Abstract The oceanic basins are dotted by seamounts, guyots and islands formed by the mantle plumes and oceanic lithosphere interaction. These plumes are responsible for several intraplate volcanisms such as the Emperor-Hawaii Chain in the Pacific Ocean with a remarkable bend at ca. 47 Ma. Comparatively, the Vitoria-Trindade Ridge (VTR) in the South Atlantic Ocean was also generated by a mantle plume and in response to the lithosphere interaction and tectonic settings it shows three remarkable bends through time. One occurred after 85 Ma associated with the Trindade plume tail movement under the Archean Sao Francisco Craton, and another one ca. 52 Ma after the formation of the Abrolhos Bank in the Brazilian platform ( Mohriak, 1989 ; Thompson et al., 1998) when the Trindade Plume encountered a thinner lithosphere in the Brazilian coast and formed a chain of seamounts and islands of W-E direction. The last bend marked in the Trindade plume trajectory is ca. 20o00′lat, around Davis Bank, marking a Miocene (21.07 Ma - 40Ar/39Ar whole-rock method) subtle clockwise rotation in the South American Plate. The easternmost part of this ridge is composed of Trindade-Martin Vaz Archipelago subject of this study. Located ca. 1200 km away from the Brazilian coastline at the Vitoria (ES) parallel, its geology is an important preserved record of an alkaline Pliocene-Pleistocene volcanism, the youngest one recorded in the Brazilian territory. Martin Vaz and the nearby islets are located on the easternmost part of the VTR. Its geological features include phono-tephritic to tephri-phonolitic domes; nosean-phonolitic dykes and sub-horizontal layers formed by pyroclastic rocks and subordinate lava flows (melanephelinites) of Volcanian-style magmatism (mostly). 40Ar/39Ar ages yielded values ranging from 336 to 721 ka representing a young and short period of intraplate magmatic activity in the South American Plate offshore. These new ages associated with compiled radioisotopic ages from onshore and offshore volcanic rocks represent a strong decreasing age correlation related to Trindade Mantle Plume. Moreover, Trindade-Martin Vaz Archipelago is a contemporaneous product of a terminal plume expression in the offshore portion of a long-lived track (ca. 90 Ma) with a slow shear velocity (VS) placing its origin at the Upper Mantle suggesting a shallow mantle plume rising from the asthenosphere.

中文翻译：

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Martin Vaz 岛地质年代学：来自最年轻和最东端的火山事件对特林达德地幔柱轨迹的约束

摘要 大洋盆地分布着海山、盖奥特和由地幔柱和大洋岩石圈相互作用形成的岛屿。这些羽流是几个板块内火山活动的原因，例如太平洋中的皇帝 - 夏威夷链，在大约 10 处有一个显着的弯曲。47 马。相比之下，南大西洋的维多利亚-特林达德海脊 (VTR) 也是由地幔柱产生的，并且响应岩石圈相互作用和构造环境，它随着时间的推移显示出三个显着的弯曲。一个发生在与太古代圣弗朗西斯科克拉通下的特林达德羽状尾运动相关的 85 Ma 之后，另一个发生在大约 85 Ma 之后。52 Ma 在巴西地台形成 Abrolhos Bank 后 (Mohriak, 1989; Thompson et al., 1998 年）当特林达德羽流在巴西海岸遇到较薄的岩石圈并形成 WE 方向的海山和岛屿链时。特林达德羽流轨迹中标记的最后一个弯道是大约。20o00'lat，围绕戴维斯银行，标志着南美板块中中新世（21.07 Ma - 40Ar/39Ar 全岩方法）微妙的顺时针旋转。该山脊的最东部分由本研究的 Trindade-Martin Vaz 群岛组成。位于约。距巴西海岸线维多利亚 (ES) 平行线 1200 公里，其地质是碱性上新世-更新世火山活动的重要保存记录，是巴西境内记录的最年轻火山活动。Martin Vaz 和附近的小岛位于 VTR 的最东端。其地质特征包括音温岩至温音质圆顶；由火山碎屑岩和火山式岩浆作用的次要熔岩流（黑斑岩）形成的鼻山-音质岩脉和亚水平层（主要是）。40Ar/39Ar 年龄产生的值范围从 336 到 721 ka，代表南美板块近海板块内岩浆活动的年轻和短期。这些与来自陆上和海上火山岩的汇编放射性同位素年龄相关的新年龄代表了与 Trindade Mantle Plume 相关的强烈下降的年龄相关性。此外，特林达德-马丁瓦斯群岛是长寿命轨道（约 90 Ma）近海部分终端羽流表达的同期产物，具有缓慢的剪切速度 (VS)，其起源位于上地幔，表明存在浅层地幔柱从软流圈升起。