湘南黄沙坪—宝山矿田构造应力场控矿规律及找矿方向分析

Ore-controlling regularity of tectonic stress field and ore-prospecting direction in Huangshaping-Baoshan ore field, southern Hunan

黄沙坪—宝山矿田位于湘南千里山—骑田岭矿集区,矿田内构造具多期性,且矿体产出明显受构造控制。在以往对于该区构造的研究中,缺乏针对构造变形过程及其控岩控矿过程的构造应力场数值模拟研究。基于前人研究成果,对矿田典型地质构造点进行详细解析,进一步完善了矿田构造体系和主要构造期次的应力状态,并运用ANSYS有限元数值模拟软件,探讨该矿田成矿前期、成矿期构造应力场分布特征及演化,总结构造变形特征及构造应力场控岩控矿规律,认为成矿前受区域SN向挤压作用形成近SN向压扭性断裂,而EW向断裂表现出明显的应变能低值,为之后岩浆侵位提供有利条件;成矿期最大主应力优势方位转变为NE向,且最大剪应力强度较大,指示该期变形强烈,并对先存构造有较强烈的改造作用,此时EW向应变能低值断裂带为岩浆侵位的有利通道,并受矿区外围NE向应变能高值断裂带的限制,使其能够在低应变能区不断聚集并沉淀成矿。最终通过对已知矿点构造应力场特征对比研究为该区找矿方向提供依据。

The Huangshaping-Baoshan ore field is located in the Qianlishan-Qitianling ore concentration area in southern Hunan.The structure in the ore field is multi-period,and the ore body output is obviously controlled by the structure.In previous studies on the structure of this area,there is a lack of numerical simulation of the tectonic stress field for the process of tectonic deformation and its rock-controlling and ore-controlling processes.Therefore,based on the previous research results,this paper analyzes the typical geological structure points of the ore field in detail and further improves the stress state of the ore field structure system and the main tectonic period.Using ANSYS finite element numerical simulation software,this paper discusses the distribution characteristics and evolution of the tectonic stress field in the pre-mineralization stage and ore-forming stage of the ore field and summarizes the characteristics of tectonic deformation and the law of tectonic stress field controlling rock and ore control.It is considered that the near SN trending compression-torsional fracture is formed by regional SN compression before mineralization,and the EW-trending fracture shows obvious low strain energy,which provides favorable conditions for subsequent magmatic emplacement.The dominant position of the maximum principal stress in the ore-forming stage changed to the NE direction,and the maximum shear stress intensity was large,indicating that the deformation was strong in this period,and the pre-existing structure was strongly reformed.At this time,the EW-trending strain energy low-value fault zone was a powerful channel for magmatic emplacement and was limited by the NE-trending strain energy high-value fault zone in the periphery of the mining area,so that it could continuously gather and precipitate mineralization in the low strain energy area.Finally,through the comparative study of structural stress field characteristics of known ore points,it provides the basis for prospecting direction in this area.