Programa de Pós-Graduação em Geologia e Geoquímica - PPGG/IG

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2603

O Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA) surgiu em 1976 como uma necessidade de desmembramento do então já em pleno desenvolvimento Curso de Pós-Graduação em Ciências Geofísicas e Geológicas (CPGG), instalado ainda em 1973 nesta mesma Universidade. Foi o primeiro programa stricto sensu de Pós-Graduação (mestrado e doutorado) em Geociências em toda Amazônia Legal. Ao longo de sua existência, o PPGG tem pautado sua atuação na formação na qualificação de profissionais nos níveis de Mestrado e Doutorado, a base para formação de pesquisadores e profissionais de alto nível. Neste seu curto período de existência promoveu a formação de 499 mestres e 124 doutores, no total de 623 dissertações e teses.

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Argila de Belterra das coberturas de bauxitas da Amazônia como matéria-prima para a produção de cerâmica vermelha
(Universidade Federal do Pará, 2018-01-10) BARRETO, Igor Alexandre Rocha; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
The Amazon region holds the largest reserves of bauxite in Brazil, whose deposits are covered by a thick bundle of clay material, known as Belterra Clay (ABT). The wide distribution, superficial occurrence, therefore accessible, and clayey ABT nature have aroused the interest of this work in evaluating its technical viability for the production of red ceramics. For the present study, ABT was selected from the large bauxite deposits of Rondon do Pará, samples of the yellow soils from Mosqueiro, illitic clay and gibbsitic clays and one sample of the clayey siltstone. This clay and other materials used as additives were characterized by X-ray Diffraction (XRD), X-Ray Fluorescence (FRX) (CT), Spectrometric Thermal Analysis (TG), Differential Scanning Calorimete (DSC), Inductively Coupled Plasma Spectrometry (ICP-MS), Coupled Plasma Optical Emission Spectrometry (ICP-OES), Scanning Electron Microscopy (SEM) Laser Particle (APL). To determine the physical and mechanical properties, were produce specimens through different mixtures with the samples of Belterra clay and percentages (20, 30 and 40%) of the yellow soil, clayey siltstone, gibbsitic clays and illitic clay. The specimens were calcined at three different temperature moments (900, 1000 and 1200 ° C). Then, linear retraction, water absorption, apparent porosity, apparent density and bending rupture tension were measured. ABT is essentially kaolinite, having quartz, goethite, anatase and gibbsite as accessory minerals. The pure and simple ABT did not present favorable technological aspects for the production of ceramic products, however the same with addition of the yellow soil and clayey silt from the same region significantly improved the technological characteristics of the ABT.
Acesso aberto (Open Access)
Contribuição à petrologia do granito central da serra dos Carajás
(Universidade Federal do Pará, 1980-09-02) ALMEIDA, Regina Célia Cunha; RONCAL, Juan Rolando Zuleta
This study was carried out in the central region of the Serra dos Carajás in the South of the State of Pará. The area referred to is underlain by a granite batholith, surrounded by basic volcanic rocks in the north-east and slightly metamorphised sedimentary clastic rocks. In order to characterize the petrogenetic nature of the granitic body, a study was realized of the petrography and petrochemistry of the various facies of the granite and of the country rocks. Petrographic and geochemical evidence suggests a magmatic origin for the granite of Carajás. During its consolidation the granitic magma underwent a slight differentiation in the formation of various facies. The intrusive character of the body is e4denced by the presence of contact metamorphism of the hornblende hornfels in the country rocks in the proximity of the contacts. The observed mineralogical association (orthoclase and plagioclase) indicates that the granitic body may be included in the SUBSOLVUS group in the classification of the Tuttle and Bowen (1958). The magma was probably originated by partial melting of older crustal rocks.
Acesso aberto (Open Access)
Dos minerais aos materiais de arquitetura e processos de degradação: edifícios e ornamentos metálicos dos séculos XIX e XX em Belém do Pará
(Universidade Federal do Pará, 2015-06-16) PALÁCIOS, Flávia Olegário; ANGÉLICA, Rômulo Simões; http://lattes.cnpq.br/7501959623721607
The use of iron in architecture was intensified during the second half of the XVIII century in Europe, and its influence spread over many countries in growth, such as Brazil. Belém (PA) was one of the cites that received the larger amount of building and ornaments imported, especially from England, France, Belgium and Portugal, during the XIX e XX centuries. Currently, Belém holds the largest number of iron architecture heritage remnants in the country. Despite of having great importance in construction techniques, many of these buildings were disassembled and remain on the wait for restoration processes. Also, studies about theses constructions only focus on historical and visual discussion, with no understanding of construction materials, causing empirical restoration processes. The knowledge about these materials is important to the detailed study of historical metal alloys, and different fabrication techniques, as well as weathering action, aiming future restoration processes with scientific bases. The main objective of this research is to understand the historical metals, their diversity in iron architecture and fabrication processes, and also weathering action in iron buildings and ornaments from the XIX and XX centuries in Belém. Thus, the following specific objectives were established: a) physical, chemical and mineralogical characterization of alloys and pathologies; b) identification of different kinds of alloys, in order understand the production types; c) determination of metallurgy evolution imported to the Amazon. The materials chosen for this research came from three different sites, due to their representativeness and diversity of pieces and origin: Mercado de Ferro do Ver-o-Peso building; the former chalet from the State’s Press; and the ornaments from tombs and mausoleums of the Soledade Cemetery. The methods used were Scanning Electron Microscopy (SEM) for physical characterization and punctual chemical analysis; and X-Ray Diffractometry (XRD) for mineralogical analysis. The results were presented in three scientific papers indicating: 1) iron alloys mostly composed by ferrite; 2) textural variations exhibiting four types for the building group: nodular cast iron, gray cast iron type E, wrought iron and gray cast iron type B; 3) three classification of gray cast iron for the ornamental group of diverse origins, among A, B and D; 4) corrosion as main weathering action, and products constituted by goethite and hematite; 4) remnant paint coats, formed by metallic zinc, and its products of alteration represented by zincite and hidrozincite. Through the results of this research it was possible to indicate the evolution of processes in iron architecture production, and enrich this research area with scientific information, as subside for future restorative processes.
Acesso aberto (Open Access)
Estudos isotópicos de U-Pb, Lu–Hf e δ18o em zircão: implicações para a petrogênese dos granitos tipo-A paleoproterozóicos da província Carajás – Cráton Amazônico
(Universidade Federal do Pará, 2018-04-05) TEIXEIRA, Mayara Fraeda Barbosa; SANTOS, João Orestes Schneider; http://lattes.cnpq.br/5516771589110657; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
In ca. 1880 Ma an extensive magmatic event generated A-type granites with rapakivi affinity in the Amazonian Craton, especially in the Carajás Province. In this Province these granites are grouped into three main suites according to mineralogy, geochemistry, and state of oxidation of their magmas – Jamon, Velho Guilherme, and Serra dos Carajás – and include also the Gogó da Onça, Seringa, São João, Gradaús, and Rio Branco plutons. The Gogó da Onça Granite (GOG) comprise a stock composed by biotite-amphibole granodiorite, biotiteamphibole monzogranite and amphibole-biotite syenogranite. The GGO crosscut discordantly the Archean country rocks and are not foliated. All Gogó da Onça Granite varieties are metaluminous, ferroan A2-subtype granites with reduced character. The major and trace element behavior suggests that its different facies are related by fractional crystallization. Zircon and titanite U–Pb SHRIMP ages show that the pluton crystallized at ~1880-1870 Ma. This is more akin to the Serra dos Carajás Suite and to the Seringa and São João granites of Carajás and to the Mesoproterozoic Sherman granite of USA and the Paleoproterozoic Suomenniemi Batholith of Finland. New U-Pb SHRIMP data for the Serra dos Carajás, Velho Guilherme and Jamon Suite and for Seringa and São João Granite show that these plutons crystallized between 1880 Ma to 1857 Ma. Some granites of the Velho Guilherme and Jamon suites and of the Seringa Granite presented 1920 to 1900 m. y. old zircon and titanite crystals interpreted here as antecrysts from an earlier pulse of magma that were incorporated in the main later pulse of 1880 Ma. We also obtained ages of 1865 Ma to 1857 Ma in the leucogranite facies of the Redenção and Bannach plutons, which indicate that the leucogranites of these plutons are younger than their ~1880 Ma old granites and were generated by independent magma pulses that are not cogenetic with the less evolved facies of the respective plutons. Besides it, an age of 1732 ± 6 Ma obtained in the leucogranite facies of the Antônio Vicente pluton of the Velho Guilherme Suite that could represent a magmatic event in the Xingu Region not yet reported or, eventually, could correspond to an isolate hydrothermal event that allowed the growth of zircons. This ranites have been also analysed by Lu–Hf and Oxygen isotopes and few granites also by Nd isotopes. Zircons from all the granites have remarkably restricted initial 176Hf/177Hf (0.281156 and 0.281384) and strongly negative εHf(t) values ranging from –9 to -18, and δ18O fairly homogeneous varying from 5.50‰ to 7.00‰. Small differences were observed internally in the plutons or between them. The ƐHf(t) values of the analysed plutons are strongly negative and similar to Nd isotopic data. The Serra dos Carajás Suite has ƐHf(t) values of -14 to -15.5, the Jamon Suite of -9.5 to -15 and values of -12 to -15 for the Velho Guilherme Suite, while São João, Seringa and Gogó da Onça granites have stronger negative values (ƐHf(t)= -12 to -18). Crustal model ages indicate a Paleoarchean source (3.3 Ga to 3.6 Ga) with a minor contribution from Mesoarchean (3.0 Ga to 3.2 Ga) melts for these granites. This model ages are older than the exposed Archean country rocks of the Orosirian granites of the Carajás Province and more investigation is needed to verify the real existence of that older Archean crust. The studied samples have Hf– O isotopic compositions that overlap within error, and evidence of contamination (crustal assimilation or mixing) of a mantle-derived magma cannot be seen. These plutons crystallized from magmas generated by melting of pre-existing igneous rocks with possibly in the Velho Guilherme Suite a minor contribution from a supracrustal (metasedimentary) component. The Nd, Hf, and O isotope compositions of the Paleoproterozoic granites of Carajás Province clearly attest to an igneous ancient crustal source in the origin of their magmas. The differences observed can result for contrasts in the crustal domains of the Carajás Province that were the source of the granites or of local contamination processes.
