Geological Characteristics And Genesis Of The Wucfaoling Molybdenum Deposit, Heilongjiang Province

The Wudaoling molybdenum deposit is a typical skarn type deposit in the LesserXing’an Range-Zhangguangcai Range metallogenic belt. Orebodies hosted incontiguous skarn zone between pyritization quartz porphyry and the tuffaceoussandstone of Wudaoling group, acid tuff, which is alterated product of alkali-feldspargranite. The mineral assemblage of skarn including garnet, diopside, actinolite andepidote etc. The orebodies, in the irregular veinlike form, occurs in branchingcomplex shape, extending along the strick or tendency in the shape of "S" in structurewith little undulatory forms, controlled by the occurrence of the contact surface. Oretypes including molybdenum, iron and pyrite ores. Ore structure is mainly in anhedraland semi-euhedral crystal granular, and semi-euhedral and euhedral crystal granularnext best. Massive and disseminated structure are the main structure of Ore. The skarnis main wall rock alteration near ore followed by silicification and sericitization,which mainly distribute in the inner contact zone. The beresitization widelydistributes in the fine-grained (porphyritic) alkali feldspar granite in the inner contactzone parallelling skarn rock zone. Hornfels distributes in the outer contact zone inlong strips shape parallelling to the skarn rock. The superposition of pyritization,carbonatization, choritization and epidotization, etc developing in skarn and thesurrounding rocks.The alkali feldspar granite and quartz porphyry in this areas, closely related tomineralization, are I-type granite, series of metaluminous-peraluminous and highpotassium calc-alkaline. Enrichment in large-ion lithophile elements (such as Rb, K, U etc.) and absence in high field strength elements (such as P, Ti etc.), it is compatiblewith geochemical features of subduction granite which take on the feature of intensenegative Eu anomalies. Research on LA-ICP-MS U-Pb Zircon showed that theformation age of quartz porphyry and alkali feldspar granite, are193.6±1.1Ma and193.9±1.3Ma respectively. Combined with characteristics of regional geologicalevolution, it is proposed that the formation of Mo-Fe deposits in Wudaoling is relatedto extended environment in the later period of the orogeny of the ancient Pacificsubduction and extrusion. The metallogenesis epoch is the Lower Jurassic（186±2Ma） and the origin of the deposite is skarn.