MÁRMORES DA REGIÃO DE ITAOCA (ES) E ESCARNITOS NO CONTATO COM DIQUES MÁFICOS E FÉLSICOS: MINERALOGIA E PETROGÊNESE

Abstract

Skarns at the contact of marbles and mafic as well as felsic dikes located in the Itaoca region (Espírito SantoState, eastern Brazil) were investigated in terms of mineralogy and genesis. Marbles and the older mafic dykeswere affected by high grade metamorphism of Brasiliano age, as comproved by the presence of spinel. Theundeformed younger granitic dykes are post-tectonic. Skarns related to the granite dykes were formed as outcomesof silica addition in marble layers during the intrusion, generating zones composed of i)olivine + carbonate +pyroxene + amphibole ± phlogopite; ii)pyroxene + amphibole ± phlogopite ± scapolite, and iii)pyroxene ±phlogopite. The last mineral association occurs close to the granite and shows the maximum silica enrichment.Evidence of Ca-metassomatism in the granite is shown by the strongly zoned plagioclase crystals, which showcentral portions with An17 and border zone with An43. Skarns generated at the contact with amphibolite dykesare wider than the former, probably because the original contact metamorphic reaction zones generated duringthe intusion were reinforced by granulite facies metamorphism. The reaction aureoles display the followingmineral associations: i) carbonate ± olivine, ii) carbonate + diopside ± scapolite ± epidote, iii) plagioclase +diopside ± scapolite ± epidote, and iv) amphibole + plagioclase ± phlogopite ± hercinite ± grossularite. The firstassociation belongs to the marble at the contact, and the last to the amphibolite. There are mineralogical andtextural evidences for metamorphic and metassomatic reactions due to the migration of Ca, Mg and Si, leading,for example, to the scapolitization of the plagioclase.