The Early Paleozoic Tectonic Framework and Evolution of Northern West Qinling Orogen: By Zircon U-Pb Dating and Geochemistry of Rocks from Tianshui and Sunjiaxia

The Tianshui-Sunjiaxia area is located in the connection zone of West Qinling Orogen and North Qilian Orogen, which could provide great insights into amalgamation processes between northern southern blocks China. Three subduction- rift-related rocks gneissic granite from arc-interarc belt (NQAI) metabasalt back-arc basin (NQBA) are distinguished across zone. was generated by melts older crustal materials Longshan Group with addition a relatively juvenile basaltic source lower crust during collision process. Liwanxincun reflects mixing partial melting shallow asthenospheric mantle metasomatized extension setting. LA-ICP-MS zircon U-Pb dating (068, 069) yields crystallization ages 457.0 ± 1.6 Ma 445.9 2.1 Ma. study divided six tectonic units Early Paleozoic time involving NQAI (Yanjiadian-Xinjie) continental arc, interarc rift (Maojiamo-Xiwali), arc (Chenjiahe-Wangjiacha); NQBA (Huluhe-Hongtubao), island ophiolitic melange (North Qinling-Shangdan). A model proposed might represent early period subduction Ocean (NQO) product triggered southward NQO. ongoing NQO then leads to formation Chenjiahe-Wangjiacha as well Hongtubao spreading ridge (Huluhe). evolution closely associated closure Qinling-Shangdan context convergence process micro-continental blocks, including China block, group Terrane.