板块俯冲和岩浆过程中碳循环及深部碳储库  

Carbon cycle and deep carbon storage during subduction and magamatic processes

作　　者：张国良[1,2] 战明君[1,2,3] ZHANG Guoliang;ZHAN Mingjun(Deep Sea Research Center&Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;Center for Ocean Mega-Science,Chinese Academy of sciences,Qingdao 266071,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院海洋研究所,深海研究中心&海洋地质与环境重点实验室,青岛266071 [2]中国科学院大科学中心,青岛266071 [3]中国科学院大学,北京100049

出　　处：《海洋地质与第四纪地质》2019年第5期36-45,共10页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金项目“西太平洋板块俯冲体系岩浆过程中深部碳循环研究”(91858206),“深部碳循环对典型大洋海山链碱性玄武岩的成因制约”(41876040);中国科学院战略性先导科技专项(A类)子课题“板块俯冲有关的岩浆体系及其驱动的水岩界面过程”(XDA220500101);青岛海洋科学与技术国家实验室“海洋地质过程与环境功能实验室创新团队建设”项目(MGQNLM-TD201806)

摘　　要：地球内部可能存储了地球上大部分的碳,地球的整个地质演化历史都伴随着碳循环。岩浆过程是重要的CO2释放途径,引起地表碳的增加。板块俯冲起动之后,俯冲带成为地表碳重返地球内部的基本途径。板块俯冲和岩浆过程构成了地表过程和地球内部之间的碳循环,在地质历史时期影响着地表的碳总量,对于宜居地球环境和一些重要矿产资源的形成具有重大意义。然而,相对地表过程的碳循环而言,国际上对深部碳循环的研究程度和取得的认识远远不足。对于地球深部碳的富集机制、赋存部位,以及碳在地球内部各圈层之间的交换规律,还存在很大争议。本文对与深部碳循环密切相关的深部碳储库、岩浆中的碳组成及其对岩浆成因的影响,以及板块俯冲过程中碳行为进行了总结。结果表明,无论是洋中脊玄武岩或洋岛玄武岩,其源区CO2组成都存在高度不均一性;与地幔柱有关的深源板内火山岩相对洋中脊具有异常高的CO2组成,显示深部地幔比上地幔或软流圈更富集碳。地球的地幔转换带(410~660km)、大陆岩石圈,甚至下地幔可能是重要的碳储库。碳酸岩熔体与岩石圈橄榄岩存在化学不平衡,长期的碳酸岩熔体交代作用可能导致大陆岩石圈是个重要碳储库;地幔转换带的高压还原环境可能使得来自上涌地幔或俯冲板片中的碳以金刚石形式存储。地幔转换带或更深的碳在上涌减压过程中通过氧化还原熔融可以转化为CO2,对地幔初始熔融和板内火山岩的成因(尤其是碱性火山岩)可能具有至关重要的作用。综合认为,导致地球内部富集碳的地质作用最可能是长期板块俯冲,但是目前国内外对与板块俯冲过程相关的碳行为和碳通量估算还存在很大的不足,未来有必要针对岩浆过程的CO2活动行为、俯冲板块中碳的转化行为以及脱碳规律重点开展研究。Most of the Earth’s carbon is stored in the deep interior of the Earth,and CO2 plays a key role over the geologic history.Magmatism is a process,which releases CO2 and increases the carbon on the Earth’s surface.Plate subduction is a major process that brings Earth’s surface carbon back to its interior since its initiation globally.Therefore,plate subduction and magmatic processes constitute a deep carbon cycle between the Earth’s surface and interior.The cycle will affect the total amount of carbon of the Earth’s surface and makes contributions to the formation to the livable Earth environment and some important mineral resources.However,in contrast to the carbon cycle in the Earth’s surface system,the knowledge on deep carbon cycle is lacking.There are still controversies about the enrichment mechanism of the deep carbon,the location of its occurrence,and the exchanges of carbon among the solid Earth’s spheres.In this study,we made a thorough review on the deep carbon reservoirs,the carbon composition of magmas and its influences on the genesis of magmas,as well as the geochemical behavior of the carbon during plate subduction.It is recognized that,for the mid-ocean ridge basalts and the ocean island basalts,the CO2 compositions of their mantle sources are highly heterogeneous.Compared to the mid-ocean ridge basalts,the deeper-sourced ocean island basalts have relatively higher concentrations of carbon,indicating that the deep mantle is more enriched in carbon than the shallow upper mantle.The continental lithosphere mantle,transition zone,and even lower mantle may be important reservoirs of carbon.There is a chemical disequilibrium between the carbonated melts and the lithospheric peridotites.The continental lithosphere mantle may be an important carbon reservoir because of the long-term metasomatism of carbonated melts,and the high pressure and strong reducing environment in the mantle transition zone may cause the carbon from the upwelling mantle or subducted slab to be stored in a form of diam

关 键 词：岩浆 地幔 碳储库 金刚石 碳循环 板块俯冲 

分 类 号：P736.4[天文地球—海洋地质]