面向隐伏矿体三维预测的成矿空间复原方法研究

Most discovered metallic mineral deposits show the characteristic of superimposed mineralization, and are found to experience tectonic reworking and destruction. In existing methods for three-dimensional (3D) prediction of concealed orebodies, however, less concern was drawn to the phenomena of tectonic reworking and superimposed mineralization. Due to the regardless of multiphase superimposed and reworking of the metallogenic space in prediction modeling, effectiveness and reliability of the prediction are limited. This project puts forward the idea to combine 3D prediction of concealed orebodies with restoration of historical metallogenic space, which plans to study the method of metallogenic space restoration for 3D prediction of concealed orebodies and thus realize the prediction based on the historical metallogenic space. The project will first build the 3D prediction model for existing metallogenic space, and then carry out space-time decomposition of metallogenic process. Furthermore, the original states of the historical metallogenic spaces will be restored. Finally, the project will build 3D prediction model based on historical metallogenic space and carry out further comparison and analysis. The implementation of the project will present a method for restoration of metallogenic space and information, and invent key techniques regarding tectonic reworking and superimposed mineralization in 3D prediction of concealed orebodies, which might thus boost the prediction reliability and accuracy. The study will prove its theoretical and realistic significance in its contribution to the theory and method of mineral resource prospecting and in the guidance for exploration targeting in deep and marginal region of mines.

已发现的金属矿床大多具有叠加成矿特征，并历经构造改造或破坏作用。然而，现有的隐伏矿体三维预测方法对构造改造和矿化叠加现象关注尚少，未能从模型上较好地表达成矿空间的多期叠加与改造，已成为制约预测结果有效性和可靠性的关键问题。本项目提出隐伏矿体三维预测与历史成矿空间复原相结合的思路，研究面向隐伏矿体三维预测的成矿空间复原方法，实现基于历史成矿空间的隐伏矿体三维预测。拟首先建立基于现存成矿空间的三维预测模型，然后开展成矿过程的时空划分，进而实现历史成矿空间原始状态的复原，最终建立基于历史成矿空间的三维预测模型并开展对比分析。项目的实施将形成一套面向隐伏矿体三维预测的成矿空间与成矿信息复原理论与方法，创新顾及构造改造与矿化叠加的隐伏矿体三维预测方法与关键技术，可望提高预测的可靠性与准确性，对发展现有矿产资源评价理论与方法，指导矿山深边部找矿，具有重要的理论与现实意义。

本项目针对现有的隐伏矿体三维预测模型未能较好地表达成矿空间多期叠加与构造改造破坏的问题，选择山东大尹格庄热液型金矿床和甘肃金川岩浆型铜镍矿床为典型试验对象开展研究，建立了顾及构造改造与矿化叠加的成矿空间与成矿信息复原方法，形成了基于历史成矿空间的隐伏矿体三维预测方法。厘定了大尹格庄金矿床成矿演化期次划分为两个主要成矿阶段和一个成矿后构造破坏阶段，建立了胶西北金矿集区和大尹格庄金矿床的构造-岩浆-流体成矿模式；厘定了金川铜镍矿床五期古构造应力作用和成矿后金川岩体变形域与变形量，提出了金川矿床多岩浆通道成矿模式。建立了大尹格庄矿床和金川矿床现存空间的三维地质模型、成矿信息模型和三维预测模型，认为大尹格庄金矿化主要受断裂面距离场（dF）、断裂面坡度（gF）、断裂面陡缓转换部位综合场（fP）、断裂面一级起伏（waF）和二级起伏（wbF）五个因素控制，金川铜镍矿化主要受断层面距离场（xcdFault）、顶底板相对距离（xcdRatio）、岩浆通道中心线距离场（xcdMC）和底板趋势面距离场（xcdTrend）四个因素控制。提出并开发了基于TIN的被错断断层复原建模方法和基于改进薄板样条的历史成矿空间复原方法，消除了大尹格庄金矿床主控矿断裂、地质体和矿体TIN模型的撕裂、扭曲等空间形变，消除了金川基性-超基性岩体的脆性破裂剪切、叠瓦式逆冲和逆-平移切错破坏，复原了矿床的地质体原始形态、矿化结构和成矿空间。在复原的历史成矿空间下，建立大尹格庄金矿床和金川铜镍矿床的三维预测模型，模型AUC、R2和ROC对比结果表明，复原预测模型具有更好的预测效果。根据新方法预测结果，圈定大尹格庄金矿床和金川铜镍矿床的深部找矿三维靶区，经矿区深部钻孔验证，在深部发现新矿体。本项目提出的成矿空间复原方法和三维预测改进方法，对矿床形成的矿化叠加与构造改造问题的研究具有科学意义，对深部找矿具有应用价值。