Ultra-high temperature metamorphism in the Guaxupé Complex: a lower crust segment

Abstract

The area is located at the northern boundary of the Guaxupé Complex, which corresponds to the northern domain of the Socorro-Guaxupé Nappe, in the Southern Brasília Orogen, close to the Varginha Shear Zone. This study integrates petrography, mineral chemistry, optimized geothermobarometry, and trace elements thermometry data, aiming to define and characterize the metamorphic conditions and the P-T path of the granulitic rocks from the northern portion of the Guaxupé Complex. In the area, the Guaxupé Complex consists predominantly of ortho-derived rocks represented by granulitic gneisses (orthopyroxene gneisses) of felsic to mafic composition with clinopyroxene, garnet, amphibole, biotite, and rare rutile. The calculated pressure and temperature conditions record metamorphic peak around 1,078°C and 14.8 kbar, compatible with ultra-high temperature metamorphism conditions, marked by grt + cpx + opx + pl ± qtz ± rt mineral assemblages, and granulite facies re-equilibration in the sillimanite stability field at P-T conditions of 930 to 800°C and 13.5 to 11.0 kbar. The results are compatible with deeper portions of the lower crust involved in a continental collision and suggest a clockwise P-T path, typical of crustal thickening zones, followed by near-isothermal decompression during tectonic exhumation.

KEYWORDS:
Southern Brasília Orogen; Guaxupé Complex; Granulites; UHT metamorphism; lower crust

INTRODUCTION

Orogens record tectono-metamorphic processes that affected continental crust rocks at convergent plate boundaries. The roots of ancient orogens carry fundamental information on deep portions of the crust, which can be used to understand and reconstruct the geodynamic evolution of a region by unraveling the pressure-temperature-time-deformation (P-T-t-d) path (Brown 2007, Pauly et al. 2016).

Ultra-high temperature (UHT) metamorphism is a subdivision of granulite facies metamorphism and is defined as crustal metamorphism at temperatures above 900°C and pressures not exceeding the sillimanite stability field (Harley 1998, 2008, 2016, Brown 2007, Kelsey and Hand 2015).

UHT metamorphism provides evidence that tectonic processes may operate under extreme thermal conditions. Identifying and obtaining accurate quantitative P-T conditions and P-T metamorphic history of rocks that attained extreme conditions is crucial to provide valuable insights into the tectono-metamorphic settings, tectonic processes in UHT granulitic terranes and implications for crust evolution (Harley 1998, 2004, 2008, 2016, Brown 2007, Kelsey 2008, Kelsey and Hand 2015). However, identify the metamorphic peak conditions of UHT granulitic terranes is potentially hampered by the application of conventional element exchange geothermobarometry, due to diffusional resetting during cooling, significantly modifying their compositions (Moraes et al. 2015, Pape et al. 2016).

In the Southern Brasília Orogen, central-south Brazil, the Guaxupé Nappe comprises granulitic terranes that record high to ultra-high temperature metamorphism conditions (Iyer et al. 1996, Campos Neto and Caby 1999, 2000, Del Lama et al. 2000, Garcia and Campos Neto 2003, Nascimento 2010, Nascimento and Oliveira 2012, Rocha et al. 2017, 2018, Tedeschi et al. 2018, Leme 2019).

In order to refine the P-T conditions and the P-T path of Guaxupé Complex granulites, this contribution highlights more recent geothermobarometric methods applied to granulites bearing grt-opx-cpx ± rt of the Guaxupé Complex northern portion. This approach includes optimized geothermobarometry (Thermocalc software and Al- orthopyroxene thermobarometry) and the first data of Zr-in-rutile thermometry in ortho-derived granulitic rocks of the region. This study integrates petrography, mineral chemistry, optimized geothermobarometry, and trace elements thermometry data, aiming:

• to define and characterize the metamorphic conditions and the P-T path of the granulitic rocks from the Guaxupé Complex northern portion;

• to contribute to discussions about the tectono-metamorphic evolution of the Southern Brasília Belt.

GEOLOGICAL SETTING

The Brasília Belt comprises an orogenic system located in the eastern portion of the Tocantins Structural Province (central Brazil), extending for more than 1,200 km (from the central portion of Tocantins State to the NE portion of São Paulo State), along the western margin of the São Francisco Craton and is oriented to NS and NNE-SSW direction. This orogenic system results from the convergence of the Amazonian, São Francisco and Paranapanema paleocontinents during the West Gondwana amalgamation, Brasiliano–Pan African Event, in the Neoproterozoic (Brito Neves et al. 1999, 2014, Dardenne 2000, Alkmim et al. 2001, Cordani et al. 2003, Fuck et al. 2017, Valeriano 2017) (Fig. 1).

Figure 1
Map showing the tectonic units that compose the Brasília Belt.

The Brasília Belt is segmented into two orientation domains and metamorphic-deformational styles (Valeriano et al. 2004, 2008, Fuck et al. 2017, Valeriano 2017), Northern Brasília Belt (NE-oriented) and Southern Brasília Belt (NW-oriented), where the study area is located.

The Southern Brasília Belt results from the Neoproterozoic collision between the active margin of the Paranapanema Block and the passive margin of the São Francisco paleocontinent, which involved subduction and collisional orogeny, and comprises a tectonic stack of E-verging nappes (Campos Neto and Caby 1999, 2000, Trouw et al. 2000, 2013, Valeriano et al. 2004, 2008, Mantovani and Brito Neves 2005, 2009, Valeriano 2017). Each nappe system represents a lithostructural domain with distinctive tectono-metamorphic features, including from WSW to ENE:

• Socorro-Guaxupé Nappe (SGN), represented by a magmatic arc domain (Campos Neto and Caby 1999, 2000, Trouw et al. 2000, 2013, Mora et al. 2014);

• Andrelândia Nappe System, including strongly deformed metasedimentary units related to an accretionary prism (Campos Neto and Caby 1999, Campos Neto et al. 2010, 2011);

• Carrancas and Lima Duarte Nappes System, represented by a domain related to the passive continental margin of the São Francisco Craton (Trouw et al. 2000, 2013, Campos Neto et al. 2010, 2011).

The SGN represents a thick section of the lower continental crust, interpreted according to some authors, as the root of a magmatic arc developed on the active margin of the Paranapanema Plate (Campos Neto and Figueiredo 1992, Campos Neto and Caby 1999, 2000, Trouw et al. 2000, Campos Neto et al. 2004, Vinagre et al. 2014). The SGN consists of three units (Campos Neto and Caby 1999, 2000, Campos Neto et al. 2011, Mora et al. 2014, Tedeschi et al. 2015):

• Basal Granulite Unit, composed mainly of banded granulites with charnockitic to enderbitic leucosomes;

• Diatexite Unit, consisting of orthogneisses and metaluminous migmatites;

• Metatexite Unit, represented by paragneisses and metasedimentary migmatites.

The SGN is subdivided into two major domains by the NE–SW trending Ouro Fino Shear Zone. The northern domain and focus of this paper, Guaxupé Nappe, Guaxupé Domain, or Guaxupé Complex (the term used in this contribution — Del Lama et al. 2000, Zanardo 2003, Zanardo et al. 2006), and the southern, Socorro Nappe, Socorro Domain or Socorro Complex. The Ouro Fino Shear Zone is 300 km long and cuts a wide tectonic window consisting of Archean and Paleoproterozoic basement migmatitic orthogneisses (Amparo, Serra Negra and Pouso Alegre Complex) (Trouw et al. 2013, Cioffi et al. 2016, Oliveira et al. 2019) (Fig. 2).

Figure 2
Geological map highlighting the tectonic units of the Southern Brasília Belt The rectangle is the localization of Figure 3.

The Guaxupé Complex is composed of intermediate to acidic ortho-derived lithologies, mainly represented by banded felsic to mafic orthopyroxene-bearing granulites, biotite, and amphibole-bearing orthogneisses, and syenogranitic to tonalitic biotite-bearing granitoids. Interleaved with the ortho-derived rocks, subordinated metasedimentary rocks (pelitic, psammitic, and carbonatic) occur (Zanardo 1992, Campos Neto and Caby, 1999, 2000, Del Lama et al. 2000, Zanardo et al. 2006).

According to Del Lama et al. (2000), the Guaxupé Complex can be divided into three domains based on pressure variation:

• N-NE domain, represented by high-pressure grade;

• intermediate domain, with intermediate to high-pressure grade;

• S-SW domain, represented by low- to intermediate-pressure grade.

High to ultra-high temperature metamorphic conditions were determined for the Basal Granulite Unit of the Guaxupé Complex, indicating metamorphic P-T peak conditions above 900°C and 10 kbar (Del Lama et al. 2000, Campos Neto and Caby 2000, Nascimento 2010, Rocha et al. 2018, Tedeschi et al. 2018, Leme 2019). Similar P-T conditions were also reported for the adjacent Diatexite and Metatexite units (Rocha et al. 2017).

The study area (Fig. 2) is located in the region of Guaxupé–Guaranésia–Monte Belo cities, close to the Varginha Shear Zone (Cavalcante et al. 1979), northern boundary of the Guaxupé Complex, in the Basal Granulite Unit.

ANALYTICAL METHODS

Petrographic and mineral chemistry analyses were performed at the Department of Petrology and Metallogeny (DPM) laboratories of the Institute of Geosciences and Exact Sciences (Instituto de Geociências e Ciências Exatas – IGCE), Universidade Estadual Paulista “Júlio de Mesquita Filho” (Unesp), Rio Claro Campus.

Mineral chemistry analyses were performed using a JEOL JXA-8230 Superprobe Electron Microprobe (EPMA). Garnet, orthopyroxene, clinopyroxene, plagioclase, orthoclase, amphibole, and biotite were analyzed with an acceleration voltage of 15 kV, beam current of 20 nA, and a spot size of 10 µm, using minerals and synthetic oxides as standard elements. The counting time for the major elements was 10 seconds at the peak and 5 seconds for each background position; for minor elements, 20 seconds were used at the peak and 10 seconds for each background position.

Mineral activity calculations of the analyzed phases and mineral structural formulas were obtained by AX (Holland and Powell 2000) and MINPET 2.02 (Richard 1995) software, in addition to the use of structural formula calculation worksheets according to Deer et al. (1992, 1997a, 1997b, 1997c, 2004).

Rutile EPMA trace elements analyses (Si and Zr) were performed with an acceleration voltage of 20 kV, beam current of 80 nA, and spot size of 5 µm, according to the method of Luvizotto et al. (2009). Analyses with Si concentrations above 300 ppm were excluded, as recommended by Zack et al. (2004).

Calculations of temperature and pressure conditions were obtained by THERMOCALC, version 3.26 (avPT mode) (Powell and Holland 1994), and RCLC (Thermobarometry Corrected for Retrograde Exchange) program by Pattison et al. (2003), and by the Zr-in-rutile geothermometer, calibrated by Tomkins et al. (2007).

