构造-流体-成矿作用的分形与混沌动力学

Fractal and Chaotic Dynamics Mechanism for Tectonic-Fluid-Mineralization

系统分析总结了构造活动与裂隙-脉体系统的分形生长,构造活动、流体作用及矿物沉淀之间的非线性反馈作用以及具分形结构与混沌特征的矿物沉淀和矿床的形成过程。以湘西金矿、水口山铅锌金多金属矿田等典型矿床为例,研究发现,水口山铅锌金多金属矿田地层及岩体内的元素含量分布均呈单分形关系,而断裂带内动性较强的Cu、Pb、Zn等成矿元素的元素具有双分形关系,产生了新的元素分布规律,指示断裂活动促进了成矿元素富集,湘西金矿石英脉是通过分形生长向着脉体长度-厚度分维值a值先减小(对应着脉体的膨胀)然后增大(对应着脉体的伸长)的趋势发展演化的,且该矿床各中段金品位空间变化序列均为非线性演化序列,其成矿流体的演化及成矿元素的沉淀富集成矿过程为混沌动力学过程。这些结果表明,构造-流体-成矿作用具有分形结构特征,并具体表现为断裂体系的分形分布,矿床的分形分布,裂隙-脉体系的分形分布和品位分布的分形变化等。成矿元素活化、迁移及沉淀的复杂动力学过程中,构造活动控制了裂隙-脉体系统的分形生长与矿床的就位,且存在于构造活动、流体作用及矿物沉淀之间的非线性反馈作用最终导致了具分形结构与混沌特征的矿物沉淀和矿床的形成。

Tectonic-fluid-mineralization system is one part of earth material system that characterized by space-time complexity,original and boundary condition dependences,self-similar fractal structure and self-organize critical.It abides by some laws and at the same time shows randomicity and complexity.In this paper,the fractal growth of fracture-vein system,the nonlinear feedback of tectonic-fluid-mineralization system and the deposition and mineralization with fractal structure and chaos characteristics are summarized.To investigate the fractal structure of tectonic-fluid-mineralization system,two typical deposits are studied.Fractal analyses of element contents of fracture zone and strata in Shuikoushan Pb-Zn-Au polymetallic ore field in Hunan province,China,indicate that strata and granites show single fractal relationship on the original element distribution but the fracture zones show bifractal relationship with some more active elements such as Cu,Pb and Zn.The bifractal relationship indicates that at least two geological processes control the element distribution and the tectonic processes enhance the enrichment of ore-forming elements.The fractal relationships of thickness vs.length of veins in the Xiangxi Au deposit,Western Hunan province,China,demonstrate that vein grew mainly in lateral expansion and the fractal dimension a1 during the early stage and it extended rapidly via vein linkings and resulted in the dimension a1 when vein reached certain size.And what＇s more,the spatial variation of Au grade in the Xiangxi Au deposit shows a chaotic series and suggests the evolution of ore-forming fluid and the enrichment and deposition of Au are chaotic dynamic processes.In generally,tectonic-fluid-mineralization systems show a fractal structure characteristic which includes the fractal distribution of fracture system,ore deposits,fissure-vein system and ore grade.The mineral deposition is a complex nonlinear dynamic process with the activation,migration and sedimentation of ore-forming elements.The tectonic activity controlled the fractal growth of fissure-vein system and the location of ore deposition.Ore-forming metal elements in hydrothermal system will deposit at appropriate places through a complex nonlinear feedback effect among structural stress,fluid flow and fluid-rock reaction and result in the fractal and chaotic characteristics of the deposits and grade distribution.