The thermochemical structure of the lithosphere controls melting mechanisms in the mantle, as well as the location of volcanism and ore deposits. Obtaining reliable images of the lithosphere structure, and its complex interactions with the asthenosphere, requires the joint inversion of multiple data sets and their associated uncertainties. In particular, the combination of seismic velocity and electrical conductivity, along with proxies for bulk composition and elusive minor phases, represents a crucial step toward fully understanding large-scale lithospheric structure and melting processes. We apply a novel probabilistic approach for joint inversions of 3D magnetotelluric and seismic data to image the lithosphere beneath southeast Australia. The results show a highly heterogeneous lithosphere with deep conductivity anomalies that correlate with the location of Cenozoic volcanism. In regions where the conductivities have been at odds with sub-lithospheric temperatures and seismic velocities, we observe that the joint inversion provides conductivity values consistent with other observations. The results reveal a strong relationship between metasomatized regions in the mantle and (a) boundaries of geological provinces, elucidating the subduction-accretion process in the region; (b) distribution of leucitite and basaltic magmatism; (c) independent geochemical data, and (d) a series of lithospheric steps which constitute areas prone to generating small-scale instabilities in the asthenosphere. This scenario suggests that shear-driven upwelling and edge-driven convection are the primary mechanisms for melting in eastern Australia, contrary to the conventional notion of mantle plume activity. Our study presents an integrated lithospheric model for southeastern Australia and provides valuable insight into the mechanisms driving surface geological processes.

中文翻译：

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澳大利亚东南部岩石圈结构和融化过程：3D 大地电磁和地震数据联合概率反演的新约束

岩石圈的热化学结构控制着地幔的熔化机制以及火山活动和矿床的位置。要获得岩石圈结构及其与软流圈复杂相互作用的可靠图像，需要联合反演多个数据集及其相关的不确定性。特别是，地震速度和电导率的结合，以及整体成分和难以捉摸的次要相的代理，代表了全面理解大规模岩石圈结构和熔化过程的关键一步。我们应用一种新颖的概率方法对 3D 大地电磁和地震数据进行联合反演，对澳大利亚东南部下方的岩石圈进行成像。结果显示，岩石圈高度不均匀，具有深层电导率异常，与新生代火山活动的位置相关。在电导率与次岩石圈温度和地震速度不一致的区域中，我们观察到联合反演提供了与其他观测结果一致的电导率值。结果揭示了地幔交代区域与地质省边界之间的密切关系，阐明了该区域的俯冲-增生过程；(b) 白榴石和玄武岩岩浆的分布；(c) 独立的地球化学数据，以及 (d) 一系列岩石圈台阶，这些台阶构成了容易在软流圈中产生小规模不稳定的区域。这种情况表明，剪切驱动的上升流和边缘驱动的对流是澳大利亚东部融化的主要机制，这与地幔柱活动的传统概念相反。我们的研究提出了澳大利亚东南部的综合岩石圈模型，并为驱动地表地质过程的机制提供了宝贵的见解。