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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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 geológica pré-cambriana e aspectos da metalogênese do ouro do cráton São Luís e do Cinturão Gurupi, NE-Pará/ NW-Maranhão, Brasil
(Universidade Federal do Pará, 2004-07-06) KLEIN, Evandro Luiz; GIRET, André; HARRIS, Christopher; MOURA, Candido Augusto Veloso; http://lattes.cnpq.br/1035254156384979
In the Gurupi region, located at the border between the Pará and Maranhão states in northern Brazil, igneous and metamorphic rocks crop out as part of the Parnaíba Structural Province. Early geochronological studies, based on the Rb-Sr and K-Ar methods have shown two geochronological domains. The rocks that crop out towards the Atlantic margin showed a Paleoproterozoic signature, around 2000 Ma, whereas the rocks that crop out towards the inner portions of the continent showed a Neoproterozoic signature, especially between 800 and 500 Ma. These domains have been then defined as the São Luís Craton and Gurupi Belt, respectively. Several lithostratigraphic propositions have been developed throughout more than two decades. However, these propositions always lack robust geochronological support. Geotectonic models discussed a one- or two-phase evolution for the Gurupi Belt, also lacking robust geochronological and isotopic data to consubstantiate the interpretations. Furthermore, among the several gold deposits that occur in both the cratonic and belt areas, only a few have geological and genetic information. These subjects are addressed in more or less depth by this thesis. New propositions for the regional lithostratigraphy and geological evolution have been achieved in this work by revaluating the available geological, geochemical, geochronological and isotopic dataset, as well as by adding new geochronological data on zircon (Pb-evaporation, U-Pb ID-TIMS, and LAM-ICP-MS) for most of the igneous and orthometamorphic rocks in the region. Whole rock Nd isotope data have also been obtained, allowing the discussion of crustal accretion and reworking. The results show a rather complex geological evolution with intensive and extensive crustal growth between 2.24-2.15 Ga and crustal reworking, involving melting, migmatization, metamorphism, and deformation around 2.10 Ga. The following results have been obtained for the São Luís Craton: Aurizona Group, metavolcano-sedimentary sequence, maximum age of 2241 Ma (juvenile) that possibly evolved until c.a. 2200 Ma; Tromaí Intrusive Suite, calc-alkaline, metaluminous tonalites of oceanic island arc, 2168 Ma (juvenile); Areal Granite, calc-alkaline, weakly peraluminous, 2150 Ma (mixing of juvenile and arc materials). In the Gurupi Belt, the following results have been obtained: Igarapé Grande Metatonalite, small and localized granoblastic tonalite, 2594 Ma; Itapeva Complex, weakly migmatized tonalitic orthogneiss, 2167 Ma (mostly juvenile); Chega Tudo Formation, metavolcano-sedimentary sequence (back-arc basin?), 2150-2160 Ma; Maria Suprema Granite, syntectonic, peraluminous muscovite-bearing granite, 2100 Ma (similar to other peraluminous granitoids in the Gurupi Belt). The Gurupi Group is tentatively placed in the Paleoproterozoic (>2160 Ma), but this must still be proved. The above data are interpreted on a plate tectonics basis, as follows. An oceanic basin is open at ca. 2260 Ma and is followed by the onset of subduction, formation of island arcs and voluminous calc-alkaline magmatism in oceanic settings, and concomitant reworking of the arcs between 2170-2150 Ma. This set of oceanic terranes has been accreted (soft-collision) onto an Archean continental margin to southwest (Archean part of the Amazonian Craton or a present day concealed cratonic nuclei). The collision provoked the metamorphism, deformation, and partial melting of the newly formed Paleoproterozoic crust and of part of the Archean bloc, or their erosive detritus, migmatization, and emplacement of peraluminous granitoids at 2100-2080 Ma. The region has been the locus of a second event in the Neoproterozoic. A continental rift developed in the bloc that was assembled in the Paleoproterozoic, as attested by the intrusion of a nepheline syenite (Boca Nova) at 732 Ma. Sedimentary rocks that filled this rift (Marajupema Formation) have detrital zircon crystals that show the youngest ages around 1100 Ma. The rift evolved probably to an oceanic basin, as suggested by the widespread occurrence of detrital zircons with