Regiane A. Fumes

São Paulo State University | Unesp · Department of Geology

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-elem...

Inverted metamorphic gradients are recognized in several Proterozoic to Phanerozoic orogens. However, the mechanisms that are responsible for the formation of these gradients are still a matter of discussion. In the southern Brasília Orogen, an inverted metamorphic gradient is recorded in the Passos Nappe, that comprises a sequence of metasedimenta...

High-pressure metamafic rocks from the Passos Nappe, Southern Brasília Orogen, have been traditionally interpreted as highly retrogressed eclogites, even though no reliable P-T conditions were available thus far. In this work, samples from the least retrogressed sample were studied using petrography, mineral and whole-rock chemical analysis, thermo...

Metagreywacke is a very common rock type in orogenic settings. It occurs in several domains within the Neoproterozoic Southern Brasília Orogen, that registers convergent events related to the Western Gondwana formation. Studied rocks derive from the Luminárias Nappe, which is composed of metapelite (Campestre Unit), quartzite and metagreywacke (San...

We use a combination of several in situ techniques to assess the P‐T‐t path of high‐pressure granulites from the Passos Nappe in the Southern Brasília Orogen (SE ‐ Brazil). Quantitative element mapping and single‐element thermometers (Zr‐in‐rutile and Ti‐in‐quartz) are coupled with P–T pseudosections and monazite and rutile dating. Compositional an...

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 + R...

A Nappe Luminárias corresponde a estrutura alongada de orientação NNE-SSW, situada na porção sul do Orógeno Brasília e de idade neoproterozoica, na borda sul do Cráton do São Francisco. Tal estrutura é composta por metapelitos e quartzitos do Grupo Carrancas. O presente trabalho foca na caracterização metamórfica das suas rochas da, utilizando petr...

HP and UHP rocks are important tools to understand Earth Dynamics. However, assessing peak metamorphism and P-T history of such rocks is not an easy task. Pelitic HP-granulites have the assemblage Grt+Ky+KFs±Rt and the lack of Opx/Cpx has led to misclassification of some of these rocks as amphibolite facies. One major problem in determining peak P-...

Quartzite represents a poor chemical system and is fairly unreactive when compared to other metamorphic rocks. Thus, it is seldom used in metamorphic studies. Geothermometers based on the equilibrium ZrO2-TiO2-SiO2 might be used to assess temperature in this rock, since Zrn, Rt and Qtz are often present. However, it has been shown [1,2] that quartz...

The Luminárias Nappe is a NNE-SSW elongated structure, located in the southern portion of the Neoproterozoic Brasília Orogen, which borders the São Francisco Craton, MG, Brazil. It is composed of metapelite and quartzite from the Carrancas Group. The present work focuses on the metamorphic characterization of the Luminárias Nappe by means of petrog...

The Luminárias Nappe (LN) is located in the southern portion of the neoproterozoic Brasília Orogen, which borders the São Francisco Craton, both crop out in Minas Gerais, Brazil. The LN is composed of rocks of the Carrancas Group and high aluminium metapelites and quartzites are the main rock types. The present work focuses on the metamorphic chara...

A Nappe de Luminárias situa-se na porção meridional do Orógeno Brasília ou na zona de interferência entre as Faixas Brasília e Ribeira. A nappe está localizada no sudeste de Minas Gerais, entre as cidades de Luminárias, Carrancas e São Tomé das Letras. Da base para o topo ocorrem duas unidades, uma dominada por quartizito, e outra em que xisto pelí...

In Indiara region (GO), dozens of metamafic rocks lenses of various dimensions (metric to kilometric) occur, intercalated in gneisses of the Goiás Magmatic Arc and oriented according to the direction of the main foliation (Sn). These lenses consist of amphibolite (amphibole schists and amphibolites), have chemical compositions of sub-alkaline bas...