Computer Science
Scientific paper
Aug 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000e%26psl.180..259l&link_type=abstract
Earth and Planetary Science Letters, Volume 180, Issue 3-4, p. 259-270.
Computer Science
9
Scientific paper
The first comprehensive chemical and Sr-Nd-Pb isotopic data set of Plio-Pleistocene tholeiitic and alkaline volcanic rocks cropping out in Sardinia (Italy) is presented here. These rocks are alkali basalts, hawaiites, basanites, tholeiitic basalts and basaltic andesites, and were divided into two groups with distinct isotopic compositions. The vast majority of lavas have relatively high 87Sr/86Sr (0.7043-0.7051), low 143Nd/144Nd (0.5124-0.5126), and are characterised by the least radiogenic Pb isotopic composition so far recorded in Italian (and European) Neogene-to-Recent mafic volcanic rocks (206Pb/204Pb=17.55-18.01) (unradiogenic Pb volcanic rocks, UPV); these rocks crop out in central and northern Sardinia. Lavas of more limited areal extent have chemical and Sr-Nd-Pb isotopic ratios indicative of a markedly different source (87Sr/86Sr=0.7031-0.7040 143Nd/144Nd=0.5127-0.5129 206Pb/204Pb=18.8-19.4) (radiogenic Pb volcanic rocks, RPV), and crop out only in the southern part of the island. The isotopic ratios of these latter rocks match the values found in the roughly coeval anorogenic (i.e. not related to recent subduction events in space and time) mafic volcanic rocks of Italy (i.e. Mt. Etna, Hyblean Mts., Pantelleria, Linosa), and Cenozoic European volcanic rocks. The mafic rocks of the two Sardinian rock groups also show distinct trace element contents and ratios (e.g. Ba/Nb>14, Ce/Pb=8-25 and Nb/U=29-38 for the UPV; Ba/Nb<9, Ce/Pb=24-28 and Nb/U=46-54 for the RPV). The sources of the UPV could have been stabilised in the Precambrian after low amounts of lower crustal input (about 3%), or later, during the Hercynian Orogeny, after input of Precambrian lower crust in the source region, whereas the sources of the RPV could be related to processes that occurred in the late Palaeozoic-early Mesozoic, possibly via recycling of proto-Tethys oceanic lithosphere by subduction.
Lustrino Michele
Melluso L.
Morra V.
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