Abstract:

Qibaoshan polymetallic deposit is a rare skarn intergrowthtype deposit that the Ca-skarn and Mg-skarn types occur together in the same deposit but different locations. The polymetallic deposit is located in the contact zone between Indosinian-Early Yanshanian porphyritic granite and carbonate beds of the mid-upper series of Carboniferous. Mineralization of the deposit can be divided into two periods. The early period is characterized by the formation of Ca-Mg skarn and magnetite, and  the late period is characterized by multi-polymetallic sulfide mineralization. The ore composition of the deposit is complicated. Besides Cu, Pb, Zn, elements such as Ga, Ge, In, Cd, Au, Ag, Te, Fe also can be utilized. The results of isotopic geochemical analysis show that the porphyritic granite is the product of assimilation and hybridization of mantle-origin magma and upper crust material. Ore-forming fluid is mainly magmatic water while ore-forming material mainly comes from magma. Metal particles transport in the magmatic water in the form of chlorine complexes, and precipitate due to chemical reaction after the formation of skarn. Geologic and geochemical evidences suggest that porphyritic granite is the parent rock of mineralization. The chemical property of wall rock determines the type of skarnization. The Qibaoshan polymetallic deposit is not only special in genesis, but also is of  great economic industrial value, and it should be researched further.

Key words: Qibaoshan, Ca-skarn, Mg-skarn, intergrowth-type, polymetallic deposit, Hunan Province