Micro-sample Rb-Sr analysis using the microsampling technique and its applications on geochronology and petrogenesis
微区-微量样品Rb-Sr同位素分析技术及其应用前景

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 87Sr/86Sr 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.