Navegando por Assunto "Granitoides"

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Petrogênese da Suíte Igarapé Gelado: implicações para o magmatismo neoarqueano da Província Carajás, Cráton Amazônico
(Universidade Federal do Pará, 2025-04-30) MESQUITA, Caio José Soares; DALL’ AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
The Igarapé Gelado suite (IGS) is located near the northern border of the Carajás Province, almost at its boundary with the Bacajá Domain, along the Cinzento lineament, and is intrusive in metavolcanic mafic rocks and banded iron formations. The central-eastern portion of the IGS comprises four rock varieties: tonalite to granodiorite with varying contents of biotite and amphibole, (1) with associated clinopyroxene and/or orthopyroxene (PBHTnGd) or (2) devoid of pyroxenes (BHTnGd); and monzogranites that exhibit variable biotite and amphibole content and can be (3) moderately (BHMzG) or (4) strongly (RBHMzG) reduced. The PBHTnGd shows ferrosilite and/or augite with subordinate hedenbergite. The amphiboles are K-hastingsite and, subordinately, Fe-Tschermakite in monzogranites. Biotites are ferroan, and in reduced granites show #Fe > 0.90. These micas are similar to those of alkaline to subalkaline rocks and compositionally akin of primary magmatic biotites. Plagioclase is oligoclase. The integration of thermineral chemistry;mobarometry results and thermodynamic modeling and their comparison with the paragenesis present in natural rocks improved the estimation of crystallization parameters (T, P, ƒO2, H2O), and allowed a better interpretation of magmatic evolution. The IGS granites crystallized at pressures of 550 ± 100 MPa, higher than those attributed to other Neoarchean granites in Carajás provinve. The estimated liquidus temperature for the IGS pyroxene variety is ~1000±50°C. BHTnGd and BHMzG formed within a similar temperature range to PBHTnGd, while RBHMzG had lower liquidus temperatures (≤900°C). Solidus temperatures of around ~660 °C were estimated for the four IGS varieties. The BHMzG magma evolved under conditions of low ƒO2, slightly above or below the FMQ buffer (FMQ±0.5), like those of the Planalto suite and the reduced granites of the Vila Jussara and Vila União suites of Carajás province. In the magmas of the PBHTnGd and BHTnGd varieties the oxygen fugacity attained FMQ+0.5. The RBHMzG crystallized under strongly reduced conditions equivalent to FMQ-0.5 to FMQ-1. The magmas of the monzogranitic varieties evolved with a H2O content of ≥4 wt%, attaining 7 wt% in the case of the reduced monzogranites. This is comparable to, or slightly exceeding, the levels typically attributed to the Neoarchean granites of Carajás province (≥ 4% wt%). In contrast, the variety with pyroxene has a water content (~4 wt%) like that of Café enderbite and Rio Seco charnockite from Carajás province, and Matok Pluton from Limpopo belt. Based on the chemical composition, the rocks from IGS are ferroan, reduced to oxidized A-type-like granites, akin to other Neoarchean granite suites from the Carajás province. The IGS are younger than the 2.76-2.73 Ga Neoarchean granites from the Carajás province. A crystallization concordia age of ~2.68 Ga was obtained by U-Pb SHRIMP in zircon for the RBHMzG variety, and similar upper intercept ages were furnished by the other IGS varieties, except for ages of ~2.5 Ga that resemble the ages of the IOCG Salobo deposits associated with reactivation of the Cinzento Lineament. Tmineral chemistry;he deformation of the IGS rocks was influenced by shear zones linked to that lineament, forming elongated bodies with varied foliation. These zones facilitated the migration and deformation of magmas from the final crystallization stages until their complete cooling, characterizing