Los piroxenos de las rocas graníticas de la Sierra de Guadarrama (S.C.E.)

Abstract

The pyroxenes are rarely observed in the granitic rocks from the Sierra de Guadarrama. The clinopyroxene only exists in the basic-intermediate types of cafemic calc-alkaline associations ( El Tiemblo, Almenara, Ventosilla, etc); in the granodiorites from alumino-cafemic monzonitic associations ( Navas del Marqués and La Cabrera ), or in the enclaves included in these rocks. Only in the Ventosilla pluton is also possible to find ortopyroxene crystals. The geochemical study of these phases allows the determination of different conditions of formation of these minerals: f02, Tª, etc, in the various granitic types. In some occasions and possibly by slow cooling rate of the plutonio masses, the crystals of clinopyroxene present granule exolution and subsolidus reequilibrium