Geology, petrography and geochemistry of the A-type granites from the Morro Redondo Complex (PR-SC), southern Brazil, Graciosa Province

Author(s)

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

Affiliation

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

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

• Document type: Journal article
• Source: Anais da Academia Brasileira de Ciências; v. 86, n. 1, p. 85-116, MAR 2014.
• Web of Science Citations: 6

Abstract

The Morro Redondo Complex is one of the most important occurrences of the Graciosa A-type Province, southern Brazil. It consists of the Papanduva and Quiriri granitic plutons and a contemporaneous bimodal volcanic association. The Papanduva Pluton includes massive and deformed peralkaline alkali-feldspar granites with Na-Ca and Na-amphiboles and clinopyroxenes. The deformed types are the most evolved rocks in the province and carry rare ` agpaitic' minerals, some being described for the first time in granites from Brazil. The larger Quiriri Pluton comprises massive, slightly peraluminous, biotite syeno-and monzogranites with rare Ca-amphibole. Biotite compositions are relatively homogeneous, whereas sodic amphiboles and clinopyroxenes show increasing Na and Fe3+ evolving paths. The Morro Redondo granites are ferroan, with high SiO2, alkalis and HFSE contents; the peralkaline types registering the highest fe\#. LILE and HFSE abundances increase with the agpaitic index and the most evolved are HHP granites, with radiogenic heat production up to 5.7 mu Wm(-3). Geothermobarometric estimates indicate emplacement under low pressures (similar to 100 MPa), at temperatures up to 850- 800 C, and relatively reduced(QFM) and oxidized (+ 1 <Delta(QFM) < + 3) environments for the Papanduva and Quiriri Plutons, respectively. In both cases, melts evolved to relatively high oxidation states upon crystallization progress. (AU)

• FAPESP's process: 08/00562-0 - Mantle-crust interaction and the genesis and evolution of the A-type: post-collisional magmatism: geochemical and isotopic records from the Graciosa Province, S-SE Brazil
• Grantee: Silvio Roberto Farias Vlach
• Support Opportunities: Regular Research Grants