Title: Neoproterozoic magmatism in Southwestern Algeria (Sebkha el Melah inlier): a northerly extension of the Trans-Saharan orogen
Abstract: The Neoproterozoic Sebkha el Melah inlier is a part of the Pan-African Trans-Saharan orogenic belt that is exposed in northwestern Africa east of the West African craton. The inlier is composed of a 4–5 km thick sequence of fine-grained marine to fluvial clastic sedimentary rocks intercalated with, and conformably overlain by, mafic lava flows and proximal volcaniclastic deposits, 600–1000 m thick. The lava flows and associated minor intrusives are mainly shoshonites. Their geochemical characteristics are indicative of subduction-related magmas and are characterized by relative depletion of Nb, Ta and Ti with respect to rare-earth elements and Th. Their positive but highly variable eNd values (þ1–þ5) are interpreted to reflect contamination of mantle-derived mafic melts (�þ 6) by continental crust. It is suggested that the Sebkha el Melah shoshonitic rocks formed in a backarc or rifted arc setting. Their location, close to the Trans-Saharan suture, is interpreted to be the result of subduction erosion which removed the forearc and possibly also part of the arc. The shallow source ( 620 Ma, Neoproterozoic volcanic suites of the Trans-Saharan belt change to typical continental, Andean margin calc-alkaline rocks in the northwestern Hoggar and an oceanic island arc complex in Mali. This may indicate that the rate of convergence of the West African craton and the Tuareg (Saharan) paleocontinent increased from south to north due to a change in the angle of convergence across the margin (oblique in the south to orthogonal in the north), resulting from the curve of the eastern margin of the West African craton that swings from N–S to NW–SE. 2002 Elsevier Science Ltd. All rights reserved.
Publication Year: 2002
Publication Date: 2002-08-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 22
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