Evidence for Neoproterozoic terrane accretion in the central Borborema Province, West Gondwana deduced by isotopic and geophysical data compilation

Abstract

The Borborema Province in NE Brazil is part of a large Neoproterozoic orogenic system related to the assembly of West Gondwana. Its evolution is contentious, due to the superposition of events that overprinted former records. We present a compilation of geological, isotopic (U-Pb detrital zircon and whole-rock Sm-Nd), and geophysical data that support a terrane accretion model for the Transversal subprovince (central Borborema Province). Bounded by thrust- and strike-slip shear zones of regional extent, the terranes vary in nature and age, and magmatic-arc related rocks, retro-eclogites, and dismembered ophiolites provide evidence of accretion. In addition, detrital zircon compilation suggests variable sources, including Palaeoproterozoic detritus related to the Rio Capibaribe and Alto Moxotó terranes and Neoproterozoic sources attributed to the Alto Pajeú and Piancó-Alto Brígida blocks. Accordingly, Archaean and Palaeoproterozoic Nd TDM model ages are concentrated within the Alto Moxotó and Rio Capibaribe terranes, whereas early- to late Mesoproterozoic isotopic sources dominate in the Alto Pajeú and Piancó-Alto Brígida. A compilation of robust geophysical data shows contrasts in magnetic, gamma-spectrometric, and gravity signatures between the terranes, whereas modelled depths and density values are variable, coinciding with the proposed terrane boundaries. Our analysis suggests that now eroded oceanic lithospheric branches existed within the Transversal subprovince, later converted into dry suture zones. Terrane accretion is a plausible mechanism to rearrange the crustal pieces of West Gondwana, including those of the Borborema Province, and should be considered in other orogenic belts of South America.