3D geological modeling for mineral resource assessment of the Tongshan Cu deposit, Heilongjiang Province, China

Three-dimensional geological modeling (3DGM) assists geologists to quantitatively study in three-dimensional (3D) space structures that define temporal and spatial relationships between geological objects. The 3D property model can also be used to infer or deduce causes of geological objects. 3DGM technology provides technical support for extraction of diverse geoscience information, 3D modeling, and quantitative calculation of mineral resources. Based on metallogenic concepts and an ore deposit model, 3DGM technology is applied to analyze geological characteristics of the Tongshan Cu deposit in order to define a metallogenic model and develop a virtual borehole technology; a BP neural network and a 3D interpolation technique were combined to integrate multiple geoscience information in a 3D environment. The results indicate: (1) on basis of the concept of magmatic-hydrothermal Cu polymetallic mineralization and a porphyry Cu deposit model, a spatial relational database of multiple geoscience information for mineralization in the study area (geology, geophysics, geochemistry, borehole, and cross-section data) was established, and 3D metallogenic geological objects including mineralization stratum, granodiorite, alteration rock, and magnetic anomaly were constructed; (2) on basis of the 3D ore deposit model, 23,800 effective surveys from 94 boreholes and 21 sections were applied to establish 3D orebody models with a kriging interpolation method; (3) combined 23,800 surveys involving 21 sections, using VC++ and OpenGL platform, virtual borehole and virtual section with BP network, and an improved inverse distance interpolation (IDW) method were used to predict and delineate mineralization potential targets (Cu-grade of cell not less than 0.1%); (4) comparison of 3D ore bodies, metallogenic geological objects of mineralization, and potential targets of mineralization models in the study area, delineated the 3D spatial and temporal relationship and causal processes among the ore bodies, alteration rock, metallogenic stratum, intrusive rock, and the Tongshan Fault. This study provides important technical support and a scientific basis for assessment of the Tongshan Cu deposit and surrounding exploration and mineral resources.