Deformation of Incompletely Crystallized Magma Systems: Granitic Gneisses and their Tectonic Implications

Hibbard, M. J.

doi:10.1086/629148

Cited by 129 publications

(84 citation statements)

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“…Gapais and Barbarin, 1986;Hibbard, 1987;Paterson et al, 1989;Vernon, 2000;Passchier and Trouw, 2005) − In the Yinmawanshan pluton, samples with magmatic and weak solid-state flow evidences occupy more than 75% of the pluton surface (Fig. 9).…”

Section: Microstructures and Petrofabric Analysesmentioning

confidence: 99%

Metamorphic Core Complex dynamics and structural development: Field evidences from the Liaodong Peninsula (China, East Asia)

Charles¹,

Gumiaux²,

Augier³

et al. 2012

Tectonophysics

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International audienceMetamorphic Core Complexes (MCC) constitute remarkable features within wide rifts. Based on analogue and numerical modelling, MCC dynamics and structural development are mainly controlled by first geothermal gradient, second the compositional layering, and after the strain rate and partial melting. In the Late Mesozoic, continental extension occurred in East Asia leading to the development of MCC, magmatism and extensional sedimentary basins. Based on an integrated study (i.e. structural and finite strain analysis, petrofabrics, Anisotropy of Magnetic Susceptibility (AMS) and U/Pb on zircon dating), this paper aims at constraining the tectonic evolution and deformation mechanisms in the South Liaodong Peninsula (NE China). The Gudaoling massif is identified as a "migmatitic" MCC developed from Upper Jurassic (ca. 157-154 Ma) to Early Cretaceous (ca. 128-113 Ma). Intrusion of the Yinmawanshan synkinematic pluton (Early Cretaceous) to the south of the dome marks out the final stages of shearing along the Gudaoling detachment zone and of exhumation of the MCC into the upper crust. The Gudaoling MCC and the Yinmawanshan pluton stay in line with the coeval South Liaodong MCC, to the south, all making a ~ 140x30km wide extensional band formed during a regional E-W to NW-SE crustal stretching. The area shows a bi-phased development with a "slow" and a "fast" stage which correspond to (1) crustal necking and (2) dome amplification/exhumation stages according to published thermo-mechanical modelling results. Finally, the Gudaoling MCC lower unit almost exclusively displays migmatites and anatectic granitoids of Late Jurassic and Early Cretaceous, respectively. Occurrence of partial melting during earlier stages of extension seems controlling the initiation of MCC (as a soft anomaly within lower crust). In East Asia, a regional-scale thermal event, during Jurassic-Cretaceous times, may have significantly reduced the bulk lithosphere strength and locally induced partial melting, emphasizing pervasive deformations and development of a wide rift system

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Section: Microstructures and Petrofabric Analysesmentioning

confidence: 99%

Metamorphic Core Complex dynamics and structural development: Field evidences from the Liaodong Peninsula (China, East Asia)

Charles¹,

Gumiaux²,

Augier³

et al. 2012

Tectonophysics

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“…Barker (1970) showed that granophyric intergrowths could be formed in response to the simultaneous/rapid crystallization of alkali feldspar and quartz from liquid or vapor. The origin of intergrowths would involve volatile-rich liquids in the final processes of crystallization in epizonal environments (Hibbard 1979, & 1987, Hughes 1982. These magmatic conditions are compatible with underformed granitoids with restricted granophyric textures that are likely related to the presence of aplite dikes formed from sudden replacement of H 2 O-saturated phases, due to pressure loss that accelerated the nucleation rates (Hibbard 1995).…”

Section: Petrological Considerationsmentioning

confidence: 99%

Field and petrographic data of 1.90 to 1.88 Ga I- and A-type granitoids from the central region of the Amazonian Craton, NE Amazonas State, Brazil

Valério

Macambira

Souza

2012

RBG

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The SW Presidente Figueiredo district, which is located in the northeastern Amazonas State of the central Amazonian Craton, Brazil, consists of 1890 to 1898 Ma I-type granitoids (Terra Preta Granite, Água Branca Suite), A-type hornblende-bearing syenogranites (Canoas Syenogranite, Mapuera Suite), felsic to intermediate volcanic rocks (Iricoumé Group), and 1883 to 1889 Ma rapakivi granites (São Gabriel Granite, Mapuera Suite) and related rocks (quartz-gabbroanorthosite and diorite), in addition to Castanhal quartz-monzonite, mylonites, and hornfels. The quartz-diorite facies of Terra Preta Granite were formed by mingling processes between a synplutonic quartz-gabbro dike and a hornblende granodiorite. Partially assimilated globules of Canoas hornblende-bearing syenogranite and their clear contacts with Terra Preta hornblende granodiorite suggest that Canoas Syenogranite is slightly younger than Terra Preta Granite. Canoas Syenogranite xenoliths inside São Gabriel Granite show that the granite is younger than the Canoas Syenogranite. New geologic and petrographic evidence improve the petrological understanding of these rocks and suggest that, in addition to fractional crystallization, assimilation and magma mingling played a role, at least at the local scale, in the evolution and compositional variation of the plutons. Such evidence is found in Terra Preta Granite mingled quartz-diorite, felsic material associated with the Canoas Syenogranite and in the intermediate microgranular enclaves, which exhibit primary biotite in hornblende-bearing rocks, plagioclase dissolution, corrosion of feldspars rims, alkali feldspar mantles, second apatite generation, and high xenocrystal contents in intermediate enclaves formed from the fragmentation of mafic intrusions. Petrographic analyses show that a deformational event recorded in the western part of the study area (with progressive deformation from E to W) is dated between the 1.90 Ga postcollisional magmatism and the intrusions of the São Gabriel Granite and related mafic/intermediate rocks (intra-plate). However, it is extremely necessary to obtain absolute ages for this metamorphic event.Keywords: field data; petrography; I-and A-type granitoids; lithostratigraphy; NE Amazonas State. RESUMO Dados de campo e petrográficos de granitoides dos tipos I e A de 1,90 a 1,88 Ga da região central do Cráton amazônico, NE do Estado do Amazonas, Brasil. O SW do município de Presidente Figueiredo, localizado noEstado do Amazonas, Nordeste do Cráton Amazônico Central, Brasil, hospeda granitoides do tipo I de idade entre 1890 a 1898 Ma (Terra Preta Granito, Suíte Água Branca), hornblenda-sienogranitos do tipo A (Sienogranito Canoas da Suíte Mapuera), rochas vulcânicas ácidas à intermediárias (Grupo Iricoumé) e granitos rapakivi de idades entre 1883 a 1889 Ma (Granito São Gabriel da Suíte Mapuera), e rochas afins (quartzo-gabro-anortosito e diorito), além de quartzo-monzonito Castanhal, milonitos e hornfels. A fácies quartzo-diorito do granito Terra Preta foi formada por proces...

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“…Hibbard (1979Hibbard ( , 1987 suggested that all myrmekite in mesoscopically undeformed granites is due to crystallization of water-saturated, pressure-quenched magma, based on his observation of crystal faces and zoning in the plagioclase of some myrmekitic aggregates and on his general model of late magmatic crystallization in granites. This is the opposite of conventional hypotheses of replacement of K-feldspar in the solid state (Phillips, 1980;Vernon et al, 1983), requiring that myrmekite in deformed granites is due to crystallization of small amounts of water-saturated magma in a largely crystallized rock, in response to 'micro pressure-quenching 1 during deformation.…”

Section: -3-3 Myrmekitementioning

confidence: 99%

Geochimie et mineralogie des granites de la region de Hetai province de Guangdong Chine meridionale =

Yang¹

1993

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The Hetai Area, located in the western Guangdong Province of South China, has been affected by four orogenies, from the Caledonian (Early Paleozoic) to the Yanshanian (Late Mesozoic). Two major northeast trending faults, the Guangning-Loudin and the Wuchuan-Sihui, characterized by wide deformation zones, traverse the region. Granitic rocks, which cover about half the surface area, are related to each of the four orogenies. Previous regional studies have been premised on the importance of in situ granitization of Precambrian strata for the formation of the older granitic rocks as well as the formation of the Hetai gold deposits.This study discusses the genesis and evolution of ten granitic intrusions from the Hetai area based on their petrography, mineralogy and geochemistry. The granites of the Hetai Area are defined as "older granites" (Caledonian and Hercynian granites) and "younger granites" (Indosinian and Yanshanian granites) for comparison. Detailed field and microscopic observations show that all granitic rocks have a magmatic flow foliation. This foliation is overprinted by various degrees of solid-state deformation in the older (Caledonian and Hercynian) granite bodies.The geochemical analyses of granites also distinguish them into different types. The older granites are characterized mainly by peraluminous chemistry (A/CNK>1.05), high LILE/HFSE, HREE/LREE and a negative Eu anomaly, whereas the younger granites are characterized by slightly peraluminous and metaluminous chemistry (A/CNK<1.05), a significant change of LILE/HFSE, HREE/LREE and a negative Eu anomaly ranging from low to high with the calc-alkaline -> alkaline evolution of the magma. Comparison of the granites of the Hetai Area to those of well studied world areas by selected geochemical diagrams such as (Nb+Ta) vs (V+Sc) and Rb/Sr shows that the older granites are similar to S-type granite, but the younger granites are coincident with I-type and A-type (?) granites.Au contents are higher in younger granites than those in older granites. Au distributions in different type granites of the Hetai Area suggest that the granites derived Chemical analyses of biotite show that biotites from the older granites contain high FeO (>22%) and A1 2 C>3(>15%) but low MgO (<8%), TiO 2 (<3%) and SiO 2 (<36%), whereas those from the younger granites have high MgO (>8%), TiO 2 (>3%) and SiO 2 (>36%) but low FeO (<22%) and A1 2 O3 (<15%). In general, the biotites from older evolution of the different granites shows a geotectonic evolution from the peraluminous collision-type granites to mafic and calc-alkaline subduction-type granites finally to alkaline extension-type granites in the Hetai Area. IV RESUMECette thèse porte sur la genèse et l'évolution des roches granitiques de la région de Hetai et sur leurs relations possibles avec la minéralisation aurifère. Cette région de la Chine Méridionale est située à l'ouest de la Province de Guangdong. La Chine Méridionale a une histoire géotectonique complexe et l'étude des granites de la région de Hetai, qui...

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Deformation of Incompletely Crystallized Magma Systems: Granitic Gneisses and their Tectonic Implications

Cited by 129 publications

References 27 publications

Metamorphic Core Complex dynamics and structural development: Field evidences from the Liaodong Peninsula (China, East Asia)

Metamorphic Core Complex dynamics and structural development: Field evidences from the Liaodong Peninsula (China, East Asia)

Field and petrographic data of 1.90 to 1.88 Ga I- and A-type granitoids from the central region of the Amazonian Craton, NE Amazonas State, Brazil

Geochimie et mineralogie des granites de la region de Hetai province de Guangdong Chine meridionale =

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