SEBARAN ALTERASI BATUAN BERDASARKAN RASIO Th/U DI TAPALANG, MAMUJU, SULAWESI BARAT

I Gde Sukadana, Frederikus Dian Indrastomo, Ngadenin Ngadenin

Abstract


Kecamatan Tapalang, Mamuju, menjadi tujuan eksplorasi uranium dengan adanya radiasi tinggi terdeteksi pada batuan basaltik Formasi Adang. Diperlukan lokalisasi daerah-daerah dengan tingkat potensi kandungan uranium yang tinggi. Proses alterasi meningkatkan tingkat kelarutan uranium, sehingga kadar uranium berkurang dan terjadi pengkonsentrasian torium serta logam tanah jarang (REE) yang signifikan. Dengan asumsi bahwa alterasi berasosiasi dengan rasio Th/U, maka dilakukan penelitian untuk mengetahui sebaran alterasi batuan berdasarkan korelasinya terhadap rasio Th/U. Penelitian dilakukan dengan pengukuran radioaktivitas dan pengamatan alterasi di lapangan, kemudian dilengkapi  dengan analisis XRF dan analisis mineragrafi untuk mengetahui tingkat alterasi. Rasio Th/U pada batuan lava Tapalang yang masih relatif segar memiliki nilai 3-30, dan batuan yang telah teralterasi memiliki nilai 30 - >3000. Pengembangan eksplorasi torium dapat difokuskan pada daerah dengan alterasi lanjut, sedangkan eksplorasi uranium harus difokuskan pada daerah yang bersifat reduktif, yang memungkinkan terbentuknya cebakan uranium.

Tapalang, Mamuju, is a destination for uranium exploration due to the high radiation detected in basaltic rocks of Adang Formation. Uranium potentials localization is required since uranium is not distributed evenly. An alteration process increases the level of uranium solubility, so that the uranium content is depleted and the concentration of thorium and rare earth elements (REE) are significantly high. This study objective was to find the distribution of rock alterations and their correlation to the ratio of Th/U in Tapalang Region. Research methods were combination of radioactivity measurement and alteration observation in the field, completed by XRF and mineragraphy analysis to measure the grade of alteration. The alteration product indicated that this area has been affected by hydrothermal alteration in the potassic zone. Th/U ratio of fresh Tapalang lava rocks has a value of 3-30, and alterated rocks have 30 - 3000 value. These values can be used to delineating alteration areas, which have high Th/U ratio (30 - >3000). The development of thorium exploration can be focused on advanced alteration areas, whereas uranium exploration should focus on reductive areas that allow for uranium deposited.

 


Keywords


Th/U ratio, alteration, thorium, uranium, Mamuju

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DOI: http://dx.doi.org/10.14203/risetgeotam2018.v28.661

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