Navegando por Assunto "Geologia estratigráfica - Arqueano"

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Geologia e geoquímica dos granitóides Arqueanos da área de Bannach (PA): uma reavaliação das áreas de ocorrência do trondhjemito mogno e granodiorito Rio Maria
(Universidade Federal do Pará, 2018-08-21) MACHADO, Jean Ricardo Mesquita; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The Bannach area is located in the center-west of Rio Maria Domain, Carajás Province, Amazonian craton. Based on field relationships, petrography and geochemical behavior, it was possible to identify six varieties that was divided into two groups: (i) high silica and low Mg group, represented by trondhjemitic rocks associated with mogno Trondhjemite (TdhMg), leucogranodiorites and fine grained granitoids and (ii) low silica and high Mg groups, represented by biotite granodiorites, amphibole bearing tonalites and biotite tonalites (enclaves). The trondhjemites, leucogranodiorites are the most extensive batholiths of the region, covering approximately 90% of the work area, presenting medium-to-coarse heterogranular texture and E-W to NW-SE ductile deformation features. The biotite granodiorites occur as a small stock in the north-east, being formed by more enriched in mafic minerals rocks than the predominant granodioritic variety. The amphibole bearing tonalites (± quartz diorites) is emplaced along shear zones that intersect the central portion of the area, being more deformed than the other rocks and the only amphibole bearing granitoid. In smaller proportions, the biotite tonalites represent mega-enclaves of the trondhjemitic rocks, whereas the fine granitoids intersect the other rocks of the region. These varieties are divided into two groups. Geochemically, the group of high silica (SiO2> 70%) presents high levels of Al2O3, CaO and Na2O (especially leucogranodiorites) in detriment of Fe2O3, MgO, Ni and Cr. Moreover, these varieties have high La/Yb and Gd/Er ratios, discrete or absent Eu negative anomalies, and strongly fractionated REE patterns. On the other hand, the low silica granitoids present high content of Fe2O3, MgO, Ni and Y, emphasizing the high K- Ba-Sr content of the biotite granodiorites in relation to the other granitoids in the area, in addition to their moderate to high La/Yb ratios, while the other low silica granitoids present low La/Yb ratios because of the high HREE content, which provides a sub-horizontal REE pattern. These differences trace back distinct formation processes for Bannach granitoids. Although the formation of trondhjemites and leucogranodiorites occurs in the garnet stability zone, its chemical differences go back to sensible differences in its magma. The origin of the trondhjemites is associated with the partial melt of garnet amphibolite, under high pressure conditions in a subduction environment. The leucogranodiorites, due to their higher sodium enrichment, Ba and Sr, have their compositional control associated to different degrees of melting of basalt under different pressure levels and by a source richer in subducted sediments of the oceanic crust to produce magmas of similar composition to the leucogranodiorite. Therefore, it is assumed that these rocks would have originated by the fusion of enriched tholeiite basalts installed below an older TTG crust that would have been assimilated by these melts. The geochemical aspects, such as the high LILE content and even high presence of mantle affinity elements (Mg, Ni and Cr) of the biotite granodiorites and amphibole bearing tonalites may denounce their affinities with the rocks of the Sanukitoid suite of Rio Maria. The ambiguous geochemical character of the biotite granodiorites associated with the highest SiO2 content when compared to the quartz diorites, as well as their higher levels of Rb and Ba, Sr, Y and the La/Y and Sr/Y ratios indicate a more evolved and conditions of formation in higher pressure and that has felsic parent magmas, as well as a mafic component acting in its origin, approaching the Closepet-type granites. In this way, these compositional affinities indicate a strong petrogenetic analogy, with an origin from an enriched mantle or even from a mafic source of high-K. On the other hand, the less evolved character of the amphibole tonalites, as well as the low La/Yb and Sr/Y ratios indicate that these have a higher mantle affinity and that formed at low depths. It is assumed that the origin of these rocks would have been from a metassomatized mantle by slab fluids in a subduction environment.
Desconhecido
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).
