Resource assessment based on 3D-GIS technology and BP network method in the Pulang porphyry Cu copper deposit, Yunnan, China

Category Other
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Wang, Gongwen۱; Du, Yangsong۱; Chen, Jianping۲
Holding Date 15 September 2008

With the development and maturing of computer graphics and database, 3D visualization technology has become an important and practical research field to predict the location of ore and estimate quantities of resources. In this paper, a 3D GIS system using block interpolation is developed with Visual C++ 6.0 and OpenGL graphics library. In this 3D GIS system, the 3D ore-body and 3D mineralized body models are discredited into regular hexahedrons, and each vertex is taken as an interpolating point. At each interpolating point, a sphere with alterable radius is used to search enough adjacent sampling points to interpolate the attribute of this point using Inverse Distance Weighted interpolation function. There are 8145 samples with Cu grades collected from 72 boreholes data in Pulang Cu deposit. All the data refer to the same system of coordinates in order for their relative spatial locations (X, Y, and Z) to be determined. The Cu grade of 3D mineralized body is not less than 0.2% and the Cu grade of 3D ore-body is not less than 0.3% in the deposit, the standard index of Cu boundary grade and industry grade respectively in China, are set up by using Regular Hexahedron Imaging Technique of 3D-GIS and Spatial Interpolation of Adjacent Sampling Points. Based on the 3D models of Pulang Cu deposits, the important insights are as follows:
• The concealed ore body can be inferred. Both the mineralized body of 3D model and the ore-body of 3D model are like a cone. According to the geological feature and the 3D models of the deposit, a significant ore zone is located in the northern portion of the mine that has produced approximately 8000 t of copper, and a potential exploration zone is located in the southwestern portion of the mine.
• The reserve of copper deposits can be evaluated. Based on the amount of hexahedron cells from the ore-body 3D model, the Cu grade of each hexahedron cell in this model, and the same proportion of ore in the deposit, the Cu reserve of this deposit is about 3,352,000t,that is controlled by 72 boreholes.
• The Cu grade model can be set up using BP network and slice image in different elevation from the mineralized body 3D model in uprightness direction. According to the Cu grade model and the index of Cu industry grade(0.3%) in China, the predicting deep of Cu ore-body is 1050m in this deposit.
•Combined with the Cu grade model and the mineralized body 3D model, the predicting reserve of Cu in Pulang deposit is about 6,058,000t.