新疆阿尔泰地区断裂控矿的多重分形机理

新疆阿尔泰地区断裂构造非常发育并对热液成矿有重要控制作用。分形分析表明该区断裂和矿床的空间分布均为多重分形分布,断裂的奇异指数为1.597～2.403,多重分维谱值为0.551～1.706;矿床的奇异指数为0.925～2.287,分维谱值为0.138～1.363。断裂的高的奇异指数和分维谱值表明该区断裂构造具有较高的成熟度和连通性,有利于提高岩石渗透性、促进流体流动和热液矿床的形成。断裂构造的多重分形分布导致该区热液成矿作用的多重分形分布。断裂体系演化过程中不同断裂部位变形和渗透性存在明显差异,数值模拟表明断裂与岩性和流体之间存在强烈的耦合作用并导致不同岩性的断裂具有明显不同的断裂渗透率。断裂-脉体系演化是一个自组织过程,元胞自动机模拟表明只有在分形渗透临界以上连通性较好的脊骨断裂部位是最有利于流体流动和成矿作用的。因此只有在部分有利的断裂部位才能形成矿床,并导致了断裂构造的奇异指数和多重分维谱值明显高于矿床。

Multifractal Mechanism of Faults Controlling Hydrothermal Deposits in Altay, Xinjiang, China

The fault structure is well developed and has an important role for controlling hydrothermal mineralization in Altay, Xinjiang, China. The fractal analysis indicates that faults and deposits spatially are all multifractal distribution with singularity exponent in 1.597～2.403 and multifractal spectrum in 0.551～1.706 for faults, and singularity exponent in 0.925～2.287 and multifractal spectrum in 0.138～1.363 for deposits. Large singularity exponent and high multifractal spectrum of faults show that the fault structure has high degrees of maturity and good linkage which is beneficial for enhancing permeability, facilitating fluids flow and controlling hydrothermal mineralization. The multifractal distribution of faults results in multifractal distribution of hydrothermal mineralization and ore deposits. The deformation and permeability in different areas are obviously different during the evolution of fault systems. Numerical simulation indicates that the strong coupling among faulting, lithology and fluids existed and resulted in different fracture permeability in different fractured rocks. The development of a fracture-vein system was a self-organizated process. Simulation using a cellular automation model shows that the backbone fault with good connectivity and over the fractal percolation threshold is the favorable sites for fluid flow and mineralization. Hence, only in some parts of a fault, ore deposits were formed, which results in that the singularity exponent and multifractal spectrum of faults are larger than those of ore deposits.