The Jawara Field in Jember Regency is a location where it is indicated that there are precious metal deposits in the form of porphyry type Gold and Copper. In this study, the focus is more on the search for metal mineral deposits related to the elements of Gold (Au) and Copper (Cu), namely the metal mineral chalcopyrite (CuFeS2) as the main carrier minerals for Au, Cu, Ag, as impurities. The results of alteration products in the form of weathered minerals are also the focus of research. The analysis used to detect metallic element content and the presence of metallic and non-metallic minerals is by petrographic analysis, mineragraphy analysis, sediment grain analysis and geochemical analysis. Based on the results of the mineragraphy analysis, it was proven that the metal mineral chalcopyrite was found in the JAFA 6 BPS sample which is a carrier mineral for the metallic copper element and silver was also found in JAFA 2 ALT. In addition, the results of the sediment grain analysis also found metal mineral grains and metal elements, namely copper and iron elements in all JAFA samples. The results of petrographic analysis show that the weathered minerals in the form of kaolinite, alunite, and smectite are products of hydrothermal alteration activities. Based on these results, the research area is divided into 3 alteration zones, namely potassic, propylitic, and argillic alteration zones. The results of the geochemical analysis showed that the highest levels of copper were found in JAFA 5 as much as 13.9 ppm and the highest levels of iron in JAFA 6 were 390.8 ppm. From the results of the analysis, it can be concluded that it is true that there are metal mineral deposits and metal elements in the form of sediment grains and porphyry-type Au and Cu elements.
The Triassic aged sandstone from Kanikeh Formation, are spread across Seram, Kesui and Teor Island. The Kanikeh formation has been known as excellent source rock, however, reservoir characteristics of this formation are unknown. This paper aimed at the diagenetic influence on reservoir characteristics was investigated for the Carnian-Norian sandstone sequence in the Eastern Seram. This study comprises two methods which are petrographic analysis and Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS). The petrographic analysis shows the sandstones of the Carnian sequence in the Eastern Seram are lithic wacke, litharenite, arkose. SEM-EDS observations showed that the minerals belong to the silica group derived from the silica minerals, feldspar, clay, and mica minerals. The silica mineral is a quartz grain. The observed feldspar mineral is K-Feldspar in the form of granules. The most dominant clay minerals are smectite, illite, chlorite, kaolinite, halloysite. The observed mica group is muscovite. Diagenetic identified in these sandstones include compaction, cementation by calcite, quartz, clay minerals, iron oxides, dissolution, and alteration of unstable clastic grains, tectonically induced grain fracturing. Unstable clastic grains like feldspars suffered considerable alteration to clay minerals. Based on characteristics of the Diagenetic, the Carnian-Norian sandstones in the study area have a negligible reservoir characteristic.
The thickness of the liquefable layer can be the factor inducing liquefaction hazard, apart from seismicity. Several studies have been conducted to predict the possibility of the liquefable layer based on the filed sampling. However, a detailed investigation of the subsurface interpretation has not been defined, in particular the thickness estimation of the liquefable layer. This study is carried out in south Cilacap area where potential liquefaction is exists due to the earthquake history data and near surface condition. The aim of this study is to investigate the physical properties and thickness distribution using GGMplus gravity data and resistivity data. This research is conducted by spectrum analysis of gravity model and 2D resistivity model . This study’s main results is by performing the residual gravity anomaly with the associated SRTM/DEM data to define the subsurface physical distribution and structural orientation of the area. Residual gravity anomaly is also separated through the low pass filter in order to have robust interpretation. The residual anomaly indicates that the area has identical structural pattern with geological and SRTM map. The results show a pattern of high gravity index in the northeast area of the study having range of 70 – 115 MGal gravity index, associated with the volcanic breccia, and a low gravity profile with less than 65 in the southwest, associated with the alluvial and water table dominated distribution. The thickness of Alluvial is determined by resistivity model with H1 at a range of 3 meters and H2 at a range of 4 m. This research is included in the potential liquefaction category with the potential for a large earthquake.
Pulau Flores merupakan salah satu pulau di Indonesia yang kaya akan potensi bahan tambang termasuk emas. Secara umum, potensi pertambangan di Pulau Flores cukup besar yang meliputi berbagai jenis galian Golongan A, B dan C. Untuk jenis galian Golongan A (emas), baru merupakan perkiraan karena belum dilakukan penelitian secara seksama. Tujuan penelitian ini adalah mengutahui potensi endapan emas yang berasosiasi dengan struktur geologi. Metode yang digunakan berupa orientasi litologi dan struktur geologi, analisis XRF (<em>X - Ray Fluoroscence) </em>dari sampel RC <em>(Rock Chip)</em> dan SS <em>(Stream Sediment). </em>Hasil pemrosesan data geokimia batuan dari data XRF terdiri dari unsur utama, unsur jejak, dan unsur tanah jarang memperlihatkan prospek mineral logam yang relatif kecil dengan mineral Au yang berkisar antara <0,005-0.011 ppm, yang cukup jauh dari nilai <em>cut off grade</em> Au. Sedangkan dari hasil orientasi litologi dan struktur geologi diduga model mineralisasinya adalah tipe <em>epithermal vein system. </em>Sistem ini dikontrol oleh struktur patahan dan kekar.
Mineralisasi di daerah Bukit Randu dan sekitarnya terbentuk oleh struktur geologi dengan pola yang perlu diselidiki. Penelitian ini menggunakan data gores-garis sesar, kedudukan urat kuarsa serta kedudukan uratan kuarsa. Penelitian ini bertujuan untuk mengetahui pola struktur utama pembentuk zona mineralisasi. Penelitian ini berguna untuk menentukan model struktur geologi di daerah Bukit Randu. Metode penelitian dilakukan melalui pengumpulan data di lapangan dan analisis di laboratorium. Pengumpulan data lapangan mencakup pengukuran data gores-garis, pengukuran kedudukan urat (vein) kuarsa, pegukuran uratan (veinlet) kuarsa dan pengambilan conto urat (vein) kuarsa. Analisis laboratorium meliputi analisis stereografis terhadap terhadap gores-garis dan analisis diagram bunga terhadap data pengukuran urat (vein) dan uratan (Veinlet), dan mineragrafi asahan poles urat (vein). Mineralisasi urat dan uratan kuarsa di daerah Bukit Randu dikontrol oleh sesar mendatar kanan berarah baratlaut-tenggara dan sesar normal utara-selatan. Zona mineralisasi ini merupakan zona transtensi berarah utara-selatan akibat en-enchelon right stepping sesar mendatar kanan. Mineral logam mulia hadir pada urat-urat berarah utara-selatan searah dengan arah sesar-sesar normal.
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