Jean-Luc Bouchez

• Doctorat d'Etat -PhD- (1978)
• Professor Emeritus at Toulouse University

Stratoid granites constitute a major feature of the Precambrien basement of Madagascar. A detailed structural study was carried out NNW of Antananarivo. New zircon isotopic data on a typical alkaline granite ascertain their Panafrican age (585 Ma). The sheets of granites metric to kilometric of thickness, are interlayered with migmatitic gneisses a...

The so-called Henkel's plot (1976) allows relating density and magnetic susceptibility of rocks. In this work we focused on three paramagnetic Pyrenean granites from the Mont Louis-Andorra, Maladeta and Marimanha granitic plutons. In total, 128 sites with 310 density measurements and > 2600 susceptibility readings cover the main range of variabilit...

In this work we establish reliable correlations between density and magnetic susceptibility in three paramagnetic granites from the Pyrenees. In total, 128 sites (310 density measurements and >2600 susceptibility ones) were studied in the Mont Louis-Andorra, Maladeta and Marimanha granitic plutons covering the main range of variability of magnetic...

The Guider pluton, located in the eastern border of the North-West Cameroon domain close to the Mayo-Kebbi domain, is one of the rare high potassic magmatic bodies in the northern portion of Central African Orogenic Belt. Previously studied for its structural and geochronological aspects, its petrogenesis remained uncertain. Petrography, mineralogy...

Ce manuel est consacré aux outils de la géologie structurale et de la géophysique. L’accent est mis sur les aspects microscopiques et macroscopiques de la déformation des roches, sur les états de contraintes à toutes échelles et sur les déplacements verticaux et horizontaux.Les chapitres sont courts, le style est direct et de nombreuses figures son...

In this paper we report on a compilation of more than 2,200 sites (more than 10,000 individual measurements) where anisotropy of magnetic susceptibility (AMS) was studied in granite from the Variscan Pyrenees. The standardization and homogenization of this information has allowed us to produce three maps that synthesize all the information related...

Teofilândia granitoids are representative of the Paleoproterozoic plutonic rocks, which intruded the Serrinha block, an Archean crustal fragment of the Sao Francisco Craton (Bahia, Brazil). Three plutons were emplaced, the Teofilândia granodiorite, the Barrocas trondhjemite and the Santa Rosa granite, respectively dated at 2130, 2127 and 2073 Ma. T...

The so-called stratoid granites are sheet-like granites emplaced as conformable sills in the Precambrian basement of central Madagascar. Most of them have A-type affinities (Nédélec et al. 1995). They are everywhere characterized by the same structural pattern evidencing two stages of deformation. The first one (foliations mildly dipping to the wes...

This book - translated, edited, and updated from the original French edition Pétrologie des Granites published by Vuibert in 2011 - gives a modern presentation of granitic rocks, or granites, from magma genesis to their emplacement into the crust and their crystallization. Mineralogical, petrological, physical, and economical aspects are developed...

The changes in magnetic mineralogy due to the hydrothermal alteration of A-type granitic rocks has been thoroughly investigated in samples from the granite of Tana (Corsica, France), and compared with other A-type granites: Meruoca (NE Brazil), Bushveld (South Africa), Mount Scott (Wichita Mountains, Oklahoma, USA) and the stratoid hypersolvus gran...

S U M M A R Y The intrusion mechanism and internal structure of sills are still under debate. We present a detailed magnetic study, including anisotropy of magnetic susceptibility and rock magnetic analyses of a Cretaceous (94 Ma), 7-m-thick sill from the Lusitanian Basin in Portugal, the Foz da Fonte sill. The results, from both the top surface an...

The magnetic fabric and grain size of sand deposits emplaced during the 2011 Tohoku-oki tsunami were studied in five trenches along a 1800 m long shore-normal transect on the Sendai plain as well as in a near shore sedimentary infill of a scour depression. The magnetic susceptibility in all deposits is due to ferromagnetic minerals (mainly magnetit...

The small Guider pluton (70 km(2)) in-between the cities of Maroua and Garoua (north Cameroon) is one of the quartz-syenite bodies that intrude Pan-African orthogneisses, and that are aligned along the western side of the NNE-directed Poli-Lere volcano-sedimentary corridor. The Guider syenite is here studied for its internal structures, using field...

