Pirofanita y Braunita titànica en las rocas con Mn del Sector Central de Ossa-Morena

Abstract

In the Oliva de la Frontera area (Ossa-Morena Central Belt, Iberian Massif, SW Spain) titanian braunite occurs in manganiferous metashales and manganiferous metatuffs while pyrophanite is restricted to pyroxmangite metatuffs. During hercynian metamorphism primary Mn4+ was reduced to Mn3+ and Mn2+ to form piemontlte in shales and metatuffs, and more extensively in piroxmangite metatuffs to form pyrophanite. Ti and Al-enrichment in braunite depend on the whole composition while high Fe-content in braunite of piroxmangite metatuffs can be related to low f02 conditions