Petrografia, Química Mineral E Geotermobarometria De Metapelito Do Grupo Carrancas Na Nappe De Luminárias (Mg)

Fumes, Regiane Andrade; Luvizotto, George Luiz; Moraes, Renato; Ferraz, Edson Ricardo Maia

doi:10.5016/geociencias.v36i4.12150

Cited by 2 publications

(3 citation statements)

References 5 publications

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“…15 Ma) and may indicate changes in the tectonometamorphic conditions along the P-T-t path. Records of prograde metamorphism steps in garnet porphyroblasts are confirmed by their chemical zoning, as documented by Fumes et al (2017). The older age presented by the included monazite represents the time of garnet and staurolite porphyroblasts crystallization at metamorphic peak conditions.…”

Section: Age Of Metamorphismmentioning

confidence: 67%

“…Silva (2010) described in the Carrancas Klippe, also composed of rocks from Carrancas Group, a metamorphic gradient that increases to the southeast, from upper greenschist facies to high pressure amphibolite facies in the transition to eclogite facies. A recent study in the metapelitic rocks of the Luminárias Nappe using the average PT mode of THERMOCALC indicates the presence of a metamorphic gradient with conditions increasing from greenschist/amphibolite facies, in the northern and center-northern portion, to amphibolite/eclogite facies in the southern portion (Fumes et al 2017).…”

Section: Geological Settingmentioning

confidence: 98%

“…A summary of mineral chemistry of the samples is further presented. A detailed description of the mineral chemistry of the studied rocks can be found in Fumes et al (2017).…”

Section: Sample Descriptions: Microstructures and Mineral Assemblagesmentioning

confidence: 99%

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Metamorphic modeling and petrochronology of metapelitic rocks from the Luminárias Nappe, southern Brasília belt (SE Brazil)

et al. 2019

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The Luminárias Nappe was formed in the agglutination of West Gondwana. A high-pressure metamorphic gradient oblique to the geological contacts is recorded in metapelitic rocks from this Nappe. In the northern portion, the metamorphic peak conditions are at high-pressure lower-amphibolite facies at 580 ± 4°C and ca. 0.9 GPa (Chl + Ky + St + Ms + Qtz + Rt); in the central portion, they are at high-pressure amphibolite facies at 600 ± 15°C and 1.1 ± 0.3 GPa (St + Bt + Grt + Ms + Qtz + Rt); and in the southern portion, they reach the eclogite facies at 630 ± 13°C and 1.4 ± 0.6 GPa (St + Ky + Grt + Ms + Qtz + Rt). Clockwise metamorphic P-T-t paths are registered in the studied rocks, with temperature and pressure increase followed by a strong decompression with retrograde phases as chloritoid (northern portion), chlorite and ilmenite (central portion) and biotite, chlorite and ilmenite (southern portion). U-Th-Pb T monazite ages range from 632 ± 4 Ma (southern portion) to 600 ± 8 Ma (northern portion included crystals in garnet and staurolite). The metamorphic age, the high-pressure conditions calculated in this paper and the clockwise metamorphic path indicate that the tectonic evolution of the Luminárias Nappe rocks is tightly associated with the subduction and collision processes of the southern Brasília belt. The overprint of the younger Ribeira belt is interpreted to be responsible for rock pile tilting, thus producing the oblique metamorphic gradient.

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Section: Age Of Metamorphismmentioning

confidence: 67%

Section: Geological Settingmentioning

confidence: 98%

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Metamorphic modeling and petrochronology of metapelitic rocks from the Luminárias Nappe, southern Brasília belt (SE Brazil)

et al. 2019

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Trace element changes in rutile from quartzite through increasing P–T from lower amphibolite to eclogite facies conditions

Fumes,

Luvizotto,

Pereira

et al. 2023

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Low concentrations of Na, Ca, K, Fe, Mg and Al in quartzite commonly prevent the crystallisation of index metamorphic minerals, inhibiting obtaining thermobarometric calculations. Quartzite typically contains quartz, zircon and rutile; therefore, single-element thermometers, such as Zr-in-rutile, may be applied. We investigate changes in trace-element composition of rutile from quartzite through increasing metamorphic conditions. Studied samples derive from a quartzite package (Luminárias Nappe, Minas Gerais, Brazil), where previous thermobarometric constraints on metapelites showed an increasing metamorphic grade southwards, from high-pressure lower amphibolite facies (580 °C; 0.9 GPa) to eclogite facies (630 °C; 1.4 GPa). Rutile from the lower-grade facies samples show a large spread in Zr concentrations, with the highest values corresponding to temperatures estimates higher than metamorphic conditions affecting those units, and thus interpreted as inherited detrital signatures. A narrower spread in Zr concentration is observed in rutile grains from the higher-grade, and estimated Zr-in-rutile temperatures agree with previous thermobarometric constraints. Therefore, we show that at 630 °C, Zr contents in detrital rutile from quartzites re-equilibrate. The comparison between the quartzite- and metapelite-hosting rutile grains from the same area shows that the resetting of the geothermometer in the latter seems to occur at slightly lower temperatures (∼50 ˚C lower). Supplementary material at https://doi.org/10.6084/m9.figshare.c.6793887

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Petrografia, Química Mineral E Geotermobarometria De Metapelito Do Grupo Carrancas Na Nappe De Luminárias (Mg)

Cited by 2 publications

References 5 publications

Metamorphic modeling and petrochronology of metapelitic rocks from the Luminárias Nappe, southern Brasília belt (SE Brazil)

Metamorphic modeling and petrochronology of metapelitic rocks from the Luminárias Nappe, southern Brasília belt (SE Brazil)

Trace element changes in rutile from quartzite through increasing P–T from lower amphibolite to eclogite facies conditions

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