Teses em Geologia e Geoquímica (Doutorado) - PPGG/IG

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/6341

O Doutorado Acadêmico pertence ao Programa de Pós-Graduação em Geologia e Geoquímica (PPGG) do Instituto de Geociências (IG) da Universidade Federal do Pará (UFPA).

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A associação anortosito-mangerito-granito rapakivi (AMG) do Cinturão Guiana Central, Roraima, e suas encaixantes paleoproterozóicas: evolução estrutural, geocronologia e petrologia
(Universidade Federal do Pará, 2002-12-19) FRAGA, Lêda Maria; COSTA, João Batista Sena; http://lattes.cnpq.br/0141806217745286
The geological mapping on a scale of 1:250,000, of an area of approximately 22,500 km2 in the central region of the state of Roraima, combined with the petrographic and microtectonic study and new geochronological, lithochemical and isotopic data, allowed the characterization of an anorthosite-mangerite association -rapakivi granite (AMG), Mesoproterozoic and its Paleoproterozoic host. Orthogneisses, foliated granitoids and charnockite rock bodies from the Serra da Prata Intrusive Suite show Pb-Pb (zircon evaporation) ages around 1.94 Ga, also inferred for the associated norites and gabbronorites. The Paleoproterozoic igneous suites were placed syn-kinematically, during Deformational Event D1, with the evolution of petroweaves indicative of high temperatures, from 600º-650ºC. These features include recrystallized feldspars by subgrain rotation, recrystallized perthitic alkali feldspars and quartz with checkerboard subgrains and have been observed in syn-plutonic dykes that cut the early-kinematic D1 fabric in the host country. The NE-NW arrangement of the Paleoproterozoic bodies was controlled by the previous structure of this sector of the Central Guiana Belt (CGC). The orthogneisses and foliated granitoids comprise two distinct suites, with lithochemical characteristics of type A granitoids, probably related to different oxidation conditions at the source. The charnockite rocks show chemical characteristics approaching those described for C-type magmatism. Sm-Nd TDM model ages between 2.19 Ga and 2.05 Ga, with ƐNd(T) values ranging from +0.68 to +2 ,47 suggested sources of limited crustal residence. The age of the orogenic events in Roraima has not yet been properly clarified, however, despite the limited data, a post-collisional positioning is proposed for the Paleoproterozoic suites studied after the accretion of transamazonian magmatic arcs. The Paleoproterozoic units constitute the basement of the Mesoproterozoic igneous suites, which comprise the anorthosites of the Repartimento unit and associated gabbronorites, the rapakivi granitoids of the Mucajaí Intrusive Suite (SIM), and the fine, porphyritic charnockites, of punctual occurrence and uncertain geochronological positioning. In SIM, three granite facies were identified (fayalite-pyroxene-quartz-mangerites to syenites; hornblende-biotite-granites; and biotite-porphyritic granites) geochemically and petrographically very similar to rapakivi granites from classical areas of Finland. The presence of fayalite in the most primitive rocks of the SIM indicates conditions of low oxygen fugacity, observed in several rapakivi granite complexes. Fine charnockites show no cpm to SIM chemical correlation. The Mesoproterozoic suites are part of an AMG (Anortosito-Mangerito-Granito rapakivi) association placed in an anorogenic environment between 1.54 and 1.53Ga. Model ages Sm-Nd, from 2.07 Ga to 2.01 Ga with ƐNd(T) values ranging from -2.37 to -1.27 suggest, for the granitoids in the association, crustal sources separate from the mantle in the Paleoproterozoic , probably during the Transamazônico. Mylonitic features related to the D2 Deformational Event, registering conditions of moderate to low temperatures (400º-450ºC), in a brittle-ductile environment, locally obliterate the igneous textures of the Mesoproterozoic units, as well as the high temperature D1 petrowebs in the Paleoproterozoic basement. These features are especially well developed in some shear zones that show dextral transpressive kinematics. The D2 event aged around 1.26 Ga relates to the K'Mudku Deformational Episode. The main D2 mylonitic zones were reactivated in the Mesozoic at shallow crustal levels and brittle conditions, during the evolution of Graben Tacutu.
Acesso aberto (Open Access)
Biogeoquímica dos sedimentos lamosos e sua influência no padrão de distribuição da vegetação, no manguezal de Bragança, NE do Pará.
(Universidade Federal do Pará, 2009-10-30) CRUZ, Cleise Cordeiro da; LARA, Rubén José; http://lattes.cnpq.br/8695520453124286; 8695520453124286
The present study investigates the relationship between sediment-plant and biogeochemical processes involved in the development and spatial distribution of vegetation in the Bragança mangrove peninsula, exposed to macrotidal regime (spring range 4 m). Therefore, three transects were established at three different topographic levels of that peninsula being colonized by different patterns of vegetation: Transect 1 (T1) Transect 2 (T2) and herbaceous plateau (PHb). The vegetation in T1 is composed mainly by Rhizophora mangle and Avicennia germinans and it is situated in a semi-diurnal flooding regime forest. The transect T2 is less frequently flooded and is characterized by a stand of young Avicennia trees and herbaceous vegetation. In the highest part of this transect with low inundation frequency and high salt stress, the vegetation is dominated by shrubs of A. schaueriana coexisting with herbaceous vegetation of Sesuvium portulacastrum and Sporobolus virginicus. The PHB, localized in the zone with lowest inundation frequency is colonized mainly by tree species of A. schaueriana in the form of shrubs and S. portulacastrum and S. virginicus with sporadic presence of B. maritima. In these sites were performed measurements of the flooding frequency; floristic and fitossociologic inventory in mangrove forest and in the herbaceous halophyte vegetation. Also sediment cores (0-30 cm) and vegetation (leaves, stems and roots) were collected. The sediment samples were subjected to granulometrical, mineralogical and chemical (total sample) analyses, and determination of the humidity, organic matter and salinity as well as cation exchange capacity (CEC) besides determination of the total, inorganic, organic and bioavailable phosphorus. In the vegetation samples, chemical analysis of total phosphorus was performed. The variance analysis (ANOVA) One Way (Post Hoc Fisher's test) was applied to test the mean of the variables (humidity, salinity, organic matter, total-P, inorg.-P, org.-P and bioavailable-P. Discriminant analysis was used to measure the degree of influence of environmental variables (humidity, salinity, organic matter and total-P) in the discrimination of sites sampled. The correlation analysis of Pearson was used to evaluate the degree of interaction between discriminated variables with the hydrological conditions and forest structure data. Fine sediments (clay) in T1 and T2 suggest areas of slow deposition, while in the plateau high levels of sand suggest its formation on a paleodune with intense eolic reworking of sandy and tidal input of finer sediments. The main mineralogy of the sediments is composed of quartz (dominant in the sand and silt) and clay minerals: kaolinite and illite, other minerals of authigenic origin are pyrite, jarosite and vivianite and possibly smectite and k-feldspar. The main mineralogical and chemical composition of major and trace elements indicate the influence of sediments and soils of the Barreiras Formation on the genesis of sediments mangroves and marine influence in their chemical composition. In T1 (the more flooded sector), the dominant species is R. Mangle, while in T2 (less flooded zone) the Avicennia genus is predominant. In the herbaceous plateau the dominance of the S. portulacastrum species, is five times higher than that of S. virginicus, indicating that Sesuvium has greater ability to survive in environments with salt stress. The flooding gradient results in highly significant positive correlation with humidity. This trend is reflected in the tree height, volume and basal area correlated significantly with sediment phosphorus availability in T1 and CEC in T2. The results of Discriminant Analysis show that in T1 the humidity is the variable that most contributes in the discrimination of (Rhizophora and Mixed) forest of the Avicennia forest, while organic matter (OM) discriminated the Mixed forests and Rhizophora forests. In T2, the humidity, total-P and salinity are the variables that most contribute to the discrimination of sites in this transect. In the profiles, along the plain, the total-P and organic mater were the most important variables for discrimination of T1, T2 and PHb. The distribution of vegetation reflects different ecophysiological responses to environmental gradients. Therefore, the combination of organic matter, salinity, and phosphorus and, the high cation exchange capacity of sediments represent a significant role in the colonization of vegetation in the peninsula of Bragança.
