Ar-Ar Age of Muscovite from the Greisenization Alteration Zones of the Honghuaerji Tungsten Polymetallic Deposit, Inner Mongolia, and Its Geological Significance

The newly found Honghuaerji tungsten polymetallic deposit is a large scale tungsten deposit in north-east Daxinganling in China.The alteration includes sericitization and greisenization.The metallic minerals are scheelite and molybdenite.These minerals in rock body show the belt characteristics of W in the top and Mo in the bottom.Geological characteristics indicate that it is a high temperature hydrothermal deposit.In order to constrain the timing of hydrothermal activities, Ar-Ar dating of muscovite from the greisenization alteration zones was carried out.The Ar-Ar dating yields an Ar-Ar plateau age of 174.4±1.2 Ma and an isochron age of 173.2±4.3 Ma.Because greisenization alteration zones and the tungsten(molybdenum) mineralization belt are closely related in space, muscovite, scheelite, and molybdenite may have formed simultaneously.Moreover, the Ar-Ar age of muscovite is in agreement with the Re-Os age of molybdenite(176.8±2.2 Ma) within uncertainties, indicating this Ar-Ar age represents the timing of the tungsten and molybdenum hydrothermal mineralization.Combined field geology, U-Pb ages and Re-Os ages indicate this deposit formed the Jurassic period and may be the product of Yanshanian tectonic magmatic activity.