Ciri Geokimia Batuan Vulkaniklastika di daerah Tanjung Balit, Sumatra Barat: Suatu Indikasi Kegiatan Magma pada Eosen

Bhakti H. Harahap

Abstract


DOI: 10.17014/ijog.v5i2.94

Volcaniclastic rocks exposed in the Tanjung Balit area, West Sumatra, are red in color, loose, soft, and fractured. The rocks are strongly altered to be clay with calcium (CaO) and natrium (Na2O) contents extremely low (0.02 and maximum 0.30wt% respectively), and high loss of ignition (LOI) (4-15wt%). Mobile minor elements such as strontium (Sr), rubidium (Rb), and lanthanum (La) are also changed as their values do not fit to a normal contents range of fresh volcanic rocks in general. Geochemical analyses of the rocks resulted in the following oxide values: silica (SiO2) ranges from 58 – 68wt%, alumina (Al2O3) 15,90 – 21,46wt%, magnesium (MgO) 1, 36 – 1.61wt%, iron oxides (Fe2O3) 4,8-6,9wt%, potassium (K2O) 2,73 - 4,23wt% and titanium (TiO2) 0,60 - 0,70wt%. In general, the element contents especially the immobile ones (Ti, Mg and Fe) show that the rocks were originated from magmatic activity, which is also supported by petrographical characteristics that are still showing felspar and quartz minerals relicts. Based on SiO2 versus K2O diagram, these rocks are classified as high K-calc-alkaline series and belong to an intermediate composition. The rocks of the above criteria such as high alumina, very low magnesium and less than 1% titanium are one of the evidences that they are a magmatic arc product. The trace element of the rocks is summarized on the spider diagram; here their patterns strongly resemble to the typical of magmatic arc as well with enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE) relative to high field strength elements (HFSE) and heavy REE (HREE). Trace element pattern and REE suggest they were originated from a high K- calc-alkaline magma source.


Keywords


volcaniclastics; calc-alkali; petrography; arc magma; Tanjung Balit

References


Abidin, H.Z., 2008. Pb-Zn-Ag Deposits at Tanjung Balit, Limapuluh Kota Regency, West Sumatra. Jurnal Sumber Daya Geologi, 18, (4), h.253-263.

Asiedu, D.K., Suzuki, S, Nogami, K., dan Shibata, T., 2000. Geochemistry of Lower Cretaceous sediments, Inner Zone of Southwest Japan: Constraints on provenance and tectonic environment. Geochemical Journal, 34, h.155-173. DOI:10.2343/geochemj.34.155

Aspden., J.A., Kartawa, W., Aldiss, D.T., Djunuddin, A., Whandoyo, R., Diatma, D., Clarke, M.C.G., dan Harahap, H.,1982. The Geology of the Padangsidempuan and Sibolga Quadrangle (0717) Sumatra, scale 1:250 000. Geological Research and Development Centre, Bandung

Barber, A.J., 2000. The origin of the Woyla Terranes in Sumatra and the Late Mesozoic evolution of the Sundaland margin. Journal of Asian Earth Sciences 18, h.713-738. DOI:10.2343/geochemj.34.155

Bennet, J.D., Bridge, D. McC., Cameron, N.R., Djunuddin, A., Ghazali, S.A., Jeffrey, D.H., Kartawa, W., Keats, W., Rock N.M.S., Thompson, S.J., dan Whandoyo, R.,1981. The Geology of the Banda Aceh Quadrangle, Sumatra, scale 1:250 000. Geological Research and Development Centre, Bandung.

Cameron, N.R., Clarke, M.C.G., Aldis, D.T., Aspden, J.A., dan Djunuddin, A., 1980. The geology evolution of Northern Sumatra. Proceedings 9th Annual Convention IPA, h.149-187.

Cameron, N.R., Bennet, J.D., Bridge, D. McC., Clarke, M.G.C., Djunuddin, A., Ghazali,S.A., Harahap, H., Jeffrey, D.H., Kartawa, W., Keats, W., Ngabito, H., dan Rock N.M.S.,1983. The Geology of the Takengon Quadrangle (0520), Sumatra, Scale 1:250 000. Geological Research and Development Centre, Bandung.

Chan, M.A. dan Parry, W.T., 2009. Rainbow of Rocks Mysterias of Sandstone Colors and Concretions in Colorado Plateau Canyon Country. Public Information Series 77. Utah Geological Survey, h.1-17.

Clarke, M.C.G., Kartawa, W., Djunuddin, A., Suganda, E., dan Bagdja, M., 1982 a. Peta Geologi Lembar Pakanbaru, Sumatra, skala 1: 250 000. Pusat Penelitian dan Pengembangan Geologi, Bandung.

Clarke, M.C.G., Kartawa, W., Djunuddin, A., Suganda, E., dan Bagdja, M., 1982 b. Geologi Lembar Pakanbaru, Sumatra, skala 1: 250 000. Pusat Penelitian dan Pengembangan Geologi, Bandung.

