites (India) clearly reveal the sodic-rich alkaline, which the magma generates from the evolution of sodic alkaline-calcic to sodic alkaline without the presence of potassic.

Title

Found 151 Documents
Search

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract

Title Search

Found 151 Documents Search

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract

Abstract

Title

Found 151 Documents
Search