Acesso aberto (Open Access)
Evolução geológica da porção centro-sul do Escudo Guianas com base no estudo geoquímico, geocronológico (evaporação de Pb e U-Pb ID-TIMS em zircão) e isótopo (Nd-Pb) dos granitóides paleoproterozóicos do sudeste de Roraima, Brasil
(Universidade Federal do Pará, 2006-11-17) ALMEIDA, Marcelo Esteves; MACAMBIRA, Moacir José Buenano; http://lattes.cnpq.br/8489178778254136
This study focuses the granitoids of center-southern portion of Guyana Shield, southeastern Roraima, Brazil. The region is characterized by two tectono-stratigraphic domains, named as Central Guyana (GCD) and Uatumã-Anauá (UAD) and located probably in the limits of geochronological provinces (e.g. Ventuari-Tapajós or Tapajós-Parima, Central Amazonian and Maroni-Itacaiúnas or Transamazon). The aim this doctoral thesis is to provide new petrological and lithostratigraphical constraints on the granitoids and contribute to a better understanding of the origin and geodynamic evolution of Guyana Shield. The GCD is only locally studied near to the UAD boundary, and new geological data and two single zircon Pb-evaporation ages in mylonitic biotite granodiorite (1.89 Ga) and foliated hastingsite-biotite granite (1.72 Ga) are presented. These ages of the protholiths contrast with the lithostratigraphic picture in the other areas of CGD (1.96-1.93 Ga). Regional mapping, petrography, geochemistry and zircon geochronology carried out in the UAD have showed widespread paleoproterozoic calc-alkaline granitic magmatism. These granitoids are distributed into several magmatic associations with different paleoproterozoic (1.97-1.89 Ga) ages, structural and geochemical affinities. Detailed mapping, petrographic and geochronological studies have distinguished two main subdomains in UAD. In the northern UAD, the high-K calc-alkaline Martins Pereira (1.97 Ga) and Serra Dourada S-type granites (1.96 Ga) are affected by NE-SW and E-W ductile dextral shear-zones, showing coexistence of magmatic and deformational fabrics related to heterogeneous deformation. Inliers of basement (2.03 Ga) crop out to northeastern part of this area, and are formed by metavolcano-sedimentary sequence (Cauarane Group) and TTG-like calc-alkaline association (Anauá Complex). Xenoliths of meta-diorites (Anauá Complex) and paragneisses (Cauarane Group) reinforce the intrusive character of Martins Pereira Granite. On the other hand, xenoliths of Martins Pereira and biotitebearing enclaves are founded in the younger, undeformed, and SiO2-rich Igarapé Azul Granite (1.89 Ga). This last and the high-K calc-alkaline Caroebe Granite (1.90-1.89 Ga, Água Branca Suite), including coeval volcanic rocks (1.89 Ga, Jatapu volcanics) and charnockitoids (1.89 Ga, e.g. Santa Maria Enderbite), crop out in the southern UAD. This subdomain is characterized only by local and slight NE-SW ductile-brittle dextral shear zones. A-type granites such as Moderna (ca. 1.81 Ga) and Mapuera (ca. 1.87 Ga) granites, cross cut both areas of UAD. Furthermore, the geological mapping also identified three main types of metalotects in this region. Gold mineralization is observed in Martins Pereira-Serra Dourada granitoids (northern UAD), alluvial columbite-tantalite is related to Igarapé Azul granitoids (southern UAD), and amethyst is associated to pegmatites from Moderna A-type granites. The Nd-Pb isotope data suggest that all granitoids of UAD are generated by reworking of older and pre-existence crustal sources (sialic Rhyacian-Archean and/or juvenile Transamazonian origin) and mantle input is not problably a viable model. Although the dominant process may be one subduction in the early stage of NUAD evolution, post-colisional magmatism may be a significant process in the production of new continental crust in the southern UAD. It is possible that, following oceanic closure in the Anauá arc system (2.03 Ga) and subsequent collisional orogeny (1.97-1.94 Ga?), underplated mantle melts (basalt liquids) were trapped below preexisting lower crustal rocks of various compositions (e.g. granulites, metatonalites, amphibolites). The basalt liquids and subsequently melted lower crust could produced the immense volumes of granite (and volcanics) observed at 1.90-1.87 Ga. This geological picture is similar to the Tapajós Domain (TD) in the southern Amazonian Craton and suggest that both belongs to the same province (Ventuari-Tapajós or Tapajós-Parima). Nevertheless, the scarcity of S-type granites and high-grade metamorphic rocks show that the collisional stage is not so evident in TD.
Acesso aberto (Open Access)
Evolução magmático-hidrotermal do granito mocambo, Província Estanífera do Sul do Pará: um estudo morfológico e composicional de quartzo e cassiterita
(Universidade Federal do Pará, 2018-10-02) BARROS NETO, Rubem Santa Brígida; LAMARÃO, Claudio Nery; http://lattes.cnpq.br/6973820663339281
The present research deals with the morphological, compositional and textural aspects of quartz and cassiterite crystals of the Mocambo Granite (MG) and of associated greisens bodies, belonging to the Velho Guilherme Intrusive Suite, Carajás Province, and its relation with the tin mineralization. The study was performed with the aid of scanning electron microscope (SEM), using catodoluminescence (CL) images, semiquantitative analyzes by energy dispersive spectroscopy (EDS) and by electronic microprobe (EM) analyzes. Different facies and greisenized rocks of the MG were studied and it was possible to identify five types of quartz, called Qz1, Qz2, Qz3, Qz4 and Qz5. The Qz1, considered the most earlier type and of magmatic origin, can be found in all facies, being less frequent in the greisens. It appears as anhedral phenocrysts to luminescent sub-rounded (light gray), with varying degree of fracturing, as well as fine-to medium-grained crystals dispersed in the groundmass. Luminescent nuclei with alternating or reasorbed alternating light-dark zonations are common. Qz2 is posterior to Qz1 and not luminescent (dark gray); is present in all facies, but is rare in the greisen. It usually occurs as irregular discontinuous stains or filling fractures and shafts that section the Qz1, suggesting a process of intense replacement. The Qz3 does not show luminescence. It occurs in almost all facies filling a fracture that cuts Qz1 and Qz2. The Qz4 is present in the most evolved and intensely altered rocks, in the greisen and in veins or interstitial cavities, usully associated with cassiterite crystals. It is represented by euhedral, medium-greined, slightly fractured crystals, with well-defined light-dark zoning and variable thickness. Qz5 occurs sectioning and forming irregular spots on Qz4, being associated generally with wolframite or wolframite + cassiterite in quartz veins. They are slightly fractured, luminescent, meduium-to-coarse greined anhedral crystals. Qz1 and Qz2 from porphyritic syenogranite to monzogranite facies show high Ti concentration (9.5 - 104 ppm) and low Al (10 - 149 ppm). Qz1, Qz2 and Qz3 crystals from the aplitic alkali-feldspar granite facies presented slightly lower Ti contents (5 - 87 ppm) in comparison to SGMP quartz values and Al values that reach 2065 ppm. In the Qz1, Qz2 and Qz3 of the greisenized rocks, the Ti presented lower contents (0.0 and 62 ppm) and variable Al content (0 - 167 ppm). In the Qz4 crystals of the mineralized greisenized rocks in cassiterite, the Ti did not exceed 20 ppm, while Al presented strong enrichment, exceeding 3000 ppm. In the mineralized quartz veins in wolframite or wolframite + cassiterite, consisting mainly of Qz5, the Ti and Al concentrations presented generally low values, with maximum contents of 7 and 77 ppm, respectively. The cassiterite is occur as anhedral to subhedral fine-to coarse-grained crystals, anhedral to subhedral, associated to chlorite, muscovite, fengite and siderophyllite in gresenizeds rocks or commonly included in wolframite crystals in quatz veins. Shows light brown to reddish color and high colors of interference. More developed crystals show concentric zoning. Analyzes carried throug ME showed that in addition to Sn, cassiterites have lower concentrations of Fe, Ti, W, Nb and Mn traces. The concentrations of Fe, Nb, Ti and W are higher in the darker spots, while Sn shows higher purity in the lighter parts of the crystals. Cassiterites associated with Qz5 (hydrothermal) are often included in wolframite crystals or are partially substituted by it. This study showed that quartz was an excellent marker of the magmatic evolution and late alteration resulting from hydrothermal processes that operated in the Mocambo granite. It was possible to distinguish one magmatic and four hydrothermal types of quartz. The CL images indicate that the tin mineralization is present in the most evolved rocks and hydrothermally altered as in greisenized rocks and quartz veins, where the cassiterite is associated with Qz4 or Qz5 + wolframite. Qz5 suggests a possible mineralizing hydrothermal event of wolframite, subsequent to the origin of the cassiterite associated with Qz4.
