胶东西北部金热液成矿系统内部结构解析

成矿系统研究可划分为系统外部环境与内部结构2个方面, 外部环境分析立足于代表性成矿带———矿集区宏观地质背景的深入解剖, 着重揭示地球圈层的内部结构和构造体制转换-岩浆活动-流体汇集多种事件的耦合作用对成矿单元内部成矿流体活动与大规模成矿事件启动机制.内部结构研究主要通过矿田-矿床-矿体等多个尺度构造-流体-成矿作用的解析, 解剖矿体-矿化网络的时空结构, 查明成矿流体物理输运机理及元素的富集-输运-沉淀过程.以胶西北矿集区为例, 从分析系统内部结构的视角出发, 力图查明系统外部地质背景对矿集区内部成矿作用的影响, 并建立成矿系统内部各成矿要素(成矿产物、成矿过程等) 的内在联系; 作为成矿学研究思路的一种新的尝试, 深化区域成矿作用认识有一定推动作用.研究发现, 区域构造体制转换所引发的胶西北矿集区应力-应变场性质转变不但启动了区域成矿活动, 成矿活动在由压剪向张剪过渡的时空界面发生; 而且还造就了复杂多变的控矿构造形迹, 由于空间构造形迹及力学性质的差异, 导致了区域成矿的多样性.应力-应变场性质的变化引起流体各项物理化学参数发生了突变, 并引发成矿物质的富集沉淀, 成矿过程中流体一则由氧化状态向还原状态稳定过渡; 而不同构造形迹控制下的流体运移方式差异则是导致成矿多样性的内因; 成矿过程具复杂性, 其主要表现为矿体金品位和厚度的空间分布多重分形特征、蚀变分带的自相似性、成矿作用的突发性及成矿产物的多样性. 

An Analysis of the Interior Structure of the Gold Hydrothermal Metallogenic System of the Northwestern Jiaodong Peninsula, Shandong Province

The study of metallogenic systems includes two branches: the geological background and the system's interior structure. The geological background analysis is based on the dissection of the macroscopic environments of representative metallogenic belts or typical ore deposit concentration areas. It emphasizes the contributions of both the layered structure of the earth and the coupling processes of the transformation of tectonic regimes, magmatic activity and fluid influx to the activation of regional ore-forming fluid and the initiation of large-scale mineralization. The study of interior structure aims to clarify the temporal-spatial structure of the mineralized web, the physical mechanism of ore-forming fluid transportation and the chemical process of the enrichment-migration-precipitation of metallogenic elements. It considers the relationship between these elements by analyzing the tectonics-fluids-mineralization process in multi-scales, including orefield, ore deposit and ore body scale. Taking the Northwestern Jiaodong ore deposit concentration area as an example, and using a method of interior system analysis, the authors try to reveal the influence of the exterior geological environment of the ore-forming system on the metallogenesis of the interior ore deposit concentration area, and to establish the intrinsic relations of ore-forming factors (ore-forming products, ore-forming processes etc.).Resultsshow that the transition of stress-strain field properties, created by the transformation of regional tectonic regimes, leads to regional ore-forming activity, which occurs in the temporal-spatial interfaces where the shearing stress alters from compression to tensile. The transformation also forms the complex and multivariate ore-controlled structural features. The differences of spatial structural features and mechanical properties result in the variety of regional metallogeny. Variations of stress-strain field properties in the ore deposit concentration area range cause the mutation of physicochemical parameters of ore-forming fluid, initiating the deposition of the metallogenic materials in the fluid. Over geological time, the fluid's Eh declined, and changed from an oxidation state to a deoxidation state. The fluid transport mode, which was under the control of different structural features, is the internal cause of metallogenic variety. The complexity of the ore-forming process mainly shows in the multi-fractal features of the spatial distribution of the gold ore bodies' grade and thickness, the self-similarity of alteration zoning, the inflation of ore-forming activity, and the variety of ore-forming products. This research is a new method of study in metallogeny and also an important approach to deepen the understanding of metallogenesis.