俯冲循环组分对大洋地幔不均一性的定量约束  

Quantitative Constraints of Subduction Cycle Components on Oceanic Mantle Heterogeneity

作　　者：胡航 余星 韩喜球 Hu Hang;Yu Xing;Han Xiqiu(Key Laboratory of Submarine Geosciences&Second Institute of Oceanography,Ministry of Natural Resources,Hangzhou 310012,China;School of Oceanography,Shanghai Jiao Tong University,Shanghai 200240,China)

机构地区：[1]自然资源部第二海洋研究所自然资源部海底科学重点实验室,浙江杭州310012 [2]上海交通大学海洋学院,上海200240

出　　处：《地球科学》2022年第7期2616-2630,共15页Earth Science

基　　金：国家自然科学基金项目(Nos.42172231,41872242);大洋“十三五”资源环境专项(No.DY135-S2-1-02);自然资源部第二海洋研究所基本科研业务费专项(Nos.JT2001,JG2001)。

摘　　要：大洋地幔内部存在广泛的不均一性,其成因可有多种模式,其中俯冲循环作用对地幔组成的变化具有重要影响.为明确各循环组分对亏损地幔的改造作用及其在富集源区中的相对贡献,系统总结了不同循环组分(远洋沉积物、俯冲洋壳、陆壳)的平均微量元素特征,计算了各循环组分在俯冲过程中经历的化学变化.基于改造后的循环组分,开展与亏损地幔源区的混合和熔融模拟.结果表明,HIMU型玄武岩可以由纯俯冲洋壳(≤10%)与亏损地幔(≥90%)混合形成的源区,经较低程度熔融(0.5%~1.5%)形成;而EMI型玄武岩可以由俯冲洋壳(≤10%)、俯冲剥蚀的下陆壳物质(≤3%)、亏损地幔(≥90%)混合形成的源区,经较低程度熔融(1%~2%)形成;EMII型玄武岩可以由俯冲洋壳(≤10%)、GLOSS-II(全球俯冲沉积物)或上陆壳物质(≤0.8%)与亏损地幔(≥90%)混合形成的源区,经较低程度熔融(1%~1.5%)形成.There is a wide range of heterogeneity in the oceanic mantle,which can be caused by a variety of models,among which the subduction cycle has an important influence on the composition of the mantle.In order to clarify the relative contribution of each cyclic component to the reformation of depleted mantle and the enrichment source region,in this paper it systematically summarizes the average trace element characteristics of different cyclic components(pelagic sediments,subducted oceanic crust,continental crust),and the cyclic components undergone chemical changes during subduction are calculated.Based on the modified cyclic components,the mixing and melting simulations with depleted mantle sources are carried out.It is found that the HIMU basalt can be formed by a low degree of melting(0.5%-1.5%) in the mantle formed by the mixing of pure subducted oceanic crust(≤10%) and depleted mantle(≥90%).The EMI basalts can be formed by a low degree of melting(1%-2%) in the mantle formed by the mixing of subducted oceanic crust(≤10%),low continental crust(≤3%) and depleted mantle(≥90%).The EMII basalts can be formed by a low degree of melting(1%-1.5%) in the mantle formed by the mixing of subducted oceanic crust(≤10%),GLOSS-II(global subducting sediment) or upper continental crust(≤0.8%) and depleted mantle(≥90%).

关 键 词：地幔不均一性 俯冲洋壳 俯冲沉积物 亏损地幔 部分熔融 地球化学 

分 类 号：P542[天文地球—构造地质学]