الفهرس | Only 14 pages are availabe for public view |
Abstract The post-collisional Mueilha and Homrit Akarem intrusions were emplaced into metamorphic country rocks with sharp intrusive contacts. They represent a magmatic cupolas above highly fractionated A-type granites. The early phases of the two intrusions reached subvolcanic conditions and emplaced a along the apex of the magmatic cupola. Subsequently, the granitic magmas crystallized downwards forming a differentiation series of hypabyssal granites. The main emplacement mechanism and evolutionary sequence of the two granitic plutons was magmatic, although the effects of hydrothermal fluids and extensive replacement by secondary minerals are observed in the marginal zones at the apex of the two intrusion. The rock types of the MGP and HAGP are nearly similar in their essential mineral compositions. They consist essentially of K-feldspars, quartz and albite with less amounts of plagioclase and mafic minerals. They contain wide variations of accessory minerals such as biotite, muscovite, zircon, garnet, Nb-Ta oxides, fluorite, Fe-Ti oxides, apatite, sphene, topaz, beryl, cassiterite and allanite. Nb-Ta oxides are the most important accessory minerals in the MGP and HAGP. They include primary phases such as columbite and tantalite, and secondary phases such as fluorcalciomicrolite and wodginite. Mineral chemistry of biotite and garnet indicated their primary magmatic nature that crystallized from peraluminous magma with A-type characters |