Shear zone-controlled magma emplacement or magma-assisted nucleation of shear zones? Insights from northeast Brazil

摘要: Abstract In the Borborema province of northeast Brazil, neoproterozoic granitoids and large-scale transcurrent shear zones are spatially associated, suggesting a genetic link between magma bodies zones. some cases emplacement was clearly favored by zone activity, but for several plutons this model is not satisfactory. these plutons, pre-full crystallization strike-slip deformation, evidenced parallelism magmatic foliations lineations with solid-state mylonitic fabric, transition from to flow, restricted vicinity Evidence activity prior lacking, foliation away in most shallowly dipping concordant slightly older, gently-dipping, regional gneissic foliation. Field anisotropy magnetic susceptibility mapping, together petrographic geochemical studies performed one complexes have revealed structure fabric incompatible zone-controlled model. Away zones, complex has retained stratification inherited mixing crystal-poor magmas contrasting composition, characterized low-to moderate-dip bearing NW-trending lineation, which contrast vertical NE- or E-W-trending stretching indicates that started development. Based on evidence predated shearing information about deformation observed studied we suggest incompletely solidified within crust represent rheological heterogeneities may induce strain localization favor nucleation. We propose first concentrated where nucleated grew. Subsequently, as solid phase component increased, crystal mush began behave solid, propagated into country rocks.