Tectonic evolution of orogenic infrastructure, plateau development and collapse

造山基础设施的构造演化、高原发育与崩塌

• 批准号: RGPIN-2014-03808
• 负责人: Gibson, Daniel
• 金额: $ 2.7万
• 依托单位: Simon Fraser University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633770
• 关键词: Tectonic; evolution; orogenic; infrastructure; plateau

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.

大陆、微大陆和岛弧在构造板块汇聚的俯冲带上的碰撞是一种基本的造山过程，称为碰撞造山作用。在整个地球历史上，这些碰撞带形成了影响长期全球气候模式的广阔山带，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。虽然这是塑造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了解还远远不完整。加拿大的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造山系统发展的过程。反过来，这提供了对所有大型造山系统共同的基本过程的关键洞察，并允许更准确地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，变质构造记录了中生代变质、深熔和韧性流动的漫长历史。我建议检验源于这些贡献的假设。假设1：)从中侏罗世到古近纪，加拿大科迪勒拉南部的变质构造在向东北延伸的高原下演化。到白垩纪中期，假设的高原可能已经超过500公里宽，海拔5公里，略大于南美洲安第斯山脉的阿尔蒂普诺高原。这对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，假设一个高原比例的高原会以类似于今天穿越高原的方式影响整个北美大陆的天气模式。在高原下方的中下地壳层，变形很可能是由穿透性韧性流调节的，而不是通过离散的逆冲片的叠加来调节的。在造山作用的高峰期和衰退期，流动方式由广泛的分布拆离带演化为大范围深熔熔融所导致的初期沟道流动和重力扩散。假设2：)先前的研究表明，加拿大科迪勒拉北部的构造发展和地体增长历史与南部不同步。然而，我的研究项目的结果使我认为，它们各自的变质基础设施之间存在中生代的同步性。此外，育空的中生代基础设施可能是导致克朗代克-白金矿区内造山金矿开发的热液来源。HQP领导的补充研究将使用科迪勒造山带和沿走向的变质基础设施内最先进的结构、岩石学和热年代学分析。产生的数据将用于测试高原的存在，限制其高度、宽度、持续时间和身体挖掘，并测试其发展是否与科迪勒拉北部的变质基础设施同步。这些结果还将被用来约束建模参数，这些参数将试图模拟科迪勒基础设施的发展、高原和其下的延性流动类型。