a syntectonic process. This syntectonicity is associated with the inversion of the Carajás Basin, and the younger crystallization age of these rocks indicates that the inversion occurred up to 2.68 Ga, extending the previously estimated interval (2.76– 2.73 Ga). The IGS displays negative to slightly positive values of εNd(t)(-2.86 to 0.18) and εHf(t)(-3.3 to 0.1), and Paleoarchean to Mesoarchean TDM ages [Nd-TDM(2.98-2.84) and Hf-TDM C (3.27-3.12)]. The positive values of εNd(t) and εHf(t) for the RBHMzG variety, suggest possible juvenile contribution or contamination in the source of its magma. The IGS rocks come from the melting of 19% (PBHTnGd) or 14% (BHTnGd) of contaminated mafic granulite, - and from melting of 9% (BHMzG) and 7% (RBHMzG) of a tholeiitic mafic granulite. The area of occurrence of the IGS is marked by hydrothermalism and mineralizations that locally modified the composition of rocks and minerals, allowing the leaching of REE and Y that changed the composition of some samples of BHMzG approaching them of (false) A1- subtype granites. In addition, these processes were responsible for zircon alteration, which resulted in grains showing enrichment of U, Th, and LREE, and massive textures, that furnished upper intercept U-Pb ages, contrarily to the zircon crystals of the RBHMzG variety that preserved primary characteristics and presented Concordia ages.
Acesso aberto (Open Access)
Petrografia e evolução crustal da porção sul do Domínio Pacajá, Cráton Amazônico: evolução policíclica do Mesoarqueano ao Riaciano
(Universidade Federal do Pará, 2025-08-13) NERI, Arthur Santos da Silva; DALL’ AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
The integration of field, petrographic, mineralogical, geochemical, geochronological (U-Pb in zircon, monazite, and titanite), and isotopic data (Sm-Nd in whole rock and Lu-Hf in zircon) undertaken in the southern portion of the Bacajá Domain enabled the identification and characterization of new granitoid and charnockitic units previously encompassed within the Cajazeiras Complex. These discoveries allowed a redefinition of the regional stratigraphy and advancing the understanding of the crystallization conditions, origin, and evolution of magmatic and metamorphic orthoderived rocks. A long-lived Rhyacian magmatic event (~70 Ma) was recognized, beginning around 2.12 Ga and lasting until 2.05 Ga. During this interval, the following units were identified: Bandeirante (2.12 Ga, εHf(t) = -6.5 to -4.6, εNd(t) = -3.40); and Alto Rio Preto (2.10-2.06 Ga, εHf(t) = -10.2 to -6.3, εNd(t) = -8.96 -2.80) granites; Maravilha (2.09 Ga, εHf(t) = - 9.2 to -8.2, εNd(t) = -3.01 to -1.91) and Serra Azul (2.07 Ga, εHf(t) = -8.8 to -5.8, εNd(t) = -6.44 to -4.71) charnockites; Bernardino granite (2.05 Ga, εNd(t) = -6.71). Geochemically, the units are mostly high-K calc-alkaline and magnesian (Alto Rio Preto and Bernardino granites, Serra Azul charnockite), transitioning to calcic or alkali-calcic and ferroan (Bandeirante granite and Maravilha charnockite, respectively). They range from metaluminous to weakly peraluminous, except the Bernardino granite, which is strongly peraluminous. The Nd-Hf isotopic integration indicates a crustal source with strongly negative epsilon values and Archean model ages, with a marked contrast to crystallization ages, pointing to long crustal residence times. These granitoids were generated by the collision between the Bacajá and Carajás domains in a late- to post-collisional setting during the Transamazonian Orogeny. Crustal thickening and subsequent delamination are interpreted as the main mechanisms responsible for partial melting and generation of these magmas. The Nd-Hf isotopic signatures reveal a coherent crustal compartmentalization between the