Magma mixing of granites at Lianghe:In-situ zircon analysis for trace elements, U-Pb ages and Hf isotopes  

作　　者：CONG Feng LIN ShiLiang ZOU GuangFu LI ZaiHui XIE Tao PENG ZhiMin LIANG Ting 

机构地区：[1]Chengdu Center of China Geological Survey, Chengdu 610081, China [2]State Key Laboratory of Geological Processes and Mineral Resources, China University ofGeosciences, Wuhan 430074, China

出　　处：《Science China Earth Sciences》2011年第9期1346-1359,共14页中国科学（地球科学英文版）

基　　金：supported by China Geological Survey (Grant No. 1212010784007)

摘　　要：In this paper, we report an integrated study of trace element, U-Pb age and Hf isotopic composition of zircons from alkali feldspar granites, granodiorites and diorite enclaves in a recently discovered ring complex at Lianghe in western Yunnan, Chi na. The granitoids showed identical U-Pb ages of 127, 115 and 122 Ma, from felsic to mafic, but had different zircon trace el ements and Hf isotopic compositions. Trace element content decreased with a gradual increase in εHf(t) values of ?9.1 to ?5.4, ?4.5 to 0, and 3.6 to 6.2, respectively. Results indicate that changes in zircon trace elements generally correlate with changes in Hf isotope signatures within single samples and among various granitoids. These relationships reflect the mixing of felsic and mafic magmas. Evidence indicates that depleted mantle-derived mafic magma underplating caused ancient crustal melting, and then formed large-scale granites in Lianghe during the Early Cretaceous. These granodiorites were formed mainly by the mix ing of mafic magma and granitic magma.In this paper, we report an integrated study of trace element, U-Pb age and Hf isotopic composition of zircons from alkali feldspar granites, granodiorites and diorite enclaves in a recently discovered ring complex at Lianghe in western Yunnan, China. The granitoids showed identical U-Pb ages of 127, 115 and 122 Ma, from felsic to mafic, but had different zircon trace elements and Hf isotopic compositions. Trace element content decreased with a gradual increase in εHf（t） values of -9.1 to -5.4, -4.5 to 0, and 3.6 to 6.2, respectively. Results indicate that changes in zircon trace elements generally correlate with changes in Hf isotope signatures within single samples and among various granitoids. These relationships reflect the mixing of felsic and mafic magmas. Evidence indicates that depleted mantle-derived mafic magma underplating caused ancient crustal melting, and then formed large-scale granites in Lianghe during the Early Cretaceous. These granodiorites were formed mainly by the mixing of mafic magma and granitic magma.

关 键 词：Lianghe ZIRCON trace element U-Pb age Hf isotope magma mixing 

分 类 号：P588.1[天文地球—岩石学] P597.2[天文地球—地质学]