The effects of local variations in conditions on carbon storage and release in the continental mantle  

作　　者：Stephen F.Foley Chunfei Chen Dorrit E.Jacob 

机构地区：[1]School of Natural Sciences,Macquarie University,North Ryde 2109,New South Wales,Australia [2]Research School of Earth Sciences,Australian National University,Canberra,AT 2601,Australia [3]State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Sciences,China University of Geosciences,Wuhan 430074,China

出　　处：《National Science Review》2024年第6期15-29,共15页国家科学评论（英文版）

基　　金：Our work on the carbon cycle is funded by the Australian Research Council(FL180100134 to S.F.F.and DP210101268 to D.E.J.).

摘　　要：Recent advances indicate that the amount of carbon released by gradual degassing from the mantle needs to be revised upwards, whereas the carbon supplied by plumes may have been overestimated in the past. Variations in rock types and oxidation state may be very local and exert strong influences on carbon storage and release mechanisms. Deep subduction may be prevented by diapirism in thick sedimentary packages, whereas carbonates in thinner sequences may be subducted. Carbonates stored in the mantle transition zone will melt when they heat up, recognized by coupled stable isotope systems (e.g. Mg, Zn, Ca). There is no single ‘mantle oxygen fugacity’, particularly in the thermal boundary layer (TBL) and lowermost lithosphere, where very local mixtures of rock types coexist. Carbonate-rich melts from either subduction or melting of the uppermost asthenosphere trap carbon by redox freezing or as carbonate-rich dykes in this zone. Deeply derived, reduced melts may form further diamond reservoirs, recognized as polycrystalline diamonds associated with websteritic silicate minerals. Carbon is released by either edge-driven convection, which tears sections of the TBL and lower lithosphere down so that they melt by a mixture of heating and oxidation, or by lateral advection of solids beneath rifts. Both mechanisms operate at steps in lithosphere thickness and result in carbonate-rich melts, explaining the spatial association of craton edges and carbonate-rich magmatism. High-pressure experiments on individual rock types, and increasingly on reactions between rocks and melts, are fine-tuning our understanding of processes and turning up unexpected results that are not seen in studies of single rocks. Future research should concentrate on elucidating local variations and integrating these with the interpretation of geophysical signals. Global concepts such as average sediment compositions and a uniform mantle oxidation state are not appropriate for small-scale processes;an increased focus on local variations will help

关 键 词：lithospheric mantle carbonate melts deep carbon cycle craton destruction continental rifts 

分 类 号：P736[天文地球—海洋地质]