Provenance and tectonic setting of the external nappe of the Southern Brasilia Orogen

Author(s)

Westin, Alice ^[1] ; Campos Neto, Mario da Costa ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Geociencias, BR-05508 Sao Paulo - Brazil

• Document type: Journal article
• Source: Journal of South American Earth Sciences; v. 48, p. 220-239, DEC 2013.
• Web of Science Citations: 13

Abstract

The Brasilia Orogen, located on the western and southern margins of the Sao Francisco Craton, corresponds to a horizontal nappe stack that was regionally transported eastward during the collision between the Paranapanema and Central Goias blocks and the Sanfranciscana Plate in the Ediacaran Period. The front of the Southern Brasilia Orogen, the object of this study, is represented by metapsammites and metapelites of the Carrancas Group, with an exotic unit of metawackes which lies tectonically on top of it. The metawackes underwent moderate chemical weathering, and the rare-earth element behavior suggests the presence, in the source area, of igneous rocks with crustal signature. The age distribution of the detrital zircon crystals is almost unimodal with dominant Neoproterozoic population and subordinate Paleoproterozoic ages. The most likely source area is a mature magmatic arc in the active continental margin of the Paranapanema Block, and the deposition occurred between 620 and 590 Ma. The correlation between these external metawackes with those occurring in the internal nappes (Santo Antonio Schist of the Andrelandia Nappe) assumes that this unit corresponds to the front of the Andrelandia Nappe. However, a syn-collisional orogenic foreland basin, installed at the edge of the Sanfranciscana Plate, must be considered. The metapelites of the Carrancas Group (Campestre Formation) have a chemical signature of sedimentary recycling and deposition in a tectonically stable area. Detrital zircon crystals exhibit juvenile provenance in the Mesoproterozoic Era and mixed provenance in the Paleoproterozoic Era. The provenance ages correlate with the Canastra Group of the Brasilia Orogen in the western craton margin but are not similar to those of the cratonic units. The likely age for the deposition of the Campestre Formation of the Carrancas Group is in the Tonian-Cryogenian Period, in the southwestern edge of the Sanfranciscana Plate. (C) 2013 Elsevier Ltd. All rights reserved. (AU)

• FAPESP's process: 10/11152-8 - Tectonics of Brasília orogen at Southern margin of São Francisco Craton: a paleogeographic, metamorphic and structural perspective
• Grantee: Mario da Costa Campos Neto
• Support Opportunities: Regular Research Grants
• FAPESP's process: 05/58688-1 - South America in the context of supercontinents: fusion and fission
• Grantee: Miguel Angelo Stipp Basei
• Support Opportunities: Research Projects - Thematic Grants