Tectonic evolution of orogenic infrastructure, plateau development and collapse

大陆、微大陆和岛弧在板块汇聚的俯冲带的碰撞是一个基本的造山过程，称为碰撞造山作用。在整个地球历史上，这些碰撞带产生了扩张的山带，影响了长期的全球气候模式，并将地壳碎片缝合在一起，形成了稳定的克拉通和过去的超级大陆。虽然这是形成地球地壳结构的一个基本过程，但我们对这些复杂而动态的系统的理解还远远不够。加拿大科迪勒拉为研究大型碰撞造山带内所有地壳水平的过程提供了极好的机会。我的研究计划的主要主题是关于导致整个科迪勒拉造山系统发展的过程。反过来，这为所有大型造山带共同的基本过程提供了关键的见解，并允许将科迪勒拉与其他类似的大型碰撞造山带（如喜马拉雅和格伦维尔）进行更准确的比较。我目前的研究重点是加拿大科迪勒拉的构造变质基础设施，重点是在造山带最深处活跃的变形和变质过程。我的研究表明，变质基础设施记录了一段漫长的中生代变质、成岩熔融和韧性流动的历史。我建议检验源自这些贡献的假设。假设1)中侏罗世至古近纪，加拿大南部科迪勒拉的变质基础设施在一个向东北扩展的高原下演化。到白垩纪中期，这个假定的高原可能已经超过500公里宽，海拔5公里，比南美洲安第斯山脉的高原略大。这对于模拟加拿大科迪勒拉的构造演化和白垩纪北美的古气候模型都有重要的意义，假设高原的比例会影响穿越北美大陆的天气模式，就像今天穿越高原的天气模式一样。在高原之下的中下地壳水平，变形可能是由穿透性韧性流动调节的，而不是由离散逆冲片的堆积调节的。在造山运动的鼎盛和衰退期，流型由广泛分布的拆离带演变为早期的河道流和广泛的复溶岩融化带来的重力扩张。假设2)以往的研究表明，加拿大北部科迪勒拉地区的构造发育和陆块增生历史与南部不同步。然而，我的研究项目结果使我认为它们各自的变质基础设施之间存在中生代同步性。此外，育空地区的中生代基础设施可能是热液流体的来源，导致了克朗代克-白金带内的造山带金矿发育。将利用最先进的构造、岩石学和热时学分析，在科迪勒拉造山带两侧和沿走向的变质基础设施内进行hqp主导的补充研究。所产生的数据将用于测试高原的存在，限制其高度、宽度、持续时间和挖掘，并测试其发展是否与科迪勒拉北部的变质基础设施同步。这些结果还将用于约束建模参数，这些参数将试图模拟科迪勒拉基础设施、高原及其下方韧性流的发展。

The collision of continents, microcontinents, and island arcs at subduction zones where tectonic plates converge is a fundamental mountain building process referred to as collisional orogenesis. Throughout Earth’s history, these collision zones give rise to expansive mountain belts that influence long-term global climate patterns, and have sutured crustal fragments together to create stable cratons and past supercontinents. Although a fundamental process in shaping Earth’s crustal architecture, our understanding of these complex and dynamic systems is far from complete. The Canadian Cordillera provides excellent opportunity to study processes at all crustal levels within a large collisional orogen. The overarching theme of my research program is concerned with the processes that led to the development of the entire Cordilleran orogenic system. In turn, this provides critical insight into the fundamental processes that are common to all large orogenic systems, and allow for a more accurate comparison of the Cordillera with other similarly large collisional orogens, such as the Himalaya and Grenville.My current research emphasis is on the tectono-metamorphic infrastructure of the Canadian Cordillera, focusing on deformational and metamorphic processes that were active in the deepest levels of the orogen. My research has demonstrated that the metamorphic infrastructure records a protracted history of Mesozoic metamorphism, anatectic melting and ductile flow. I propose to test hypotheses that stem from these contributions.Hypothesis 1:) The metamorphic infrastructure of the southern Canadian Cordillera evolved beneath a northeastward propagating plateau since Middle Jurassic to Paleogene time. By mid-Cretaceous time the hypothesized plateau may have been greater than 500 km across and 5 km above sea level, slightly bigger than the Altiplano plateau in the South American Andes. This has important implication both for modeling the tectonic evolution of the Canadian Cordillera and for paleoclimate modeling of Cretaceous North America assuming a plateau of Altiplano proportions would have affected the weather patterns moving across the North American continent in a similar fashion to that crossing the Altiplano today. In the mid- to lower crustal levels beneath the plateau, deformation was likely accommodated by penetrative ductile flow, not by stacking of discrete thrust sheets. The style of flow evolved from a broad, distributed detachment zone, to incipient channel flow and gravitational spreading brought on by widespread anatectic melting during the peak and waning stages of orogenesis. Hypothesis 2:) Previous research suggests the tectonic development and history of terrane accretion in the northern Canadian Cordillera is out of sync with the south. However, results from my research program lead me to suggest there is a Mesozoic synchroneity between their respective metamorphic infrastructures. Additionally, the Mesozoic infrastructure in Yukon may have been a source of hydrothermal fluids that led to orogenic gold development within the Klondike-White Gold districts.Complementary HQP-led studies will be undertaken using state-of-the-art structural, petrological and thermochronometric analyses within the metamorphic infrastructure both across, and along strike, of the Cordilleran orogen. The data generated will be used to test the existence of the plateau, constrain its height, width, duration and exhumation, and to test if its development was synchronous with the metamorphic infrastructure in the northern Cordillera. These results will also be used to constrain parameters for modeling that will attempt to simulate the development of the Cordilleran infrastructure, the plateau and the style of ductile flow beneath it.