Formation, deformation and exhumation of a high-pressure/ultra-high-pressure mélange - the Adula Nappe (Central Alps).

我们想研究阿杜拉推覆体中榴辉岩相构造混杂岩的形成和发掘。大多数发现的俯冲到超高压（UHP）变质条件下（深度超过80公里）的岩石位于与阿杜拉推覆体类似的以大陆岩石为主的混杂带，将这些岩石挖掘回表层是讨论最多的构造问题之一。特别是，混杂岩的形成与沿俯冲板块边界的发掘之间的关系仍然存在争议。一些研究认为，在弱俯冲通道的连续回流过程中，在挖掘过程中同时存在强烈的岩石混合，而另一些研究则认为在不同的挖掘事件中挖掘出相干的高压/超高压单元（这意味着混合岩在俯冲过程中形成得更早）。阿杜拉推覆构造是解决这一基本问题的完美范例。我们将(1)通过对石榴石定年确定整个阿杜拉推覆岩中榴辉岩和石榴石-白云母片岩的峰值压力条件的时间，(2)确定相同样品的压力-温度历史，(3)揭示峰值压力条件后最早变形的运动学和变质条件。我们将识别与挖掘相关的推覆体内部应变，并确定在挖掘过程中，阿杜拉推覆体是作为一个连贯的单元被挖掘出来的，还是由不同压力-温度-时间历史的组分混合而成。因此，这项研究将提高对大陆地壳在俯冲通道中的行为的整体认识。

We want to study the formation and exhumation of an eclogite facies, tectonic melange in the Adula Nappe (Central Alps). Most findings of rocks that were subducted to ultra-high-pressure (UHP) metamorphic conditions (depths in excess of 80 kilometres) are located in melange zones of dominantly continental rocks similar to the Adula Nappe and exhumation of such rocks back to the surt ace represents one of the most discussed tectonic problems. In particular, the relation between melange formation and exhumation along the subducting plate boundary remains controversial. Some studies propose Intense mixing of rocks simultaneous with exhumation during continuous return flow in a weak subduction channel, while others argue for exhumation of coherent HP/UHP units in distinct exhumation events (implying that the melanges formed eariier during subduction. The Adula Nappe represents a perfect example to attack this fundamental problem. We will (1) determine the time of peak pressure conditions in eclogites and garnet-whIte-mica schists throughout the entire Adula Nappe by dating garnets, (2) determine pressuretemperature histories of the same samples, and (3) unravel kinematics and metamorphic conditions of the eariiest deformation postdating peak-pressure conditions. We will identify the nappe internal strain associated with exhumation and find out whether the Adula Nappe was exhumed as a coherent unit or was amalgamated from components with different pressure-temperature-time histories during exhumation. Hence, this study will improve the overall knowledge about the behaviour of continental crust in a subduction channel.