湖北铜绿山铜铁矿床成矿机制探讨

以铜绿山铜铁矿为例,探讨了浅成岩体冷却过程中夕卡岩及夕卡岩矿床在接触带上的形成过程及其耦合条件。在铜绿山矿区,矿体主要产出于石英二长闪长玢岩与下三叠统大冶群碳酸盐岩的半岛状-岛链状残留、捕虏体接触带中,矿体与夕卡岩密切共生。此次工作根据大量野外观察,结合对已有资料综合研究,提出成矿空间为冷缩低压区的概念,即夕卡岩及夕卡岩矿床形成的起因是在岩浆固结后的岩石冷凝收缩过程中,在接触带上形成了一个能使流体持续汇聚和长期驻留的低压区——冷缩低压区系统。这个系统与岩浆期后热液的耦合,在超临界流体、CO2气体和临界转换作用的配合下,满足了夕卡岩型矿床成矿的需求,形成了铜绿山矿床。

A discussion on the genetic mechanism of Tonglüshan skarn Cu-Fe deposits, Hubei Province

This paper discusses the cooling process of magmatic rock mass during the formation of the skarn and skarn deposits in contact zone and their coupling conditions,taking the Tonglüshan Cu-Fe deposit as an example.The host rocks of Tonglüshan ore body are quartz monzodiorite porphyry and the Lower Triassic Daye Group carbonate rocks,which are in the contact zone with the form of peninsular and island-chain-like residues and xenoliths.The ore body and skarn are closely coexisting.The contact boundary lines among main ore body,skarn,magmatic rock mass,carbonatite,and other ores are generally distinct.On the basis of a large number of field observations and comprehensive study of existing data of the tectonic setting of intrusions and ore bodies,and considering the facts that the carbonatite residues were in peninsular or island-chain-like forms and the xenoliths were at a stable and closed state in a period after the consolidation of magma,we put forward a concept of cooling shrinkage low-pressure area.We pointed out that a cooling shrinkage low-pressure area system was formed when the condensation shrinkage after the consolidation of magma was taking place,and the fluids were continuously gathered together and preserved in this area for a long time.The coupling of this cooling shrinkage low-pressure area system with the post-magmatic hydrothermal fluids presented an appropriate condition for the formation of skarn and skarn ore deposits,leading to the occurrence of the Tonglüshan deposit.