Thermal and Structural History of the Pennine-Austroalpine Transition Zone, Alps (Eastern Switzerland)

碰撞山带的大型构造，如阿尔卑斯山或喜马拉雅山，通常记录了反映两个大陆碰撞的缩短应变。然而，越来越多的证据表明，这些带中的一些结构由于伸展而变形，这与预期的模式相反。在某些情况下，伸展可能是由碰撞造成的高地形塌陷的结果。在这个项目中，来自加州理工学院和澳大利亚国立大学的一个研究小组将测试阿尔卑斯山的一个主要结构是否因延伸而变形。如果是这样，这一发现将为主要碰撞山带的复杂过程提供新的线索。该项目将通过以下方式促进预期的社会成果：(1)通过高中辅导计划，让未被充分代表的少数民族充分参与STEM；(2)通过外联活动提高公众科学素养和公众对科学技术的参与；(3)通过培养一名研究生和一名本科生，培养具有竞争力的STEM人才队伍；(4)通过国际合作加强伙伴关系。该项目研究了瑞士东部奥斯特阿尔卑斯异生体基地的结构和低温热史，代表了亚得里亚海微板块与位于欧洲南缘的各种构造地层单元之间的接触。该地区已发表的热年代学和构造资料表明，该断层可能主要是一条正断层，在早第三纪至中第三纪的某个时间点，将异体与其构造复杂的基底——奔宁带并置。在与澳大利亚国立大学的合作下，研究小组将分析异种生物基地南部的8个样带，以限制澳大利亚阿尔卑斯山脉和Penninic区域的热历史，以及基地沿线和附近的结构运输方向。该项目将使用(U-Th)/He和裂变径迹法对磷灰石、锆石和钛矿的样品样带进行冷却路径约束。澳大利亚国立大学的研究小组将使用白色云母和钾长石来限制相同样品的冷却历史。这种跨关键接触带的多方法方法将对异源生物的起源和就位提供强有力的新约束。同种异体底部的正断层起源（冷岩置于热岩之上），如果正确的话，将不仅对这个标志性造山带的组合，而且对一般的会聚造山带具有一级意义。

Large-scale structures in collisional mountain belts such as the Alps or Himalayas typically record shortening strains reflective of the collision of two continents. However, increasing evidence is emerging that some structures in these belts deform by extension (or stretching), a pattern opposite to the expectation. In some cases, the extension may be consequence of collapse of the high topography created by the collision. In this project, a research team from California Institute of Technology and Australian National University, will test if a major structure in the Alps deformed by extension. If so, the finding would shed new light on the complex processes that operate in major collisional mountain belts. The project would advance desired societal outcomes by: (1) full participation of underrepresented minorities in STEM through a high school mentoring program; (2) increased public scientific literacy and public engagement with science and technology through outreach activities; (3) development of a competitive STEM workforce through training of a graduate and an undergraduate student; and (4) increased partnerships through international collaboration.This project investigates the structural and low-temperature thermal history of the base of the Austroalpine allochthon in eastern Switzerland, representing the contact between the Adriatic microplate and various tectonostratigraphic units located along the southern margin of Europe. Published thermochronological and structural data in the region suggest that the fault may primarily be a normal fault, juxtaposing the allochthon against its structurally complex substrate, the Pennine Zone, at some point in early to mid-Tertiary time. In collaboration with the Australian National University, the research team will analyze eight transects across the southern part of the base of the allochthon in order to constrain the thermal histories of the Austroalpine and Penninic domains, and the structural transport direction(s) along and near the base. This project will constrain the cooling paths of from samples transects using (U-Th)/He and fission-track methods on apatite, zircon and where possible, titanite. The Australian National University group will constrain the cooling histories of the same samples, using white mica and potassium feldspar. This multiple-method approach across key contact zones will provide powerful new constraints on the origin and emplacement of the allochthon. A normal fault origin for the base of the allochthon (cold rocks emplaced over hot), if correct, will have first-order implications not only for the assembly of this iconic orogen, but for convergent orogens in general.