Jean‐Luc Bouchez

Observatoire Midi-Pyrénées

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Anne Nédélec

Géosciences Environnement Toulouse

Hervé Diot

La Rochelle Université

Adolphe Nicolas

Géosciences Montpellier

Arnaud Pêcher

Laboratoire Bordelais de Recherche en Informatique

Ricardo I.F. Trindade

Universidade de São Paulo

Gérard Gleizes

Centre National de la Recherche Scientifique

Jean‐Louis Paquette

Laboratoire Magmas et Volcans

Michel de Saint Blanquat

Institut de Recherche pour le Développement

Rigobert Tchameni

University of Ngaoundéré

Daouda Dawaï

Géosciences Environnement Toulouse

Cooperative Institutions

Centre National de la Recherche Scientifique

Université Toulouse III - Paul Sabatier

Institut de Recherche pour le Développement

Université de Toulouse

Géosciences Environnement Toulouse

Observatoire Midi-Pyrénées

Institut des Sciences de la Terre

Nantes Université

Université de Montpellier

Universidad de Zaragoza

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Granites

Anne Nédélec Jean‐Luc Bouchez Peter Bowden

Abstract Granites are emblematic rocks developed from a magma that crystallized in the Earth's crust. They ultimately outcrop at the surface worldwide. This book, translated and updated from the original French edition Pétrologie des Granites (2011) is a modern presentation of granitic rocks from magma genesis to their crystallization at a higher level into the crust. Segregation from the source, magma ascent and shapes of granitic intrusions are also discussed, as well as the eventual formation of hybrid rocks by mingling/mixing processes and the thermomechanical aspects in country rocks around granite plutons. Modern techniques for structural studies of granites are detailed extensively. Granites are considered in their geological spatial and temporal frame, in relation with plate tectonics and Earth history from the Archaean eon. A chapter on granite metallogeny explains how elements of economic interest are concentrated during magma crystallization, and examples of Sn, Cu, F and U ore deposits are presented. Mineralogical, petrological, physical and economical aspects are developed in a succession of 14 chapters comprising a large number of high-quality illustrations. Selected examples used for the figures are derived from every continent. Special 'info boxes' discuss topics for those wishing to deepen the subject.

Metallogeny

Outcrop

10.1093/acprof:oso/9780198705611.001.0001

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Citations (35)

Genesis of hybrid granitoids: mingling and mixing

Oxford University Press eBooks (2015)

Anne Nédélec Jean‐Luc Bouchez

Abstract Mafic enclaves are common in granitic hosts. Magma mingling is controlled by the effective viscosity (hence the crystal load) of both magmas. Evidence of mingling or mixing events can be found in plagioclase crystals where complex internal zoning is present. Hybrid rocks plot along mixing lines in Harker diagrams. Mingling, and eventually mixing, result from either the transfer of a granitic liquid into a mafic magma which therefore is contaminated, and/or the mechanical dispersion of the mafic magma into the granitic host provided that the viscosities of these two phases are alike. Mingling/mixing may take place at any level in the continental crust. Sections cover field observations, the influence of viscosity, the characteristics of hybrid rocks, processes involved in magma mingling and mixing, and the locations of hybrid magma formation.

Igneous differentiation

Felsic

Magma chamber

10.1093/acprof:oso/9780198705611.003.0004

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Citations (2)

Shape anisotropy versus magnetic interactions of magnetite grains: Experiments and application to AMS in granitic rocks

Geophysical Research Letters (1995)

Vincent Grégoire Michel de Saint Blanquat Anne Nédélec Jean‐Luc Bouchez

The magnetic fabric of ferromagnetic granitic rocks results from both the shape preferred orientation of individual magnetite grains and their distribution anisotropy through magnetic interactions between neighbouring grains. Measurement of the low‐field magnetic anisotropy of single multi‐domain magnetite grains shows a linear correlation between their magnetic anisotropy degree and their aspect ratio. Interactions between two elongated grains were studied experimentally using two types of grain arrangement: an “aligned” configuration and a “side‐by‐side” configuration. For a distance between the grain centers equal to approximately twice the average grain size, the magnetic susceptibility and its anisotropy are enhanced in both configurations, and the direction of k max , the easiest magnetization axis, is stable in the “aligned” configuration, whereas it rotates toward an orthogonal direction in the “side‐by‐side” configuration. Depending on the distribution of the interacting magnetite grains, magnetic interactions may therefore either increase the whole‐rock anisotropy magnitude, or reduce it as in the given example of the granitic rocks from Madagascar.

Single domain

10.1029/95gl02797

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Citations (111)

Magnetic fabrics and microstructures of the post-collisional aegirine-augite syenite Triunfo pluton, northeast Brazil

Journal of Structural Geology (1997)

Carlos José Archanjo Jean‐Luc Bouchez

Lineation

Diorite

10.1016/s0191-8141(97)00008-4

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Citations (26)

Segregation of granitic melts

Oxford University Press eBooks (2015)

Anne Nédélec Jean‐Luc Bouchez

Abstract Viscosity of the melt as well as the melt wetting properties influence the segregation rate of melt from its source called the protolith. Dynamic partial melting experiments show that segregation takes place mainly via fractures that develop in the protolith at melt percentages that can be very low. The formation of disequilibrium melts, with respect to their trace element contents, is a likely consequence of fast segregation rates compared with geological phenomena. Sections deal with the viscosity of granitic melts, melt behaviour during partial melting, progressive partial melting experiments, melt distribution in migmatites and migmatites in the field. The role of the filter-press mechanism is highlighted.

