广东河台金矿剪切带变形条件的差异性成矿作用研究

It is well known that the shear zone related gold deposits mineralization processes, from the ore-fluid migration to enrichment and precipitation, are associated with the shear deformation conditions, including deformation types, strength, patterns, environment and kinematics. However, the genetic relationship and effect mechanism of the shear zone deformation conditions with mineralization differences are unclear..The deposits in the Hetai goldfield of Guangdong province are shear zones related. Numerous shear zones have been found in the goldfield. However, only the shear zones in the north of the goldfield have economic ore bodies, and others are weak or no Au mineralization. Moreover, the mineralization differences are also present in the different part of one shear zone. Therefore, the Hetai goldfield is a favourable object for study on the mineralization differences with shear zone deformation conditions. This project will focus on the No.9 Au-bearing mylonite zone. The macroscopic structure deformation characteristics of the shear zone will be investigated in detail, and compared with the barren one in the goldfield, to ascertain the Au occurrence regularity in the shear zones. Stress, strain and kinematics vorticity of the different Au content deformation rock samples from the shear zones will be calculated based on the field geological investigation and microscopic observation. Petrofabrics of the samples will be analyzed integrated use of AMS and EBSD methods. The results will give insights into the relationship of shear zone deformation conditions with mineralization differences, and the structural ore-controlling mechanism. The project not only will contribute to the shear zone metallogenic theory, but also provide a scientific basis for the prospecting of the analogous gold deposit.

与剪切带有关金矿的成矿过程（含矿热液的运移、富集和沉淀）都受剪切变形的类型、强度、方式、环境、运动学等条件控制，这已成为共识。然而，目前对剪切带变形条件与Au矿化差异性之间的成因关系和控制机制尚不清楚。.广东河台金矿是典型的与剪切带有关的金矿。矿区内已发现的多条剪切带中，仅北部的几条有工业Au矿体产出，其它剪切带矿化均很弱，且同一剪切带内不同构造部位矿化差异也很大。因而是开展剪切变形差异性成矿研究的理想对象。本申请拟对矿区内9号含矿剪切带变形特征进行系统的野外观测，并与不含矿剪切带进行对比，查明Au矿化在剪切带中的赋存规律。在此基础上，对Au矿化各异的变形岩石进行应力、应变测量和运动学涡度分析，并借助系统的EBSD岩石组构和磁组构分析（AMS），查清剪切带的构造变形条件与Au差异性矿化之间的时空制约关系，进而揭示其构造控矿机制。本研究可推进剪切带成矿理论研究，并指导类似矿床找矿勘探工作。

广东河台金矿是典型的与剪切带有关的金矿。工业化Au矿体仅产于北部几条剪切带中，且同一剪切带内不同构造部位矿化差异也很大。该类型矿床成矿过程受剪切变形的类型、强度、方式、环境、运动学等条件控制，然而，对剪切带变形条件与Au矿化之间的成因关系尚不清楚。本文首次利用XRD、磁组构（AMS）以及EBSD石英c轴组构对河台金矿高村（ML11号糜棱岩带）和云西（9号糜棱岩带）金矿床各类糜棱岩的变形条件进行综合研究。结果表明，两条含金剪切带都是在印支期NNW-SSE向近水平的强烈挤压作用下形成的，其中发育的糜棱岩为S型和SL型构造岩，具有强烈压扁的特征，剪切变形过程中纯剪切作用所占的比重要明显大于简单剪切，石英颗粒受位错蠕变的影响。剪切带中白（绢）云母的含量在初糜棱岩、无矿糜棱岩、含矿糜棱岩、无矿超糜棱岩、含矿超糜棱岩中逐渐递增，b0值也递增，指示压力递增。含矿糜棱岩的K1近于直立，且Km（＞500μSI）和Pj值都明显大于无矿糜棱岩。因此，糜棱岩的变形强度与含矿性具有一定的正相关关系，剪切带中韧性变形越强、且糜棱岩最大应变主轴（磁线理）倾伏角越陡的部位越有利于后期叠加脆性破裂和金的富集成矿。在糜棱岩、超糜棱岩矿化的过程中，微量元素未发生真正意义上的富集或亏损，而主量元素中MgO、CaO、LiO、Fe2O3和SiO2迁入，Na2O有迁出。高村矿床石英c轴组构特征显示剪切带主要以底面(0001)<11-20>滑移为主，伴有少量Ⅰ级柱面(10-10)<11-20>滑移，变形温度为中低温（250℃~450℃）；而云西矿床以Ⅱ级柱面(10-10)<0001>滑移为主，反映高温（550℃~650℃）变形。因此，云西矿床比高村矿床有明显的抬升剥蚀，高村金矿床深部更有找矿潜力。以上研究成果丰富和完善了剪切带型金矿的成矿理论，为河台金矿的深部找矿研究提供了重要的依据。