The role of ore metals in magmatic fluids during the magmatic-hydrothermal transition in porphyry systems remains unclear,and their contributions to porphyry ore genesis are unclear.This study offers fresh perspective...The role of ore metals in magmatic fluids during the magmatic-hydrothermal transition in porphyry systems remains unclear,and their contributions to porphyry ore genesis are unclear.This study offers fresh perspectives on the ore-forming process during this critical transition,focusing on the Hongyuan porphyry Mo(Cu) deposit(PMCD) in West Junggar,China.We find that sulfide-quartz-rich miarolitic cavities(MCs),characterized by micrographic quartz and feldspar,indicate the formation of initial mineralizing fluids from magmatic fluids.This conclusion is supported by three key observations: the simultaneous formation of feldspar and sulfides in the micrographic zones of MCs,the high formation temperatures(approaching 750 ℃) suggested by the sectorzoned bright CL cores of quartz phenocrysts,and the magmatic sulfur source indicated by the narrow sulfur isotopic composition ranges(+0.18‰ to +4.63‰).LA-ICP-MS analyses reveal distinct trace element distribution patterns between the early magmatic and transition stages and the later hydrothermal stage.Chalcopyrite from the early stages has higher Cd and lower Zn contents,while molybdenite has higher Re contents,and pyrite has higher Co and Ni contents than its counterparts in the hydrothermal stage.The decrease in sulfur concentrations at sulfide saturation from granite porphyry to micrographic quartz-feldspar melts(from 200 ppm to 100 ppm) suggests that nearly half of the sulfur was exsolved during the formation of feldspar and quartz intergrowths from fractionated granitic magma.These findings indicate that the initial mineralizing fluids of the porphyry deposit were high-temperature,melt-bearing,and ore-rich and originated from magma.The transition from initial melt-bearing,metal-rich fluids to hydrothermal ore-forming fluids is marked by decreasing temperatures and logf_(S2) values,underscoring the critical role of sulfide formation during the magmatic-hydrothermal transition in the development of porphyry deposits.展开更多
基金jointly supported by the National Natural Science Foundation of China (Nos.42272075,42302083,and 92162323)Guangdong Province Introduced Innovative R&D Team of Big Data-Mathematical Earth Sciences and Extreme Geological Events Team (No.2021ZT09H399)+1 种基金the National Key R&D Program of China (Nos.2017YFC0601201,2018YFC0604002)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University (No.22qntd2101)。
文摘The role of ore metals in magmatic fluids during the magmatic-hydrothermal transition in porphyry systems remains unclear,and their contributions to porphyry ore genesis are unclear.This study offers fresh perspectives on the ore-forming process during this critical transition,focusing on the Hongyuan porphyry Mo(Cu) deposit(PMCD) in West Junggar,China.We find that sulfide-quartz-rich miarolitic cavities(MCs),characterized by micrographic quartz and feldspar,indicate the formation of initial mineralizing fluids from magmatic fluids.This conclusion is supported by three key observations: the simultaneous formation of feldspar and sulfides in the micrographic zones of MCs,the high formation temperatures(approaching 750 ℃) suggested by the sectorzoned bright CL cores of quartz phenocrysts,and the magmatic sulfur source indicated by the narrow sulfur isotopic composition ranges(+0.18‰ to +4.63‰).LA-ICP-MS analyses reveal distinct trace element distribution patterns between the early magmatic and transition stages and the later hydrothermal stage.Chalcopyrite from the early stages has higher Cd and lower Zn contents,while molybdenite has higher Re contents,and pyrite has higher Co and Ni contents than its counterparts in the hydrothermal stage.The decrease in sulfur concentrations at sulfide saturation from granite porphyry to micrographic quartz-feldspar melts(from 200 ppm to 100 ppm) suggests that nearly half of the sulfur was exsolved during the formation of feldspar and quartz intergrowths from fractionated granitic magma.These findings indicate that the initial mineralizing fluids of the porphyry deposit were high-temperature,melt-bearing,and ore-rich and originated from magma.The transition from initial melt-bearing,metal-rich fluids to hydrothermal ore-forming fluids is marked by decreasing temperatures and logf_(S2) values,underscoring the critical role of sulfide formation during the magmatic-hydrothermal transition in the development of porphyry deposits.