Bacajá, Carecuru and Lourenço (Amazonian Craton) and Bauolé-Mossi domains (West Africa Craton), suggesting that these segments were juxtaposed during the amalgamation of the Columbia supercontinent. The Alto Rio Preto granite is composed of epidote-bearing granites and granodiorites-tonalites. This granite was emplaced at pressures of 0.4-0.7 GPa and temperatures between 949 and ~640 ºC, evolved under oxidizing conditions (NNO±0.5 to ±1), with initial water contents of ~2-6 wt%. The preservation of magmatic epidote results of a complex interaction between generation and emplacement pressures, oxidizing conditions and water content in the magma, combined with low density and viscosity that facilitated rapid magma ascent (4-5 km/year) through the crust, preventing complete epidote dissolution. Field and petrographic data suggest that this granite represents a syntectonic intrusion, with geochemical affinities with high-K calc-alkaline series. The parental magma of the monzogranitic facies was derived from dehydration melting of a basaltic source at 0.99 GPa and 865 °C leaving an amphibolite residuum. These granitoids represent an example of crustal reworking of lower mafic crust and do not contribute to net crustal growth in the collisional zone between the Bacajá and Carajás domains. The Maravilha charnockite comprises two petrographic associations: (i) monzonite-granite-charnockite and (ii) granodiorite-monzogranite, with or without igneous orthopyroxene and fayalite + quartz. The (i) association crystallized at temperatures between 1052 and ~680 °C, and evolved under reducing (FMQ±0.5), with ≤3 wt% initial water contents. The (ii) crystallized at temperatures between 918 and ~680 °C and evolved under oxidizing conditions (NNO±0.5), with ~4 wt% initial water contents. Both associations were emplaced at pressures between 0.3 and 0.6 GPa The Serra Azul charnockite consists of tonalites, granodiorites, and rare granites, with or without igneous orthopyroxene. These rocks were emplaced at pressures 0.3-0.6 GPa, temperatures between 1078 and ~700 ºC, and evolved under oxidizing conditions (NNO±0.7 to ±2), with initial water contents ~ 2-3 wt%. Thermodynamic data indicate that fayalite is restricted to low pressures (≤0.3 GPa) and reduced conditions (FMQ -2 to -0.6), but it can crystallize under water-rich conditions (2.3 to 6.2 wt%, possibly up to 9 wt%). In contrast, orthopyroxene can crystallize over a wide pressures range (0.1-1 GPa), from reduced to oxidizing conditions (FMQ-2 to NNO+2.5), and under moderate water contents (~5.2 to 6.5 wt%). The Cajazeiras Complex comprises tonalitic to monzogranitic orthogneisses crystallized at 2.97-2.94 Ga, followed by Pb-loss/metamorphism at 2.80–2.81 Ga and Paleoproterozoic metamorphism 2.21-2.01 Ga. These rocks show geochemical affinities with sanukitoid s.l., representing the oldest sanukitoid magmatism in the Amazonian Craton and the second oldest worldwide. The Nd-Hf data (εNd(t) +0.65; εHf(t) +0.5 to +2.5) suggest a juvenile contribution and short crustal residence time, with model ages close to the crystallization age. The discovery of these rocks implies that the mantle was already metasomatized in the Mesoarchean and opens possibilities for the presence of other typical Archean rocks in the basement of the domain. These orthogneisses were metamorphosed under upper amphibolite to granulite facies. The metamorphic peak was marked by the assemblage clinopyroxene-amphibole-biotite-quartzmagnetite- ilmenite-melt, under conditions of ~0.52–0.55 GPa/760–790 °C at ~2.21 Ga. Cooling toward the solidus occurred at ~ 2.10-2.08 Ga, and retrograde metamorphism is represented by the amphibole-biotite-quartz-magnetite-ilmenite-H₂O assemblage, developed under ~0.40–0.48 GPa/600–650 °C at ~2.01 Ga.
