The Space-time Structure Model Of The Gejiu Superlarge Tin-copper-polymetallic Deposit

The Gejiu super-large tin-copper-polymetallic deposit is located on the southeastern Yunnan province, and technically situated on the junction area of Eurasian, Pacific and Indian plates. There are a long history of mineral exploitation and much more high geological researches in Gejiu ore district. But the substantive researches are mainly focus on the minerogenetic theory and related model based on granitic hydrothermal mineralization, and many conclusions have been drawn that the tin-copper-polymetallic deposit is mainly related to Yanshanian epoch granitic mineralization,and the metallogenetic period is medium-later Yanshanian epoch. Based on the geological fact which collides with granitic mineralization,this paper mainly do systemic researches on geologic features, mineralogy, trace elements, rare earth elements, stable isotope geochemistry, fluid inclusions of rock or orebody, and petrology, petrochemistry, geochemistry, regional geological synthetic analyses of the Gejiu strata formation. From that, some conclusions are summarized as follows:The geological environment of Gejiu ore district is a NE-striking fault basin during Indo-Chinese epoch which goes deep and wide smartly in middle-upper Triassic, and it may combine or join NW-striking fault basin named Guangnan-Qiubei and Malipo-Babu into a fault basin belt. The viewpoint also can be supported by the rock types of alkali-basalt, basalt-tuff, carbonatite bearing pyroclastic material, silicolite and so on. The characteristics of petrochemistry and rock occurrence show that the alkali-basalt in Gejiu strata formation was formed in the extensional tectonic setting within continent (T2gi $ ).Geochemical analysis of the regional strata and the section in-place measurements shows that the strata rich in tin and copper of Precambrian basement and Devonian system etc. is the partly mineral source for Gejiu Tin-copper-polymetallic deposit.The Gejiu strata formation is the mainly mineral-hosting rock series, but not the main source for mineralization.Comparison researches on different types of deposits indicate that the bedded tin-copper-polymetallic ore bodies in alkali-basalt have a volcano-sedimentary origin, and the bedded cassiterite-sulfide deposit in carbonate rock of Gejiu formation have a seabed exhalative hydrothermal sedimentary mineralization genesis. There are obvious characteristics of symphitic sedimentary. Their mineralizations occurred both during mid Triassic, the mineralization of latter is successive and successional. The bedded volcano -sedimentary copper (tin) ore bodies and exhalative hydrothermal sedimentary tin, copper (lead, silver) ore bodies are often superimposed by vein tin, tungsten, beryllium, copper, lead, silver ore bodies related to granitic mineralization of Yanshanian epoch. Symphitic sedimentary structures and strata are the key factors for volcanic sedimentary mineralization, exhalative hydrothermal sedimentary mineralization and output of bedded ore body. So if there are huge and rich ore bodies, there must be centers for volcano eruption and exhalative hydrothermal in the forepart and for granitic intrusion in the last stage.It is found that the symphitic sedimentary laminated striped ore bodies and thin(net) vein or thick vein bodies have the same source of metal, lead and sulphur through studying on the trace elements, rare earth elements, stable isotope geochemistry. Furthermore they mainly come from mantle. Alkali-basalt is the main mineral source for volcanic sedimentary tin copper deposit. The Yanshanian epoch granitic magma activity mainly provided drive power and heat for superimposed mineralization.The time-space structure model of Gejiu super-large tin-copper-polymetallic deposit has been set up. There take place three different stages of mineralization, such as seabed volcanic sedimentary stage, exhalative hydrothermal sedimentary stage in Indo-Chinese epoch and granitic superimposed activity stage in the mid-late Yanshanian epoch. So three types of metallogenic series and eight types of deposit models...