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Alcides Nobrega Sial, Federal University of Pernambuco (Brazil)
Paulo M. Vasconcelos, University of Queensland (Australia)
Valderez Pinto Ferreira, Federal University of Pernambuco (Brazil)
Ricardo Ribeiro Pessoa, Federal University of Pernambuco (Brazil)
Roberta Galba Brasilino, Companhia de Pesquisa de Recursos Minerais (Brazil)
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Calc-alkalic to high K-calc alkalic granitoid plutons in the Borborema province, northeastern Brazil, have been studied to constrain depth of emplacement by mineralogical and geological methods and to estimate upward magma transport rate based on partial dissolution of magmatic epidote (mEp).
Laser-probe incremental heating 40Ar/39Ar dating of biotite and hornblende single crystals from the Neoproterozoic Tavares and Brejinho high K-calc alkalic magmatic epidote (mEp)-bearing plutons reveals age differences of ∼ 60 m.y. between these two minerals in each of these two intrusions. These data suggest solidification at relatively great depth followed by prolonged cooling interval between the closure temperatures of biotite and hornblende.
Al-in-hornblende barometry indicates that hbl in several mEp-bearing plutons in the Transversal Domain of the Borborema province solidified at 5 to 7 Kbar, whereas in the Seridó and Macururé terranes, solidification pressures range from 3 to 4 Kbar.
Partial dissolution of epidote indicates very rapid upward transport. Partial corrosion occurred during 15-35 years (Cachoerinha-Salgueiro terrane), 10-30 years (Alto Pajeú), 15 years (Seridó), and 10 years (Macururé) corresponding to upward transport rates of 450-1300, 650-1050, 1200, and 1800 meters/year respectively in these four terranes. Rapid upward magma migration in most cases was probably facilitated by diking simultaneous with regional shearing.
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