Characteristics Of Structural Deformation And Its Relationship With Mineralization In Baotan Tin Polymetallic Metallogenic Region,Northern Guangxi

Located in the southeastern margin of the Yangtze Plate and the southwestern section of the Jiangnan Orogenic Belt,the North Guangxi Baotan area is an important part of China's famous Nanling metallogenic belt in the western part of Jiuwandashan tin polymetallic metallogenic concentration area.The background of the geological structure evolution in this area is quite complex.The ore-controlling structure in the area has many characteristics such as multi-stage,multi-structure types,multi-movement directions and so on.Although the complex structural evolution features provide a good geological background for tin-polymetallic mineralization in this area,it brings many challenges and obstacles to clearly study the genesis of the deposits in this area.There are many types of volcanic rocks in the area,with basic,neutral and acidic volcanic rocks in different periods.Different magmatic intrusion provides a very rich source of ore-forming materials and ore-forming hydrothermal fluids in the area.In order to ascertain the relationship between multi-stage and multi-stage structural deformation and tin polymetallic mineralization in the area,the author relies on the project of the tutor to carry out work in the area.In this work,a large number of field investigations were carried out.A large number of field rock specimens and ductile shear zone directional specimens were collected.Through detailed microstructural analysis of the ductile shear zone,EBSD quartz c-axis fabric analysis,and mineralogy The analysis,LA-MC-ICP-MS U-Pb cassiterite dating analysis,etc.carried out a more detailed combing of the metallogenic geological background of the mining area and the metallogenic age of cassiterite.Achieve recognition and results:?1?It was preliminarily found that in the outer contact zone of some fine-grained granite veins in the Baotan tin polymetallic ore-forming area in northern Guangxi,there are strong victoria petrification and tin mineralization,and they have been transformed by ductile deformation.This indicates that there was a stage of dolmenite mineralization related to magmatism before the structural deformation.?2?Through macro and micro structural analysis,the investigation of tin polymetallic ore bodies is generally controlled by NNE or near-SN structural belts,which have undergone at least three stages of structural deformation.The ductile shear zone is the main ore-forming structure,and the exposed width is several tens of centimeters to several meters wide.?3?Through finite strain measurement and EBSD quartz c-axis fabric analysis,the formation temperature of the ductile deformation stage of the ore-controlling structural belt in the Baotan tin polymetallic metallogenic area in northern Guangxi is obtained,which belongs to the greenschist facies-angle The metamorphic conditions of amphibolite facies,and the temperature has an obvious increasing trend from northwest to southeast,indicating that the shear depth from northwest to southeast in this area has an increasing trend;finite strain measurement results show that it is squashed;obtained The variation range of the ancient differential stress is23.21?43.03MPa.?4?The LA-MC-ICP-MS U-Pb method is used for dating,and the harmonic age of cassiterite transformed by deformation is obtained to be 829.0±15.0 Ma,which is the highest value of tin element in the Pingying compound rock mass.The zircon U-Pb harmonic age?831.1±7.1 Ma?of fine biotite?two-long-?alkali feldspar granite?Pt₃??⁴T?in the fourth?inclusive?tourmaline is basically consistent within the error range,indicating that this type of tin The ore-forming materials of the stone may be mainly derived from the fourth magmatism of the Pingying compound rock mass.?5?Combining the above research results,combined with the previous research results of the region,the metallogenic materials of tin polymetallic deposits in this area may be mainly derived from the fourth magmatism of the Pingying compound rock mass,while the later tectonic activities The tin polymetallic elements are transported out of the source rock and enriched in ore in the ductile shear zone.