THE GEOCHEMICAL CHARACTERISTIC OF MAJOR ELEMENT OF GRANITOID OF NATUNA, SINGKEP, BANGKA AND SIBOLGA

Ediar Usman

Abstract


A study of geochemical characteristic of major elelemnt of granitoid in Western Indonesia Region was carried out at Natuna, Bangka, Singkep and Sibolga. The SiO2 contents of the granites are 71.16 to 73.02 wt%, 71.77 to 75.56wt% and 71.16 to 73.02wt% at Natuna, Bangka, and Singkep respectively, which are classified as acid magma. While in Sibolga the SiO2 content from 60.27 to 71.44wt%, which is classified as intermediate to acid magma. Based on Harker Diagram, the granites from Natuna, Bangka and Singkep as a co-genetic. In other hand the Sibolga Granite show as a scatter pattern. Granites of Natuna, Bangka and Singkep have the alkaline-total (Na2O + K2O) between 6.03 to 8.51 wt% which are classified as granite and alkali granite regime. K2O content ranges from 3.49 to 5.34 wt% and can be classified as calc-alkaline type. The content of alkaline-total of Sibolga granite between 8.12 to 11.81 wt% and classified as a regime of syenite and granite. The range of K2O is about 5.36 to 6.94wt%, and assumed derived from high-K magma to ultra-potassic types. Granites of Natuna, Bangka and Singkep derived from the plutonic rock types and calc-alkaline magma, while Sibolga granite magma derived from K-high to ultra-potassic as a granite of islands arc. Based on the chemical composition of granite in Western Indonesian Region can be divided into two groups, namely Sibolga granite group is representing the Sumatera Island influenced by tectonic arc system of Sumatera Island. Granites of Bangka and Singkep are representing a granite belt in Western Indonesian Region waters which is influenced by tectonic of back arc.

Keywords: magma, geochemical characteristic, major element and Western Indonesian Region


Kajian karakteristik geokimia dari unsur utama granitoid di Kawasan Barat Indonesia telah dilakukan di daerah Natuna, Bangka, Singkep dan Sibolga. Kandungan SiO2 granit Natuna antara 71,16 - 73,02%, Bangka antara 71,77 - 75,56%, Singkep antara 72,68 - 76,81% termasuk dalam magma asam. Granit Sibolga memiliki kandungan SiO2 antara 60,27 - 71,44% termasuk dalam magma menengah - asam. Berdasarkan Diagram Harker, granit Natuna, Bangka dan Singkep mempunyai asal kejadian yang sama (ko-genetik), sedangkan granit Sibolga membentuk pola pencar. Granit Natuna, Bangka dan Singkep mengandung total alkalin (K2O+Na2O) antara 6,03 - 8,51% termasuk dalam jenis rejim granit dan alkali granit. Berdasarkan kandungan K2O antara 3,49 - 5,34 %berat, bersifat kalk-alkali. Granit Sibolga mengandung total alkali antara 8,12 - 11,81% termasuk dalam rejim syenit dan granit, dan berdasarkan kandungan K2O antara 5,36 - 6,94% berasal dari jenis magma K-tinggi sampai ultra-potassik. Granit Natuna, Bangka dan Singkep berasal dari jenis batuan beku dalam dan magma kalk-alkalin yang berhubungan dengan penunjaman, sedangkan granit Sibolga berasal dari jenis magma K-tinggi - ultra-potassik sebagai granit busur kepulauan. Berdasarkan komposisi unsur kimia utama, granit di Kawasan Barat Indonesia dapat dibagi dalam dua, yaitu granit Sibolga yang mewakili P. Sumatera, dipengaruhi oleh sistem tektonik busur P. Sumatera. Granit Bangka dan Singkep dapat mewakili suatu jalur granit di perairan Kawasan Barat Indonesia yang dipengaruhi oleh tektonik busur belakang.

Kata kunci: jenis magma, karakteristik geokimia, unsur utama, dan Kawasan Barat Indonesia


Keywords


Magma;geochemical characteristic;major element;Western Indonesian Region

Full Text:

PDF

References


Batchelor, B.C., 1983. Late Cenozoic Coastal and Offshore Stratigraphy in Western Malaysia and Indonesia. Thesis Ph.D., Dept. Of Geology, University Malaya, Kuala Lumpur.

