Formation of heterogeneous magmatic series beneath North Santorini, South Aegean island arc

The geochemistry of basaltic to dacitic lavas and dykes in the volcanic centres of North Santorini (Greece) has been investigated using elemental and Sr-Nd-Pb isotopic data and three main magmatic series with sub-parallel trace element patterns for basalts can be distinguished. The basalts have Sr and Nd isotopic values consistent with varying levels of incompatible-element mantle depletion. A fourth magma group with only two basalt samples has a trace element pattern with even lower contents of incompatible elements, especially Th. and with lower Sr-87/Sr-86 but higher Pb-206/Pb-204. Heterogeneous magma formation beneath North Santorini throughout its 500 ka history is attributed to variable transfer of sedimentary components - either terrigenous or pelagic as bulk sediments or high-temperature partial melts rather than fluids or low-temperature partial melts - from a rupture zone in the subducted slab to the overlying mantle. The three main magmatic series followed independent paths of assimilation of upper crustal materials during fractional crystallization. Assimilation was more pronounced at the basaltic stage. The long-lived histories of the three main magmatic series imply repetitive melting of isolated mantle regions, ascent of magmas through independent feeder systems, and their residence in separate crustal magma chambers. (C) 2008 Elsevier B.V. All rights reserved.