Abstract

• The objective of this paper is to present the main results of a comparative study of geochemistry and tectonic implication on Singu Area and Kyaukphyu-Webaung Area. The Singu area is composed mainly of the basaltic rocks from the younger lava of Singu Plateau. Singu Lava Plateau is made up of a thick pile of very fluid basaltic flows displaying segregation structure. They form a 100 km2 plateau which overlies Mio-Pliocene sandstones as well as the upper part of the Irrawaddy Formation. Most basaltic rocks of Singu area are aphanitic, glassy, and pyroclastic rocks in which plagioclase and pyroxene are major constituents with subordinate amounts of olivine and Fe-Ti oxides. Basaltic rocks often show porphyritic, vesicular and trachytic texture. Major element data suggest that the Singu lava are predominantly of basaltic trachyandesite and show the alkaline nature. According to the immobile trace element concentrations, the basaltic rocks are dominated by alkali basalt. The trace element geochemistry suggests geochemical characteristic of Within-Plate Basalt. Lavas from the Singu area show a clear intraplate character with no subduction signal. In Kyaukphyu-Webaung area, the basaltic rocks are mainly composed of olivine, plagioclase and pyroxene and minor amount of chrome spinel and opaque minerals. They show porphyritic, trachytic texture and reaction rims. According to the major element data, the volcanic rocks fall in tephrite, trachy basalt, basalt and basaltic andesite. They show tholeiitic and calc-alkaline character. The spider diagram of the basaltic rocks confirm that the basaltic lavas are originated from variable partial melting degrees of subduction-related mantle source and island arc nature. The trace element analyses of the basaltic rock samples indicate that these are having characteristics of either IAT or transitional between MORB and IAT and they have formed in supra-subduction zone tectonic setting. This suggests that there may be significant tectonic differences between Singu Area and Kyaukphyu-Webaung Area.