Generation of andesite through partial melting of basaltic metasomatites in the mantle wedge:Insight from quantitative study of Andean andesites  

作　　者：Long Chen Yong-Fei Zheng Zheng Xu Zi-Fu Zhao 

机构地区：[1]CAS Key Laboratory of Crust-Mantle Materials and Environments,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China [2]CAS Center for Excellence in Comparative Planetology,Hefei 230026,China [3]State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China

出　　处：《Geoscience Frontiers》2021年第3期636-668,共33页地学前缘（英文版）

基　　金：supported by funds from the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(XDB41000000);the National Natural Science Foundation of China(41888101,41703025);the Fundamental Research Funds for the Central Universities(WK2080000128)。

摘　　要：Continental crust in average exhibits a similar composition in both major and trace elements to andesites along active continental margins.For this reason,andesitic magmatism above oceanic subduction zones is considered to have played a key role in the generation of continental crust along convergent plate boundaries.With respect to the origin of andesites themselves,however,there is still a hot debate on how they have acquired their geochemcial compositions.The debate is mainly centralized on the relative contributions of crustal contamination,magma differentiation and source mixing,which reaches an impasse in the past decades.The essential reason for this kind of debates is that these three mechanisms only can account for some of the geochemical observations for andesites,leading to insufficient discrimination among them.Nevertheless,the geochemical features of andesites are primarily controled from early to late by the composition of their source rocks in addition to partial melting and magma differentiation processes.If source mixing and partial melting processes in the early stage of andesite magmatism can account for the first-order geochemical features of andesites,there is no need to invoke the late processes of magma differentiation and crustal contamination for andesite petrogenesis.This is illustrated by quantitative forward modeling of the geochemical data for Quaternary andesites from the Andean arc in South America based on an integrated interpretation of these data.The modeling has run with four steps from early to late:(1)dehydration of the subducting oceanic crust at forearc depths;(2)partial melting of the subducting terrigenous sediment and altered oceanic basalt at subarc depths to produce hydrous felsic melts;(3)the generation of basaltic metasomatites(e.g.,Si-excess pyroxenite)in the mantle wedge through reaction of the mantle wedge peridotite with large amounts of the hydrous felsic melts;(4)the production of andesitic melts by partial melting of the basaltic metasomatites.The results not o

关 键 词：Andean arc ANDESITE Magma differentiation Source mixing Crust-mantle interaction 

分 类 号：P588.144[天文地球—岩石学]