The intrusion mechanism and internal structure of sills are still not well understood. Here we present a detailed and high resolution AMS study of a Cretaceous sill from Portugal in order to better constrain the magmatic flow along a vertical profile. We also conducted rock magnetic analysis in order to identify the nature and grain size of magneti...

The ∼136 Ma, NW–SE elongate Shir-Kuh pluton is one of the most poorly understood geological feature of Central Iran. It is composed of peraluminous rocks, corresponding to ilmenite-bearing S-type granites compositionally ranging from granodiorites to leucogranites. These rocks show a continuum in their chemistry attributed to progressive differenti...

Les granites sont les roches emblématiques de la croûte continentale. Issus d'un magma cristallisé en profondeur, ils affleurent aujourd'hui en surface sur tous les continents et témoignent de l'histoire géologique passée. Ce manuel traite des granites au sens large, autrement dit de tous les granitoïdes, de la genèse à la mise en place et à la cri...

En partenariat avec : SGF (Société Géologique de France) (/auteur/sgf-societe-geologique-de-france) 2011-320 pages Les granites sont les roches emblématiques de la croûte continentale. Issus d'un magma cristallisé en profondeur, ils affleurent aujourd'hui en surface sur tous les continents et témoignent de l'histoire géologique passée. Code ISBN :...

The Liptako area consists of narrow greenstone belts bordered by tonalite, trondhjemite and granodiorite (TTGs) batholithes. These TTGs have been dated at 2.21 Ga (Castaing et al., 2003). Both greenstone belts and TTGs contain biotite granites emplaced around 2.1 Ga (Castaing et al., 2003). In the field, the TTGs are regularly foliated while the st...

The Jurassic Shir-Kuh granitoid batholith in Central Iran intrudes Lower Jurassic sandstones and shales. The batholith consists of three main facies: (i) a granodioritic facies to the north; (ii) a monzogranitic facies spread throughout the batholith; and (iii) a leucogranitic facies along the northwestern margin. The granodiorites are composed mai...

The Urumieh complex, to the north of the Sanandaj–Sirjan zone (NW Iran), belongs to a plutonic arc that took place above the northeastward dipping subduction of Arabia under Iran during Late Cretaceous times. Seven granitoid bodies occupying an area of ∼300 km2 can be sorted into three suites. According to the isotope chronology study of Ghalamghas...

The Urumieh plutonic complex is located in the northwestern part of the Sanandaj–Sirjan zone (Iran). The Urumieh plutonic complex comprises three components, i.e. a dioritic suite, a granitic suite consisting of biotite-bearing granites, and younger stocks, i.e. an alkaline suite (alkali syenite and alkali granite) and a muscovite-bearing granite....

The Fada N′Gourma area in Burkina Faso is underlain by Paleoproterozoic rocks that make the northeastern West-African Craton. This region is composed of NE-trending volcano-sedimentary belts and foliated tonalites, affected by several shear zones. A generation of younger, ∼2100Ma-old, non-foliated biotite-bearing granites intrudes the former rock u...

The abundant paleomagnetic and AMS information in the Pyrenees (and their foreland basins; Aquitaine and Ebro) motivated the development of databases in 2003 in the frame of an INTERREG III project (Pyrenean Network, CTP). In this paper we describe the different databases, the methodology used (sources, layers, display) and future developments. The...

The abundant paleomagnetic and AMS information in the Pyrenees (and their foreland basins; Aquitaine and Ebro) motivated the development of databases in 2003 in the frame of an INTERREG III project (Pyrenean Network, CTP). In this paper we describe the different databases, the methodology used (sources, layers, display) and future developments. The...

This article describes a new kind of sample holder for the automatic (KLY "S" and MFK "A") Kappabridge models, capable of obtaining the full AMS (Anisotropy of Magnetic Susceptibility) tensor of a rock specimen in one single manipulation. Inside this holder, a standard-sized, cylindrical (diameter: 2.5cm, height: 2.2cm) specimen tumbles simultaneou...