ages around 550 Ma in small sedimentary basins that have been filled with immature sediments. The precise time of orogenesis climax that followed basin closure, with mass transport from SSW to NNE and accompanying metamorphism, is not yet constrained. Equivocal geochronological information point to 650-520 Ma (zircon of the nepheline syenite, Rb-Sr and KAr ages in minerals). The metallogeny of selected gold deposits occurring in both the São Luís Craton and the Gurupi Belt is addressed using varied information, such as geology, chlorite chemistry, fluid inclusion geochemistry, and stable (O, H, C, S) and radiogenic (Pb) isotopes. Structural and textural relationships, and Pb isotope data indicate a post metamorphic peak and late- to posttectonic timing for the gold mineralization with respect to the Paleoproterozoic events (post 2080 Ma). At a regional scale, the deposits show a similar signature characterized by formation temperatures between 280° and 380°C; pressures of 2-3 kbars; low-salinity (5 mass % NaCl equiv), reduced and moderately dense aqueous-carbonic (CO2 <20 mol%, traces of CH4 and N2), showing strong evidence for phase separation. Stable isotope studies suggest distinct sources for fluids and solutes. The carbonate, graphite, and fluid inclusion carbon comes from two sources: a depleted organic source, and an unknown source that may be magmatic, metamorphic or mantlederived (or both). Sulfide sulfur derived directly from magmas or from the dissolution of magmatic sulfides. Combined oxygen and hydrogen isotopes attest a metamorphic source for the fluids. Therefore, dehydration and decarbonization reactions during the metamorphism of the Paleoproterozoic metavolcano-sedimentary sequences appear to have produced the mineralizing fluids. Gold was transported as a reduced sulfur complex, such as the Au(HS)2 - and precipitated in response to the breakdown of this complex due to phase separation and fluid-rock interactions. The geological and genetic constraints are consistent with the orogenic gold model, found in metamorphic belts of all ages. As a whole the results of this study have implications for the understanding of the Paleoproterozoic and Neoproterozoic orogenies that built up the South American Platform and for the assembly and break-up of the Atlantica, Rodinia, and West-Gondwana supercontinents. The geological scenario outlined here for the Paleoproterozoic shows good correlations with those found especially in the southeastern Guyana Shield and in the southern portion of the West- African Craton. For the Neoproterozoic, the available information is still insufficient to draw major correlations.
Acesso aberto (Open Access)
Geocronologia em zircão, monazita e granada e isótopos de Nd das associações litológicas da porção oeste do domínio Bacajá: evolução crustal da porção meridional da província Maroni-Itacaiúnas - sudeste do Cráton Amazônico
(Universidade Federal do Pará, 2006-11-16) VASQUEZ, Marcelo Lacerda; MACAMBIRA, Moacir José Buenano; http://lattes.cnpq.br/8489178778254136
The Bacajá domain is located in the southeastern Amazonian craton and represents the southern part of the Maroni-Itacaiúnas province, which comprises Paleoproterozoic orogens and Archean blocks reworked during the Transamazonian cycle (2.2–1.95 Ga). This domain is composed of granitoids, charnockitic and supracrustal rocks, orthogneisses, migmatites, metaigneous granulites and high-grade metasedimentary rocks. The previous geochronological data denote reworking of Archean crust and formation of juvenile crust during the Transamazonian cycle. The present study was based on field work, petrography, isotope geochemistry and geochronology in order to identify the igneous and high-grade metamorphic events in the western part of the Bacajá domain and to discuss its crustal evolution. The previous geochronological data, plus new data on zircon (U-Pb SHRIMP and Pbevaporation) and Nd isotope data for the igneous and meta-igneous rocks of the lithologic associations from the study area allowed the identification and dating of magmatic events from Neoarchean to Orosirian times, with a climax of crust formation during the Rhyacian. The 2.67- 2.44 Ga orthogneisses and 2.45 Ga metavolcanoclastic rock remnants are related to the first event of crust formation in the western Bacajá domain marked by an accretion at ca. 2.7 Ga and contamination by Mesoarchean crust (ca. 3.0 Ga). A second event of accretion at ca. 2.5 Ga and reworking of Mesoarchean crust were identified in 2.36 Ga