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Geoscience ›› 2020, Vol. 34 ›› Issue (06): 1261-1276.DOI: 10.19657/j.geoscience.1000-8527.2020.072

• Petrology • Previous Articles     Next Articles

Igneous Assemblage and Metallogenic Background of the Mawu Gold Deposit in the Min-Li Ore Belt of the Western Qinling Orogen

GUO Na1(), LIU Cui2, CUI Long1, YAO Wei1, LI Guoying1, GAN Liming1, HUANG Yong3   

  1. 1. Xi’an Center of Mineral Resources Survey, China Geological Survey, Xi’an, Shaanxi 710100, China
    2. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China
    3. Civil Military Center of Geological Survey, China Geological Survey, Chengdu, Sichuan 611732, China
  • Received:2018-10-26 Revised:2019-06-10 Online:2020-12-22 Published:2020-12-22

Abstract:

The Mawu gold deposit in Gansu Province is a medium-sized finely-disseminated gold deposit, which is located in the eastern part of the Min-Li ore belt in the Western Qinling Orogen, and in the exocontact of the Zhongchuan intrusion. A series of analyses on the fieldwork geology, petrology, geochronology, and geochemistry of the igneous rocks from the mining area were carried out to reveal the ore-causative igneous rock assemblages and their characteristics, and to explore their petrogenetic and geotectonic background as well as gold ore formation. Field observations indicate that the lamprophyre dikes/veins, aplitic dikes, and quartz diorite dikes were developed near or crosscut the gold veins, indicating that the gold ores and magmatic dikes were nearly coeval. LA-MC-ICP-MS zircon U-Pb dating of the lamprophyre and granitic dikes indicates that they were formed at about (153.5±3.5) Ma to (154.9±0.9) Ma, suggesting a Late Jurassic gold mineralization. Therefore, the work concludes that the igneous assemblage of Mawu gold deposit are dominated by dikes. The dikes have a wide composition range of SiO2, K2O, Na2O, TFeO and MgO, belonging to different igneous types and likely derived from different magma sources. The occurrence of wide spectrum dike swarm (WSDS) means that it was formed under an extensional environment caused by lithospheric delamination of the orogen. The dikes and gold orebodies intruded into the Zhongchuan granitic rocks and other wall-rocks, which indicates that they were formed after large-scale magmatic activities and batholith uplift in the late Western Qinling orogeny, and belongs to post-batholith metallogeny.

Key words: Gansu Province, Mawu gold deposit, wide spectrum dike swarm, igneous assemblage, post-batholith metallogeny, Late Jurassic

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