The Metallogenic Features And Ore-forming Prediction Of Basalt Type Tin-copper-polymetallic Deposit In The East Area Of Gejiu

The thesis title is selected based on Research on Prospecting prognosis of Tin-copper-polymetallic Deposit in Gejiu,Yunnan which is the key scientific and technical item (serial number:3-4-05-05) of Yunnan Tin Co Ltd. This paper has lucubrated the Metallogenic features of basaltic deposit in the east area of Gejiu, set up a metallization-prospecting model and synthetically alpplied GIS and 3D Technology for prospecting prognosis.For years, research work at Gejiu tin deposit was mostly about the metallogenic theory of granite and the construction of its model. Many studies indicate that Gejiu tin-copper polymetallic deposit was controlled by Middle and Late Yanshanian granite and its related structure, the time of ore-forming was relatively concentrative. Recently, as deep sulfide type deposits exploited becomes more and more, especially new stratiform ore bodies are found, some people put forward the cognition of basic volcano-sedimentary metallogenesis and exhalative-sedimentary metallization. Great attention is paid to the relationship between Middle Indosinian basalt in the ore-bearing rock series and tin-copper polymetallic deposit.The metallogeny of Gejiu tin-copper polymetallic deposit is very complex. So it is not enough to reasonably explain the genesis of the deposit merely by the single source of ore and the simple view of granite mineralization. Based on the work of antecedents, combined with field exploration and datum collecting, the regional geologic background, the distribution characteristic of basalt and its 3D display, petrology, petrochemistry and the deposit's geological characteristics are studied in the east area of Gejiu mine. According to integrative studies of major elements, trace elements, rare earth elements, isotopic geochemistry and chronology of mineralization, the basalt in east area of Gejiu was the main source of ore-forming materials and the intrusion of Yanshanian granite provided heat and hydrothermal fluid and partial source of ore-forming materials during the ore-forming process. The shapes,occurrences and scales of ore bodies were controlled by the spatial combination form of basalts and granite.Based on systematically collecting of drilling data, and combined with elevation measurement of the basalt in the east area of Gejiu, spatial distribution map of basalt and granite has been systematically drew with amendments, shapes and occurrences of the rock bodies have been displayed by 3D technique, and ore-forming regularities have also been concluded according to the spatial relationship among the known ore deposits (bodies) and basalt layer and granite. Under the guidance of metallization-prospecting model of basaltic deposit, profitable positions of prospecting are concluded, through analysis on the spatial combination profile features of basalt layer and granite. And prospecting targets are delimited in the research area by using GIS technique. These provide scientific bases for prospecting prognosis.