Géochimie isotopique du lithium dans les basaltes-Géochimie des ...
Géochimie isotopique du lithium dans les basaltes-Géochimie des ...
Géochimie isotopique du lithium dans les basaltes-Géochimie des ...
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tel-00344949, version 1 - 7 Dec 2008<br />
2. Article soumis à EPSL<br />
data, the chemical variations shown in figure 2.10 can be explained by the involvement of<br />
two<br />
distinct reservoirs:<br />
44<br />
�i� The first component is expressed in the least evolved volcanics and is<br />
characterized by an HIMU‐like isotopic signature �Wilson and Downes, 1991,<br />
1992� with high Pb isotopic ratio � 206 Pb/ 204 Pb � 19.6� and low 87 Sr/ 86 Sr ratio ��<br />
0.7037�.<br />
�ii� The second component displays a slightly more radiogenic Sr isotopic<br />
compositions � 87 Sr/ 86 Sr � 0.7043�, lower εNd and lower Pb isotopic ratios<br />
� 206 Pb/ 204 Pb � 19.3�, features that indicate unambiguously a continental crust<br />
component.<br />
Figure 2.8 : Binary plot of 206Pb/ 204Pb versus 87Sr/ 86Sr. Chaîne <strong>des</strong> Puys<br />
samp<strong>les</strong> are shown superimposed on AFC models, which are calculated using<br />
a meta‐sedimentary derived lower crustal contaminant and with 3 different<br />
values of the ratio between the assimilation and the crystallization mass �r�.
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