The Brazilian continental margin includes several volcanic islands, submerged volcanic seamounts, and a unique non-volcanic archipelago located in a transform segment of the Equatorial South Atlantic. The mechanism of formation of these islands is related to post-breakup magmatic episodes dated as Late Cretaceous to Pleistocene. Diverse Late Cretaceous to Paleogene alkaline magmatic episodes are registered in southeast Brazil, resulting in igneous plugs onshore and volcanic structures offshore. The Abrolhos Volcanic Complex in eastern Brazil is characterized by several volcanic features on the continental shelf, including small islands that expose Paleogene sedimentary layers interbedded with volcanic sequences. The adjacent Vitória-Trindade Chain extends to oceanic crust forming basaltic to alkaline seamounts that outcrop at the Trindade Archipelago, the easternmost islands in Brazil with the youngest volcanic eruptions. The Fernando de Noronha lineament in northeast Brazil is characterized by Neogene alkaline igneous plugs. The small islets in the São Pedro—São Paulo archipelago, located near the mid-Atlantic ridge, are formed by exhumed mantle rocks related to compressional episodes a transform fault zone. The Rio Grande Rise in southern Brazil is characterized by shallow Paleogene seamounts and a large oceanic plateau probably related to subaerial spreading centers formed in the Late Cretaceous. Multiple mechanisms are responsible for the origin and evolution of the volcanic islands offshore Brazil in continental, transitional, and oceanic crust settings, including volcanic build-ups, leaking fracture zones, and hotspots. Some of the islands might be related to mantle plume activity, as indicated by comparisons with modern mantle plume analogues in the South Atlantic.

中文翻译：

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巴西近海南大西洋火山岛的成因与演化

巴西大陆边缘包括几个火山岛、淹没的火山海山和位于赤道南大西洋转换段的独特非火山群岛。这些岛屿的形成机制与晚白垩世至更新世的破裂后岩浆事件有关。巴西东南部记录了多种晚白垩世至古近纪碱性岩浆事件，导致陆上火成岩塞和海上火山结构。巴西东部的阿布洛霍斯火山群的特点是大陆架上有几个火山特征，包括暴露出古近系沉积层与火山序列互层的小岛。相邻的 Vitória-Trindade Chain 延伸到海洋地壳，形成玄武岩到碱性海山，这些海山在巴西最东端的岛屿 Trindade Archipelago 露头，火山喷发最年轻。巴西东北部的 Fernando de Noronha 构造以新近纪碱性火成岩塞为特征。圣佩德罗-圣保罗群岛中的小岛位于大西洋中脊附近，是由与挤压事件相关的地幔岩石形成的转换断层带。巴西南部里奥格兰德海隆的特点是古近纪浅海山和大洋高原，可能与晚白垩世形成的地下扩张中心有关。巴西近海火山岛在大陆、过渡、和海洋地壳环境，包括火山堆积、泄漏断裂带和热点。一些岛屿可能与地幔柱活动有关，正如与南大西洋现代地幔柱类似物的比较所表明的那样。