J.A. Barrat^a, B. Zanda^b, A. Jambon^c, C. Bollinger^d

^aU.B.O.-I.U.E.M., CNRS UMR 66538 (Domaines Océaniques), Place Nicolas Copernic, 29280 Plouzané Cedex, France
^bMuséum National d’Histoire Naturelle, Laboratoire de Minéralogie et de Cosmochimie du Muséum, CNRS UMR7202, 61 rue Buffon, 75005 Paris, France
^cUniversité Pierre et Marie Curie-Paris 6 ISTeP, CNRS UMR 7193, case 110, 4 place Jussieu, 75252 Paris cedex 05, France
^dCNRS UMS 3113, I.U.E.M., Place Nicolas Copernic, 29280 Plouzané Cedex, France

We report on the abundances of a selected set of lithophile trace elements (namely REEs, Y, Rb, Ba, Sr, Zr, Hf, Nb, Th, U) in a comprehensive suite of enstatite chondrites (EC – 13 EH and 11 EL). EH3 and EL3 display only minor deviations from chondritic distributions for these elements. In most metamorphosed EC, a wide range of compositions is observed and suggests a mobility of many of the elements studied during the history of these rocks. For example, EL6 chondrites exhibit light-REE and Nb depletions, negative Eu anomalies, and positive Y anomalies. More important trace element fractionations are observed in metamorphosed EH like St Marks (Rb depletion), LAP 02225 (Rb, Nb, Zr, Eu, light REE depletions) and Galim (b), which displays large Ba, Sr, Eu, Nb and light REE depletions.
Leaching experiments were undertaken to investigate the contributions of sulfides in the whole rock budgets. These phases control not only the REE budget, but also important fractions of the other elements we studied. These fractions strongly depend on the type of the rock (EH or EL, and metamorphic grade). For many elements, the sulfide contributions increase with the metamorphic grades. The trace element abundances of silicate residues are extremely variable. Negative Sm and Yb anomalies are observed in EL3 and EH3 residues, and are certainly the results of early nebular processes. Such anomalies are lacking in residues obtained with most metamorphosed EC, underlining the importance of trace element redistributions during metamorphism. In addition, EL6 residues display distinctive positive Y anomalies that could be potentially ascribed to a less chalcophile behavior than Ho in the conditions that prevailed during EL metamorphism.

Reference
Barrat JA, Zanda B, Jambon A and Bollinger C (in press) The lithophile trace elements in enstatite chondrites. Geochimica et Cosmochimica Acta 98:1966-1971.
[doi:10.1016/j.gca.2013.11.042]
Copyright Elsevier

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