Acesso aberto (Open Access)
Geocronologia U-Pb, classificação e aspectos evolutivos do Granito Marajoara – Província Carajás
(Universidade Federal do Pará, 2018-01-24) SANTOS, Rodrigo Fabiano Silva; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The Marajoara granite (MjGr) is a stock intrusive in mesoarchean granitoids of the Rio Maria domain, which is formed mainly by leucocratic rocks, represented by equigranular (BMzE) and heterogranular (BMzH) monzogranite facies. Rapakivi texture and occurrences of porphyritic granite (EGp) and microgranular enclaves (EMg) are restricted to BMzH facies. Such varieties have similar mineralogy: microcline, quartz and plagioclase occur as essential minerals; biotite partially altered to chlorite as the only varietal phase; zircon, titanite, opaque, apatite and allanite as primary accessories; and chlorite, sericite-muscovite, epidote, fluorite and clay minerals as secondary phases. The high magnetic susceptibility (SM) values (2.3-6.5 x10-3) and the frequent presence of magnetite show that the BMzH facies is akin to granites with magnetite series, whereas the BMzE variety shows affinity with the ilmenite series considering the modal opaque contents ≤0.5%, low values of SM (<0.15x10-3), and ilmenite as the sole Fe-Ti oxide. These rocks are, in general, peraluminous and have high FeOt/FeOt+MgO ratio, similar to the ferroan granites. In addition, they have geochemical affinities with intraplate A-type granites, which have crustal origin, wherein a significant variation of FeOt/(FeOt + MgO) found for these rocks [EGp (> 0.82); BMzH (> 0.86); BMzE (> 0.97)], allow them to be classified as oxidized (BMzH and EGp) and reduced (BMzE) Atype granites, that are related to the Jamon and Velho Guilherme suites, respectively. Differently from this, the EMg show clear affinity with the magnesian granites and the calcalkaline series. Evidence of magma mixing and geochemical modeling calculations demonstrate that EGp originate from the interaction of EMg (60%) and BMzH (40%) liquids. The compositional gaps existing among the several varieties that constitute the MjGr, as well as their compositional contrasts, suggest that their magmas are not cogenetic. The EMg represents a basic magmatism from the enriched lithospheric mantle that would have been injected into the magma chamber during the underplating process and at different phases of the granitic magma crystallization. The U-Pb zircon isotopic analyzes (SHRIMP) yielded an age of 1885 ±6Ma, interpreted as the crystallization age of MjGr. The MjGr was emplaced at shallow crustal levels (epizone) in an extensional tectonic environment with the effort following the trend NNE-SSW to ENE-WSW. The concentric zoning in the MjGr and the rheological behavior of its country rocks as well as the reduced or no influence of the regional efforts during the emplacement of the pluton indicate that the transport of the magma occurred through dikes. It is suggested that the construction of the MjGr was a result of the vertical rise of magmas through fractures and accommodation along the planes of the regional EW foliation, followed by a change of the vertical flow by a lateral scattering of the magma, analogous to the admitted model for the emplacement of the tabular batholiths of the Jamon Suite.
Acesso aberto (Open Access)
Geologia, geoquímica e geocronologia do magmatismo paleoproterozóico da região de Vila Riozinho, Província Aurífera do Tapajós, Cráton Amazônico
(Universidade Federal do Pará, 2001-09-27) LAMARÃO, Cláudio Nery; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
Several Paleoproteroic granitoids and two volcanic sequences were studied in the Vila Riozinho region. This region is located in the eastern area of the Tapajós Gold Province, near the border between the Tapajós and Central Amazonian tectonic provinces in the south-central part of the Amazonian craton. In the southern part of the region, it was identified the Vila Riozinho volcanic sequence composed of basaltic andesite, basaltic trachyandesite, trachyte and rhyolite, with a high-K calc-alkaline to shoshonitic geochemical signature. Pb-Pb zircon dating indicate ages of 2000 + 4 Ma and 1998 + 3 Ma for this sequence. The São Jorge granite pluton is spatially associated with this volcanic sequence. Two granitoids were distinguished in the pluton, the Old São Jorge granite, with Pb-Pb zircon ages of 1981 + 2 Ma and 1983 + 8 Ma, and the Younger São Jorge granite with an age of 1891 + 3 Ma. The Older São Jorge granite, largely dominant in the pluton, is composed of an expanded magmatic series including biotite-amphibole monzodiorite/quartz monzodiorite, amphibole-biotite monzogranite/quartz monzonite, biotite leucomonzogranite/syenogranite and granite porphyry. It has a metaluminous to mildly peraluminous character, and high-K cale-alkaline signature, similar to that of volcanic arc granitoids. The Younger São Jorge granite was initially identified in drill cores obtained in the gold mineralized area of the pluton. In that area, it corresponds to a hornblende-biotite monzogranite, but biotite leucogranites occur in the southern part of the pluton. This granite also has a high-K calc-alkaline signature, but it differs from the Older São Jorge granite in some geochemical and mineralogical aspects and it is comparatively younger. In the northern part of the Vila Riozinho region, it was identified the Moraes Almeida volcanic sequence, the Maloquinha and Jardim do Ouro granites and a granite porphyry distinct from that associated with the Older São Jorge granite. The Moraes Almeida Formation is composed of ignimbrite and rhyolite with subordinate trachyte, with Pb-Pb zircon ages of 1875 + 4 Ma, 1890 + 6 Ma and 1881 + 4 Ma, respectively. The 1880 + 9 Ma old Maloquinha granite is composed of leucosyenogranite and subordinate leucomonzogranite. This granite and the rhyolite and ignimbrite of the Moraes Almeida Formation show affinities with aluminous, A-type series. The strong petrographic and geochemical similarities between these rocks suggest that they are cogenetic. An age of 1880 + 3 Ma, similar to that of the Maloquinha grafite, was obtained for the Jardim do Ouro hornblende-biotite monzogranite. However, preliminary data indicate that it differs from the former, as well as from the Older São Jorge and Younger São Jorge granites, in petrographic and geochemical aspects. Geochemical and mineralogical data allow the distinction of two different types of grafite porphyries. The first one is spatially associated and similar to the Older São Jorge granite. The second occurs along the contact between the Maloquinha granite and the ignimbrite of the Moraes Almeida Formation and is geochemically similar to the Jardim do Ouro granite and trachyte of the Moraes Almeida Formation. The magmatic activity in the Vila Riozinho region is concentrated into two distinct periods, near the end of the Paleoproterozoic. The Vila Riozinho Formation and the Older São Jorge granite formed during the first period between 2010 and 1970 Ma. At the second period, between 1900 and 1870 Ma, the Moraes Almeida Formation, Maloquinha, Younger São Jorge and Jardim do Ouro granites were formed. The high-K calc-alkaline magmatism that was formed during the first period is probably related to subduction processes. Two hypotheses are considered to explain the diversified magmatic activity registered during the second period: (1) the different magmas could result from late tectonic activity related to the subduction processes; (2) these magmas are related to taphrogenetic processes that affected the Amazonian craton at 1.88 Ga and lasted the entire Mesoproterozoic. It implies to admit a crustal source for the magmas originated during the second period. The second hypothesis is assumed as the more plausible at this stage, but the need for additional isotopic information is emphasized.
