地质学报2018，Vol.92Issue(5)：946-963,18.
政和-大埔断裂带内变基性岩成因及构造属性研究
Petrogenesis and Tectonic Attribute of Metabasite Rocks in the Zhenghe-Dapu Fault Zone
摘要
Abstract
The NE-SW trending Zhenghe-Dapu fault zone is an important fault belt in the Cathaysia block,within which metabasite rocks are extensively exposed.The study focused on zircon U-Pb geochronology and geochemical analysis of the metabasite rocks along the Zhenghe-Dapu fault zone from Zhenghe County to Jianou County,to clarify the petrogenesis and the tectonic attributes of the metabasite rocks,and to explore tectonic evolution of Cathaysia block during the late Neoproterozoic period.Zircon U-Pb dating yields 807±4 Ma and 812±7 Ma for protolith of hornblende plagioclase schists and rhyolite of the bimodal volcanic rock eruption age,respectively,suggesting that the protolith of plagioclase amphibolite schists Zhenghe County should have formed at 725±22 Ma.Geochemical analysis shows that the amphibolite schists of Dikou Town are significant enrichment in LILEs and LREEs and depletion in HFSEs,with a slight positive Eu anomaly (δEu =0.98 ～ 1.09),low initial 87 Sr/86 Sr ratios ranging from 0.685523 ～0.707149,and negative εNd(t) values of-1.2～-1.0.The tectonic discrimination diagram suggests that the amphibolite schists belong to intraplate basalt.The plagioclase amphibolite schists from Zhenghe County exhibit flat REE patterns,with LREE/HREE=1.77～2.08,(La)N/(Yb)N =0.99～1.30,(La)N/(Sm)N=0.88～1.17 and slight positive Eu anomalies (δEu=1.05～1.14),sharing the characteristic of NMORB.The plagioclase amphibolite schists have low initial 87Sr/86 Sr ratios ranging from 0.698279 ～0.701964 and εNd(t) values of +3.8 to +4.3,indicating the magma originated from relatively depleted mantle source.Both protolith forming age of the amphibolite schists from Dikou Town and the bimodal volcanic rock of Shuiji Town are roughly the same.The dated age of ca.810 Ma bimodal volcanic rock constrain the initial time of the rifting during the late Neoproterozoic of Cathaysia block.The protolith of the plagioclase amphibolite schists may be derived from the asthenospheric mantle upwelling,indicating that Neoproterozoic rifting may continue to ca.725 Ma.关键词
镁铁质火山岩/构造演化/地球化学/新元古代裂谷/华夏板块/Sr-Nd同位素Key words
mafic volcanic rocks/tectonic evolution/geochemistry/Neoproterozoic rift/Cathaysia block/Sr-Nd isotopes引用本文复制引用
贺健,李龙明,林寿发,邢光福,姜杨,任升莲,李加好,冯腊梅,葛延鹏..政和-大埔断裂带内变基性岩成因及构造属性研究[J].地质学报,2018,92(5):946-963,18.基金项目
本文为国家自然科学基金项目(编号41573023)资助成果. （编号41573023）
