Syntectonic granites in thrust and strike–slip regimes: the history of the Carmo and Cindacta plutons (southeastern Brazil)

The Carmo and Cindacta plutons (SE Brazil) represent syntectonic intrusions during the late-Proterozoic Brasiliano orogeny (700–500 Ma) in the southern Ribeira belt. A first magma pulse (the Carmo pluton) intruded as a thin lenticular body along a low-angle WSW-directed overthrust plane, which probably formed during the collision of the Congo and São Francisco cratons. The magma crystallized at a depth of ∼22 km. In a later stage of the Brasiliano orogeny, large-scale strike–slip shear zones developed. Along these zones, two successive compositionally different magma pulses (the Cindacta pluton) intruded. The first of these pulses probably intruded into a pull-apart structure, and the second was emplaced parallel to a strike–slip shear zone at a depth of ∼19 km. Both magmas cooled under the same deformation regime to the lower amphibolite facies. The two plutons exemplify the sheet-like intrusions of granitic magmas during thrust and strike–slip tectonics under conditions of continent collision.