The Deep Tectonic-Magmatic System And Mineralization Of Tethys Composite Orogenic Belt In Sanjiang Region

Sanjiang orogenic belt is one of the most complex orogenic belts in the world,it experienced the late Paleozoic-Mesozoic Tethys tectonic evolution and Cenozoic continental collision composite orogenic process,there occurred a huge amounts of the metal accumulation and episodic massive metal mineralization which lead to the conformation of world-class polymetallic metallogenic province.Crustal tectonism,magmatism and mineralization in Sanjiang area are the comprehensive response of deep tectonic-magmatic evolution.Fundamentally speaking,deep tectonicmagmatic activity control the shallow geological characteristics and mineral distribution.According to the research of deep tectonic,magmatic activities and deep composite orogenic process of Sanjiang area,This paper built the deep tectonic-magmatic system and its ore-controlling model,also carried out regional three-dimensional metallogenic prediction and assessment which improved the reliability of predicted results.Based on the thorough research of the gravity,magnetic and seismic data,combined with regional geological features,we built Sanjiang region crust tectonic and magmatic system.The gravity and aeromagnetic data reflection of lithospheric faults in Sanjiang orogenic belts is obvious,it also strictly controls the superficial fracture distribution;It is the first time that we found the Yidun "long island arc magnetic body",Tengchong "super magnetic block" and Lincang-Menglian-Jinghong "complex collision magnetic belt" through aeromagnetic data quantitative inversion.The inversion of curie-interface depth reflect a large "double uplift" in the north of Sanjiang area,and the uplift zone of curie-interface is well corresponding with the mineralization zone;We outlined a number of regional deep faults and concealed magma rock mass after lithologic-structure mapping with geophysical data.All of above can provide important reference information for geological research and prospecting.In the thesis,we clarified the deep response of upper mantle to orogenic process,and discussed subduction-delamination model and crust-mantle interaction process in regional composite orogenic.The uplift and depression of moho surface are alternate arranged,orogenic belts are almost located in the moho depression area,while deep fractures usually distribute in the junction area of uplift and depression belt;Seismic tomography shows that India-Eurasian continent lithosphere subducted to lower lithosphere of Sanjiang area which caused massive delamination;Magnetotelluric data shows that the existing of large-scale low resistance of the deep material flow and seismic tomography revealed deep lower body are the direct evidences of regional material and energy exchange between crust and mantle.The regional deep faults system is the primary ore-controlling factor.Large deposits are strictly controlled by deep fractures,while the shallow secondary fractures of the large directly determined the spatial distribution of ore deposits;Inversion of Curie interface result shows that high geothermal gradient abnormal zones in the deep crust generally are the regional metallogenic belt;Deep low pillar is a important evidence of deep mantle material upwelling,which also shows the crust-mantle interaction;According to Sanjiang region complex tectonic evolution dynamics process,we preliminary built ore-controlling model of deep tectonic-magmatic system and the regional metallogenic dynamics model.We carried out three-dimensional metallogenic prediction for the first time,and selected many favorable metallogenic prospect areas with the fuzzy evidence weight method and based on the deep tectonic-magmatic system,also,integrated shallow regional geology,mineral,geophysical and geochemical data,Fuzzy evidence weight method has a unique advantage in the regional metallogenic prediction,combining with more information sources and evidence layers,the regional metallogenic prediction forecasting results are more credible.Three-dimensional metallogenic prediction technology which based on geophysical,geochemical,geological data and comprehensive deep magma-tectonic system realized the deep ore-controlling information application in regional metallogenic prediction,it also opened up a new way of thinking for regional exploration prospecting.