In order to test the feasibility of nuclear waste storage, Andra, the French radioactive waste management agency, gave us the opportunity to study preserved specimens of Jurassic clay-rich rocks from eastern Paris Basin. These rocks, deposited during the Callovian and beginning of the Oxfordian, are dark- to light-grey marls that consist mainly in...

The Jurassic Shah-Kuh granite pluton was emplaced in the northeastern part of the Lut Block (Eastern Iran) while this block was a part of the active margin under which the Tethys ocean, that separated Arabia from Central Iran, was subducting. Since this time, the Lut Block has rotated and migrated northward up to its present position. This structur...

A set of regularly spaced specimens, made up of dark-coloured calcareous argillites, were collected from borehole-cores from the Early Callovian up to the Middle Oxfordian, in the eastern Paris Basin. These specimens have been studied for their magnetic susceptibility, natural and artificial remanence, and for their anisotropy of magnetic susceptib...

The relationship between mineral fabric and pore network geometry anisotropy is studied for representative clay-rich lithologies from the Callovo-Oxfordian formation of the Andra Laboratory (Paris Basin, France), sampled from the oblique borehole-core #EST211. Comparisons between standard magnetic fabric measurements (AMS) that give the mineral fab...

The magnetic fabrics and microstructures of the Variscan granite pluton of Bodmin (Cornwall) have been studied. Its low susceptibility magnitude, consistent with its lack of magnetite, comes from biotite and tourmaline. As the magneto-crystalline behaviour of tourmaline is 'inverse' compared with that of the phyllosilicates, the magnetic fabric was...

Besides granites of the ilmenite series, in which the anisotropy of magnetic susceptibility (AMS) is mainly controlled by paramagnetic minerals, the AMS of igneous rocks is commonly interpreted as the result of the shape-preferred orientation of unequant ferromagnetic grains. In a few instances, the anisotropy due to the distribution of ferromagnet...

1] Defect moment of antiferromagnets yields the highest remanent coercivity observed among minerals, and previous studies have been unable to reach saturation of isothermal remanent magnetization (IRM) in some goethite and hematite, even up to 20 Teslas, using resistive Bitter magnets. To go further, acquisition of IRM at room temperature has been...

The ∼32 Ma, NW-SE elongate, 75 km-long granite pluton of Zahedan is one of the most conspicuous geological features of southeast Iran. It is composed of metaluminous to weakly peraluminous rocks, corresponding to magnetite- and ilmenite-bearing I-type granitoids, ranging from diorites to granites. All rocks, including the late andesitic to dacitic...

According to magnetic carriers, granites were classified as belonging to "ilmenite se-ries" or to "magnetite-series" [Ishihara, S., 1977. Mining Geology, 27: 293-305.]. Sus-ceptibility values [Ellwood & Werner, 1981. EPSL, 54: 200-202] allow corresponding this sorting with "non-magnetic" (10 −5 to 10 −4 S.I.) and "magnetic" granites (10 −3 to 10 −2...

The Teofilândia area, south of the Serrinha block (São Francisco Craton, NE Brazil), marks a region where the boundary between the Serrinha block and the Itabuna-Salvador-Curaça belt rotates from NS to EW. The granitoids of Teofilândia are made of granodiorites and trondjhemites dated at 2.13 Ga. To the south and west, they are hosted by biotite-be...

The Variscan Querigut Pluton (eastern Axial Zone, Pyrenees), recently dated at 307 ± 2 Ma, is a classical example for the structural study of granitoids. We present a new structural analysis of this pluton using the powerful technique of magnetic susceptibility anisotropy (AMS). A model of pluton emplacement is proposed on the basis of complementar...

The Tenkodogo–Yamba (TY) elongate pluton is made of apparently isotropic biotite-bearing granites that form a continuous, 125 km long and NE trending, and 15–20 km wide, succession of granite bodies that intruded the so-called batholith of eastern Burkina Faso dominated by foliated granitoids and associated volcano-sedimentary belts. Geochemically,...

The low anisotropies of paramagnetic granites, due to magnetocrystalline anisotropy, require a statistical treatment of the anisotropy of magnetic susceptibility (AMS) data when systematic fabric studies are performed. Absence of statistical information on these data makes evaluation of their quality difficult. The statistical significance of magne...

