Química mineral dos enclaves máficos hospedados no Complexo Cajazeiras e Granulito Novolândia, porção sul do Domínio Bacajá

Abstract

The area where the enclaves were found is located in Vila Cruzeiro do Sul, south of the Bacaja Domain, in Transamazonic Province, eastern portion of the Amazonian Craton. The Cajazeiras and Novolândia Granulite Complexes represents the dominant units in this area, they are composed of high-grade metamorphic rocks that constitute the Archean basement of the Bacajá Domain. Recently, scientific initiation researches, conclusion course paper and other activities about the rocks associated with the Cajazeiras and Novolândia Granulite Complexes, identified mafic enclaves and hosted them in three groups: amphibolites, transitional amphibolites and granulites. However, studies involving the mineral chemistry of these rocks are absent, making it difficult to understand the evolution of the temperature and pressure conditions during the metamorphism that these bodies were submitted. The chemical characterization from the essential minerals (pyroxene, amphibole and plagioclase) that constitute the mafic enclaves based on semiquantitative analyzes by EDS and in textural analyzes of these minerals can estimate the temperature (T) and pressure (P) conditions of the metamorphism. The pyroxenes analyzed are preferably in the field of augite. Amphiboles are from the calcium group and range from pargasite, ferro-edenite and edenite. The plagioclases have intermediate levels of anortite, occupying the field of andesine to bytownite. The formation temperatures of these enclaves vary between 737 to 844 ° C and pressures 4.7 to 7.7 Kbar belonging to granulite facies with intermediate P-T ratio.