INTEGRAÇÃO DE PARÂMETROS FÍSICOS DO MAGMA E COMPOSIÇÃO QUÍMICA DOS MINERAIS NA PETROGÊNESE DO GRANITO ITAPEMA, SC

Abstract

The Itapema Granite, located in the Catarinense Shield, southern Brazil, is a late-orogenic intrusion in the Paleoproterozoic Camboriu Complex gneisses, and shows U-Pb age of 2011±14Ma. It is composed of hornblende-biotite granodiorites and biotite monzogranites, which are distributed in two main facies: a fine to medium-grained equigranular facies and a heterogranular one. The Itapema Granite shows a well-developed magmatic foliation, abundant xenoliths of metamorphic rocks, and autoliths formed mainly by cumulatic plagioclase and amphibole. Lithostatic pressure during magmatic crystallization was estimated based on total-Al content in horblende and on the presence of magmatic epidote, at 4 to 4.5 kbar. Liquidus temperature, based on zirconium solubility curves, is estimated at about 800 0 C, and solidus temperature at about 700 0 C, which is indicated by the hornblende-plagioclase geothemometer. The generation of chessboard pattern in quartz suggests solidus temperatures over 665 to 690 0 C for pressures of 3.84 and 4.7 kbar, respectively. The natural viscosity of magmatic liquids varied from 10 4 to 10 5 Pa.s. Three rheological domains are presumed during magma crystallization: a solid domain, a mush domain, and a liquid one, which produced the autholiths and xenoliths, the heterogranular and the equigranular facies, respectively. The lithological variation of Itapema Granite is controlled mainly by mineral segregation and fractionation promoted by magmatic flow.