| Abstrakt: |
The Paleozoic magmatism of the Tighza Mining District (Central Morocco Massif) is of the polyphaser, emplaced during the Upper Carboniferous to the Middle Permian. It is expressed by granitic intrusions and their swarm dikes extending over several kilometers in length. The petro-structural and geochemical studies applied to this magmatic complex, has revealed the presence of several events: (i) A hypo-volcanic complex, formed from dikes, intermediate to felsic composition of microdiorite, microgranodiorite, microgranites, and rhyolites, composed of biotite, plagioclase, quartz, and K-feldspar. Apatite, zircon, and iron oxides form accessory minerals. The whole is affected by a strong hydrothermal alteration, particularly chlorite-micaceous, with parallel development of oxides and carbonates, generated by the (ii) emplaced of granitic intrusions. These, circumscribed and independent intrusions, outcropping following meridian alignment within a contact metamorphic aureole, generated by a buried granite, revealed by gravimetry. (iii) The porphyritic microtonalites with biotite, quartz, orthoclase, and plagioclase (An30-55), presented by occurrences of veins oriented in two conjugated directions NW-SE and NE-SW, intersect the granite and are relatively little altered. (iv)The microleucogranite lenses finish the magmatic activity of the region, emplaced in the sinistral shear zone, porphyritic microgranular to rhyolitic texture, with quartz, plagioclase (An<15) and primary muscovite, showing plastic deformation structures, intersected and offset by secondary quartz and muscovite veinlets. The chemical analyses in major elements and traces of the different petrographic groups of Tighza, make it possible to specify the aluminous character of this magmatism (A/CNK>1 and A/NK>1) with strong crustal participation. The hypo-volcanic complex with granitic stocks describes a calc-alkaline signature, which tends towards a win aluminum-potassic tendency which is well emphasized by microleucogranites. The focus of this magmatism in a deep crustal rupture that is activated at the end of the Variscan compression explains the syn- to post-collisional character of this magmatism as reproduced in the geotectonic diagrams. [ABSTRACT FROM AUTHOR] |
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