Rare earth element and other trace element distribution,and the origin of the iblean magmas

In the Iblean region, southeast Sicily, a sequence of subaqueous and subaerial volcanics is interlayered in sedimentary levels, Upper Miocene to Lower Pleistocene in age. These rocks range from low-K tholeiites to basanites.Rare earth elements (REE) have been determined by instrumental neutron activation analysis in five samples, and other trace elements (Li, Rb, Sr, Co, Cr, Cu, Ni) by atomic absorption spectrophotometry in thirteen samples, already analyzed also for major elements.The tholeiites differ systematically from rocks of the alkalic suite for elements like Li, Sr and light REE (Sr < 200 ppm, Ce ? 15 ppm in the former; Sr > 500 up to 2000 ppm, Ce > 150 ppm in the latter), while Ni, Co, Cr and heavy REE ranges overlap in the two rock suites.The results agree in indicating different degrees of partial melting, probably at different levels in a heterogeneous mantle, as responsible for the origin of most of the rocks found in the Iblean region: the tholeiites should have been formed at relatively shallow depth by fusion of large proportions of a depleted mantle, while increasingly undersaturated volcanics of the alkalic suite have been probably generated at greater depth by partial melting of decreasing amounts of mantle material.