Chemical and O-isotope compositions of amphiboles and clinopyroxenes from A-type granites of the Papanduva Pluton, South Brazil: Insights into late- to post-magmatic evolution of peralkaline systems

Autor(es)

Vilalva, Frederico C. J. ^[1] ; Vlach, Silvio R. F. ^[2] ; Simonetti, Antonio ^[3]

Afiliação do(s) autor(es)

^[1] Univ Fed Rio Grande do Norte, Ctr Ciencias Exatas & Terra, Dept Geol, BR-59078970 Natal 1639, RN - Brazil

^[2] Univ Sao Paulo, Inst Geociencias, Dept Mineral & Geotect, BR-05508080 Sao Paulo, SP - Brazil

^[3] Univ Notre Dame, Dept Civil & Environm Engn & Earth Sci, Notre Dame, IN 46556 - USA

• Tipo de documento: Artigo Científico
• Fonte: CHEMICAL GEOLOGY; v. 420, p. 186-199, JAN 20 2016.
• Citações Web of Science: 6

Resumo

Clinopyroxene and amphibole are the main mafic minerals in peralkaline granites of the Papanduva Pluton, Morro Redondo Complex, one of the most important granitic occurrences within the Graciosa A-type Province, S-SE Brazil. Clinopyroxene is present as three distinct late-to post-magmatic textural generations of aegirine, as well as post-magmatic aegirine-augite. Amphibole is predominantly magmatic ferrorichterite and arfvedsonite, and post-magmatic riebeckite. Major and trace element compositions reveal evolutionary trends characterized by increasing Fe3+ and Na and decreasing Fe2+, Ca, HFSE, and REE contents from core to crystal rims; trace element and REE partitioning is controlled by the composition of the coexisting melts or fluid phases, as well as by crystal chemistry. delta O-18 values for minerals investigated range from +2.3 to +6.4 parts per thousand and correlate both with increasing degrees of alkalinity and quasi-solidus (sub-magmatic) deformation affecting several granites of the Papanduva Pluton. These deformation events played a significant role in the concentration and circulation of residual melts and fluid phases from which amphiboles and clinopyroxenes precipitated. Combined textural, chemical, and O isotope findings suggest that these fluids evolved through more oxidizing (close to the FMQ buffer), alkali-(i.e. peralkaline), fluorine-, and O-18-rich conditions, associated with higher abundances of HFSEs and REEs within a temperature interval between 750 and 700 degrees C (late-magmatic stages) and 400-450 degrees C (post-magmatic stages). (C) 2015 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 08/00562-0 - Interação manto-crosta e a geração e evolução do magmatismo pós-colisional de tipo-A: registros geoquímicos e isotópicos da Província Graciosa, S-SE do Brasil
• Beneficiário: Silvio Roberto Farias Vlach
• Modalidade de apoio: Auxílio à Pesquisa - Regular