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Mantle degassing related to changing redox and thermal conditions during the Precambrian supercontinent cycle
Precambrian Research ( IF 3.2 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.precamres.2020.105895
Zhensheng Wang , Yongsheng Liu , Keqing Zong , Jie Lin , Timothy M. Kusky

Abstract The C-O-H cycling of the early shallow Earth is suggested to be closely related to mantle degassing and speciation processes. These processes are influenced by the mantle’s thermal and redox states, which have changed significantly in different mantle reservoirs during Earth’s protracted history. However, the link between speciation of C-O-H magmatic volatiles and the temporal changes of the mantle’s thermal and redox states in different mantle reservoirs remains elusive. We test this link through chemical equilibrium modeling of C-O-H magmatic volatiles to assess its influences on shallow C-O-H cycling and the oxidization history of the shallow Earth. We find that a rapid oxidization of Archean mantle related to recycling of oceanic crust, core-mantle material exchange, or evolution of primitive mantle redox heterogeneities can strongly reduce the fraction of reducing compositions (e.g., H2 and CH4) in volcanic gases, which then consumed less photosynthetic oxygen, leading to a net increase of atmospheric oxygen and triggering the Great Oxidation Event (GOE) at 2.4-2.3 Ga. After the GOE, mantle degassing at rifts, mid ocean ridges, and plumes became more oxidizing and thus triggered later atmospheric oxidation synchronous with supercontinent breakup. Our results support that the oxidation of the atmosphere in the Precambrian was influenced by mantle oxidation, upwelling and/or degassing, especially during the GOE.

中文翻译:

与前寒武纪超大陆循环中氧化还原和热条件变化有关的地幔脱气

摘要 早期浅地球的COH循环被认为与地幔脱气和物种形成过程密切相关。这些过程受地幔热状态和氧化还原状态的影响,在地球漫长的历史中,这些状态在不同的地幔储层中发生了显着变化。然而,COH岩浆挥发物的物种形成与不同地幔储层中地幔热和氧化还原状态的时间变化之间的联系仍然难以捉摸。我们通过 COH 岩浆挥发物的化学平衡模型来测试这种联系,以评估其对浅层 COH 循环和浅层地球氧化历史的影响。我们发现太古代地幔的快速氧化与洋壳的再循环、核-地幔物质交换、或原始地幔氧化还原异质性的演化可以强烈减少火山气体中还原成分(例如 H2 和 CH4)的比例,然后消耗较少的光合氧,导致大气氧的净增加并引发大氧化事件(GOE)在 2.4-2.3 Ga。GOE 之后,裂谷、洋中脊和羽流的地幔脱气变得更加氧化,从而引发了与超大陆破裂同步的后期大气氧化。我们的结果支持前寒武纪大气氧化受地幔氧化、上升流和/或脱气的影响,尤其是在 GOE 期间。导致大气氧的净增加并在 2.4-2.3 Ga 触发大氧化事件 (GOE)。GOE 之后,裂谷、洋中脊和羽流处的地幔脱气变得更加氧化,从而引发后来与超大陆同步的大气氧化分手。我们的结果支持前寒武纪大气氧化受地幔氧化、上升流和/或脱气的影响,尤其是在 GOE 期间。导致大气氧的净增加并在 2.4-2.3 Ga 触发大氧化事件 (GOE)。GOE 之后,裂谷、洋中脊和羽流处的地幔脱气变得更加氧化,从而引发后来与超大陆同步的大气氧化分手。我们的结果支持前寒武纪大气氧化受地幔氧化、上升流和/或脱气的影响,尤其是在 GOE 期间。
更新日期:2020-11-01
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