湘西合仁坪金矿床角砾岩的地质特征及形成机制

湘西合仁坪钠长石-石英脉型金矿中,角砾岩普遍发育,主要分布于矿脉中,与金成矿关系密切。在详细的野外观察和室内研究的基础上,文章对合仁坪金矿床中角砾岩的形态、大小及胶结物进行了较系统的研究,并结合角砾岩的矿物组合特征,探讨了该区角砾岩的形成机制。研究表明,合仁坪金矿床中的角砾岩大多数呈原地破裂特征,角砾分选差,成分简单,且角砾之间的拼合性较好,为钠长石、石英等热液矿物所胶结,角砾的长轴方向大致具有定向排列的特点,表现出明显的液压致裂特征,反映出成矿流体的特征。研究区的液压致裂作用具有脉动性,每期液压致裂作用大致可分为应力腐蚀、岩石破碎、裂隙愈合3个阶段。

Geological characteristics and formation mechanism of breccias in Herenping gold deposit, western Hunan Province

Breccias are widespread in the Herenping albite-quartz lode deposit, western Hunan Province. Breccias are mostly distributed in ore veins and are closely associated with gold mineralization. Based on detailed field observation and indoor study, the authors systematically studied the morphology and size of fragments as well as the cements in breccias. In combination with the mineral assemblage, the formation mechanism for breccias was further ascertained. It is shown that most breccias are in-situ fractured, poorly sorted and simple in composition, and that slate fragments are usually in good collage and cemented by hydrothermal albite and quartz. The long-axis of fragments is approximately aligned. All these characteristics show that the breccias in the Herenping mining district were caused by hydraulic fracturing, which can reveal the characteristics of ore-forming fluid. It is concluded that hydraulic fracturing in the studied deposit was continual and periodic, and each period can be divided into three stages: Wear erosion, rock fracturing and crack sealing.