Differential Phanerozoic evolution of cratonic and non-cratonic
lithosphere from a thermochronological perspective: São Francisco Craton
and marginal orogens (Brazil)
Abstract
The São Francisco Craton (SFC) and its marginal Araçuaí and Brasília
orogens exhibit a significant diversity in their lithospheric
architecture. These orogens were shaped during the
Neoproterozoic–Cambrian amalgamation of West Gondwana. The rigid
cratonic lithosphere of the SFC and the relatively weak lithosphere of
the Araçuaí Orogen were disrupted during the Cretaceous opening of the
South Atlantic Ocean, whereas the Brasília Orogen remained in the
continental hinterland. In earlier research, the thermal effects of the
Phanerozoic reactivations in the shallow crust of the Araçuaí Orogen
have been revealed by low-temperature thermochronology, mainly by
apatite fission track (AFT) analysis. However, analyses from the
continental interior are scarce. We present new AFT data from
forty-three samples from the Brasília Orogen, the SFC and the Araçuaí
Orogen, far from the passive margin of the Atlantic coast
(~150 to 800 km). Three main periods of basement
exhumation were identified: (i) Paleozoic, recorded both by samples from
the SFC and Brasília Orogen; (ii) Early Cretaceous to Cenomanian,
recorded by samples from the Araçuaí Orogen; and (iii) Late Cretaceous
to Paleocene, inferred in samples from all domains. We compare the
differential exhumation pattern of the different geotectonic provinces
with their lithospheric strengths. We suggest that the SFC likely
concentrated the Meso-Cenozoic reactivations in narrow weak zones while
the Araçuaí Orogen displayed a far-reaching Meso-Cenozoic deformation.
The Brasília Orogen seems to be an example of a stronger orogenic
lithosphere, inhibiting reworking, confirmed by our new AFT data.
Understanding the role of the lithosphere rigidity may be decisive to
comprehend the processes of differential denudation and the
tectonic–morphological evolution over Phanerozoic events.