Magma formation and evolution in the western South Aegean Volcanic Arc: Implications for crustal growth and arc migration

像爱琴海弧这样的俯冲带通常表现出广泛的岩浆活动，包括爆炸性火山爆发和大型岩体的侵入，有助于大陆地壳的生长。岩浆成分变化很大，从镁铁质到长英质，从低钾钙碱性到钾玄质系列。这些岩浆的形成在空间和时间，镁铁质和长英质熔体之间的关系，以及构造和岩浆过程的关系知之甚少。 在此，我们建议检验几种关于爱琴海弧岩浆形成的假说：（1）爱琴海弧不同时期的不同母岩浆反映了不同的沉积俯冲作用;（2）底辟构造中的岩浆可能是通过减压熔融形成的;（3）包括同化作用在内的分离结晶作用发生在不同的地壳层次;（4）长英质岩石与来自地幔的伴生基性岩密切相关。将对来自希腊东北部、萨莫斯拉克、利姆诺斯、萨摩斯、保萨尼亚斯和米洛斯的爱琴海弧中选定的岩浆中心的熔岩样品进行研究。通过确定原始低钾钙碱性钾玄质岩浆的组成，我们将能够模拟地幔中导致其形成的混合和熔融过程的连续性，并将组成与实验工作的组成进行比较，以确定温度和压力。对熔岩中的橄榄石、单斜辉石和角闪石的研究将有助于了解原始岩浆的成分、停滞的深度以及上升过程中的连续同化过程。对希腊东北部和较年轻的爱琴海弧火山岩的年代学研究将有助于确定岩浆活动的迁移和不同岩浆系列之间的演化。

Subduction zones like the Aegean arc typically show extensive magmatic activity including explosive volcanic eruptions and intrusion of large plutons contributing to the growth of the continental crust. The magmas a highly variable in composition ranging from mafic to felsic and from low-K calc-alkaline to shoshonitic series. The formation of these magmas in space and time, the relationship between mafic and felsic melts, and the relation of tectonic and magmatic processes are poorly understood. Here we suggest to test several hypotheses of magma formation in the Aegean arc: (1) different parental magmas in the Aegean form at different times reflecting variable sediment subduction, (2) magmas form in diapiric structures possibly by decompression melting, (3) fractional crystallization including assimilation occurs at different crustal levels, and (4) felsic rocks are closely related to associated mafic rocks from the mantle. Lava samples from selected magmatic centres in the Aegean arc from NE Greece, Samothraki, Limnos, Samos, Pausanias and Milos will be stueied. By defining the composition of primitive low-K calc-alkaline to shoshonitic magmas we will be able to model the succession of mixing and melting processes in the mantle causing their formation and to compare the compositions to those of experimental work in order to define temperature and pressure. Studies of olivine, clinopyroxene and amphibole in the lavas will provide insight into the composition of primitive magmas, the depths of stagnation, and the successive assimilation processes during ascent. Geochronological studies of volcanic rocks in NE Greece and in the younger Aegean arc will help to define the migration of magmatic activity and the evolution between different magma series.