GEOCHEMICAL EVIDENCE OF ISLAND-ARC ORIGIN IN VOLCANIC ROCKS OF CENTRAL SUMATERA

Iskandar Zulkarnain

doi:10.14203/risetgeotam2014.v24.79

GEOCHEMICAL EVIDENCE OF ISLAND-ARC ORIGIN IN VOLCANIC ROCKS OF CENTRAL SUMATERA

Iskandar Zulkarnain

Abstract

Abstract. Geochemical study on volcanic in Lampung and Bengkulu regions proposed a preposition that the western part of Sumatera is formed by a separated fragment with island-arc character and does not belong to continental margin of Eurasia. Geochemical signatures of western and eastern volcanic in Central Sumatera have confirmed the preposition indicated by evidences of existing island-arc tectonic environment on the western volcanic and both island-arc and continental tectonic environments on the eastern volcanic. Besides that, the geochemical data in this region have revealed the third tectonic environment reflecting development of back-arc tectonic setting in the geological history of the island. The island-arc tectonic setting is marked by higher ratio of (Ti/Ce)N, varying from 0.15 to 0.3, but in narrow ratio of (Ta/Nb)N, between 1.0 to 1.5, while the Active Continental Margin tectonic environment is characterized by wide range of (Ta/Nb)N ratio, ranging from 1.2 to 2.8 but with ratio of (Ti/Ce)N less than 0.1. The back-arc basin tectonic setting is marked by high ratio of (Ti/Ce)N, up to more than 0.8. The results are made based on rock chemistry analysis including major, trace and rare earth elements.

Keywords

geochemical, volcanic, Sumatera, island-arc, continental, preposition, back-arc basin.

Full Text:

PDF

References

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, 713–738.

Barber, A.J. & Crow, M.J., 2003. Evaluation of plate tectonic models for the development of Sumatera. Gondwana Research, vol. 20, 1-28.

Cameron, N.R., M.C.G. Clarke, D.T. Aldis, A.A. Aspden, dan A. Djunuddin, 1980. The geological evolution of Northern Sumatra. Procc Indon. Petrol. Assoc. 9th Ann Conv. hal. 149-187.

Crow M.J., 2005. Pre-Tertiary volcanic rocks, In: Barber, A.J., Crow, M.J & Milsom, J.S., 2005, Sumatra: Geology, Resources and Tectonic Evolution, The Geological Society, London.

Curray, J.R., 1989, The Sunda Arc: a model for oblique plate convergence, Netherlands Journal of Sea Research, vol.24, 131-140.

Fitch TJ., 1972, Plate convergence, transcurrent faults and internal deformation adjacent to southeast Asia and the western Pacific, J. Geophys. Res., 77:4432–60.

Hamilton W., 1974, Earthquake map of the Indonesian region, USGS Misc. Invest. Ser. Map I-875C

Hamilton W., 1979, Tectonics of the Indonesian Region, U.S. Geol. Surv. Prof. Pap., 1078:345.

Le Bas, M. J., Le Maitre, R. W., Streckeisen, A. and Zanettin, B., 1986, A chemical classification of volcanic rocks based on the total alkali–silica diagram, Journal of Petrology, vol. 27, 745–750.

Metcalfe, I., 1998, Paleozoic and Mesozoic geological evolution of the SE Asia Region: multidisciplinary constraints and implications for biogeography, Biogeography and Geological Evolution of SE Asia, (edt) R. Hall dan J.D. Holloway, Backhuys Publishers, Leiden, The Netherlands, hal. 25-41.

Miyashiro, A., 1974, Volcanic rock series in island-arcs and active continental margins, American Journal of Science, vol.274, 321–355.

Pearce, J.A., 1983, The role of sub-continental lithosphere in magma genesis at destructive plate margins. In Hawkesworth, C.J. & Norry, M.J. (eds), Continental basalts and mantle xenoliths, Nantwich: Shiva, 230-249.

Pulunggono, A. and N. R. Cameron, 1984, Sumatran microplates, their characteristics and their role in the evolution of the central and South Sumatra basins, Procc Indon. Petrol. Assoc. 30th Ann Conv, hal. 121-144.

Simons, W.J.F., Socquet, A., Vigny, C., Ambrosius, B.A.C., Haji Abu, S., Promthong, Chaiwat, Subarya, C., Sarsito, D.A., Matheussen, S., Morgan, P., Spackman, W., 2007. A decade of GPS in Southeast Asia: resolving Sundaland motion and boundaries, J. Geophys.Res.,112, B06420. DOI:10.1029/2005JB003868

Wilson, M., 1989, Igneous Petrogenesis; a global tectonic approach, Unwin Hyman, London, 466pp.

Zulkarnain, I., 2007, Geochemical character of Hulusimpang Formation volcanic around Kota Agung area and their genetic implication, Jurnal JTM international edition, vol. XIV, No.3, 156-167.

Zulkarnain, I., 2011, Geochemical Evidence of Island-arc Origin for Sumatera Island; A New Perspective based on Volcanic Rocks in Lampung Province, Indonesia, Jurnal Geologi Indonesia, vol.6, No.4.

Zulkarnain, Iskandar, 2012, New Geochemical Data of Island-Arc Origin for Sumatera: The Bengkulu Case, RISET Geologi dan Pertambangan, Vol. 22, No. 1, 11-23.

DOI: http://dx.doi.org/10.14203/risetgeotam2014.v24.79