Geologia e geofísica de rochas ultramáficas e carbonatitos ediacaranos intrusivos no Complexo Senador Elói de Souza, Maciço São José do Campestre, Província Borborema - NE do Brasil
Located in the São José do Campestre Massif, the Senador Elói de Souza Complex is a geological unit composed of 3.03 Ga granitic to tonalitic orthogneisses, mafic and ultramafic rocks characterized by metagabbros, metaclinopyroxenites and anorthosites with garnet and oligoclase, with the ultramaf...
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| Formato: | Dissertação |
| Idioma: | pt_BR |
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Universidade Federal do Rio Grande do Norte
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| Endereço do item: | https://repositorio.ufrn.br/handle/123456789/31690 |
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| Resumo: | Located in the São José do Campestre Massif, the Senador Elói de Souza Complex is a
geological unit composed of 3.03 Ga granitic to tonalitic orthogneisses, mafic and ultramafic
rocks characterized by metagabbros, metaclinopyroxenites and anorthosites with garnet and
oligoclase, with the ultramafic bodies and carbonatites dated by the U-Pb method at 600 ± 03
Ma. These bodies have contact features evidenced through magmatic breccias with carbonate
matrix and involving pyroxenite fragments. In addition, field data and 2D gravimetric modeling
allowed interpreting carbonatites and pyroxenites as ellipsoidal bodies, the first one less
expressive along the borders of the intrusion complex. The analysis of gravimetric data suggests
they ate shallow bodies and appear to truncate the low angle structures of the basement gneiss
rocks. Clinopyroxenites have a well-preserved igneous texture, a low fractional pattern of rare
earth elements [(LaN / YbN) = 8.9-49.8] and negative Eu anomaly of (Eu/Eu* = 0.39-0.88).
Carbonatites are calcite-rich, with diopside, phlogopite and olivine as main mafic phases, low
concentration of rare earth elements, with parallel and slightly inclined patterns [(LaN /YbN) =
1.5-8.6], in addition to enrichment of rare earth elements lightweight compared to heavy rare
earth elements. The distinct geochemical behavior between these lithologies in Harker-type
diagrams, in addition to a magmatic gap, suggests partial mixture of magmas. Occurrences of
symplectite between clinopyroxene and plagioclase and grossular partially consumed
generating scapolite indicate retrogression processes in clinopyroxenite. Recrystallization of
calcite, serpentinization of olivine and deformation of phlogopite in carbonatite indicate the
action of metamorphic events and fluid-rich (CO2, H2O) metasomatism. The geological and
geophysical data reported here may contribute to understand the Ediacaran mantelic events in
the Archean domain of the São José do Campestre Massif. |
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