花岗质岩浆作用及后期演化过程:来自矿物原位微区成分与同位素组成的制约  

The magmatic and post-magmatic processes of granitic magma:Constraints from in situ element and isotope compositions of minerals

作　　者：龙欣雨 唐杰[1] 许文良[1,2] LONG XinYu;TANG Jie;XU WenLiang(College of Earth Sciences,Jilin University,Changchun 130061,China;Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources,Changchun 130061,China)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]自然资源部东北亚矿产资源评价重点实验室,长春130061

出　　处：《岩石学报》2024年第3期785-810,共26页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(U2244201、42072071)资助.

摘　　要：花岗岩作为大陆地壳的重要组成部分,其岩浆作用过程一直是地学领域研究的热点。传统上利用全岩地球化学和同位素数据来示踪花岗岩成因和演化过程的方法已不够准确,为此,本文系统总结了近年来报导的花岗岩中单矿物的原位微区成分——这些数据记录了全岩数据无法识别的单矿物颗粒内部和不同矿物颗粒之间元素和同位素组成的变异特征,明显提高了对花岗质岩浆作用及后期演化过程的认识。首先,矿物原位微区成分对花岗质岩浆的源区性质和混合过程具有指示意义。花岗岩中岩浆锆石Hf同位素组成的变异可能暗示其源区在深熔作用过程中发生了锆石的不平衡和选择性熔融,而未必是壳幔混合作用的结果,这是对“锆石效应”概念新的扩展;同一花岗岩样品中分选出的磷灰石颗粒可以具有完全不同的稀土元素配分模式、Eu异常、Sr含量和Sr-Nd同位素组成等,表明它们中的部分颗粒是岩浆形成和上升过程中从围岩捕获的,是小规模地壳混染作用的产物;榍石的微区成分分带记录了多种岩浆混合过程,也反映了熔体成分、氧逸度和温度等因素的变化;花岗岩与其中发育的包体、捕虏体和相关围岩的锆石Hf-O同位素和磷灰石Sr-Nd同位素组成可以记录上述岩石在形成过程中经历岩浆混合和同化混染等作用。其次,矿物原位微区成分可以反映花岗质岩浆的分离结晶过程。岩浆成因磷灰石不同的稀土元素配分模式可能指示它们受到了其他矿物分离结晶作用的影响,如帘石族、榍石、角闪石、斜长石等;花岗伟晶岩系统中岩浆成因独居石Sm/Nd值在不同岩带中的规律性变化揭示了岩浆分离结晶程度的差异;榍石的多种微区元素含量和它们之间的协变关系受控于花岗质岩浆的结晶分异过程和氧化还原状态;岩浆成因绿帘石族矿物的震荡环带表明在绿帘石结晶的晚期阶�As an important conponent of continental crust,granitoid together with its magmatic processes have been hot issues in earth science study for a long time.The petrogenesis and evolution processes of granitoids were traditionally constrained by the whole-rock geochemical and isotopic data which become less precise at present.This paper systematically summarizes the in situ analyses data of minerals from granitoids reported in recent years which record not only the intra-but also the inter-mineral variations in elemental and isotopic compositions that are not evident from whole-rock geochemistry,and thus greatly advance the understanding of the magmatic and post-magmatic processes of granitoids.Firstly,in situ mineral composition is an indicator of source nature and mixing process of granitic magma.Significant Hf-isotope variations in magmatic zircons of granitoid may indicate a disequilibrium and preferential melting of zircon at the source,rather than a crust-mantle mixing origin,which extends the idea of“zircon effect”to crustal anataxis.The rare earth element(REE)patterns,Eu anomalies,Sr contents and Sr-Nd isotopic compositions of apatites from a single granitoid sample can be markedly different,indicating that some of the grains are captured from wall rocks during magma generation and ascent,and are products of small-scale crustal assimilation.The compositional zoning in the titanites records various magma-mixing processes and also reveals changes in melt composition,oxygen fugacity and temperature.Zircon Hf-O and apatite Sr-Nd isotopic compositions of granitoids and the enclaves/inclusions hosted in them,as well as the related wall rocks can record the magma mixing and assimilation processes during the formation of these rocks.Secondly,in situ mineral composition reflects the fractional crystallization process of granitic magma.Distinct REE patterns of magmatic apatites suggest the influence of fractional crystallization of other minerals,such as epidote-group,titanite,hornblende,and plagioclase.The regula

关 键 词：花岗岩 岩浆和岩浆期后过程 矿物原位微区成分 源区性质 分离结晶过程 变质和交代作用 

分 类 号：P588.121[天文地球—岩石学] P597[天文地球—地质学]