摘要：Tonnge basalt is a relatively small basaltic field situated in the Tigyaing Township, Sagaing Region, Myanmar. This basaltic field is considered as one of the occurrences of younger extrusive rocks along the major strike-slip fault of central Myanmar. The basaltic lava flows erupted and rested upon the Upper Miocene-Pliocene Irrawaddy Sandstone. Petrological and geochemical studies of the Tonnge basalts have not been carried out yet. This paper reports the results of petrological and geochemical investigation on the basalts from Tonnge area. These data have provided insight into the origin and petrogenetic processes during evolution. The petrographic characteristics of the basalts have been studied using polarizing microscope. The major- and trace-element compositions of basalt samples were analyzed using X-Ray Fluorescence. The Tonnge basalts are porphyritic, holocrystalline and consist of phenocrysts of olivine, plagioclase ± clinopyroxene which are set in the fine-grained intergranular groundmass of olivine, pyroxene, and opaque minerals. The basalts show typical characters of alkali olivine basalts. Trace element assemblage of the studied basalts plots on various discrimination diagrams as within-plate basalt erupted in the continental setting. A relatively small volume, monogenetic nature and unique geochemical characteristics of the basaltic lavas suggest that they are derived from a single, short-lived, discrete parental magma as a result of partial melting.
