A review of the geological characteristics and geodynamic setting of the late Early Cretaceous molybdenum deposits in the East Qinling-Dabie molybdenum belt, East China

摘要

The East Qinling Dabie molybdenum belt, which is located in the nearly east-west trending Qinling-Dabie orogen, East China, is the largest Mo belt in the world and is characterized by extensive Mesozoic mineralization. Although the late Early Cretaceous (ca. 120-100 Ma) is the latest stage of the Mo mineralization in the East Qinling Dabie Mo belt, this period shows relatively intensive Mo mineralization, such as the world-class Shapinggou Mo deposit. All of the late Early Cretaceous Mo deposits are closely related to granitic magmatism, some of which are typical porphyry-type deposits (e.g., Donggou, Tangjiaping, Shapinggou). Homogenization temperatures of fluid inclusions in the late Early Cretaceous Mo deposits range from 115 to 550 degrees C, with salinities ranging from 0.02 to 62.1 wt.% NaCl equivalent. Different amount of CO2 have been recognized in the hydrothermal systems of these Mo deposits, indicating H2O-NaCl-CO2 systems. The ore-forming fluids in these Mo deposits were magmatic water mixed with different amount of meteoric water. Except the Donggou deposit, the delta S-34 values of sulfides from the late Early Cretaceous Mo deposits have a narrow range of 0.4-6.3%0, suggesting a deep magmatic source for the sulfur. The Donggou Mo deposit has slightly higher delta S-34 values (7.5-9.4%o), reflecting that the ore sulfur was mainly derived from magma, probably with some upper crust materials. Available isotopic data show that the ore-associated magmas of the late Early Cretaceous Mo deposits were mainly derived from crustal materials, probably with some contribution of mantle or newly added crust. The Donggou, Tangjiaping, and Shapinggou Mo deposits are genetically related to A-type magmatism, suggesting that they formed in an extensional setting. The late Early Cretaceous Mo deposits in the East Qinling Dabie Mo belt formed in an intraplate extensional setting accompanied by the lithospheric thinning and asthenospheric upwelling. (C) 2015 Elsevier Ltd. All rights reserved.