Granitic rock

10.1093/acprof:oso/9780198705611.003.0003

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Secondary fabrics revealed by remanence anisotropy: methodological study and examples from plutonic rocks

Geophysical Journal International (2001)

Ricardo I.F. Trindade Jean‐Luc Bouchez Olivier Bolle Anne Nédélec Anne Peschler

The fabric of fine-grained magnetite is isolated by partial remanence anisotropy (pAAR) measurements that combine cycles of anhysteretic remanence acquisition and alternating frequency (AF) tumbling demagnetization of the low-coercivity fraction. Since remanence intensities of the most coercive, fine-grained magnetite are very weak (rarely exceeding 10 per cent of the measured remanence in the studied samples), a methodological study is presented that defines optimal measurement schemes and examines the role of gyroremanence and background remanences due to hard remanence carriers. This procedure is applied to some 'reddened' granites from Tana (Corsica) and Wichita (Oklahoma) and to the Tellnes ilmenite-rich norite (Norway). The pAAR fabrics for fine-grained magnetites are compared to the fabrics of the coarse-grained, primary magnetite grains, as shown by both the anisotropy of magnetic susceptibility (AMS) and the remanence anisotropy of the low-coercivity fraction. In Tellnes, fine-grained magnetite is believed to be of secondary origin; this is strongly suggested by the correlation between the pAAR fabrics and the orientations of sets of microfractures decorated by oxides. In the 'reddened' granites, although no direct correlation between pAAR fabrics and microstructures could be evidenced, the comparison between unaltered specimens and hydrothermally altered ones reveals changes in magnetic properties and fabrics that are ascribable to this secondary geological process.

Rock magnetism

Stoner–Wohlfarth model

10.1046/j.0956-540x.2001.01529.x

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Citations (45)

Petrology of the late Pan-African Guider syenite pluton (Cameroon): Implications for magma genesis and emplacement

Journal of African Earth Sciences (2022)

Daouda Dawaï Alliance Nicaise Saha Fouotsa Aboubakar Bello Rigobert Tchameni Anne Nédélec

Diorite

Fractional crystallization (geology)

Petrogenesis

Magma chamber

10.1016/j.jafrearsci.2022.104519

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Citations (3)

Principes de tectonique

HAL (Le Centre pour la Communication Scientifique Directe) (2018)

Adolphe Nicolas Jean‐Luc Bouchez

Ce manuel est consacre aux outils de la geologie structurale et de la geophysique. L’accent est mis sur les aspects microscopiques et macroscopiques de la deformation des roches, sur les etats de contraintes a toutes echelles et sur les deplacements verticaux et horizontaux. Les chapitres sont courts, le style est direct et de nombreuses figures sont originales. Le livre se termine par une serie d’exercices corriges portant sur quelques techniques importantes utilisees en tectonique ainsi que sur des applications et sujets d’examen ou de concours. Il s’adresse aux etudiants en Licence 3 et en master de SVT, aux candidats aux concours de l’enseignement ainsi qu’aux eleves des ecoles d’ingenieurs. Sommaire 1. Deformation et contrainte – 2. Deformation fragile – 3. Empreintes de la deformation fragile – 4. Deformation plastique a l’etat solide et microstructures – 5. Empreintes de la deformation plastique a l’etat solide – 6. Fabriques (de forme, de reseau) et cinematique – 7. Structures et fabriques magmatiques – 8. Rheologie de la lithosphere et etats de contraintes – 9. Deplacements horizontaux et verticaux – 10. Aspects techniques de la tectonique – 11. Exercices – Glossaire – References bibliographiques – Index.

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Citations (22)

Microstructures and magnetic fabrics of the Ngaoundéré granite pluton (Cameroon): Implications to the late-Pan-African evolution of Central Cameroon Shear Zone

Journal of African Earth Sciences (2017)

Daouda Dawaï Rigobert Tchameni Jérôme Bascou Salomon Awe Wangmene Périclex Martial Fosso Tchunte

Lineation

Porphyritic

Transpression

Silicic

Strain partitioning

10.1016/j.jafrearsci.2017.02.027

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Citations (24)

Le quartz et la cinématique des zones ductiles

Jean‐Luc Bouchez

Ce travail est voue a l'etude de comportement plastique du quartz dans les tectonites, par l'examen au microscope optique des microstructures des sous-structures et des orientations preferentielles de forme et de reseau. en vue d'une analyse cinematique de ces tectonites. Trois zones de grande deformation appelees zones ductiles apportant chacune des contributions specifiques. sont choisies comme support de l'etude : l'axe Angers- Lanvaux etudie dans la region d'Angers (Massif Armoricain), le Grand Chevauchement Central himalayen au Nepal Central et la zone ductile de Maydan (Afghanistan). Le caractere cinematique le plus constant dans ces zones est un ecoulement plastique subparallele a une lineation majeure d'allongement. horizontale ou faiblement pentee ; l'echauffement plastique developpe par cet ecoulement peut rendre compte, au moins partiellement, du metamorphisme de position lie a ces zones, ainsi que le montre un modele thermique schematique. Le probleme de l'initiation et de la croissance d'une zone ductile est aborde a l'aide d'un modele base sur l'existence d'une heterogeneite locale de la loi de deformation d'une plaque soumise a un couple de cisaillement constant. Un modele general de zone ductile a plan d'ecoulement subverti cal (par opposition aux grands chevauchements) tente d'integrer les caracteristiques communes a ces zones.

Tectonite

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Citations (16)