Geologia e evolução petrogenética do Maciço Alcalino de Itatiaia, MG-RJ

Rosa, Pedro Augusto da Silva

doi:10.11606/t.44.2018.tde-10072018-152847

Cited by 6 publications

(12 citation statements)

References 82 publications

(171 reference statements)

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“…Due to the larger number of outcrops described and better exposure and geomorphology, mapping is more detailed in the central part of the massif. Geochemical, isotopic, mineral chemical and geochronological data (Rosa 2017) were also considered in the individualization of units. Country rock units were compiled from Trouw et al (2003) and Heilbron et al (2016).…”

Section: Methodsmentioning

confidence: 99%

“…This magma pulse is similar to the SE-S cluster, but the subsequent one evolved with an increase in silica content and, in some way, crossed the thermal barrier of nepheline-quartz to the silica-oversaturated types. Isotopic data shows crustal contamination in quartz-bearing rocks (Brotzu et al 1997, Rosa 2017. The first C-S intrusions are concentric, but QzASF-II resumed migration to NW.…”

Section: Emplacement Stagesmentioning

confidence: 99%

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Nepheline syenites to syenites and granitic rocks of the Itatiaia Alkaline Massif, Southeastern Brazil: new geological insights into a migratory ring Complex

Rosa

Ruberti

2018

Braz. J. Geol.

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The Itatiaia Alkaline Massif comprises some of the largest meso-cenozoic alkaline igneous occurrences in Brazil, covering over 215 km 2 between the states of Minas Gerais and Rio de Janeiro. It appears as an elongated, 30-km long and 4.5-11.5-km wide SE-NW-trending body emplaced along accommodation zones of the Continental Rift of Southern Brazil, intruding metapelites, orthogneiss and granites of the Brasília and Ribeira fold belts. New data and geological mapping suggest that the massif evolved from a migratory magmatic center manifested as ring structures and successive moon-shaped intrusions from SE to NW in three sectors of distinct lithological and geomorphological characteristics: Southeastern, Central and Northwestern. The lithological variants in the three sectors present themselves as discrete intrusive bodies, comprising feldspathoid-bearing and quartz-bearing syenites, porphyritic to breccioid trachytes, granite, monzonite, gabbro and trachybasalt, which can be grouped into 21 units. These rocks occur in five petrographical sets: plagioclase-free nepheline syenites, plagioclase-bearing nepheline syenite and pulaskites, nordmarkite-granite series, anti-rapakivi associations and basic rocks. Sin-to tardi-plutonic dykes of nephelinites, phonolites, trachytes and rhyolites are also present.

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Section: Methodsmentioning

confidence: 99%

Section: Emplacement Stagesmentioning

confidence: 99%

Nepheline syenites to syenites and granitic rocks of the Itatiaia Alkaline Massif, Southeastern Brazil: new geological insights into a migratory ring Complex

Rosa

Ruberti

2018

Braz. J. Geol.

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“…While some alkali basalt and lamprophyres present potassic affinity (which prevails in the Serra do Mar Alkaline Province), others are of sodic affinity and belong to a strongly silica-undersaturated series (Azzone et al 2018). The phonolitic tephrite dike shows ultrapotassic affinity (K 2 O > 3 wt%, MgO > 3wt%, and K 2 O/ Na 2 O > 2 wt%; Foley et al 1987); quite unusual in the province (Garda 1995, Valente 1997, Marins 2012, Rosa 2017. Chondrite-normalized REE patterns are sub-parallel, with an abundance of light over heavy elements.…”

Section: Whole-rock Geochemistrymentioning

confidence: 99%

Mafic macrocrysts of ultrabasic alkaline dikes from the Mantiqueira Range, SE, Brazil: tracers of a complex plumbing system

et al. 2020

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Macrocryst assemblages of porphyritic alkaline dikes in the Mantiqueira range (SE Brazil) are mainly composed of clinopyroxene and olivine with different origins. Based on petrographic features, mineral chemistry, and equilibrium relationships with the host liquid, those macrocrysts are classified as xenocrysts, antecrysts, and phenocrysts. Described xenocrysts are mantle olivine, Cr-diopside cores compatible with garnet-bearing mantle facies, green-core clinopyroxene cores compatible with lower crust, and enstatite cores mantled by clinopyroxene, all reported for the first time in this region. Two contrasting types of clinopyroxene antecrysts prevail among the macrocryst cores (both occurring in the same samples and presenting corrosion and sieve textures): primitive colorless diopside and more evolved green-core clinopyroxenes. In the studied rocks, green clinopyroxene zones mantling colorless diopside cores (and vice-versa) are also found. Diopside-and green-cores antecrysts have similar compositions to those from mafic and felsic alkaline melts, respectively. Phenocrysts are mainly related to Ti-augite overgrowths, mantling all other types. Mixing-model curves between mafic and felsic alkaline equilibrium liquids calculated from clinopyroxene antecrysts indicate a hybrid origin for the host matrix. The macrocryst populations of the studied dikes are indicative of a complex plumbing system, recording several processes of an open-system magmatic evolution.

