Abstract This contribution investigates mechanisms controlling subduction development and stabilization over time (coined as 'slabitization'), from a nascent slab to a mature slab viscously coupled to mantle convection, from grain scale to plate tectonics scale. Frozen-in, deep and warm portions of the subduction plate interface with both sides still preserved are found at the base of ophiolites in almost pristine state. Both sides record changes in the mineralogy, structure, fluid content and rheology due to devolatilization of subducting metamorphic rocks. They allow characterizing the evolution, shortly after subduction initiation (~1–10 Ma), of interplate coupling, mantle resistance to slab penetration or incipient mantle wedge metasomatism, as well as transformations occurring at depth in warm or cold subduction zones today. This study combines structural field work, mineralogical and crystallographic data, detailed petrology, thermodynamic modelling and geochemistry from/on both sides of the plate interface, i.e. the base of the mantle wedge (basal ophiolitic peridotites) and crustal fragments from the slab (metamorphic soles). Data collected across the entire Semail ophiolite (Oman, UAE territory) and other similar settings worldwide (e.g., Canada, Turkey, New Caledonia) show a continuous evolution of the subduction plate interface from 1.2–0.9 GPa 900–750 °C to 0.7–0.5 GPa 750–600 °C, with progressive localization of strain and fluid transfer. Crystallization of neo-formed minerals, enrichment in fluid-mobile elements and their isotopic signature (e.g., for boron) indicate that metasomatism of the mantle base results from interaction with subduction fluids derived from the dehydrating metamorphic sole and slab tip, migrating at velocities ~1–10 m/a. Coeval deformation and metamorphic reactions in metabasalts of the downgoing slab reveal the importance of mineral changes (e.g., amphibole content) and deformation modes in controlling fluid delivery, stepwise detachment and accretion of successive slices from the downgoing slab (HTa, HTb and then LT soles) to the mylonitized mantle. This study demonstrates how the interplay between metamorphic reactions, fluid/melt transfer and deformation mechanisms, in particular dissolution-precipitation creep (DPC), controls the mechanical coupling state of the plate interface: (i) suppression of fluid transfer and DPC at depth triggers the onset of viscous coupling. This occurs near ~ 30 km depth during subduction infancy and HTa sole formation; (ii) with increased cooling and fluid availability, strain localization progressively develops downwards and unzips the subduction interface. The downward migration of viscous coupling triggers localized mantle wedge upwelling, potentially leading to short-lived suprasubduction ophiolite or forearc lithosphere formation; (iii) the locus of viscous coupling stabilizes near ~80–100 km in mature (and cold) subduction zones, and sets mantle counterflow. This is where and when plates get reattached and slabs become part of the mantle convection system. Recent geochronological data suggest that the duration from subduction nucleation to ophiolite formation is probably slower than suspected (~5–10 Ma), and that another 5–10 Ma may be needed to reach mature subduction and profuse arc magmatism. These results refine our view of the subduction factory and have important implications for how, how much, and which sort of fluid is being fluxed into the mantle wedge at depths where serpentine is no longer stable.

中文翻译：

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Slabitization：控制俯冲发展和粘性耦合的机制

摘要 本论文研究了随着时间的推移控制俯冲发展和稳定（称为“slabitization”）的机制，从新生板块到与地幔对流粘性耦合的成熟板块，从颗粒尺度到板块构造尺度。在蛇绿岩的底部发现了几乎原始状态的俯冲板块界面的冰冻、深部和温暖部分，两侧仍然保留。双方都记录了俯冲变质岩脱挥发分引起的矿物学、结构、流体含量和流变学的变化。它们允许表征在俯冲开始（~1-10 Ma）后不久的板间耦合、地幔对板片穿透或初期地幔楔交代作用的抵抗力的演化，以及今天在暖或冷俯冲带深处发生的转变。这项研究结合了来自板块界面两侧的构造野外工作、矿物学和晶体学数据、详细的岩石学、热力学模型和地球化学，即地幔楔底部（基底蛇绿橄榄岩）和板块（变质底部）的地壳碎片）。在整个 Semail 蛇绿岩（阿曼、阿联酋领土）和全球其他类似环境（例如加拿大、土耳其、新喀里多尼亚）收集的数据显示，俯冲板块界面从 1.2-0.9 GPa 900-750 °C 持续演变为 0.7- 0.5 GPa 750–600 °C，逐渐定位应变和流体转移。新形成矿物的结晶，流体流动元素的富集及其同位素特征（例如，硼）表明地幔底部的交代作用是与来自脱水变质底部和板片尖端的俯冲流体相互作用的结果，以~1-10 m / a的速度迁移。下行板片变玄武岩的同时变形和变质反应揭示了矿物变化（例如角闪石含量）和变形模式在控制流体输送、逐步脱离和下行板片连续切片（HTa、HTb 和 LT 底部）中的重要性) 到糜棱化地幔。本研究展示了变质反应、流体/熔体转移和变形机制之间的相互作用，特别是溶解-沉淀蠕变 (DPC)，如何控制板界面的机械耦合状态：(i) 在深度处抑制流体转移和 DPC 触发粘性耦合的发生。这发生在俯冲初期和 HTa 唯一形成期间约 30 公里深度附近；(ii) 随着冷却和流体可用性的增加，应变局部化逐渐向下发展并解开俯冲界面。粘性耦合的向下迁移触发局部地幔楔上涌，可能导致短寿命的超俯冲蛇绿岩或弧前岩石圈的形成；(iii) 在成熟（和冷）俯冲带中，粘性耦合的轨迹稳定在~80-100 公里附近，并设置地幔逆流。这是板块重新连接的地方和时间，板块成为地幔对流系统的一部分。最近的地质年代学数据表明，从俯冲成核到蛇绿岩形成的持续时间可能比推测的要慢（~5-10 Ma），并且可能需要另外 5-10 Ma 才能达到成熟的俯冲和丰富的弧岩浆作用。这些结果完善了我们对俯冲工厂的看法，并对在蛇纹石不再稳定的深处流入地幔楔的方式、数量和种类具有重要意义。