Caracterização Química de Cromitas nos Maciços de Cromínia e Mairipotaba, Goiás, Brasil

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:24:38Z No. of bitstreams: 0Bitstream added on 2014-05-27T14:35:44Z : No. of bitstreams: 1 2-s2.0-77951069166.pdf: 718441 bytes, checksum: 8eb48304099737179873b54a458b7597 (MD5) Made available in DSpace on 2014-05-27T11:24:38Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-01 Metaultramafic bodies tectonically emplaced within the metasedimentary sequence of the Araxá Group are associated with an ophiolitic melange in southeast Goiás. In the region of Crominia - Mairipotaba, they occur as lenticular bodies aligned E-W. Cumulate textures and geochemical data indicate that the parent rocks had harzburgitic to dunitic compositions. Relicts of primary crystals of olivine and orthopyroxene are suggestive of amphibolite facies metamorphic re-equilibration fabrics, even though the paragenesis and mineral associations of these metaultramafic rocks are typical of greenschist facies (T < 550°C and P = 5.5 kbar). The chromitites exhibit massive to breccioid structure and pull-apart texture, with chromite crystals around 0.5 mm in size. Chromite concentrations in the chromitite levels reach 70 to 85% by volume of the rock. The crystals are dispersed in the matrix, which is composed essentially of serpentine, and subordinately of chlorite and talc. The textures and geochemical data (Cr 2O 3 x TiO 2 and Mg x Cr ratios present in the chromitite) are similar to those observed in ophiolitic complexes. Hence, they correspond to allochthonous bodies (Alpine type) associated with an ophiolitic mélange. Departamento de Petrologia e Metalogenia UNESP, Av. 24-A 1.515, CEP 13506-900, Rio Claro, SP Pós-graduação em Geologia Regional Instituto de Geociências e Ciências Exatas UNESP, Rio Claro, SP Departamento de Mineralogia e Geotectônica Instituto de Geociências USP, São Paulo, SP Departamento de Petrologia e Metalogenia UNESP, Av. 24-A 1.515, CEP 13506-900, Rio Claro, SP Pós-graduação em Geologia Regional Instituto de Geociências e Ciências Exatas UNESP, Rio Claro, SP