Compiled potential field data and seismic surveys across the Eastern Brazilian continental margin integrated with new magnetometric profiles and stratigraphic configuration for Trindade Island, South Atlantic, Brazil

This work discusses the regional geological and geophysical datasets (potential field data coupled with seismic lines) available across the Eastern Brazilian Continental Margin and addresses tectonic models that have been applied to the geological interpretation of the Vitória-Trindade Chain (VTC). New magnetic data acquired in the Trindade Island is combined with compiled petrological data and geological maps to propose a stratigraphic column with radiometric control for the volcanic sequences. The gravity and magnetic anomaly maps were integrated with regional seismic profiles extending from the continental platform towards the oceanic crust, showing the geomorphology of the Abrolhos Volcanic Complex (AVC) and the VTC. A detailed geological mapping of the Trindade Island was complemented by magnetometric profiles acquired on the island. The magmatic episodes identified in the Trindade Island within different volcano-stratigraphic sequences are, geochronologically, dated by ⁴⁰Ar/³⁹Ar method as Late Neogene to Quaternary (Pliocene/Upper Pleistocene) and indicate intrusive and extrusive igneous rocks formed on the Mesozoic (Cretaceous) oceanic crust. Models for the emplacement of these volcanic rocks on much older oceanic crust include hotspots and leaking fracture zones. The presence of flat tops as observed in the volcanic banks and seamounts along the Vitória-Trindade volcanic chain indicate abrasion of much higher volcanic edifices that now form the isolated islands in the Trindade-Martin Vaz Archipelago. Geological mapping and detailed magnetometric surveys suggest different rock properties for distinct volcanic episodes that formed the Trindade Island. The remarkable pattern of magnetic anomalies trending NE-SW in the deep-water region of the Espírito Santo Basin, eastwards of the AVC, suggests that the linear chain of volcanic edifices in the VTC may be associated with mantle anomalies caused by a hotspot or plume that was influenced by the E-W direction of leaking transform fracture zones. <b>Abbreviation:</b> Abrolhos Volcanic Complex (AVC); Vitória-Trindade Chain (VTC)

本研究围绕巴西东部大陆边缘（Eastern Brazilian Continental Margin）已有的区域地质与地球物理数据集——位场数据（potential field data）结合地震测线（seismic lines）——展开分析，并系统梳理了应用于维多利亚-特里达德海链（Vitória-Trindade Chain, VTC）地质解译的各类构造模型（tectonic models）。研究将在特林达迪岛（Trindade Island）获取的新磁测数据与汇编的岩石学数据（petrological data）及地质图相结合，针对火山序列（volcanic sequences）建立了带有放射性定年约束（radiometric control）的地层柱（stratigraphic column）。本研究将重力与磁异常图（gravity and magnetic anomaly maps）与从大陆架（continental platform）延伸至洋壳（oceanic crust）的区域地震剖面（regional seismic profiles）进行整合，揭示了阿布罗卢霍斯火山杂岩（Abrolhos Volcanic Complex, AVC）与VTC的地貌（geomorphology）特征。针对特林达迪岛的详细地质填图（detailed geological mapping）辅以岛上获取的磁测剖面（magnetometric profiles）得以完善。通过⁴⁰Ar/³⁹Ar定年法，研究对特林达迪岛不同火山-地层序列（volcano-stratigraphic sequences）中识别出的岩浆事件（magmatic episodes）开展了地质年代学定年，结果显示其形成时代为晚新近纪（Late Neogene）至第四纪（Quaternary）（上新世/晚更新世（Pliocene/Upper Pleistocene）），且指示该岩石为形成于中生代（Cretaceous）洋壳之上的侵入火成岩与喷出火成岩（intrusive and extrusive igneous rocks）。针对这些火山岩在更古老洋壳上的就位机制，现有研究提出的成因模型包括热点（hotspots）与渗漏断裂带（leaking fracture zones）两类。沿维多利亚-特里达德火山链分布的火山滩（volcanic banks）与海山（seamounts）均可见平顶构造，表明原本规模更为庞大的火山锥（volcanic edifices）经侵蚀作用改造，最终形成了特里达德-马丁瓦斯群岛（Trindade-Martin Vaz Archipelago）中的孤立岛屿。地质填图与详细磁测调查结果显示，构成特林达迪岛的不同岩浆事件所形成的岩石具有各异的物性特征。在阿布罗卢霍斯火山杂岩东侧的埃斯皮里图桑托盆地（Espírito Santo Basin）深水区域，呈现出显著的东北-西南向（NE-SW）磁异常展布特征，这表明VTC中的线性火山锥链或与地幔异常（mantle anomalies）相关——该异常由受东-西向（E-W）渗漏转换断裂带（leaking transform fracture zones）调控的热点或地幔柱（plume）所引发。缩写说明：阿布罗卢霍斯火山杂岩（Abrolhos Volcanic Complex, AVC）；维多利亚-特里达德海链（Vitória-Trindade Chain, VTC）