全球俯冲沉积物组分及其地质意义  

The Chemical Composition of Global Subducting Sediments and Its Geological Significance

作　　者：赵仁杰 鄢全树 张海桃 关义立 葛振敏 袁龙 闫施帅 Zhao Renjie;Yan Quanshu;Zhang Haitao;Guan Yili;Ge Zhenmin;Yuan Long;Yan Shishuai(Key Laboratory of Marine Geology and Metallogeny,First Institute of Oceanography,Ministry of Natural Resources,Qingdao 266061,China;College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao 266590,China;Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266061,China)

机构地区：[1]自然资源部第一海洋研究所海洋地质与成矿作用重点实验室,山东青岛266061 [2]山东科技大学地球科学与工程学院,山东青岛266590 [3]青岛海洋科学与技术试点国家实验室海洋地质过程与环境功能实验室,山东青岛266061

出　　处：《地球科学进展》2020年第8期789-803,共15页Advances in Earth Science

基　　金：国家自然科学基金项目“科科斯脊俯冲组分及邻近大陆坡沉积物的地球化学研究及其对俯冲剥蚀机制的制约”(编号:41776070);山东省泰山学者工程项目资助.

摘　　要：俯冲沉积物在壳幔相互作用和深部地幔过程中扮演了重要角色,对汇聚板块边缘处的俯冲带岩浆成因与地幔地球化学过程也产生了重要影响。全球俯冲沉积物输入速率为0.5~0.7 km^3/a,由陆源物质(76%)、钙质碳酸盐(7%)、蛋白石(10%)以及结合水(7%)组成,化学组分与上地壳相似,主要受陆源物质影响,同时海洋过程产生的组分(生物相、热液相和自生相)会稀释陆源物质。不同海沟处的俯冲沉积物组分存在一定的差异,在增生边缘,俯冲沉积物组分与上地壳相似,而在非增生边缘海洋过程产生的组分占比增加。在俯冲过程中,随着温度和压力的增加,俯冲沉积物发生一系列化学反应,以流体、熔体或者超临界流体的形式对弧下地幔与岛弧地壳产生影响,部分俯冲沉积物与其下伏洋壳或岩石圈(俯冲残余组分)一同进入地幔(甚至是下地幔),对地幔不均一性作出贡献。地球化学示踪剂显示俯冲沉积物影响着地球不同构造背景下的岩浆过程。因此,俯冲沉积物在板块构造与地幔柱两大动力学系统中具有重要作用,通过准确计算俯冲沉积物组分,并综合运用各类地球化学指标,计算各元素或同位素的输入与输出通量,可得到更准确的俯冲残余组分,为研究地球动力学过程提供重要的基础性资料。Subducted sediments play an important role in crust-mantle interaction and deep mantle processes,especially for subduction zone magmatism and mantle geochemistry.The current rate of Global Subducting Sediments(GLOSS)is 0.5~0.7 km^3/a.The GLOSS are composed of terrigenous material(76 wt.%),calcium carbonate(7 wt.%),opal(10 wt.%)and mineral-bound H2O+(7 wt.%).The chemical compositions of GLOSS are similar to those of upper continental crust which is mainly controlled by the terrigenous materials,and yet the materials formed by marine processes will dilute the terrigenous materials.The components of subducted sediments are different among trenches.In the accretionary margin,the components of subducted sediments are similar to those of the upper crust,while in the non-accretionary margin the components are terrigenous materials plus those produced by marine processes.During subduction,subducted sediments will released fluids,melt or supercritical fluid to affect island arc/back-arc basin magmatism by means of aqueous fluid or sediment melt.In addition,a part of subducted sediments,together with underlying altered oceanic crust/lithosphere,recycle into the mantle and contribute to the mantle heterogeneity.Geochemical tracers indicate that subducted sediments play variable contributions to the magmatic processes in different tectonic setting.Thus,subducted sediments play an important role in two relatively independent dynamics systems(plate tectonics and mantle plume),as well as related mantle evolution models.As a result,by accurately calculating the compositions of subduction sediments and using various geochemical indicators,we can further limit the input and output fluxes of various elements or isotopes,and then obtain more accurately residual subducted components,which can provide us some important clues for geodynamic process.

关 键 词：俯冲沉积物输入通量 俯冲沉积物化学组分 地球动力学过程 

分 类 号：P542.5[天文地球—构造地质学]