Acesso aberto (Open Access)
Petrologia experimental e química mineral das suítes Neoarqueanas Vila Jussara e Planalto, Província Carajás, Amazônia, Brasil
(Universidade Federal do Pará, 2023-03-20) CUNHA, Ingrid Roberta Viana da; SCAILLET, Bruno; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
In the Carajás Province (CP), during the late stages of the neoarchean (2.75-2.73), in the Sapucaia and Canãa dos Carajás domains granitoids represented by the Vila Jussara and Planalto suites were formed respectively. These suites are metaluminous and have a geochemical affinity with A-type granites and FeO/(FeO+MgO) whole rock ratios that vary from ferroan to magnesian. Chemical-mineralogical studies performed in these neoarchean granites, based on optical microscopy, scanning electronic microscopy, electron microprobe and experimental petrology revealed notable variation between the main mineral phases. Magmatic epidote is a common mineral phase in the reduced, oxidized and magnesian varieties of the Vila Jussara suite, with pistacite contents between 25 and 30% mol. In the Planalto Suite and others neoarchean granites of the CP magmatic epidote is absent. The study of the dissolution kinetics of Archean epidotes of the CP reveals that its formation and stability are directly linked to pressure, temperature and oxygen fugacity conditions, however, its stability is also conditioned by mechanisms of magma rise, emplacement and crystallization, which affected the dissolution intensity of the epidote crystals. Chemical-mineralogical performed on titanites of the Vila Jussara and Planalto Suites and the paleoproterozoic Jamon Suite revealed notable textural and compositional variations. The titanite’s Fe/Al ratios are quite variable in the studied granites, three major titanite groups were distinguished: 1) high Fe/Al ratio (Fe/Al>0.5); 2) moderate Fe/Al ratio (0.5≤Fe/Al≥0.25); and 3) low Fe/Al ratio (Fe/Al<0.25). Furthermore, in general, the obtained data support the major titanite tendency to stabilize under oxidizing conditions, near the nickel-nickel oxide buffer (NNO), however, the occurrence of magmatic titanite in the reduced varieties from the Planalto and Vila Jussara Suites ratifies that its crystallization is possible under conditions near the fayalite-magnetite-quartz buffer (FMQ). Moreover, experimental petrology studies performed on the same neoarchean suites, reveal that the sample MDP-02E, with tonalitic composition, which represents the magnesian oxidized magma from the Vila Jussara suite, exhibits SiO2 content around 60% in the whole rock composition and 61.05% in the experimental glass, while the sample with sienogranitic composition (AMR-116), from the strongly reduced variety of the Planalto Suite, shows SiO2 content of 74.13% in whole rock and 73.17% in glass, pointing out that the initially calibrated experimental conditions approach the natural magmatic conditions. To characterize the crystallization parameters of the tonalitic and sienogranitic magma, nine experiments were performed on the two samples, with the following conditions: pressure ~4 kbar, ƒO2 ~NNO-1.3 (1.3 log unit bellow the NNO buffer) and temperature varying from 850°C to 668°C and water content from 9% to 6% in weight. Experiments with ƒO2 ~NNO+2.4 and temperatures of 800°C to 700°C with similar pressures and water content variations of the reduced experiments were also performed. Subordinately, experiments with pressures of 8 to 2 kbar with variable redox conditions were performed. These experiments show that the tonalite from the Vila Jussara Suite was crystallized at ~4 kbar from a water-rich magma (>5% in weight) in ƒO2 oxidizing conditions, probably between NNO and NNO+1. On the other hand, the experiments performed on the sample with sienogranitic composition from the Planalto Suite show a main paragenesis of Cpx+Fa which substantially diverge from the natural minerals, suggesting that the experiments did not reach the natural conditions.
Acesso aberto (Open Access)
Petrologia magnética e parâmetros de cristalização do Charnoquito Rio Seco: Implicações para evolução de granitos neoarqueanos da Província Carajás.
