Earth Science Frontiers ›› 2018, Vol. 25 ›› Issue (5): 151-166.DOI: 10.13745/j.esf.yx.2018-3-40

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Study of fluid inclusions and ore genetic type of the Changlingzi deposit, Keshiketeng County, Inner Mongolia

XU Qiangwei,WANG Pin,ZHONG Jun,WANG Chengming,ZHENG Yi,FANG Jing   

  1. 1. School of Earth and Space Sciences, Peking University, Beijing 100871, China
    2. Key Laboratory of Marginal Sea Geology, Chinese Academy of Sciences; South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
    3. Beijing Research Institute of Uranium Geology, Beijing 100029, China
    4. School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China
    5. Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China
  • Received:2018-02-08 Revised:2018-04-11 Online:2018-09-15 Published:2018-09-15

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Abstract: The Changlingzi Pb-Zn deposit in Keshiketeng County, Inner Mongolia, China, was recently discovered in the southern Great Hinggan Range. Ore bodies occur as veins in the Early Permian Dashizhai Formation with skarn alteration. The Early Permian Dashizhai Formation consists of marine intermediate-acid volcanic rocks and spilites interbeded with sandstones and slates. Based on the mineral assemblages and crosscutting relations of vein lets, the mineralization process can be divided into four stages (from early to late): the dry skarn stage, wet skarnmagnetite stage, quartzsulfide stage and quartzcarbonate stage characterized by the mineral assemblages of garnet±diopside±wollastonite, quartz+epidote+tourmaline+magnetite, quartz+pyrite±pyrrhotite±chalcopyrite±galena±sphalerite, and quartz±calcite, respectively. Two types of fluid inclusions (FIs), including aqueous (W-type) and daughter mineral-bearing polyphase (S-type) fluid inclusions, occur in the Changlingzi deposit. And the W-type can be subdivided into the liquid-rich (WL-type) and vapor-rich (WV-type) types. The diopside grains contain S- and WL-type FIs. The epidote and quartz grains of the wet skarnmagnetite stage contain WL-, WV- and S-type FIs. Quartzes of the quartzsulfide stage include all types of FIs. Only WL-type FIs are present in the quartzcarbonate stage quartz±calcite veins. FIs in the diopside were homogenized at 387524 ℃, with salinities ranging from 10.7 to 52 wt.%(NaCleqv.). FIs of the wet skarnmagnetite, quartzsulfides and quartzcarbonate stages attained homogenization temperatures of 312533 ℃, 182329 ℃, 124199 ℃ and salinities of 11.360, 4.738 and  3.122.4 wt.%(NaCleqv.), respectively. The above characteristics of ore geology and ore-forming fluids indicated that the Changlingzi Pb-Zn deposit is a typical skarn-type deposit. The ore-forming fluids experienced an evolutionary transformation from the high-temperature, high-salinity magmatic fluids of the skarn stage to the low-temperature, low-salinity meteoric waters of the quartzcarbonate stage. The occurrence of ebullition in the quartzsulfide stage was recognized as an important mechanism for ore-metals precipitation.

Key words:  fluid inclusions, Changlingzi Pb-Zn deposit, skarn deposit, Great Hinggan Range

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