Structural studies of Variscan plutons of the Pyrenees demonstrate their syn-orogenic character, contrasting with their post-orogenic Permian Rb-Sr datation. The Bassiès and Mont-Louis-Andorra plutons were emplaced before the main Variscan D2 phase and behaved as rigid markers during D2. Emplacement of the Néouvielle pluton was coeval with D2 as at...

The basement of central Madagascar registered a polyphase history during Panafrican times. The latest events (560--530 Ma) are responsible for a major N-S shear zone, the Angavo shear zone, characterized by steep foliation planes and N-S subhorizontal lineations (Nédélec et al., 2000). This shear zone has been active in low-pressure granulitic cond...

A full textural study of the Upper Critical Zone plagioclase-pyroxene cumulates of the Bushveld complex is presented. This zone display a spectacular but irregular cyclic layering, whose complete development show a basal ultramafic layer, associated to chromitite, grading to norite, capped by an anorthosite layer. This cyclic pattern fits with reve...

ABSTRACT The Pan-African orogeny left a strong imprint on the basement rocks of Madagascar, which were metamorphosed up to granulite facies conditions. The supracrustal Itremo Group of central Madagascar, comprising quartzites, schists and carbonates of lower metamorphic grade, has to date been described as a folded sedimentary sequence. Despite th...

The anisotropy of magnetic susceptibility (AMS) of magnetite-free granites having complex paramagnetic mineralogies can be thermally enhanced. In-air heating at 650 degreesC during 2 h helps growing new magnetites that are mimetic with respect to the biotite cleavages. As attested by the similar after-heating AMS and AAR fabrics, the signal of the...

Combining geological mapping and petrological, structural and geophysical (gravity and seismic) data already available for the late Proterozoic Rogaland Igneous Complex of Norway allows the 3D shape of the Bjerkreim–Sokndal layered intrusion to be modelled as a thick cumulate series capped by massive granitic rocks. Using the latter data, along wit...

Fabrics of the Brasiliano-age granitoid plutons of the Seridó belt (northeastern Brazil) were organized following the partitioned regional strain field which shaped larger areas of the basement and its metapelitic cover. Nine plutons located at the central and western portions of the belt have been investigated by means of anisotropy of magnetic su...

In order to extract geological information about the possible emplacement mode of the late-Variscan granite plutons of British Cornwall, detailed petro-structural studies, including magnetic fabric coverages, have been performed in Carnmenellis and Bodmin plutons. The behaviour of these granites is paramagnetic (no magnetite). However, tourmaline i...

Hydrothermalized A-type granites are commonly identified by their pink to red-brick colour attributed to tiny flakes of hematite in the alkali feldspars. These inclusions can be of interest in magnetic studies, but their timing and process of formation are still unclear. Formation of chlorite after biotite is the commonest effect of hydrother- mali...

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 exceedin...

The Papoose Flat pluton of eastern California is commonly cited in the geologic literature as a classic example of a "forcibly" emplaced pluton, although the relative importance attributed to magmatic versus tectonic processes in controlling the structural evolution of the pluton has been controversial. Reexamination of this Late Cretaceous (83 Ma)...

The thermally induced growth of mimetic magnetite after biotite is here demonstrated by the equivalence of anisotropies of magnetic susceptibility (AMS) and anhysteretic remanence (AAR) after heating of biotite single crystals and whole rock specimens from a magnetite-free granite (Elba Island, Italy). It is concluded that between 500° and 725°C ma...

This microstructural and anisotropy of magnetic susceptibility study of the internal structures of the Hercynian Nouvielle granite pluton (100 km2) provides new data indicating that the pluton was emplaced during the main Hercynian tectonic event recognized in the Pyrenees. It also provides new data about the later Alpine deformation localized alon...

The Precambrian basement of Madagascar acquired a polyphase imprint during the Pan-African orogeny. In northern central Madagascar, emplacement of stratoid alkaline granites at midcrustal depth (4-5 kbars) led to formation of a layered crust in a postcollisional extensional regime at 630 Ma (D1). Subsequently, the structures of the stratoid granite...

