Geophysical Characteristics And Metallogenic Significance Of Volcanic Mechanism In Baiyinwula Mountain In The Southeast Of Inner Mongolia

Baiyinwula volcanic edifice is located in the southeastern segment of the Great Xingan Range metallogenic belt,adjacent to Baiyinnuoer Pb-Zn deposit in the northeast.The deposit,superimposed and reformed by paleo Asian Ocean,Mongolia-Okhotsk Ocean and paleo Pacific Ocean,is the best place for studying multi-stage mineralization.Based on the mineralogy,petrology and geochemistry studies,researcheres have determined that there are two stages of mineralization in Baiyinnuoer deposit.The mineralization alteration zone formed in the middle Yanshanian has the characteristics of hydrothermal vein deposit.Combined with the geological analysis,it is considered that the mineralization related to Baiyinwula volcano in the southwest occurred in this period.It is of great significance to establish the metallogenic model,determine the source of ore-forming materials and delineate the metallogenic prospect area by studying the deep relationship between the volcanic edifice and the deposit.In this paper,based on the comprehensive geophysical method,three-dimensional focusing inversion of large-scale gravity and magnetic data and two-dimensional inversion of magnetotelluric profile through baiyinwula volcanic edifice are carried out,and a geophysical model with a depth of less than 5 km in the study area is obtained.The gravity inversion results show that the volcanic edifice has a low gravity structure,and the important faults in the study area show the characteristics of gradient zone.In addition,a hidden fault is identified.The two groups of faults meet in the deep,and gradually become shallow from southwest to northeast.The results of magnetic inversion reveal that the volcanic edifice is characterized by high magnetic anomaly,and the deep part extends to the north,which may represent the connection with the deep part of the deposit.The resistivity model shows that there is a steep middle high resistivity anomaly below the Baiyinwula volcanic edifice,with high resistivity structure on both sides,which represents the feature that the former magma upwelling channel has crystallized.Combined with the study of regional geological setting,the following understandings are obtained:(1)Baiyinwula volcanic edifice is characterized by high magnetism,low density and medium high resistivity.The effect of magnetic and electric methods on the characterization of volcanic mechanisms is better than that of gravity methods;(2)The deep distribution characteristics of faults related to mineralization were obtained by using gravity,magnetic and electrical inversion results,and the ability of gravity,magnetic and magnetotelluric methods to identify fault structures was evaluated;(3)The ore controlling factors of Baiyinnuoer deposit are as follows: Baiyinwula volcanic edifice provides the source of hydrothermal material,the fault between the volcano and the deposit provides the favorable channel for hydrothermal migration,and the Permian Zhesi formation provides a good ore hosting location;(4)The distance between Baiyinwula volcanic edifices and Baiyinnuoer deposit is more than 2 km,which is consistent with the long-distance metallogenic model.During the magmatic activity,the hydrothermal material migrated to the ore bearing strata through important ore controlling faults and interacted with the sedimentary strata,resulting in the precipitation and crystallization of ore-bearing materials.(5)According to the gravity structure,the concealed faults are another group of important ore controlling structures,which connect the volcanic institutions and the sedimentary strata of Permian Dashizhai formation.It has the necessary elements for the formation of the deposit.Therefore,the location of 2 km in the southeastern side of the Baiyinnuoer deposit is a recognized metallogenic prospective area.