Geochronological and geochemical evidences for extension-related Neoarchean granitoids in the southern Sao Francisco Craton, Brazil

Author(s)

Moreno, J. A. ; Baldim, M. R. ; Semprich, J. ; Oliveira, E. P. ; Verma, S. K. ; Teixeira, W.

• Document type: Journal article
• Source: Precambrian Research; v. 294, p. 322-343, JUN 2017.
• Web of Science Citations: 11

Abstract

New LA-SF-ICP-MS U-Pb zircon dating of high-K granitoids from the Campo Belo metamorphic complex, southern Sao Francisco Craton (Brazil), reveals a long period (ca. 100 My) of Neoarchean granitic magmatism that post-date the TTG magmatism. The oldest studied pluton is a highly porphyritic biotite orthogneiss emplaced at 2748 +/- 5 Ma, followed by a hornblende-biotite orthogneiss (2727 +/- 7 Ma). Both granitic bodies were affected by a deformation event prior to the emplacement of the Rio do Amparo, Bom Sucesso and Lavras granitoid plutons at 2716 +/- 6 Ma, 2696 +/- 6 Ma and 2646 +/- 5 Ma, respectively. The Neoarchean granitic magmatism ended with the intrusion of peraluminous leucogranitic dikes at 2631 +/- 4 Ma. The 2.73-2.65 Ga Campo Belo granitoids share chemical features of A-type granites, such as high apatite- and zircon-saturation temperatures (mostly > 800 degrees C), relatively high Fe-number, high total alkalis and characteristic enrichment in LREE and HFSE although most samples of the Rio do Amparo granite have lower HFSE and LREE content that typical A-type granites but very high Th. The high Th content of the Rio do Amparo and Bom Sucesso granites may suggest involvement of Th-orthosilicate in their sources. The trace element composition permits to classify the Campo Belo granitoids as A(2)-type granites, suggesting derivation from partial melting of TTG-crustal sources likely in an extensional setting. Significant reworking of Mesoarchean crust is suggested by mostly negative epsilon Nd-i, values (Rio do Amparo: -2.0 and +3.1; Bom Sucesso: -3.6, -3.1 and +0.9; Lavras: -2.5 and -0.2) and old Nd model ages (T-DM close to 3.1 Ga), although with probable involvement of juvenile material (T-DM of 2.7-2.9 Ga). This contrasts with Neoarchean granites of the northern Sao Francisco and Congo cratons characterized by negligible juvenile imprint. The 2.75-2.63 Ga Campo Belo granitoids witness the thermal stabilization of the Archean lithosphere through a major episode of high-K granitoid magmatism between 2760 and 2600 Ma, which affected the whole Sao Francisco Craton and the northern Congo Craton. (C) 2017 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 14/03334-0 - Origin of TTG magmas using thermodynamic and trace element modeling
• Grantee: Julia Jennifer Semprich
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 12/15824-6 - Evolution of archaean terranes of the São Francisco Craton and the Borborema Province, Brazil: global environmental and geodynamic implications
• Grantee: Elson Paiva de Oliveira
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 14/04920-0 - Geological and geochemical investigations on archaen granite-gneiss terranes of São Francisco Craton
• Grantee: Juan Antonio Moreno Moreno
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 12/07243-3 - Application of new multi-dimensional discrimination diagrams and geochemical modeling to Archaean igneous rocks of Brazilian cratons
• Grantee: Sanjeet Kumar Verma
• Support Opportunities: Scholarships in Brazil - Post-Doctoral