安徽铜陵凤凰山燕山期中酸性侵入岩地球化学特征及其与金属成矿关系

安徽铜陵凤凰山铜矿是铜陵矿集区内最典型的矽卡岩型铜矿床之一,也是凤凰山矿田内规模最大的铜矿床。矿区内新屋里岩体属于高钾钙碱性系列,主要岩性为石英二长闪长岩和花岗闪长岩。岩石地球化学特征表明凤凰山中酸性侵入岩岩浆属于壳幔混合型,原始岩浆来源于上地幔碱性玄武岩区并有地壳物质混染,在岩浆不断演化过程中有外来物质的加入,成岩过程以混合作用为主。凤凰山铜矿体分布于岩体与大理岩的内矽卡岩带上,岩体中铜含量较高。铜矿体是岩浆期后热液交代碳酸盐地层形成的。矿体的空间分布受构造变形-岩浆侵入高温高压作用的双重控制。矿化经历了从高温矽卡岩阶段到中低温热液阶段的多期次复合成矿作用。

Geochemical characteristics of the Fenghuangshan Yanshanian intermediate-acid intrusive rocks in Tongling, Anhui Province, and their relationship with the metallogenic process

The Fenghuangshan copper deposit is the largest skarn type Cu deposit in the Tongling polymetallic (Cu, Fe, Au) ore cluster area. The Xinwuli pluton in the ore district is a Late Yanshanian high-K calc-alkaline intrusion (with U - Pb zircon age of 144 Ma), which is composed of quartz monzodiorite envelope and granodiorite interior part. Geochemical characteristics of the Xinwuli quartz monzodiorite indicate that the original magma was upper mande alkli basalt, which was contaminated by crust materials during the intrusion. Curst material contamination might have happened during partial melting or upward migration of the magma. Cu mineralization has close spatial, temporal and genetic relationship with the Xinwuli pluton. Ore bodies are hosted by both quartz monzodiorite and marble along the contact zone, with endoskarn ore bodies being dominant. Similar trace element features of ore samples and quartz monzodiotite indicate that copper might have been derived from the monzodiorite intrusion. Fluid bimetasomatism between quartz monzodiorite and carbonate rocks caused Cu precipitation. Ore bodies are joindy controlled by bimetasomatism and structural deformation in three-dimensional distribution, resulting in the distribution of breccia ores along the contact zones. The whole mineralization history can be classified into the high temperature skarn stage and the middle-low temperature hydrothermal stage.