斑岩型矿床容矿裂隙成因的几种概念模型及其意义

Conceptual model for genesis of mineralized fissures in porphyry deposits and its geological significance

斑岩型矿床对成矿的围岩没有选择性,但斑岩型矿床的网状裂隙系统控制了矿体的分布、矿石的品位和组构变化、矿化蚀变等特征,因此对容矿裂隙的形成机制、控制因素、裂隙分布规律等开展研究有着重要意义。文章探讨了斑岩在侵位、冷却、结晶演化过程中,在岩体及其围岩中形成网状裂隙系统的相关机制及其制约因素,将斑岩型矿床容矿裂隙的成因归纳为岩浆结晶冷缩、侵入挤压、水岩分离和区域应力叠加等4种主要成因类型,并构建了它们的概念模型。这些裂隙成因概念模型较好地反映了不同成因的裂隙系统与斑岩侵入体的空间依存关系、裂隙的分布特征及裂隙率的变化规律,以及它们之间的差异;较好地解释了斑岩型矿床的成矿作用特点及其共性特征。在分析典型斑岩型矿床容矿裂隙成因的基础上,提出了将概念模型应用于斑岩型矿床勘查找矿的思路。

Porphyry deposits do not choose their mineralized host rocks,but the distribution of the orebody,the grade and composition of the ore,and the mineralization-alteration characteristics are controlled by the extensively developed reticular fracturing system of the porphyry deposit.Therefore,the study of the formation mechanism,controlling factors and fractures distribution of the ore-bearing fractures is of great importance.In this paper,the mechanism concerning the reticular fracturing system formation in the porphyry rock mass and its surrounding rocks during the emplacement,cooling and crystallization evolution of porphyry rock mass is discussed.Further-more,the genesis of the fracturing is divided into four main types:magma crystallization shrinkage,magmatic intrusion extrusion,water-rock separation,and regional stress superposition,and their conceptual models are constructed.These conceptual models for fracturing genesis can better reflect the spatial dependence of different genetic fractures and porphyry intrusions,the distribution characteristics and the variation of fracture rates of fractures,and the differences between them;in addition,they can better explain the distinct porphyry mineralization characteristics and common characteristics of ore deposits.Based on an analysis of the genesis of the ore-bearing fractures in typical porphyry deposits,the authors put forward the idea of applying the conceptual model to the exploration of porphyry deposits.