Geochemistry of mylonitic gneisses from the Cycladic Basement Unit (Paros and Serifos, Aegean Sea): implications for protoliths of the high-grade gneisses

Migration of Arc Magmatism Above Mantle Wedge Diapirs With Variable Sediment Contribution in the Aegean

“…Since the magmas with <58 wt% SiO 2 were derived by partial melting of the mantle wedge with only minor effects of fractionation or assimilation, this approximately represents the isotopic range of the mantle source, which has been enriched by variable components of the subducted slab. Any crustal assimilation would lead to increasing SiO 2 and 87 Sr/ 86 Sr, because the overriding continental crust consists of Mesozoic to Tertiary units,for example, widespread gneisses with 87 Sr/ 86 Sr > 0.710 (Buettner et al., 2005; Frei, 1995; McGrath et al., 2017). The relatively constant 87 Sr/ 86 Sr and 143 Nd/ 144 Nd between mafic and felsic rocks at Maronia, Samothraki, Limnos, and Evia indicates that the evolution of these magmas is dominated by fractional crystallization (Figures 5a and 5c).…”

“…The upper crust of these continental blocks consists mainly of Mesozoic to Tertiary sedimentary sequences ranging from pelitic to volcaniclastic, platform, and flysch sediments. Accreted parts of the lower crust crop out in the metamorphic core complexes of the Cyclades, for example, the gneisses and metasediments at Paros, Serifos, and Ios (Buettner et al., 2005; McGrath et al., 2017). We suggest that the variation in Sr and Nd isotope ratios (Figure 4) reflect the changes of amount and type of subducting sedimentary material with time, similar to observations in calc‐alkaline to shoshonitic lavas of the Sunda‐Banda arc (Elburg et al., 2004).…”

Structural Study and Detrital Zircon Provenance Analysis of the Cycladic Blueschist Unit Rocks from Iraklia Island: From the Paleozoic Basement Unroofing to the Cenozoic Exhumation

“…The structurally underlying CB is mainly exposed on the islands of Paros, Naxos, Ios, Sikinos and comprises Carboniferous (Variscan s.l.) granitoids related to the closure of the Paleotethys and intruded into late Proterozoic-early Paleozoic metasedimentary sequences of Gondwanan affinity [14,19,20,32,35,[70][71][72][73][74][75][76][77]. The contact between CB/CBU has been variably considered as either an extensional detachment fault, ductile shear zone [78][79][80][81], or thrust [58].…”