铜官山矿田深部构造的三维计算模拟及其找矿意义

摘要

计算模拟已成为研究矿田深部三维构造重要可行手段，对深部找矿具有重要意义。基于铜官山矿田地质背景及所获勘查数据特征，我们采用知识驱动下多级约束和多源数据融合建模方法模拟矿田范围内–2000 m以上主要地质界面。以逆冲推覆导致断展–断弯褶皱理论模式解释大地测深的电阻率数据，推断地质界面位置，在 Micromine- GOCAD耦合平台上在多级约束下融合多源的界面位置数据，以离散光滑插值算法和Delaunay三角网剖分法重构主要地质界面，在计算机虚拟空间再现矿田三维构造格架。结果显示：铜官山岩体和天鹅抱蛋岩体三维形态变化复杂，总体上向西倾，向深部岩体规模快速变小。位于铜官山岩体东接触带的铜官山铜矿田深部无找矿潜力，原因是接触带产状变陡，并且是岩体直接与上泥盆统砂岩接触；矿田深部主要构造为走向NE并沿倾向弯曲的逆冲推覆断层；铜官山背斜东翼含矿的中–上石炭统层位向深部倒转后又在–1200 m至–1500 m深度返转成向东南缓倾的正常层位，其底部与逆冲推覆断层重合，是深部找矿的有利靶区。%Computational modeling has become an important virtual technique for revealing the deep structures in 3D, which is critical for deep ore exploration. In view of the geological setting and the exploration data available for the Tongguanshan ore field, we simulate the major geological interfaces within the ore field deep to−2000 m by applying the knowledge-driven modeling method, during which multi-sourced data are integrated under multi-scaled constraints. The concept model for thrust induced fault-propagation fold and fault-bend fold is used to interpret the MT resistivity data, and the inferred positions of geological interfaces are used where no drills or tunnels are available. The multi-sourced data about the geological interfaces are integrated under multi-scaled constraints in the soft platform of coupled Micromine and GOCAD. The algorithms of DSI and Delaunay TIN are applied to reconstruct the major geological interfaces for virtually revealing the structure architecture of the ore field. The final modeling results demonstrate that the Tongguanshan and Tian’ebaodan intrusions, with very complex spatial variation in 3D geometric shape, are generally west-dipping and diminished sharply at depth. The majority of the ore bodies of the Tongguanshan deposit occur in the shallow part of the east contact zone of the intrusion, however, the economic potential of ore mineralization at depth is permissive because the steeper and directly contact with the Upper Devonian sandstone. The principal structure deep in the ore field is the NE-trending bend thrust fault. The ore-hosting strata, the Mid- to Upper Carboniferous sequences, in the southeastern limb of the Tongguanshan upturn anticline will be appear as gently dipping strata and cut by the bend thrust fault at the depth of−1200 m to−1500 m, and thus is likely favorable target for ore prospecting.