| Autor: |
Nélson Angeli, Guillermo Rafael Beltran Navarro, Antenor Zanardo, Silvio Roberto Farias Vlach |
| Jazyk: |
English<br />Portuguese |
| Rok vydání: |
2010 |
| Předmět: |
|
| Zdroj: |
Geologia USP. Série Científica, Vol 10, Iss 1, Pp 87-99 (2010) |
| Druh dokumentu: |
article |
| ISSN: |
1519-874X |
| Popis: |
Metaultramafi c bodies tectonically emplaced within the metasedimentary sequence of the Araxá Group are associatedwith an ophiolitic melange in southeast Goiás. In the region of Cromínia - Mairipotaba, they occur as lenticular bodiesaligned 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-equilibrationfabrics, even though the paragenesis and mineral associations of these metaultramafi c rocks are typical of greenschistfacies (T < 550ºC and P = 5.5 kbar). The chromitites exhibit massive to breccioid structure and pull-apart texture, withchromite crystals around 0.5 mm in size. Chromite concentrations in the chromitite levels reach 70 to 85% by volumeof the rock. The crystals are dispersed in the matrix, which is composed essentially of serpentine, and subordinately ofchlorite and talc. The textures and geochemical data (Cr2O3 x TiO2 and Mg x Cr ratios present in the chromitite) are similarto those observed in ophiolitic complexes. Hence, they correspond to allochthonous bodies (Alpine type) associated withan ophiolitic mélange. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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