The southeastern Brazilian onshore-offshore margin and underlying lithosphere are investigated by three-dimensional magnetotelluric imaging using 202 high-quality broadband and long-period amphibious MT-dataset, orthogonally traversing the regional surface deformation hills of Serra da Mantiqueira and Serra do Mar, as well as the coast-parallel onshore-offshore lineaments. Three-dimensional conductivity model reveals an electrically heterogeneous crust (up to 40 km) in the onshore Brasília and Ribeira Orogenic Belts, and ∼ 2–10 km thick-conductive-sedimentary-wedge beneath the offshore Santos Basin laying on top of a stretched and thinner resistive crust. Regionally, the lithosphere is found ∼130 km thick beneath the most northwestern part of the Brasília Orogenic Belt which is thinning out towards the deep-water Santos Basin (∼70 km). This thinning coincides with the lithosphere-asthenosphere boundary in recent seismic tomography results, reflecting the current state of the uplifted asthenosphere post-West Gondwana break-up. A major steeply dipping sub-lithospheric conductor, in conjunction with a confined asthenosphere upwelling (or lithospheric thinning), has been observed underneath Embu-Paraíba do Sul domain (Ribeira belt), which may be somehow associated with the continental scale rifting, surface uplift and the Cretaceous São Paulo-Rio de Janeiro dykes swarm. Our findings provide valuable insights into the formation of southeast Brazilian highlands and its association with mantle plume-induced lithospheric delamination (or removal) and the occurrence of alkaline magmatism, after reactivation of some pre-existing weak zones.

中文翻译：

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两栖大地电磁学导致巴西东南部深层岩石圈耦合的地表变形

使用 202 个高质量宽带和长周期两栖 MT 数据集，通过三维大地电磁成像对巴西东南部陆上-海上边缘和底层岩石圈进行调查，正交穿越 Serra da Mantiqueira 和 Serra do Mar 的区域表面变形山，如下所示以及与海岸平行的陆上和近海轮廓。三维电导率模型揭示了巴西利亚陆上造山带和里贝拉造山带中存在电性不均质地壳（长达 40 公里），以及位于海上桑托斯盆地下方约 2-10 公里厚的导电沉积楔形物，该楔形物位于延伸和延伸的顶部。更薄的电阻地壳。从区域上看，巴西利亚造山带最西北部分下方的岩石圈厚约 130 公里，该带向深水桑托斯盆地（约 70 公里）逐渐变薄。这种变薄与最近地震层析成像结果中的岩石圈-软流圈边界一致，反映了西冈瓦纳分裂后软流圈隆起的当前状态。在 Embu-Paraíba do Sul 区域（里贝拉带）下方观察到了一个主要的陡倾地下岩石圈导体，以及有限的软流圈上升流（或岩石圈减薄），这可能与大陆尺度裂谷、地表隆起有关以及白垩纪圣保罗-里约热内卢堤坝群。我们的研究结果为了解巴西东南部高地的形成及其与地幔柱引起的岩石圈分层（或去除）以及一些预先存在的薄弱带重新激活后碱性岩浆作用的发生的关系提供了宝贵的见解。