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

最上层单位（外希腊群岛，塞特岛）的起源和构造变质演化。

• 批准号: 423521329
• 负责人: Professor Dr. Gernold Zulauf
• 金额: --
• 依托单位: Department of Geology
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/423521329?language=en
• 关键词: Provenance; tectonometamorphic; evolution; Uppermost; Unit

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.

克里特岛位于非洲板块向北俯冲到爱琴海下方的弧前位置。从前寒武纪以来，类似的活动板块边缘环境反复出现，这一点至少可以从南太平洋推覆叠层中的两条缝合线中得到证明。阿尔卑斯山的平多斯缝合线将未变质的平多斯单元与最高单元分开，后者由不同的推覆体（阿尔维、瓦托斯、米亚穆、斯皮利、普雷韦利、阿斯特鲁西亚）组成，这些推覆体在年龄、变质类型和变质程度上有很大差异。虽然最高单元与内希腊系的关系是无可争议的，但大多数工作者认为的Pelagonian物源与（1）Spili推覆体中的中侏罗世蛇绿岩，（2）Preveli推覆体中的上侏罗世蓝片岩，（3）Asteroussia推覆体中的Campanian弧型花岗岩不一致。这类岩石在Pelagonian区缺乏，但在Vardar，Serbomacedonian和Rhodope域很常见。为了验证这样一个出处，并揭示如何最高单位的岩石成功地结束在克里特岛和Gavdos，是目前的建议的主要目标。我们的假设可以通过比较推覆体的最高单元与可能的物源区有关的原岩年龄，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时代和演化仍然缺乏约束。因此，将对克里特岛和加夫多斯岛上出露的最高单元的岩石进行以下研究：（1）对Vatos和Spili群的岩石进行显微镜、EBSD、µCT和微探针分析，重点关注变形微组构、有限应变和增量应变以及结晶-变形关系，以约束推覆体就位期间的构造变质演化和运动学。(2)流体矿物（方解石、葡萄石、绿帘石）的U-Pb定年（小尺度等时线），这些矿物在矿脉、应变条纹和剪切带中同运动地形成，以确定变形年龄。(3)变质文石的U-Pb定年对高压-低温变质作用时代的制约(4)Preveli蓝片岩原岩和变质作用的锆石和钛铁矿U-Pb定年(5)对Asteroussia、Vatos和Preveli推覆体的碎屑锆石进行U-Pb测年，以确定变质沉积物的最大年龄和物源。新的结果将是感兴趣的所有工人处理东地中海的阿尔卑斯山地球动力学演变。它们将有助于揭示最高单元的物源区和构造变质演化，这两者对于东地中海地区后三叠纪的地图视图解释至关重要。