metavolcanic rocks and associated 2.34 Ga granitoids, respectively. They are probably related to the amalgamation of a late Siderian island arc to an Archean microcontinent. The 2.21-2.18 Ga granitoids with Neoarchean crustal sources (ca. 2.8 Ga) and 2.16-2.13 Ga granitoids formed by mixture of a 2.3 Ga juvenile component with Archean crustal sources are related to Rhyacian magmatic arcs that collided against an Archean-Siderian continent. This collision was marked by the formation of 2.10 Ga granitoids (syncollisional rocks ?), probably originated from sources related to late magmatic arc rocks, and of charnockitic rocks and granitoids of 2.09-2.07 Ga (post-collisional rocks) formed respectively by mixture of Ryacian crustal sources and the 2.3 Ga juvenile component and by melting of Archean crust (3.0-2.7 Ga). There are Orosirian magmatic events identified in 1.99 Ga granitoids, whose correlation with the Transamazonian cycle is controversial, and by the extensional magmatism of ca. 1.88 Ga. Both events have Neoarchean crustal sources (ca. 2.8 Ga), probably derived from the Bacajá domain. The high-grade metamorphic events and associated anatexis were identified in the metaigneous and metasedimentary rocks from the western Bacajá domain. However, the petrologic and geochronological studies focused only on the high-grade metasedimentary rocks. These rocks have dominantly Archean detrital sources (3.1-2.5 Ga) and were affected by Rhyacian metamorphic events preliminary constrained by Sm-Nd whole rock-garnet isochrones (2208- 2025 Ma), but there is little evidence suggesting the existence of a high-grade metamorphic event at 2.3 Ga, that could be related to the collage of the late Siderian island arc. High-grade Transamazonian metamorphism commenced with a 2147-2123 Ma migmatization event that took place under upper amphibolite facies P-T conditions and was preserved in zircon overgrowths and in the cores of monazite grains. This event could be related to the collision of the early Rhyacian magmatic arc against to a Neoarchean-late Siderian continent. An anatectic event at 2109 Ma was recorded on unzoned rims of zircon crystals, which is probably it related to the continental collision at 2.1 Ga that has been identified in the Transamazonian orogens of the French Guiana shield. Despite the formation of synchronous granitoids and charnockitic rocks during this collision, in the studied metapelites it was a modest anatexis. After that, a low pressure granulite facies metamorphism (4-6 kbar / 700-800 ºC) at ca. 2070 Ma was registered on monazite and zircon grains, followed by a possible Pb-loss event at 2057 Ma. The existence of coeval quartz diorite and charnockitic intrusions suggests underplating of mafic magma and crustal thinning during the post-collisional period. The igneous and metamorphic events of the western Bacajá domain are analogue to those identified in other Transamazonian domains of the Amazonian craton and South America. In global scale, the 2.1 Ga collage has been correlated to the collision of the paleoplates of eastern South America and western Africa that triggered the formation of a Paleoproterozoic supercontinent.
Acesso aberto (Open Access)
Geoquímica multi-elementar de crostas e solos lateríticos da Amazônia Oriental
(Universidade Federal do Pará, 1994-12-16) ARAÚJO, Eric Santos; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
This work intention is to stand out a sistematic study on the chemical elements dispersion in soils and duricrust, developed over, diversified geological environments lithotypes, under humid tropical climate in the Amazon region-. Two target areas were chosen for soil sampling( Serra dos Carajás-N-5 and Serra do Tiracambu TN-6); the former, a gibbsite rich latosoil, is situated in the southwest part of Pára State; the latter, has a predominartee- of kaolinite and iron oxi-hydroxides overling a bauxite layer, situated in the western border of Maranhão State. Two other areas were selected for duricrust studies, Pirocaua iron-phosphate crust, surrounded by latosoil ( NW of Maranhão State) and Serra dos Carajás target N-1 feruginous crust. The methodology assumed was the same for all targets for both soil and duricrust, as follow: a - sampling grid of 200x200m; b - Three parts separation of soil samples (bulk,<200-14 and -80-F200- mesh- )-for duricrusts were only considered bulk samples; - X-ray difratometric analysis were carried out to determine mineralogical composition and atomic absortion for determination of Ni,Co,Cr,Cr,Mn,V,As