The Molybdenite Re-Os Isotopic Dating of the Kekesala Fe-Cu Deposit in West Tianshan, Xinjiang and Its Geologic Significance

As a typical skarn-type deposit in the Boluokenu polymetallic belt, West Tianshan, Xinjiang, the Kekesala Fe-Cu deposit was occurred at the contact zone between the Husite intermediate-acid intrusions and Upper Ordovician carbonate. Inrecent years, the chronological studies indicate that the diagenetic age of intermediate-acid intrusive rocks from this deposit are concentrated on Late Devonian.However, the metallogenic age of molybdenite is Early Permian, which varies in wide range. This paper has collected molybdenum samples from the surface trenches of this deposit to determine its metallogenic age.The results suggest that the Re-Os isotopic isochron age is (290±10)Ma, and its weighted average age is (287.8±0.9)Ma, corresponding to Early Permian. The metallogenic age of molybdenite is significantly different from the diagenetic age of intermediate-acid intrusive rocks, indicating two periods of magmatic or magmatic hydrothermal events in this studying area. The Kekesala skarn-type Fe-Cu deposit may be related to the contact metasomatism of the early stage (Late Devonian)intermediate-acid magma intruded into the limestone formation; the late stage (Early Permian) Cu-Mo deposit was formed by the tectonic-magmatic hydrothermal effect occurred along with the fault, which was superimposed on the early stage skarn-type deposit.