The emplacement , geochemistry and petrogenesis of two central Morocco Hercynian granites . Geotectonic implications

New field, petrographic and geochemical data including REE, Rb-Sr, and K-Ar, are presented conceming the emplacement and petrogenesis of two calc-alkaline Moroccan Hercynian granites: the Zalr pluton and thc Djebel Aouam stocks. Zonation in the Zalr pluton does not appear to result from simple fractional crystallization nor from hydrothermal alteration but is rather the diapiric. intrusion of two interlocked bodies. REE geochemistry supporls the interpretation that the biotitegranodiorite magma (301 f 8.2 M.a.) and thc Djebel Aouam stocks appear to have been derived by fusion of crustal materials with possible mantle contamination (Initial 87Sr/%r ratio = 0.70514). The second two-mica granitic magma (283.4 f 6.2 M.a.) corrcsponds to a peraluminous granite (1.22 < A/ CNK < 1.33) generated by fusion of continental crust including mature sedimentary materials (Initial 87Sra6Sr atio = 0.70836). Thesc granites arc compared to the Acadian granites of north Appalachian and classified in the ccpost-collision, uplift environmentu type. An illustrative four step model presenting the generation and emplacement of these two granites togethcr with the associated W-SnPb-Zn-Ag mineralizations is proposed (1) frst magma generation. (2) first melt emplacemcnt, (3) second melt emplacement, (4) late convectivc flow.

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