地质通报Issue(8)：1438-1446,9.
祁连山西段新元古代晚期花岗质片麻岩成因及LA-ICP-MS锆石U-Pb定年
Petrogenesis and LA-ICP-MS zircon U-Pb dating of Late Neoproterozoic granitic gneisses in western Qilian Mountain
摘要
Abstract
Neoproterozoic granitic gneisses from the Diaodaban area of the western Qilian Mountain outcrop in two-mica gneiss of the Beidahei Group. The granitic gneisses are mainly alkaline and peraluminous, with A/CNK values of 1.04~1.12. Their low Rb values and high Sr and Ba values as well as K/Rb ratios of 179~225 show that the rocks are not highly fractionated granite;nev⁃ertheless, the rocks have obvious negative Eu anomaly (Eu/Eu∗=0.25~0.35), indicating that the magma experienced weak fraction⁃ation crystallization. The diagram of (Al2O3+TFeO+MgO+TiO2)-Al2O3/(TFeO+MgO+TiO2) suggests that the protolith of the rocks was sourced from graywacke or mafic-intermediate igneous rocks. Samples are enriched in incompatible elements and have geochemical characteristics of the intraplate granite in Y-Nb and (Y+Nb)-Rb diagrams. LA-ICP-MS zircon U-Pb dating of the granitic rocks yielded a weighted mean age of 736 ± 5Ma, suggesting that there is a magmatic record of 750~730Ma in the Qilian Mountain, probably resulting from intraplate extension in the late Neoproterozoic. The Neoproterozoic magmatic activities in the Qilian Mountain recorded a long-term evolution history from early Neoproterozoic convergence through Late Neoproterozoic ex⁃tension to breakup.关键词
LA-ICP-MS锆石U-Pb年龄/花岗质片麻岩/新元古代/祁连山西段Key words
LA-ICP-MS zircon U-Pb ages/granitic gneisses/Neoproterozoic/western Qilian Mountain分类
天文与地球科学引用本文复制引用
李猛,王超,李荣社,彭岩..祁连山西段新元古代晚期花岗质片麻岩成因及LA-ICP-MS锆石U-Pb定年[J].地质通报,2015,(8):1438-1446,9.基金项目
中国地质调查局项目(编号1212010610102)、中国地质调查局百名青年地质英才计划和陕西省科技计划项目 （编号1212010610102）
