Objective The Qingshuihe Donggou porphyry molybdenum deposit is one of the representative porphyry deposits in the East Kunlun metallogenic belt.
Methods Therefore, a detailed study of the age, genesis and tectonic environment of the porphyry intrusions in the Qingshuihe Donggou deposit is needed to improve the understanding of the metallogenic regularity of this area. In this paper, zircon U−Pb dating, petrogeochemistry and zircon Hf isotope of the porphyries from the Qingshuihe Donggou deposit, which are closely related to the Mo mineralization, have been studied.
Results The zircon U−Pb age of granodiorite porphyry is 226.9 ± 1.3 Ma (MSWD = 1.03, n = 18), and the zircon U−Pb age of diorite porphyry is 224.3 ± 1.2 Ma (MSWD = 0.47, n = 15), These results indicate that this deposit formed at 226.9~224.3 Ma. Granodiorite porphyry, diorite porphyry and granite porphyry are rich in Si, Na, K and Al, poor in Ti and Mg, and show a right−leaning partition pattern characterized by the light rare earth element enrichment. The former two granites have no obvious Eu depletion (δEu: 0.79~0.98), whereas granite porphyry displays noticeable Eu depletion (δEu: 0.22~0.24). All of them are enriched in large ion lithophile elements (e.g., Rb, K, Ba), and depleted in high field strength elements (e.g., Ta, Nb, Ti, P), belonging to the metalluminous to weak peraluminous high K calc−alkaline granites. The 176Hf/177Hf ratio of zircon from these porphyry rocks ranges from 0.282510 to 0.282652, the εHf(t) value ranges from −4.5 to 0.2, and the two−stage model age ranges from 1541 Ma to 1240 Ma.
Conclusions Based on the characteristics of regional tectonic evolution, it is deduced that these porphyries formed by partial melting of the Middle Proterozoic Jinshuikou Group under the Late Triassic post−collisional extension environment, and experienced magma mixing by mantle−derived materials.
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