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Deng, Z, Moynier F, van Zuilen K, Sossi P, Pringle EA, Chaussidon M.  In Press.  Lack of resolvable titanium stable isotopic variations in bulk chondrites. Geochimica et Cosmochimica Acta.   10.1016/j.gca.2018.06.016   Abstract

Titanium and calcium are both refractory lithophile elements. Significant stable isotopic variations on Ti and Ca have been documented within calcium, aluminum-rich inclusions (CAIs) in carbonaceous chondrites. To trace the condensation history of Ti in the solar nebula, we conducted a high-precision double-spike Ti stable isotopic study on a large set of chondrites. The studied chondrites have a homogeneous bulk Ti stable isotopic composition (δ49/47TiIPGP-Ti = −0.069 ± 0.018‰, 2se, n = 22, i.e., the per mil deviation of the 49Ti/47Ti ratios relative to the IPGP-Ti reference material). The homogeneity across eleven chondrite groups implies that chondrites have acquired, through the condensation sequence at equilibrium, the average stable isotopic composition of Ti in the refractory solids that condensed early in the solar nebula. In contrast, the light Ca stable isotopic compositions of bulk chondrites can be attributed to either the presence of CAIs (CV-, CM- and CO-type) or parent-body aqueous alteration (CR- and CI-type).

Ducasse, T, Gourgiotis A, Pringle EA, Moynier F, Frugier P, Jollivet P, Gin S.  2018.  Alteration of synthetic basaltic glass in silica saturated conditions: Analogy with nuclear glass. Applied Geochemistry. 97:19-31.   10.1016/j.apgeochem.2018.08.001   Abstract

This study investigates the analogy between basaltic and borosilicate glasses of nuclear interest, by focusing on mechanisms controlling glass dissolution under silica saturation conditions. These conditions are representative of a non- or slowly renewed contacting solution, favouring the formation of a potentially passivating silica rich gel layer and secondary phases. Laboratory batch experiments were performed with synthetic basaltic glass altered at 90 °C, at pH 7 in a saturated 29Si-doped aqueous solution for more than 600 days. Using elemental and isotopic solution analysis and solid characterizations by SEM, TEM and ToF-SIMS, we show that basaltic glass corrodes at an unexpectedly high and constant dissolution rate of 4 × 10−3 g m−2 d−1 associated with the absence of passivating gel. Our results highlight the fact that the dissolution rate is controlled by the hydrolysis of the glassy network, sustained by the precipitation of clay-type minerals and amorphous silica. When tested in similar conditions, the International Simple Glass (ISG), a six oxide borosilicate glasses of nuclear interest displays a much lower rate limited by water diffusion through a passivating layer. The different behavior of the two glasses is explained by their ability to form secondary crystalline phases at the expense of an amorphous passivating film.