Petrogenesis of keratophyes in the Pingshui Group,Zhejiang:Constraints from zircon U-Pb ages and Hf isotopes  

作　　者：CHEN ZhiHong XING GuangFu GUO KunYi DONG YongGuan CHEN Rong ZENG Yong LI LongMing HE ZhengYu ZHAO Ling 

机构地区：[1]Nanjing Institute of Geology and Mineral Resources, Nanjing 210016, China [2]Department of Earth Sciences, Nanjing University, Nanjing 210093, China

出　　处：《Chinese Science Bulletin》2009年第9期1570-1578,共9页

基　　金：Supported by China Geological Survey (Grant No. 1212010610611);the Ministry of Land and Resources (Grant No. 200811015)

摘　　要：Zircon LA-ICP-MS U-Pb ages and Hf isotopic as well as whole-rock geochemical data are reported for keratophyes in the Pingshui Group, Zhejiang. The results are used to discuss their petrogenesis and geological significance. The keratophyes were dated at 904±8 to 906±10 Ma. These intermediate-felsic rocks are characterized by high LREE contents and depletion of HREE and HFSE (e.g., Nb, Ta, Ti, P), resembling arc-derived rocks. The keratophyes exhibit positive εHf(t) values of 8.6 to 15.4, consistent with their εNd(t) values of 6.4 to 7.9 but far away from those of crust-derived rocks. Such features indi-cate that they were likely originated from prompt reworking of juvenile crust by arc-continent collision during the early-Neoproterozoic assembly between the Cathaysia and Yangtze Blocks. Combining with their Hf model ages, we suggest that there may exist not only remarkable growth of juvenile crust at ca.1.3―1.1 Ga but also production of juvenile arc-derived crust along the southeastern margin of the Yangtze Block (e.g., the Pingshui area) at ca.1.0―0.9 Ga.Zircon LA-ICP-MS U-Pb ages and Hf isotopic as well as whole-rock geochemical data are reported for keratophyes in the Pingshui Group, Zhejiang. The results are used to discuss their petrogenesis and geological significance. The keratophyes were dated at 904±8 to 906±10 Ma. These intermediate-felsic rocks are characterized by high LREE contents and depletion of HREE and HFSE （e.g., Nb, Ta, Ti, P）, resembling arc-derived rocks. The keratophyes exhibit positive εHt（t） values of 8.6 to 15.4, consistent with their εNd（t） values of 6.4 to 7.9 but far away from those of crust-derived rocks. Such features indicate that they were likely originated from prompt reworking of juvenile crust by arc-continent collision during the early-Neoproterozoic assembly between the Cathaysia and Yangtze Blocks. Combining with their Hf model ages, we suggest that there may exist not only remarkable growth of juvenile crust at ca.1.3-1.1 Ga but also production of juvenile arc-derived crust along the southeastern margin of the Yangtze Block （e.g., the Pingshui area） at ca.1.0-0.9 Ga.

关 键 词：铪同位素 模式年龄 锆石 浙江 Pb 水 稀土含量 高场强元素 

分 类 号：P618.510.4[天文地球—矿床学] O614.413[天文地球—地质学]