Earth Science Frontiers ›› 2018, Vol. 25 ›› Issue (2): 280-298.DOI: 10.13745/j.esf.yx.2017-12-24

Previous Articles     Next Articles

The Cihai FeCo deposit, Xinjiang: a superimposed hydrothermal mineralization of two mantlederived magmatic series.

WANG Yuwang,SHI Yu,TANG Pingzhi,LI Dedong,WANG Jingbin,XIE Hongjing   

  1. 1. Beijing Institute of Geology for Mineral Resources, Beijing 100012, China
    2. China Nonferrous Metals Resource Geological Survey, Beijing 100012, China
  • Received:2016-12-27 Revised:2017-05-12 Online:2018-03-15 Published:2018-03-15

Abstract:  The Cihai deposit in the Eastern Xinjiang is best known for its special Fe-Co metal assemblage. In this paper, we studied the chronology and geochemistry of maficultramafic rocks, geological characteristics of the symbiotic Co mineral and chemical composition of pyrite at the Cihai ore district, and concluded that the Cihai deposit was a superimposed magmatic hydrothermal deposit of two mantlederived magmatic series, i.e. Cu-Ni and Ti-Fe series. The Cu-Ni series produces plutonic rocks including olivine gabbro, troctolite, gabbro and hornblende gabbro with a zircon U-Pb age of 279.1±1.4 Ma for the gabbros. The rocks of Cu-Ni series have high m/f ratio (mostly higher than 1.5), contain high levels of Co, Ni and Cu, and host Cu-NiCo sulfide mineralized bodies, suggesting their proximity to Co source of the deposit. The Ti-Fe series produces extrusive and hypabyssal rocks including basalt and diabase, and yields a zircon U-Pb age of 276.2±2.2 Ma for basalt. The rocks of TiFe series have low m/f ratio (mostly lower than 1.5), contain low percentage of Ni and Cu but rich in TiO2, and host magnetite ore bodies, all indicating the series is close to Fe source of the deposit. The geological characteristics of orebody and ore suggest that the formation of the main magnetiteCo orebodies were controlled by hydrothermal mineralization, and the deposit may belong to a hydrothermal deposit related basicultrabasic magma. The occurrence and chemical composition of different pyrite types further reveal that the Co mineralization happened after magnetite mineralization, and that the metasomatism of pyrite by volcanicsubvolcanic hydrothermal mineralization formed the Cobearing pyrite and other cobalt minerals. In other words, Fe and Co deposits display complex mineralization from two sources and in two stagesthey are essentially the superposition of CuNi and Ti-Fe magma series.

Key words: Cihai, Xinjiang, FeCo deposit, metallogenic superimposition, Cobearing pyrite, maficultramafic rocks, magmatic series

CLC Number: