| Автор | OTTONELLO, G. |
| Автор | ERNST, W. G. |
| Автор | JORON, J. L. |
| Дата выпуска | 1984 |
| dc.description | Trace element analyses have been obtained employing RNAA and INAA techniques for 23 bulk-rock specimens and for five pairs of mechanically separated opx and cpx from Western Alpine peridotites. Investigated rocks include 5 garnet lherzolites from Alpe Arami, and spinel (+plagioclase) lherzolites from Finero (2), Balmuccia (7), Baldissero (6) and Lanzo (3). Three pyroxene pairs were analysed from Balmuccia and two from Baldissero.All rocks exhibit marked LREE depletions relative to chondritic abundances except for the two Finero samples which appear to be HREE depleted. Separated minerals also show LREE depletions and HREE enrichments relative to chondrites. However, intermediate rare earths are markedly depleted in opx whereas they are enriched in coexisting cpx. Higher overall concentrations and patterns similar to those of the bulk rocks indicate that REE distributions in lherzolites are dominated by clinopyroxene chemistry. In contrast, both opx and cpx appear to contribute equally to the 3d transition element geochemistry of the investigated peridotites.Most of the investigated rocks show the effects of early partial melting of a pre-existing mantle source material characterized by ‘chondritic’ REE fractionation and by a 3d transition element composition near the estimated values of Jagoutz et al. (1979).The melting process probably developed in a closed system (equilibrium melting) and at temperatures which, for the spinel peridotite protolith, seemingly were compatible with estimates of Presnall el al. (1979) for the ‘melting at the cusp’ process (T = 1200–1250 °C). In some cases the residual rocks underwent a further contamination event. This is particularly evident for the Lanzo peridotites, but possibly also for single Baldissero and Balmuccia specimens.During ascent to the surface, the rocks underwent subsolidus annealing which occurred at temperatures around 900–1000 °C under more or less closed system conditions. |
| Формат | application.pdf |
| Издатель | Oxford University Press |
| Копирайт | © Oxford University Press |
| Тема | Articles |
| Название | Rare Earth and 3d Transition Element Geochemistry of Peridotitic Rocks: I. Peridotites from the Western Alps |
| Тип | research-article |
| Electronic ISSN | 1460-2415 |
| Print ISSN | 0022-3530 |
| Журнал | Journal of Petrology |
| Том | 25 |
| Первая страница | 343 |
| Последняя страница | 372 |
| Аффилиация | OTTONELLO G.; Istituto di Geocronologia e Geochimica Isotopica del C.N.R. Via Cardinale Maffi |
| Аффилиация | ERNST W. G.; Department of Earth and Space Sciences, Institute of Geophysics and Planetary Physics, University of California, Los Angeles |
| Аффилиация | JORON J. L.; Laboratoire par analyse en activation neutronique Pierre Süe, C.E.A., Saclay and Institute de Physique du Globe, Université de Paris VI |
| Выпуск | 2 |
