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

Abstract：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 mantle 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 jointly 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.