The Parnaíba Basin, in northeastern Brazil, is one of the most significant intracratonic basins on the South American platform. Its formation, driven by vertical thermal and mechanical processes has been extensively studied, however, the internal structural configuration remains subject of debate. Magnetotellurics (MT) is a geophysical method that provides information about the geo-electric internal distribution. As part of the multi-physics Parnaíba Basin Analysis Project (PBAP), 218 broadband and 37 long-period MT stations were deployed along an E-W transect profile of ∼1400km. The MT data were inverted to produce 3-D resistivity models. Lateral resistivity variations were identified along the profile and interpreted as the amalgamation of the three blocks, from west to east: Amazonian Craton, Parnaíba block, and Borborema Province. Within each block, the models reveal differentiated geoelectric behaviours. The Amazonian Craton exhibits a high-conductivity domain associated with the replacement of a delaminated lithosphere. The Parnaíba block comprises two distinct tectonic domains: the resistive Grajaú block and the conductive Teresina block. Their resistivity contrast is associated with magmatic activity, which is more intense in Teresina. However, Cretaceous extensional events related to the opening of the South Atlantic may have also influenced it. In the Borborema Province, resistive and conductive signatures at lower crustal depth are identified, providing evidence of collisional events associated with its formation in the Neoproterozoic. These deep resistivity models provide new evidence for the crustal amalgamation of the Parnaíba Basin and offer insights into the tectonic processes that shaped Western Gondwana.

中文翻译：

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Parnaíba 盆地的大地电磁成像：对西冈瓦纳地层的影响

位于巴西东北部的帕尔奈巴盆地是南美平台上最重要的克拉通盆地之一。它由垂直热和机械过程驱动的形成已被广泛研究，然而，内部结构配置仍然存在争议。大地电磁学 （MT） 是一种地球物理方法，可提供有关地电内部分布的信息。作为多物理场帕尔奈巴盆地分析项目 （PBAP） 的一部分，沿 ∼1400 公里的东-西样带剖面部署了 218 个宽带站和 37 个长周期 MT 站。对 MT 数据进行反演以生成 3-D 电阻率模型。沿剖面确定了横向电阻率变化，并将其解释为三个区块的合并，从西到东：亚马逊克拉通、帕尔奈巴区块和博尔博雷马省。在每个块中，模型揭示了不同的地电行为。亚马逊克拉通表现出与分层岩石圈的替换相关的高电导性结构域。Parnaíba 区块由两个不同的构造域组成：电阻 Grajaú 区块和导电 Teresina 区块。它们的电阻率对比与岩浆活动有关，而岩浆活动在 Teresina 中更为强烈。然而，与南大西洋开放有关的白垩纪伸展事件也可能影响了它。在 Borborema 省，在较低的地壳深度发现了电阻和导电特征，为新元古代与其形成相关的碰撞事件提供了证据。这些深电阻率模型为 Parnaíba 盆地的地壳合并提供了新证据，并为塑造西冈瓦纳的构造过程提供了见解。