O PAPEL DAS ESTRUTURAS LITOLÓGICAS NA DINÂMICA E EVOLUÇÃO DO MACIÇO DE URUBURETAMA, CEARÁ, BRASIL

2019 ◽  
Vol 21 (2) ◽  
pp. 81-93
Author(s):  
Abner Monteiro Nunes Cordeiro ◽  
Islane Pinto de Carvalho ◽  
Frederico De Holanda Bastos ◽  
Danielle Lopes de Sousa Lima
Keyword(s):  
Structural Control ◽  
Granitic Rocks ◽  
Borborema Province ◽  
Northern Portion ◽  
Granitoid Rocks ◽  
Residual Masses ◽  
Semi Arid Region ◽  
The Many ◽  
Lithological Composition ◽  
Geomorphological Evolution

A estrutura litológica de um determinado relevo tem papel fundamental na sua dinâmica e evolução, tendo em vista as propriedades geomorfológicas das rochas. A Serra de Uruburetama é um dos muitos maciços residuais que pontuam o semiárido cearense, cuja constituição litológica tem relação direta com a gênese e evolução de macroformas e microformas graníticas encontradas nesse relevo serrano. Inserido no Domínio Ceará Central da Província Borborema, na porção norte do estado do Ceará, esse maciço é composto, predominantemente por rochas granitoides, sendo imprescindível o conhecimento da composição litológica para compreensão da sua evolução geomorfológica. O presente artigo tem como objetivo expor as principais litologias encontradas na área de estudo, suas propriedades geomorfológicas e as formas de relevo associadas. Para tanto, foi realizado levantamento de literatura referente às propriedades geomorfológicas das rochas graníticas, assim como do quadro geológico e geomorfológico do Maciço de Uruburetama a fim de compreender sua composição e evolução, além de levantamentos cartográficos e utilização de técnicas de geoprocessamento. O Maciço de Uruburetama apresenta diferentes feições graníticas com formas e dimensões variadas, cuja formação, desenvolvimento e exposição dessas feições se devem ao controle estrutural imposto por litologias graníticas e suas descontinuidades estruturais, bem como pela influência de condições paleoclimáticas e pelos processos de erosão diferencial, a que foram submetidas.Palavras-chave: Evolução geomorfológica; Propriedades geomorfológicas das rochas; Formas graníticas. ABSTRACTThe lithological structure of a given landform plays a fundamental role in its dynamics and evolution, considering the geomorphological properties of the rocks. The Mountain of Uruburetama is one of the many residual masses that punctuate the semi - arid region of Ceará, whose lithological constitution is directly related to the genesis and evolution of macroforms and granitic microforms found in this mountain relief.  Located in the Central Ceará Domain of the Borborema Province, in the northern portion of the state of Ceará, this massif is composed predominantly of granitoid rocks, being essential the knowledge of the lithological composition to understand its geomorphological evolution. The present article has as objective to expose the main lithologies found in the study area, its geomorphological properties and the associated relief forms. For that, a literature survey was carried out regarding the geomorphological properties of the granitic rocks, as well as the geological and geomorphological framework of the Uruburetama Massif in order to understand its composition and evolution, as well as cartographic surveys and the use of geoprocessing techniques. The Uruburetama Massif presents different granitic features with different shapes and dimensions, whose formation, development and exposition of these features are due to the structural control imposed by granite lithologies and their structural discontinuities, as well as by the influence of paleoclimatic conditions and the processes of differential erosion, to which they were submitted.Keywords: Geomorphological evolution; Geomorphological properties of rocks; Granite shapes. RESUMENLa estructura litológica de un determinado relieve tiene papel fundamental en su dinámica y evolución, teniendo en vista las propiedades geomorfológicas de las rocas. La Sierra de Uruburetama es uno de los muchos macizos residuales que puntúan el semiárido cearense, cuya constitución litológica tiene relación directa con la génesis y evolución de macroformas y microformas graníticas encontradas en ese relieve Serrano. Insertado en el Dominio Ceará Central de la Provincia Borborema, en la parte norte del estado de Ceará, este macizo está compuesto, predominantemente por rocas granitoides, es imprescindible el conocimiento de la composición litológica para comprender su evolución geomorfológica. El presente artículo tiene como objetivo exponer las principales litologías encontradas en el área de estudio, sus propiedades geomorfológicas y las formas de relieve asociadas. Para ello, se realizó estudio de literatura referente a las propiedades geomorfológicas de las rocas graníticas, así como del cuadro geológico y geomorfológico del macizo de Uruburetama a fin de comprender su composición y evolución, además de encuestas cartográficas y el uso de técnicas de geoprocesamiento. El macizo de Uruburetama presenta diferentes facciones graníticas con formas y dimensiones variadas, cuya formación, desarrollo y exposición de estos rasgos se deben al control estructural impuesto por litologias graníticas y sus discontinuidades estructurales, así como la influencia de las condiciones paleoclimáticas y de los procesos de erosión diferencial a los que han sido sometidas.Palabras clave: Evolución geomorfológica; Propiedades geomorfológicas de las rocas; Formas graníticas.

