Research On Spatial Dsitribution Characteristics Of Metallogentic Elements Composing Gold-Polymetallic Deposits In Ailaoshan

With the sustainable and quick development of our country's economy, in a very long period from now, the demands on mineral resources will become more and more. However, many mining areas in our country are confronting with the shortage crisis of mineral resources, so the investigating and probing on new mineral resources become a hot and key work at present.This paper,"research on spatial distribution characteristics of metallogentic elements composing gold-polymetallic deposits in Ailaoshan", is based on"research on development and applying of investigating and exploiting technology for gold-polymetallic deposits in Ailaoshan"(task 10) which is a subtask of"research on the probing technology and demonstration activitys looking for replacing gold-polymetallic deposits for mining areas at risk", a national support program of science and technology in 5-year plan of No.11.The paper, taking GIS as a developing platform and the metallogenic prognosis theory based on comprehensive information as a main tool, deals with the spatial distribution characteristics of geochemical elements.The dissertation depends on the stream sediment geochemical survey measured 1∶200,000 in Ailaoshan of Yuanyang county and takes the topography map and geological map of scale 1∶200,000 as basic data. Geochemical anomalies are identified by the method of factors-universal kriging model and the spatial quantitative association anomaly of elements is implemented using this method. Taking the topography map of Yuanyang county as data source, the digital elevation model (DEM) has been found. Through the hydrological analysis on digital elevation model, the catchment basins and water network maps are extracted. Then according to the metallogenic geological conditions and the water network map of catchment basins, the metallogenic prognosis is made by the analysis on dispersion pattern of orebody determined by the anomaly. The aim of this paper is to establish a theoretical model about the visualization showing of geochemical element distribution on surface and make application in metallogenic prognosis.Geochemical data processing has two purposes: first, to determine the regularity of symbiotic element association; second, to separate geochemical anomalies from geochemical background. The dissertation uses factor analysis of multivariate statistical analysis to study the paragenetic association regularity of elements. Factor analysis has the function of compressiing variable space and reproducing inner correlations of primitive variables. Using the techniques that factors come from the linear association and the rotation transformation of original variables, we can convert multi-element variable collection in geochemical data matrix into several indexes of elemental quantitative composition which has a specific significance of instructing orebody. 1,846 samples are taken and 26 geochemical elements are analysed in the study area. The analysed elements are: Ag,As,Au,Ba,Be,Bi,Cd,Co,Cr,Cu,F,Hg,Mn,Mo,Ni,Pb,Sb,Sn,V,W,Zn,Al2O3,Fe2O3,K2O,MgO,Na2O. Through the orthogonal factor rotation conversion of R-variance extremely great, those samples are simplified into seven main factors. High load variables in factor F1 are Fe2O3, Co, Mg, P, Cu, Cr, Ba and Sr; High load variables in factor F2 are As, Mo and Sb; High load variables in factor F3 are Cd, Pb, Zn, Ag and Mn; High load variables in factor F4 are As and Al2O3. High load variables are not obvious in factors F5 and F6, and they are not discussed in this dissertation.On the basis of the factor solution of variance extremely great orthogonal rotation, we can find out anomaly from the new lattice which relys on the original grid data. The process follows the correlation and designability of spatial data and the multivalence of controled spatial objects. In the process searching for anomaly, the above lattice data can be expressed as Z(x), a drifting regional variable, so Z ( x ) = m ( x ) + R ( x), then , through the seeking of mathematical expectation m(x), R(x), a anomaly region, can be obtained. Of course, it is assumed that Z (x) has variability function and its theoretical model is the spherical model. And the increment of variability function has first moment and second moment. Solving kriging equations without bias and under optimal conditions, we can get m(x). Abnormal results are expressed by contours which show the intensity and the scope of an anomaly. We have recgonized 15 anomaly districts in the studied area. The direction of abnormal distribution was roughly NW-SE, the same as the direction of main tectonic lines in the region.According to the data sources of 1∶200,000 topographic map and the method of irregular triangular network modeling, the DEM of the study area has been found in ArcGIS, stacking remote sensing images and geological grid map in the ArcScene, and implementing the 3D visualization of topographical features and the distribution of geologic bodies in the study area, then professional information is visually expressed and the natural landscape features are simulated, which are shared, collaborative and distributed. 3D visualization of anomalies about elements'quantitative association in space shows the space distribution, magnitude and geometry of an anomaly more concisely and visually.The extraction of the hydrological characteristics in stream area is depending on data sources of the digital elevation model (DEM). The United States Environmental Systems Research Institute (ESRI) provided a hydrological analysis model (Hydrology Model) for ArcGIS, mainly for the extraction and analysis about terrain and river networks in order to implement terrain model visualization.The metallogenic belts in the study area undergo poly-episodes of structural-magmatic activities and deposit-forming activitis during geologic history. The study area is strongly effected by the Himalayas diastrophism which is the last and most important metallogenic event for endogenous deposits. The mineral deposits in the studied area are controlled by the northwest-strike deep-seated Honghe Fault,Ailaoshan Fault and Jiujia-Anding Fault as well as the secondary faults derived from the main ones.The northeast-strike faults also contrall the distribution of the mineral deposits and provide the space for ore-forming.Especially the intercross locations of the northwest-strike linear structures and northeast-strike linear structures controll the distribution of mineral deposits very well.Smaller faults,detachment structures between layers and broken rock belts also controll the distribution of mineral deposits. The ultrabasic, basic and acid rocks as well as veinrocks have intimate relations with mineralization in genesis and ore-forming space. The known mineral deposits or mineralized spots are distributed in the areas composed of magmatic rocks. Parts of the mineral deposits are located in the inner parts of plutons, or near the plutons and veins, and the external contacting belts of plutons. The ultrabasic, basic and acid rocks are the main ore-bearing rocks in the studied area On the basis of elements'spacial quantitative association anomaly, geological background of mineralization and tracing the source of anomaly in river network basin, a total of 5 polymetallic mineralization districts are recognized and the main ore-forming elements are: Fe,Co,Cu,Cr,Cd,Pb,Zn, Ag,As,Sb and Mo.The information about existing research and analysis in Yuanyang district shows that the area has plenty potential for exploration. We suggest that an 1∶50000 regional geochemical survey in the abnormal area should be started, meanwhile with geophysical exploration. The gravitation and magnetic prospecting can help to interpret the basement and deep-seated faults and identify geological bodies which cause the anomalies and to provide evidences searching for mineral deposits.