钾同位素的高精度分析及深部过程的示踪应用  

High precision potassium isotope analysis and its application in tracing deep-earth processes

作　　者：顾海欧 刘倩 孙贺 顾笑龑 汪方跃[1,2] GU Haiou;LIU Qian;SUN He;GU Xiaoyan;WANG Fangyue(School of Resources and Environmental Engineering,Hefei University of Technology,Hefei,Anhui 230009,China;Ore Deposit and Exploration Center(ODEC),Hefei University of Technology,Hefei,Anhui 230009,China;School of Earth Science,Zhejiang University,Hangzhou,Zhejiang310027,China)

机构地区：[1]合肥工业大学资源与环境工程学院,安徽合肥230009 [2]合肥工业大学矿床成因与勘查技术研究中心,安徽合肥230009 [3]浙江大学地球科学学院,浙江杭州310027

出　　处：《地质学报》2022年第12期4331-4339,共9页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号91962218);中央高校基本科研业务费专项资金(编号JZ2021HGTB0110,PA2021KCPY0047)联合资助的成果。

摘　　要：钾(K)是主要造岩元素之一,高水溶性,高活动性,同时具有高度的不相容性。尽管K同位素组成的测试始于20世纪初,但其高精度测试一直发展缓慢,直到近年来得益于多接收电感耦合等离子体质谱(MC-ICPMS)的快速发展,K同位素的分析精度得到显著提升,极大地促进了K同位素地球化学的发展。目前已经基本查明地球各主要储库的K同位素组成,并对一些地质和物理化学过程中的K同位素分馏开展了研究工作。研究结果表明海水的K同位素组成(均值0.11‰±0.08‰)显著高于硅酸盐地球的K同位素组成(估计值-0.44‰±0.04‰);而主要地质过程中,低温风化过程中风化壳一般富集轻的同位素,而与之平衡的水体富集重的同位素;高温岩浆分异过程中目前尚未观察到显著的同位素分馏。目前K同位素已经被广泛应用于俯冲循环地壳物质或板片流体活动的示踪上,如幔源岩浆的地幔源区过程示踪等。由于浅部物质的K含量远高于地幔源区,在俯冲循环过程中,地幔源区的K同位素组成对于交代、混染等过程比较敏感。因此,K同位素在示踪地幔组成变化方面可能会具有广阔的应用前景。As a major rock-forming and highly incompatible element,potassium(K)is highly water-soluble and highly mobile.In recent years,the rapid development of multi-collector inductively coupled plasma-mass spectrometry(MC-ICP-MS)has greatly promoted the development of K isotopes due to the breakthrough of high precision K isotopic measurement.Till now,the K isotopic compositions of the major terrestrial reservoirs have been investigated,and behaviors of K isotopes during some geological and physicochemical processes have been studies.The results indicated that the K isotopic composition of seawater(averaging in 0.11‰±0.08‰)is obviously heavier than bulk silicate earth(BSE,estimated in-0.44‰±0.04‰).Large K isotopic fractionation occurs during continental weathering with light K isotopes retained in the weathered products and heavy K isotopes released into the water.And the fractionation during magmatic differentiation is limited.K isotopes have been used to trace the subducted crustal material in the mantle source of mantle-derive magmas.Since the K content of crustal materials is much larger than that of the mantle,K isotope is very sensitive to the metasomatism or assimilation processes in the mantle during the subduction processes.Thus,it is believed that K isotope would open new horizons to crust-mantle processes.

关 键 词：K同位素 MC-ICP-MS 地质储库 高温地球化学 壳幔相互作用 地质示踪 

分 类 号：P597[天文地球—地球化学]