scholarly journals A preserved early Ediacaran magmatic arc at the northernmost portion of the Transversal Zone central subprovince of the Borborema Province, Northeastern South America

2016 ◽  
Vol 46 (4) ◽  
pp. 491-508 ◽  
Author(s):  
Benjamim Bley de Brito Neves ◽  
◽  
Edilton José dos Santos ◽  
Reinhardt Adolfo Fuck ◽  
Lauro César Montefalco Lira Santos ◽  
...  
Keyword(s):  
Granitic Rocks ◽  
Lower Plate ◽  
Low Grade ◽  
Northeast Brazil ◽  
The South ◽  
Magmatic Arc ◽  
Continental Plate ◽  
Borborema Province ◽  
Northern Portion ◽  
Fold Belts

ABSTRACT: Magmatic arcs are an essential part of crust-forming events in planet Earth evolution. The aim of this work was to describe an early Ediacaran magmatic arc (ca. 635-580 Ma) exposed in the northernmost portion of the Transversal Zone, central subprovince of Borborema Province, northeast Brazil. Our research took advantage of several syntheses by different authors, including theses and dissertations, carried out on magmatic rocks of the study area for the last 30 years. The ca. 750 km long and up to 140 km wide arc, trending ENE-WSW, is preserved to the south of the Patos Lineament, between 35º15' and 42º30'W and 7º15' and 8ºS. About 90 different stocks and batholiths of I-type granitic rocks were mapped along this orogenic zone, preferentially intruding low-grade schists of the Cryogenian-Ediacaran Piancó-Alto Brígida (SPAB) belt. Three igneous supersuites are recognized: a) epidote-bearing granodiorites and tonalites ("Conceição" type); b) high-K calc-alkaline granites ("Itaporanga" type); c) biotite granodiorites of trondhjemite affinity ("Serrita" type). A fourth group of peralkalic and shoshonitic rocks occurs to the south of the previous ones, reflecting special tectonic conditions. NNE-SSW trending Paleoproterozoic fold belts, surrounding Archean nuclei, characterize the continental part of the northern lower plate. The oceanic fraction of this lower plate was recycled by subduction and scarce remnants of which may be seen either within the enclosing low-grade schists or as xenoliths within the arc intrusions. The upper continental plate presents WSW-ENE structural trends and is composed of Neoproterozoic fold belts and Paleoproterozoic reworked basement inliers. Available data bear clear evidence of an Ediacaran magmatic arc built at the northern portion of the Transversal Zone in the Borborema Province, northeast Brazil.

Composition, age, and origin of granitoid rocks in the Davin Lake area, Rottenstone Domain, Trans-Hudson Orogen, northern Saskatchewan

2005 ◽  
Vol 42 (4) ◽  
pp. 599-633 ◽  
Author(s):  
D Barrie Clarke ◽  
Andrew S Henry ◽  
Mike A Hamilton
Keyword(s):  
Granitic Rocks ◽  
Lake Area ◽  
Granitoid Magmatism ◽  
Metasedimentary Rocks ◽  
Metavolcanic Rocks ◽  
Granitic Magmatism ◽  
Deformation Features ◽  
High Grade Metamorphism ◽  
Granitoid Rocks ◽  
Host Rocks

