It is widely accepted that moderately to highly oxidized magmas are needed to form porphyry copper deposits(PCDs).However,only a few studies have attempted to investigate the effects of variable magmatic fO2 values on...It is widely accepted that moderately to highly oxidized magmas are needed to form porphyry copper deposits(PCDs).However,only a few studies have attempted to investigate the effects of variable magmatic fO2 values on the formation of PCDs.Based on previously published studies,the magma oxygen fugacity of giant PCDs is mainly concentrated betweenΔFMQ−0.5 andΔFMQ+2.5,with the first quartile,median,and third quartile being+0.8,+1.3,and+1.7,respectively.In this work,we have carried out numerical modeling,which shows that the S^(2−)used to precipitate Cu accounts for approximately 90%of total sulfur atΔFMQ+1 but drops to 33%–38%and 15%–25%atΔFMQ+2 andΔFMQ+3,respectively.This leads to a decrease of 88%–96%in Cu precipitation efficiencies fromΔFMQ+1 toΔFMQ+3.Our petrological model further shows that the maximum Cu precipitation efficiency(and,therefore,Cu endowments)occurs at aroundΔFMQ+1.We,therefore,highlight that moderately oxidized magma(ΔFMQ=∼1)rather than highly oxidized ones(ΔFMQ>∼2)is optimal for the generation of giant PCDs.展开更多
基金supported by the National Key Research and Development Program of China(2022YFC2903303)the Strategic Priority Research Program of Chinese Academy of Sciences(XDA0430301)+1 种基金the National Natural Science Foundation of China(42222206,42202104,42073047,and 42121003)the Hundred Talent Plan of the Chinese Academy of Sciences.
文摘It is widely accepted that moderately to highly oxidized magmas are needed to form porphyry copper deposits(PCDs).However,only a few studies have attempted to investigate the effects of variable magmatic fO2 values on the formation of PCDs.Based on previously published studies,the magma oxygen fugacity of giant PCDs is mainly concentrated betweenΔFMQ−0.5 andΔFMQ+2.5,with the first quartile,median,and third quartile being+0.8,+1.3,and+1.7,respectively.In this work,we have carried out numerical modeling,which shows that the S^(2−)used to precipitate Cu accounts for approximately 90%of total sulfur atΔFMQ+1 but drops to 33%–38%and 15%–25%atΔFMQ+2 andΔFMQ+3,respectively.This leads to a decrease of 88%–96%in Cu precipitation efficiencies fromΔFMQ+1 toΔFMQ+3.Our petrological model further shows that the maximum Cu precipitation efficiency(and,therefore,Cu endowments)occurs at aroundΔFMQ+1.We,therefore,highlight that moderately oxidized magma(ΔFMQ=∼1)rather than highly oxidized ones(ΔFMQ>∼2)is optimal for the generation of giant PCDs.
