Genesis of Volcanic Rocks in the Zijinshan Ore District, SE China: Implications for Porphyry-Epithermal Mineralization

摘要: Volcanic rocks, as the extrusive counterparts of mineralized intrusions, can provide important information on magma source, petrogenesis, and metallogenic conditions coeval porphyry-epithermal system. Shanghang Basin volcanic rocks are spatially temporally related to a series adjacent Cu–Au deposits, they be used window study deposits. Two laser-ablation–inductively coupled plasma–mass spectrometry zircon U–Pb analyses yield weighted mean ages ~105 Ma, identical age mineralization. Rocks have SiO2 contents 55.4 74.8 wt % belong high-K shoshonitic series, characterized by strong differentiation light rare-earth elements (REEs) relative heavy REEs (mean LaN/YbN = 16.88); enrichment in REEs, Rb, Th, U; depletion Nb, Ta, Zr, Hf, Ti. The display (87Sr/86Sr)i values 0.709341 0.711610, eNd(t) −6.9 −3.3 eHf(t) −3.95 −0.30, δ18O 6.07‰–6.79‰, suggesting that parental magmas were derived from mantle source enriched subduction-related progress. content shows negative correlation with some major trace elements, indicating fractional crystallization played an role generation these rocks. A binary mixing model Hf–O isotopes gives estimated degree crustal contamination 30%. In addition, magnetite crystallized early, samples showed high EuN/EuN* (0.48–0.68), had oxygen fugacity. inferred suppression plagioclase increasing hornblende during evolution suggest was water rich. high-water fugacity promoted dissolving sulfides containing Cu Au area contributed migration ore-forming elements.