Structural Evolution of the Rio das Velhas Greenstone Belt, Quadrilátero Ferrífero, Brazil: Influence of Proterozoic Orogenies on Its Western Archean Gold Deposits
| Autor: | Orivaldo Ferreira Baltazar, Lydia Maria Lobato |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
lcsh:Mineralogy
lcsh:QE351-399.2 010504 meteorology & atmospheric sciences Proterozoic Archean Geochemistry Geology Orogeny paleoproterozoic orogeny Greenstone belt Fold (geology) 010502 geochemistry & geophysics Geotechnical Engineering and Engineering Geology 01 natural sciences Crenulation São Francisco Craton Syncline archean orogeny Shear zone Rio das Velhas greenstone belt Quadrilátero Ferrífero tectonic-structural analysis gold deposits 0105 earth and related environmental sciences |
| Zdroj: | Minerals, Vol 10, Iss 983, p 983 (2020) Minerals Volume 10 Issue 11 |
| Popis: | The Quadrilá tero Ferrí fero region is located in the extreme southeast of the Brasiliano Sã o Francisco craton, Minas Gerais state, Brazil. It is composed of (i) Archean TTG granite-gneaissic terranes (ii) the Archean Rio das Velhas greenstone belt (iii) the Proterozoic metasedimentary and metavolcano-sedimentary covers. The Rio das Velhas rocks were deposited in the synformal NW&ndash SE-directed Nova Lima basin. The Archean deformation converted the Nova Lima basin into an ample synclinorium with an eastern inverted flank. Archean orogenic gold mineralization within the Rio das Velhas greenstone belt rocks is controlled by NNW&ndash SSE-directed, Archean regional shear zones subparallel to the strata of the Nova Lima synclinorium borders. Transamazonian and Brasiliano orogenies are superposed onto the Archean structures that control gold mineralization. In the eastern domain, Brasiliano fold-and-fault belts prevail, whereas in the western domain Archean and Transamazonian structures abound. The present study focus mainly is the western domain where the Cuiabá Morro Velho, Raposos, Lamego and Faria deposits are located. Gold orebodies plunge to the E&ndash NE and are tectonically controlled by the Archean D1&ndash D2 deformation. The D3 Transamazonian compression&mdash which had a SE&ndash NW vector sub-parallel to the regional mineralized Archean foliation/bedding&mdash buckled these structures, resulting in commonly open, synformal and antiformal regional folds. These are well documented near the gold deposits, with NE&ndash SW axial traces and fold axes plunging to E&ndash NE. Such folds are normal to inverted, NW-verging, with an axial planar foliation dipping moderately to the SE. The Transamazonian compression has only been responsible for the reorientation of the mineralized Archean gold ores, due to coaxial refolding characterized by an opposite tectonic transport. It has therefore not caused any other significant changes. Thrust shear zones, sub-parallel to the strong Transamazonian foliation, have given rise to localized metric segmentation and to the dislocation of gold orebodies. Throughout the region, along the towns of Nova Lima to Sabará structures pertaining to the Brasiliano Araç uaí orogeny are represented only by gentle folding and by a discrete, non-pervasive crenulation cleavage. Thrust-shear zones and small-scale normal faults have caused, at most, metric dislocations along N&ndash S-oriented planes. |
| Databáze: | OpenAIRE |
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