FIELD RELATIONSHIPS

The study area is located in the northern part of the Guaxupé Complex, to the south of the Varginha Shear Zone (VSZ), in the region of Guaxupé–Guaranésia–Monte Belo cities. The area corresponds to the northern portion of the Basal Granulite Unit of the SGN.

The VSZ delimits the northern boundary of the Guaxupé Complex and separates UHT rocks, represented by the Guaxupé Complex, to the south, from high-pressure rocks (Del Lama et al. 1994, Leme 2019, Leme et al. 2019) attributed to the Araxá Group, to the north. The sinistral transcurrent VSZ has an approximately E-W direction and inflects toward SE in the eastern part, at the height of Monte Belo municipality, where it acquires lateral ramp features (Zanardo 1992, Morales 1993, Del Lama et al. 2000).

The location of the studied samples is shown in Figure 3.

Figure 3
Simplified geological map showing the location of the studied samples.

In the study area, the Guaxupé Complex consists predominantly of basic to acidic ortho-derived rocks, with a prevalence of intermediate compositions, associated with rare intercalations of metasedimentary rocks, both metamorphosed at granulite facies.

Ortho-derived rocks are represented by banded to homogeneous granulitic gneisses (orthopyroxene gneisses) of felsic to mafic composition, with or without clinopyroxene, garnet, amphibole, and less often biotite and rutile associated, interlayered with granitic to tonalitic banded gneisses with amphibole and/or biotite, which may also contain garnet and clinopyroxene, and mafic granulite lenses.

The ortho-derived lithologies are fine to coarse-grained, and the gneiss banding is defined by the alternation of continuous to discontinuous layers, with variable thickness (submillimeter to subcentimeter), marked by compositional variation between felsic (quartz-feldspathic) and mafic (pyroxenes, amphibole, garnet, and biotite) beds. The occurrence of garnet in granulitic gneisses is more common in the northern boundary of the Guaxupé Complex, near VSZ southeast inflection, in Monte Belo region.

The metasedimentary rocks associated with this unit are subordinate in the study area. These rocks are mainly represented by fine to coarse-grained quartzites, quartz gneisses, and quartz schists bearing garnet, sillimanite, orthoclase, and rutile, and occur in discontinuous centimeter-to-metric lenses interlayered with the ortho-derived rocks; or as discontinuous metric-to-decametric bands that narrow in the granulitic gneisses.

The rocks of the Guaxupé Complex exhibit penetrative foliation with W to WNW direction, parallel to the compositional banding and with a moderate to high dip angle toward SSW. Frequently, the main foliation is blastomylonitic with different development degrees, comprising anastomosed and lenticular forms (Fig. 3).

PETROGRAPHY AND MINERAL CHEMISTRY

Based on the mineralogical and textural aspects, three samples of garnet granulitic gneiss (samples: TGL-13, TGL-32, and TGL-58) and one sample of basic granulite (sample MAG-11) were selected for mineral chemical analysis. Representative results of major element composition of garnet, clinopyroxene, orthopyroxene, feldspar, amphibole, and biotite are presented in the Supplementary Tables (Tables S.1, S.2, S.3, S.4, and S.5). Mineral abbreviations are according to Whitney and Evans (2010).

Garnet granulitic gneiss

The garnet granulitic gneiss occurs immediately to the south of the VSZ. This rock type is characterized by a predominantly intermediate composition and fine- to medium-grained. The texture is oriented and granoblastic with discontinuous porphyroblastic domains, which define the foliation (Fig. 4A).

The main mineralogy is composed of plagioclase (40–55%), quartz (1–25%), garnet (5–20%), clinopyroxene (7–15%), orthopyroxene (5–13%), orthoclase (traces — 5%), amphibole (0–10%), and biotite (0–4%). Opaque minerals (2–3%), apatite (traces — 1%), zircon (traces), and rutile (0–2%) occur as accessory minerals.

Subhedral, anhedral, and rounded garnet (Alm_42-51Prp_30-39Grs_9-17Adr_<1-7Sps_<1-3) occur in diffuse porphyroblastic aggregates, with grains dimensions ranging from 1.0 to 4.5 mm. The crystals are poikilitic, with inclusions of quartz, plagioclase, opaque minerals, clinopyroxene, and less often rutile and biotite, and frequently exhibit irregular shapes with lobate boundaries (Figs. 4B, 4C, and 4D). Some crystals are corroded and replaced by clinopyroxene and orthopyroxene and secondarily by biotite. The compositional profiles are relatively flat and homogeneous, with slight chemical variations toward the crystals rims, defined by an increase in Fe²⁺ and a decrease in Mg. Grossular and andradite concentrations exhibit reverse trend profiles but do not show well-defined chemical zoning. Spessartite concentrations are low and homogeneous across all crystals (Figs. 4E, 4F, and 4G).

Figure 4
Mineralogical and textural aspects from garnet granulitic gneiss. (A) Photograph of thin-section of garnet granulitic gneiss (sample TGL-13), illustrating the granoblastic texture with porphyroblastic domains and the location of analyzed garnet crystals. (B, C, D) Detail of the textural aspects of garnet crystals and the location of compositional profiles. (E, F, G) Compositional profiles across garnet crystals in garnet granulitic gneiss.

Plagioclase (An_34-38) occurs as anhedral to subhedral crystals and is commonly elongated, with polygonal to predominantly lobate boundary. The crystals may be antiperthitic or myrmekitic (Fig. 5A). Quartz forms ribbons and can reach dimensions of up to 5.0 mm in length (Fig. 5B). In the more mafic and plagioclasitic portions, quartz is interstitial and vermiform. Orthoclase is anhedral and occurs as interstitial crystals, forming antiperthitic texture.

Figure 5
Representative photomicrographs showing detail of textural aspects from garnet granulitic gneiss. (A) Antiperthitic texture in plagioclase crystal (crossed polarized light) (Sample TGL-13); (B, C) Granoblastic oriented texture showing the main mineral assemblage (grt + cpx + opx + pl), with emphasis on quartz ribbons in (B) (plane polarized light) (Sample TGL-32 and Sample TGL-58, respectively); (D, E) Pyroxene crystals (cpx and opx) partially replaced by amphibole (plane polarized light) (Sample TGL-13); (F) Biotite corroding garnet crystals (plane polarized light) (Sample TGL-58); (G) Rutile inclusions in garnet and rutile grains in matrix (plane polarized light) (Sample TGL-58).

Clinopyroxene is classified as sahlite (Wo_39-47En_33-39Fs_15-20), has X_Mg content ranging from 0.58 to 0.73, Al core content between 0.17 to 0.28 atoms per formula unit (a.p.f.u.), and Na core content between 0.04 to 0.09 a.p.f.u. It occurs as subhedral to anhedral crystals, partially replaced by amphibole. Anhedral to rounded orthopyroxene is hypersthene (En_57-62), has X_Mg content ranges from 0.58 to 0.62 and Al core content between 0.08 to 0.17 a.p.f.u. The crystals are partially replaced by clinopyroxene, amphibole, and biotite (Figs. 5C, 5D, and 5E).

Amphibole, where present, exhibit calcium composition (Ca_B > 1.5, Na_A+ K_A > 0.5, Ti ≪ 0.5 e Si ≪ 6.5; Leake et al. 1997) and is classified as magnesiohastingsite. Ti content is high and ranges from 0.26 to 0.35 a.p.f.u. The crystals may be well-developed or occur as small crystals replacing the pyroxenes associated with the metamorphic re-equilibration process (Figs. 5D, and 5E).

Biotite (X_Mg = 0.69 to 0.72), where present, is classified as phlogopite (Fe/(Fe + Mg) × Al^IV) and has composition characterized by high Ti core contents (0.60–0.64 a.p.f.u.). It is frequently associated with amphibole and garnet replacement (Fig. 5F).

Opaque minerals include ilmenite, magnetite, chalcopyrite, and pyrrhotite. Ilmenite crystals occur with exsolution lamellae of magnetite. Rutile is rare and occurs in garnet granulitic gneiss in the northern portion of the Guaxupé Complex, close to the VSZ inflection. It occurs as subprismatic to anhedral crystals, with dimensions up to 0.3 mm, associated with mafic minerals, dispersed in quartz-feldspathic granoblastic beds, or included in garnet crystals (Fig. 5G). Rutile crystals are clear and homogeneous (Figs. 6A, and 6B) or may have exsolution lamellae of ilmenite (Figs. 6C, and 6D).

Figure 6
Back-scattered electron (BSE) images of representative rutile grains in garnet granulitic gneiss (Sample TGL-58). (A) Homogeneous anhedral rutile crystal in the rock matrix; (B) homogeneous rounded rutile inclusion in garnet; (C) anhedral rutile inclusion with thin ilmenite exsolution lamellae; (D) subhedral rutile crystal with thin ilmenite exsolution lamellae in the rock matrix.

Basic granulite

Basic granulites occur as metric lenses interlayered with granulitic gneisses and garnet granulitic gneisses. This rock type exhibits massive structure with incipient to prominent orientation and decussate granoblastic texture domains with euhedral amphibole and clinopyroxene crystals, to nematoblastic domains (Fig. 7A). The mineralogy consists of amphibole (± 45%), clinopyroxene (± 35%), plagioclase (± 10%), orthopyroxene (± 8%), garnet (± 2%), and opaque minerals (≪ 1%).

Figure 7
Mineralogical and textural aspects from basic granulite (Sample MAG-11). (A) Photograph of thin-section of basic granulite, illustrating the granoblastic texture, mineral assemblage and the location of analyzed garnet crystal; (B, C) pyroxene crystals (cpx and opx) partially replaced by amphibole (plane polarized light); (D) detail for garnet texture showing the location of compositional profile (plane polarized light); (E) compositional profile across garnet.

Amphibole has calcium composition (Ca_B ≥ 1.5, Na_A + K_A ≥ 0.5, Ti ≤ 0.5 e Si ≪ 6.5; Leake et al. 1997) and is classified as magnesiohastingsite, with Ti core contents ranging from 0.18 to 0.23 a.p.f.u. It occurs as euhedral to subhedral crystals with decussate texture; and also as anhedral crystals replacing pyroxene (clinopyroxene and orthopyroxene) with nematoblastic texture. Amphibole does not show compositional zoning, and chemical differences were not observed between the euhedral and anhedral crystals.

Clinopyroxene is classified as sahlite (Wo_41-44En_36-38Fs_13-15) and exhibits no significant core-rim compositional variation. X_Mg contents range from 0.68 to 0.74, Al core content between 0.20 and 0.26 a.p.f.u., and Na core content between 0.05 and 0.07 a.p.f.u. The crystals are subhedral to anhedral and may occur partially replaced by amphibole, and with orthopyroxene exsolution lamellae. Orthopyroxene is hypersthene (En_63-65), with X_Mg contents ranging from 0.65 to 0.67 and Al core content from 0.12 to 0.18 a.p.f.u. They are frequently anhedral, replaced mainly by amphibole and, less often, by clinopyroxene (Figs. 7B, and 7C).

