Petrogenesis of Ajil mafic dykes from Eastern Belt of Peninsular Malaysia: Fractionated within plate lithospheric mantle magma beneath the eastern Malaya Block

Abstract

North-eastern trending mafic dykes are found intruding granitic body in Ajil area, Eastern Belt of Peninsular Malaysia. The intrusions display sharp, vertical to sub-vertical contacts to granitic host and consist mainly of plagioclase and clinopyroxene. Majority of the dykes are quartz tholeiite with some olivine tholeiite. All dykes display enrichment in light rare earth elements (LREE) relative to heavy rare earth elements (HREE) and depletion in high field strength elements (HFSE) and Pb. Low compatible elements' content such as MgO, Ni and Cr implied that crystal fractionation were controlled by olivine and clinopyroxene. The dykes were originated from shallow lithospheric mantle, the source region of which has been influenced by hydrous metasomatism. The emplacement of the dykes took place in fault-controlled within-plate tectonic setting.