Rocas estictolíticas de la Sierra de Guadarrama

Résumé

Some finimetamorphic granitoidic rocks, rich in nodules, with metamorphic outcroping, appear in the central part of the Sierra de Guadarrama, specially close to Sotosaltos and Santo Domingo de Pirón (Turégano's Map). Because of its frecuent migmatitic character, these rocks have been defined as stictolithic. The stictolithic rocks appear as: separated nodules between the metamorphic rocks, with or without granitic halo (E^: as nodular granitic veins, sometimes according to shear microbands (E2); or like inhomogeneous granitic bodies, no more than some meters in shape (E3). All of these stictolithic faciès are composed by one two-mica granitic fraction, and a quartz-cordieritic maphic nodule, moreover there are also some nodules with quartz-turmaline. The geochemical study points out and anatectical origin of these rocks. In this contest the nodular character could be due by inmiscibility phenomena (or segregation). These rocks are subauthoctonous (there are incongruencies in an idea of anatexis in situ), and in more advanced stictolithic faciès (Ej), they show some assimilation of metamorphic wall rocks.