Evaluasi Sistem Pengendapan Uranium Pada Batuan Sedimen  Formasi Sibolga, Tapanuli Tengah

I Gde Sukadana; Heri Syaeful

doi:10.17146/eksplorium.2016.37.2.3112

Evaluasi Sistem Pengendapan Uranium Pada Batuan Sedimen Formasi Sibolga, Tapanuli Tengah

I Gde Sukadana, Heri Syaeful

DOI: http://dx.doi.org/10.17146/eksplorium.2016.37.2.3112

Sari

ABSTRAK

Uranium di alam dapat terbentuk dalam berbagai tipe cebakan, sesuai dengan sumber, proses, dan lingkungan pengendapannya. Keterdapatan uranium di Sibolga pada batuan sedimen Formasi Sibolga merupakan suatu potensi yang layak untuk dikembangkan tetapi hingga saat ini belum diketahui pola pengendapan dan proses mineralisasi uranium tersebut. Penelitian bertujuan untuk mengetahui pola sebaran batuan dan keterdapatan anomali kadar uranium berdasarkan data geologi, radiometri permukaan, dan data log bor untuk mengetahui proses pengendapan batuan dan mineralisasi uranium. Keterdapatan mineralisasi berdasarkan data log bor tersebar dari satuan konglomerat alas (Kgl 1), satuan batupasir 1 (Bp 1), satuan konglomerat 2 (Kgl 2), dan satuan batupasir 2 (Bp 2) dengan ketebalan dan sebaran semakin ke atas semakin menipis. Sebaran mineralisasi pada bagian timur pada satuan batuan konglomerat 1 lebih didominasi oleh mineral detrital hasil pengendapan epigenetik berupa monasit yang terbentuk pada saat pembentukan granit sebagai batuan sumber. Pada satuan batuan di atasnya mineralisasi berbentuk pola alur (channel) yang berarah timur laut-barat daya, yang terbentuk secara syn-genetic dengan mineral berupa uraninite, carnotite, dan coffinite. Pengendapan batuan Formasi Sibolga berasal dari timur ke arah barat dan pengendapan uranium terjadi akibat perbedaan kondisi lingkungan pengendapan dari oksidasi di bagian timur menjadi lebih reduktif di bagian barat daya. Peningkatan kandungan material organik yang cukup tinggi pada lingkungan pengendapan bagian barat daya menyebabkan lingkungan pengendapan dalam kondisi reduksi.

ABSTRACT

Uranium in nature formed in various deposit type, depends on its sources, process, and depositional environments. Uranium occurrence in Sibolga, hosted in sedimentary rocks of Sibolga Formation, is properly potential to develop; nevertheless, the depositional pattern and uranium mineralization process so far had not been recognized. The research aim is to determine the rock distribution patterns and the existence of uranium grade anomalies based on surface geology and borehole log data. Mineralization occurrences from borehole log data distributed from basalt conglomerate unit (Kgl 1), sandstone 1 unit (Bp 1), conglomerate 2 unit (Kgl 2), and sandstone 2 unit (Bp 2) with their distribution and thickness are thinning to the top. Mineralization distribution in the eastern area, mainly on Kgl 1 unit, dominated by detritus materials from epi-genetic depositional in the form of monazite which is formed along with the formation of granite as its source rock. Meanwhile, mineralization on the upper rocks units formed a channel pattern trending northeast-southwest, which formed in syn-genetic process consist of uraninite, carnotite, and coffinite. Sibolga Formation deposition originated from east to west and uranium deposit formed because of the differences of depositional environment from oxidation in the east to the more reductive in the southwest. The increasing of organic materials in southwest basin caused the reduction condition of depositional environment.

Kata Kunci

sedimen; uranium; mineralisasi; granit; Sibolga

Teks Lengkap:

PDF

Referensi

[1] P. Bruneton and M. Cuney, Geology of Uranium Deposits, no. 1956. Elsevier Ltd, 2016.

[2] R. P. Kusumadinata and S. Sastrowihardjo, “Uranium Prospect in Tertiary Sediments in the Sibolga Area, North Sumatera,” in Uranium Deposits in Asia and the Pacific: Geology and Exploration, 1988, pp. 121–140.

