摘要
本文对榴辉岩部分熔融过程中不同同位素体系是否存在分馏这一当前研究热点进行了综述。榴辉岩作为研究洋陆俯冲、超高压变质以及壳幔相互作用的主要岩石类型,其部分熔融与地壳增生、板片折返过程以及俯冲隧道中元素的迁移分配等具有紧密的联系。作为典型的高压-超高压变质岩石,榴辉岩可通过俯冲带将壳源信息携带至地幔深部,影响地幔的化学组成,并可在大洋玄武岩中得以表现。近些年,随着仪器分析技术的发展,实验研究和理论计算均表明榴辉岩部分熔融过程中稳定同位素可以产生显著的分馏。作为常见的放射性成因子体同位素和传统稳定同位素Sr-Nd-Hf-O被广泛应用于源区示踪、岩浆混合以及结晶分异等过程。但目前有研究指出,在非平衡熔融过程中,熔体和源区的Sr-Nd-Hf-O同位素可发生解耦,导致二者的同位素组成不均一。另外,通过研究榴辉岩及其熔融产物的金属稳定同位素特征,发现榴辉岩部分熔融过程中,由于石榴石效应,会造成Ca、Mg、Fe、Li等金属稳定同位素的分馏。因此,当利用稳定同位素示踪榴辉岩熔体的源区时,需要考虑其分馏的影响。
In this paper,we reviewed the isotope fractionation during partial melting of eclogite.Eclogite is the main rock for studying the oceanic/continental subduction,ultrahigh pressure metamorphism and crust-mantle interaction.Its anatexis is closely associated with crust formation,mechanism for slab exhumation as well as elements migration and distribution in subduction channel.As a typical high pressure-ultrahigh pressure metamorphic rock,the eclogite can change the chemical composition of mantle by carrying the crustal information through the subduction zone,which can be reflected by the ocean island basalts that bring out the above clues.In recent years,with the development of instrumental analysis techniques,both experimental studies and theoretical calculation show that stable isotopes can produce significant fractionation during partial melting of eclogite.Sr,Nd and Hf are the common radiogenic daughter isotopes,while O is a traditional stable isotope.They are widely used in source tracing,magma mixing and fractional crystallization etc.However,some researches point out there maybe the Sr-Nd-Hf-O isotopes decoupling between the sources and melts during disequilibrium melting.In addition,by studying the stable isotope characteristics of eclogite and its melting products,we found some metal stable isotopes,like Ca,Mg,Fe and Li may fractionate significantly due to the"garnet effect".Therefore,we should pay extra attention when using stable isotopes to track the sources.
作者
刘帅奇
张贵宾
LIU ShuaiQi;ZHANG GuiBin(Key Laboratory of Orogenic Belt and Crustal Evolution,MOE,School of Earth and Space Science,Peking University,Beijing 100871,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2021年第1期95-112,共18页
Acta Petrologica Sinica
基金
国家自然科学基金项目(91755206、41972056、41622202)
国家重点研发计划项目(2017YFC0601302)联合资助.
