Antonio Díaz de Federico

The Nevado-Filabride metaophiolitic association in the Cobdar region (Betic Cordillera, SE Spain): preservation of pillow structures and development of coronitic eclogites

AbstractThe Nevado-Filabride ophiolilic association is made up of the dismembered and metamorphosed remains of a Jurassic ocean floor. This associatiion is exceptionally well preserved, and locally unmetamorphosed, around the village of Cobdar (prov. of Almeria). It crops out in this area as lenticular metabasite and metasedimentary bodies, about 7 km in length and several hundred metres thick, tectonically intercalated between the Caldera and the Sabinas Units of the Mulhacen Group of Nappes. The ophiolitic association in this region is made up of three distinct sequences: a plutonic sequence consisting of cumulitic troctolites, olivine-pyroxene gabbros and dolerites, cut through by numerous dykes of porphyric basalts; a volcanic sequence composed of massive or vesicular olivine-pyroxene basalts, sporadically intersected by basaltic dykes and locally containing pillow-structures; and a frequently laminated sedimentary sequence made up mostly of ankerite-garnet calc-schists with interbedded lenses of mica...

The evolution of the magmatism in the external zones of the Betic Cordilleras during the mesozoic

AbstractThe Mesozoic igneous rocks from the External Zones of the Betic Cordilleras extend for some 300 km along the Subbetic Zone. They are poorly differentiated basic rocks which, altogether, correspond to a transitional series containing tholeiitic and sodium-alkaline terms. They crop out as small ophite stocks and dykes intruded into middle- and upper-Triassic rocks, or as submarine flows and sills interlayered with Jurassic materials.Geological and radiometric evidence points to an upper-Triassic-Liassic age for the ophite-generating magmatism, while the fissure volcanism began locally in the early-Liassic and extended throughout the Dogger. It reached its climax in the Tithonian and ceased abruptly in the lowermost Cretaceous.The magmas that generated the two groups of rocks originated within the mantle. During the ascent through a continental crust they were contaminated by deep-crust granitoid rocks and by the assimilation of pelites from the basement. The chemical composition and fractional-cryst...

Exsolution microstructures in amphiboles from metabasalts of the Betic ophiolitic association (SE Spain)

Exsolution microstructures in a complex amphibole assemblage from metabasalts of the Betic Ophiolitic Association (SE Spain) have been studied using transmission and analytical electron microscopy (TEM, AEM). Three main types of amphibole were identified, filling veins and vesicles: brown amphibole, with mean composition of pargasite, originated during an early ocean-floor metamorphism, and two types of green amphiboles with compositions of edenite and actinolite-magnesiohornblende, respectively formed during a later orogenic metamorphic event. The exsolution in the brown amphibole include minute rutile and amphibole rods. The brown amphibole also contains numerous halite inclusions. Amphibole exsolutions, with compositions of magnesiohornblende and actinolite appear to have formed paired rutile + amphibole intergrowths. All the exsolution products appear oriented with respect to the lattice of the host amphibole. Green amphiboles do not contain either submicroscopic rutile or halite inclusions, but they show oriented lamellae of magnesiokatophorite, exsolved in the edenite. These thin lamellae (300 to 500 A in thickness) are coherently intergrown with the host. The studied amphibole pairs evidence two types of miscibility gaps: the one gap between amphiboles of the calcic group (brown amphibole) and the other gap between amphiboles of the calcic and sodiccalcic groups (green amphibole).