Jean-Yves Calvez

European Commission | ec · Research and Innovation (RTD)

Galena Pb-isotope ratios of epithermal vein and disseminated sulfide occurrences in the Taconian Orogen and Siluro-Devonian basin cluster around 17.90–18.05 for 206Pb/204Pb and 37.70–38.00 for 208Pb/204Pb. The major source of Pb in most, if not all, occurrences is a fairly common continental crust, a characteristic found in published analyses of Gr...

Three cores from different Red Sea deeps were analysed for Sr-Nd isotopes and REE. Non-metalliferous biodetrital sediment from the Shaban Deep was used as reference. Its REE-pattern characteristics are similar to those of normal detrital sediment, whereas the Sr and Nd isotope ratios (0.7092 and εNd = −4.7) are consistent with deposition from seawa...

The Rei Bouba Group is a sedimentary and volcanic sequence (750–?650 Ma), regarded as a remnant of a Pan-African (back-arc?) orogenic basin that separated a remobilized Paleoproterozoic crust from an accretionary area (Poli Complex: 800-650 Ma). The latter was subjected to early deformation (D1) and intruded by calc-alkalic plutons (670 Ma). Transp...

The Precambrian basement of northern Mozambique is composed mainly of high-grade gneiss, granulite, migmatite and orogenic plutonic rocks emplaced and deformed during the Mozambican orogeny between 1100 and 850 Ma. Granulite nappes (Lurio Supergroup) were thrust over allochthonous supracrustal units (Chiure Supergroup), and both sequences were then...

A Pb isotope study was carried out on three main types of Cu(Au) hydrothermal mineralization in the allochthonous terrains of northern Oman: (1) the Al Ajal sulphide-hematite deposit of Late Permian age; (2) massive sulphide deposits emplaced during a major break in the Late Albian-Early Cenomanian volcanic activity; and (3) minor massive sulphides...

Strontium isotope studies (120 analyses) were carried out on ore and gangue minerals from five ore districts in different carbonate basins. Most of the samples were separated from consecutive diagenetic generations. Even for diverse stratigraphic positions and mineralogies, very consistent trends are recognized. In all cases87Sr/86Sr ratios increas...

The St.-Fabien deposit occurs in the Taconic thrust belt of the Quebec Appalachians. It consists of intimately associated veins and disseminations of barite, galena, and sphalerite hosted in interdigitated sandstones and limeston conglomerates comprising a proximal, deep submarine facies of the Upper Cambrian St.-Damase Formation. At a late stage i...

The Ariab district is part of a vast Late Proterozoic volcanosedimentary complex that extends for 250 km in the Red Sea Hills Province of norhteastern Sudan. It includes numerous polymetallic sulphide bodies of exhalative origin and associated economically important auriferous mineralization with quartz-barite breccias. One hundred Pb-isotope analy...

Chemical and strontium isotopic analyses have been performed on 10 geothermal waters from the Valles caldera/Jemez Mountain region, as well as 10 rock samples collected in the VC-1 scientific core hole. The 87Sr/86Sr values of other rocks sampled in the Jemez Mountains have also been used in this study to understand relations between the fluids and...

Isotopic (Sr, Nd, Pb) and trace element data are reported for samples dredged along the South-East Indian Ridge (SEIR). They confirm the existence of a geochemical province under the Indian Ocean which is distinct from the provinces observed under the North Atlantic and Pacific Oceans. This province is characterized by the association of Sr and Nd...

U-Pb dating from zircons from high magnesio-potassic (Mg-K) calc-alkalic monzogranite of Calvi (Western Corsica, France) provide an age of 350(+36, -18) Ma interpreted as the time of emplacement of the Mg-K rocks, early in the genesis of the Corsica-Sardinia batholith during the anatexis of an amphibolite facies metamorphic basement. There is an ab...

Icart orthogneisses (Guernsey, Channel Islands) present, in spite of their petrographic homogeneity, Rb-Sr whole rock data strongly scattered between two reference isochrons at 2.55 and 1.91 b.y. We present a U-Pb zircon age of 201815m.y. (upper intersection on Concordia) which is probably close to the emplacement age of the whole massif. This age...

Les méthodes classiques de la géologie structurale ont pour but de reconstituerl'histoire de la croûte continentale, et pour un domainedonné; d'établir d'une part, une chronologie des différents orogènes quel'on y observe et d'autre part, de caractériser les évènements magmatiques,métamorphiques et structuraux, liés au développement de chaqueorogèn...

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