A low δLi lower crustal component: Evidence from an alkalic intraplate volcanic series (Chaîne des Puys, French Massif Central) |
| |
| Authors: | Cdric Hamelin Hans-Michael Seitz Jean-Alix Barrat Laure Dosso Ren C Maury Marc Chaussidon |
| |
| Institution: | aUEB, Université de Brest, CNRS UMR 6538, I.U.E.M., place N. Copernic, 29280 Plouzané Cedex, France;bInstitut für Geowissenschaften, Universität Frankfurt, 1 Altenhöferallee, 60438 Frankfurt, Germany;cCNRS UMR 6538, IFREMER, BP70, 29280 Plouzané, France;dCRPG-CNRS UPR 2300, 15 rue Notre-Dame des Pauvres, 54501 Vandoeuvre-les-Nancy Cedex, France |
| |
| Abstract: | The intraplate volcanic suite of the Chaîne des Puys (French Massif Central) shows a complete petrologic range, from alkali basalts to trachytes. The significant variations of trace elements and radiogenic isotopes along the series strongly support the occurrence of crustal assimilation associated with fractional crystallization (AFC). The least contaminated basalts are clearly related to a HIMU-type reservoir (206Pb/204Pb > 19.6; 87Sr/86Sr < 0.7037; εNd > + 4). The behavior of radiogenic isotopes suggests that the most likely crustal contaminants are meta-sediments located in the lower crust.The Li isotopic compositions of the lavas range from high δ7Li (> + 7‰) in basalts to lighter values in more evolved lavas (down to δ7Li ≈ 0‰). The mantle component, expressed in the least evolved lavas, has a heavy Li isotopic signature, in good agreement with previous δ7Li measurements of OIB lavas with HIMU affinities. The evolution of Li isotopic compositions throughout the volcanic series is in agreement with the AFC model suggested by the Sr–Nd–Pb isotopic systems. Although the behavior of Li isotopes during assimilation processes is currently poorly constrained, our calculations suggest that at least a portion of the lower crust beneath the Chaîne des Puys is characterized by a light Li isotopic composition (δ7Li < − 5‰). |
| |
| Keywords: | Li Sr Nd and Pb isotopes Lower crust Assimilation and fractional crystallization (AFC) HIMU Basalts Trachytes |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