Acesso aberto (Open Access)
Geologia, geoquímica e mineralogia dos corpos anfibolíticos de Água Azul do Norte: condições metamórficas e implicações tectônicas para o Domínio Sapucaia - Província Carajás
(Universidade Federal do Pará, 2016-11-09) SOUZA, Diwhemerson Barbosa de; MONTEIRO, Lena Vírginia Soares; http://lattes.cnpq.br/6455990478032543; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The metamafics bodies identified in the Água Azul do Norte area, located in the south-central portion of the Carajás domain, crosscut the TTG basement and include two distinct varieties: (i) actinolite amphibolite, an extensive elongated body (~17 km long) with N-S orientation and inflection to NE, composed essentially of plagioclase and amphibole, with relicts of igneous pyroxene crystals and plagioclase, defining a subophitic texture; and (ii) diopside amphibolite, with occurrence restricted to the extreme east portion of the area, outcropping as small lenticular anastomosed bodies of NW-SE orientation. The latter shows nematoblastic and porphyroblastic textures, mylonitic foliation, and S-C pairs. The mineral paragenesis recognized in this variety include: Plg+Amph+Di+Ilm, which represent the metamorphic peak, while Plg+Amph+Ep+Clz+Tit+Ap+Qtz+Ser were generated during the retrometa-morphism. The plagioclase from the actinolite amphibolite has a broad compositional spectrum, ranging from calcic oligoclase to calcic labradorite (An28-65) with calcic compostions representing igneous inheritances. The plagioclase from the diopside amphibolite has more homogeneous composition and was classified as sodic andesine (An31-35). The amphibole from the actinolite amphibolite shows compositional zoning with Mg/Fe ratio slightly higher than those of the diopside amphibolite, and can be classified as Mg-hornblende, tschermakite, actinolite and edenite. In addition, the amphibole of the diopside amphibolite has AlVI of ~0.4 and Fe3+ of 0.7 to 0.8 contents, which allows its classification as Mg-hastingsite. Taking into account the chemical data, these bodies had a protolith with composition compatible with tholeiitic basalts, multielement standard of continental tholeiites (diopside amphibolite) and tholeiites low K (actinolite amphibolite), incompatible elements (HFSE) ratios suggest a source derived from primitive mantle, with significant changes in the magma composition due to interaction with the continental crust and/or subcontinental lithosphere. The chemical-mineralogical and textural evidences indicate that the protolith of actinolite amphibolite underwent deformation in the submagmatic stage and later a deformation in solid state at shallow depths. In contrast, the diopside amphibolite was submitted to ductile deformation regime in relatively higher depths. The metamorphic path of the actinolite amphibolite reveals isothermal decompression (metamorphic peak at 2.7 kbar and 430 °C; and retrometamorphic equilibrium at 1.2 kbar and 425 °C), associated with its exhumation and/or emplacement of leucogranite bodies, whereas the diopside amphibolite indicates amphibolite facies metamorphism in intermediate crustal level conditions (5 kbar; 540oC). These data indicate the exposure of relatively deep crustal levels in Água Azul do Norte (9-16 km).
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Geologia, geoquímica e petrologia magnética do magmatismo básico da área de Nova Canadá (PA), Província Carajás
(Universidade Federal do Pará, 2013-08-29) MARANGOANHA, Bhrenno; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
Through geologic mapping of the Nova Canadá area, was possible to individualize two mafic units, typified for diabase dikes, isotropic, and extensive bodies of amphibolites with nematoblastic and granoblastic textures, outcropping only in the southwestern part of the area. Both units cross-cut granitoids of Xingu Complex and Sapucaia greenstone belts sequence. They are classified as subalkaline tholeiitic basalts. Diabase dikes are divided into three varieties, namely hornblende-gabbronorite, gabbronorite and norite, being the differences between these ones only concerned the modal contents of amphibole, ortho- and clinopyroxene, once petrographically, they don’t show significant differences. They consist of plagioclase, ortho-/clinopyroxene, amphibole, Fe-Ti oxides and olivine; they show a moderate fractional pattern REE and unremarkable negative Eu anomaly. Tectonically, they are related to a continental intraplate environment, and show OIB and E-MORB-types signatures. On the other hand, the amphibolites show a flat REE pattern and an absence of Eu anomaly. They are classified as island arc tholeiites and show N-MORB-type signature. This lithotype includes plagioclase, amphibole, opaque minerals, titanite and biotite as main mineralogical phases. The mineral chemistry shows in the diabases no significant variation between plagioclase core and rim, being classified as labradorite, with rare andesine and bytownite; the amphibole shows a compositional gradation from Fe-hornblende to actinolite with increasing silica. In the amphibolites, the plagioclase shows a wide compositional variation, from oligoclase to bytownite in the foliated rocks; in the amphibolites less/no foliated, there is only sodic andesine. Pyroxene is only found in the diabase dikes and exhibits considerable variation compositional, showing a magnesium content increasing in the cores; the iron and calcium contents increase toward the rims; it is classified as augite, pigeonite (clinopyroxene) and enstatite (orthopyroxene). Diabase dikes have titanomagntite, magnetite and ilmenita as main Fe-Ti oxides. Textural analyses of these oxides allowed identifying five distinct forms of ilmenite in the diabase dikes: trellis ilmenite, sandwich ilmenite, patch ilmenite, individual ilmenite, internal and external composite ilmenite. Texture features suggest that titanomagnetite and individual and external composite ilmenite crystallized in early magmatic stage. During the subsolidus stage, titanomagnetite was transformed by oxidation-exsolution in intergrowths of almost pure magnetite and ilmenite (sandwich, patch, trellis and internal composite ilmenite). Amphibolites have ilmenite as the only Fe-Ti oxide mineral, that occurs as individual ilmenite, and it is always associated to amphibole and titanite. Norites and gabbronorites are characterized by the highest values of the magnetic susceptibility (MS); these varieties exhibit the highest modal opaque minerals content, having primary titanomagnetite as mineralogical phase. Hornblende-gabbronorites exhibit the moderate values of the MS, and amphibolites, the lowest ones. The negative correlation between MS values with modal ferromagnesian contents of the diabases shows that paramagnetic minerals (amphibole and pyroxene) don’t have significant influence in the magnetic behavior in these rocks. In contrast, the positive correlation between these variables, of the amphibolites, suggests these mineral phases are the main responsible for its values of the MS. Geothermobarometric data obtained from titanomagnetite-ilmenite pair in the diabase dikes show temperature and oxygen fugacity conditions (1112°C and -8,85, respectively) close to NNO buffer.
