• R.I H Sulistyawan Pusat Survei Geologi
  • Baharuddin Baharuddin
  • U Hartono



The Jelai volcanics are exposed at Mount Rian and the surrounding area, northeastern part of Kalimantan. Major, trace and rare earth element data are presented. The volcanics consist of basalt to andesite with silica content ranging from about 52 to 63.5 wt%. Fractional crystallization involving olivine, pyroxene, plagioclas, and magnetite may resposible for the geochemical variation in the volcanics. However, there is a silica gap about 5wt% between basaltic andesite and andesite. Two trends of fractionation are observed, i.e., the tholeiitic and calc-alkaline trends in the basaltic and andesitic magmas respectivelly. Precipitation of magnetite, as a new phase, in the andesitic magma might change the fractionation from tholeiitic to calc-alkaline trends. Initial crystallization of Fe-Ti magmentite, pyroxene and plagioclase, that produce a rapid compositional change in the residual basaltic andesite to andesite liquids over a small temperature interval would cause a compositional gap.

Keyword : Mount Rian volcanics, geochemistry, compositional gap


Download data is not yet available.


Baharuddin, 2011. Petrologi dan geokimia Batuan Gunungapi Tersier Jelai di daerah Malinau Kalimantan Timur. Jurnal Sumber Daya Geologi, vol. 21, no. 4: 203-211.

Carlile, J.C. and Mitchell, A.H.G., 1994. Magmatic areas and associated gold and copper mineralization in Indonesia. In T.M. Van Leeuwen, J.W. Hedenquist, L.P. James and J.A.S. Dow (eds.). Indonesian Mineral Deposits-Discoveries of the past 25 years. J. Geochem. Explor. 90: 91-142.

Clague, D. A., 1978. The oceanic basait-trachite associa­tion: an explanation of the Daly Gap. J. Geology. 86: 739 - 743.

Fudali, R.F., 1965. Oxygen fugacities of basaltic and andesitic magmas. Geochim. Cosmochim. Acta, 29: 1063-1075.

Grove, T.L. and Baker, M.B., 1984. Phase equilibria controls on the tholeiitic versus calc-alkaline differentiation trends. J. Geophys. Res., 89: 3253-3274.

Grove, T.L. and Donnelly-Nolan, J. M,. 1986. The evolution of Young silicic lavas at Medicine Lake volcano. California: Implication for the origin of composi­tional gaps in calc-alkaline series lavas. Contrib. Mineral. Petrol., 92: 281 - 302.

Hartono, U. (ed), 2012. Magmatism in Kalimantan. Centre for Geological Survey, Geological Agency, Ministry of Energy and Mineral Resources.

Hartono, U., 2003. A Geochemical Study on the Plio-Pleistocene Magmas from Kalimantan. Their influence to the Tertiary Mineralization System in Kalimantan. Majalah Geologi Indonesia, v. 18, No. 2 Agustus : 168-174.

Hartono, U. and Sulistyawan, R.I.H., 2011. An overview of arc magma petrogenesis. J. of Geological Resources, v. 21, No.4: 179-190.

Hartono, U. and Sulistyawan, R.I.H., 2010. Origin of Cretaceous high magnesian andesites from Southeast Kalimantan. J. of Geological Resources, v. 20, No.65: 261-276.

Heryanto, R., Supriatna, S. and Abidin, H.Z., 1995. 1 : 250,000 Geological map of the Malinau Sheet, Kalimantan. Geological Research and Development Centre, Bandung.

Heryanto, R. and Abidin, H.Z., 1995. 1 : 250,000 Geological map of the Napaku Sheet, Kalimantan. Geological Research and Development Centre, Bandung.

Osborn, E.F., 1969. Experimental aspects of calc-alkaline differentiation. In: Proceding of the andesite coverence, McBirney, A.R. (ed). Dept.Geol. Min. Res. Oreg. Bull., 65: 33-42.

Soeria-Atmadja, R., Noeradi, D. And Priadi, B., 1999. Cenozoic magmatism in Kalimantan and its related geodinamic evolution. Journal of Asian Earth Sciences, 17: 25 – 45.

Weaver, S. D., 1977. The Quaternary caldera volcano Emuruangogalak, Kenya Rift, and petrology of a bimodal ferrobasalt-pantelleritic trachite associa­tion. Bull. Volcanol, 40: 209 - 227.