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All Journal Journal of Geoscience, Engineering, Environment, and Technology Bulletin of Geology
Basuki, Nurcahyo Indro
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Earth & Planetary Sciences Energy Engineering Environmental Science Physics

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Metamorphic Complex Deformation in North Bangka Island Based on Macrostructures and Microstructures Evidences Hendrawan, Rezki; Draniswari, Windi Anarta; Wahyuni, Fitri Indah; Sapiie, Benjamin; Basuki, Nurcahyo Indro
Journal of Geoscience, Engineering, Environment, and Technology Vol. 9 No. 2 (2024): JGEET Vol 09 No 02 : June (2024)
Publisher : UIR PRESS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25299/jgeet.2024.9.2.13379

Abstract

The northern Bangka Island is composed of Pemali metamorphic complex which is indicated by the collision between Indochina and Sibumasu blocks. These features are interesting to observe because the metamorphic rocks could be recorded in some geological structures at different times. The study began by conducting field observation on Pemali Metamorphic Complex as objects. Field observation aims to collect lithological data, structural data, and oriented rock samples. The results of field pitching were processed to determine macrostructures, microstructures, and mineral distribution. The data was analyzed based on kinematic, descriptive, and deformation mechanisms to determine the deformation patterns that occurred in the study area. Field and oriented thin section data show structures and occurred in different deformation conditions. The analysis based on macrostructures and microstructures showed that the northern part of Bangka Island experienced three different deformation phases. Deformation begins with the formation of folds that are associated with collisions between Sibumasu-Indochina, followed by a second deformation that forms a fold with different verging. Both deformations are formed in the ductile zone and the brittle-ductile transition zone. The third deformation occurs when rocks have been lifted to the surface by the presence of faults, joints, and veins. The sequence of the deformation model is similar to the deformation experienced in the Bentong-Raub suture zone formed in the shear zone.
THE GEOCHEMICAL SIGNATURE OF THE ELANG PORPHYRY CU-AU DEPOSIT SUMBAWA, NUSA TENGGARA BARAT, INDONESIA Bastian, Arief; Basuki, Nurcahyo Indro; R, Yan Rizal
Bulletin of Geology Vol 8 No 2 (2024): Bulletin of Geology Vol. 8 no. 2
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2024.8.2.1

Abstract

The demand for copper and gold has increased significantly, but finding new exposed porphyry deposits has become more challenging. Elang porphyry Cu-Au deposit is one of few world class deposits, discovered in the last 30 years, located in Sumbawa Island, Indonesia. This study aimsto understand the correlation between geochemical elements in porphyry mineralization using soil and core sample data. The research methods include collecting soil and core samples, conducting geochemical analysis, and processing and interpreting the data. The research results show that The Cu-Au mineralization at Elang is mainly within and around multiple tonalite intrusions where intense of early quartz-sulphide and potassic alteration dominates, constrained by the extent of advanced argillic alteration.Tonalite is distinguished based on cross-cutting relationships, texture, and the crystal shape of quartz eye that is present as a phenocryst. The crystalline shapes are closely aligned with the copper and gold mineralization. Variations in the styles of geology and mineralization contribute to differing geochemical expressions of the porphyry deposits. Geochemical data, especially from soil samples, emerges as a valuable method for identifying signatures within porphyry mineralization deposits. The copper,zinc, lead, and molybdenum clearly point to the central of the porphyry system, while broad zones of high gold anomalies are associated with epithermal high-sulfidation systems. Analysis of core samples reveals that the Cu/Au ratio exhibits a distinct vertical zonation pattern throughout the porphyry body. Understanding the geology and geochemical characteristics of the Elang deposit provides valuable insights for exploration strategies aimed at discovering similar deposits elsewhere. Key words: porphyry Cu-Au, geochemical soil anomaly, Elang deposits
LATERITISASI PADA KOMPLEKS MELANGE AREA WAILUKUM, KABUPATEN HALMAHERA TIMUR Ramadhan, Aditya Rizki; Basuki, Nurcahyo Indro; Priadi, Bambang; Sutopo, Bronto; Bari, Abdul
Bulletin of Geology Vol 4 No 1 (2020): Bulletin of Geology
Publisher : Fakultas Ilmu dan Teknologi Kebumian (FITB), Institut Teknologi Bandung (ITB)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/bull.geol.2020.4.1.3

Abstract

Penelitian ini dilatar belakangi oleh adanya endapan laterit yang berasal dari litologi yang berbeda pada Area Wailukum, Daerah Buli, Kabupaten Halmahera Timur. Daerah penelitian merupakan bagian dari IUP PT. Antam UBPN Maluku Utara. Koordinat area penelitian berada di 412.369-413.763mT dan 89.304-88.384mU zona 52N, dengan luas area penelitian sebesar 1,4km2. Penelitian ini bertujuan untuk mengetahui karakteristik endapan laterit dan batuan dasar di Area Wailukum. Data yang digunakan berupa DEM, data lapangan, sertadata bor. Analisis DEM dan data lapangan digunakan untuk penentuan satuan topografi. Analisis data lapangan bertujuan untukpeta danpenampang geologi. Analisisgeostatistik pada data bor yang terdiri dari data assay (470 sampel) dan deskripsi bor bertujuan untuk menentukan karakteristik endapan laterit dan batuan dasar dari area penelitian.Berdasarkan hasil analisis petrografi sayatan tipis, didapatkan jenis batuan dasar berupa serpentinit, orthopiroksenit terserpentinisasi sedang dan olivin gabbronorit terserpentinisasi lemah. Kompleks melange berupa serpentinit, orthopiroksenit dan olivin gabbronorit dalam bentuk boudinage yang dilingkupi oleh serpentinit berfoliasi. Keberadaan melange ini diperkirakan hasil dariproses kolisi. Berdasarkan analisis diagram terner SiO2-MgO-Fe2O3, tipe lateritisasi berupa dry laterites dengan pengendapan silika. Endapan laterit terbagi menjadi limonit dan saprolit. Satuan topografi dibagi menjadi hill slope dan lowland basin. Pada area hill slope, terdapat proses longsor yang menyebabkan lebih tipisnya endapan laterit yang terbentuk.Litologi dapat dibagi menjadi litologi yang didominasi gabbrodan litologi yang didominasi serpentinit. Pada litologi yang didominasi gabbro, lateritisasitidak berlangsung dengan baik dan tidak ditemukan zona bijih. Pada litologi yang didominasi serpentinit,lateritisasiberlangsung dengan baik dan ditemukan zona bijih pada bagian saprolit dan bagian bawah limonit. Ni berada dalam serpentin kaya nikel sehingga Ni berkorelasi positif kuat dengan Co, Fe, MnO, dan Cr2O3. Pada area lowland basin, terdapat akumulasi hasil longsor yang menyebabkan endapan laterit tebal danzona bijih berada di limonit. Kata kunci: Endapan Laterit, Batuan Dasar, Melange, Wailukum, Halmahera Timur
Co-Authors Abdul Bari Bambang Priadi Bastian, Arief Draniswari, Windi Anarta R, Yan Rizal Ramadhan, Aditya Rizki Rezki Naufan Hendrawan Sapiie, Benjamin Sutopo, Bronto Wahyuni, Fitri Indah