The Rottenstone Domain of the Trans-Hudson orogen is a 25-km-wide granitic–migmatitic belt lying between the La Ronge volcanic–plutonic island arc (1890–1830 Ma) to the southeast and the ensialic Wathaman Batholith (1855 Ma) to the northwest. The Rottenstone Domain consists of three lithotectonic belts parallel to the orogen: (i) southeast — gently folded migmatized quartzo-feldspathic metasedimentary and mafic metavolcanic rocks intruded by small concordant and discordant white tonalite–monzogranite bodies; (ii) central — intensely folded and migmatized metasedimentary rocks and minor metavolcanic rocks intruded by largely discordant, xenolith-rich, pink aplite-pegmatite monzogranite bodies; and (iii) northwest — steeply folded migmatized metasedimentary rocks cut by subvertical white tonalite–monzogranite sheets. Emplacement of granitoid rocks consists predominantly of contiguous, orogen-parallel, steeply dipping, syntectonic and post-tectonic sheets with prominent magmatic schlieren bands, overprinted by parallel solid-state deformation features. The white granitoid rocks have A/CNK (mol Al2O3/(mol CaO + Na2O + K2O)) = 1.14–1.22, K/Rb ≈ 500, ΣREE (sum of rare-earth elements) < 70 ppm, Eu/Eu* > 1, 87Sr/86Sri ≈ 0.7032, and εNdi ≈ –2. The pink monzogranites have A/CNK = 1.11–1.16, K/Rb ≈ 500, ΣREE > 90 ppm, Eu/Eu* < 1, 87Sr/86Sri ≈ 0.7031, and εNdi ≈ –2. The white granitoid rocks show a wider compositional range and more compositional scatter than the pink monzogranites, reflecting some combination of smaller volume melts, less homogenization, and less control by crystal–melt equilibria. All metavolcanic, metasedimentary, and granitic rocks in the Rottenstone Domain have the distinctive geochemical signatures of an arc environment. New sensitive high-resolution ion microprobe (SHRIMP) U–Pb geochronology on the Rottenstone granitoid rocks reveals complex growth histories for monazite and zircon, variably controlled by inheritance, magmatism, and high-grade metamorphism. Monazite ages for the granitoid bodies and migmatites cluster at ~1834 and ~1814 Ma, whereas zircon ages range from ~2480 Ma (rare cores) to ~1900–1830 Ma (cores and mantles), but also ~1818–1814 Ma for low Th/U recrystallized rims, overgrowths, and rare discrete euhedral prisms. These results demonstrate that at least some source material for the granitic magmas included earliest Paleoproterozoic crust (Sask Craton?), or its derived sediments, and that Rottenstone granitic magmatism postdated plutonism in the bounding La Ronge Arc and Wathaman Batholith. We estimate the age of terminal metamorphism in the Davin Lake area to be ~1815 Ma. Petrogenetically, the Rottenstone migmatites and granitoid rocks appear, for the most part, locally derived from their metasedimentary and metavolcanic host rocks, shed from the La Ronge Arc, Sask Craton, and possibly the Hearne Craton. The Rottenstone Domain was the least competent member in the overthrust stack and probably underwent a combination of fluid-present melting and fluid-absent decompression melting, resulting in largely syntectonic granitoid magmatism ~1835–1815 Ma, analogous to granite production in the High Himalayan gneiss belt.

Petrochemistry, tectonic history, and Sr–Nd systematics of the Liscomb Complex, Meguma Lithotectonic Zone, Nova Scotia

1993 ◽  
Vol 30 (3) ◽  
pp. 449-464 ◽  
Author(s):  
D. B. Clarke ◽  
A. K. Chatterjee ◽  
P. S. Giles
Keyword(s):  
Crustal Contamination ◽  
Granitic Rocks ◽  
Low Grade ◽  
South Mountain Batholith ◽  
Mafic Intrusions ◽  
Depleted Mantle ◽  
Isotopic Analyses ◽  
Wide Range ◽  
Granitoid Rocks ◽  
Lithotectonic Zone

