Gao Mingdi, Wang Yu, Foley Stephen F, Xu Yi-Gang
State Key Laboratory of Deep Earth Processes and Resources, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
School of Natural Sciences, Macquarie University, North Ryde, New South Wales 2109, Australia.
Sci Adv. 2025 May 23;11(21):eadu4985. doi: 10.1126/sciadv.adu4985. Epub 2025 May 21.
Slab subduction transports carbonates into the reduced, metallic iron (Fe)-bearing sublithospheric mantle (>250 kilometers), leading to heterogeneous mantle redox states and sublithospheric diamond formation beneath cratons. To elucidate the drivers of mantle redox variation, we performed mixed reaction experiments between carbonatite melt and Fe-bearing peridotite at 9 to 21 gigapascals under varying redox conditions. Comparing our results with sublithospheric diamond inclusions, we find that majorite and ferropericlase inclusions from the Amazonia Craton reflect a predominantly reduced, nonplume mantle environment, while majorites from the Kaapvaal Craton indicate a fully oxidized plume setting. In nonplume environments, carbonatite melts are progressively consumed until fully frozen as reduced carbon. Attachment of these materials to the cratonic keel further enhances craton stability. In plume environments, carbonatite melts surpass the redox buffering capacity of Fe, leading to an oxidized, CO-rich melt-bearing mantle. Impregnation of these melts into the lithosphere weakens the cratonic keel, resulting in lithosphere delamination, surface uplift, and widespread volcanism.
板片俯冲将碳酸盐输送到还原的、含金属铁（Fe）的岩石圈下地幔（深度大于250公里），导致地幔氧化还原状态的不均一性以及克拉通下方岩石圈下地幔金刚石的形成。为了阐明地幔氧化还原变化的驱动因素，我们在9至21吉帕斯卡的不同氧化还原条件下，进行了碳酸盐熔体与含铁橄榄岩之间的混合反应实验。将我们的结果与岩石圈下地幔金刚石包裹体进行比较，我们发现来自亚马孙克拉通的镁铁榴石和铁方镁石包裹体反映了一个主要为还原的、非地幔柱的地幔环境，而来自卡普瓦尔克拉通的镁铁榴石则表明是一个完全氧化的地幔柱环境。在非地幔柱环境中，碳酸盐熔体逐渐被消耗，直至作为还原碳完全固化。这些物质附着在克拉通岩基上进一步增强了克拉通的稳定性。在地幔柱环境中，碳酸盐熔体超过了铁的氧化还原缓冲能力，导致形成一个氧化的、富含CO的含熔体地幔。这些熔体侵入岩石圈会削弱克拉通岩基，导致岩石圈拆沉、地表隆升和广泛的火山活动。
