Trace-element abundances of iron-rich eclogites,with implications on the geodynamical evolution of the Voltri Group (Pennidic Belt)

Fe (136,900 ppm)- and Ti (28,540 ppm)-rich eclogites contained in the Voltri serpentinites show contents of metallic trace elements different from those of other eclogites described so far, both those of ophiolitic type and those included in ultramafic rocks. The Voltri eclogites are enriched in Mn (1,894 ppm), V (610 ppm), and Co (75 ppm) and depleted in Cr (110 ppm), Ni (56 ppm), and Zr (46 ppm) in comparison with other occurrences. The analyzed samples are: twelve flaser-eclogites, four fine-grained bimineralic eclogites and three eclogites showing an advanced degree of retrometamorphism toward greenschist facies. The given average values (in ppm) are based on nineteen analyzed samples. This trace-element content is believed to reflect the highly fractionated tholeiitic character of the eclogites and suggests that the Voltri rocks originated from the isochemical metamorphism of ferrogabbros which were probably intruded into the serpentinized lherzolites of a mid-oceanic ridge at the time of the opening of the Pennidic trough.