The Liscomb Complex (area ca. 240 km2), located in the Meguma Lithotectonic Zone of the Canadian Appalachians, consists of three main lithological components: high-grade gneisses, mafic plutons, and peraluminous granitoid bodies. Field relations and 40Ar/39Ar dating (369–377 Ma) embracing all three lithological groups show that the complex is post-Acadian. The gneisses occur as a domal uplift and represent a mixed volcano-sedimentary package that is structurally, metamorphically, and chemically distinct from the surrounding low-grade metawackes and metapelites of the Meguma Group. The mafic intrusions (quartz gabbro to quartz diorite) have major and trace element compositions (e.g., Ti–Zr–Y, Nb–Zr–Y, Th/Yb – Ta/Yb, rare earth elements) typical of within-plate or volcanic arc materials. The peraluminous granitoid rocks range from two-mica granodiorites to leucomonzogranites, and are mineralogically and chemically very similar to granitic rocks elsewhere in the Meguma Zone. Neodymium and strontium isotopic analyses show that (i) the gneisses have a wide range of εNd and initial Sr isotopic ratios, with Nd model ages that are generally younger than those of the Meguma Group; (ii) the mafic intrusive rocks represent magmas derived from slightly depleted mantle sources (εNd +3.3 to +1.4), in part modified by crustal contamination (εNd +0.5 to −5.0); and (iii) the granitoid rocks isotopically overlap both the South Mountain Batholith and the intermediate gneisses of the Liscomb Complex. The combined field, petrological, and chemical evidence suggests that underplating by mafic magmas, followed by thermal doming of the gneisses, diapirism through the Meguma Group, anatexis, and multiple intrusion of both mafic and felsic magmas best explain the observed relationships in the Liscomb Complex. This mechanical model may also apply to granite generation throughout the Meguma Zone.

scholarly journals IDENTIFICAÇÃO GAMAESPECTROMÉTRICA DE PLACERES RUTILO-MONAZÍTICOS NEOPROTEROZÓICOS NO SUL DA FAIXA SERIDÓ, NORDESTE DO BRASIL

2010 ◽  
Vol 28 (1) ◽  
Author(s):  
Sebastião Milton P. da Silva ◽  
Álvaro P. Crósta ◽  
Francisco J.F. Ferreira ◽  
Hartmut Beurlen ◽  
Adalene M. Silva ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Coarse Grained ◽  
Granitic Rocks ◽  
Gamma Ray Spectrometry ◽  
Geological Data ◽  
Borborema Province ◽  
Two Samples ◽  
Scanning Electron ◽  
The Eu ◽  
Sem Analyses

Dados digitais de um aerolevantamento gamaespectrométrico cobrindo seqüência crustal Neoproterozóica da Faixa Seridó (FSe) foram processados e analisados juntamente com medidas de gamaespectrometria terrestre, fotos aéreas e dados geológicos de campo, objetivando a caracterização e o mapeamento litogeofísico de granitos pegmatíticos e campos de pegmatitos associados, bem como de litologias e unidades litoestratigráficas do Grupo Seridó. A interpretação das imagens individuais e ternária dos canais do urânio (eU), do tório (eTh) e do potássio (K), além das razões eU/eTh e eTh/K, possibilitou a identificação de anomalias de tório associadas a metaconglomerados e metarenitos intercalados nos quartzitos da Formação Equador, constituídos de fragmentos e seixos de quartzo, muscovita e concentrações de minerais pesados, dominantemente hematita, ilmenita, monazita, rutilo, titanita e zircão. A análise semiquantitativa em grãos minerais de duas amostras dessas rochas, por microscopia de varredura eletrônica (MEV-EDS), revelou teores máximos de 79,4% de ThO2 e 87,7% de ETR (Ce, La, Nd) em monazitas; 99,2% de TiO2 em ilmenita e rutilo e 1,81 % de Hf02 em zircão. Também foram identificadas anomalias de tório em sedimentos de idade cenozóica na mesma região.Keywords : gamaespectrometria; sensoriamento remoto; placeres rutilo-monazíticos; Província Borborema; Faixa Seridó.ABSTRACTAerial gamma-ray survey data covering Neoproterozoic supracrustal sequences in the Seridó Belt were processed and analyzed together with ground gamma-ray data, air photos and geological data for lithogeophysical characterization and mapping of granitic rocks, related pegmatites fields and lithological units of Seridó Group. Interpretation was based on individual and ternary images of the three radio-elements and the eU/eTh and eTh/K ratios, and allowed the discovery of thorium anomalies associated with coarse-grained metarenites and metaconglomerates facies intercalated with quartzites of the Equador Formation. High contents of iron oxides, ilmenite, monazite, rutile, titanite and zircon were identified by ore microscopy of polished sections in the metaconglomerate's matrix. Semiquantitative scanning electron microscopy (SEM) analyses in minerals of two samples revealed up to 79.4% of Th02 and 87.7% of REE in monazites; up to 99.2% of Ti02 in ilmenite and rutile and up to 1.81 % of HfO2 in zircon. Gamma-ray anomalies due to thorium were also identified in association with sediments of Cenozoic age in the region.Keywords : gamma-ray spectrometry; remote sensing; rutile-monazite placers; Borborema Province; Seridó Belt.

