Estudio geoquímico preliminar sobre la composición de feldespatos potásicos y muscovitas de pegmatitas de las sierras de Velasco y Mazán, provincia de La Rioja

SARDI, F. G. Y LOZANO FERNÁNDEZ, R.

Río Cuarto, Córdoba

Congreso; 10° Congreso de Mineralogía y Metalogénesis (MINMET); 2010

Universidad Nacional de Río Cuarto

The pegmatites of the Velasco and Mazán district belong to Pampean Pegmatite Province. In both cases, the host-rock is peraluminous granite with high degree of fractionation. The age is Carboniferous for Velasco range and Ordovician for Mazán range. The pegmatite bodies have simple zoning, being the intermediate zone the most important in volume, composed of perthitic microcline. The Velasco´s pegmatites contain beryl and phosphates (triplite and F-apatite) as accessory minerals, while the Mazán´s pegmatites contain sometimes andalusite. The first belong to rare-element class (beryl type) and the second would classify as intermediate between rare-element class and muscovite class. The Rb, Cs and Ga contents in K-feldspars and the Rb, Cs and Ba in muscovites, both minerals from the intermediate zones, are considered in agreement to composition of similar minerals of other pegmatites from Pampean Province. Besides, they would be in agreement to the studied pegmatites typology. On the other hand, the Ba and Li contents in muscovite could be useful to distinguish the precedence of pegmatites between Velasco and Mazán district.