Acesso aberto (Open Access)
Geologia, mineralogia e afinidades petrológicas dos granitóides neoarqueanos da porção central do Domínio Canaã dos Carajás
(Universidade Federal do Pará, 2017-10-28) OLIVEIRA, Vinícius Eduardo Silva de; OLIVEIRA, Davis Carvalho de; http://lattes.cnpq.br/0294264745783506
The central portion of the Canaã dos Carajás domain, located in the northern part of the Carajás province was originally marked by the occurrence of undifferentiated rocks belonging to the Xingu complex and Plaque suite, as well as greenstone belts, mafic rocks of the Pium diopside-norite and high K calc-alkaline leucogranites (Boa Sorte and Cruzadão granites). A semi-detailed geological mapping (1:100.0000) was carried out in the Vila União area and allowed the identification of several deformed granite bodies intrusive in the Mesoarchean units. They correspond to the most expressive unit of the studied area and are composed predominantly of monzogranites with chemical and mineralogical affinity with the Neoarchean A-type granites of the Planalto and Vila Jussara suites. The variable felsic and ferromagnesian minerals contents, as well as the different proportions between them, allowed to distinguish four major groups of granitoids: (i) biotite-hornblende monzogranites (BtHblMzG); (ii) biotite granites and leucogranites (BtLG); (iii) biotite-hornblende tonalites (BtHblTn); and quartz diorites (QD). The tectonic foliation of these rocks follows the regional E-W trend and exhibits high angles (70-85°). Well-developed core and mantle structures in quartz and feldspar crystals, as well as the presence of serrated and irregular contacts between these crystals suggest that dynamic recrystallization occurred at relatively high temperatures (> 500 °C). These rocks exhibit a wide variation in silica content (61.7 – 75.91 wt%), are metaluminous to slightly peraluminous and show affinity with A-type (high HFSE) and ferroan granites. Based on magnetic petrology studies it was possible to distinguish two groups of rocks: (1) granites containing only ilmenite with low magnetic susceptibility values (MS; <0.570 × 10-3 SI), and (2) granites with magnetite as the main iron and titanium oxide mineral and higher MS values (> 1.437 × 10-3 SI). Textural and compositional evidences indicate that magnetite and ilmenite are earlycrystallized phases and titanite has magmatic origin. Amphiboles are calcic and classified as hastingsite, whereas biotites are rich in the annite molecule. The relatively high Fe/(Fe + Mg) ratios found in the amphiboles of the BtHblMzG and BtHblTn varieties indicate that these granitoids were formed under low to moderate fO2 conditions, whereas in the BtLG the lower values of this ratio suggest more oxidizing conditions. Geothermometers point to crystallization temperatures between 830 – 930 °C in the different facies. The high total Al content in the amphibole crystals suggests crystallization at pressures between 400 and 800 MPa, indicating that these granitoids were emplaced at different crustal depths.
Acesso aberto (Open Access)
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.
Acesso aberto (Open Access)
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.
Acesso aberto (Open Access)
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.
Acesso aberto (Open Access)
Petrografia, química mineral e parâmetros de cristalização da suíte Planalto, Província Carajás
(Universidade Federal do Pará, 2015-07-28) CUNHA, Ingrid Roberta Viana da; FEIO, Gilmara Regina Lima; http://lattes.cnpq.br/9344671380219647; DALL'AGNOL, Roberto; http://lattes.cnpq.br/2158196443144675
The Planalto Suite is located in the Canaã dos Carajás Domain of the Carajás Province in the southeastern part of the Amazonian Craton. The suite has Neoarchean age (~2.73 Ga), ferroan character and affinity with A-type granites. Magnetic petrology studies allowed the distinction of two groups: (1) Ilmenite granites devoid of magnetite and showing low magnetic susceptibility (MS) values (MS between 0.6247x10-3 and 0.0102x10-3 SI; average of 0.1522x10-3); (2) Magnetite-ilmenite-bearing granites which display comparatively higher but still moderate MS values (between 15.700x10-3 and 0.8036x10-3 SI; average of 5.1717x10-3). Textural evidence indicates that amphibole, ilmenite, titanite, and, in the rocks of Group 2, also magnetite formed during magmatic crystallization. However, titanite chemical composition suggests that it was re-equilibrated by subsolidus processes. The amphibole varies from potassian-hastingsite to chloro-potassian-hastingsite and shows Fe/(Fe+Mg) >0.8. Biotite also shows high Fe/(Fe+Mg) ratios and is classified as annite although relatively enriched in Al compared to the annite end member. Plagioclase porphyroclasts are oligoclase (An25-10) and the grains of the recrystallized matrix display oligoclasic or albitic composition (An9-2). Mineral chemistry, magnetic petrology and whole rock geochemistry indicate that the dominant group 1 granites of the Planalto Suite were formed under reduced conditions below the FMQ buffer. The group 2 granites crystallized under more oxidizing conditions on or slightly above the FMQ buffer. Pressures of 900-700 MPa for the origin and of 500-300 MPa for the emplacement were estimated for the Planalto magmas. Geothermometers suggest initial crystallization temperatures between 900 °C and 830 °C and water content in the magma higher than 4 wt %. The mineralogical comparison between the Planalto Suite and the Archean subalkaline Estrela Granitic Complex of the Carajás Province reveals strong compositional analogies indicating that they were probably formed under similar conditions. The amphibole and biotite compositions of Planalto and Estrela granites are relatively enriched in Al being comparable with those of the Neoarchean Matok Pluton of the Limpopo Belt. They differ using the same criteria of the Proterozoic rapakivi A-type granites. On the other hand, in terms of Fe/(Fe+Mg) ratio, the Planalto and Estrela granites approach the reduced Mesoproterozoic rapakivi granites and the reduced to moderately oxidized Paleoproterozoic granites of, respectively, the Velho Guilherme and Serra dos Carajás suites and differ from the oxidized granites (Jamon Suite) of the Carajás province and also of Matok pluton. It is concluded that the Planalto Suite and similar Neoarchean granites of the Carajás Province differ in mineralogical characteristics and crystallization parameters of some classic examples of A-type granites and, except for its reduced character, they are akin to the Neoarchean Fe-K and Mg-K granitoids of the Limpopo Belt, as exemplified by the Matok granitoids. This indicates that the collisional setting of Carajás and Limpopo exerted strong influence in the nature of the Neoarchean granitoid magmas.