Darman, H. and Sidi, F.H., 2000. An outline of The Geology of Indonesia. Indonesian Association of Geologist, Jakarta: 192pp.

Hakim, A.S. and Suryono, N., 1994. Geological of the Teluk Butun & Ranai Sheet, Sumatera, Scale 1 : 250.000. Geological Research and Development Centre, Bandung.

Hamilton, W., 1978. Tectonics Map of the Indonesian Zone. Prepared on Behalf of The Ministry of Mines, Government of Indonesia and The Agency for International Development US. Department of State. Department of the Interior, United States Geological Survey Pub., Washinton.

Hamilton, W., 1979. Tectonics of the Indonesian Zone, United States Geological Surveys Professional Paper 1078. United States Government Printing Office, Washington: 345pp.

Ishihara, S., 1977. The Magnetit-series and Ilmenite-series Granitic Rocks. Mining Geol., 27: p.293-305.

Katili, J.A., 1980. Geotectonics of Indonesia, A Modern View. Directorate General of Mines, Jakarta: 271pp.

Muller, D. and Grove, D.I., 1997. Potassic Igneous Rocks and Associated Gold-Copper Mineralization. Second Updated and Enlarged Edition. Springer-Verlag Berlin Heidelberg: 238 pp.

Mustafa, M.A., Kurnio, H., Kamiluddin, U., Harsenanto, C.W., Rachmat, B., Hadi, P.H., Nurdin, N., 2012. Penelitian Keterdapatan Endapan Plaser Pembawa Timah Perairan Singkep Timur, Provinsi Kepulauan Riau. Pusat Penelitian dan Pengembangan Geologi Kelautan, Laporan Intern, Bandung: 100pp.

Mustafa, A. and Usman, E., 2013. Analisis Perbandingan Geokimia Granit dan Sedimen Dasar Laut di P. Singkep Bagian Timur, Provinsi Kepulauan Riau. Journal Geologi Kelautan, 11(3), Pusat Penelitian dan Pengembangan Geologi Kelautan, Bandung: p.131 - 140.

Patra Nusa Data (PND), 2006. Indonesia Basin Summaries (IBS), The Gateway to Petroleum Investment in Indonesia, Elnusa Jakarta: 466pp.

Peccerillo, A. and Taylor, S.R., 1976. Geochemistry of Eocene Calc-alkaline Volcanic Rocks from the Kastamonu Area, Northern Turkey. Contrib. Mineral Petrol 58: p.63-81.

Subandrio, A.S. and Soeria-Atmadja, R., 1995. Petrography Relationship and Uranium Distribution in the Sibolga Granitoid Complex, North Sumatera. Indonesia. Geosea Eighth Regional Conference on Geology, Mineral and Energy Resources of Southeast Asia. In Koesoemadinata, R.P. and Noeradi, D. (ed)., 2003. Indonesian Island Arcs: Magmatism, Mineralization and Tectonic Setting. ITB Press, Bandung: p.194-215.

Rollinson, H., 1995. Using Geochemical Data: Evaluation, Presentation and Interpretation. Longman Group Limited, London: 352pp.

Suparka, M.E., Martodjojo, S. and Soeria-Atmadja, R., 1990. Cretaceous-Early Tertiary Magmatic Belt in Java and its Surrounding areas. Prosiding Persidangan Sains Bumi and Masyarakat, Universiti Kebangsaan Malaysia, 9-10 Julai 1990, Kuala Lumpur: p.81-91.

Usman, E., 2010. A Comparison of Major Elements Between Marine Sediment and Igneous Rocks: As a Basic Determination of the Sediment Source at Ujung Penyusuk Waters, North Bangka, Bangka-Belitung Islands Province. Bulletin of The Marine Geology, 25(1). Marine Geological Institute, Bandung: p.1-12.




DOI: http://dx.doi.org/10.32693/bomg.30.1.2015.74