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)
Fácies deposicionais, estratigrafia e aspectos estruturais da cobertura sedimentar paleoproterozoica na serra do Tepequém, Escudo das Guianas, Estado de Roraima
(Universidade Federal do Pará, 2010-12-09) FERNANDES FILHO, Lucindo Antunes; TRUCKENBRODT, Werner Hermann Walter; http://lattes.cnpq.br/5463384509941553; 5463384509941553
In the northern South America, occurs the largest continuous exposure of Paleoproterozoic sedimentary deposits related to the Roraima Supergroup, forming the Pacaraima Block with 73,000 km2. This siliciclastic succession of more than 2 km thick is inserted in the Guyana Shield, northern Amazon Craton, extending from in the border of Brazil, Venezuela, Guyana and Suriname. Near of the Pacaraima Block occur isolated mountains with little-known siliciclastic successions of the faciologic and stratigraphic point view, which does not allow a better correlation with the Roraima Supergroup and, consequently, hinders the paleogeographic and paleoenvironmental reconstitution of the Paleoproterozoic in this part of Amazonia. Outcrop-based stratigraphic and facies studies in the Serra do Tepequém and Uiramutã region, State of Roraima, northern Brazil, allowed redefined and redescribed the lower unit of Roraima Supergroup as Arai Group. The Arai Group of approximately 400 m thick overlies acid volcanic rocks of the Surumu Group, is covered by siliciclastic deposits of the Suapi Group and has been subdivided into two formations. The lower one, similar in both areas, generally consists of polymictic conglomerates, cross-bedded sandstones with microplacers of hematite, and subordinate mudstones interpreted as braided stream deposits. In contrast, the upper formation, in the Uiramutã region, is composed of silty fine-grained sandstones with medium-scale trough cross bedding and convolute lamination deposited in a more distal braided stream environment. This unit, in the Serra do Tepequém region, consists of fine to medium-grained cross-bedded sandstones with mudstones, sandstone/mudstone rhythmites and subordinate conglomerates and breccias interpreted as coastal, tide-influenced deposits. The top of the Arai Group is marked by an expressive unconformity covered with diamond-bearing conglomerates and pebbly sandstones of the basal Suapi Group, interpreted as braided stream deposits. This study confirms the previous interpretation of a big braided stream system migrating to southwest in the central part of the Guyana Shield. In addition it could be shown that the fluvial system in its distal part (Serra do Tepequém) was influenced by tidal processes. The stratigraphy of the Arai Group has established the basis for a regional correlation included deposits of isolated occurrences in the Guyana Shield and points to the presence of a large intracratonic Paleoproterozoic basin connected to the open sea. The structural framework of Serra do Tepequém indicates that major sinistral oblique, normal and reverse NE-SW fault zones bound domains whose bedding dips mainly towards SE and NW. Regional scale forced folds are represented by kilometer scale kink bands and chevron folds compatible with upper-to-middle crustal level. These findings differ from previous regional models based on folding under ductile conditions related to collisional tectonics and evidence the importance of Guiana Shield early basement structures, reactivated probably during the K'Mudku event (~ 1.2 Ga).
Acesso aberto (Open Access)
Geologia, geoquímica, geocronologia e petrogênese das suítes TTG e dos leucogranitos arqueanos do Terreno Granito-Greenstone de Rio Maria, sudeste do Cráton Amazônico
(Universidade Federal do Pará, 2010-03-23) ALMEIDA, José de Arimatéia Costa de; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675; 2158196443144675
TTG and granite suites are exposed in large domains of the Mesoarchean Rio Maria granitegreenstone terrane (RMGGT), southeastern Amazonian craton. Extensive field work in key areas of the RMGGT, integrated with petrographic, geochemical, and geochronological studies, the latter employing the Pb-Pb evaporation and U-Pb LA-ICP-MS on zircon techniques, indicates that the TTG magmatism record in the RMGGT can be divided into three episodes: (I) A first event at 2.96±0.2 Ga (the older rocks of the Arco Verde tonalite and the Mogno trondhjemite), (II) a second one at 2.93±0.1 Ga (Caracol tonalitic complex, Mariazinha tonalite, and the younger rocks of the Arco Verde tonalite), and (III) a restricted event at 2.86±0.1 Ga (Agua Fria trondhjemite). The new data demonstrate that the Mogno trondhjemite is significantly older than previously admitted, reveal the existence of a new TTG suite (Mariazinha tonalite) and indicate that the volume of TTG suites formed during the 2.87 event was limited. The Arco Verde tonalite yielded significant age variations (2.98 to 2.93 Ga) but domains with different ages could not be individualized so far. The tonalitic-trondhjemitic suites of the RMGGT derived from sources geochemically similar to the metabasalts of the Andorinhas supergroup, which were extracted from the mantle during the Mesoarchean (3.0 to 2.9 Ga) and had a short time of crustal residence. Three groups of TTG granitoids were distinguished in Rio Maria: 1) high-La/Yb group, with high Sr/Y and Nb/Ta ratios, derived from magmas generated at relatively high pressures (≥1.5 GPa) from sources leaving garnet and amphibole as residual phases; 2) medium-La/Yb group which magmas formed at intermediate pressure conditions (~1.0-1.5 GPa), but still in the garnet stability field; and 3) low-La/Yb group, with low Sr/Y and Nb/Ta ratios, crystallized from magmas generated at lower pressures (≤1.0 GPa), from an amphibolitic source that left plagioclase as a residual phase. These three geochemical groups do not have a direct correspondence with the three episodes of TTGs generation and a same TTG unit can be composed of rocks of different groups. The geochronological data indicate that the emplacement of the Archean granites of the RMGGT occurred during Mesoarchean (2.87 and 2.86 Ga) being coeval with the sanukitoid suite (~ 2.87 Ga) and post-dating the main timing of TTG suites formation (2.98 - 2.92 Ga). Three main types of Archean granites were distinguished in the RMGGT on the basis of petrographic and geochemical data: (1) Potassic leucogranites (Xinguara and Mata Surrão granites), that are composed dominantly of biotite-monzogranites with high SiO2, K2O, and Rb contents and fractionated REE patterns with moderate to pronounced negative Eu anomalies. These granites are similar to the low-Ca granites of the Yilgarn craton and to the CA2 Archean granites. Their magmas resulted from the partial melting of sources similar to the older TTG suites of the RMGGT; (2) Amphibole-biotite monzogranites (Rancho de Deus granite) generated by fractional crystallization and differentiation of sanukitoid magmas; (3) leucogranodiorite-granite suites (Guarantã suite and Grotão granodiorite), which are Ba- and Sr-rich rocks with strongly fractionated REE patterns without significant Eu anomalies. These granites have affinity with the high-Ca granites of the Yilgarn craton and the CA1-type Archean granites. On the basis of modeling and geochemical data we suggest that the leucogranodiorite-granite suites were derived from mixing between a granite, similar to the Ba- and Sr-enriched samples of the Guarantã suite, and trondhjemitic liquids. The granite magmas participating in the mixture were originated by fractional cystallization of 35% of a sanukitoid magma of granodioritic composition. The fractionated mineral phases were: plagioclase (46.72%), hornblende (39.05%), clinopyroxene (10.36%), magnetite (3.12%), ilmenite (0.7%) and allanite (0.06%). The large compositional variations observed in the Guarantã suite can be apparently explained by mixing in different proportions between the granite and trondhjemitic liquids. A model involving a subducting slab underneath a thick oceanic plateau was envisaged to explain the tectonic evolution of the RMGGT. In this context, the low-La/Yb group was formed from magmas originated by the melting of the base of a thickened basaltic oceanic crust at comparatively lower pressures (≤ 1.0 GPa), whereas the medium- and high-La/Yb groups were derived from the slab melting at increasing different pressures (1.0-1.5 and > 1.5 GPa, respectively). Part of these TTG magmas react during their ascent with the mantle wedge being totally consumed and leaving a metassomatized mantle. 50 m. y. later, at ca. 2870 Ma, thermal events, possibly related to the slab-break-off, causing asthenosphere mantle upwelling, or to the action of a mantle plume, may have induced the melting of the metassomatized mantle and the generation of sanukitoid magmas. These magmas may have heated the base of the Archean continental crust during their rising to the surface and could have lead to the local melting of the basaltic crust forming the Água Fria trondhjemite magma. This was accompanied by partial melting (at shallower crustal levels) of the Rio Maria tonalitic-thondhjemitic crust and generation of the potassic leucogranite.
Acesso aberto (Open Access)
lndicadores de estabilidade da matéria orgânica em terras pretas nos sítios arqueológicos Jabuti e Jacarequara (Pará)
(Universidade Federal do Pará, 2015-09-02) SENA, Luciana Freitas de; KERN, Dirse Clara; http://lattes.cnpq.br/8351785832221386; 8351785832221386; LEMOS, Vanda Porpino; http://lattes.cnpq.br/1829861620854008; 1829861620854008
Environmental conditions in the Amazon region favor the weathering and decomposition of soil organic matter, making it depleted in nutrients and difficult agricultural use. But in the same region, areas that have been modified by human action preterit, known as Terra Preta Archaeological (TPA), have different properties, among which stands out the high stability of soil organic matter (SOM) that in some research it is attributed to interactions between the MOS and other soil constituents such as pyrogenic carbon and minerals from the soil. In this study were selected two archaeological sites in the state of Pará, the Jabuti, the cemetery housing type, located in the city of Bragança, and the Jacarequara, the sambaqui type, located in Barcarena, in order to assess the stability of organic matter TPA from soil extracted solutions (depths 30 and 80 cm) and own soil (collected during the implementation of extractors in December 2013) in areas of TPA and vicinity. The characterization of soil solutions was conducted in the period between March and June 2013, based on the macroscopic properties and the chemical indicators: dissolved carbon concentrations (organic, inorganic and total), determined by the combustion method; pH, Eh and conductivity. The SOM stability assessments in the solid phases of the TPA and surrounding areas (ADJ) were based on textural verification of soil chemical indicators (pH, organic carbon concentrations and Ca, K, P, Na, and Mg) and biological represented by the microbial biomass, determined by the method of irradiation / extraction and expressed in terms of carbon (Cbm) and nitrogen (Nbm). The results of the soil solutions showed that two sites in the pH values are higher in depth (80 cm), and at the site Jacarequara values were determined for this parameter up to 7.2, while the site Jabuti pH results do not exceed the value 6. The maximum values of Eh (mV), conductivity (μs) and dissolved organic carbon (mg L-1) in place Jacarequara, 30 cm deep were respectively +201 mV, 427 µs e 13 mg L-1 and in the area adjacent to this site, at the same depth the highest values were +128 mV, 72 µs e 23 mg L-1 for the same parameters. At the Jabuti site and its ADJ, in 30 cm deep, the respective maximum values of the same areas were Eh +108 mV and +96 mV; conductivity 138.87µs and 59.85µs, dissolved organic carbon 12 mg L-1 and 21.08 mg L-1. Comparing the areas of TPA and their ADJ, the data Eh and dissolved organic carbon refer to more stable components in soil areas of solutions of TPA, owing to the more oxidizing values and smaller dissolved organic carbon concentrations, the results conductivity, which is an indicator of the concentration of ions is higher in the TPA reporting the increased availability of nutrients. In both sites, soils presented sandy texture, both in the areas of TPA as the ADJ, the latter being more sandy. In the soil Jacarequara site and its ADJ in the range of 20 to 30 cm deep, the following values were obtained respectively: 119.82 g kg-1 and 20.34 g kg-1 for SOM; pHH2O equal to 6.8 and 4.9; 183 mg/dm3 and 5 mg/dm3 P (available); 39 mg/dm3 and 29 mg/dm3 K (exchangeable); 14.8 cmolc/dm3 and 0.7 cmolc/dm3 Ca (exchangeable); 0.1 cmolc/dm3 and 1.7 cmolc/dm3 Al (exchangeable), 181.26 μg g-1 and 88.74 μg g-1 of Cbm and 3.27 mg kg-1 and 1.91 mg kg-1 Nbm. In the soil of Jabuti site, the determined values were: 83.66 g kg-1 of MOS, pHH2O equal to 4.4; 55 mg/dm3 P (available); 59 mg/dm3 K (exchangeable); 0.3 cmolc/dm3 Ca (exchangeable); 4 cmolc/dm3 of Al (exchangeable); 92.56 mg kg-1 of Cbm and 1.41 mg kg-1 Nbm; in the area adjacent to this site, the values were: 13.13 g kg-1 of MOS, pHH2O equal to 4.6; 4 mg/dm3 P (available); 29 mg dm3 K (exchangeable); 0.3 cmolc/dm3 Ca (exchangeable); 1 cmolc/dm3 Al (exchangeable), 27.54 mg kg-1 of Cbm and 0.96 mg kg-1 Nbm. As well as other archaeological sites with TPA, Jacarequara and the Jabuti had significantly higher levels of nutrients compared to surrounding areas, with the exception of Ca element in Jabuti. In the sites, carbonaceous particles were investigated, showing no intrinsic results pyrogenic carbon. In areas of TPA, the results obtained from the soil analysis indicated positive correlation between the microbial biomass, organic matter and nutrients, which can be associated with better quality of the soil in these areas compared their ADJ, consistently with the data highlighted in the soil solutions. Comparing the two sites, the results indicate that the SOM in Jacarequara site shows more stable constituents.
Acesso aberto (Open Access)
Magmatismo granitóide arqueano da área de Canaã dos Carajás: implicações para a evolução crustal da Província Carajás.
(Universidade Federal do Pará, 2011-08-16) FEIO, Gilmara Regina Lima; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675; 2158196443144675
Geological mapping, geochemical, and geochronological studies undertaken in the Archean granitoids of the Canaã area in the Carajás province, Amazonian craton, Brazil, led to the definition of new granitoid units that entirely replace the Xingu complex in the area. Four major magmatic events are indentified: three of Mesoarchean age and one of Neoarchean age. The succession of events is: (1) at 3.05-3.0 Ga, it occurred the formation of the protolith of the Pium complex and of rocks with similar ages only indicated by inherited zircons found in different units; (2) at 2.96-2.93 Ga, occurred the crystallization of the Canaã dos Carajás granite and the formation of the older rocks of the Rio Verde trondhjemite; (3) at 2.87-2.83 Ga, the Bacaba tonalitic complex, the Rio Verde trondhjemite, and the Cruzadão, Bom Jesus and Serra Dourada granites were formed; (4) in the Neoarchean, at 2.75-2.73 Ga, the Planalto and Pedra Branca suites and charnockite rocks were originated. Geochemically, two groups of granitoid units were distinguished: (1) The tonalitic-trondhjemitic units, which encompass the Bacaba tonalitic complex and the Pedra Branca suite, which are geochemically distinct of typical Archean TTG series, and the Rio Verde trondhjemite, akin to the TTG series; (2) the granitic units which cover more than 60% of the Canaã surface and include five distinct granites. The Mesoarchean Canaã dos Carajás, Bom Jesus, Cruzadão, and Serra Dourada granites are composed dominantly of biotite leucomonzogranites whereas the dominant rocks in the Neoarchean Planalto suite are biotite-hornblende monzogranites to syenogranites with total mafic content between 5% and 20%. The Canaã dos Carajás and Bom Jesus granites and the variety of the Cruzadão granite with higher La/Yb are geochemically akin to the calcalkaline granites, whereas the other varieties of the Cruzadão granite are transitional between calc-alkaline and alkaline granites. The Serra Dourada granite has an ambiguous geochemical character with some features similar to those of calc-alkaline granites and other to peraluminous granites. The Canaã dos Carajás and Bom Jesus granites of Canaã are similar to the High-Ca granites, whereas the Cruzadão and Serra Dourada are more akin to the Low- CaO granites of the Yilgarn craton. The geochemical characteristics of the Mesoarchean Canaã granites approach those of the biotite granite group of the Dharwar craton but the latter are enriched in HFSE and HREE compared to the Mesoarchean granites of Canaã. The accentuated variation of the Sr/Y and (La/Yb)N ratios observed in the Canaã granites should reflect dominantly compositional differences in the sources of the granite magmas with a subordinate effect of pressure. Geochemical modeling suggests that partial melting of a source similar in composition to the average of Early Proterozoic basalts or to the average lower continental crust could be able to give origin to the Bom Jesus granite and to the variety of the Cruzadão granite with higher (La/Yb)N. The residue of melting will contain variable proportions of plagioclase, amphibole, garnet, clinopyroxene ± orthopyroxene, and ilmenite. In the other Canaã granites, plagioclase was dominant, garnet was probably an absent phase in the residue of melting and the influence of amphibole was also apparently limited. A crustal environment and a pressure of 8 to 10 kbar is estimated for the generation of the Bom Jesus and similar granite magmas that left garnet as a residual phase. The Neoarchean Planalto granites have ferroan character and are similar geochemically to reduced A-type granites. The tectonic setting and the association between the Planalto suite and charnockitic series led us to propose classifying these biotite-hornblende granites as hydrated granites of the charnockitic series. The Planalto suite was derived by partial melting of mafic to intermediate tholeitic orthopyroxene-bearing rocks similar to those of the Pium complex. The Archean granitoid magmatism in Canaã significantly differs of that found in most classical Archean cratons, including the Rio Maria terrane, because TTG magmatism is not abundant, sanukitoid rocks are absent and granitic rocks are dominant. The Neoarchean Planalto suite granite has no counterpart in the Mesoarchean Rio Maria terrane of the Carajás province, neither apparently in the Yilgarn and Dharwar cratons. The contrasts between Canaã and the Rio Maria granitegreenstone terrane do not favor a common tectonic evolution for these two domains of the Carajás province. The Archean crust of Canaã has not a juvenile character and the Nd evolution paths suggest the existence of a little older crust in the Canaã area compared to that of Rio Maria. The crust of the Canaã area existed at least since the Mesoarchean (ca. 3.2 to 3.0 Ga) and was strongly reworked during the Neoarchean (2.75 to 2.70 Ga). A similar terrane to that represented by the Canaã Mesoarchean crust or even an extension of it was probably the substratum of the Carajás basin formed during the Neoarchean. Probably there is no an effective transition between Rio Maria and the Carajás basin and the denominated 'Transition' subdomain had more probably an evolution distinct of that of Rio Maria. The Neoarchean evolution of the Carajás province is marked by the upwelling of the asthenospheric mantle in an extensional setting that propitiated the formation of the Carajás basin. Later on, at ca. 2.73-2.70 Ga, the heat input associated with underplate of mafic magma induced the partial melting of mafic to intermediate lower crustal rocks originating the Planalto and Pedra Branca suites, and charnockite rocks. The close association between the Planalto suite and charnockitic rocks suggests similarity between its evolution and that of the high temperature granite magmatism commonly found near the limits between distinct tectonic blocks or in their zone of interaction.
Acesso aberto (Open Access)
Petrogênese e evolução magmática da Suíte Sanukitóide Rio Maria, Terreno Granito – Greenstone de Rio Maria, Cráton Amazônico
(Universidade Federal do Pará, 2009-08-25) OLIVEIRA, Marcelo Augusto de; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675; 2158196443144675
The Archean sanukitoid Rio Maria suite yielded zircon ages of ~2.87 Ga and is exposed in large domains of the Rio Maria Granite-Greenstone Terrane, southeastern Amazonian craton. It is intrusive in the greenstone belts of the Andorinhas Supergroup, in the Arco Verde, Mariazinha, and Caracol tonalite, and Mogno trondhjemite. Archean potassic leucogranites, Água Fria trondhjemite, and the Paleoproterozoic granites of Jamon Suite are intrusive in the rocks of the Rio Maria suite. The dominant rocks have granodiorite to subordinate monzogranitic compositions, with minor proportions of intermediate quartz-diorites or quartz-monzodiorites rocks, in addition to mafic end members occurring as layered rocks or as enclaves. The Rio Maria suite has clear geochemical characteristics of Sanukitoids rocks (high Mg#, elevated Cr and Ni contents, LREE enrichment, and high Ba and Sr contents relative to typical calc-alkaline series). The significant geochemical contrasts between the occurrences of the granodiorites in different areas suggest that this unit corresponds in fact to a granodioritic suite of rocks derived from similar but distinct magmas. In spite of their broad geochemical similarities, granodiorites, intermediate rocks, and mafic enclaves show some significant differences in their REE patterns and in the behavior of Rb, Ba, Sr, and Y. The granodiorites and intermediate rocks are not related by fractional crystallization and the internal evolution of intermediate rocks were leaded by fractionation of amphibole + biotite ± apatite, whereas granodiorites evolved by fractionation of plagioclase + amphibole ± biotite. The layered rocks should have been derived from the granodiorite magma by accumulation of 50% of amphibole (dark layer) and 30% of amphibole ± plagioclase accumulation (gray layer). Modeling and geochemical data suggest that mafic enclave and granodiorite magmas were originated at different depths and should have mingled during their ascent and final emplacement and a limited interaction would explain the relatively uniform geochemical behavior of each rock variety and the distinct trends displayed by their rocks in different modal and geochemical diagrams. These contrasts between granodiorites and mafic enclaves are reflected in the behavior of the Sr and Y, which are generally seen as good indicators of the pressure of melt formation. The behavior of these elements, observed in different sanukitoid rocks from Archean terranes worldwide, indicates that the geochemical and modal contrasts observed between the granodioritic (granodiorites) and monzonitic (mafic enclaves) sanukitoid series are a general feature of these rocks and their origin is strongly dependent of the pressure of magma generation and, as a consequence, that the nature of the series could indicate the approximate depth of formation of its magma. The petrogenesis of the Rio Maria suite requires melting of a modified mantle extensively metasomatized by addition of about 30% TTG-like melt to generate the granodiorite (21% of melt) and intermediate magmas (24% of melt), and ~20% TTG-like melt in the case of mafic enclave magma (9% of melt). Our modeling results indicate that an active subduction tectonic setting was present in the Rio Maria terrane in between 2.98 to 2.92 Ga to generate the TTG magmas and the proposed metasomatism of the mantle by these magmas, before the melting process responsible for the origin of the sanukitoid magmas. A tectonothermal event at ~2.87 Ga, possibly related to a mantle plume, causing the partial melting of the metasomatized mantle and generating the Rio Maria sanukitoid magmas. In the rocks of the Rio Maria suite, the mineral assemblage is dominated by amphiboleplagioclase-biotite and epidote minerals, all of inferred magmatic origin, pyroxenes being notably absent. Textural and compositional criteria indicate that amphibole is a principal mineral on the liquidus of all the Rio Maria rocks. To derive crystallisation conditions, the phase assemblages, proportions and compositions of the natural rocks were compared with experimental works carried out on similar magma compositions. The comparison shows that the parental magmas were water-rich, with more than 7 wt% dissolved H2O near liquidus, with crystallisation temperature in the range 950-680°C. The Mg/(Mg+Fe) ratios of both amphibole and biotite indicate fO2 conditions in the range NNO + 0.5 up to NNO + 2.5, therefore pointing to both water-rich and oxidizing conditions for sanukitoid magmas. Analyses of amphibole aluminium content in cumulate rocks, indicate in addition a high pressure crystallisation stage, around 700-1000 MPa, prior to emplacement in the upper crust at around 200 MPa. Sanukitoid magmas share therefore two of the principal characteristics of modern arc magmas, elevated redox sate and volatile contents, which suggest that they may have formed in a geodynamic environment broadly similar to present-day subduction zones.
Acesso aberto (Open Access)
Petrogênese e história tectônica dos granitóides mesoarqueanos de Ourilândia (PA) – Província Carajás
(Universidade Federal do Pará, 2022-09-16) SILVA, Luciano Ribeiro da; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506; https://orcid.org/0000-0001-7976-0472
Zircon U-Pb-Hf isotopic data from the main Mesoarchean units in the Ourilândia do Norte area (Carajás Province, Amazon Craton) were combined with a review of the main geological-structural, petrographic and geochemical aspects of these rocks, which allowed a redefinition of local stratigraphy, as well as a better understanding of the nature of the sources, based on geochemical modeling. In addition, a modern framework of the tectonostratigraphic correlations and the main events that led to the stabilization of the province was presented, as well as their implications for the origin of the plate tectonics. The Ourilândia granitoids are composed of interdigitated batholiths of sanukitoids and potassic granites, with subordinate TTG. (1) The TTG represent the oldest event in the area (2.92 Ga) and they are composed of tonalitic xenoliths (Mogno suite) and a porphyritic trondhjemite stock (Rio Verde suite), in which biotite is the main mafic mineral. The xenoliths are intensely deformed and the trondhjemite presents small mafic enclaves. The xenolith provided chondritic values of εHf(2.92 Ga) = +2.0 to –0.2 and was formed by partial melting of hydrated metabasalts, while the trondhjemite presented εHf(2.92 Ga) = +2.3 to –3.5 suggesting a more complex origin involving mixing between TTG-type melt and a subchondritic component, reflecting its longer crustal residence time (Hf-TDMC = 3.2–3.5 Ga) in relation to the xenolith (Hf- TDMC = 3.2–3.3 Ga). (2) The sanukitoids were grouped in the Ourilândia sanukitoid suite, which integrates the Arraias granodiorite (2.92 Ga) and the Ourilândia tonalite-granodiorite complex (2.88 Ga), which is composed of tonalites and granodiorites with subordinate quartz monzodiorite, quartz diorite and mafic enclaves. In general, these rocks show hornblende, biotite and epidote as the main mafic phases. The Arraias granodiorite is the oldest sanukitoid unit in the province and one of the oldest in the world. It provided εHf(2.92 Ga) values ranging from chondritic to subchondritic (+1.9 to –4.4) and can be generated by 29% melting of the mantle metasomatized by 40% TTG- type melt, under oxidizing conditions, leaving a residue composed of orthopyroxene, garnet, clinopyroxene and magnetite. Meanwhile, the Ourilândia complex provided values of εHf(2.88 Ga) = +3.4 to –2.0 and its different varieties of granitoids (including quartz monzodiorite) were formed from 18–33% melting of the mantle enriched by 20–40% TTG-type melt, under oxidizing conditions, leaving a residue composed of orthopyroxene, clinopyroxene, garnet, magnetite ±olivine. The mafic enclaves and the quartz diorite show distinct petrogenetic histories and were assumed to be a product of partial melting from the mantle metassomatized by fluids at lower pressures, outside the garnet stability zone. (3) The equigranularmonzogranite represents the largest unit in the area and was correlated with the Boa Sorte batholith (Canaã dos Carajás granitic suite). Its parental magma can be formed by 18% melting from a TTG-type trondhjemite (analogous to those of Água Azul do Norte) under relatively oxidizing conditions, leaving a residue composed of plagioclase, quartz, biotite, magnetite and ilmenite. The U-Pb data allowed to distinguish four zircon populations (3.04 Ga, 2.97 Ga, 2.93 Ga and 2.88 Ga). The youngest population was interpreted as the magmatic crystallization age (coeval to the Ourilândia complex) and provided subchondritic values of εHf(2.88 Ga) = –0.8 to – 4.1, which confirms its crustal origin. The 2.93 Ga population was interpreted as crystals C inherited from the TTG-type source and provided chondritic εHf(2.93 Ga) = +2.8 to –0.7 (Hf-TDMC = 3.1–3.4 Ga), indicating a shorter crustal residence time than the 2.88 Ga population (Hf-TDMC = 3.3–3.5 Ga). The populations dated at 3.04 Ga and 2.97 Ga were interpreted as xenocrystals with εHf(3.04 Ga) = –1.7 to –2.2 (Hf-TDMC = 3.5 Ga) and εHf(2.97 Ga) = +1.4 to –5.7 (Hf-TDMC = 3.3–3.7 Ga), respectively. (4) The high-Ti porphyritic granodiorite and the associated heterogranular monzogranite are closely related to the Boa Sorte granite and were grouped in the Tucumã granodiorite-granite suite, which has affinity with the Closepet (Dharwar craton, India) and the Matok (Pietersburg block, South Africa) granites. The high-Ti granodiorite can be formed by 30% melting from the mantle enriched with 40% of TTG-type melt under oxidizing conditions, leaving a residue composed of orthopyroxene, olivine, plagioclase, clinopyroxene and magnetite, with the participation of a component enriched in HFSEs, such as sediments, fluids and/or asthenosphere materials. The petrogenesis of the monzogranite of this suite involved mixing between 40% crust-derived magmas (Boa Sorte granite) and 60% enriched mantle-derived magmas (high-Ti granodiorite). A three-stage tectonic model is assumed to explain the C origin and isotopic signature of the studied granitoids. In general, the Hf-TDMC ranging from 3.7 to 3.1 Ga, indicating the existence of a Paleoarchean crustal component, which was generated in long-lived dome-and-keel tectonics (~600 Ma) and later recycled in the mantle allowing its enrichment from low-angle subduction in Mesoarchean (2nd setting), where the TTG-type granitoids and the first sanukitoid generation were formed at 2.92 Ga. Then, a short-lived collision (3rd setting) defined by the peak regional metamorphism (2.89–2.84 Ga) and associated with crustal thickening and slab breakoff allowed the origin of large volumes of mantle- and crust-derived magmas at ~2.88 Ga, where the ascent and emplacement were conditioned by shear zones.
Acesso aberto (Open Access)
Petrografia e evolução crustal da porção sul do Domínio Pacajá, Cráton Amazônico: evolução policíclica do Mesoarqueano ao Riaciano
(Universidade Federal do Pará, 2025-08-13) NERI, Arthur Santos da Silva; DALL’ AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
The integration of field, petrographic, mineralogical, geochemical, geochronological (U-Pb in zircon, monazite, and titanite), and isotopic data (Sm-Nd in whole rock and Lu-Hf in zircon) undertaken in the southern portion of the Bacajá Domain enabled the identification and characterization of new granitoid and charnockitic units previously encompassed within the Cajazeiras Complex. These discoveries allowed a redefinition of the regional stratigraphy and advancing the understanding of the crystallization conditions, origin, and evolution of magmatic and metamorphic orthoderived rocks. A long-lived Rhyacian magmatic event (~70 Ma) was recognized, beginning around 2.12 Ga and lasting until 2.05 Ga. During this interval, the following units were identified: Bandeirante (2.12 Ga, εHf(t) = -6.5 to -4.6, εNd(t) = -3.40); and Alto Rio Preto (2.10-2.06 Ga, εHf(t) = -10.2 to -6.3, εNd(t) = -8.96 -2.80) granites; Maravilha (2.09 Ga, εHf(t) = - 9.2 to -8.2, εNd(t) = -3.01 to -1.91) and Serra Azul (2.07 Ga, εHf(t) = -8.8 to -5.8, εNd(t) = -6.44 to -4.71) charnockites; Bernardino granite (2.05 Ga, εNd(t) = -6.71). Geochemically, the units are mostly high-K calc-alkaline and magnesian (Alto Rio Preto and Bernardino granites, Serra Azul charnockite), transitioning to calcic or alkali-calcic and ferroan (Bandeirante granite and Maravilha charnockite, respectively). They range from metaluminous to weakly peraluminous, except the Bernardino granite, which is strongly peraluminous. The Nd-Hf isotopic integration indicates a crustal source with strongly negative epsilon values and Archean model ages, with a marked contrast to crystallization ages, pointing to long crustal residence times. These granitoids were generated by the collision between the Bacajá and Carajás domains in a late- to post-collisional setting during the Transamazonian Orogeny. Crustal thickening and subsequent delamination are interpreted as the main mechanisms responsible for partial melting and generation of these magmas. The Nd-Hf isotopic signatures reveal a coherent crustal compartmentalization between the Bacajá, Carecuru and Lourenço (Amazonian Craton) and Bauolé-Mossi domains (West Africa Craton), suggesting that these segments were juxtaposed during the amalgamation of the Columbia supercontinent. The Alto Rio Preto granite is composed of epidote-bearing granites and granodiorites-tonalites. This granite was emplaced at pressures of 0.4-0.7 GPa and temperatures between 949 and ~640 ºC, evolved under oxidizing conditions (NNO±0.5 to ±1), with initial water contents of ~2-6 wt%. The preservation of magmatic epidote results of a complex interaction between generation and emplacement pressures, oxidizing conditions and water content in the magma, combined with low density and viscosity that facilitated rapid magma ascent (4-5 km/year) through the crust, preventing complete epidote dissolution. Field and petrographic data suggest that this granite represents a syntectonic intrusion, with geochemical affinities with high-K calc-alkaline series. The parental magma of the monzogranitic facies was derived from dehydration melting of a basaltic source at 0.99 GPa and 865 °C leaving an amphibolite residuum. These granitoids represent an example of crustal reworking of lower mafic crust and do not contribute to net crustal growth in the collisional zone between the Bacajá and Carajás domains. The Maravilha