Transpressive strain partitioning between the Major Gercino Shear Zone and the Tijucas Fold Belt, Dom Feliciano Belt, Santa Catarina, southern Brazil

Abstract

A composite cross section from the Florianópolis Batholith towards the Tijucas Fold Belt in the northern Dom Feliciano Belt (southern Brazil) is divided in three structural domains: the Major Gercino Shear Zone, the suprastructural Brusque Complex and the infrastructural Camboriú Complex. A kinematic correlation among the structural domains is based on structural and petrological data integrated with geochronology. An oblique collisional event at 650-645 Ma affected all structural domains and is best recorded in the Porto Belo Complex, which shows migmatization (700 °C/4.3 kbar) and top-to-the-NNW+dextral shear along the Major Gercino Shear Zone. Subsequent strain partitioning led to progressive tangential movement recorded in the Quatro Ilhas Granitoids (625-615 Ma) followed by later granitic intrusions (after 615 Ma) controlled by dextral strike-slip. Meanwhile, the contractional component was absorbed by the Tijucas Fold Belt infrastructure, causing exhumation of the Camboriú Complex migmatites (from 5 to 3.4 kbar) and unroofing of the suprastructural Brusque Complex (around 635 Ma). Tectonic juxtaposition occurred along a dextral+normal detatchment zone between the complexes. As a consequence, heating of the Brusque Complex locally reached amphibolite-facies conditions and suprastructure thrusting inverted to extension, which is recorded in discrete shear structures with normal kinematics. The sequence of events and their age suggest that the hinterland Porto Belo Complex and the foreland Tijucas Fold Belt were juxtaposed already at ca. 650–645 Ma, which questions the validity of the subduction-related tectonic models in the northern Dom Feliciano Belt.