Ultramafic (mg# > 88) xenoliths from the Tertiary Veneto Volcanic Province (SE Alps, Italy) are characterized by variable depletion due to removal of a basaltic component and show significant trace element and isotopic heterogeneity (87Sr/86Sr: 0.703031-0.704356; 143Nd/144Nd: 0.512817-0.513085; 206Pb/204Pb: 18.539-19.694; 207Pb/204Pb: 15.608-15.658; 208Pb/204Pb: 38.412-39.660; 18O: 6.6-11.2‰). Variable large-ion lithophile and light rare earth/high field strength element ratios and isotopic compositions are seen in samples showing comparable mineralogy and major element content. Whole rock geochemical characteristics and the presence of spongy clinopyroxene and glass patches may be explained by metasomatism of the local mantle lithosphere induced by both alkaline magmas upwelling to the surface (OIB-like mantle diapirism) and interaction with slab-derived material. In comparison with the geochemistry of xenoliths carried by alkaline magmas in typical within-plate tectonic environments, the Veneto xenoliths record a major heterogeneity of the local lithosphere. This appears to be related to a geodynamic scenario that was previously dominated by active continental collision, in which hot spot magmatism subsequently manifested itself.
Petrological and geochemical evidence for multiple metasomatism of the SE Alps mantle lithosphere
MACERA, PATRIZIA;
2006-01-01
Abstract
Ultramafic (mg# > 88) xenoliths from the Tertiary Veneto Volcanic Province (SE Alps, Italy) are characterized by variable depletion due to removal of a basaltic component and show significant trace element and isotopic heterogeneity (87Sr/86Sr: 0.703031-0.704356; 143Nd/144Nd: 0.512817-0.513085; 206Pb/204Pb: 18.539-19.694; 207Pb/204Pb: 15.608-15.658; 208Pb/204Pb: 38.412-39.660; 18O: 6.6-11.2‰). Variable large-ion lithophile and light rare earth/high field strength element ratios and isotopic compositions are seen in samples showing comparable mineralogy and major element content. Whole rock geochemical characteristics and the presence of spongy clinopyroxene and glass patches may be explained by metasomatism of the local mantle lithosphere induced by both alkaline magmas upwelling to the surface (OIB-like mantle diapirism) and interaction with slab-derived material. In comparison with the geochemistry of xenoliths carried by alkaline magmas in typical within-plate tectonic environments, the Veneto xenoliths record a major heterogeneity of the local lithosphere. This appears to be related to a geodynamic scenario that was previously dominated by active continental collision, in which hot spot magmatism subsequently manifested itself.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
