Genetic connection of Pb- Ag- Au polymetallic deposit in the Chuxiong basin, central Yunnan Province: evidence from trace elements and S isotope of metallic minerals
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    Abstract:

    The Laojiezi Pb- Ag and the Baimaju Au (Cu) are typical polymetallic deposits which are associated with the Himalayan stage alkali- rich porphyry in the Chuxiong basin, central Yunnan province. However, the unclear origin connection and metallogenic model between the two deposits have become the key problems limiting the theoretical knowledge of the deposit and the achievement of the polymetallic metallogenic model in the Yaoan alkali- rich porphyry area. In this paper, the trace elements of pyrite and specularite and S isotope of pyrite, galena and molybdenite in different types of rock and ore were systematically studied. The results show that: ① the sources of Pb, Ag, Au, Cu and Mo polymetallic metallogenic materials in the Yaoan alkali- rich porphyry area are related to syenitic magma derived from deep crust- mantle interaction; ② the characteristics of REE and trace elements in pyrite indicated that the ore- forming fluid was Cl- enriched. In addition, the Pb, Ag, Cu, Mo polymetallic ore- forming fluid in the Laojiezi deposit and the early stage Ⅰ fluid in the Baimaju deposit were mainly derived from the magmatic fluid separated during the diagenesis of syenite porphyry. However, the ore- forming fluid of Laojiezi specularite and the early stage Ⅰ fluid in the Baimaju deposit were complex and may have been a mixture of magmatic fluid and meteoric fluid rich in δ34S and probably also mixed with some metallogenic materials in the strata during the mineralization process of migration and precipitation; and ③ this study also shows that, compared to the early mineralization stage in the Baimaju deposit, the Pb, Ag, Cu, Mo polymetallic mineralization stage in the Laojiezi deposit and the later mineralization stage in the Baimaju deposit should have occurred in an environment of relatively high fO2 and low temperature. Furthermore, a synthetically comparative study (such as geology, rock, orebody, source of metallogenic materials, etc.) in the two deposits, shown that the Pb, Ag, Au, Cu, Mo polymetals in the Yaoan alkali- rich porphyry area were genetically related, controlled by the same magmatism and were the product of different parts of the same geological tectonic environment and rock formations. These two deposits had a “temporal- spatial- material- evolution” genetic connection. Based on the metallogenic correlation studies of Laojiezi Pb- Ag deposit and Baimaju Au (Cu) deposit, a Pb- Ag- Au polymetallic mineralization model in the Yaoan alkali- rich porphyry region was constructed. Through the above research, we believe that these two deposits and their deep parts jointly constitute an epithermal- porphyry type Pb- Ag- Au (Cu- Mo) polymetallic mineralization system.

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Yang Hang, Wu Peng, Zhang Yan, Han Runsheng, Jiang Longyan, Jiang Xiaojun, Guan Shenjin.2021. Genetic connection of Pb- Ag- Au polymetallic deposit in the Chuxiong basin, central Yunnan Province: evidence from trace elements and S isotope of metallic minerals[J]. Acta Geologica Sinica,95(12):3799-3819

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History
  • Received:August 01,2020
  • Revised:December 19,2020
  • Adopted:March 08,2021
  • Online: March 18,2021
  • Published: