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Journal : Eksplorium : Buletin Pusat Pengembangan Bahan Galian Nuklir

Peralihan Rezim Tektonik: Implikasinya pada Konsentrasi Torium di Mamasa dan Tana Toraja, Sulawesi-Indonesia Saputro, Sugeng Purwo; Purwaningsih, Dwi Ratih; Priadi, Bambang
EKSPLORIUM Vol. 41 No. 2 (2020): NOVEMBER 2020
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17146/eksplorium.2020.41.2.6063

Abstract

Mamasa and Tana Toraja geographically are part of the western arm of Sulawesi Island. The mafic rocks in these areas and their surroundings have high radiation dose rate and thorium (Th) anomaly content. This research aim is to determine tectonic setting mechanism which play the important role on the increasing of Th concentration. Six rock samples were analysed using petrography and geochemical analyses (AAS, ICP-MS, NA, and XRF) completed with the 40K-40Ar dating on selected rock samples. Petrography observations show plagioclase, olivine, pyroxene, hornblende, nepheline, and allanite minerals presence in the rocks which identified as nepheline-basanite, basalt, trachybasalt, and gabbro. Numbers of texture appearances in the rocks indicate contamination and changes on tectonic setting. Geochemistry analysis shows that nepheline-basanite, basalt, trachybasalt, and gabbro (absarokite) were formed at the active continental margin (ACM), which is undergoing active subduction (westward subduction) to post-subduction transition. The changing of tectonic setting made magma solidify in extreme conditions. The magma solidify process is interpreted to occur at the age of 13.10-11.02 Ma. These mechanisms play an important role for the increase of thorium concentration in Mamasa and Tana Toraja.
Aplikasi Metode Geolistrik dan Analisis X-Ray Diffraction (XRD) untuk Investigasi Longsor di Pidada, Kecamatan Panjang, Bandar Lampung Mulyasari, Rahmi; Suharno; Haerudin, Nandi; Hesti; Yogi, Ida Bagus Suananda; Saputro, Sugeng Purwo
EKSPLORIUM Vol. 42 No. 2 (2021): NOVEMBER 2021
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17146/eksplorium.2021.42.2.6304

Abstract

Bandar Lampung is a densely populated urban area consisting of land and water with several plateaus and mountains that stretch across this region. To support sustainable development in a city area, it is necessary to have a regional arrangement concept that considers all aspects, one of which is the potential disaster aspect. One of the potential disasters in Bandar Lampung, especially in Panjang District is a mass movement/landslide. Based on previous research, this area has been recorded as having several historical points of landslides, but there is no mitigation/response specifically for this type of disaster. The purpose of this study was to determine the arrangement of rocks that are in the landslide-prone zone in Panjang District using the geoelectric resistivity method and to analyze the soil engineering assessment obtained from the results of lithological analysis using X-Ray Diffraction (XRD). The results of the geoelectric analysis indicate that there are three lithological layers in the study area; namely tuff sediments with resistivity values and depths between (1–40 Ωm; 0.4–4 m), clay sand (40–120 Ωm; 2–4 m), and solid breccias with igneous rock components (>120 Ωm; 2–22 m). Furthermore, based on the results of the analysis of soil engineering assessments, tuff sediment as a surface layer that has experienced landslides has been identified as having susceptible lithological engineering properties because it has undergone quite intensive oxidation and weathering. The data obtained is expected to be used as supporting data for disaster potential-based regional planning.