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Geoscience ›› 2019, Vol. 33 ›› Issue (03): 501-513.DOI: 10.19657/j.geoscience.1000-8527.2019.03.04

• Ore Deposits and Petrology • Previous Articles     Next Articles

Geochemical Characteristics and Tectonic Significance of Ordovician Intrusions in Bayanbulak, Xinjiang,China

LIU Xiang1(), GONG Xiaoping1, LIU Yangyang1, WANG Zhe2, FENG Jun2, LIU Shijie1, HAN Bingjun1, QI Rui1   

  1. 1. College of Geology and Mining Engineering, Xinjiang University,Urumqi,Xinjiang 830047, China
    2. Geological Survey Institute of Xinjiang Uygur Autonomous Region,Urumqi,Xinjiang 830000, China
  • Received:2018-01-11 Revised:2018-12-08 Online:2019-06-23 Published:2019-06-24
  • Contact: GONG Xiaoping

Abstract:

The Bayinbuluk area is located in the multi-stage composite continental arc in the Middle Tianshan Complex. Our study found that the Ordovician intrusions include mainly quartz diorite, granodiorite and monzogranite. Zircon U-Pb dating yielded Middle Ordovician ages (462.7±6.2 Ma, 463.4±2.8 Ma, 471.5±5.9 Ma) intrusions, and geochemical analysis shows metaluminous and calc-alkaline affinities. Chondrite-normalized REE patterns show clear right-inclining pattern and negative Eu anomalies. Trace element analysis results show large ion lithophile element (LILE) enrichments and high field strength element (HFSE) depletions. Geochemical characteristics indicate that the intrusions were formed in a subduction-collisional setting, and the magma may have been derived from a crust-mantle mixed source. Comprehensive analysis suggests that the South Tianshan ocean basin started to subduct northward in the early Middle Ordovician, which may have been related to the regional dextral movement. Magmatism in the Middle Tianshan shows a gradual eastward migration and expansion.

Key words: Bayinbuluk area, intrusion, Ordovician, crust-mantle mixed source, South Tianshan ocean basin

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