DOI: 10.1016/j.epsl.2020.116663
论文题名: Unravelling surface and subsurface carbon sinks within the early Martian crust
作者: Kissick L.E. ; Mather T.A. ; Tosca N.J.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 557 语种: 英语
中文关键词: carbonate
; experimental geochemistry
; Martian atmosphere
; Noachian Mars
; siderite
英文关键词: Carbon dioxide
; Carbon dioxide process
; Carbonates
; Carbonation
; Climate models
; Earth (planet)
; Geochemistry
; Orbits
; Pore pressure
; Supersaturation
; Temperature
; Analytical detection
; Carbonate formations
; Carbonate precipitation
; Environmental evolution
; Geochemical conditions
; Kinetically controlled
; Sedimentary records
; Spectroscopic investigations
; Iron compounds
; carbon sink
; crust
; geochemistry
; Mars
; Martian atmosphere
; precipitation (chemistry)
; siderite
英文摘要: Understanding the climate history of Mars, one of our closest planetary neighbours, has important implications for understanding the environmental evolution of Earth and other rocky planets in general. The widespread recognition of an extensive sedimentary record modified, at least in part, by liquid water holds much promise to provide evidence about Mars' past. However, unravelling the pressure and compositional history of Mars' Noachian atmosphere has remained problematic. Based on expected outgassing behaviour, observed atmospheric isotope ratios, and climate models, carbon dioxide is widely considered a main constituent of the early Martian atmosphere. If this was indeed the case, it is surprising that carbonate minerals, the expected sinks for this carbon, are only abundant in a few isolated localities across the Martian surface. Three broad possibilities may account for this apparent inconsistency: (1) carbonates formed under pCO2 higher than present but were buried, or subsequently destroyed; (2) Noachian atmospheric pCO2 was significantly lower than current estimates; or (3) low-temperature carbonate formation was kinetically controlled under the aqueous conditions that characterised much of the early Martian surface. While orbital spectroscopic investigations have yielded an increasing inventory of isolated carbonate-bearing deposits, their relative rarity at the near-surface has prompted suggestions that the Noachian atmosphere was commonly characterised by low pCO2. Without a more complete investigation of the carbonate-forming processes occurring within the ancient crust, no hypothesis can be tested robustly. Here, we examine the controls on Fe(II)-carbonate precipitation in low-temperature, anoxic water-rock systems as a function of pCO2. In experiments lasting up to 85 days, no measurable Fe(II)-carbonate precipitation occurred within the limits of analytical detection, despite significant and sustained supersaturation with respect to siderite. These observations are quantitatively consistent with recent investigations highlighting a significant supersaturation threshold for Fe(II)-carbonate nucleation. Reaction path models that incorporate these constraints indicate that Fe(II)-carbonate supersaturation thresholds would have been commonly met in low water:rock ratio systems isolated from the Noachian atmosphere as opposed to high water:rock ratio, open-systems exposed at the near surface. These results suggest the rarity of carbonates exposed at or near the surface of Mars may be controlled, at least in part, by a lack of deep crustal exposures and lack of the geochemical conditions conducive to carbonate formation, rather than insufficient atmospheric pCO2. Such geochemical constraints are in turn consistent with available orbital data indicating that carbonates may be more abundant within the deep crust, potentially representing a significant subsurface carbon sink. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165543
Appears in Collections: 气候变化与战略
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作者单位: Department of Earth Sciences, University of Oxford, Oxford, United Kingdom; National Nuclear Laboratory, Cumbria, United Kingdom; Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom
Recommended Citation:
Kissick L.E.,Mather T.A.,Tosca N.J.. Unravelling surface and subsurface carbon sinks within the early Martian crust[J]. Earth and Planetary Science Letters,2021-01-01,557