Plagioclase (An_43-54) occurs in discontinuous domains in tabular to anhedral shapes, with dominantly polygonal boundary. The crystals exhibit subtle compositional zoning, marked by a slight increase in Ca and a decrease in Na toward the rims of the crystals.

Garnet (Alm_40-44Prp_36-41Grs_9-12Adr_5-8Sps_2-3) is rare and occurs as anhedral to rounded crystals, with variable dimensions (from 0.3 to 4.5 mm). The compositional profiles are almost flat, marked by weak chemical zoning, with an increase in Fe²⁺ and a decrease in Mg toward the crystals rims. Grossular and andradite concentrations exhibit reverse trend profiles but do not show well-defined chemical zoning. Spessartite concentrations are homogeneous and low across all crystals (Figs. 7D).

Granulitic gneiss

Toward the south and southwest of the Guaxupé Complex, the study area is dominated by granulitic gneisses (orthopyroxene gneisses), with oriented granoblastic texture and nematoblastic domains. The mineralogy consists of plagioclase (30–60%), quartz (traces-20%), potassium feldspar (1–35%), orthopyroxene (5–10%), clinopyroxene (0–10%), amphibole (0–20%), biotite (0–5%), and opaque minerals (2–4%, in addition to apatite (± 1%) and zircon (traces) (Figs. 8A, 8B, and 8C).

Figure 8
Representative photomicrographs showing detail of textural aspects and mineral assemblage from granulitic gneiss and metasedimentary rocks. (A, B, C) Oriented granoblastic texture consisting of quartz-feldspathic beds and granoblastic/nematoblastic domains composed of mafic minerals (opx, cpx, and amp) (plane polarized light); (D) orthopyroxene crystals partially replaced by amphibole (plane polarized light); (E) oriented granoblastic to porphyroblastic texture with discontinuous oriented nematoblastic domains composed of sillimanite (plane polarized light); (F) aggregates of prismatic sillimanite crystals associated with ilmenite (plane polarized light).

Plagioclase (oligoclase and andesine) has subhedral to anhedral shapes and is commonly elongated, with lobate to polygonal boundary. The crystals may be myrmekitic or antiperthitic and dimensions range from 0.1 to 3.0 mm.

On the acidic and intermediate terms, quartz occurs as ribbons up to 4.5 mm in length. It may have a very restricted occurrence in more plagioclasitic and basic terms, with interstitial disposition.

Potassium feldspar (orthoclase and microcline) is elongated and has subhedral to anhedral shapes, with dimensions up to 5.0 mm. The crystals exhibit perthitic to mesoperthitic texture, with lobate boundary.

Orthopyroxene is subhedral to anhedral, commonly elongated, with dimensions ranging from 0.2 to 2.0 mm. The crystals occur partially replaced by amphibole or exhibit exsolution lamellae of clinopyroxene. Where present, anhedral to subhedral diopside crystals occur with dimensions of up to 4.0 mm and may be partially replaced by amphibole or orthopyroxene, and may exhibit exsolution lamellae of orthopyroxene.

Hornblende occurs as well-developed subhedral crystals up to 3.0 mm in length, or as medium-sized anhedral crystals in order of 0.4 mm, associated with pyroxene replacement (Fig. 8D). In some portions, amphibole crystals show equilibrium texture with pyroxenes. Brownish biotite occurs as a result of amphibole and pyroxene replacement.

Metasedimentary rocks

Metasedimentary rocks show inequigranular oriented granoblastic to porphyroblastic texture, with discontinuos nematoblastic domains. This rock type is composed of quartz (50–65%), garnet (15–30%), potassium feldspar (0–25%), sillimanite (10–15%), biotite (traces-5%), muscovite (0–3%), and accessory mineralogy composed of rutile (≪ 1–2%), opaque minerals (≪ 1–3%), zircon (≪ 1%), and apatite (≪ 1%) (Fig. 8E).

Quartz has an anhedral shape, is elongated and exhibits a high degree of recrystallization. Anhedral to rounded garnet crystals range in size from 2.0 to 8.0 mm and are poikilitic, with inclusions of opaque minerals, rutile, sillimanite, quartz, and biotite. Sillimanite has prismatic to anhedral shape, with dimensions ranging from less than 0.1 to 3.0 mm, and occurs concentrated in discontinuous domains, forming oriented lenticular aggregates with strong undulose extinction (Fig. 8F). Rutile crystals occur included in garnet crystals, dispersed in quartz granoblastic beds, or associated with sillimanite crystals and opaque minerals. Biotite and muscovite occur as small tabular crystals resulting from the replacement of garnet and sillimanite.

P-T CONDITIONS OF METAMORPHISM

High-grade metamorphism conditions were calculated by optimized geothermobarometry using THERMOCALC and RCLC software, both using an internally consistent thermodynamic database to calculate pressure and temperature conditions. The same combined analyses of garnet, orthopyroxene, plagioclase, and biotite were used for the calculations by the Average P-T and Al-solubility in orthopyroxene methods.

Thermocalc (average P-T)

The pressure and temperature results obtained for each sample and the mineral assemblage used for the calculation are presented in Table 1. Average P-T calculations for the garnet granulitic gneiss (samples TGL-13, TGL-32, and TGL-58) were performed with and without orthoclase in the mineral assemblage. The calculations for hydrated mineral assemblage were obtained with ɑ_H2O values of 0.3, which resulted in the smallest uncertainties.

Table 1
P-T conditions calculated by THERMOCALC software (Average P-T).

Sample	Mineral assemblage	P (Kbar) / T (°C)	Correlation
TGL-13	Pl4_6 Grt8_14 Cpx7_1 Opx3_3 Amp2_1 Qtz	12.2 ± 0.6 / 961 ± 29	0.474
TGL-13	Pl4_1 Grt6_13 Cpx1_1 Opx3_1 Amp4_1 Qtz	12.8 ± 0.5 / 968 ± 30	0.499
TGL-13	Pl7_1 Grt10_5 Cpx1_2 Opx5_3 Amp4_3 Qtz	11.3 ± 0.7 / 957 ± 27	0.516
TGL-13	Pl4_6 Grt8_14 Cpx7_1 Opx3_3 Amp2_1 Qtz Or4	11.3 ± 0.7 / 900 ± 37	0.568
TGL-13	Pl4_1 Grt6_13 Cpx1_1 Opx3_1 Amp4_1 Qtz Or10	11.4 ± 0.7 / 887 ± 36	0.562
TGL-13	Pl7_1 Grt10_5 Cpx1_2 Opx5_3 Amp4_3 Qtz Or4	11.6 ± 0.7 / 889 ± 36	0.640
TGL-32	Pl14 Grt8_8 Cpx8 Opx18 Qtz	14.7 ± 1.3 / 1,199 ± 99	0.893
TGL-32	Pl15 Grt1_17 Cpx10 Opx5 Qtz	13.8 ± 1.6 / 1,108 ± 121	0.923
TGL-32	Pl8 Grt4_13 Cpx13 Opx16 Qtz	13.8 ± 1.5 / 1,123 ± 118	0.915
TGL-32	Pl14 Grt8_8 Cpx8 Opx18 Qtz Or1	13.2 ± 1.6 / 1,039 ± 116	0.914
TGL-32	Pl15 Grt1_17 Cpx10 Opx5 Qtz Or9	14.6 ± 1.6 / 1,124 ± 114	0.912
TGL-32	Pl8 Grt4_13 Cpx13 Opx16 Qtz Or1	12.7 ± 1.3 / 988 ± 98	0.910
TGL-58	Pl4 Grt11_4 Cpx23 Opx21 Amp1 Bt4 Qtz	12.0 ± 0.9 / 958 ± 38	0.623
TGL-58	Pl2 Grt11_13 Cpx22 Opx25 Amp3 Bt3 Qtz	12.3 ± 0.6 / 928 ± 28	0.631
TGL-58	Pl1 Grt8_3 Cpx13 Opx17 Amp4 Bt5Qtz	12.7 ± 1.0 / 979 ± 43	0.468
TGL-58	Pl4 Grt11_4 Cpx23 Opx21 Amp1 Bt4 Qtz Or1	11.4 ± 0.9 / 906 ± 39	0.632
TGL-58	Pl2 Grt11_13 Cpx22 Opx25 Amp3 Bt3 Qtz Or2	10.9 ± 1.0 / 910 ± 43	0.656
TGL-58	Pl1 Grt8_3 Cpx13 Opx17 Amp4 Bt5 Qtz Or1	10.91 ± 0.9 / 915 ± 41	0.656
MAG-11	Pl20 Grt5_6 Cpx22 Opx19 Amp26	12.8 ± 0.9 / 929 ± 29	0.350
MAG-11	Pl18 Grt5_7 Cpx22 Opx13 Amp35	13.0 ± 0.8 / 955 ± 27	0.354
MAG-11	Pl21 Grt3_8 Cpx30 Opx14 Amp29	12.9 ± 0.7 / 948 ± 34	0.359

• Samples: i) garnet granulitic gneiss: TGL-13: amp-cpx-grt granulitic gneiss; TGL-32: grt-cpx granulitic gneiss; TGL-58: cpx-grt granulitic gneiss with bt, amp and rt; ii) basic granulite: MAG-11: cpx-amp basic granulite with grt. The numbers subscribed to the minerals indicate the mineral chemical analysis point used in the geothermobarometric calculations (See Supplementary Tables).

For garnet granulitic gneiss with amphibole (sample TGL-13), the mineral assemblage considered was sahlite + hypersthene + almandine + andesine + Mg-hastingsite + quartz ± orthoclase. In calculations in which orthoclase is not considered, average P-T values range from 11.3 ± 0.70 to 12.8 ± 0.50 kbar and from 957 ± 27 to 968 ± 30°C, with correlations of the order of 0.5 (Fig. 9A, Tab. 1). Considering potassium feldspar in the mineral assemblage, the P-T conditions are slightly lower and more homogeneous, ranging from 11.3 ± 0.7 to 11.6 ± 0.7 kbar and from 887 ± 36 to 900 ± 37°C (Fig. 9A, Tab. 1).

Figure 9
P-T diagrams showing pressure and temperature conditions calculated by THERMOCALC software (average P-T) from Guaxupé Complex samples. (A) Sample TGL-13; (B) sample TGL-32; (C) sample TGL-58; (D) sample MAG-11. The continuous lines represent orthoclase-free calculations. The dashed lines represent the P-T calculations performed with orthoclase-bearing mineral assemblage. Metamorphic facies diagram modified from Spear (1993) and Harley (2016).

