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Basaltic magmatism related to the early stages of rifting along the Benue Trough: The Obudu dolerites of south‐east Nigeria
Author(s) -
Ekwueme Barth N.
Publication year - 1994
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3350290306
Subject(s) - magmatism , trough (economics) , geology , rift , basalt , geochemistry , geomorphology , seismology , structural basin , tectonics , economics , macroeconomics
Dolerites of the Obudu Plateau of south‐eastern Nigeria occur predominantly as dykes cutting Precambrian basement gneisses. Minor dolerite sills have also been mapped. The dolerites are dominantly olivine tholeiites and are geochemically of the oceanic basalt type. They were emplaced in a within‐plate tectonic setting and yield a 40 Ar/ 39 Ar plateau age of 140.5 ± 0.7 Ma, which is interpreted as the age of their emplacement. This age indicates that the Obudu dolerites are the products of basic magmatism related to the early stages of rifting along the Benue Trough of Nigeria. The Obudu dolerites are comparable with Mesozoic tholeiitic dykes of the northern Amazon craton, whose intrusion preceded the break‐up of Africa and South America.