Early Ediacaran two-mica granites marking the contractional stage of the brasiliano orogeny in the Pernambuco-alagoas domain, NE Brazil

Abstract

Abstract The two-mica granitoids intrude metasedimentary rocks of the Pernambuco-Alagoas Domain in the Southern subprovince of the Borborema Province. They comprise biotite ( 10\xa0%), ferroan, alkali-calcic leucogranites. Zircon, apatite, and opaque minerals are the accessory phases. Most of the muscovite grains show high Na, Ti, Alt, and low Si (3.08–3.10 apfu) contents, being considered primary muscovite. Biotite grains have high Fe and Al, and low Mg contents, and Fe# (FeOt/FeOt\xa0+\xa0MgO) values ranging from 0.68 to 0.79, typical of biotite crystallized from peraluminous magmas. Plagioclase grains show compositional variation within the albite to low oligoclase fields (Ab94An05Or01 - Ab88An11Or01), and the K-feldspar crystals have composition ranging from Or97Ab03 to Or92Ab08. Thermobarometric data point out crystallization at temperatures