Geologicial Feature and Chronology Study of Kangxiwar Beryl-Bearing Muscovite Pegmatite in Weste Kunlun Orogen, Xinjiang

The Kangxiwar-Dahongliutan pegmatite field is an important area with abundant LCT family rare-metal pegmatites in the West Kunlun Orogen. The Kangxiwar beryl-bearing muscovite pegmatite and Dahongliutan spodumene pegmatites are the representative beryllium deposit and lithium deposit, respectively in this pegmatite field. Previous studies were focused on the Dahongliutan granitic pluton and lithium deposits that were formed at 220~210Ma in the Dahongliutan area. Nevertheless, there are few studies on the Kangxiwar pegmatite. Based on the field observation, this study summarizes geological features of the Kangxiwar beryl-bearing muscovite pegmatite and presents the latest zircon U-Pb dating results. According to our dating results, the crystallization age of the Kangxiwar beryl-bearing muscovite pegmatite is (209±4.4)Ma, which is consistent with the ages of the Dahongliutan spodumene pegmatite and Dahongliutan granitic pluton, indicating that theberyl-bearing muscovite pegmatite, spodumene pegmatites and granite were likely the products of the same magmatic event. In addition, the zircon from the Kangxiwar pegmatite also has recorded a hydrothermal event around 200Ma and a metamorphic event at~160Ma. Based on muscovite ⁴⁰Ar-³⁹Ar dating, previous studies suggested that the age of the Kangxiwar pegmatite is 185~156 Ma. The reported ⁴⁰Ar-³⁹Ar age is significantly younger than the crystallization ages of the beryl-bearing muscovite pegmatite, granitic pluton and spodumene pegmatites that had been obtained using U-Pb dating of zircon, cassiterite and columbite, but it is comparable to the age of the metamorphic zircon in this study, which suggested that the muscovite ⁴⁰Ar-³⁹Ar isotope system of the Kangxiwar pegmatite underwent thermal disturbance due to the metamorphic event in the Kangxiwar-Dahongliutan pegmatite field.