地质学报2018，Vol.92Issue(4)：704-721,18.
安徽铜陵角闪石堆积岩锆石U-Pb年代学、矿物化学及其对深部岩浆作用的启示
Zircon U-Pb Dating and Mineral Chemistry of the Amphibole Cumulates in Tongling, Anhui Province, and Its Implications for Deep Magmatism
摘要
Abstract
The Tongling region in the Middle-Lower Yangtze River belt has experienced strong magmatic activities in the Late Mesozoic,and frequent interaction of crust and mantle resulted in the formation of large amount of amphibole cumulates or megacrysts.Voluminous study suggests that amphibole cumulates or megacrysts likely resulted from the evolution of the mantle underplated magma in the lower crust magma chamber.In this study,we separated zircons from the amphibole cumulate for the first time and conducted LA ICP-MS U-Pb dating for these zircons and zircons from the host rocks.Dating analysis yielded isotopic ages of 144.67±0.41 Ma (MSWD=0.25) for cumulate and 137.27±0.41 Ma (MSWD=0.25) for host rock.The findings of zircons in the cumulate not only demonstrate the lower crust magmatism in the region but also provide constraint on the time of Mesozoic mantle-derived magma underplating and crust-mantle interaction in the Tongling region.Mineral chemistry analyses indicate that amphiboles are mainly pargasites or magnesiohastingsites,with high contents of Al2 O3 (13.52％ ～13.81％) andTiO2(2.63％～2.98％).The lowCr (1.78×10 6～3.12×10 6),low Ni (21.55×10 6～26.10 × 10 6),and low Mg number (68～69) of the amphibole imply they were not generated by primitive mantle-derived magma.Comprehensive analyses in the study indicate that the magma in the deep lower crust magma chamber might have evolved into basaltic-andesitic magma,with amphibole being the last major crystallization phase.关键词
锆石U-Pb定年/角闪石矿物化学/底侵时代/岩浆作用/铜陵Key words
Zircons U-Pb dating/amphibole mineral chemisty/time of underplating/deep magmatism/Tongling region引用本文复制引用
胡乐,李以科,宋扬,王安建..安徽铜陵角闪石堆积岩锆石U-Pb年代学、矿物化学及其对深部岩浆作用的启示[J].地质学报,2018,92(4):704-721,18.基金项目
本文为国家地质大调查项目(编号:1212011220870和12120114077201)资助的成果. （编号:1212011220870和12120114077201）
