A bimodal source for the generation of tonalitic to granitic magmas in a non-subduction-related magmatic belt: An example from the Sierra Chica of Córdoba, Argentina

A notable consensus prevails about the hybrid nature of intermediate calc-alkaline magmatism. Accordingly, petrogenetic models envisage the addition of young mantle material and cortical recycling in those geological settings where intermediate magmas are dominant. Most exhaustively studied examples are: 1) magmatic arcs associated with subduction zone settings where oceanic crust and sediments are introduced into the mantle wedge, and 2) deep crustal sections are pervaded by hot, H2O-rich mantle-derived liquids. Nevertheless, back-arc or foreland terranes of several hundred kilometers in width, frequently characterized by high heat flux, crustal melting, recycling and melt fractionation, are crucial areas to evaluate the generation of intermediate magmatism. The Sierra Chica of Córdoba (Argentina) provides an excellent example to study these processes. The high-grade crustal segment shows metamorphosed pelitic and basaltic protoliths that were part of an old sedimentary succession. We evaluate the evolution of this bimodal source during two consecutive early Paleozoic orogenic periods when it was established as the source area of intermediate to silicic magmatism far from the contemporary magmatic arcs.