Uplift and denudation of the Caçapava do Sul granitoids (southern Brazil) during Late Paleozoic and Mesozoic: constraints from apatite fission-track data

Abstract

This paper describes the application of apatite fission-track (FT) thermochronology to six outcrop samples of the Caçapava do Sul granite complex in southernmost Brazil. The investigated granite body is composed of two contrasting blocks bounded by NW-trending structures. In the northern block, where leucogranitoids dominate and a 4 km deep root appears according to gravimetric modeling, two samples yielded apparent FT ages of 293.5 and 274.8 Ma. The mean lengths of the confined tracks for these samples are 11.11 and 10.57 μm, respectively, and an estimate for the initial track recording points to 366 Ma. These results are interpreted in the frame of the uplift and denudation history of the region during the evolution of the Paleozoic to Mesozoic intraplate Paraná Basin, as influenced by the convergent tectonic setting of southwestern Gondwana. In the southern block, where dioritic and gneissic portions crop out, apparent FT ages range from 252.1 to 245.5 Ma. The mean track lengths spread from 9.89 to 11.37 μm. The activity of NW-trending structures in juxtaposing the two blocks is coherent with the northeastward sedimentation pattern of the Triassic deposits of the Paraná Basin. A possible subsequent Upper Cretaceous uplift event can be inferred from the modeled thermal history curves and the apparent FT age of the northernmost collected sample, which yields 73.7 Ma and a mean track length of 12.21 μm.