Slab tearing or slab retreat as triggers of extension at the Dinaric-Hellenic transition?

这个项目将展示地壳如何对大陆岩石圈从回滚俯冲到大陆-大陆斜碰撞的沿走向转换做出反应。俯冲模式中的横向转换是相关的，因为它们与地震活动的显著差异相吻合，并伴随着沿海和山区的社会危害。具体地说，我们将检验这样的假设，即沿着欧洲东南部的迪纳里亚-希腊链俯冲模式的变化涉及晚期造山伸展，这些伸展向板片撕裂或板片回滚和弧形方向迁移。调查最初将集中在迪纳里德和希伦尼德的交界处，在那里，我们的初步工作揭示了造山带平行和正向伸展断裂，它们叠加并重新激活了较老的冲断。这是一个开始的好地方，因为它与地球物理成像的地幔结构的一级差异相吻合，从目前向西南撤退的希腊西北部下方的SSE倾斜的大陆板块，到迪纳里德山脉下的较短的板块，几乎没有或没有后退。到目前为止，我们的工作表明，这一过渡期的地壳结构以一条横向正断层(Shkoder-Peja Normal断层或SpnF)为标志，该断层沿着其走向从西南到东北方向容纳了越来越多的造山带平行伸展，在那里它与中上新世科索沃(梅托亚)盆地接壤。然而，SpnF只是该地区几条断层中的一条，这些断层的年龄和运动学是理解地壳伸展是与希腊回滚俯冲、迪纳里德之下的板片剥离或断裂有关，还是与这些机制的某种组合有关的关键。调查还将涉及迪纳里德斯-希伦尼德山脉的另外三个地点，在这些地点，地层和推覆结构的沿线走向变化与造山带垂直断层重合。为了实现这些目标，我们将结合最先进的测年方法(断块的磷灰石裂变径迹和氦分析、断裂带沉积盆地的碎屑热年代学)和成熟的构造技术(断层滑动分析、组构作图)。

This project will show how Earths crust responds to an along-strike transition from roll-back subduction of continental lithosphere to oblique continent-continent collision. Lateral transitions in subduction mode are relevant because they coincide with marked differences in earthquake activity, with attendant hazards for society in coastal and mountainous areas. Specifically, we will test the hypothesis that a change in subduction mode along the Dinaric-Hellenic chain of SE Europe involved late orogenic extension which migrated in the direction either of slab tearing or of slab roll-back and arcuation.Investigation will initially focus on the junction of the Dinarides and Hellenides, where our preliminary work has revealed both orogen-parallel and -normal extensional faults that overprint and reactivate older thrusts. This is an auspicious place to start because it coincides with a first-order difference in geophysically imaged mantle structure, from a SSE-dipping continental slab beneath the northwestern Hellenides currently retreating to the SW, to a shorter slab beneath the Dinarides with little or no retreat. Our work so far suggests that the crustal structure at this transition is marked by a transverse normal fault (the Shkoder-Peja Normal Fault or SPNF) that accommodates increasing amounts of orogen-parallel extension along its strike from SW to NE, where it bounds the Mio-Pliocene Kosovo (Metohia) Basin. However, the SPNF is only one of several faults in this area whose age and kinematics are key to understanding whether crustal extension is related to the Hellenic roll-back subductions, to slab delamination or break-off beneath the Dinarides, or to some combination of these mechanisms. Investigation will also cover three other locations in the Dinarides-Hellenides where along-strike changes in stratigraphy and nappe structure coincide with orogen-perpendicular faults. If so, the Dinaric-Hellenic transition is possibly unique in recording the along-strike response of the lithosphere to changing modes of plate convergence.To realize these goals, we will combine state-of-the-art dating methods (apatite-fission track- and -helium analyses of faulted blocks, detrital thermochronology in fault-bounded sedimentary basins) and well-established structural techniques (fault-slip analysis, fabric mapping).