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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=708256
• 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。在整个地球历史中，这些碰撞带产生了影响长期全球气候模式的广阔山脉带，并将地壳碎片缝合在一起，形成稳定的板块和过去的超级大陆。虽然这是塑造地球地壳结构的一个基本过程，但我们对这些复杂和动态系统的理解还远未完成。 加拿大科迪勒拉山脉为研究大型碰撞造山带内所有地壳层次的过程提供了极好的机会。我的研究计划的首要主题是关注导致整个科迪勒拉造山系统发展的过程。反过来，这提供了关键的洞察力的基本过程是共同的所有大型造山系统，并允许更准确地比较科迪勒拉与其他类似的大型碰撞造山带，如喜马拉雅山和格伦维尔。 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，专注于变形和变质过程，活跃在造山带的最深层次。我的研究表明，变质基础记录了漫长的中生代变质作用，重熔熔融和韧性流动的历史。我建议测试的假设，源于这些贡献。 假设1：）加拿大南部科迪勒拉的变质基础设施从中侏罗世到古近纪时期在向东北扩展的高原之下演化。到白垩纪中期，假设的高原可能已经超过500公里，海拔5公里，略大于南美洲安第斯山脉的高原。这对加拿大科迪勒拉山脉的构造演化建模和白垩纪北美的古气候建模都有重要意义，假设高原的比例会影响到北美大陆的天气模式，以类似的方式穿越今天的高原。 在高原下的中下部地壳水平，变形可能是由贯穿的韧性流动，而不是由离散的逆冲岩席的堆叠。流动的风格演变从一个广泛的，分布拆离带，初期的通道流和重力扩张所带来的广泛的深源熔融的高峰期和造山作用的衰退阶段。 假设2：）以前的研究表明，在加拿大科迪勒拉北方的构造发展和历史的加积是不同步的南部。然而，从我的研究计划的结果使我建议有一个中生代的同步性之间各自的变质基础设施。此外，育空地区的中生代基础设施可能是热液流体的来源，导致克朗代克-白金矿区内的造山金开发。 将利用最先进的结构、岩石学和热年代学分析，在科迪勒拉造山带的变质基础结构内，沿走向进行由HQP领导的补充研究。产生的数据将用于测试高原的存在，限制其高度，宽度，持续时间和折返，并测试其发展是否与北方科迪勒拉的变质基础设施同步。这些结果也将被用来约束参数的建模，将试图模拟的发展，科迪勒拉基础设施，高原和风格的韧性流下面。