For garnet granulitic gneiss (sample TGL-32) without amphibole or biotite, the mineral assemblage used was sahlite + hypersthene + almandine + andesine + quartz ± orthoclase. In orthoclase-free calculations, pressure and temperature values range from 13.8 ± 1.5 to 14.7 ± 1.30 kbar and from 1,108 ± 121 to 1,199 ± 99ºC, with high correlations (Fig. 9B, Tab. 1). For potassium feldspar-bearing assemblages, the P-T results range from 12.7 ± 1.30 to 14.6 ± 1.60 kbar and from 988 ± 98 to 1,124 ± 114°C, with high correlations (Fig. 9B, Tab. 1).

In garnet granulitic gneiss with biotite, amphibole, and rutile (sample TGL-58), the mineral assemblage considered was sahlite + hypersthene + almandine + andesine + Mg-hastingsite + phlogopite + quartz ± orthoclase. Calculations in which orthoclase is not used indicate pressure and temperature values from 12.0 ± 0.90 to 12.7 ± 1.0 kbar and from 928 ± 28 to 979 ± 43°C, with correlations ranging from 0.47 to 0.63 (Fig. 9C, Tab.1). Considering potassium feldspar in the calculation, the average P-T is slightly lower and more homogeneous and ranges between 10.90 ± 1.0 to 11.40 ± 0.90 kbar and 906 ± 39 to 915 ± 41°C, with correlations in the order of 0.6 (Fig. 9C, Tab. 1).

For basic granulite with garnet (sample MAG-11), the mineral assemblage considered was sahlite + hypersthene + Mg-hastingsite + labradorite + almandine. Pressure and temperature values range from 12.8 ± 0.90 to 13.0 ± 0.8 kbar and from 929 ± 29 to 955 ± 27°C, with correlations of 0.35 (Fig. 9D, Tab. 1).

RCLC (thermobarometry corrected for retrograde exchange)

Garnet and orthopyroxene core compositions of garnet granulitic gneisses (samples TGL-13, TGL-32, and TGL-58) and basic granulite (sample MAG-11) were used to calculate pressure and temperature conditions using the RCLC program by Pattison et al. (2003). The program is based on Al-solubility in orthopyroxene in equilibrium with garnet, correcting effects of late Fe-Mg exchange. The results and the mineral assemblage used in the calculations are presented in Table 2 and Figure 10.

Figure 10
P-T diagram showing pressure and temperature conditions calculated by RCLC software from Guaxupé Complex samples. (A) Sample TGL-13; (B) sample TGL-32; (C) sample TGL-58; (D) sample MAG-11. Metamorphic facies diagram modified from Spear (1993) and Harley (2016).

Table 2
P-T results calculated using Pattison et al. (2003) (RCLC software).

Sample	Mineral Assemblage	XAl Opx	T (°C)	P (Kbar)
TGL-13	Grt8_14 Opx3_3 Pl4_6 Qtz	0.03	936	12.72
TGL-13	Grt6_13 Opx3_1 Pl4_1 Qtz	0.028	924	12.54
TGL-13	Grt10_5 Opx5_3 Pl7_1 Qtz	0.028	922	12.6
Average			927	12.62
Standard deviation			8	0.1
TGL-32	Grt8_8 Opx18 Pl14 Qtz	0.03	948	12.56
TGL-32	Grt1_17 Opx5 Pl15 Qtz	0.032	936	12.86
TGL-32	Grt4_13 Opx16 Pl8 Qtz	0.032	927	12.97
Average			937	12.80
Standard deviation			11	0.21
TGL-58	Grt11_4 Opx21 Pl4 Bt4 Qtz	0.035	1,079	14.97
TGL-58	Grt11_13 Opx25 Pl2 Bt3 Qtz	0.034	1,069	14.71
TGL-58	Grt8_3 Opx17 Pl1 Bt5 Qtz	0.035	1,085	14.83
Average			1,078	14.84
Standard deviation			8	0.13
MAG-11	Grt5_6 Opx19 Pl20	0.044	1,005	13.51
MAG-11	Grt5_7 Opx13 Pl18	0.039	967	12.63
MAG-11	Grt3_8 Opx14 Pl21	0.038	927	12.68
Average			966	12.94
Standard deviation			39	0.49

• T (°C) and P (Kbar): temperature and pressure estimated using et al (RCLC software), based on Al/2 mode; X_Al Opx: proportion of Al filling the octahedral site. The numbers subscribed to the minerals indicate the mineral chemical analysis point used in the geothermobarometric calculations (See Supplementary Tables).

Temperature and pressure estimates vary between each sample of garnet granulitic gneiss. For sample TGL-13, P-T conditions range from 922 to 936°C and from 12.54 to 12.72 kbar, with an average of 927 ± 8°C and 12.62 ± 0.10 kbar (Fig. 10A, Tab. 2). For sample TGL-32, temperature and pressure conditions range from 927 to 948°C and from 12.56 to 12.97 kbar, with an average of 937 ± 11°C and 12.81 ± 0.21 kbar (Fig. 10B, Tab. 2). For sample TGL-58, temperature ranges from 1,069 to 1,085°C and pressure between 14.71–14.97 kbar, with an average conditions of 1,078 ± 8°C and 14.84 ± 0.13 kbar (Fig. 10C, Tab. 2). The P-T conditions calculated for basic granulite (sample MAG-11) range from 927 to 1,005°C and from 12.63 to 13.51 kbar, with an average of 966 ± 39°C and 12.94 ± 0.49 kbar (Fig. 10D, Tab. 2).

Zr-in-rutile thermometry

Zr-in-rutile temperatures were calculated using the Tomkins et al. (2007) calibration. Only one garnet granulitic gneiss sample (sample TGL-58) has the appropriate buffering assemblage (zircon, quartz, and rutile) to apply this method. The pressure conditions were fixed in 14.0 kbar (obtained based on Al-solubility thermobarometry, by Pattison et al. 2003).

Zr concentrations in matrix rutile crystals range from 1,235 to 3,405 ppm and correspond to temperatures of 799 ± 6 to 919 ± 4°C at 14 kbar (Tab. 3, Fig. 11). Zr concentrations in rutile inclusions in garnet range from 2,470 to 7,078 ppm, and correspond to temperatures of 878 ± 4 to 1,024 ± 2°C at 14 kbar (Tab. 3, Fig. 11).

Figure 11
P-T diagram showing the minimum, average and maximum isopleths of Zr-in-rutile from sample TGL-58 using the calibration of Tomkins et al. (2007).

Table 3
Trace element composition (in ppm) of the analyzed rutile from cpx-grt granulitic gneiss with bt, amp, and rt (sample TGL-58).

Detection Limit (in ppm):		30	45	Tomkins et al. (2007)		Errors (2 σ)
Texture	Analysis	Si	Zr	P (Kbar)	T (°C)	T (°C)
matrix	rt_2	BD	1,235	14	799	± 6
inclusion	rt_3	293	2,500	14	880	± 4
matrix	rt_5	66	2,575	14	884	± 4
matrix	rt_6	179	2,765	14	893	± 4
inclusion	rt_7	103	2,797	14	894	± 4
inclusion	rt_9	83	2,881	14	898	± 4
inclusion	rt_10	49	3,324	14	916	± 4
inclusion	rt_11	84	3,409	14	920	± 4
matrix	rt_12	BD	3,352	14	917	± 4
matrix	rt_13	BD	2,744	14	892	± 4
inclusion	rt_14	70	3,109	14	907	± 4
matrix	rt_16	BD	2,654	14	887	± 4
inclusion	rt_17	130	4,072	14	943	± 4
inclusion	rt_18	122	7,078	14	1,024	± 2
matrix	rt_19	38	3,372	14	918	± 4
matrix	rt_21	70	3,100	14	907	± 4
matrix	rt_22	36	3,180	14	910	± 4
inclusion	rt_23	125	3,156	14	909	± 4
matrix	rt_25	35	3,226	14	912	± 4
matrix	rt_26	BD	1,945	14	850	± 4
matrix	rt_27	99	3,137	14	909	± 4
inclusion	rt_28	230	2,470	14	878	± 4
matrix	rt_29	BD	3,405	14	919	± 4
inclusion	rt_30	129	3,205	14	911	± 4
inclusion	rt_31	49	3,217	14	912	± 4
inclusion	rt_32	39	2,755	14	892	± 4

• P (Kbar): Pressure estimated based on RCLC calculations; T (°C): temperature calculated using et al calibration (α-quartz field); BD: below detection limit.

DISCUSSION

Metamorphism and P-T path

The pressure and temperature values obtained for the Basal Granulite Unit of the Guaxupé Complex northern portion indicate metamorphic peak around 1,078°C and 14.8 kbar, based on orthopyroxene Al-solubility in equilibrium with garnet in garnet granulitic gneiss (sample TGL-58 — grt + opx + cpx + rt). Calculations with the RCLC software show greater homogeneity in P-T values in comparison to THERMOCALC results, even though the calculated conditions for both are similar. In the case of sample TGL-32, with grt + cpx + opx + pl + qtz mineral assemblage, the temperature values above 1,150°C and with high standard deviation were interpreted as overestimated and unreliable.

The main metamorphic re-equilibration is recorded by P-T conditions of ca. 930 to 800°C and 13.5 to 11.0 kbar, marked mainly by the formation of amphibole and biotite in ortho-derived rocks. Considering orthoclase in geothermobarometric calculations in garnet granulitic gneisses, pressure and temperature conditions tend to be lower, suggesting that the potassium feldspar formation is associated with anatexis process by decompression, but still in the granulite facies (above orthoclase isograd).

Zirconium concentrations in rutile are highly dispersed, which is common under granulite and ultra-high temperature conditions (Luvizotto and Zack 2009, Jiao et al. 2011, Meyer et al. 2011, Kooijman et al. 2012, Taylor-Jones and Powell 2015, Harley 2016, Pape et al. 2016, Hart et al. 2018). Matrix rutile crystals show lower Zr concentrations (1,235 to 3,405 ppm) in comparison to rutile inclusions concentrations (2,470 to 7,078 ppm) in garnet.

Low Zr values in the matrix correspond to lower temperature conditions (799 to 918°C). Zr concentrations in rutile inclusions in garnet correspond to temperatures ranging from 878 to 1,024°C, which are lower than the metamorphic peak temperatures calculated by the RCLC and THERMOCALC softwares, but still in agreement with those of UHT metamorphism. The lower temperatures obtained in matrix crystals may occur due to the effect of post-peak metamorphic re-equilibration processes, such as decompression and cooling, which mobilize elements such as Zr, resulting in a variable retrograde adjustment of rutile Zr concentrations (Jiao et al. 2011, Hart et al. 2018). At UHT granulite-facies conditions, host minerals with low Zr-diffusivity (e.g., garnet or pyronexe) can shield rutile inclusions from re-equilibration during post-peak processes (Zack et al. 2004, Kooijman et al. 2012, Pauly et al. 2016), corresponding to temperatures closer to the metamorphic peak.