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Geologia, petrografia e geoquímica das associações leucograníticas e TTG arqueanos da área de Nova Canadá (PA) Domínio Carajás
(Universidade Federal do Pará, 2014-02-25) SANTOS, Pablo José Leite dos; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The geological mapping carried out in the Nova Canada and Velha Canada villages, south portion of the Carajas Domain, ally to the petrographic and geochemical data allowed to the characterization of new geological units before inserted in the Xingu Complex geological context. In abundance order they are: (i) Nova Canada Leucogranodiorite composed predominantly by leucogranodiorite rocks that are more enriched in Al2O3, CaO, Na2O, Ba, Sr and in the Sr/Y ratio. They show strong geochemical affinities with Guarantã Suites from the Rio Maria Domain, which are also correlated to Transitional TTGs from Yilgarn Craton. Their REE pattern is slightly fractionated with low (La/Yb)N ratios with Eu negative anomalies absent or discrete; (ii) Velha Canadá Leucogranite comprised essentially by leucogranitic rocks that show higher contents of SiO2, Fe2O3, TiO2, K2O, Rb, HFSE (Zr, Y e Nb), and K2O/Na2O, FeOt/(FeOt+MgO), Ba/Sr e Rb/Sr ratios. The Velha Canada area rocks are characterized by two distinct patterns REE of: (a) moderate to low (La/Yb)N ratios with accentuated Eu negative anomalies, and (b) high to moderate (La/Yb)N ratios with discrete Eu negative anomalies. A concave HREE pattern is observed. In several aspects, the Velha Canada granite show similarities with K-Leucogranites like Xinguara and Mata Surrão granites from Rio Maria Domain, and more discretely with low-Ca granites from Yilgarn Craton. To origin of Nova Canadá Leucogranodiorite rocks is admitted fractional crystallization by sanukitoid liquids, following by mixing with trondhjemitic magmas, while for those high-K rocks is assumed partial melting of metatonalites rocks related to TTG Suites on different crustal levels, for give rise to these liquids; and (iii) Trondhjemitic associations with high-Al and low-K calc-alkaline TTG series affinities. Two varieties were distinguished: (a) biotite-trondhjemite with deformational features like compositional banding, folds and evidence of migmatization, suggesting the presence at least two compressional events during the sin- and post magmamtic stages; and (b) (muscovite) biotite-trondhjemite that differs from the previous one by the presence of muscovite, plagioclase saussuritization, medium evengrained texture and discrete deformation features with development of a low-angle foliation with E-W direction. The restrict occurrence of the first one, ally with intense deformation and eventual anatexie processes that affected these rocks, can indicate a crustal rework linked to generation of the leucogranites described in the Nova Canadá area. The trondhjemites of the southern part of area are more enriched in Fe2O3, MgO, TiO2, CaO, Zr, Rb, an in the Rb/Sr ratio in relation to those of the northern part. The arrangement of trends defined by the set of analyzed samples, suggests that theses varieties are not cogenitc or comagmatic. These rocks also show fractionated REE patterns, with variations in contents of the heavy REE and Strong light REE enrichment, besides the absence of the Eu and Sr anomalies, and low contents of Yb and Y. Such aspects are tipically attributed to magmas generated from partial melting of a mafic source at different depths, with increasing of the garnet influence in the residue, as well as the lack of plagioclase in both residual and fractionating phases. Geochemical affinities between the rocks studied with those of the mesoarchean Rio Maria domain, suggest the extension of Rio Maria Domain to north until the Nova Canadá area, while that the leuocogranodiorites of the Velha Canadá area, that are younger and generated in the neoarchean, discard the hypothesis to associate the generation of these rocks to the same tectonic-magmatic events that acted in Rio Maria.
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Geologia, petrografia e geoquímica das associações TTGs e Leucogranodioritos do extremo norte do Domínio Rio Maria, Província Carajás
(Universidade Federal do Pará, 2013-06-18) SILVA, Chrystophe Ronaib Peixoto da; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The geological mapping carried out in the southeastern portion of Água Azul do Norte / PA, northern part of the Rio Maria domain, ally to the petrographic and geochemical data allowed the individualization of TTGs associations and leucogranodiorites. In this region, mapping was performed only on regional scale which allowed the extrapolation of the area of occurrence of rocks similar to Caracol Tonalite and Mogno Trondhjemite. The TTGs studied were individual in two units based on the contents of mafic minerals, concentration of magmatic epidote and degree of saussuritization of the plagioclase in: (1) Epidote-Biotite Tonalite and, (2) Biotite-Trondhjemite. In general, rocks which have a foliation defined by compositional banding which locally can be disturbed by folds and shear bands. Their geochemical characteristics are consistent with Archean TTG group of high Al2O3 and are still relatively poor in ferromagnesian elements, with HREE pattern moderaly to strongly fractionated and Eu discrete anomalies. The differences in the ratios La/Yb and Eu anomalies, allowed todiscrimination three distinct groups of rocks: The TTGs belonging to the group of high La/Yb, Sr/Y are similar to rocks Mogno Trondhjemite described in Rio Maria Domain. These rocks include the most samples of the unit Biotite Trondhjemite. In the case of TTGs with medium to low La/Yb, Sr/Y compared with the rocks of the Rio Maria area are strongly correlated with the Tonalite Caracol. These groups are composed mainly by unit Epidote- Biotite Tonalite, including also isolated samples the Biotite Trondhjemite. On the basis of geological, petrographic and geochemical data leucogranodiorites of the study area were divided into two groups: Biotite Granodiorite and Leucogranodiorite. The rocks of the Biotite Granodiorite have wide spatial occurrence in the western portion of the area. Field relationships show that these rocks are intrusive in granitoids TTGs. The available geochemical indicate that the Biotite Granodiorite have as well fractionated REE patterns, with high ratio La/Yb (33-186) and Eu anomalies quite pronounced, being strongly positive (1,11 < Eu/Eu* < 3,26). Whereas leucogranodioritos show slightly fractionated patterns, with moderate ratios La/Yb (24.7 to 34.7) and Eu anomalie absent (Eu / Eu * = 1.03). The Harker diagrams for major and trace elements do not favor a genetic link by fractional crystallization processes between the Biotite Granodiorite and TTG associations, considering present distinct evolution trends, thus indicating that the conditions of their genesis and differentiation were quite different, either by partial melting of a TTG source by the fact of the leucogranites not to present significant negative Eu anomaly, as well as for to show similar patterns of REE fractionation in relation to TTG suites, attesting that these rocks were probably not derived from precursor magmas of the TTG suites.
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Geologia, petrografia e geoquímica dos granitóides arqueanos de Sapucaia - Província Carajás-PA
(Universidade Federal do Pará, 2013) TEIXEIRA, Mayara Fraeda Barbosa; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
Geological mapping performed in the eastern portion of the Transition Subdomain, Carajás Province, southern of Canaã dos Carajás and the northern of Sapucaia cities, allowed the identification, individualization and characterization of a variety of Archean rocks, previously encompassed in the Xingu Complex. The oldest unit identified in this area is a hornblende tonalite, correlated to São Carlos Tonalite (~2.93 Ga), which is exposed as blocks or outcrop and commonly present foliation (NW-SE to E-W) or homogeneous aspect. Its geochemical signatures differ from the typical Archean tonalite-trondhjemite-granodiorite (TTG) associations due to show enrichment in TiO2, MgO and CaO, low contents of Sr, and Rb contents similar to samples with lower concentrations of silica, which are reflected in higher Rb/Sr ratios and lower Sr/Ba ratios. The REE patterns reveal low to moderate fractionation of HREE compared to LREE, and discrete or moderate negative Eu anomalies. It is stratigraphycally followed by TTG association correlated to Colorado Trondhjemite (~2.87 Ga) which displays gray color, medium-grained, and commonly a NW-SE to E-W foliation. In the southern of area, outcrops a body of 40 km 2, which comprises a small mountain of porphyritic leucogranodioritic rocks named Pantanal Leucogranodiorite . It is emplaced at TTG association and crosscutted, on its western portion, by deformed leucogranites. The Pantanal Leucogranodiorite shows peraluminous character and calc-alkaline affinity, with high contents of Ba and Sr. The REE patterns show nosignificant Eu anomalies and HREE are strongly fractionated, which is geochemically similar to Guarantã Suite (~2.87 Ga) from the Rio Maria Domain. Its origin may be related to low degrees of melting of TTG, probably accompanied by interaction with fluids enriched in K, Ba and Sr, derived from a metasomatized mantle. The leucogranites exhibit A-type geochemical signature and reduced character, and may have originated from the melt of dehydrated peraluminous calcic-alkaline rocks, during the Neoarchean. In the eastern portion of the Pantanal Leucogranodiorite was also identified ahornblende-biotite monzogranite which is geochemically similar to oxidized A-type granites, correlated to Neoarchean Vila Jussara Suite. Also, it correlated to Neoarchean subalkaline magmatism in the northern area, occur two granitic stocks. They comprise (i) tonalite to granodiorite with geochemical signature similar to oxidized A-type granites and show affinity with Vila Jussara Suite; and (ii) monzogranites which show reduced A-type granites signature and could be compared to Planalto Suite. At northern of the study area was identified an association of mafic-enderbitic rocks which comprises intensely deformed and recrystallized hornblende norite, pyroxene-hornblende gabbros, pyroxeneix hornblende monzonite, hornblende gabbros, amphibolites and enderbites, which are represented in the geological map as a WNW-ESE small elongated body , and a semicircular body controlled by shear zones. The textures observed in these rocks indicate that recrystallization occurs under relatively high temperatures, 6000C or above, and those rocks show metamorphic features. The geochemical behavior of these rocks suggests that the hornblende-norite, hornblende-gabbros and amphibolites are tholeiitic subalkalines, whereas enderbites, pyroxene-hornblende gabbro and pyroxene-hornblende monzonite exhibit calcalkaline signature. The low La/Yb ratios for mafic rocks indicate low degree of fractionation, whereas the high La/Yb ratios for enderbites reveal significant fractionation of HREE during formation and differentiation of its magmas, and the concavity of HREE pattern indicates probably influence of amphibole fractionation during its evolution. In the central and northcentral of area was recognized biotite-monzogranites with peraluminous and calc-alkaline signature and distinct REE patterns, which allowed us to distinguish two groups. The first shows higher REE enrichment, weak enrichment in LREE relative to HREE, and exhibit moderate negative Eu anomalies, indicating no significant fractionation of phases enriched in HREE and show possibly affinity with Bom Jesus Granite from Canaã dos Carajás area. The second group shows a sharp fractionation of HREE relative to LREE, with discrete or absent Eu anomalies, and concave HREE patterns indicating that amphibole was important phase during the fractionation of these rocks, like Serra Dourada and Cruzadão granites, also located in the Canaã dos Carajás area. This comparison should be enhanced as soon as further geochemical and geochronological data are available in order to a correlation can be evaluated.
