Geochemistry of Precambrian ophiolites from Bou Azzer,Morocco |
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| Authors: | J L Bodinier C Dupuy J Dostal |
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| Institution: | (1) Centre Géologique et Géophysique, U.S.T.L., Place E. Bataillon, 34060 Montpellier, France;(2) Department of Geology, Saint Mary's University, B3H 3C3 Halifax, Nova Scotia, Canada |
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| Abstract: | The Upper Proterozoic ophiolite complex of Bou Azzer, Morocco, includes ultramafic rocks, cumulate gabbros, sheeted dykes, pillow lavas and diorite-quartz diorite intrusions and an overlying volcano-sedimentary sequence. The gabbroic cumulates, basaltic flows and dykes have compositions similar to recent ocean-floor rocks (N- and/or T-type). Among other features, they have comparable light REE-depleted patterns and relations of Ti-Zr and La-Nb. Although fractional crystallization played an important role in the evolution of these rocks, the large variations in their chemical compositions require generation from a heterogeneous upper mantle source and/or by a dynamic partial melting process. Diorites, quartz diorites and the volcanic rocks of the overlying sequence are calc-alkaline, genetically unrelated to the tholeiitic suite and indicative of an island arc setting. A possible tectonic model for the ophiolite complex is a marginal basin just behind a still active island arc. |
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