The LA-ICP-MS zircons U-Pb ages and geochemistry of the Baihua basic igneous complexes in Tianshui area of West Qinling  

作　　者：PEI XianZhi DING SaPing ZHANG GuoWei LIU HuiBin LI ZuoChen LI GaoYang LIU ZhanQing MENG Yong 

机构地区：[1]Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education [2] Faculty of Earth Science and Land Resources, Chang'an University, Xi'an 710054, China Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education [3] Faculty of Earth Science and Land Resources, Chang'an University, Xi'an 710054, China State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi'an 710069, China Key Laboratory of Western China's Mineral Resources and Geological Engineering, Ministry of Education [4] Faculty of Earth Science and Land Resources, Chang'an University, Xi'an 710054, China

出　　处：《Science China Earth Sciences》2007年第z2期264-276,共13页中国科学（地球科学英文版）

基　　金：Supported by the National Natural Science Foundation of China (Grant Nos. 40234041 and 40572121), the Ministry of Education of China (Grant No. 104175) and China Geological Survey (Grant No. 200013000154)

摘　　要：Baihua meta-igneous complex consists mainly of pyroxenite-gabbro(diorite)-diorite-quartz diorite. They form a complete comagmatic evolutionary series. The geochemical characteristics of basic-interme- diate basic igneous rocks indicate that they belong to a tholeiite suite. The REE distribution pattern is nearly flat type and LREE is slightly enriched type, and their primitive mantle-normalized and MORB-normalized trace element spider diagrams are generally similar; the LIL elements (LILE) Cs, Ba, Sr, Th and U are enriched, but Rb, K and the HFSEs Nb, P, Zr, Sm, Ti and Y are relatively depleted. All these show comagmatic evolution and origin characteristics. The tectonics environment discrimination of trace element reveals that these igneous complexes formed in an island-arc setting. The LA-ICP-MS single-zircons U-Pb age of Baihua basic igneous complex is 434.6±1.5 Ma (MSWD = 1.3), which proves that the formation time of the island-arc type magmatite in the northern zone of West Qinling is Late Ordovician or Early Silurian, also reveals that the timing of subduction of paleo-ocean basin represented by the Guanzizhen ophiolite and resulting island-arc-type magmatic activities is probably Middle-Late Ordovician to Early Silurian.

关 键 词：basic IGNEOUS complex  ISLAND-ARC setting  LA-ICP-MS  ZIRCONS U-PB isotopic ages  Tianshui area  West QINLING 

分 类 号：N[自然科学总论]