scholarly journals Petrology and dating of the Permian lamprophyres from the Malá Fatra Mts. (Western Carpathians, Slovakia)

2018 ◽  
Vol 69 (5) ◽  
pp. 453-466 ◽  
Author(s):  
Ján Spišiak ◽  
Lucia Vetráková ◽  
David Chew ◽  
Štefan Ferenc ◽  
Tomáš Mikuš ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Granitic Rocks ◽  
Western Carpathians ◽  
Magma Ascent ◽  
Crustal Material ◽  
Calc Alkaline ◽  
Nd Isotopes ◽  
Granitoid Rocks ◽  
Alkaline Lamprophyres

Abstract Calc–alkaline lamprophyres are known from several localities in the Malá Fatra Mountains. They form dykes (0.5–3 m) of varying degree of alteration that have intruded the surrounding granitoid rocks which are often incorporated xenoliths. Clinopyroxenes (diopside to augite), amphiboles (kaersutitic), biotites (annite) and plagioclases are major primary minerals of the dykes, accessory minerals include apatite, ilmenite, rutile, pyrite, chalcopyrite, and pyrrhotite. Apatite has a relatively low F, but increased Cl content compared to typical apatite from lamprophyres or magmatic apatite from granitic rocks in the Western Carpathians. The chemical composition of the lamprophyres indicates their calc–alkaline character, but affinity to alkaline lamprophyres is suggested by the Ti enrichment in clinopyroxene, amphibole and biotite. According to modal classification of the minerals, the studied rocks correspond to spessartite. The differences in the chemical composition of the rocks (including Sr and Nd isotopes) probably result from the contamination of primary magma by crustal material during magma ascent. The age of the lamprophyres, based on U/Pb dating in apatite, is 263.4 ± 2.6 Ma.

Variations in the 87Sr/86Sr Ratio in Lake Waters from Central Sweden

1987 ◽  
Vol 18 (1) ◽  
pp. 21-32 ◽  
Author(s):  
F. E. Wickman ◽  
G. Åberg
Keyword(s):  
Isotopic Ratio ◽  
Granitic Rocks ◽  
Mineral Matter ◽  
86Sr Ratio ◽  
Exchange Reactions ◽  
Hydrologic Processes ◽  
Granitoid Rocks ◽  
Lake Waters ◽  
Stream Waters ◽  
Excellent Tool

The 87Sr/86Sr ratios of lake waters from eastern Central Sweden, a region consisting mainly of 1.7-2.0 × 109 years old granitoid rocks are reported and discussed. The ratios range from 0.722-0.739, and are similar to lake and stream waters in geologically similar areas. The annual variation of the isotope ratio in two small lakes varied in the range of 0.7323-0.7339 and 0.7313-0.7325 respectively, except at ice clearing in spring when the ratio of surface water was lowered by a contribution from melting snow. Small lateral differences also exist in Lake Mälaren, probably because its complex outline hinders complete mixing of its water. The Sr isotopic ratio variations with respect to bedrock geology suggest that a more important influence on the ratio is the mineralogic composition of the Quaternary deposits (mainly till). The great difference between the ratios of rain water (0.709-0.710) and those of rocks in old Precambrian platforms with granitic rocks (0.720 and greater) results in waters (ground, lake and river) with ratios around 0.720-0.740. This means that the 87Sr/86Sr ratio is an excellent tool in studies of hydrologic processes, such as mixing of waters and exchange reactions between water and mineral matter.

