Geología y geoquímica del granito de Montánchez (Cáceres)

Abstract

The granite of Montánchez (Cáceres, Spain) is located to the S.E. of the Albalá granite and is separated from it by a strongly tectonized zone. According to the mica content, three perografic facies have been distinguished in the Montánchez granite. Facies 1, is made up of medium to coarse grained, two mica granites richer in muscovite, which occupy the northern half of the granite and have been extremely deformed. Facies II, consiting of coarse to very coarse grained, sometimes porphyrblastic, two-mica granites, richer in biotite, has not been deformed, or very little. Facies III is made up of aplitic muscovite granties which are poor in biotite and rich in tourmaline. The Montánchez granite frecuently contains tonalitic xenolith, sometimes quitee large. Regarding the geochemistry of the Montánchez granite the major and some trace elements have been analyzed on 22 samples belonging to the three different facies and the tonalitic xenoliths. As for the major elements, the chemical-mineralogical parameters of la Roche, the binary diagrams of Harker, Larsen, la Roche and Deban and Le Fort, and the ternary diagrams Na₂O, K₂O, CaO, Na₂O+K₂O, Al₂O₃, CaO and AFM have been calculted. They indicate that these granties are made up alkaline rocks richer in Na than K, poor in Ca, and with a markedly peraluminous character. Concerning the distribution of the trace elements in the Montánchez granite the average conten in Rb, Ba, Sr, Zr and Nb lower and those in Sn and Zn higher, than the values reported by different autors for several world granites considered to be standard.