SINTESIS GEOLOGI DAN KEMUNGKINAN KEDAPATAN CEBAKAN URANIUM DI SULAWESI

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ABSTRAK

SINTESIS GEOLOGI DAN KEMUNGKINAN KEDAPATAN CEBAKAN URANIUM DI SULAWESI. Eksplorasi U di Sulawesi Barat telah dilakukan oleh Pusat Pengembangan Geologi Nuklir – BATAN  dari 1978 – 1984. Hasil eksplorasi belum bisa menyimpulkan tipe cebakan U yang mungkin terbentuk di Sulawesi Barat. Tujuan penulisan makalah ini adalah untuk mengetahui cebakan U yang mungkin terbentuk di Sulawesi Barat. Metoda yang digunakan adalah dengan menggabung data geologi, radioaktivitas batuan dan kadar U total batuan dari Sulawesi Barat ditambah data hasil analisis butir mineral berat dan data hasil pengamatan ulang analisis petrografi khusus dari daerah Masamba, Sulawesi Selatan. Berdasarkan data tersebut kemudian dikaji kemungkinan cebakan U yang bisa terbentuk dengan mengacu teori pembentukan cebakan U secara umum. Litologi Sulawesi Barat tersusun oleh kelompok batuan metamorfosa berumur Trias, kelompok batuan sedimen klastika berumur Tersier Awal termasuk Kapur Akhir, kelompok batuan terobosan asam – menengah berumur Tersier, kelompok batuan vulkanik laut berumur Tersier Tengah dan Akhir, kelompok batuan klastika dan karbonatan berumur Tersier Awal – Tengah, kelompok batuan vulkanik berumur Tersier Tengah- Akhir, kelompok batuan sedimen Tersier Akhir sebagian sedimen laut Kuarter, kelompok batuan endapan Kuarter dan vulkanik Tersier Akhir, kelompok batuan produk letusan vulkanik aktif dan kelompok endapan aluvium, endapan teras pantai dan danau terisolasi. Anomali radioaktivitas dan kadar U batuan terdapat pada batuan metamorfosa Trias, klastika Tersier Awal termasuk Kapur Akhir, batuan intrusi asam-menengah Tersier,  vulkanik Tersier Tengah-Akhir dan batuan sedimen Tersier Akhir. Monasit, zirkon, thorit dan alanit adalah mineral-mineral radioaktif yang terdapat dalam batuan intrusi asam-menengah berumur Tersier. Berdasarkan data geologi, radioaktivitas batuan, hasil analisis kadar U, petrografi dan butiran mineral berat batuan maka cebakan U yang mungkin terbentuk di Sulawesi Barat ádalah cebakan U tipe plaser. Batuan terobosan asam-menengah berumur Tersier sebagai sumber U dan endapan aluvium hasil rombakannya sebagai tempat mineral radioaktif diendapkan. Cebakan tersebut terdapat pada endapan aluvium  di sekitar daerah Masamba.

Kata Kunci : geologi, cebakan, uranium, plaser, Sulawesi Barat

ABSTRACT

SYNTHESIS OF GEOLOGY AND POSIBILITY OF URANIUM DEPOSIT OCCURENCES IN SULAWESI. U exploration in West Sulawesi has been conducted by the Center for Development Nuclear Geology from 1978 to 1984. Exploration results can not yet conclude the type of U deposits that will be formed in the West Sulawesi. The purpose of this paper is to determine the U deposits that may be formed in West Sulawesi. The method used is to merge the data of geology, radioactivity and total U content of the rocks from the West Sulawesi and also data of heavy mineral and petrographic analysis from Masamba, South Sulawesi. Based on these data, it was examined the type of U deposits that can be formed by referring to the theory of U deposits occurrences. Lithology of West Sulawesi constructed by Triassic metamorphic rocks group, late Cretaceous to early Tertiary clastic sedimentary rocks group, middle Tertiary acid to intermediate intrusive rock group, middle and late Tertiary marine volcanic rocks group, early to middle Tertiary clastic and carbonaceous rocks group, middle to late Tertiary volcanic rocks group. late Tertiary sedimentary rocks group include Quaternary marine sedimentary rocks, Quaternary sediments and late Tertiary volcanic rocks group, eruption product of active volcanic group and group of alluvium, beach terrace and isolated lakes sediments. Anomalous of U content and rock radioactivity found in Triassic metamorphic rocks group, late Cretaceous to early Tertiary clastic sedimentary rocks group, Tertiary acid to intermediate intrusive rocks, middle to late Tertiary volcanic rocks and late Tertiary sedimentary rocks. Monazite, zircon, thorite and allanite are radioactive minerals that was found at Tertiary acid to intermediate intrusive rocks. Base on the data of geology, radioactivity of rock, analysis of U content, petrography and heavy mineral analysis was concluded  that U deposit which may be formed at West Sulawesi is placer deposits. Tertiary acid to intermediate intrusive rocks as a source rock and the alluvial deposits result of its rework as a place of radioactive minerals were deposited.  The placer deposits located around Masamba area.

Key word : geology, deposits, uranium, placer, West Sulawesi.