Abstract
Lead isotope composition has been determined for a diverse suite of Cenozoic igneous rocks in the central and north Aegean Sea. These include voluminous Miocene shoshonitic and calc-alkali volcanic rocks and correlative plutonic phases; middle Miocene adakitic (high Mg) andesite and associated rhyolite; and middle Miocene to Quaternary ne-normative basalt, trachyte and K-rich andesite. The trace-element contents of most of the studied rocks suggests that Pb-isotopic composition is not a result of upper-crustal contamination, but rather is a feature of the mantle source for K-rich rocks. This mantle source is represented by primitive mafic to intermediate volcanic rocks with 87Sr86Sr ≈ 0.7095, high 207Pb204Pb and 208Pb204Pb, >1000 ppm Sr and Ba, and >35 ppm Pb. The high 207Pb204Pb requires a metasomatic origin that lowered U/Pb and increased Th/Pb, followed by a second-stage residence time of >1 Ga. This K-rich magma was generated as a result of late Tertiary extension of the Aegean. In the South Aegean Arc, there is more evidence for crustal contamination, either from present crust or from subduction of Nile-derived sediment.
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