GEOCHRONOLOGY AND GEOCHEMISTRY OF SINGLE-GRAIN ZIRCONS: SIMULTANEOUS IN-SITU ANALYSIS OF U-PB AGE AND TRACE ELEMENTS BY LAM-ICP-MS

Abstract

Simultaneous in-situ analysis of U-Pb age and 26 trace elements for single-grain zircon using the LAM-ICPMS technique was successfully achieved in this study. The precision of analysis is 1 to 3 % for 207Pb/206Pb isotopic ratios, 2 and 8 % for 206Pb/238U ratios and 5 to 15% for most of the other trace elements. The concordia U-Pb and the mean 206Pb/238U ages for zircon grain of 1800 Ma to 150 Ma by LAM-ICP-MS spot analysis are in good agreement within analytical errors with the TIMS and SHRIMP results. All zircon grains are uniquely LREE-depleted in chondrite-normalized REE patterns. Zircon formed in mantle-derived magmas is significantly different from that of granitoids with regard to contents of many trace elements (i.e., U, Th, ΣREE, Y, Nb and P) and REE patterns (i.e., Nd/Yb ratio and Ce and Eu anomalies). This combined geochronological and geochemical investigation provides valuable information on timing and genesis of zircon.