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Geoquímica, petrogênese e evolução estrutural dos granitóides arqueanos da região de Xinguara, SE do Cráton amazônico
(Universidade Federal do Pará, 2001-05-25) LEITE, Albano Antônio da Silva; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
The Xinguara region is situated in the northern sector of the Rio Maria Granite-Greenstone Terrain (RMGGT), southeastern Amazonian craton. The RMGGT is composed by greenstone belts and diversified granitoid plutons. Granitoids and gneisses, formeriy included indistinctly in the Xingu Complex, have been individualized in two new stratigraphic units: The Caracol tonalitic complex (CTc), which shows enclaves of the greenstone belts and the Água Fria trondhjemite (THaf). The Iatter is intrusive in the Sapucaia greenstone belt and in the CTc, and coeval with the Xinguara granite (Gxg). Some granodioritic bodies exposed in the Xinguara region are correlated with the Rio Maria granodiorite (GDrm). They are younger than the CTc and older than the THaf and Gxg. The dominant regional structures follow a WNW-ESE trend, observed in the south portion of the CTc and also in the comparatively younger granitoid plutons. The CTc preserves a N-S banding in its NW sector, but this structure is transposed to the WNW-ESE regional trend. The GDrm shows strongly flattened mafic enclaves, which defines a foliation; The THaf displays a magmatic banding; The Gxg pluton has an elongated shape; ali these structures follow the regional trend. The Gxg displays a weak foliation, subhorizontal at the center and dipping at high angles along the borders of the intrusion. The G1 axis of the regional stress during the intrusion of the granitoids was horizontal and trending N40E. The regional stress remained active during the submagmatic stage of the CTc evolution, as indicated by the presence of folds or boudins affecting its banding. It was responsible by the transposition to WNW-ESE of N-S structures. The stress field orientation was similar during the two phases of the Archean evolution of the region. This is suggested by the main submagmatic to subsolidus deformation structures in the GDrm, THaf, and Gxg. The changing trends of the CTc foliation suggest that the CTc was formed by domic plutons, intruded and sectionated by the younger granitic intrusions. Al-in amphibole geobarometer data suggest that the GDrm crystallized under a lithostatic pressure of —3 kbar, equivalent to a —10 km depth. The contact metamorphic effects of the Rio Maria granodiorite in the metabasaltic rocks of the Identidade greenstone belt are coherent with this data and suggest also that its emplacement was not diapiric-controlled. The variation in the intensity and orientation of the foliation in the Xinguara pluton and the deformation imprinted on its country rocks suggest its emplacement by bailooning. The emplacement of the THaf was probably controlled by diapiric processes. The CTc is a typical TTG, similar to those of the Archean trondhjemite series. Two different geochemical signatures have been identified in this granitoid on the basis of accentuated contrasts in LaN/YbN ratios. The GDrm is different of the TTG series. It follows the calc-alkaline trend and is similar to the Mg-rich granodiorites of the Sanukite Series. The THaf is geochemically similar to the CTc and by extension to the Archean TTG, but it is comparatively enriched in K2O. The Gxg is a high-K2O, strongly fractionated, calc-alkaline Archean leucogranite. Its REE pattern is indicative of a crustal origin. The dominant, high LaN/YbN ratio CTc group crystallized from a liquid probably originated from the partial melting of garnet amphibolites derived from 'normal' tholeiites. The latter should be similar in composition to the Archean metabasalts or to the metabasalts from the Identidade greenstone belt and the degree of partial fusion required would be, respectively, 25-30% and 10-15. On the other hand, the tonalites with Iow LaN/YbN ratios crystallized from a liquid derived from a garnet-free similar source. Nd isotopic data indicate a mantle source and a juvenile character for the tonalites of the first group. A tonalite sample of the second group and an enclave in the Gxg yielded negative ONd values and >3.2 Ga TDM ages. These data suggest that the tonalites of this group could derive from an older source with a longer crustal residence time. The THaf may have been generated by 5-10% partial melting of garnet amphibolites derived from metabasalts, chemically similar to the metabasalts from Identidade. The liquids of the Gxg were originated by variable degrees of partial melting of a source similar to the oldest TTG granitoids. The Archean geologic evolution of the Xinguara region occurs in two stages. The first starts in the interval of <2.95 to 2.91 Ga and is apparently similar to those of the Pilbara and Darwhar cratons. The second stage starts at 2.88 Ga and it is coincident with a sharp change in crustal behavior. At this time, the increasing thickening and stabilization of this Archean crustal segment, turned more effective the processes of plate subduction and convergence. In this tectonic context, the partial melting of an enriched mantie wedge would generate the parental magma of the GDrm and the partial fusion of garnet amphibolites derived from the subducted ocean crust would generate the THaf magma. Finally, the upward movement of the THaf and GDrm magmas would induce the melting of the TTGs in the lower crust, thus generating the granitic magmas of the Xinguara pluton.
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Granodiorito Rio Maria e rochas associadas de Ourilândia do Norte – Província Carajás: geologia e afinidades petrológicas
(Universidade Federal do Pará, 2015-07-22) SANTOS, Maria Nattania Sampaio dos; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The granitoids of sanukitoid affinity of the Ourilândia do Norte area, located near the Rio Maria-Carajás domain boundary, are associated with Rio Maria sanukitoid suite from the Mesoarchean age. In this area dioritic, quartz-monzodioritic, tonalitic and granodioritic rocks with variable proportions of amphibole and biotite were described. Contrary to what is observed in the sanukitoid rocks of the Rio Maria area, those of Ourilândia do Norte are constantly affected by deformational processes, relating to the installation of the Itacaiúnas Shear Zones. They exhibit pervasive foliation and microstructures developed under three dynamic recrystallization regimes: (1) Bulging recrystallization (300-400°C); (2) Subgrain rotation recrystallization (<500°C); (3) Grain boundary migration recrystallization (<600°C). Granitoids with sanukitoid affinities are magnesian and metaluminous and belong to medium to high potassium calc-alkaline series. They display non-collinear trends from (quartz) diorite toward granodiorite and exhibit a negative correlation for compatible elements (CaO, Fe2O3 t, MgO, TiO2, Zr, Ni, Cr and #Mg) and inverse behavior for incompatible ones (Ba, Sr), as well as Rb/Sr and Sr/Ba ratios. Moreover, they show amphibole, clinopyroxene and subordinate biotite and plagioclase fractionation. The clinopyroxene-bearing monzogranite shows trends parallel to those of sanukitoids and has a lower Sr/Ba ratio and #Mg content, due to its ferrous character, and probably does not belong to the sanukitoid series. The REE pattern of granodiorite shows a slight or absent Eu anomaly (Eu/Eu*=0.76-0.97) and moderate (La/Yb)N ratio, indicating garnet, amphibole or pyroxene fractionation. Tonalites are less depleted in HREE and have little Eu anomaly (Eu/Eu*=~0.95). Enclaves, (quartz) diorite and quartzmonzodiorite exhibit negative to positive Eu anomalies (Eu/Eu*=0.56-1.71) and a low (La/Yb)N ratio, whose horizontal pattern is similar to that of intermediate rocks from the Rio Maria area. Clinopyroxene-bearing monzogranite shows affinities for the tholeiitic series, following slightly different trends from granitoids, with a negative Eu anomaly (Eu/Eu*= 0.63-0.98) and (La/Yb)N slightly fractionated ratios. Negative Nb-Ta-Ti anomalies, associated with high (La/Yb)N and Y/Nb ratios suggest that these rocks were generated in a subduction zone from a depleted source mantle which was contaminated by fluids or melt. Analysis of the metassomatic agent nature revealed that less evolved rocks were contaminated by fluids, while granodiorites and related rocks were contaminated by melt, whose composition is similar to that of tonalite-trondhjemite-granodiorite (TTG). Enclaves, (quartz) diorite and clinopyroxene-bearing monzogranite were produced by relatively low pressures (La/Yb<1.0 GPa) and depths (<33.6 Km), with little or no residual garnet, while the other granitoids could ix have been generated under superior geothermal conditions (La/Yb=1.0-1.5 GPa; 33.6-50.5 Km) with variable proportions of residual garnet. Furthermore, these granitoids started to crystallize at depths between 30.3 and 20.2 Km and ended between 10.1 and 6.7 Km. Ourilândia do Norte sanukitoid rocks and the other analoguous intrusions of the Carajás Province show geochemical and petrogenetic affinities with high-SiO2 adakites and low-TiO2 sanukitoids. They may have originated through a one-stage process, by direct hybridization between the mantle and TTG-melt. Nevertheless, the modeling performed on Rio Maria and Karelian sanukitoids indicates that they were produced by a two-stage process, from meltmetasomatized peridotite remelting.
