Felsic Xenoliths in Corundum-related Basalt at Khao Lun Tom, Bo Phloi District, Kanchanaburi Province, Western Thailand

Abstract

Felsic xenoliths found within an area of Cenozoic alkali basalt related to corundum deposit in Bo Phloi district, Kanchanaburi province, western Thailand, were collected for this study. Petrography, mineral chemistry and whole-rock geochemistry were carried out and aimed to find relationship with corundum formation. Based on petrographic description, alkali feldspar, plagioclase and quartz are significantly essential minerals whereas accessory minerals are composed of biotite, zircon, apatite and ilmenite. Porphyritic and poikilitic textures are clearly distinguished as primary texture, particularly in feldspar grains; besides, quenched texture and reaction product induced by basaltic magma usually present around edges of these feldspars. Whole-rock geochemistry also yields similar result with slight variation in composition. These xenoliths can be classified, based on petrochemical data, as granite to syenite. Alumina saturations of all xenolith samples are classed as peraluminous series which normative corundum present sometimes in these samples. Essential minerals of these felsic xenoliths have similar chemical compositions. Feldspar compositions, in particular, are equivalent to about 700-800ºC of equilibrated temperature, estimated at a pressure of 5 Kbar, and they seem to have been heated up to over 1000ºC by basaltic magma. In conclusion, these felsic xenoliths appear to have originated in high aluminous igneous provenances in which differentiation processes had been taken place before picking up and transportation to the surface via basaltic eruption. Although, corundum has potential to crystallize within some of these xenoliths, corundum crystal has never been found during this study. However, more samples should be collected for further investigation.