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Karakteristik Geokimia Basal Alkali Formasi Manamas di Sungai Bihati, Baun, Pulau Timor Widiatama, Angga Jati; Santy, Lauti Dwita; Natalia, Happy Christin; Wahyudiono, Joko; Ikhram, Rinaldi
EKSPLORIUM Vol. 42 No. 1 (2021): MEI 2021
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17146/eksplorium.2021.42.1.6205

Abstract

The igneous rock of Manamas Formation in the Bihati River, Baun is one of the igneous rock outcrops in Timor Island that has not been widely studied based on its geochemical characteristic. This study aims to determine the genesis and processes that occur in the igneous rocks of the Manamas Formation within tectonic framework of Timor Island based on petrographic and geochemical analysis. X-ray Fluorescence (XRF) and Inductively Coupled Plasma-mass Spectrometery (ICP-MS) were used to determine the major elements, trace elements, and rare earth elements. The igneous rock of the Manamas Formation is a basalt intrusion with an alkaline affinity which shown an enrichment pattern of rare earth elements identical to Ocean Island Basalt (OIB). This study proves the existence of two different mechanisms of elemental enrichment, fluid related enrichment which related to the subduction activity of the Indian Ocean plate under the Banda Arc and also melt related enrichment which originated from the broken Indian Ocean plate which enters the OIB reservoir zone. The two different magmas then mix and underplating beneath the Banda Arc.
Review on Granitic Rocks in Sumatra: Intrusion Process, Classification, Mineralization, and Potential Uses Irzon, Ronaldo; Syaeful, Heri; Kusworo, Aries; Wahyudiono, Joko; Ngadenin
EKSPLORIUM Vol. 43 No. 1 (2022): MAY 2022
Publisher : BRIN Publishing

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.17146/eksplorium.2022.43.1.6471

Abstract

Granitic rocks are widely distributed in Sumatra and surrounding areas. These granitoids are classified into several granite provinces of Southeast Asia with different intrusion processes and specific characteristics. This paper aims to review the intrusion of granitic rocks in Sumatra and describe the opportunities associated with it. Granite rocks are used to manufacture cultural heritage, works of art, and ornaments because of their weathering resistance, color diversity, and hardness characters. S-type granite intrusion in Sumatra might be associated with tin mineralization while silver-gold with the I-type. Theoretically, granite contains more REE than other igneous rocks. Mining and extraction difficulties complicate the direct REE exploitation from fresh granite. A-type granite relatively contains more REE than the other types, but this type of granite is not correlated with certain provinces. Indonesia has a tropical climate which is prone to weathering. Therefore, it is possible for REE and/or bauxite enrichments in the granite weathering horizon. Granite is assumed to be a potential source of uranium and thorium, especially for the S-type, because it is formed through the compression of sediments that can absorb these radioactive elements from the continental crust.