Cox, K.G., Bell, J.D., dan Pankhurst, R.J., 1979. The interpretation of igneous rocks. London; Allen and Unwin, 450 h. DOI:10.1007/978-94-017-3373-1

Cox, K.G. dan Hawkesworth, C.J., 1985. Geochemical stratigraphy of the Deccan Traps at Mahabaleshwar, western Ghats, India, with implications for open system magmatic processes. Journal of Petrology, 26, h.355-377. DOI:10.1093/petrology/26.2.355

Crow, M.J., 2005. Tertiary Volcanicity. In: Barber, A.J. Crow, M.J., dan Milsom J.S., (eds.), Geology, Resources and Tectonic Evolution of Sumatra. Geological Society Memoir 31, h. 63-85. Geological Society of London. DOI:10.1093/petrology/26.2.355

Crow, M.J. dan Barber, A.J., 2005. Simplified geological map of Sumatra. In: Barber, A.J., Crow, M.J., dan Milsom, J.S. (eds.) Sumatra Geology, Resources and Tectonic Evolution, Geological Society Memoir, 31. DOI:10.1144/GSL.MEM.2005.031.01.17

Fontains, H. dan Gafoer, S., 1989. The Pre-Tertiary fossils of Sumatra and their environment. CCOP, Technical Papers, 19, United Nations Bangkok.

Gill, J.B., 1981. Orogenic andesites and plate tectonics. Berlin: Springer-Verlag, 358 h. DOI:10.1093/gji/73.2.581-a

Hamilton, W., 1979. Tectonics of the Indonesian region, US. Geological Survey Proffessional Paper 1078.

Harahap, B.H. dan Abidin, H.Z., 2006. Petrology of lava from Maninjau Lake, West Sumatra. Journal of Geological Resources, XVI (6), h.359-370.

Harahap, B.H., 2006. Magmatisme segmen utara Zone Bukit Barisan daerah Kabupaten Limapuluh Kota, Sumatra Barat. Pusat Survei Geologi (tidak diterbitkan).

Harahap, B.H., 2007. Petrologi batuan magmatis Neogen daerah Pangkalan Kotabaru Limapuluh Kota Sumatra Barat. Jurnal Sumber Daya Geologi, XVII (4), h. 2007-217.

Irvine, T. N. dan Baragar, W.R.A., 1971. A guide to the chemical classification of the common rocks. Canadian Journal of Earth Science, 8, h.523-48. DOI:10.1139/e71-055

Jakes, P. dan White, A.J.R., 1972. Major and trace element abundances in volcanic Rocks of orogenic areas. Geological Society of America Bulletin, 83, h.29-40. DOI:10.1130/0016-7606(1972)83[29:MATEAI]2.0.CO;2

Kastowo, Sukardi, Suparman, M., Sukanta, U., dan Mac. Endharto, 1978. Peta Geologi Lembar Lubuk Sikaping, skala 1:250 000. Direktorat Geologi, Bandung.

Miyashiro, A., 1974. Volcanic rock series in island arcs and active continental margins. American Journal of Science, 274, h.321-355. DOI:10.2475/ajs.274.4.321

Peccerillo, A. dan Taylor, S.R., 1976. Geochemistry of Eocene calc-alkaline volcanic rocks from the Kastamonu area, Northern Turkey. Contribution on Mineralogy and Petrology, 58, h.63-81. DOI:10.1007/BF00384745

Pigram, C.J. dan Panggabean, H., 1983. Geological Data Record of Waghete (Yapekopare) Quadrangle, Irian Jaya. Geological Research and Development Centre. Open file report (unpublished).

Rock, N.M.S., Aldiss, D.T., Aspden, J.A., Clarke, M.C.G., Djunuddin, A., Kartawa, W.,Miswar, S.J., Thompson, R., dan Whandoyo, R., 1983. The Geology of the Lubuk Sikaping Quadrangle (0716) Sumatra, scale 1:250 000. Geological Research and Development Centre, Bandung.

Sajona, F.G., Maury, R.C., Bellon, H., Cotton, J., dan Defant, M., 1996. High Field Strength Element Enrichment of Pliocene-Pleistocene Island Arc basalts, Zamboanga Peninsula, Western Mindanao (Philippines). Journal of Petrology, 37(3), h.693-726. DOI:10.1093/petrology/37.3.693

Silitonga, P.H. dan Kastowo, 1995. Peta Geologi Lembar Solok, Sumatra Barat, sekala 1:250 000. Pusat Penelitian dan Pengembangan Geologi, Bandung.

Visser, W.A. dan Hermes, J.J, 1962. Geological results of the exploration for oil in Netherlands New Guinea, Koningklijke Netherlands Mijnbouwkundig Genootschaft Verhandelingen, Geologische Serie, 20.

Wilson, M., 1989. Igneous Petrogenesis a global tectonic approach. Harper Collins Academic.

Wood, D.A., Joron, J.L., dan Treuil, M., 1979. A re-appraisal of the use of trace elements to classify and discriminate between magma series erupted in different tectonic settings. Earth Planetary Scientific Letters, 45, h.326-36. DOI:10.1016/0012-821X(79)90133-X


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