[3] S. A. Cumberland, G. Douglas, K. Grice, and J. W. Moreau, “Uranium Mobility in Organic Matter-Rich Sediments: A Review of Geological and Geochemical Processes,” Earth Sci. Rev., 2016.

[4] C. S. Spirakis, “The Roles of Organic Matter in the Formation of Uranium Deposits in Sedimentary Rocks,” vol. 8, pp. 53–69, 1996.

[5] M. Masdja, S. Sastrowihardjo, and P. Tampubolon, “Uranium Mineralisation in Sibolga Formation at Aloban, North Sumatera,” In Seminar on Uranium Exploration, Geology and Extraction, 1989, pp. 123–144.

[6] J. A. Aspde, W. Kartawa, D. T. Aldiss, A. Djunuddin, D. Diatma, M. C. G. Clarke, R. Whandoyo, dan H. Harahap, “Peta Geologi Lembar Padang Sidempuan dan Sibolga, Sumatera,” Pusat Penelitian dan Pengembangan Geologi, 1992.

[7] A. G. Muhammad, M. Nurdin, H. Syaeful, dan P. Widito, “Survey Geolistrik Tahanan Jenis di Daerah Aloban dan Sekitarnya, Sibolga, Sumatera Utara,” Eksplorium, vol. 33, no. 1 Mei, 2012.

[8] M. Cuney, “The Extreme Diversity of Uranium Deposits,” Miner. Depos., vol. 44, no. 1, pp. 3–9, 2009.

[9] J. Wang, J. Liu, H. Li, Y. Chen, T. Xiao, G. Song, D. Chen, and C. Wang, “Uranium and Thorium Leachability in Contaminated Stream Sediments from a Uranium Minesite,” J. Geochemical Explor., pp. 6–11, 2016.

[10] D. Cinti, P. P. Poncia, L. Brusca, F. Tassi, F. Quattrocchi, and O. Vaselli, “Spatial Distribution of Arsenic, Uranium and Vanadium in the Volcanic-Sedimentary Aquifers of the Vicano-Cimino Volcanic District (Central Italy),” J. Geochemical Explor., vol. 152, pp. 123–133, 2015.

[11] K. Ullah, N. U. Khattak, A. A. Qureshi, M. Akram, H. A. Khan, and A. Nisar, “Search for Uranium Source in Warcha Sandstone, Salt Range, Pakistan, Using SSNTD Technique,” vol. 40, pp. 491–495, 2005.

[12] M. Cuney, A. Emetz, J. Mercadier, V. Mykchaylov, V. Shunko, and A. Yuslenko, “Uranium Deposits Associated with Na-Metasomatism from Central Ukraine : A Review of Some of the Major Deposits and Genetic Constraints,” Ore Geol. Rev., vol. 44, pp. 82–106, 2012.

[13] M. Min, J. Chen, J. Wang, G. Wei, and M. Fayek, “Mineral Paragenesis and Textures Associated with Sandstone-Hosted Roll-Front Uranium Deposits , Nw China,” vol. 26, pp. 51–69, 2005.

[14] S. M. Zaid, M. I. Moustafa, and M. G. Barakat, Mineralogy, Chemistry and Radioactivity Of The Heavy Minerals in the Black Sands, along the Northern Coast Of Egypt. Elsevier Ltd, 2016.

[15] J. Eagling, P. J. Worsfold, W. H. Blake, and M. J. Keith-Roach, “Influence of Sediment Redox Conditions on Uranium Mobilisation During Saline Intrusion,” Chem. Geol., vol. 357, pp. 158–163, 2013.

[16] S. Ortaboy and G. Atun, “Kinetics and Equilibrium Modeling of Uranium(Vi) Sorption by Bituminous Shale from Aqueous Solution,” Ann. Nucl. Energy, vol. 73, pp. 345–354, 2014.

[17] Q. J. Fisher and P. B. Wignall, “Palaeoenvironmental Controls on the Uranium Distribution in an Upper Carboniferous Black Shale (Gastrioceras Listeri Marine Band) and Associated Strata; England,” Chem. Geol., vol. 175, no. 3–4, pp. 605–621, 2001.

[18] I. H. Saleh and A. A. Abdel-Halim, “Determination of Depleted Uranium Using a High-Resolution Gamma-Ray Spectrometer and Its Applications in Soil and Sediments,” Integr. Med. Res., 2015.