期刊名称：IOP Conference Series: Earth and Environmental Science
印刷版ISSN：1755-1307
电子版ISSN：1755-1315
出版年度：2008
卷号：2
出版社：IOP Publishing
摘要：The widespread Western Anatolian-Aegean Neogene volcanism presents a complex
geochemical evolution reflecting the uncommon space-time variability of the
geodynamic setting of the region. In the Western Anatolian and Central Aegean, a
widespread supra-subduction magmatism, with calc-alkaline to shoshonitic
affinity, took place from Early to Middle Miocene; this phase of activity ends
with spots of ultra-K lavas and dykes. From Late Miocene onwards scattered
alkali basaltic lavas with intraplate affinity were emitted, while calc-alkaline
activity occurred in the South Aegean arc. Since Late Oligocene-Early Miocene,
the region was, and still is, affected by extensional tectonics generally
ascribed to a backarc rift. However the Aegean region should rather be
considered as an unconventional backarc since its characteristics rather differ
from 'typical' backarcs. In fact, in spite of a long lasting(>40Ma) active
NE-directed subduction of Africa, the backarc area still maintains a relatively
thick continental crust (>20–25 km). Moreover, the upper Eurasian plate is
overriding the lower Africa plate with separate segments, with Greece moving
faster, and Turkey moving slower. The differential velocity between Greece and
Turkey determines extension in the upper plate, unrelated to the loss of
subducted retreating lithosphere, which is the usual setting for the origin of
'classic' backarc settings. The geodynamic framework is supported by the
geochemical and isotopic features of the supra-subduction magmas revealing the
occurrence of a trapped, drying slab, with progressive decreasing of Fluid
Mobile Elements/Fluid Immobile Elements ratios, δ11B and
δ7Li, coupled with scarce variations of Sr and Nd isotopes. Moreover,
the differential motion between the Greek and Anatolian micro-plates creates
tear zones with the formation of slab ruptures or vertical slab windows. The
occurrence of such windows is, in fact, outlined by the presence of alkali
basalts with intraplate affinity sourced in the sub-slab mantle.