and Bi and, Au, through fire assay; d X-ray fluorescence analysis were taken for SiO2,Fe2O3,Al2O3,TiO2,Ba,Y,Nb,Zr,Ga and Sc; PGE (Pt,Pd,Rh) and REE analysis were obtained by aplicai emission spectrography after pre concentration and ICP, respectively. Mineralogical and chemical data were processed in order to obtain basic statistical parameters by using compatible PC-IBMIXT through Geoquant System CPRM 3.1 version, as well as some other complementary softwares CONVERT and QPRO) both in the statistical studies and graphic data display, besides CLUSTER R MOD and Q MOD analysis. Target TN-6 X-ray difratometry soil samples analysis showed a mineralogical homogeneous character as predominantly composed by kaolinite,A1-goethite and anatase. This homogeneity is also present in bulk sample chemical composition and in the analized fractions as well,revealing a distribution of three main geochemical association-SiO2-Al2O3-Cu-Mn-Sr; Fe2O3-V-Cu-Ba-Cr-As-Sc-REE and TiO2-Y-Nb-Zr-Ga-Sc-REE as a reflect of kaolinite, iron oxi-hydroxide and anatase,respectively. On the other hand target N-5 latosoils are made out by gibbsite followed by goethite-hematite and in minor content, kaolinite and anatase. Although this target, from the mineralogical point of view, does not present much difference from the TN-6 except for the presence or gibbsite, it outstands the association of TiO2- Al2O3-Ga-Zr-Sc-Sr as well as Fe2O3-Mn-V-Cr-Sc-As. The former association representing gibbsite and anatase, besides being more consisterrt, surrounds the Fe2O3 association wich in turn reflect iron oxi-hydroxides and, indirectly, the contribution of basic rocks in the latosoils origin. Regarding target N-1duricrust, which presents differents textures (stratified,pisolitic and cavernous), the results obtained showed independently, similar concentration for Mn, Sr,Nb and Ga. Small difference characterize the cavernous duricrust in the gibbsite content and the predominantly presence of Au and Pt. In target N-1, as a whole, the most significant geochemical association was defined by Al2O3-TiO2-Cr-V-Sr-Nb-Zr-Ga-Sc-As. Low concentration of trace elements in this association reflects its origin from sedimentary nature Fe-Mn silicate deprived rocks, with low mafic/ultramafic contribution correlation matrix and groupment analysis in the Pirocaua target stablished two great geochemical associations with equal importance for soils and duricrust. The first, Fe2O3-V-Ga-Ni-Cu-Cr-As, indicates iron minerais, chiefly goethite and hematite, while the second, P2O5-Al2O3-(TiO2)-Sr-Y-Zr-REE reflects the crandallite-goyazite group of phosphates. The iron association is more frequent, occuping great extension of the plateau, not discerning soils or duricrust. So does the Au disperssion which presents indistinctly qualified values for 13 samples averaging 0.2 ppm and 1.01 ppm as maximum value. Arsenic concentratiton achieved an average of 188 ppm in duricrusts and 273 ppm in soils to which are associated the presence of tourmaline (dravite) in soil derived from hydrothermal zones noticiable in some outcrops fractures. Regarding PGE,qualified values for PT ( 0.1 to 0.4ppm) are directly associated to high concentration of Cr ( 1235 ppm in duricrust) and high values of P2O5 ( 11.85% soil to 15.05%-duricrust), this geochemical landscape is an evidence a basic composition vulcanosedimentary bedrock, rich in phosphates for the Serra do Pirocaua. The studies carried out were important in characterizing soils and duricrusts under a geological, mineralogical and chemical pooints of view, considering that, in both sample categories a surface sampling reflects, till certain extent and accuracy, trough geochemical association, the bedrock nature from which these covers had derived, as observed in the Pirocaua and N-5 targets the contribution of basic rocks as well as in the TN-6 and N-1 sedimentary rocks influence. This fact shows an importance to.consider.in the geochemical surveys, in characterizing concealed bedrock lithotypes by sampling their autochthonous covers, developed under humid tropical climate regions as the Amazon, taking into account that these rocks are not easily identified due the morphological condition involved and the consequent thicknes of the overburden. This is most outstanding inasmuch that the widrespread distribution frequency of those lithotypes in this region plus the scarcety of outcrops and their relationship to host environments of mineral deposits.

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