Quantitative 3D Association of Geological Factors and Geophysical Fields with Mineralization and Its Significance for Ore Prediction: An Example from Anqing Orefield, China

Abstract

Quantitative 3D spatial association of geological factors and geophysical fields with orebodies is critical for ore prediction. The Anqing orefield, a principal Cu–Fe orefield in China, is closely associated with the Yueshan intrusion. By compiling the data from drilling and tunnelling exploration, Controlled Source Audiofrequency Magnetotelluric (CSAMT) surveying and the computational modelling of magmatic intrusion’s cooling process, we constructed models of the Yueshan intrusion, ore-favourable carbonate formation, orebodies, resistivity field and volume strain field. These models are used as evidential factors to analyse their spatial association with mineralization by the weights-of-evidence (WofE) method. The location of orebodies is closely related to the shape of the contact zone of the Yueshan intrusion. The spaces with the distance ≤200 m to the concaves that were selected by minimum principal curvature (|Kmin| ≥ 0.0025) from contact zones, are very favourable for localization of orebodies. Most orebodies are not located in the spaces of the lowest resistivity, suggesting that the lowest resistivity cannot be used as an indicator for mineralization. The spaces with higher positive volumetric strain have higher positive weights with orebodies, implying that the mineralization is positively related to the positive volumetric strain. The spaces of all evidential factors that had positive correlation with mineralization were integrated to create a 3D prospectivity map by calculating posterior probability. Five areas with higher posterior probability, indicating higher prospectivity potential, are selected as targets for future exploration.

Keywords

• spatial association
• 3D geological modelling
• ore prediction
• weights-of-evidence
• Anqing orefield