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“…No entanto, Marins (2012), investigando processos de diferenciação magmática com diques em sete complexos sieníticos da PASM, propõe que apenas Moro Redondo, Gericinó-Mendanha e Passa Quatro seriam cogenéticos a magmas progenitores máficos por processos de cristalização fracionada. Processos de assimilação durante a cristalização fracionada são indicados nas intrusões sieníticas Ilha de Cabo Frio e Itatiaia, no maciço máfico-ultramáfico alcalino Ponte Nova e nos enxames de diques miaskíticos (Na 2 O+K 2 O/Al 2 O 3 em proporção molecular <1 é miaskítico, >1 é agpaítico, conforme o índice de alcalinidade/agpaítico, IA, de Sörensen, 1974) do litoral do estado do Rio 6 7 de Janeiro (Valente, 1997;Brotzu et al, 1997, Motoki et al, 2013Rosa, 2017). A mistura entre magmas básico-ultrabásicos fortemente insaturados em sílica e fonolitos agpaíticos foi observada nos diques do litoral do Rio de Janeiro (Valente, 1997).…”

Section: Rochas Alcalinas Cretáceas Da Serra Da Mantiqueira Pasmunclassified

“…Brechas magmáticas, estruturas anelares e minerais exóticos são característicos a tais litotipos félsicos (Alves et al, 1992;Brotzu et al, 1989Brotzu et al, , 1992Brotzu et al, , 1997Brotzu et al, , 2005Atencio et al, 1999;Enrich et al, 2005Enrich et al, , 2009Marins, 2012;Lopes, 2015;Melluso et al, 2017;Rosa, 2012Rosa, , 2017Rosa & Ruberti, 2018).…”

Section: Rochas Alcalinas Cretáceas Da Serra Da Mantiqueira Pasmunclassified

Antecristais e xenocristais máficos em diques ultrabá¡sicos de tendência alcalina da Serra da Mantiqueira (SP)

Silva¹

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Lopes, J.C.S., 2018, Mafic antecrysts and xenocrysts in alkaline ultrabasic dykes of the Mantiqueira range (SP) [Master's Thesis], São Paulo, Instituto de Geociências, Universidade de São Paulo, 186p. Weakly to strongly silica-undersaturated mafic alkaline dike series occur nearby Santo Antonio do Pinhal (SP) and Campos do Jordão (SP) in a restricted area of the Mantiqueira range, SE Brazil. These are intrusive in the Precambrian crystalline basement (south of the Brasília orogen) and in the Ponte Nova mafic-ultramafic alkaline massif. These are Cretaceous rocks and are grouped as part of the Serra do Mar alkaline province. In the majority, the dikes are classified as alkaline basalts and alkaline lamprophyres. Are porphyritic, with the macrocryst population having clinopyroxene and olivine as main phases. Subordinatedly, kaersutite, and occasionally, phlogopite, enstatite, magnetite, spinel and plagioclase were found. These macrocrysts present desequilibrium textures, such as sieve and embayment, combined with complex zoning styles, which indicate a open-system magmatic evolution. The study involves: (1) detailed petrographic analyses by optical microscopy and scanning electron microscopy, (2) quantitative punctual analyses of major and minor elements by electron microprobe and trace element by laser ablation -inductively coupled plasma mass espectrometry (LA-ICP-MS) in different horizons of the main macrocrystic phases, and (3) whole-rock geochemistry by X-ray fluorescence and ICP-MS. These determinations were collected focusing in the determination of the genesis of each population of zoned crystals. From the obtained compositions, mass balance calculations were done to exclude the macrocryst influence in the bulk compositions of the bodies and to have a compositional estimative of the melts, represented by the fine-grained to aphanitic matrices of these rocks. The crystalline zones of macrocrysts in equilibrium with the calculated melts were defined using the Mg-Fe exchange equilibrium constant between minerals and liquid, -.The equilibrium relationships allowed the designation genetic meanings to the the crystalline zones, being these classified as xenocrysts, antecrysts and phenocrysts. The first two types (in textural and chemical disequilibrium with the matrices) were captured and/or recycled from an early magmatic environment, allowing to access the former magmatic processes during the

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Geologia e evolução petrogenética do Maciço Alcalino de Itatiaia, MG-RJ

Cited by 6 publications

References 82 publications

Nepheline syenites to syenites and granitic rocks of the Itatiaia Alkaline Massif, Southeastern Brazil: new geological insights into a migratory ring Complex

Nepheline syenites to syenites and granitic rocks of the Itatiaia Alkaline Massif, Southeastern Brazil: new geological insights into a migratory ring Complex

Mafic macrocrysts of ultrabasic alkaline dikes from the Mantiqueira Range, SE, Brazil: tracers of a complex plumbing system

Antecristais e xenocristais máficos em diques ultrabá¡sicos de tendência alcalina da Serra da Mantiqueira (SP)

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