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Greisens e Epi-sienitos potássicos associados ao granito água boa, Pitanga (AM): um estudo dos processos hidrotermais geradores de mineralizações estaníferas
(Universidade Federal do Pará, 2002-10-23) BORGES, Régis Munhoz Krás; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
Three stanniferous greisen types were characterized in the western border of Água Boa pluton, Pitinga mine (AM), associated with the rapakivi granite facies: greisen 1 (Gsl), composed mainly by quartz, topaz, brown siderophyllite and sphalerite; greisen 2 (Gs2), composed essentially by quartz, phengite and chlorite; greisen 3 (Gs3), composed of quartz, fluorite and phengite, with minor green siderophyllite. Besides these rocks, a potassic episyenite (EpSK) was identified associated with the Gs2. In spite of the compositional and petrographic differences, all of these hydrothermal rocks derived from a same protholith, a hornblende biotite aikali feldspar granite to syenogranite. The Gsl shows an inner mineralogical zoning defined by topaz or siderophyllite predominance. Along drill cores, the siderophyllite-rich zone occurs near the contact with the greisenized grafite and the topaz-rich zone is situated far from the grafite contact. The brown siderophyllite displays moderated Al contents, and its compositional changes can be explained by Fe+2 substitution for A1+3 and Li in octahedral sites, with a coupled Al+3 substitution for Si+4 in tetrahedral sites. The mineralogical zones in the Gs2 are physicaliy separated in leveis with phengite or chlorite predominance. The mica of Gs2 is a phengite, whose chemical variation is due to substitution of viAl for Fe+2, coupled with Si+4 enrichment. The calculated Li contents in phengites are lesser than those estimated in siderophyllite. The green siderophyllite from Gs3 is VIAl richer and F poorer than Gs1 brown siderophyllite, and the phengite displays two compositional types: an early Fe+2-poor aluminous phengite and a later Fe+2- F-rich one whose chemical variation is similar to that of Gs2 phengite. The chlorite from the three greisen is a Fe-rich daphnite, and its compositional range is due to VIAl substitution for R+2 cations, coupled with Si+2 enrichment. The aluminous chlorite displays higher temperature formation than ferrous one, according to the geothermeter proposed in the literature. The Pitinga greisens were formed by different processes of interaction among three main fluids: (1) low salinity, F-rich, aquo-carbonic fluid, with initial temperatures between 400° -350°C, present during Gsl and Gs3 formation; (2) low salinity aqueous fluid, with a temperature around 300°C, which during a progressive salinity increasing process, originates a moderate to high salinity residual fluid, with temperatures between 200° - 100°C, present during the Gs2 formation and silicification stage of EpSK; (3) low salinity aqueous fluid, with temperatures between 200° - 150°C, which interplayed with the others two fluids in differents grades, contributing to the formation of ali the hydrothermal rocks. The first two fluids has seemingly an orthomagmatic origin while the latter has a surface characteristic (meteoric water?). Moreover, the data suggests that the fluid responsible by the initial stage of the episyenitization process was not registered in the studied samples. These fluids were trapped in pressure conditions around 1 Kbar, representing high crustal levels conditions, similar to that of the stanniferous granites from Pitinga. Both episyenitization and greisenization processes occurred without volume changes in the granitic protholith, and the density differences of the altered rocks were caused by the mass variations along the alteration processes. The greisenization process caused a extensive loss of Na2O and K2O, while SiO2 showed a immobile behaviour in Gsl but was parcially removed in Gs2. The Al2O3 was depleted during the Gs2 formation but added in Gsl. The Fe2O3 (Fe total), Sn, S, volatiles LOl and F were the responsible by the mass increase at greisenization. In the Gsl, the chemical changes in the fiuids were caused by F activity decrease and fO2 increase during cooling. These changes also originated the differentiation between the ZT, in the inner portions of the fratures/conducts, and the ZS, nearest to surrounding gravite. The Gs3 was formed in more oxidizing conditions by F-poorer fiuids than those trapped in the ZS. The dissolution cavities generated during the episyenitization process increased the permeability of the altered rocks, providing an increase of fluid/rock ratios in the EpSK and Gs2 sites. The interaction between aqueous fluid and EpSK feldspar, during the Gs2 formation, caused a continuous salinity increase. The ZF was formed in the early stages of this interaction, at higher temperatures, while the ZC was originated by the more cold and saline, residual fluid. The latter was also trapped in the quartz filling cavities in the EpSK during the later silicification stage. In this way, the greisens and the potassic episyenites were generated from interactions among, at least, three fluids of seemingly independent origin, from a same protholith, in shallow crust conditions. The fO2, F activity and salinity variations, during the hydrothermal system cooling, and the contrast in fluid/rock ratios caused by permeability differences, were very important factors to greisen differentiation. These factors controlled greatly the fluids compositional changes, and caused the cassiterite and sulphides precipitation in the greisens and the Sn- S-enrichment during later greisenization of EpSK.
Acesso aberto (Open Access)
Mineralogia e petrologia do complexo ultramáfico e alcalino de Santa Fé - GO
(Universidade Federal do Pará, 1978) SOUSA, Ana Maria Soares de; GIRARDI, Vicente Antonio Vitório; http://lattes.cnpq.br/6876269679513816
Acesso aberto (Open Access)
Mineralogia, geoquímica e minerais pesados do perfil laterito-bauxítico com cobertura e sua relação com o grupo Itapecuru: lavra piloto ciríaco (Rondon do Pará)
(Universidade Federal do Pará, 2015-07-11) PANTOJA, Heliana Mendes; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
The lateritic-bauxite profile studied in Rondon do Pará is part of the Paragominas Bauxite Province, the most important of the Brazil that hosts world-class deposits of considerable economic value. The deposit comprises six horizons: bauxitic clay at the bottom, massive bauxite, massive iron-aluminous crust, iron-aluminous crust dismantled, ferruginous spheroliths and a clay cover equivalent to the "argilas de Belterra" at the top. The sedimentary rocks of the Itapecuru Group are the probable source of the lateritic-bauxite profile and include weathered siltstone and claystone. The mineralogical composition of the three studied units (Itapecuru Group rocks, lateritic-bauxite profile and clay cover) is similar and consist to kaolinite, quartz, hematite, goethite and gibbsite, accessory minerals include anatase and heavy minerals (zircon, tourmaline, rutile, staurolite and opaque). The units differ mainly in this content variation and the absence of gibbsite and goethite in the rocks of Itapecuru Group. The chemical composition of the three units shows that Al2O3, SiO2, Fe2O3, TiO2 and LOI are the most abundant constituents, related to the major minerals. Trace elements content in the three units are heterogeneous with V, Cr, Ga, Zr, Hf and Th showing concentrations above the crustal average, these elements display good correlation with iron oxy-hydroxides. When normalized to chondrites, the three units differ by positive Ce anomaly in the Itapecuru Group rocks, but are similar in negative Eu anomaly, the depletion of LREE and enrichment of HREE. The data obtained show clear affinities between the three units, suggesting that the sediments of the Itapecuru Group are similar to those of the bedrock of lateritic-bauxite profile while their respective cover demonstrates strong relationship with the crusts and spheroliths. The structure of the lateritic-bauxite profile together with mineralogical and chemical data allow to correlate the Rondon do Pará lateritic-bauxite profile with the deposits of Paragominas and Juruti.
