Um Novo Tipo De Estrutura Em Lavas Ultramáficas: Greenstone Belt Crixás, Go

Low- and high-alumina komatiites of Goiás, Central Brazil

“…Since then, textural, structural, and chemical features of these rocks have been described by Saboia and Teixeira (1980), Montalvão and Bezerra (1981), Teixeira et al (1981), Montalvão et al (1982), Kuyumjian and Teixeira (1982), Kuyumjian and Dardenne (1982), Profumo (1993). Arndt et al (1989) point out that the Crixás komatiites have a unique and perhaps petrogenetically unusual chemical composition, in which the proportions of many immobile elements can be explained by neither magmatic processes nor thermal erosion and wall-rock assimilation during eruption but may have been remobilized during hydrothermal alteration and/or metamorphism.…”

Sm–Nd studies at Mina III gold deposit, Crixás greenstone belt, central Brazil: implications for the depositional age of the upper metasedimentary rocks and associated Au mineralization

“…Through deformation and metamorphism, these volcanics were transformed into schists with variable proportions of serpentine, talc, chlorite, carbonate, and actinolite. In areas of low strain, the metakomatiites are massive, light to dark green, fine-grained rocks, with locally well-preserved cumulate and tabular, radiated, porphyritic, harrisitic, and squeletal spinifex textures, as well as polyhedral jointing and orbicular structures (Saboia, 1979;Kuyumjian, 1981;Kuyumjian and Teixeira, 1982;Saboia and Teixeira, 1983).…”

Petrografia, geoquímica e geocronologia das rochas metavulcânicas e metaplutônicas dos Greenstone Belts faina e Serra de Santa Rita : implicações para o ambiente tectônico

“…No entanto, os depósitos singenéticos potenciais ainda necessitam de estudos mais aprofundados na região (Jost et al, 2014). Os metakomatiitos preservam feições vulcânicas originais, tais como texturas spinifex, cumulática, estruturas de resfriamento rápido, brechas de fluxo e pillow lavas (Danni et al, 1981;Teixeira, 1981;Teixeira et al, 1981;Kuyumjian & Teixeira, 1982;Danni et al, 1986;Profumo, 1993;Jost et al, 1995 (Jost et al, 2014). Rochas metavulcanoclásticas são descritas por Resende et al (1998) (Resende & Jost, 1994, 1995a primeiro ciclo e áreas-fonte cratônicas, com rochas de variados graus metamórficos (Resende et al, 1998;Carvalho et al, 2013) (Fig.…”

“…Primary volcanic features are locally preserved and include pillow lavas, spinifex and cumulate textures, polyhedral disjunctions, flux breccia and vesicles (Danni et al, 1981;Teixeira, 1981;Teixeira et al, 1981;Kuyumjian & Teixeira, 1982;Danni et al, 1986;Profumo, 1993;Jost et al, 1995). Intercalation of banded iron formation, gondite and metachert can occur in different proportions among the metavolcanic rocks.…”

“…Spinifex textures are well described in metakomatiites of the Crixás greenstone belt, in the northern portion of the Archean-Paleoproterozoic Terrane of Goiás (Teixeira et al, 1981;Teixeira et al, 1981;Kuyumjian & Teixeira, 1982), but textures of this kind are not yet recognized in the Faina and Serra de Santa Rita greenstone belts. However, the presence of pillowed structures in ultramafic rocks of the Serra de Santa Rita greenstone belt is extremely important because it indicates the subaqueous volcanic character of these sequences.…”