Enhanced metamorphic CO2 release on the Proterozoic Earth

• 成果类型: Article
• 署名作者: Stewart, E. M.; Penman, Donald E.
• 署名单位: State University System of Florida; Florida State University; Utah System of Higher Education; Utah State University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-15350
• DOI: 10.1073/pnas.2401961121
• 发表日期: 2024-10-01
• 关键词: faint young sun; carbon-cycle; EVOLUTION; fluxes; constraints; dolomite; sediment; feedback; HISTORY; climate

摘要

Rock metamorphism releases substantial CO2 over geologic timescales (>1 My), potentially driving long-term planetary climate trends. The nature of carbonate sediments and crustal thermal regimes exert a strong control on the efficiency of metamorphic CO2 release; thus, it is likely that metamorphic CO2 degassing has not been constant throughout time. The Proterozoic Earth was characterized by a high proportion of dolomite-bearing mixed carbonate-silicate rocks and hotter crustal regimes, both of which would be expected to enhance metamorphic decarbonation. Thermodynamic phase equilibria modeling predicts that the metamorphic carbon flux was likely similar to 1.7 times greater in the Mesoproterozoic Era compared to the modern Earth. Analytical and numerical approaches (the carbon cycle model PreCOSCIOUS) are used to estimate the impact this would have on Proterozoic carbon cycling and global atmospheric compositions. This enhanced metamorphic CO2 release alone could increase pCO(2) by a factor of four or more when compared to modern degassing rates, contributing to a stronger greenhouse effect and warmer global temperatures during the expansion of life on the early Earth.