Sr-rich aragonite veins in Hyblean serpentinized peridotite xenoliths (Sicily, Italy): Evidence for abyssal-type carbonate metasomatism

Most of Hyblean serpentinized peridotite xenoliths (south-eastern Sicily, Italy) are characterized by the abundance of some incompatible trace elements, particularly Sr, whose origin is still debated. A cryptic metasomatic process is traditionally invoked, although there is also mineralogical evidence for ancient hydrothermal alteration. In this work, two selected peridotite xenoliths were investigated by combining scanning electron microscopy (SEM), electron probe microanalyses and vibrational (Infrared and Raman) spectroscopy. The results, based on both new and previously published data, confirm that the Sr contents in Hyblean partially serpentinized peridotite xenoliths correlate linearly with the loss on ignition (LOI, wt%), indicating that alteration strongly influences whole-rock compositions of these rocks. The Sr abundance is related mainly to the presence of aragonite veins (SrO = 0.65–5.10 wt%), substituting serpentine veins. A tentative timing of alteration of Hyblean deep-seated xenoliths, based on published data on hydrothermal zircons and the SmNd isotope compositions of some peridotite xenoliths, suggests a Permo-Triassic time range, in agreement with palaeo-geographical reconstructions suggesting that Sicily and much of the present Mediterranean are presently rooted in a preserved in-situ remnant of the (Early Devonian) Palaeo-Tethys realm.