Metallogenic Geological Conditions and Prospecting Model of the Hulunxibai Gold Deposit in Ejinaqi, Inner Mongolia

Hulunxibai gold deposit is located in the western of hulunxibai-zhusileng reverse "S"-type arcuate structure.The NW-striking faults are large in scale,not only the main rock-and ore-controlling structures,but also the important pathways for hydrothermal activity.The late superimposed NE-striking secondary structures related to sub-volcanic rocks activity or deep cryptoexplosion are important depositing ore structure.Metallogenic materials are mainly from Jurassic porphyry biotite granite,syenite porphyry and gabbro.Ore-bodies are hosted in different structure positions with Jurassic porphyry biotite granite,syenite porphyry-sub-volcanic rock activity(or deep cryptoexplosion),and belong to post magmatic hydrothermal cataclastic altered rock type or subvolcanic type (magma crypto-explosion breccia type) gold deposit.The occurrence environment of the 13 gold veins having been discovered can be divided into two types: one is inner rock body or inner contact zone with wall rock,the other is outer contact interstratified fracture zone (weak zone).The major alterations closely related to ore-forming are silicification,pyritization,and chalcopyritization,and there is a positive correlation between gold grade and contents of metal sulfides.Based on the analysis of metallogenic geological conditions,the ore-forming model has been established preliminarily.