charnockite comprises two petrographic associations: (i) monzonite-granite-charnockite and (ii) granodiorite-monzogranite, with or without igneous orthopyroxene and fayalite + quartz. The (i) association crystallized at temperatures between 1052 and ~680 °C, and evolved under reducing (FMQ±0.5), with ≤3 wt% initial water contents. The (ii) crystallized at temperatures between 918 and ~680 °C and evolved under oxidizing conditions (NNO±0.5), with ~4 wt% initial water contents. Both associations were emplaced at pressures between 0.3 and 0.6 GPa The Serra Azul charnockite consists of tonalites, granodiorites, and rare granites, with or without igneous orthopyroxene. These rocks were emplaced at pressures 0.3-0.6 GPa, temperatures between 1078 and ~700 ºC, and evolved under oxidizing conditions (NNO±0.7 to ±2), with initial water contents ~ 2-3 wt%. Thermodynamic data indicate that fayalite is restricted to low pressures (≤0.3 GPa) and reduced conditions (FMQ -2 to -0.6), but it can crystallize under water-rich conditions (2.3 to 6.2 wt%, possibly up to 9 wt%). In contrast, orthopyroxene can crystallize over a wide pressures range (0.1-1 GPa), from reduced to oxidizing conditions (FMQ-2 to NNO+2.5), and under moderate water contents (~5.2 to 6.5 wt%). The Cajazeiras Complex comprises tonalitic to monzogranitic orthogneisses crystallized at 2.97-2.94 Ga, followed by Pb-loss/metamorphism at 2.80–2.81 Ga and Paleoproterozoic metamorphism 2.21-2.01 Ga. These rocks show geochemical affinities with sanukitoid s.l., representing the oldest sanukitoid magmatism in the Amazonian Craton and the second oldest worldwide. The Nd-Hf data (εNd(t) +0.65; εHf(t) +0.5 to +2.5) suggest a juvenile contribution and short crustal residence time, with model ages close to the crystallization age. The discovery of these rocks implies that the mantle was already metasomatized in the Mesoarchean and opens possibilities for the presence of other typical Archean rocks in the basement of the domain. These orthogneisses were metamorphosed under upper amphibolite to granulite facies. The metamorphic peak was marked by the assemblage clinopyroxene-amphibole-biotite-quartzmagnetite- ilmenite-melt, under conditions of ~0.52–0.55 GPa/760–790 °C at ~2.21 Ga. Cooling toward the solidus occurred at ~ 2.10-2.08 Ga, and retrograde metamorphism is represented by the amphibole-biotite-quartz-magnetite-ilmenite-H₂O assemblage, developed under ~0.40–0.48 GPa/600–650 °C at ~2.01 Ga.
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Petrologia e geotermobarometria das rochas metamórficas do Cinturão Araguaia: região de Xambioá-Araguanã (TO)
(Universidade Federal do Pará, 2016-12-16) PINHEIRO, Bruno Luís Silva; GORAYEB, Paulo Sérgio de Sousa; http://lattes.cnpq.br/4309934026092502
In order to contribute to the understanding of the metamorphic processes of the metamorphic rocks of the Araguaia Belt (CA), this thesis presents field data and metamorphic modeling, used as tools to obtain the maximum conditions of P-T reached by the units located in the Xambioá-Araguanã (TO) region of the rocks studied are five samples of Staurolite-garnetbiotite- muscovite-schist with Kyanite and a sample of Garnet amphibolite, belonging to the Xambioá Formation and Xambica Suite, respectively. The study of the metamorphism occurred through petrographic, chemical analyzes of rocks and minerals of the main associations of pelitic rocks, semipelitic and mafic rocks that comprise the zone of greater metamorphic degree of CA, for later analysis by metamorphic modeling in the NCKFMASH system and optimized geothermobarometry, In the avPT mode, in the THERMOCALC program, as well as the Hb-Pl software, which made it possible to identify PT metamorphic peak conditions. In addition to defining an approximate age of metamorphism using the Ar-Ar method in biotite and amphibole. The petrographic-mineralogical study identified the main mineral parageneses in the studied micaxists, such as St + Grt + Bt + Ms + Qtz ± Pl (An12-31) + Ky, and in the amphibolites Hb + Grt + Bt + Pl (An12-25). The mineral chemistry results showed that the pomegranate composition of the six samples is dominated by the almandide molecule, which is followed by pyropo, thickenstock, and andradite, increasing Fe2 + and Mg from the nuclei to the edges, with a concomitant decrease of Mn and Ca. The higher Fe and Mg contents towards the edges indicate an increase in the temperature conditions during mineral development. The composition of the biotite is in the transition of the biotite with phlogopite, becoming more ferromagnesian mica. Staurolite from the core to the border is enriched in Fe2 + and depleted in Mg, which may suggest reactions in contact with the matrix and / or with micas or grenades. Metamorphic modeling in the NCKFMASH system resulted in pseudosections with similar topologies for samples BP002, BP149 and BP299, suggesting that the maximum metamorphic conditions they were subjected to are similar, being situated within a PT window with pressure approximately between 7 and 9 kbar and temperature between 630 and 665 ° C. The models of composite isopleths of the minerals calculated in the pseudosections indicate a higher participation of Mg and a lower participation of Ca in the composition of the main minerals according to the increase of the metamorphic P-T conditions in the region, compatible with the mineral chemistry results of the studied rocks. In addition to the plagioclase and the pomegranate of the sample BP002 presenting as good indicators of metamorphism conditions, with values of 8 kbar and 660 °C, in which the coreedge variation of Ca and Na in plagioclase crystals and the variation Core-edge in the iron content of the grenades show a progressive barometric-type metamorphic trajectory, represented by a small slope curve, coming from the trivariant field Chl + Grt + Bt + Ms. PT estimates obtained in the avPT mode of THERMOCALC in all the selected samples (BP002, BP005, BP149, BP149, BP299, BP006), as well as in the Hb-Plag software in the amphibolites (BP006), presented enough Consistent and consistent with calculations of metamorphic peak conditions via THERMOCALC for rocks in the Xambioá-Araguanã region, although there are discrepancies in the calculated results. All calculated P-T results are compatible with the field of the amphibolite facies of the mean P-T series, typical of continental orogenic belt environments and therefore characteristic of continental collisions. Metamorphic conditions are reinforced with the mineral chemistry results of calcium amphiboles suggesting the same average pressure conditions of the Dalradian terrain of Scotland. The air-air ages in minerals obtained in the metapelites and amphibolites in this thesis were similar, around 504 Ma, and they show that the peak of the metamorphism of the amphibolite facies in the region under study has an older age and they suggest that it was next to the Neoproterozoic-Paleozoic interface, because these Ar-Ar ages obtained are younger ages than the K-Ar ages of 520-560 Ma, interpreted as relating the metamorphism of the CA with the Brasilian thermo-tectonic event, and because it is within the error of the U-Th-Pb monazites chemical age in feldspathic schist biotite from an area near the city of Presidente Kennedy (TO), 513 ± 14 Ma interpreted only at a younger age than the mean age evaluated for the metamorphism of the Araguaia Belt (550 - 530 Ma).
