PETROLOGIA DAS LAVAS ULTRABÁSICAS E BÁSICAS DA SEQUÊNCIA VULCÂNO-SEDIMENTAR MORRO DO FERRO. FORTALEZA DE MINAS (MG)

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Abstract
In this work the petrology of the Archean Morro do Ferro volcano-sedimentary sequence is being defined. The sequence is located in southwest part of the São Francisco Craton in the vicinity of the Fortaleza de Minas Village. The basal part of the Greenstone belt of Morro do Ferro is constituted of ultramafic flows with spinifex texture intercalated with aluminous tuffs, and iron formation. The medium part is formed of massive basaltic flows, now represented by tremolite-chlorite-epidote schist associated with reworked volcanic rocks, iron formation and talc schist lenses. The petrological studies indicated a fractionation trend wich starts with rocks of komatiitic afiliation (peridotite, pyroxenite, basalt) to rocks of tholeiitic composition (basalt). The fractionation is caracterized by a decrease in MgO content, a constant CaO/Al 2 O 3 ration, that reflects the olivine crystalization in the initial stages, followed by clinopiroxene and plagioclase. In this work the petrology of the Archean Morro do Ferro volcano-sedimentary sequence is being defined. The sequence is located in southwest part of the São Francisco Craton in the vicinity of the Fortaleza de Minas Village. The basal part of the Greenstone belt of Morro do Ferro is constituted of ultramafic flows with spinifex texture intercalated with aluminous tuffs, and iron formation. The medium part is formed of massive basaltic flows, now represented by tremolite-chlorite-epidote schist associated with reworked volcanic rocks, iron formation and talc schist lenses. The petrological studies indicated a fractionation trend wich starts with rocks of komatiitic afiliation (peridotite, pyroxenite, basalt) to rocks of tholeiitic composition (basalt). The fractionation is caracterized by a decrease in MgO content, a constant CaO/Al 2 O 3 ration, that reflects the olivine crystalization in the initial stages, followed by clinopiroxene and plagioclase.

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