Lithium elemental and isotopic variations in rock-melt interaction
| Type | : | ACL |
|---|---|---|
| Nature | : | Production scientifique |
| Au bénéfice du Laboratoire | : | Oui |
| Statut de publication | : | Publié |
| Année de publication | : | 2014 |
| Auteurs (5) | : | SU B-x ZHANG H-f DELOULE E VIGIER Nathalie SAKYI P.a |
| Revue scientifique | : | Chemie der Erde / Geochemistry |
| Volume | : | 74 |
| Fascicule | : | 4 |
| Pages | : | 705-713 |
| DOI | : | 10.1016/j.chemer.2014.04.005 |
| URL | : | <go to isi>://wos:000347502700016 |
| Abstract | : | Despite the occurrence of highly variable lithium (Li) elemental distribution and isotopic fractionation in mantle mineral, the mechanism of Li heterogeneity and fractionation remains a controversial issue. We measured Li contents and isotopic compositions of olivine and clinopyroxene xenocrysts and phenocrysts from kamafugite host lavas, as well as minerals in melt pockets occurring as metasomatic products in peridotite xenoliths from the Western Qinling, central China. The olivine xenocrysts in the kamafugites show compositional zonation. The cores have high Mg# (100 x Mg/(Mg+Fe); 91.0-92.2) and Li abundances (5.63-21.7 ppm), low CaO contents (<= 0.12 wt%) and low delta Li-7 values (-39.6 to -6.76 parts per thousand), which overlap with the compositional ranges of the olivines in the melt pockets as well as those in peridotite xenoliths. The rims of the olivine xenperysts display relatively low Mg# (85.9-88.2), high CaO contents (0.19-0.38 wt%) and high delta Li-7 values (18.3-26.9%0), which are comparable to the olivine phenocrysts (Mg#: 86.4-87.1; CaO: 0.20-0.28 wt%; Li: 12.4-36.8 ppm; delta Li-7: 18.1-26.0 parts per thousand) and the silicate-melt metasomatized olivines. The dinopyroxene phenocrysts and clinopyroxenes in the melt pockets have no distinct characteristics with respect to the Li abundances and delta Li-7 values, but show higher and lower CaO contents, respectively, than the clinopyroxenes from silicate and carbonatite metasomatized samples. These features indicate that Li concentration and isotopic signatures of the cores of the xenocrysts recorded carbonatite melt-peridotite reaction (carbonatite metasomatism) at mantle depth, and the variations in the rims probably resulted from xenocryst-host magma interaction during ascent. Our results reveal that the interaction with carbonatite and silicate melts gave rise to an increase in Li abundance in minerals of peridotite xenoliths at mantle depth or during transportation. In terms of delta Li-7, the carbonatite and silicate melts produced remarkably contrasting delta Li-7 variations in olivine. Based on the systematic variations of Li abundances and Li isotopes in olivines, we suggest that the delta Li-7 value of olivine is a more important indicator than that of clinopyroxene in discriminating carbonatite and silicate melt interaction agents with peridotites. (C) 2014 Elsevier GmbH. All rights reserved. |
| Mots-clés | : | - |
| Commentaire | : | Times Cited: 1 Su, Ben-Xun/H-3296-2011 1 |
| Tags | : | - |
| Fichier attaché | : | - |
| Citation | : |
Su B-X, Zhang H-F, Deloule E, Vigier N, Sakyi P (2014) Lithium elemental and isotopic variations in rock-melt interaction. Chem Erde Geochem 74: 705-713 | doi: 10.1016/j.chemer.2014.04.005
|