Most Granitoid Rocks are Cumulates: Deductions from Hornblende Compositions and Zircon Saturation

2019 ◽  
Vol 60 (11) ◽  
pp. 2227-2240 ◽  
Author(s):  
Calvin G Barnes ◽  
Kevin Werts ◽  
Vali Memeti ◽  
Katie Ardill
Keyword(s):  
Partition Coefficients ◽  
Granitic Rocks ◽  
Granitic Magma ◽  
Intrusive Complex ◽  
Bulk Rock ◽  
Granitoid Rocks ◽  
Modal Layering ◽  
Zircon Thermometry ◽  
Crystal Accumulation ◽  
Zircon Saturation

Abstract Cumulate processes in granitic magma systems are thought by some to be negligible and by others to be common and widespread. Because most granitic rocks lack obvious evidence of accumulation, such as modal layering, other means of identifying cumulate rocks and estimating proportions of melt lost must be developed. The approach presented here utilizes major and trace element compositions of hornblende to estimate melt compositions necessary for zircon saturation. It then compares these estimates with bulk-rock compositions to estimate proportions of extracted melt. Data from three arc-related magmatic systems were used (English Peak pluton, Wooley Creek batholith, and Tuolumne Intrusive Complex). In all three systems, magmatic hornblende displays core-to-rim decreases in Zr, Hf, and Zr/Hf. This zoning indicates that zircon must have fractionated during crystallization of hornblende, at temperatures greater than 800 °C. This T estimate is in agreement with Ti-in-zircon thermometry, which yields a maximum T estimate of 855 °C. On the basis of this evidence, concentrations of Zr in melts from which hornblende and zircon crystallized were calculated by (1) applying saturation equations to bulk-rock compositions, (2) applying saturation equations to calculated melt compositions, and (3) using hornblende/melt partition coefficients for Zr. The results indicate that melt was lost during crystallization of the granitic magmas, conservatively at least as much as 40 %. These results are in agreement with published estimates of melt loss from other plutonic systems and suggest that bulk-rock compositions of many granitic rocks reflect crystal accumulation and are therefore inappropriate for use in thermodynamic calculations and in direct comparison of potentially consanguineous volcanic and plutonic suites.

Iapetus Ocean floor stuffed into a suture zone: xenolith Nd isotopic evidence for Dunnage-equivalent basement in central Newfoundland

1997 ◽  
Vol 34 (10) ◽  
pp. 1392-1400 ◽  
Author(s):  
Brian J. Fryer ◽  
John D. Greenough ◽  
J. Victor Owen
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Granulite Facies ◽  
Suture Zone ◽  
Ocean Floor ◽  
Granitic Rocks ◽  
Bay Area ◽  
Iapetus Ocean ◽  
Depleted Mantle ◽  
Northern Portion

Granulite-facies xenoliths from Late Jurassic alkaline lamprophyres may represent basement to the Dunnage Zone in north-central Newfoundland (Notre Dame Bay area). At 143 Ma the xenoliths had positive εNd values between 0.9 and 4.7. They give Nd depleted mantle model ages around 700 Ma and have trace element and major element compositions reminiscent of oceanic arc-related intermediate volcanic and sedimentary rocks. Their positive εNd values and associated "young" Nd model ages argue against their representing Grenvillian crust. Similarly, Gander Zone basement to the east produced granitic rocks with strongly negative εNd values unlike those of the xenoliths. Positive εNd values for Avalonian granites indicate that the xenoliths could represent Avalon-type basement; however, there are 100–200 km of Gander and Dunnage zone rocks between the xenoiith locality and the Avalon Zone. Early orogenic volcanic rocks and some late orogenic to postorogenic granitic rocks in the central to northern portion of the Gander Zone have positive εNd values, consistent with extraction from a depleted mantle at the same time as material forming the xenoliths. Similarities between the xenolith chemistry and that of early orogenic (Cambrian) arc-related intermediate volcanic rocks of the Dunnage Zone indicate that the xenoliths and basement in the Notre Dame Bay area are composed of Iapetus Ocean floor relics (volcanic or volcanic-rich sedimentary rocks) stuffed into a collisional suture zone during ocean closure.

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