Garnet, biotite, and amphibole chemical characteristics corroborate with high-grade metamorphism conditions. Garnet composition is dominated by end-members almandine and pyrope. The compositional profiles are almost flat, with small variations toward the rims. In high-grade metamorphism, there often is a reduction of compositional zoning, representing the homogenization of the composition, followed by little modification during cooling, marked by the small variations toward the rims (Tracy et al. 1976, Woodsworth 1977, Yardley 1977, Spear 1993, Carlson and Schwarze 1997, Cooke et al. 2000). The high X_Mg, Al^IV, and Ti contents in biotite composition indicate typical characteristics of high metamorphic grade (Guidotti 1984), as well as the relatively high concentrations of Na_A, K_A, Al^IV, Al^VI, and Ti in amphibole composition, which also suggest higher grade conditions (Kostyuk and Sobolev 1969, Robinson et al. 1982, Deer et al. 1997a).

The higher pressure conditions obtained are at equilibrium in the sillimanite stability field and are in coherence with the mineralogical aspects and the geological setting. The mineral assemblage (grt + opx + cpx + rt) at equilibrium, the high pyrope concentrations in garnet, and the relatively high Al content in clinopyroxene and orthopyroxene in ortho-derived rocks (Deer et al. 1997c, Pattison et al. 2003) prove that these studied rocks experienced high pressures.

The pressure and temperature conditions calculated in this contribution (ca. 1,078°C and 14.8 kbar) are interpreted as close to the metamorphic peak in the basal portion of the Guaxupé Complex and are in agreement with ultra-high temperature metamorphic conditions. The P-T peak and re-equilibration conditions are congruent with the maximum and minimal temperatures and pressures previously calculated for the basal granulite unit of Guaxupé Complex (850°C and 8.5 kbar — Iyer et al. 1996; 900°C and 12.5 kbar — Campos Neto and Caby 1999; 1,040°C and 14.4 kbar — Del Lama et al. 2000; 890°C and 11 kbar — Garcia and Campos Neto 2003; 900°C and 10 kbar — Nascimento and Oliveira 2012; 900°C and 12 kbar — Rocha et al. 2018; 998 ± 23°C — Tedeschi et al. 2018).

Mineralogical, petrographic, chemical, and geothermobarometric data indicate metamorphic re-equilibration in the sillimanite stability field, mainly due to a decrease in pressure, followed by a slower decrease in temperature (near-isothermal decompression), following the kyanite-sillimanite stability limit line. These results suggest a clockwise P-T path (Fig. 12), as also proposed by Zanardo (1992), Iyer et al. (1996), Del Lama et al. (2000), Nascimento and Oliveira (2012), and Rocha et al. (2018).

Figure 12
P-T diagram showing pressure and temperature conditions calculated in this contribution and P-T path from samples of the basal portion of Guaxupé Complex. Metamorphic facies diagram modified from Spear (1993) and Harley (2016).

Tectono-metamorphic implications

The pressure and temperature conditions associated with the lithological, petrographic, and mineral chemistry data described in this contribution corroborate a regional framework of juxtaposed crustal blocks marked by a suture zone (Davino 1979, Almeida et al. 1980, Haralyi and Hasui 1982, Haralyi et al. 1985, Zanardo 1992, Malagutti Filho et al. 1996, Ebert and Hasui 1998, Dardenne 2000, Zanardo et al. 2006, Hasui 2010).

The geological setting of the region results from a Neoproterozoic continental collision and corresponds to the obduction of granulitic terranes represented by the Guaxupé Complex (Paranapanema Block) over an indentor (edge of the São Francisco Craton) (Brito Neves et al. 1999, 2014, Dardenne 2000, Alkmim et al. 2001, Cordani et al. 2003, Fuck et al. 2017, Valeriano 2017). The blocks’ boundaries are defined by wide gravimetric discontinuities (Bouguer anomalies involving type A subduction) (Davino 1979, Almeida et al. 1980, Haralyi and Hasui 1982, Haralyi et al. 1985, Malagutti Filho et al. 1996).

The results described in this contribution are in agreement with geological literature data and indicate that Guaxupé Complex terranes, represented by a lower crust segment, thrusted over the São Francisco Craton, initially, in a frontal ramp with direction close to NS to NW-SE. In the progression of the collision, the rotation of tensors responsible for the deformation takes place, leading the suture zone to develop lateral/oblique ramp features toward E-W and sinistral movement (Morales 1988, 1993, Zanardo 1992). The structural data are congruent with this setting, showing dominant foliation with NW to WNW direction tending to E-W and increasingly steep dips to the north direction of the unit. The mineral and stretching lineations exhibit NW direction and dip toward SE. Superposition or rotation of the lineation to E-W to ENE direction are described in the VSZ (Zanardo 1992, Morales 1993).

The pressure and temperature conditions interpreted as close to the metamorphic peak are related to the development stage of the frontal ramp (continental collision). The transpressional movement of the oblique/lateral ramp (VSZ) allowed the uplift of deepest portions of the lower crust in the northern Guaxupé Complex domain (Del Lama 1998, Del Lama et al. 2000, Zanardo et al. 2006). This segment is interpreted to record the higher pressure and temperature conditions of the granulitic terrane and agrees with the ultra-high temperature and high-pressure conditions obtained in this paper.

The progression of deformation resulted in the metamorphic re-equilibration under conditions around 930 to 800°C and 13.5 to 11.0 kbar in granulite facies in the sillimanite stability field. The results indicate faster decrease in pressure than in temperature, suggesting a near-isothermal decompression and a clockwise P-T path.

U-Pb zircon geochronological data indicate ages between 625 and 600 Ma for the syn-collisional metamorphism of the SGN (Mora et al. 2014, Vinagre et al. 2014, Rocha et al. 2018), consistent with ages between 630 and 600 Ma for the Southern Brasília Orogen collision (Basei et al. 1995, Janasi 1999, Campos Neto and Caby 2000, Vlach and Gualda 2000, Trouw et al. 2000, 2013, Campos Neto et al. 2004, 2011, Coelho et al. 2017, Tedeschi et al. 2018).

The geotectonic model and metamorphic trajectory suggested in this contribution are analogous to the large hot orogens model of Jamieson and Beaumont (2011, 2013) and Harley (2016). In this model, the deeper units compatible with ultra-high temperature conditions are lifted as nappes by ductile thrusting during syn-convergence thickening. The arrival of an indentor leads to upward ramping, forcing the expulsion of lower crustal segment rocks. Lower crustal rocks forced upward experiencing some decompression with cooling, and suggest a clockwise P-T path.

CONCLUSIONS

The pressure and temperature conditions calculated for the basal portion of the Guaxupé Complex indicate metamorphic peak around 1,078°C and 14.8 kbar, compatible with ultra-high temperature metamorphism, marked by mineral assemblages composed of grt + cpx + opx + pl ± qtz ± rt. This metamorphic stage was followed by re-equilibration in the sillimanite stability field of granulite facies at temperatures of 930 to 800°C and pressures of 13.5 to 11.0 kbar, following the boundary between the kyanite-sillimanite stability field.

Mineralogical, petrographic, mineral chemistry, and geotermobarometric data indicate that temperature and pressure conditions increase in NE direction of the Guaxupé Complex, close to the VSZ inflection to SE. The VSZ inflection (transpression segment) allowed the uplift of deeper portions of the granulitic sequence, recording higher pressure and temperature conditions.

The results presented in this contribution suggest a clockwise P-T path, typical of crustal thickening zones (continental collision), followed by near-isothermal decompression during tectonic exhumation.

• T.G.L. wrote the first draft of the manuscript, prepared Figures 4, 5, 6, 7, 8, 9, and 10, and prepared all tables; G.R.B.N. revised and improved the manuscript and prepared Figures 1, 2, 3, 11, and 12; A.Z: revised and improved the manuscript.

ACKNOWLEDGMENTS

T. G. Leme acknowledges Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil (CAPES) — Finance Code 001 — (MSc scholarship). The authors are grateful to Renata A. S. Paes for her participation and help in fieldwork. We would like to thank Professor Marcos Aurelio F. de Oliveira for his comments and discussions. We also thank the two anonymous reviewers for their constructive comments that benefited and improved this manuscript.