Acesso aberto (Open Access)
Petrologia experimental e química mineral das suítes Neoarqueanas Vila Jussara e Planalto, Província Carajás, Amazônia, Brasil
(Universidade Federal do Pará, 2023-03-20) CUNHA, Ingrid Roberta Viana da; SCAILLET, Bruno; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
In the Carajás Province (CP), during the late stages of the neoarchean (2.75-2.73), in the Sapucaia and Canãa dos Carajás domains granitoids represented by the Vila Jussara and Planalto suites were formed respectively. These suites are metaluminous and have a geochemical affinity with A-type granites and FeO/(FeO+MgO) whole rock ratios that vary from ferroan to magnesian. Chemical-mineralogical studies performed in these neoarchean granites, based on optical microscopy, scanning electronic microscopy, electron microprobe and experimental petrology revealed notable variation between the main mineral phases. Magmatic epidote is a common mineral phase in the reduced, oxidized and magnesian varieties of the Vila Jussara suite, with pistacite contents between 25 and 30% mol. In the Planalto Suite and others neoarchean granites of the CP magmatic epidote is absent. The study of the dissolution kinetics of Archean epidotes of the CP reveals that its formation and stability are directly linked to pressure, temperature and oxygen fugacity conditions, however, its stability is also conditioned by mechanisms of magma rise, emplacement and crystallization, which affected the dissolution intensity of the epidote crystals. Chemical-mineralogical performed on titanites of the Vila Jussara and Planalto Suites and the paleoproterozoic Jamon Suite revealed notable textural and compositional variations. The titanite’s Fe/Al ratios are quite variable in the studied granites, three major titanite groups were distinguished: 1) high Fe/Al ratio (Fe/Al>0.5); 2) moderate Fe/Al ratio (0.5≤Fe/Al≥0.25); and 3) low Fe/Al ratio (Fe/Al<0.25). Furthermore, in general, the obtained data support the major titanite tendency to stabilize under oxidizing conditions, near the nickel-nickel oxide buffer (NNO), however, the occurrence of magmatic titanite in the reduced varieties from the Planalto and Vila Jussara Suites ratifies that its crystallization is possible under conditions near the fayalite-magnetite-quartz buffer (FMQ). Moreover, experimental petrology studies performed on the same neoarchean suites, reveal that the sample MDP-02E, with tonalitic composition, which represents the magnesian oxidized magma from the Vila Jussara suite, exhibits SiO2 content around 60% in the whole rock composition and 61.05% in the experimental glass, while the sample with sienogranitic composition (AMR-116), from the strongly reduced variety of the Planalto Suite, shows SiO2 content of 74.13% in whole rock and 73.17% in glass, pointing out that the initially calibrated experimental conditions approach the natural magmatic conditions. To characterize the crystallization parameters of the tonalitic and sienogranitic magma, nine experiments were performed on the two samples, with the following conditions: pressure ~4 kbar, ƒO2 ~NNO-1.3 (1.3 log unit bellow the NNO buffer) and temperature varying from 850°C to 668°C and water content from 9% to 6% in weight. Experiments with ƒO2 ~NNO+2.4 and temperatures of 800°C to 700°C with similar pressures and water content variations of the reduced experiments were also performed. Subordinately, experiments with pressures of 8 to 2 kbar with variable redox conditions were performed. These experiments show that the tonalite from the Vila Jussara Suite was crystallized at ~4 kbar from a water-rich magma (>5% in weight) in ƒO2 oxidizing conditions, probably between NNO and NNO+1. On the other hand, the experiments performed on the sample with sienogranitic composition from the Planalto Suite show a main paragenesis of Cpx+Fa which substantially diverge from the natural minerals, suggesting that the experiments did not reach the natural conditions.
Acesso aberto (Open Access)
Uso de ferramentas multidisciplinares na avaliação de vulnerabilidade e risco a subsidência no meio cárstico na cidade de Castanhal, Nordeste do Pará – Brasil.
(Universidade Federal do Pará, 2009-11-06) PINHEIRO, Ana Valéria dos Reis; GOUVEIA, José Luiz; ABREU, Francisco de Assis Matos de; http://lattes.cnpq.br/9626349043103626; 9626349043103626
Castanhal was chosen for this work for being one of the cities with the most demographic growth and also for having its public water supply taken from the Pirabas aquiferous system, whiose main characteristic as the fact that it is formed by carbonaceous rocks. The hypothesis suggested in this work is that this lithology explains the loss of drilling fluid that occurred during the drilling of the three wells in the Jaderlândia district, what can yield a subsurface collapse. The methodology applied in this work consisted of several techniques remote sensing, geomorphology, neotectonics, hydrogeology, geophysics and environmental analysis. The maps were prepared utilizing a Landasat -5/TM satellite images, SRTM images, aerial photos in 1: 70.000 scale and orthophotos mosaics in 1: 10.000 scale. To enhance the geological data, geophysical methods such as gravimetry, resistivity, and well logging: γ rays, spontaneous potential and resistance were applied. The hydrogeological study of Castanhal city was conducted mainly by using data from wells intended for public water supply and from private wells. Geologically, the northeast region of Pará state, where Castanhal city is located, is composed by Pós-Barreiras sediments and Barreiras Group rocks, that are underlied by Pirabas Formation, of calcareous constitution which is the focus of this work. The drainage system is structurally ordered and is represented by a stockwork pattern striking mainly NE-SW and NW-SE, withstrong asymmetry, which allowed to visualize a tectonic sectioning of the Sheet Castanhal SA.23-V-C-I including the Castanhal city, identifying in this way high and low blocks that where confirmed by lithostratigraphics profiles of the wells and by the geophysical survey. The tectonic structure is congruous with the dextral system transcorrent of Riedel, and still contains relaystructures found in all the Sheet of Castanhal, favoring to the recharge of the water-bearing systems; however, this increases its vulnerability to contamination. The hydraulical load and the underground flow present a zone of recharge in the center of the Castanhal city and another one in the Village of Apeú, and indicate effluent draining. The analysis of the quality of the waters showed high contents of total iron and turbidness in some wells and of calcium carbonate in the wells supplied by the Pirabas aquifer system. The gravity survey showed a positive anomaly inthe center of the city, indicating a less deep basement, what was corroborated by the resistivitysurvey. In Jaderlândia and Bom Jesus quarters in the city of Castanhal negative anomalies lined up, concordant with drainage alignments of NW direction indicating the construction of two4 karstics buildings between 60 m and 100 m of depth and 200 m and 400 m of extension representing a high risk of collapse in these quarters to occur. The interaction of the abovementioned information made possible the elaboration of geological sections, blocks diagrams and thematic maps that gave origin to the map of environmental risk for the city of Castanhal.

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