云南东川铜矿马尾丝状铜矿石特征及成因

东川铜矿位于扬子板块西南缘康滇构造带中,其矿体发育在落雪组白云岩中,典型矿石为马尾丝状铜矿石。本文对马尾丝状铜矿石的宏观和微观特征进行总结,通过ICP-MS和EMPA方法获得铜矿石和白云石主量元素特征,综合收集硫同位素值,对其成因进行探讨。研究表明马尾丝状铜矿石由顺层细矿脉和高角度切层含矿脉组成,两者在结构、构造、矿物组成、Ca/Mg比值等方面基本一致,具有明显的交代结构。容矿岩石表现为砂质层与泥质层互层,顺层细矿脉主要分布于砂质层中,马尾丝状铜矿石的SiO2含量明显高于弱矿化白云岩,说明顺层细矿脉发育于渗透性较好的石英砂质白云岩中。含矿卤水沿断裂构造运移至落雪组白云岩中,向两侧含孔隙度较高的砂质白云岩和叠层石白云岩顺层交代,形成以马尾丝状铜矿石为主的东川式层状铜矿体,马尾丝状铜矿石属于盆地卤水交代成因。

Characteristics and Genesis of the Horsetail-like Copper Ore in Dongchuan Copper Deposit, Yunnan

Dongchuan copper deposit is located in the Kangdian tectonic belt, southwest margin of the Yangtze plate. Dongchuan type copper body is developed in the dolomite of Luoxue Formation, and its typical ore is horsetail-like copper ore. In this paper, we summarized the macro- and microscopic characteristics of horsetail-like copper ore, evaluating the main element characteristics of copper ore and dolomite by ICP-MS and EMPA methods. Combined with the sulfur isotope values, we discuss the origin of the horsetail-like copper ore. The results show that the horsetail-like copper ore consists of bedding .ne veins and high-angle ore-bearing veins, which are basically the same in structure, tectonic, mineral composition and Ca/Mg ratio. The two veins exhibit obvious metasomatic structure. The ore-hosting rocks are interbedded with sandy layer and argillaceous layer, and the bedding .ne veins are mainly distributed in the sandy layer. The SiO₂ content of the horsetail-like copper ore is obviously higher than that of the weak mineralized dolomite, indicating that the bedding fine veins are developed in the quartz sandy dolomite with better permeability. The ore-bearing brine migrated to the dolomite of the Luoxue Formation along the fault structure and metasomatized to the sandy dolomite and stromatolite dolomite with high porosity on both sides, forming the Dongchuan type strati.ed copper body characterized by horsetail-like copper ore, which belongs to the brine metasomatism genesis of the basin.