REFERENCES

• Alkmim F.F., Marshak S., Fonseca M.A. 2001. Assembling West Gondwana in the Neoproterozoic: clues from the São Francisco craton region, Brazil. Geology, 29(4):319-322. https://doi.org/10.1130/0091-7613(2001)029<0319:AWGITN>2.0.CO;2
  » https://doi.org/10.1130/0091-7613(2001)029<0319:AWGITN>2.0.CO;2
• Almeida F.F.M., Hasui Y., Davino A., Haralyi N.L.E. 1980. Informações geofísicas sobre o oeste mineiro e seu significado geotectônico. Anais da Academia Brasileira de Ciências, 52(1):49-60.
• Basei M.A.S., Siga Jr. O., Sato K., Sproesser W.M. 1995. A metodologia Urânio- Chumbo na USP. Princípios metodológicos, aplicações e resultados obtidos. Anais da Academia Brasileira de Ciências, 67(2):221-237.
• Brito Neves B.B., Campos Neto M.C., Fuck R.A. 1999. From Rodinia to Western Gondwana: an approach to the Brasiliano-Pan African Cycle and orogenic collage. Episodes, 22(3):155-166. https://doi.org/10.18814/epiiugs/1999/v22i3/002
  » https://doi.org/10.18814/epiiugs/1999/v22i3/002
• Brito Neves B.B., Fuck R.A., Pimentel M.M. 2014. The Brasiliano collage in South America: a review. Brazilian Journal of Geology, 44(3):493-518. http://dx.doi.org/10.5327/Z2317-4889201400030010
  » http://dx.doi.org/10.5327/Z2317-4889201400030010
• Brown M. 2007. Metamorphic conditions in orogenic belts: a record of secular change. International Geology Review, 49(3):193-234. https://doi.org/10.2747/0020-6814.49.3.193
  » https://doi.org/10.2747/0020-6814.49.3.193
• Campos Neto M.C., Basei M.A.S., Janasi V.A., Moraes R. 2011. Orogen migration and tectonic setting of the Andrelândia Nappe system: An Ediacaran western Gondwana collage, south of São Francisco craton. Journal of South American Earth Sciences, 32(4):393-406. https://doi.org/10.1016/j.jsames.2011.02.006
  » https://doi.org/10.1016/j.jsames.2011.02.006
• Campos Neto M.C., Basei M.A.S., Vlach S.R.F., Caby R., Szabó G.A.J., Vasconcelos P. 2004. Migração de Orógenos e Superposição de Orogêneses: Um Esboço da Colagem Brasiliana no Sul do Cráton do São Francisco, SE -Brasil. Geologia USP. Série Científica, 4(1):13-40. https://doi.org/10.5327/S1519-874x2004000100002
  » https://doi.org/10.5327/S1519-874x2004000100002
• Campos Neto M.C., Caby R. 1999. Neoproterozoic High-Pressure Metamorphism and Tectonic Constraint from the Nappe System South of the São Francisco Craton, Southeast Brazil. Precambrian Research, 97(1-2):3-26. https://doi.org/10.1016/S0301-9268(99)00010-8
  » https://doi.org/10.1016/S0301-9268(99)00010-8
• Campos Neto M.C., Caby R. 2000. Terrane Accretion and Upward Extrusion of High-Pressure Granulites in the Neoproterozoic Nappes of Southeast Brazil: Petrologic and Structural Constraints. Tectonics, 19(4):669-687. https://doi.org/10.1029/1999TC900065
  » https://doi.org/10.1029/1999TC900065
• Campos Neto M.C., Cioffi C.R., Moraes R., Motta R.G., Siga Jr. O., Basei M.A.S. 2010. Structural and metamorphic control on the exhumation of high-P granulites: The Carvalhos Klippe example, from the oriental Andrelândia Nappe System, Southern portion of the Brasília Orogen, Brazil. Precambrian Research, 180(3-4):125-142. https://doi.org/10.1016/j.precamres.2010.05.010
  » https://doi.org/10.1016/j.precamres.2010.05.010
• Campos Neto M.C., Figueiredo M.C.H. 1992. Orogênese Rio Doce. In: Congresso Brasileiro de Geologia, 37., 1992, São Paulo. Boletim de Resumos Expandidos, v. 1, p. 276-277.
• Carlson W., Schwarze E. 1997. Petrological significance of prograde homogenization of growth zoning in garnet: an example from the Llano Uplift. Journal of Metamorphic Geology, 15(5):631-644. https://doi.org/10.1111/j.1525-1314.1997.tb00640.x
  » https://doi.org/10.1111/j.1525-1314.1997.tb00640.x
• Cavalcante J.C., Cunha H.C., Chieregati L.A., Kaefer L.Q., Rocha J.M., Daitx E.C., Coutinho M.G.N., Yamamoto K., Drumond J.B.V., Rosa D.B., Ramalho R. 1979. Projeto Sapucaí - Estados de São Paulo e Minas Gerais: Relatório Final de Geologia. Brasília: Departamento Nacional da Produção Mineral, 299 p.
• Cioffi C.R., Campos Neto M.C., Möller A., Rocha B.C. 2016. Paleoproterozoic continental crust generation events at 2.15 and 2.08 Ga in the basement of the southern Brasília Orogen, SE Brazil. Precambrian Research, 275:176-196. https://doi.org/10.1016/j.precamres.2016.01.007
  » https://doi.org/10.1016/j.precamres.2016.01.007
• Coelho M.B., Trouw R.A.J., Ganade C.E., Vinagre R., Mendes J.C., Sato K. 2017. Constraining timing and PT conditions of continental collision and late overprinting in the Southern Brasília Orogen (SE-Brazil): U-Pb zircon ages and geothermobarometry of the Andrelândia Nappe System. Precambrian Research, 292:194-215. https://doi.org/10.1016/j.precamres.2017.02.001
  » https://doi.org/10.1016/j.precamres.2017.02.001
• Cooke R.A., O’Brien P.J., Carswell D.A. 2000. Garnet zoning and the identification of equilibrium mineral compositions in high-pressure-temperature granulites from the Moldanubian Zone, Austria. Journal of Metamorphic Geology, 18(5):551-569. https://doi.org/10.1046/j.1525-1314.2000.00273.x
  » https://doi.org/10.1046/j.1525-1314.2000.00273.x
• Cordani U.G., Brito Neves B.B., D’Agrella-Filho M.S. 2003. From Rodinia to Gondwana: a review of the available evidence from South America. Gondwana Research, 6(2):275-283. https://doi.org/10.1016/S1342-937X(05)70976-X
  » https://doi.org/10.1016/S1342-937X(05)70976-X
• Dardenne M.A. 2000. The Brasília Fold Belt. In: Cordani U.G., Milani E.J., Thomaz-Filho A., Campos D.A. (eds). Tectonic Evolution of South America. 31st International Geological Congress Rio de Janeiro, p. 231-263.
• Davino A. 1979. O baixo gravimétrico da região de Caldas Novas, GO. In: Simpósio Regional de Geologia, 2., 1979, Rio Claro. Atas.. v. 1, p. 87-100.
• Deer W.A., Howie R.A., Zussman J. 1992. An Introduction to the Rock-Forming Minerals 2^nd ed. London: Longman, 696 p.
• Deer W.A., Howie R.A., Zussman J. 1997a. Rock-forming minerals: Double-chain silicates. 2^nd ed. London: Geological Society Publishing House, 764 p. v. 2A.
• Deer W.A., Howie R.A., Zussman J. 1997b. Rock-forming minerals: Orthosilicates. 2^nd ed. London: Geological Society Publishing House, 918 p.
• Deer W.A., Howie R.A., Zussman J. 1997c. Rock-forming minerals: Single-chain silicates. 2 ed. London: Geological Society Publishing House, 668 p. v. 2A.
• Deer W.A., Howie R.A., Zussman J. 2004. Rock-forming minerals: Framework silicates: silica minerals, feldspathoids and the zeolites. London: Geological Society Publishing House, 982 p. v. 4B.
• Del Lama E.A. 1998. Terrenos granulíticos de Guaxupé: Evolução petrológica de um segmento da crosta inferior PhD Thesis, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista “Júlio de Mesquita Filho”, Rio Claro, 188 p.
• Del Lama E.A., Oliveira M.A.F., Zanardo A. 1994. Geotermobarometria em rochas do Complexo Campos Gerais ao norte da Zona de Cisalhamento Varginha. Revista Brasileira de Geociências, 24(4):1-7.
• Del Lama E.A., Zanardo A., Oliveira M.A.F., Morales N. 2000. Exhumation of high-pressure granulites of the Guaxupé Complex, southeastern Brazil. Geological Journal, 35(3-4):231-249. https://doi.org/10.1002/gj.859
  » https://doi.org/10.1002/gj.859
• Ebert H.D., Hasui Y. 1998. Transpressional tectonics and strain partitioning during oblique collision between three plates in the Precambrian of southeast Brazil. In: Holdsworth R.E., Strachan R.A., Dewey J.E. (eds.). Continental Transpressional and Transtensional Tectonics London: Geological Society, Special Publications, 135, p. 231-252. https://doi.org/10.1144/GSL.SP.1998.135.01.15
  » https://doi.org/10.1144/GSL.SP.1998.135.01.15
• Fonseca M.J.G., Silva Z.C.G., Campos D. de A., Tosatto P. 1979. Carta geológica do Brasil ao milionésimo: Folhas Rio de Janeiro, Vitória e Iguape. Texto explicativo. Brasília: MME/DNPM, 240 p.
• Fuck R.A., Pimentel M.M., Alvarenga C.J., Dantas E.L. 2017. The northern Brasília belt. In: Heilbron M., Cordani U.G., Alkmim, F.F. (eds). São Francisco Craton, Eastern Brazil - Tectonic Genealogy of a Miniature Continent, Regional Geology Reviews Berlin, Heidelberg: Springer, p. 205-220.
• Garcia M.G.M., Campos Neto M.C. 2003. Contrasting metamorphic conditions in the Neoproterozoic collision-related nappes south of Sao Francisco Craton, SE Brazil. Journal of South American Earth Sciences, 15(8):853-870. https://doi.org/10.1016/S0895-9811(02)00147-5
  » https://doi.org/10.1016/S0895-9811(02)00147-5
• Guidotti C.V. 1984. Micas in metamorphic rocks. In: Bailey S.W. (ed.). Micas. Reviews in Mineralogy and Geochemistry Washington, D.C.: Mineralogical Society of America, 13(1), p. 357-467.
• Haralyi N.L.E., Hasui Y. 1982. The gravimetric information and the archean-proterozoic structural framework of eastern Brazil. Revista Brasileira de Geociências, 12(1-3):160-166.
• Haralyi N.L.E., Hasui Y., Mioto J.A., Hanza V.M., Rodrigues C.R.V. 1985. Ensaio sobre a estruturação crustal do Estado de Minas Gerais com base na informação geofísica e geológica. In: Silva A.B., Rao A.B., Barbosa A.L.M., Dutra C.V., Rodrigues C.R.V., Ladeira E.A., Gierth E., Machado I.F., Buchi J., Sad J.H.G., Danni J.C.M., Mioto J.A., Érico J.C.D., Fuzikawa K., Baecker M.L., Haralyi N.L.E., Leonardos Jr. O.H., Mendonça Jr. T., Hamza V.M., Hasui Y. (Eds.). Contribuições à Geologia e à Petrologia Belo Horizonte: SBG, p. 71-93.
• Harley S.L. 1998. On the occurrence and characterization of ultrahigh-temperature crustal metamorphism. In: Treloar P.J., O’Brien P.J. (eds.). What drives metamorphism and metamorphic reactions? London: Geological Society, Special Publication, 138(1), p. 81-107. https://doi.org/10.1144/GSL.SP.1996.138.01.06