(Universidade Federal do Pará, 2024-10-09) SANCHES NETO, Silvio; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506; http://lattes.cnpq.br/0294264745783506 Orcid iD ? https://orcid.org/0000-0001-7976-0472
This work presents new magnetic petrological data and crystallization conditions (T, fO2 and xH2O) of the Rio Seco Charnockite from a detailed study of the textural evolution of silicates and Fe-Ti oxide. The body is intrusive in Mesoarchean granitoids (2.88 Ga) and was subdivided into four petrographic types: (i) gabbronorite; (ii) ortho-clinopyroxene granodiorite; (iii) clinopyroxene-hornblende monzogranite; (iv) hornblende-biotite monzogranite. The magnetic values range from 0.231x10-3 to 22.1x10-3 Slv and shows bimodal character. Pyroxene-bearing rocks are concentrated in magnetic population A, whose magnetic susceptibility values range from 3.2x10-3 to 22.1x10-3, and are compatible with the SM values defined for oxidized neoarchean granites of the Carajás Province. Pyroxene-deprived rocks define magnetic population B, with lower values, between 0.231x10-3 and 0.309x10-3. They are included in the range of values defined for reduced granites. The amphibole crystallization temperature ranges from 713 to 809°C and the emplacement pressure ranges from 81 to 300 MPa. The fO2 (ΔNNO) ranges from -0.4 to +2.4 and the log fO2 from -12.0 to -16.0. The low Fe/(Fe+Mg) ratio in hornblende and biotite confirms the oxidizing conditions of these rocks, which belong to the magnetite series. The hygrometer used indicated water content in the magma ranging from 4.3 to 6.1% wt. The corona-type textures record the physical-chemical disequilibrium between silicates and favor the formation of magnetic minerals in the rocks with pyroxene. The rocks of population A present modal content of opaque minerals ranging from 0.2 to 1.7% with different degrees of exsolution of ilmenite in the magmatic stage (magnetite-ulvospinel series). The magnetic population B shows lower contents of opaque minerals (<0.3%) and is characterized by the presence of zoned goethite formed by oxyhydration processes in the late to post magmatic stage. The study of textural and mineralogical evolution reinforces the fractional crystallization model proposed in a previous work and explains the abundance of Fe-Ti oxide minerals in the variety with orthopyroxene, giving these rocks an oxidized character. The Charnockite Rio Seco has its emplacement controlled by a system of lineaments with ductile ruptile behavior, which is favorable to the interpretation of a pluton emplaced at shallow crustal levels. In deeper crustal conditions, the assimilation of crustal components may give rise to ferrous magmatism.
Acesso aberto (Open Access)
Petrologia magnética e química mineral dos granitoides mesoarqueanos de Ourilândia do Norte (PA)
(Universidade Federal do Pará, 2020-06-29) NASCIMENTO, Aline Costa do; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506; https://orcid.org/0000-0001-7976-0472
The Ourilândia do Norte area is located in the midwestern portion of the Carajás province, whose tectonic segment is comprised between the Rio Maria (RMD) and Carajás domains (CD), where outcrop three main Mesoarchean (2.92-2.88 Ga) granitoids: (i) leucogranite and associated high-Ti granodiorite – are constituted by equi- to heterogranular monzogranites and associated granodiorite with high titanite contents. Both of them have biotite as an essential mafic phase, lack amphibole and host TTG basement; (ii) sanukitoids – are represented by granodiorites (equigranular, heterogranular and porphyritic), with subordinate tonalite, quartz monzodiorite and quartz diorites occurrences. These rocks are characterized by the presence of hornblende as an essential mineral and associated mafic enclaves; and (iii) trondhjemite – represented by porphyritic granitoids with fine-grained mafic enclaves. Based on magnetic susceptibility (MS) studies these granitoids were distinguished into three magnetic populations: (i) lowest magnetic values (A; MS ranging from 0.05x10-3 