Détermination expérimentale du fractionnement isotopique D/H entre tourmaline et eau à 600, 500°C et 3 kbar

International audienceThe experimental calibration ofthe D/H isotopic fractionation between natural tourmaline (schorl-dravite with X$_{Fe}$ ~0.5) and water at 600, 500DC and 3 kbar gives an equilibrium fractionation factor of 1.002 and 0.980 respectively. In this temperature range, the fractionation factor (oc) between tourmaline and muscovite can be expressed as:1,000 ln $\alpha_{tour.-musc.}$ = $-$ 39,3 (10$^6$ T$^{-2}$) +63,4The couple tourmaline-muscovite is the first hydrogen isotope mineral geothermometer which can be applied to high température Systems.La calibration expérimentale du fractionnement isotopique de l'hydrogène entre tourmaline naturelle (schorl-dravite, X$_{Fe}$~0.5) et eau à 600, 500°C et 3 kbar donne un coefficient de fractionnement à l'équilibre de 1,002 et de 0,980 respectivement. Dans cette gamme de température, le facteur de fractionnement ($\alpha$) entre tourmaline et muscovite peut s'exprimer sous la forme :1,000 ln $\alpha_{tour.-musc.}$ = $-$ 39,3 (10$^6$ T$^{-2}$) +63,4Le couple tourmaline-muscovite est le premier géothermomètre minéral, pour les isotopes de l'hydrogène, qui soit applicable aux systèmes de haute température.Expérimental détermination of the D/H isotopic fractionation between tourmaline and water at 600, 500°C and 3 kba

Lithospheric shear zones and mantle-crust connections

cited By 88A crustal-scale ductile shear zone network in the Precambrian granulite-facies crust of Madagascar is examined to determine the nature of the connections between the mantle and lower crust. Based on three independent data sets - field and satellite mapping, C- and O-isotope geochemistry and gravimetry - this crust is divided into three zones: (1) outside of shear zones; (2) minor shear zones that are <140 km long and 7 km wide; and (3) major shear zones that are >350 km long (up to 1000 km) and 20-35 km wide. The mantle is uplifted by about 10 km beneath the major shear zones. The major shear zones are rooted in and are inferred to be controlled by the mantle; they directly tapped mantle-derived CO2. The small-scale minor shear zones were controlled by crustal processes and focused crustally derived H2O-rich±CO2 fluids. The regular distribution of the shear zones on a crustal scale is in agreement with models of buckling of the continental lithosphere in a compressional context. The propagation of these mechanical instabilities promoted and channelled fluid flow. These major Pan-African shear zones thinned the crust and were reactivated during the subsequent drifting of Madagascar and opening of the Indian Ocean during Jurassic to Cretaceous times. They also controlled many of the brittle fault zones in the overlying sedimentary basins. Mantle-rooted large-scale shear zones are inferred to be a general feature of cratonic areas reactivated by shear zone systems

d13C and stomatal number variability in the Cretaceous conifer Frenelopsis. Palaeogeography, Palaeoclimatology, Palaeoecology, 257, 462-473.

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Formation of carbonates in the Tatahouine meteorite

The Tatahouine meteorite, in southern Tunisia, shows terrestrial contamination that developed during 63 years of exposure on Earth's surface. Samples collected on the day of the fall in 1931 contained fractures, with no secondary minerals, whereas samples collected in 1994 contain calcite aggregates (70 to 150 micrometers) and rod-shaped forms (100 to 600 nanometers in length and 70 to 80 nanometers in diameter) on the fractures. Carbon isotope analysis of the carbonates within the Tatahouine meteorite [delta(13)C = -2.0 per mil Pee Dee belemnite standard (PDB)] and the underlying ground (delta(13)C = -3.2 per mil PDB) confirm their terrestrial origin

Incompatible trace element and isotopic (D/H) characteristics of amphibole- and phlogopite-bearing ultramafic to mafic xenoliths from Kerguelen Islands (TAAF, South Indian Ocean)

17 page(s

Carbonatite melt in the oceanic upper mantle beneath the Kerguelen Archipelago

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Carbonatite melt in the oceanic upper mantle beneath the Kerguelen Archipelago

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Carbonatite melt in the Indian oceanic upper mantle (Kerguelen Archipelago, TAAF)

1 page(s