Περίληψη:
Compiled data show the age progression of magmatic centers along the two
approximately linear profiles from NE Greece and NW Turkey to the South
Aegean Volcanic Arc. The age progression reveals the southwestward
migration of arc magmatic activity from Oligocene to present,
perpendicular to the Hellenic Trench. This is in accordance with the
migration of the Aegean subduction zone due to the collision of oceanic
and continental blocks, trench retreat, mantle flow, and coeval
extension. We suggest that the subduction of large volumes of sediments
and their contribution to the sub-arc magma source controlled the
composition of calc-alkaline to high-K calc-alkaline and shoshonitic arc
magmas during the past 30 Ma. The magma geochemistry and the
approximately linear age-progressive migration of magmatic activity
suggest focused ascent of mixed material from the subducted slab into
the mantle wedge, most likely in the form of melange diapirs.
Geochemical data along the profile reveals increasing Sr and decreasing
Nd isotopes during Upper Miocene in agreement with the ongoing
subduction of continental blocks, low subduction rates, and development
of an accretionary wedge. The different K-rich arc magmas reflect the
variable subduction of sediments, whereas crustal assimilation often
plays a minor role. Magmas with variable Sr-87/Sr-86, P/Nd, and Ba/La
indicate a variable contribution of clastic, phosphate-bearing, and
barite-bearing sediments. Low-degree partial melting in
sediment-dominated melange diapirs causes the formation of shoshonitic
magmas with high Sr and P2O5 contents and high La/Yb in the northern
Aegean.
Συγγραφείς:
Schaarschmidt, A.
Haase, K. M.
Voudouris, P. C.
Melfos, V
and Klemd, R.
