Abstract

• The study area is located within southern part of the Mogok Metamorphic Belt and Slate belt, Kyaikhto Township of Mon State, Myanmar. It is consisting of meladiorite, diorite and granitic rocks intruded by a variety of lamprophyre dykes. Most of lamprophyres are fine-grained, porphyritic in nature, with phenocrysts of hornblende, feldspar and sometimes biotite. Occasionally, medium-grained textures of spessartite are observed and their strikes are trending NE direction. There are three types of lamprophyre encountered in the study area, which are camptonite, minette and spessartite. The whole rock chemical compositions are wide span range of SiO2 (52.47-60.06), CaO (4.28-6.8), MgO (2.5-5.1) and Fe2O3 (5.6-9.6) consisting mainly of calcalkaline to high-K calc-alkaline. Lamprophyres fall within the basaltic andesite-basaltic andesite, and trachy-andesite field. Enrichments in Cs, Rb, Ba and Th while depletion in Nb, and Ti were generated from the partial melting of the subducted related shallower mantle lithosphere. Trace element ratios, the pattern of the LREE to HREE show that the rocks were come from spinel lherzolite mantle (< 50 km depth) rather than garnet lherzolite mantle source. Calc-alkaline of lamprophyre related to the eastward late-subduction of Tethys II of the ancestral Indian Ocean.