  » https://doi.org/10.1144/GSL.SP.1996.138.01.06
• Harley S.L. 2004. Extending our understanding of ultrahigh temperature crustal metamorphism. Journal of Mineralogical and Petrological Sciences, 99(4):140-158. https://doi.org/10.2465/jmps.99.140
  » https://doi.org/10.2465/jmps.99.140
• Harley S.L. 2008. Refining the P-T records of UHT crustal metamorphism. Journal of Metamorphic Geology, 26(2):125-154. https://doi.org/10.1111/j.1525-1314.2008.00765.x
  » https://doi.org/10.1111/j.1525-1314.2008.00765.x
• Harley S.L. 2016. A matter of time: the importance of the duration of UHT metamorphism. Journal of Mineralogical and Petrological Sciences, 111(2):50-72. https://doi.org/10.2465/jmps.160128
  » https://doi.org/10.2465/jmps.160128
• Hart E., Storey C., Harley S.L., Fowler M. 2018. A window into the lower crust: Trace element systematics and the occurrence of inclusions/intergrowths in granulite-facies rutile. Gondwana Research, 59:76-86. https://doi.org/10.1016/j.gr.2018.02.021
  » https://doi.org/10.1016/j.gr.2018.02.021
• Hasui Y. 2010. A grande colisão pré-cambriana do sudeste brasileiro e a estruturação regional. Geociências, 29(2):141-169.
• Heineck C.A., Vieira V.S., Drumond J.B.V., Leite C.A.L., Lacerda Filho V.J., Valente C.R., Souza J.D., Lopes R.C., Malouf R.F., Oliveira I.W.B., Oliveira C.C., Sachs L.L.B., Paes V.J.C., Junqueira Pa. A. 2004. Folha SE.23 - Belo Horizonte. In: Schobbenhaus C., Gonçalves J.H., Santos J.O.S., Abram M.B., Leão Neto R., Matos G.M.M., Vidotti R.M., Ramos M.A.B., Jesus J.D.A. de (eds.). Carta Geológica do Brasil ao Milionésimo, Sistema de Informações Geográficas Programa Geologia do Brasil. Brasília: CPRM. CD-ROM.
• Holland T.J.B., Powell R. 2000. AX: A program to calculate activities of mineral end members from chemical analyses (usually determined by electron microprobe). Available at: <http://www.ccp14.ac.uk/ccp/web-mirrors/crush/astaff/holland/ax.html>. Accessed on: Mar. 19, 2019.
  » http://www.ccp14.ac.uk/ccp/web-mirrors/crush/astaff/holland/ax.html
• Iyer S.S., Choudhuri A., Pattison D.R.M., De Paoli G.R. 1996. Petrology and geochemistry of the Neoproterozoic Guaxupé granulite facies terrain, southeastern Brazil. Precambrian Research, 77(1-2):23-40. https://doi.org/10.1016/0301-9268(95)00043-7
  » https://doi.org/10.1016/0301-9268(95)00043-7
• Jamieson R.A., Beaumont C. 2011. Coeval thrusting and extension during lower crustal ductile flow–implications for exhumation of high‐grade metamorphic rocks. Journal of Metamorphic Geology, 29(1):33-51. https://doi.org/10.1111/j.1525-1314.2010.00908.x
  » https://doi.org/10.1111/j.1525-1314.2010.00908.x
• Jamieson R.A., Beaumont C. 2013. On the origin of orogens. Geological Society of America Bulletin, 125(11-12):1671-1702. https://doi.org/10.1130/B30855.1
  » https://doi.org/10.1130/B30855.1
• Janasi V.A. 1999. Petrogênese de granitos crustais na Nappe de Empurrão Socorro Guaxupé (SP-MG): uma contribuição da geoquímica elemental e isotópica PhD Thesis, Instituto de Geociências, Universidade de São Paulo, 248 p.
• Jiao S., Guo J., Mao Q., Zhao R. 2011. Application of Zr-in-rutile thermometry: a case study from ultrahigh-temperature granulites of the Khondalite belt, North China Craton. Contributions to Mineralogy and Petrology, 162(2):379-393. https://doi.org/10.1007/s00410-010-0602-3
  » https://doi.org/10.1007/s00410-010-0602-3
• Kelsey D.E. 2008. On ultrahigh-temperature crustal metamorphism. Gondwana Research, 13(1):1-29. https://doi.org/10.1016/j.gr.2007.06.001
  » https://doi.org/10.1016/j.gr.2007.06.001
• Kelsey D.E., Hand M. 2015. On ultrahigh temperature crustal metamorphism: phase equilibria, trace element thermometry, bulk composition, heat sources, timescales and tectonic settings. Geoscience Frontiers, 6(3):311-356. https://doi.org/10.1016/j.gsf.2014.09.006
  » https://doi.org/10.1016/j.gsf.2014.09.006
• Kooijman E., Smit M.A., Mezger K., Berndt J. 2012. Trace element systematics in granulite facies rutile: implication for Zr geothermometry and provenance studies. Journal of Metamorphic Geology, 30(4):397-412. https://doi.org/10.1111/j.1525-1314.2012.00972.x
  » https://doi.org/10.1111/j.1525-1314.2012.00972.x
• Kostyuk E.A., Sobolev V.S. 1969. Paragenetic types of calciferous amphiboles of metamorphic rocks. Lithos, 2(1):67-81. https://doi.org/10.1016/S0024-4937(69)80006-X
  » https://doi.org/10.1016/S0024-4937(69)80006-X
• Lacerda Filho J.V., Valente C.R., Bahia R.B.C., Lopes R.C., Romanini S.J., Oliveira I.W.B., Oliveira C.C., Sachs L.L.B., Silva V.A., Batista I.H. 2004. Folha SD.22 - Goiás. In: Schobbenhaus C., Gonçalves J.H., Santos J.O.S., Abram M.B., Leão Neto R., Matos G.M.M., Vidotti R.M., Ramos M.A.B., Jesus J.D.A. de (eds.). Carta Geológica do Brasil ao Milionésimo, Sistema de Informações Geográficas Programa Geologia do Brasil. Brasília: CPRM. CD-ROM.
• Leake B.E., Woolley A.R., Arps C.E.S., Birch W., Gilbert M.C., Hawthorne F.C., Grice J.D., Kato A., Kisch H., Krivovichev V., Linthout K., Laird J., Mandarino J.A., Maresch W., Nickel E., Rock N.M.S., Schumacher J.C., Smith D.C., Stephenson N.C.N, Ungaretti E.J.W., Youzhi G. 1997. Nomenclature of amphiboles: report of the subcommittee on amphiboles of the international mineralogical association, commission on new minerals and mineral names. The Canadian Mineralogist, 35(1):219-246.
• Leite C.A.S., Perrotta M.M., Silva L.C., Silva M.A., Heineck C.A., Salvador E.D., Vieira V.S., Lopes R.C., Silva M.G.M., Drumond J B.V., Malouf R.F., Lacerda Filho J.V., Valente C.R., Gomes S.D., Sachs L.L.B., Oliveira I.W.B., Ramgrab G.E., Netto C., Junqueira P.A., Paes V.J. C. 2004. Folha SE.23 - Rio de Janeiro. In: Schobbenhaus C., Gonçalves J.H., Santos J.O.S., Abram M.B., Leão Neto R., Matos G.M.M., Vidotti R.M., Ramos M.A.B., Jesus J.D.A. de (eds.). Carta Geológica do Brasil ao Milionésimo Programa Geologia do Brasil. Brasília: CPRM. CD-ROM.
• Leme T.G. 2019. Geotermobarometria das rochas do Grupo Araxá e do Complexo Guaxupé na região de Guaxupé – Nova Resende, MG Ms Dissertation, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista “Júlio de Mesquita Filho”, Rio Claro, 175 p.
• Leme T.G., Navarro G.R.B., Zanardo A., Montibeller C.C. 2019. Petrografia, química mineral e geotermobarometria de retroeclogito no Grupo Araxá na região da Zona de Cisalhamento Varginha, sudoeste de Minas Gerais. Geociências, 38(2):297-313.
• Luvizotto G.L., Zack T. 2009. Nb and Zr behaviour in rutile during high-grade metamorphism and retrogression: an example from the Ivrea-Verbano Zone. Chemical Geology, 261(3-4):303-317. https://doi.org/10.1016/j.chemgeo.2008.07.023
  » https://doi.org/10.1016/j.chemgeo.2008.07.023
• Luvizotto G.L., Zack T., Triebold S., Von Eynatten H. 2009. Rutile occurrence and trace element behavior in medium-grade metasedimentary rocks: Example from the Erzgebirge, Germany. Mineralogy and Petrology, 97(3-4):233-249. https://doi.org/10.1007/s00710-009-0092-z
  » https://doi.org/10.1007/s00710-009-0092-z
• Malagutti Filho W., Ebert H.D., Hasui Y., Haralyi N.L.E., Sturaro J.R. 1996. Gravimetria e compartimentação crustal do sul de Minas Gerais. Geociências, 15(1):199-217.
• Mantovani M.S.M., Brito Neves B.B. 2005. The Paranapanema Lithospheric Block: Its Importance for Proterozoic (Rodinia, Gondwana) Supercontinent Theories. Gondwana Research, 8(3):303-315. https://doi.org/10.1016/S1342-937X(05)71137-0
  » https://doi.org/10.1016/S1342-937X(05)71137-0
• Mantovani M.S.M., Brito Neves B.B. 2009. The Paranapanema Lithospheric Block: its nature and role in the Accretion of Gondwana. In: Gaucher C., Sial A., Halverson G., Frimmel H. (eds.). Neoproterozoic-Cambrian Tectonics, Global Change and Evolution: A Focus on South Western Gondwana. Amsterdam: Elsevier, p. 257-272.
• Meyer M., John T., Brandt S., Klemd R. 2011. Trace element composition of rutile and the application of Zr-in-rutile thermometry to UHT metamorphism (Epupa Complex, NW Namibia). Lithos, 126(3-4):388-401. https://doi.org/10.1016/j.lithos.2011.07.013
  » https://doi.org/10.1016/j.lithos.2011.07.013
• Mora C.A.S., Campos Neto M.C., Basei M.A.S. 2014. Syn-collisional lower continental crust anatexis in the Neoproterozoic Socorro-Guaxupé Nappe System, southern Brasília Orogen, Brazil: Constraints from zircon U–Pb dating, Sr–Nd–Hf signatures and whole-rock geochemistry. Precambrian Research, 255(3):847-864. https://doi.org/10.1016/j.precamres.2014.10.017
  » https://doi.org/10.1016/j.precamres.2014.10.017
• Moraes R., Nicollet C., Barbosa J.S.F., Fuck R.A., Sampaio A.R. 2015. Applications and limitations of thermobarometry in migmatites and granulites using as an example rocks of the Araçuaí Orogen in southern Bahia, including a discussion on the tectonic meaning of the current results. Brazilian Journal of Geology, 45(4):517-539. https://doi.org/10.1590/2317-4889201520150026
  » https://doi.org/10.1590/2317-4889201520150026
• Morales N. 1988. Evolução lito-estrutural das rochas pré-cambrianas da região de São João da Boa Vista Ms Dissertation, Intituto de Geociências, Universidade de São Paulo, São Paulo, 157 p.
• Morales N. 1993. Evolução tectônica do cinturão de cisalhamento Campo do Meio na sua porção ocidental. PhD Thesis, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista “Júlio de Mesquita Filho”, Rio Claro, 2 v.
