Aperçu sur les amas sulfurés massifs des hercynides Marocaines |
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| Authors: | A J Bernard O W Maier A Mellal |
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| Institution: | 1. Ecole Nationale Supérieure de Géologie, B.P. 452, 54001, Nancy Cedex 01, France
2. Bureau de Recherches et de Participations Minières, 5-7 Charia Moulay El Hassan, Rabat, Maroc
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| Abstract: | Massive sulfide deposits located on Hercynian islets of northwestern Morocco exhibit four main characteristics: They are strata-bound massive pyrrhotite deposits mined for sulfur and/or base metals occasionally occurring as sulfides of workable grade. Volcanic rocks with which these massive sulfide orebodies are associated are scarce, although always present as acid flows of submarine emissions of either rhyolitic or more often quartz-keratophyric nature. Later on, basic plutonics intruded the pelitic country rocks. Stockworks underlying the massive sulfide orebodies are common, but not systematic. When present, they occur in siltite ± phyllite ± carbonate rocks at the wall of massive sulfide lenses. They consist of fissural disseminations transformed by epimetamorphic recrystallization and by one schistosity generally concordant with s0. Associated alterites and exhalites belong to three types, i.e., sericitite (or biotite-rich rock), chloritite, and/or chert (jasper). Generally well located in a back-arc basin environment characterized by a two-phase geological history, i.e., “extension and volcanism, compression and metamorphism”, these volcano-sedimentary deposits exhibit distal features with regard to the volcanism coeval with their sedimentation. They are mostly linked with strongly reducing environmental properties entailing pyrrhotite and/or magnetite syngenetic deposition, whatever the iron activity. |
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