摘要
全球碳循环研究对于理解现今及未来大气圈CO2浓度及其变化趋势至关重要。传统的碳循环研究多侧重于探讨碳元素在大气圈、水圈、生物圈等地球表层之间的循环过程,基本不讨论地球内部圈层碳元素地球化学的行为与循环,现在发现传统的研究方式已很难深刻认识大气圈CO2浓度变化的规律。探讨地球内部与表层碳元素双向交换过程的深部碳循环研究应运而生,成为当前全球碳循环研究的主要方向。火成碳酸岩主要由碳酸盐矿物所组成,是地球内部碳元素含量最高的岩石,因而成为深部碳循环研究的主要对象之一。当前的研究发现,相当一部分火成碳酸岩中的碳来自大气圈的CO2,是再循环的碳。地表附近消耗大气CO2所新生成的沉积碳酸盐岩借助板块深俯冲作用被带入地球内部,在(超)高温和含水条件下发生部分熔融作用,形成碳酸岩浆,后者再上侵形成火成碳酸岩,或者直接喷发至地表,碳元素又重返地球表层。因此,地球内部的构造运动主导碳元素在地球表层与内部的循环过程,进而控制大气圈CO2浓度长周期变化的趋势。
The knowledge of global carbon cycle is critical to understanding of today＇s atmospheric CO2 contents and varying of atmospheric CO2 contents in the future.Conventional researches of global carbon cycle focus mainly on the carbon cycling among atmosphere,hydrosphere,and biosphere at Earth＇s surface.Carbon reservoirs and carbon geochemical cycling within Earth＇s interior had hardly studied in the past.At present these conventional research methods have hardly illustrated the evolution of CO2 contents of atmosphere.Deep carbon research,aiming at the carbon two-way exchanging between Earth＇s interior and surface,became a current research hot-spot.Carbonatites are mainly made up of carbonate minerals and are the rocks of highest content of carbon within Earth＇s interior.Therefore,carbonatites are the target of deep carbon cycling research.Current studies are further revealed that carbon from most carbonatites worldwide is from atmospheric CO2,and thus,is recycling carbon.New formation of carbonate-bearing sedimentary rocks at surface,at the expense of huge atmospheric CO2,were transferred into Earth＇s interior through subduciton zones,which were experienced（ultra）high-temperature metamorphism under water conditions,and subsequently partial melting to form carbonate magmas within Earth＇s interior.The new carbonate magmas moved upwards into upper crust,or even at surface,to form carbonatites.Carbon could go back to Earth＇s surface.Therefore,the carbon cycling between Earth＇s surface and interior was controlled by tectonic movements.Moreover,the long-term varying of atmospheric CO2 contents is mainly driven by global tectonic activities.
出处
《自然杂志》
北大核心
2012年第4期201-207,共7页
Chinese Journal of Nature