• Nascimento M.B. 2010. Evolução metamórfica PTt da porção norte do Complexo Guaxupé na região de Arceburgo-Santa Cruz da Prata, MG PhD Thesis, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista “Júlio de Mesquita Filho”, Rio Claro, 141 p.
• Nascimento M.B., Oliveira M.A.F. 2012. Geotermobarometria de Granulitos Associados à Supracrustais na Porção Norte do Complexo Guaxupé-Região de Arceburgo-Santa Cruz do Prata, MG. Geociências, 31(2):207-228.
• Oliveira M.A.F., Negri F.D.A., Zanardo A., Morales N. 2019. Archean and paleoproterozoic crust generation events, Amparo complex and Serra Negra orthogneiss in southern Brasília Orogen, SE Brazil. Journal of South American Earth Sciences, 90:137-154. https://doi.org/10.1016/j.jsames.2018.11.029
  » https://doi.org/10.1016/j.jsames.2018.11.029
• Pape J., Mezger K., Robyr M. 2016. A systematic evaluation of the Zr-in-rutile thermometer in ultra-high temperature (UHT) rocks. Contributions to Mineralogy and Petrology, 171(5):1-20. https://doi.org/10.1007/s00410-016-1254-8
  » https://doi.org/10.1007/s00410-016-1254-8
• Pattison D.R.M., Chacko T., Farquhar J., McFarlane C.R.M. 2003. Temperatures of granulite-facies metamorphism: constraints from experimental phase equilibria and thermobarometry corrected for retrograde exchange. Journal of Petrology, 44(5):867-900. https://doi.org/10.1093/petrology/44.5.867
  » https://doi.org/10.1093/petrology/44.5.867
• Pauly J., Marschall H.R., Meyer H.P., Chatterjee N., Monteleone B. 2016. Prolonged Ediacaran–Cambrian metamorphic history and short-lived high-pressure granulite facies metamorphism in the H.U. Sverdrupfjella, Dronning Maud Land (East Antarctica): evidence for continental collision during Gondwana assembly. Journal of Petrology, 57(1):185-228. https://doi.org/10.1093/petrology/egw005
  » https://doi.org/10.1093/petrology/egw005
• Powell R., Holland T.J.B. 1994. Optimal geothermometry and geobarometry. American Mineralogist, 79(1-2):120-133.
• Richard L.R. 1995. Mineralogical and Petrological Data Processing System MINPET for Windows. Version 2.02. Québec: MinPet Geological Software.
• Robinson P., Spear F.S., Schumacher J.C., Laird J., Klein C., Evans B.W., Doolan B.L. 1982. Phase relations of metamorphic amphiboles: Natural occurrence and theory. In: Veblen D.R., Ribbe P.H. (eds). Amphiboles: Petrology and Experimental Phase Relations. Reviews in Mineralogy and Geochemistry Washington, D.C., Mineralogical Society of America, p. 1-227.
• Rocha B.C., Moraes R., Möller A., Cioffi C.R. 2018. Magmatic inheritance vs. UHT metamorphism: Zircon petrochronology of granulites and petrogenesis of charnockitic leucosomes of the Socorro–Guaxupé nappe, SE Brazil. Lithos, 314-315:16-39. https://doi.org/10.1016/j.lithos.2018.05.014
  » https://doi.org/10.1016/j.lithos.2018.05.014
• Rocha B.C., Moraes R., Möller A., Cioffi C.R., Jercinovic M.J. 2017. Timing of anatexis and melt crystallization in the Socorro–Guaxupé Nappe, SE Brazil: Insights from trace element composition of zircon, monazite and garnet coupled to U–Pb geochronology. Lithos, 277:337-355. https://doi.org/10.1016/j.lithos.2016.05.020
  » https://doi.org/10.1016/j.lithos.2016.05.020
• Souza J.D., Kosin M., Heineck C.A., Lacerda Filho J.V., Teixeira L.R., Valente C.R., Guimarães J.T., Bento R.V., Borges V.P., Santos R.A., Leite C.A., Neves J.P., Oliveira I.W.B., Carvalho L.M., Pereira L.H.M., Paes V.J.C. 2004. Folha SD.23 - Brasília. In: Schobbenhaus C., Gonçalves J.H., Santos J.O.S., Abram M.B., Leão Neto R., Matos G.M.M., Vidotti R.M., Ramos M.A.B., Jesus J.D.A. de (eds.). Carta Geológica do Brasil ao Milionésimo Programa Geologia do Brasil. Brasília: CPRM. CD-ROM.
• Spear F.S. 1993. Metamorphic phase equilibria and pressure-temperature-time paths Washington, D.C., Mineralogical Society of America, 789 p.
• Taylor-Jones K., Powell R. 2015. Interpreting zirconium-in-rutile thermometric results. Journal of Metamorphic Geology, 33(2):115-122. https://doi.org/10.1111/jmg.12109
  » https://doi.org/10.1111/jmg.12109
• Tedeschi M.F., Novo T., Azevedo R., Amaral L.F.S., Degler R., Viera P.L.N.C.R. 2015. Geologia das Folha Caldas (SF.23-V-D-IV) e Poços de Caldas (SF.23-V-C-VI) 1:100.000 Projeto Fronteiras de Minas. Belo Horizonte: CODEMIG-UFMG.
• Tedeschi M.F., Pedrosa-Soares A., Dussin I., Lanari P., Novo T., Pinheiro M.A.P., Lana C., Peters C. 2018. Protracted zircon geochronological record of UHT garnet-free granulites in the Southern Brasília orogen (SE Brazil): Petrochronological constraints on magmatism and metamorphism. Precambrian Research, 316:103-126. https://doi.org/10.1016/j.precamres.2018.07.023
  » https://doi.org/10.1016/j.precamres.2018.07.023
• Tomkins H.S., Powell R., Ellis D.J. 2007. The pressure dependence of the zirconium-in-rutile thermometer. Journal of Metamorphic Geology, 25(6):703-713. https://doi.org/10.1111/j.1525-1314.2007.00724.x
  » https://doi.org/10.1111/j.1525-1314.2007.00724.x
• Tracy R.J., Robinson P., Thompson A.B. 1976. Garnet composition and zoning in the determination of temperature and pressure of metamorphism, central Massachusetts. American Mineralogist, 61(7-8):762-775.
• Trouw R.A.J., Heilbron M., Ribeiro A., Paciullo F.V.P., Valeriano C.M., Almeida J.C.H., Tupinambá M., Andreis R.R. 2000. The central segment of Ribeira Belt. In: Cordani U.G., Milani E.J., Thomaz-Filho A., Campos D.A. (eds.). Tectonic Evolution of South America. 31st International Geological Congress Rio de Janeiro, p. 287-310.
• Trouw R.A.J., Peternel R., Ribeiro A., Heilbron M., Vinagre R., Duffles, P., Trouw C.C., Fontainha M., Kussama H.H. 2013. A new interpretation for the interference zone between the southern Brasília belt and the central Ribeira belt, SE Brazil. Journal of South American Earth Sciences, 48:43-57. http://dx.doi.org/10.1016/j.jsames.2013.07.012
  » http://dx.doi.org/10.1016/j.jsames.2013.07.012
• Valente C.R., Lacerda Filho J.F., Rizzotto G.J., Lopes R.C., Romanini S.J., Oliveira I.W.B., Sachs L.L.B., Silva V.A., Batista I.H. 2004. Folha SE.22 - Goiânia. In: Schobbenhaus C., Gonçalves J.H., Santos J.O.S., Abram M.B., Leão Neto R., Matos G.M.M., Vidotti R.M., Ramos M.A.B., Jesus J.D.A. de (eds.). Carta Geológica do Brasil ao Milionésimo Programa Geologia do Brasil. Brasília: CPRM. CD-ROM.
• Valeriano C.M. 2017. The Southern Brasília Belt. In: Helibron M., Cordani U.G., Alkmim F.F. (eds.). São Francisco Craton, Eastern Brazil – Tectonic Genealogy of a Miniature Continent. Regional Geology Reviews Berlin/Heidelberg: Springer, p. 189-203.
• Valeriano C.M., Dardenne M.A., Fonseca M.A., Simões L.S.A., Seer H.J. 2004. A evolução tectônica da Faixa Brasília. In: Mantesso-Neto V., Bartorelli A., Carneiro C.D.R., Brito Neves B.B. (eds). Geologia do Continente Sul-Americano: evolução da obra de Fernando Flávio Marques de Almeida. São Paulo: Beca, p. 575-592.
• Valeriano C.M., Pimentel M.M., Heilbron M., Almeida J.C.H., Trouw R.A.J. 2008. Tectonic evolution of the Brasília Belt, Central Brazil, and early assembly of Gondwana. In: Pankhurst R.J., Trouw R.A.J., Brito Neves B.B., De Wit M.J. (eds.). West Gondwana: Pre-Cenozoic Correlations Across the South Atlantic Region. London: Geological Society, Special Publications, 294(1), p. 197-210. https://doi.org/10.1144/SP294.11
  » https://doi.org/10.1144/SP294.11
• Vinagre R., Trouw R.A., Mendes J.C., Duffles P., Peternel R., Matos G. 2014. New evidence of a magmatic arc in the southern Brasilia Belt, Brazil: the Serra da Agua Limpa batholith (Socorro-Guaxupé Nappe). Journal of South American Earth Sciences, 54:120-139. https://doi.org/10.1016/j.jsames.2014.05.002
  » https://doi.org/10.1016/j.jsames.2014.05.002
• Vlach S.R., Gualda, G.A.R. 2000. Microprobe monazite dating and the ages of some granitic and metamorphic rocks from southeastern Brazil. Revista Brasileira de Geociências, 30(1):214-218.
• Whitney D.L., Evans B.W. 2010. Abbreviations for names of rock-forming minerals. American Mineralogist, 95(1):185-187. https://doi.org/10.2138/am.2010.3371
  » https://doi.org/10.2138/am.2010.3371
• Woodsworth G.J. 1977. Homogenization of zoned garnets from pelitic schists. The Canadian Mineralogist, 15(2):230-242.
• Yardley B.W.D. 1977. An empirical study of diffusion in garnet. American Mineralogist, 62(7-8):793-800.
• Zack T., Moraes R., Kronz A. 2004. Temperature dependence of Zr in rutile: Empirical calibration of a rutile thermometer. Contributions to Mineralogy and Petrology, 148(4):471-488. http://dx.doi.org/10.1007/s00410-004-0617-8
  » http://dx.doi.org/10.1007/s00410-004-0617-8
• Zanardo A. 1992. Análise petrográfica, estratigráfica e microestrutural da região de Guaxupé-Passos-Delfinópolis (MG) PhD Thesis, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista “Júlio de Mesquita Filho”, Rio Claro, 288 p.
• Zanardo A. 2003. Pesquisa Geológica e de matérias primas cerâmicas do centro nordeste do Estado de São Paulo e vizinhanças – Sistematização crítica da produção Técnico - Científica PhD Thesis, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista “Júlio de Mesquita Filho”, Rio Claro, 304 p.
• Zanardo A., Morales N., Oliveira M.A.F., Del Lama E.A. 2006. Tectono-Lithologic associations of the Alterosa Paleo Suture Zone – Southeastern Brazil. Revista UnG - Geociências, 5(1):103-117.

Supplementary data

Supplementary data associated with this article can be found in the online version: Supplementary Table.

Publication Dates

• Publication in this collection
  06 Nov 2020
• Date of issue
  2020

History

• Received
  28 Jan 2020
• Accepted
  30 July 2020