Crustal magma oxidation state and endowments in porphyry copper deposits  

作　　者：Yumin AI Massimo CHIARADIA Chao WU Huayong CHEN 

机构地区：[1]Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou,510640,China [2]University of Chinese Academy of Sciences,Beijing,100049,China [3]Department of Earth Sciences,University of Geneva,Geneva,1205,Switzerland [4]Guangdong Provincial Key Laboratory of Mineral Physics and Materials,Guangzhou,510640,China

出　　处：《Science China Earth Sciences》2025年第1期226-236,共11页中国科学(地球科学英文版)

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.41921003,42230810,41902089);the Science and Technology Planning Project of Guangdong Province,China(Grant No.2023B1212060048);the Guangzhou Basic and Applied Basic Research Subject(Young Doctor Sailing Project)(Grant No.2024A04J4828)。

摘　　要：Porphyry copper deposits(PCDs)supply the majority of the world's copper(Cu)as well as significant amounts of molybdenum(Mo)and gold(Au).The formation of these deposits is controlled by a variety of geological factors,among which the magmatic oxidation is one of the focuses of current research.This study investigates the redox characteristics of arc magmas by analyzing the ratio of vanadium(V)to scandium(Sc)and its correlation with the oxygen fugacity(fO2)of magmas from arcs of various crustal thicknesses globally.We compiled an extensive dataset of published V/Sc values and studied the partition coefficients of Vand Sc between minerals and silicate melts across various magmatic environments.The results demonstrate that fractional crystallization of magnetite markedly reduces V/Sc values of the residual melt.Furthermore,magnesium number(Mg#)at the onset of magnetite fractionation is strongly positively correlated with fO_(2)of the equilibrium magma.Based on this,the oxidation of arc magmas from different crustal thicknesses can be evaluated.The result suggests that magmas generated in crusts thicker than 20 km tend to be more oxidized with increasing crust thickness.This trend is attributed to enhanced intracrustal differentiation processes involving garnet and amphibole,particularly in mature island and continental arcs.In contrast,magmas in thinner arc crusts(<20 km),which are significantly influenced by subducted slab materials,display higher oxidation states than most of their thicker crust counterparts.These findings suggest that both subduction dynamics and crustal thickness play a vital role in determining the oxidation state of arc magmas and,consequently,their capacity to generate PCDs.Highly oxidized,primitive arc magmas are less favorable for PCD formation due to that they tend to experience magnetite fractionation and thus sulfide saturation in the early stage of magma evolution,a process leading to copper depletion.On the contrary,thick arcs where magnetite crystallization is widely suppressed and the

关 键 词：Magma evolution V/Sc systematics MAGNETITE Oxygen fugacity Porphyry copper deposits 

分 类 号：P618.41[天文地球—矿床学]