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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Contrasted crustal sources as defined by whole-rock and Sr-Nd-Pb isotope geochemistry of neoproterozoic early post-collisional granitic magmatism within the Southern Brazilian Shear Belt, Camboriu, Brazil

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Author(s):
Florisbal, Luana Moreira [1] ; Janasi, Valdecir de Assis [1] ; Bitencourt, Maria de Fatima [2] ; Stoll Nardi, Lauro Valentim [2] ; Heaman, Larry M. [3]
Total Authors: 5
Affiliation:
[1] Univ Sao Paulo, Inst Geociencias, BR-05508080 Sao Paulo - Brazil
[2] Univ Fed Rio Grande do Sul, Inst Geociencias, Ctr Estudos Petr & Geoquim, BR-91500000 Porto Alegre, RS - Brazil
[3] Univ Alberta, Dept Earth & Atmospher Sci, Edmonton, AB T6G 2E3 - Canada
Total Affiliations: 3
Document type: Journal article
Source: Journal of South American Earth Sciences; v. 39, p. 24-43, NOV 2012.
Web of Science Citations: 12
Abstract

The early phase of post-collisional granitic magmatism in the Camboriu region, south Brazil, is represented by the porphyritic biotite +/- hornblende Rio Pequeno Granite (RPG; 630-620 Ma) and the younger (similar to 610 Ma), equigranular, biotite +/- muscovite Serra dos Macacos Granite (SMG). The two granite types share some geochemical characteristics, but the more felsic SMG constitutes a distinctive group not related to RPG by simple fractionation processes, as indicated by its lower FeOt, TiO2, K2O/Na2O and higher Zr Al2O3, Na2O, Ba and Sr when compared to RPG of similar SiO2 range. Sr-Nd-Pb isotopes require different sources. The SMG derives from old crustal sources, possibly related to the Paleoproterozoic protoliths of the Camboriu Complex, as indicated by strongly negative epsilon Nd-t (-23 to -24) and unradiogenic Pb (e.g., Pb-206/Pb-204 = 16.0-16.3; Pb-207/Pb-204 = 15.3-15.4) and confirmed by previous LA-MC-ICPMS data showing dominant zircon inheritance of Archean to Paleoproterozoic age. In contrast, the RPG shows less negative epsilon Nd-t (-12 to -15) and a distinctive zircon inheritance pattern with no traces of post-1.6 Ga sources. This is indicative of younger sources whose significance in the regional context is still unclear; some contribution of mantle-derived magmas is indicated by coeval mafic dykes and may account for some of the geochemical and isotopic characteristics of the least differentiated varieties of the RPG. The transcurrent tectonics seems to have played an essential role in the generation of mantle-derived magmas despite their emplacement within a low-strain zone. It may have facilitated their interaction with crustal melts which seem to be to a large extent the products of reworking of Paleoproterozoic orthogneisses from the Camboriu Complex. (C) 2012 Elsevier Ltd. All rights reserved. (AU)

FAPESP's process: 07/02387-9 - Petrogenesis of contemporary felsic-mafic rock associations: an integration of geochemistry and structural geology in post-collision sintectonic granites of Santa Catarina
Grantee:Luana Moreira Florisbal
Support type: Scholarships in Brazil - Doctorate
FAPESP's process: 07/00635-5 - Contributions from the mantle and different crust reservoirs to the Neoproterozoic granitic magmatism in SE Brazil
Grantee:Valdecir de Assis Janasi
Support type: Regular Research Grants