深部碳循环的Mg同位素示踪:2015-2016的进展与问题  

A Review of Tracing Deep Carbon Recycling Researches by Using Mg Isotopes During 2015-2016:Progresses and Questions

作　　者：李曙光[1,2] 

机构地区：[1]中国地质大学(北京)科学研究院同位素地球化学实验室,北京100083 [2]中国科学技术大学地球与空间科学学院,合肥230026

出　　处：《矿物岩石地球化学通报》2017年第2期197-203,共7页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金资助项目(41230209)

摘　　要：镁同位素示踪深部碳循环研究在过去一年取得了很大进展。这些进展包括蚀变洋壳、沉积物、深海橄榄岩和再循环榴辉岩的Mg同位素组成,具有EM-I和HIMU同位素特征的低δ^(26)Mg玄武岩成因,低δ^(26)Mg玄武岩熔融p-t条件的Mg-Sr同位素制约,Mg同位素揭示的大陆岩石圈地幔的碳酸盐交代作用,特提斯洋俯冲板块导致的深部碳循环,和富Na碳酸盐岩浆的Mg同位素分异。然而仍有许多重要科学问题尚不清楚,包括:(1)如何区分再循环沉积碳酸盐岩和再循环碳酸盐化榴辉岩对地幔Mg同位素的影响?(2)板块俯冲过程中Mg同位素地球化学行为和为什么岛弧玄武岩没有低δ^(26)Mg特征?(3)再循环碳在地幔的储存部位及存留时间?(4)普通碳酸盐岩浆的Mg同位素如何分异?(5)如何示踪那些不含Mg或含Mg很少的再循环碳酸盐,如方解石、文石、菱铁矿?这些问题指明了未来的重要研究领域。Tracing deep carbon recycling researches by using Mg isotopes have had some significant progresses during the last calendar year（2015-2016）. Those progresses may include Mg isotopic compositions of altered oceanic crust, sediments, abyssal peridotites and recycled eclogites, origins of low δ^26Mg basalts with EM-I or HIMU isotopic features, melting p-t conditions of low δ^26Mg basalts constrained by Mg-Sr isotopes, carbonated mantle metasomatism in continental lith- osphere revealed by Mg isotopes, deep carbon recycling induced by subduction of the Tethys oceanic plate and Mg isotopes fractionation in Na-rich carbonate magma. However, several important questions remain, including： （1）How to distinguish the effects on mantle Mg isotope compositions by recycled sedimentary carbonates or by recycled carbonated eclogites？ （2）What is Mg isotopic behavior during slab subduction and why do island arc basahs have no low δ^26Mg feature？ （3）Where is the recycled carbon stored in the mantle and its residence time？ （4）How do Mg isotopes fractionate in normal carbonatite magma？ （5）How to trace the recycled carbonates that contain little Mg, such as calcite, aragonite or siderite？ To answer these questions are important in the future research.

关 键 词：深部碳 MG同位素 蚀变洋壳 沉积物 玄武岩 岩石圈地幔 特提斯构造带 碳酸岩岩浆 

分 类 号：P597[天文地球—地球化学]