Structures Associated with the Dynamics of Granitic Rock Emplacement (NW Portugal)

Abstract

AbstractThis chapter proposes a fieldtrip on NW of Portugal (Oporto metropolitan area), which is a sequence of thematic stops. The stops began on deep crustal level at a magmatic feeder zone—Leça da Palmeira Metamorphic Complex, and follows to a middle-upper crustal level with magmatic features associated with magmatic chamber dynamics of post-orogenic biotite granite (Bt-granites)—the Lavadores granite. Each theme is methodological divided into several sections: short introductory text about each feature highlighted on the outcrops; stop description supported with sketches and photos illustrating what can be really seen at the outcrops; field and/or drawing activity; discussion and conclusion section, focused on new approaches and interpretations of the geological results. On Leça Palmeira Metamorphic Complex the major issue is a granite-tonalite relationship on a deep shear zone, where a magmatic feeder zone was evolved as a gneissic complex. The Lavadores granite shows all a sequence of mesostructures related with the interaction between mafic microgranular enclaves and the host granite; a morphological potash feldspars (Kfs) classification is used; hybridization mechanism involving Kfs and enclaves motion and an Enclave Disruption Mechanism (EDM) is proposed; feldsphatic plume structure recorded the feeding process into the magmatic chamber.KeywordsGranitic rocksMetamorphic complexMagmatic structuresMagmatic chamber dynamicsMafic micogranular enclaves