Ikenne, M. and Ennaciri, A. and Ouguir, H. and Cousens, B. and Ziyadi, R. and Mouhagir, M. and El-Gaouzi, A. (2007) Geochemical signature and geodynamic significance of an Ag-Hg mineralized dyke swarm in the neoproterozoic Ilier of Imiter - anti-atlas (morocco). Ofioliti, 32 (2). pp. 109-118.

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The Cryogynian basement of the Imiter Inlier and its volcanic cover are crosscut by an important swarm of mafic and felsic dykes. In the volcanic series, the dykes are oriented N-S to N70°E and emplaced within a E-W tensional stress field, whereas in the basement they are parallel to pre-existing planes (S o//S 1) which vary in trend from N70°E to N90°E. Silver mineralization is closely associated with mafic dykes that behaved as mechanical traps, either due to their brittle structural behaviour or by behaving as a barrier to fluid flow. Two petrogenetic groups have been recognised in dyke rocks: the first group consists of basalts and basaltic-andesites, the second one corresponds to andesites, quartz-microdiorites, and keratophyres. Both groups are calc-alkalic and display geochemical features comparable to those of magmatic rocks from modern active continental margins and island arcs: large ion lithophile (LIL) element enrichments, high field strength (HFS) element depletion, and weakly fractionated rare earth element (REE) (La/Yb) N = 3.7 to 6.6) patterns. Constraints of the regional geology suggest that these rocks were associated with post-orogenic, post-Panafrican rifting and preclude any subduction activity at that time. Their nature and their chemical signature can be related to: (i) the existence of fragments of an older subducted crust, (ii) partial melting of a mantle contaminated during the orogenic Panafrican stages or (iii) contamination during ascent of mantle derived magmas by African crust.

Item Type: Article
Uncontrolled Keywords: andesite; dike; geochemistry; geodynamics; magma; mercury (element); mineralization; Pan African orogeny; Proterozoic; silver; stress field, Africa; Morocco; North Africa
Subjects: Earth and Planetary Sciences
Divisions: SCIENTIFIC PRODUCTION > Earth and Planetary Sciences
Depositing User: Administrateur Eprints Administrateur Eprints
Last Modified: 31 Jan 2020 15:46
URI: http://eprints.umi.ac.ma/id/eprint/2944

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