El macizo metagranítico de La Cebollera (Pico de las Tres Provincias, Somosierra, Sistema Central español): nuevos datos sobre el metamorfismo hercínico del sector de Somosierra

Laburpena

La Cebollera metagranite massif differs from the associated orthogneisses of the Somosierra area (Spanish Central System) by its massive, meta-igneous appearance, the presence of rapakivi-like textures and abundance of metamorphic xenoliths, in cases showing evidence of polyphase deformation. The peraluminous character (ASI values of 1.5 to 1.6) and the trace element contents allow to correlate them with the nearby Lower Ordovician felsic orthogneisses. P-T estimates for recrystallization of La Cebollera metagranites show a thermal-peak event (M1) at 725 ± 10 ºC and 9.5 ± 0.5 kbar followed by a retrogression (M2) of 575 ± 25 ºC and 2.5 ± 0.5 kbar. This new metamorphic path with high exhumation rate (of around 7 kbar) and near isothermal decompression (showing 100-150ºC of cooling) suppose higher P-T conditions than previously assumed in metamorphic studies on this sector of the Hercynian foldbelt.