DOI:10.19762/j.cnki.dizhixuebao.2020256
 
Geochronological and geochemical characteristics of the metamorphic basic rocks and their tectonic implications in the Longquan area, Zhejiang Province
Author NameAffiliationE-mail
LIU Yuandong 1) Zhejiang Institute of Geological Survey, Hangzhou, 311203 lyd661106@163.com 
LIU Fenglong 1) Zhejiang Institute of Geological Survey, Hangzhou, 311203  
ZHANG Jianfang 1) Zhejiang Institute of Geological Survey, Hangzhou, 311203  
LI Xiang 1) Zhejiang Institute of Geological Survey, Hangzhou, 311203  
XU Lei 1) Zhejiang Institute of Geological Survey, Hangzhou, 311203  
WEN Xubin 2) Zhejiang Province Industrial EP Design & Research Institute Co. Ltd, Hangzhou, 311203  
NI Weiwei 1) Zhejiang Institute of Geological Survey, Hangzhou, 311203  
Abstract:The formation age, diagenetic, and tectonic attributes of a set of medium- deep metamorphic rock series exposed in the Longquan area, southwestern Zhejiang Province, an important component of the Cathaysian massif, remains controversial. Based on petrogeochemical studies of the metabasites from the Longqun metamorphic rocks, the diagenetic tectonic environments of these rocks can be divided into at least two types. Type Ⅰ rocks have the same REE distribution curves and spider diagram of trace element with IAB. The trace element ratio and discrimination diagrams indicate that these rocks were formed in an island arc setting which was related to subduction. Type Ⅱ rocks have the same REE distribution curves and spider diagram of trace element with OIB. The trace element ratio and discrimination diagrams indicate that these rocks were formed in a within- plate tectonic environment which were not relevant to the subduction. The rocks symbiosis of different tectonic attributes proves that the original Longquan Group is a subduction accretion complex. The zircon U- Pb dating of metabasites yielded the peak metamorphic ages between 404~402 Ma. This provides new data for reevaluatingthe tectonic attributes of the Lishui- Yuyao fault zone, the establishment of the regional tectonic framework, and the further analysis of the material composition and structure of the Cathaysian orogenic system.
keywords:metabasites  geochemistry  subduction- accretion complex  Early Paleozoic  Longquan
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