QUÍMICA MINERAL DA MUSCOVITA DE ROCHAS GRANÍTICAS E GREISENS DA SUÍTE INTRUSIVA VELHO GUILHERME, PROVÍNCIA ESTANÍFERA DO SUL DO PARÁ

Abstract

42 analyses were carried out by electronic microprobe on muscovite of the Antônio Vicente, Velho Guilherme, Mocambo, Benedita and Ubim/Sul granitic massifs and associated greisens of the Velho Guilherme Intrusive Suite, South Pará Tin Province. ln ali massifs the analyzed muscovite corresponds to a secondary phase, product of post-magmatic hydrothennal alteration which affected the granitic rocks in different degrees. Relatively to the greisen bodies, it corresponds to a primary phase. ln the Mocambo and Ubim/Sul granitic massifs it presents compositional variation from very dose to the muscovite end member until the phengite end member, characterizing a typical phengitic substitution [IVAI, VIAI -- IVSi, VIR(Fe,Mn,Mg,Ti)], since the proportion of Si and Fe is variable. ln the Antônio Vicente, Velho Guilherme and Benedita granitic massifs, this substitution was more homogenous, implying in structural formulas predominant1y phengitic. In relation to much for another granitics bodies in the region, as for another provinces.