The principle of anisotropy of magnetic susceptibility measurement, or AMS, and elements of magnetic mineralogy applied to granitic rocks, are presented. AMS measurement allows the study of the magnetic fabric of magnetite-free, paramagnetic granites in which the iron-bearing silicates carry the signal, and ferromagnetic granites dominated by magne...

Abstract — Magnetic susceptibility anisotropy and fabrics in granites. The principle of anisotropy of magnetic susceptibility measurement, or AMS, and elements of magnetic mineralogy applied to granitic rocks, are presented. AMS measurement allows the study of the magnetic fabric of magnetite-free, paramagnetic granites in which the iron-bearing si...

The Vila Pouca de Aguiar granite pluton, emplaced during the latest event of the Variscan orogeny of northern Portugal, is here subjected to a detailed study that combines magnetic fabric measurements and gravity modelling of its shape at depth. This laccolith, less than 1 km in thickness over ≈60% of its outcrop area, appears to be fed from its no...

Although twenty years ago fabric was defined as “the complete spatial and geometrical configuration of all those components that make up a deformed rock”, fabric was mainly synonymous with lattice preferred orientation. Very little attention has been paid to the multi-scale geometrical and spatial relationships of the rock components. Fabric quanti...

The Tioueine pluton intrudes the Neoproterozoic series of the Iskel terrane, located in the Tuareg shield, western Hoggar. The consistency of the internal structures as well as the nature and organization of the associated microstructures demonstrate that the Tioueine pluton was emplaced syn-kinematically while N–S strike–slip shear zones were acti...

The three plutons of the Cauterets–Panticosa granite complex are studied by the anisotropy of magnetic susceptibility (AMS) technique. As expected from the dominantly paramagnetic nature of the rocks, the magnetic susceptibility zonation accurately compares with the lithological zonation. Detailed examination of the linear and planar structural pat...

The Rubim pluton (160 km2), a suite of diorite and porphyritic granodiorite bodies, was subject to magnetic susceptibility and anisotropy studies. The pluton intrudes high-grade to migmatitic gneisses of the Jequitinhonha Complex situated in the Neoproterozoic Araçuaı́fold belt, Southeast Brazil. The magnetic susceptibility is shown to be of parama...

The relationships between Hercynian deformation and contact metamorphism in the aureole of the Aneto unit, a constituent pluton of the Maladeta granite complex (Spanish Pyrenees), provide new data relevant to the controversy between the syn-and post-tectonic models of emplacement for the Pyrenean granites. The deformation in the Aneto aureole is re...

This paper is part of the special publication Continental transpressional and transtensional tectonics (eds. R.E. Holdsworth, R.A. Strachan and J.F. Dewey). Synthesis of several recent structural studies in the Pyrenees points to a syntectonic emplacement of granitic plutons, more or less early during the D2 main phase of the Hercynian orogenesis....

We present a dynamic scenario of granite emplacement in the upper crust for the pluton of Cabeza de Araya (Extramadura, Spain), based on interpretations of gravity data, internal structures and geochemical variations. The three-dimensional shape of the pluton is derived from the inversion of gravity data, and the magma flow structures are obtained...

The two-dimensional Anisotropic Wavelet Transform aims to decipher images in which distributions are combined at different scales. Based on the Optimized Anisotropic Wavelet Coefficient method (OAWC), we present two C++ programs which enable multi-scale analysis and discrimination of objects, or groups of objects, depending on their area, shape rat...

Two granite plutons in the Pan-African belt of Hoggar, Algeria, are studied using the anisotropy of magnetic susceptibility technique (AMS) at low-field, together with a study of microstructures. The Tesnou Complex is made of coalescent plutons at the margins of which dextral N-S-oriented shearing imprints solid-state textures. In the granite, micr...

Anisotropy of magnetic susceptibility (AMS) and microstructures of the Neoproterozoic Triunfo alkaline pluton, situated in northeast Brazil, have been investigated in order to characterize fabrics formed during its emplacement. Bulk magnetic susceptibility in the pluton varies between 0.15 × 10−3 and 25 × 10t-3 SI, and the mean magnetic anisotropy...