Various sources of rare earth element enrichment at Manamas volcanic rock, Timor Island

Abstract

Manamas volcanic rock formed due to crustal thinning in fore arc setting. This research aims to provide information and the enrichment process of rare earth elements in Manamas Formation on the Timor Island and their tectonic implication. Manamas volcanic rock exposed in Bihati River, Baun, Timor consists of two different types of basalts, namely alkaline basalt and sub alkaline basalt. Analysis using ICP-MS method shows enrichment in large ion lithophile element and high field strength element. Subalkaline basalt has N-MORB patterns and alkaline basalt have OIB patterns. The Nb element is relatively impoverished that indicates influence of subduction activities. Thorium and uranium elements also show significant enrichment, due to sedimentary rocks contamination or continental crust or directly from the asthenosphere due to magma upwelling. The two distinctive patterns interpreted due to slab tear phenomenon beneath Timor Island during Australia oceanic plate subduction and recycled oceanic crust beneath Banda Arc.