Geological Characteristics and Re-Os Dating of the Chaganhua Molybdenum Deposit in Urad Rear Banner,Western Inner Mongolia

The Changanhua molybdenum deposit,a concealed porphyry molybdenum deposit newly discovered in western Inner Mongolia,contains large quantities of molybdenum resources.This ore deposit is characterized by disseminated,lumpy and veinlet molybdenite mineralizations hosted in the northeastern contact zone between medium-fine grained monzonitic granite and Paleoproterozoic Baoyintu Group.Re-Os isotopic dating of six samples from various ore bodies in the ore deposit yields model ages of(239.3±3.3)～(242.6±3.6)Ma,isochron age of(242.7±3.5)Ma,initial 187Os of-1±3 ng/g,and MSWD of 0.77,indicating that molybdenum mineralization took place in lower Triassic and was related to tectonomagmatic orogenic process in early Indosinian period.The Chaganhua-Chagandeersi granite in the Zongnaishan-Shalazashan structural belt of western Inner Mongolia is considered to be a molybdenum-polymetallic metallogenic area.Characteristics of molybdenum mineralization and ore-prospecting criteria in this area are also summarized in this paper.