Identifying eroded Messinian deposits on the Maltese Islands by gypsum Sr isotopes

I. Techer (1) , L. Casteleyn (2) , M. Rocher (3) , Y. Missenard (4) , P. Robion (2) , J. Reynes (1)

1 GIS - Laboratoire de Géochimie Isotopique Environnementale (GIS) / Université de Nîmes
2 GEC - Laboratoire Géosciences et Environnement Cergy
3 IRSN/PRP-DGE/SRTG/LETIS - Laboratoire d'Etude et de recherche sur les Transferts et les Installations dans les Sols
4 GEOPS - Géosciences Paris Sud

Evaporite sediments are known to have formed during the Messinian high salinity crisis that has been recognized in many Mediterranean areas. This event was however never identified on the Maltese Islands. In this study, a Sr isotopic characterization of gypsum, found as secondary minerals in the Oligocene-Miocene formations of Malta and Gozo is performed. The 87Sr/86Sr values are discussed on the basis of comparison with the surrounding rock Sr isotopic signature. The data outline two distinguishable 87Sr/86Sr ratios for gypsum according to their facies. Most of crack-infilling mineral data suggest a downward fluid circulation in the Miocene sediment associated with interaction in the currently outcropping limestones. Some gypsum crystals found as crystallized spherules show significantly lower 87Sr/86Sr ratios, close to those defined in the literature for Messinian evaporate sediments. Taken together, this may suggest that an evaporate formation of Messinian age had in the past covered the present-day sedimentary sequence in Malta and Gozo.

Mots clés: Malta; Messinian; Gypsum; Sr isotopes

Mots clés: dépôt Messinien; Malte; Strontium (Isotopes); Gypse

Domaines: Minéralogie; Sciences de la Terre

I. Techer, L. Casteleyn, M. Rocher, Y. Missenard, P. Robion, et al.. Identifying eroded Messinian deposits on the Maltese Islands by gypsum Sr isotopes. 14th International Symposium on Water-Rock Interaction, WRI 14, Jun 2013, Avignon, France. pp.830-833, ⟨10.1016/j.proeps.2013.03.101⟩. ⟨hal-00817848⟩