Mantle-Plume-Generated Triple Junction Between Ne Brazil And West Africa?

This paper has three purposes. First, it offers an overview<br>of the nature and history of the interior and<br>offshore basins of Northeast Brazil and West Africa,<br>and their relationship to the development of the<br>Southern and Equatorial branches of the Atlantic.<br>Second, it places emphasis on the differences of the<br>rift systems and the control exercised by basement<br>structures on the conjugate margins of West Africa<br>and Northeast Brazil. Third, as the most important, it<br>challenges the idea of a mantle-plume-generated<br>triple junction between Northeast Brazil and West<br>Africa.The Benue Trough is very often cited as one of<br>the best examples of a failed arm of an RRR triple<br>junction (Burke and Wilson, 1976), formed through<br>the activation of a mantle plume. This would imply<br>in: (1) early crustal doming, warping and flexure over<br>a plume with crestal alkaline volcanoes; (2) formation<br>of three simultaneous rift arms, symmetrically orientated<br>at 1200 to each other; (3) if one rift arm is<br>aborted, the other two develop into a single ridge<br>(new margin) and drift begin; and (4) growth of delta<br>at the mouth of a failed arm. Among them, just the<br>last one is corroborated by the data set. Voluminous<br>magmatism clearly post-dated the opening of the<br>Equatorial Atlantic. Rifting and drifting were diachronous<br>among the African - Brazilian basins and the<br>rift arms are not symmetrically orientated, and finally,<br>instead of one, there are two failed arms: Benue<br>Trough and the onshore Potiguar basin.