Study On The Spatial And Temporal Distribution Regularity And Isotopic Geochemical Characteristics Of Tin Deposits In China

China is the country with the richest tin resources in the world.Tin is one of critical strategic resources and China's dominant mineral resources,with a high strategic position and social value.After years of exploitation and utilization,China's tin resources are facing with a crisis,and China has changed from a major exporter of tin to a country dependent on imports.Therefore,it is of great significance to increase the intensity of prospecting,explore new tin resources and maintain the stability of China's tin resources.Over the years,a lot of isotopic geochemistry and chronology data have been accumulated in the previous studies,but the data are relatively scattered and lack of systematic synthesis.In this study,we collect analysis data on various important tin deposits in China from previous studies and establishes China's tin deposits database,in which includes mineralization geochronologica and geochemical data,in order to get systematical synthesis.The research results of the thesis will provide certain basic information for the improvement of tin deposit research in our country and further exploration of tin deposits in China.The main progresses achieved are as the follows:(1)To identify the metallogenic series and metallogenic belts related to tin deposits in China,the metallogenic series related to tin deposits in China are divided into 22 metallogenic series,44 metallogenic belts related to tin deposits and 15 important ore concentration areas.(2)The geochronologica results of China's tin deposits show that the tin-forming period of China includes Precambrian,Caledonian,Hercynian,Indosinian,Yanshanian,and Himalayan,and particularly160-130 Ma and 100-80 Ma in Yanshanian period,followed by Caledonian,Hercynian,and Himalayan;tin deposits of different metallogenic ages have a concentrated distribution feature,of which the Precambrian tin deposits are mainly distributed in the western Sichuan and northern Guangxi mining areas;the tin deposits in the Yanshanian period are mainly distributed in the ore concentration areas of the northern Guangxi,southeastern Yunnan,southern Hunan,Linxi-Xilinhaote;the tin deposits in the Caledonian period are mainly distributed in the Qimantag metallogenicarea;the tin deposits in the Hercynian period are mainly distributed in Eastern Junggar and Xingxingxia ore Concentration areas;the tin deposits in the Himalayan period are mainly distributed in Sanjiang ore Concentration area.On this basis,the establishment of China's tin metallogenic lineage was obtained.(3)Sulfur isotopic data show that there are two main sources for China's tin deposits:(1)magma source;(2)magma-based with mixing of strata;hydrogen and oxygen isotope data indicate that the source of ore-forming fluid is mainly from magmatic water with additions of meteoric water.Lead isotopic data show the complex,mainly lead in the upper crust and lead in subduction zones where the upper crust and mantle are mixed.On the whole,the diagenetic and ore-forming materials aremainly derived from the crust with a little mantle source.(4)Based on the results of previous studies,the diagenetic and metallogenic dynamics background of tin deposits in the early-late Yanshanian of Mesozoic in south China and late Jurassic-early Cretaceous in the southern part of the Great Hinggan Range were preliminarily discussed.