Acesso aberto (Open Access)
Modelos de evolução e colocação dos grantitos paleoproterozóicos da Suíte Jamon, SE do Cráton Amazônico
(Universidade Federal do Pará, 2006-10-27) OLIVEIRA, Davis Carvalho de; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
The 1.88 Ga, anorogenic, A-type Jamon suite and associated dikes intruded 2.97 – 2.86 Ga-old Archean granitoids of the Rio Maria Granite-Greenstone Terrane which lies to the south of Serra dos Carajás, in the southeastern domain of the Amazon Craton, northern Brazil. Petrographic and geochemical aspects associated with magnetic susceptibility and gamma-ray spectrometry data showed that the Redenção and the northern part of Bannach plutons are normally zoned, with mingling relationships that indicate multiple magma injections in their construction. Both were formed by two magmatic pulses: (1) a first magma pulse which fractionated in situ after shallow crustal emplacement and generated a series of coarse, evengrained monzogranites with variable modal proportions of biotite and hornblende; (2) a second, slightly younger magma pulse, localised in the center of both plutons, and composed of a more evolved liquid from which even-grained leucogranites were derived. Seriated and porphyritic biotite monzogranite facies intruded the coarse (hornblende)-biotite monzogranites and formed anellar structures within the Redenção pluton. The magmatic zoning is marked by a systematic decrease in mafic mineral modal content, plagioclase/potassium feldspar and amphibole/biotite ratios, and anorthite content of plagioclase. TiO2, MgO, FeOt, CaO, P2O5, Ba, Sr, and Zr decreased, and SiO2, K2O, and Rb increased in the same fashion. Magmatic differentiation was controlled by fractionation of early crystallized phases, including amphibole±clinopyroxene, andesine to calcic oligoclase, ilmenite, magnetite, apatite, and zircon. The Jamon suite is subalkaline, metaluminous to mildly peraluminous, ferroan alkali-calcic, and displays geochemical affinities with within-plate A-type granites. The ubiquitous occurrence of magnetite and titanite as well as high magnetic susceptibility values demonstrate that granites of the Jamon suite are oxidized in character. Oxidized A-type granites have high FeOt/(FeOt+MgO), TiO2/MgO, and K2O/Na2O ratios and low CaO and Al2O3 compared to calc-alkaline granites. The oxidized character of the Jamon suite makes it more akin to the USA Mesoproterozoic magnetiteseries A-Ttype granites but differs from the reduced rapakivi granites of the Fennoscandian Shield, and Serra dos Carajás and Velho Guilherme suites of the Carajás province, probably because of different magmatic sources. The Jamon suite probably crystallized near or slightly above the nickel-nickel oxide (NNO) buffer and an Archean sanukitoid biotite-hornblende quartz diorite source was proposed for the oxidized Jamon magmas. Gravity modelling indicates that the Redenção and Bannach plutons are sheeted-like composite laccolithic intrusions, ~6 km and ~2 km thick, respectively. These plutons follow the general power law for laccolith dimensions and are similar in this respect to classical rapakivi granite plutons. Gravity data suggest that the growth of the northern part of the Bannach pluton was the result of the amalgamation of smaller sheeted-like plutons which successively intruded in sequence from northwest to southeast. Jamon suite plutons were emplaced in an extensional tectonic setting with the principal stress oriented approximately along NNE-SSW to ENE-WSW, as indicated by the occurrence of diabase and granite porphyry dike swarms, orientated WNWESE to NNW-SSE and coeval with the Jamon suite. The 1.88 Ga A-type granite plutons and stocks of Carajás are disposed along a belt defined by the general trend of the dike swarms. The inferred tabular geometry of the studied plutons can be explained by magma transport via dikes and it is supported the high contrast of viscosity between the granites and their Archean country rocks. Mechanisms responsible for emplacement of granitic plutons, and in particular of anorogenic A-type plutons, are still debated. A magnetic fabric study derived from anisotropy of magnetic susceptibility (AMS) measurements was applied to the Redenção pluton in order to understand its emplacement history. High magnetic susceptibilities (K from 1 x 10-3 SI to 54 x 10- 3 SI) indicated that magnetic fabrics are primarily carried by ferromagnetic minerals (magnetite). Low P' values and absence of intracrystalline deformation features indicated that the magnetic fabric is of magmatic origin. The magnetic fabric is well organized and characterized by concentric steep foliations associated with moderately to gently plunging lineations. The lack of a well-defined unidirectional linear fabric at pluton scale suggests the reduced or null influence of regional stresses during granite emplacement. Three stages are proposed for construction of the Redenção pluton, which reconcile the tabular shape of the intrusion with the occurrence of steep magnetic foliations: (1) ascent of magmas in vertical, northwest-striking feeder dikes and accommodation by translation along east-west-striking regional foliation planes; (2) switch from upward flow to lateral spread of magma with space for injection of successive magma pulses created by floor subsidence; and (3) in situ inflation of the magma chamber in response to the central intrusion of late facies, accompanied by evacuation of resident magmas through ring fractures.
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Morfologia e assinatura geoquímica de zircão da suíte sanukitoide Rio Maria, Província Carajás: implicações petrológicas
(Universidade Federal do Pará, 2016-11-29) COSTA, Hévila de Nazare Silva da; LAMARÃO, Claudio Nery; http://lattes.cnpq.br/6973820663339281
This research involved the morphological and compositional study of zircons from granodioritic rocks of Sanukitoide Rio Maria suite, Carajás Province. For this study were chosen five regions inserted in this Province, namely: Rio Maria and Bannach, type areas of the Rio Maria Sanukitoide rocks; Ourilândia do Norte, containing correlated granodioritic rocks to sanukitoids Rio Maria; São Felix do Xingu, where there are still poorly studied granodiorite rocks similar to sanukitoides, besides Trairão Granodiorite, situated in the Pau D'Arco region, belonging to the Guarantã suite and geochemically distinct from sanukitoide rocks. Zircon crystals were studied with the aid of secondary electron images (ES), cathodoluminescence (CL), semiquantitative analysis by spectroscopic energy dispersive (EDS) using a scanning electron microscope (SEM), aiming to define morphological features and characteristics geochemical signatures for zircons from each group of rock, compare the typological aspects between them and reaffirm the importance of zircon in petrological studies and SEM-CL-EDS methodology as a support tool for these purposes. The morphological study was conducted in zircons from two groups of rock. In the first one, made up of zircons from Rio Maria Sanukitoide Suite, were selected one hundred ten zircons and in the second one, represented by zircons of Trairão Granodiorite, twenty nine crystals. Zircons from the first group have euhedral shapes, subordinately subhedral, well defined standard zoning, well-developed and preserved cores, thin luminescent edges, suggesting compositional change at the end of crystallization, and rare to moderate presence of F-apatite inclusions. The zircons of Trairão Granodiorite showed euhedral the subhedral forms and well defined oscillatory zoning. The presence of F-apatite inclusions is recurring in this sample, both at the cores or at the edges of the crystals, truncating or taking place in parallel with the growth zones, suggesting simultaneous crystallization of both minerals. For the typological study were selected two groups of zircons. The first, made up of zircons of the Rio Maria sanukitoides, falls mostly within S18 type, with rare occurrences in P4 type. The second, represented by zircons of the Guarantã Granodiorite, correlates with S3 and S8 types. Semiquantitative ESD analysis performed in zircons from the five studied regions were compared and interpreted in specific geochemical diagrams. Zircons of Rio Maria and Ourilândia do Norte sanukitoides showed the lowest Nb contents (1.0-1.8%), followed by the zircons of Bannach and Xingu regions (1.8-2.5%) and Trairão Granodiorite (dominantly between 2.2 to 3.3%). Zircons from Rio Maria and Ourilândia do Norte sanukitoides showed higher Zr/Nb ratios, between 30 and 50, and zircons from Trairão Granodiorite the lower ratios, predominantly between 17 and 23. Zircons from Bannach and Xingu sanukitoides presented intermediate Zr/Nb ratios, between 23 and 32. The Sr versus Zr/Nb diagram shows a well defined negative trend, with zircons of Trairão Granodiorite more enriched in Sr (1.5 to 2.4%) and zircons from the Rio Maria and Ourilândia of Norte sanukitoides most depleted (0.6 to 1.6%), with partial overlap between them. Zircons from Bannach and Xingu sanukitoides showed intermediate Sr content (1.2 to 1.7%) and Zr/Nb (23 and 32) and plotted between the previous in the diagram. The study showed morphological, typological and compositional differences between the zircons of sanukitoides rocks of southeastern Para, and between these and the zircons of the Trairão Granodiorite. According to Pupin (1980) scheme, these differences allowed to frame the zircons of the sanukitoid rocks and the Trairão Granodiorite into two distinct groups, suggesting its crystallization occurred in different environments and temperatures.

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