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

作者：Vilalva Frederico C J^*; Vlach Silvio R F

来源：ANAIS DA ACADEMIA BRASILEIRA DE CIENCIAS, 2014, 86(1): 85-116.

DOI：10.1590/0001-37652014108312

• A-type granites
• geochemistry
• petrography
• Graciosa Province
• mineralogy
• Morro Redondo
• Complex

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.

• 出版日期2014-3