Micro-sample Rb-Sr analysis using the microsampling technique and its applications on geochronology and petrogenesis

This study presents analytical data of Rb-Sr isotopic composition of K-feldspar megacrysts from the Mesozoic Heyu granite pluton exposed in the eastern Qinling orogenic belt,by using the micro-drilling technique and the micro-sample Rb-Sr isotopic analytical method.Analytical results show significant variations in Rb/Sr ratio and Sr isotopic composition within a single K-feldspar crystal.Rb-Sr isochron ages of about 132 Ma to 133 Ma can be obtained from both megacryst and matrix K-feldspars.No significant variations of ~(87)Sr/~(86)Sr initial ratio can be detected in the centre and marginal parts of K-feldspar crystals,suggesting homogeneous Sr isotopic composition during the crystallization of the magma and implying primary origin for the K-feldspar megacrysts of the Heyu granite.Owing the feature of high spatial resolution,a combination of the micro-drilling technique and the micro-sample Rb-Sr isotopic analytical method increases the applications in studies on isotopic geochronology and petrogenesis of metamorphic and plutonic rocks as well as volcanic rocks.