to 0.57x10-3 SI) – characterized by rare opaques phases, predominant sanukitoids and trondhjemite; (ii) moderate magnetic values (B; MS 0.59x10-3 to 2.35x10-3 SI) – the modal ilmenite contents prevails over magnetite, with variable proportions of sanukitoids and leucogranites; and (iii) high magnetic values (C; MS 2.35x10-3 to 17.0x10-3 SI) – characterized by the highest magnetite contents, with subordinate ilmenite occurrence as trellis and composite textural types. The leucogranites and associated high-Ti granodiorite predominate over porphyritic sanukitoid. Amphiboles classify as magnesio-hornblende, characterized by Mg/(Mg+Fe+2) ratio ≥ 0.70, and minor occurrence of ferropargasite e actinolite-hornblende. For the trondhjemite, amphibole occurs as an acessory mineral and corresponds to magnesio- hornblende and tschermakite. Biotite crystals have Fe+2/(Mg + Fe+2) ratio down 0.6 in leucogranites and associated high-Ti granodiorite, and lower values (≤ 0.4) in sanukitoids and trondhjemite. Plagioclase crystals are predominantly oligoclase, without significant compositional variations between phenocrysts and matrix, and are frequently replaced by sericite. Although there are four distinct textural types of epidote and titanite, were investigated two main textural types: the former has magmatic origin and the latter indicate late-magmatic origin. In terms of the pistacite molecule contents in epidote {Ps = [Fe+3/(Fe+3 + Al)]*100}, Ps values of 25 to 36 %, 26 to 36 % and 22 to 30 % were estimated for the leucogranites, sanukitoids and trondhjemite, respectively, along with TiO2 contents ≤ 0.137, suggesting magmatic origin. Temperature estimative based on zircon (TZr) and apatite saturations (TAp) are in the range TZr 841-990 °C and TAp 884-979 °C (leucogranite and associated high-Ti granodiorite), TZr 826-972 °C and TAp 864-886 °C (sanukitoids) and, finally, TZr 853-977 °C and TAp 909 °C (trondhjemite), which all of them are interpreted as close to liquidus, with pressure estimates in general between 100 and 280 MPa, akin to upper crust conditions. Geothermometers and barometers based on aluminium contents in amphibole indicate temperature around 738-811 °C (sanukitoids) and 779-892 °C (trondhjemite). The lower temperatures(< 800 °C) is assumed as resulted of opening magmatic system related to deformation, and denote that dynamic recrystallization may have occurred at temperatures close to solidus, indicative of a syntectonic nature. Although the leucogranites and associated high-Ti granodiorite present relative enrichment of #Fe in whole- rock, are calc-alkaline affinity granitoids, overlapping the Cordilleran granites with SiO2 > 70%, low HFSE (high field strength elements) abundances, magmatic magnetite and high MS, pointing to oxidized crystallization conditions (problably at ∆NNO+2.8). Sanukitoids varieties have FeOt/(FeOt + MgO) < 0.7 in whole-rock, amphibole and biotite, low MS, indicating less oxidized crystallization conditions (∆NNO+1.0); however, the equigranular varieties and trondhjemite probably are formed in conditions relatively close to the ΔFMQ+0.5. The lower MS and lower magnetite contents reported for the sanukitoids and trondhjemite can also be attributed to the earlier epidote formation and to the late magmatic processes, which are responsible by the magnetite instability. It is concluded that the precursor magma of the sanukitoids are hydrated (H2O > 4-7 %), whereas lower water contents in melt (H2O < 4-7 %) are suggested for the leucogranites and associated high-Ti granodiorite; and trondhjemite, as indicated by their amphibole absence and acessory amphibole contents, respectively, along with low contents of hydrated mineralogy. These results are compared to those estimated for calc-alkaline rocks of the Rio Maria suite from the Carajás province and oxidized members from other Archean to Paleoproterozoic terrains such as Baltic Belt, Sarmatian orogen (Western Europe), Closepet-type granites and high-Mg granodiorites of the Matok pluton (Limpopo Belt – South Africa).