Provenance and tectonometamorphic evolution of the Uppermost Unit (External Hellenides, Cete).

克里特岛位于爱琴海下方非洲板块向北活动俯冲的弧前位置。自前寒武纪以来，类似的活动板块边缘设置被反复给出，克里特推覆体堆叠中至少有两条缝合线记录了这一点。阿尔卑斯平多斯缝合带将未变质的平多斯单元与最上面的单元分开，后者由不同的推覆体(Arvi、Vatos、Miamou、Spili、Preveli、Asteroussia)组成，它们在变质作用的年龄、类型和级别上有很大的不同。尽管最高单元归属于内部希勒尼德是毋庸置疑的，但大多数工作人员认为贝拉贡期的物源与(1)斯皮利推覆体内的中侏罗世蛇绿岩，(2)普雷维利推覆体内的上侏罗统蓝片岩，以及(3)阿斯特鲁西亚推覆体内的坎帕尼亚弧型花岗岩并不一致。这种岩石在伯拉哥尼亚带中很少见，但在瓦尔达尔、塞波马梅多尼亚和罗多普区很常见。核实这一出处并揭示最高单元的岩石是如何成功地在克里特岛和加夫多斯结束的，是本提案的主要目标。我们的假设可以通过比较最高单元的推覆体和可能的源区来检验，其中包括原岩年龄、变质年龄、冷却历史和构造变质演化。然而，目前，最高单元的大多数推覆体的年龄和演化仍然受到很差的限制。为此，将对出露在克里特岛和加夫多斯岛上的最上层单元的岩石进行以下研究：(1)对瓦托斯群和斯皮利群的岩石进行显微、EBSD、µCT和显微分析，重点研究变形显微组构、有限应变和增量应变以及结晶-变形关系，以约束推覆侵位过程中的构造变质演化和运动学。(2)流体来源矿物(方解石、方解石、绿帘石)的U-Pb定年(小尺度等时线)，这些矿物是在矿脉、应变条纹和剪切带中同步运动形成的，以确定变形的年龄。(3)对变质文石进行U-Pb定年，以确定HP-LT变质作用的年龄。(4)锆石和钛铁矿的U-Pb定年，以确定普雷维利蓝片岩的原岩年龄和变质作用。(5)碎屑锆石U-Pb定年，以确定Asteroussia、Vatos和Preveli推覆体的变质岩最大年龄和物源。所有研究地中海东部阿尔卑斯山地球动力学演化的工作人员都会对新的研究结果感兴趣。它们将有助于揭示物源区和最高单元的构造变质演化，这两个方面对于地中海东部地区后三叠世地图图的恢复至关重要。

The Island of Crete is situated in a fore-arc position above northward-directed active subduction of the African plate underneath the Aegean. A similar active plate-margin setting was repeatedly given since Precambrian times, as is documented by at least two sutures in the Cretan nappe stack. The Alpine Pindos suture separates the unmetamorphic Pindos Unit from the Uppermost Unit, the latter consisting of different nappes (Arvi, Vatos, Miamou, Spili, Preveli, Asteroussia), which differ considerably in age, type and grade of metamorphism. While an affiliation of the Uppermost Unit to the Internal Hellenides is beyond dispute, a Pelagonian provenance, as assumed by most workers, is not in line with (1) Middle Jurassic ophiolites in the Spili nappe, (2) Upper Jurassic blueschists in the Preveli nappe, and (3) Campanian arc-type granitoids in the Asteroussia nappe. Such rocks are lacking in the Pelagonian Zone, but are common in the Vardar, Serbomacedonian and Rhodope domains. To verify such a provenance and to reveal how the rocks of the Uppermost Unit succeeded to end up in Crete and Gavdos, are the main goals of present proposal. Our hypothesis can be tested by comparing the nappes of the Uppermost Unit with possible provenance domains concerning protolith age, age of metamorphism, cooling history and tectonometamorphic evolution. At present, however, the age and evolution of most nappes of the Uppermost Unit are still poorly constrained. For this reason the following investigations will be carried out on rocks of the Uppermost Unit exposed on Crete and Gavdos: (1) Microscopic, EBSD, µCT and microprope analyses of rocks of the Vatos and Spili groups focusing on the deformation microfabrics, finite and incremental strain, and crystallization-deformation relation to constrain the tectonometamorphic evolution and kinematics during nappe emplacement. (2) U-Pb dating (small-scale isochrones) of fluid-derived minerals (calcite, prehnite, epidote), which formed synkinematically in veins, strain fringes and shear zones to date the age of deformation. (3) U-Pb dating of metamorphic aragonite to constrain the age of HP-LT metamorphism. (4) U-Pb dating of zircons and titanite to constrain the age of protolith and metamorphism of the Preveli blueschists. (5) U-Pb dating of detrital zircons to determine the maximum age and provenance of metasediments of the Asteroussia, Vatos and Preveli nappes. The new results will be of interest for all workers dealing with the Alpine geodynamic evolution of the eastern Mediterranean. They will help to reveal the provenance area and the tectonometamorphic evolution of the Uppermost Unit, both of which are essential for post-Triassic map-view restorations of the eastern Mediterranean region.