Testing Jura-Cretaceous Terrane Displacement Hypotheses - a Critical Piece of the Cordilleran Puzzle

测试汝拉-白垩纪地体位移假说——科迪勒拉拼图的关键部分

• 批准号: RGPIN-2022-03143
• 负责人: Gibson, Daniel
• 金额: $ 2.19万
• 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: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=751141
• 关键词: Testing; Jura; Cretaceous; Terrane; Displacement

Collision of crustal fragment at convergent plate boundaries (subduction zones) is a fundamental mountain building process called accretionary orogenesis. It is important for us to better understand this process because it gives rise to expansive mountain belts (orogens), profoundly influencing long-term global climate patterns, hosts multiple styles of ore deposits, and creates some of the most hazardous geologic environments on Earth. The North American Cordillera is a classic accretionary orogen that is a product of protracted oblique convergence with oceanic plates along the continent's western margin for >200 million years. Changes in the obliquity over time led to tectonic settings that switched between compressional and extensional regimes, both accompanied by varying degrees of left-handed (sinistral) and right-handed (dextral) lateral shearing. This shearing imparted southward and then northward displacements of outer western portions of the Cordilleran orogen. Many of the structures and other geological relationships used to assess these displacements have been obscured by younger overprinting events. The resulting uncertainty in estimates for these displacements (100's to 1000's km) hinders our ability to reconstruct the geologic evolution of western North America and is one of the most controversial aspects of Cordilleran geology. The long-term vision of my research program is to apply my research strengths in innovative ways to unravel complex and enigmatic processes involved in mountain building and facilitate analysis of secular changes of tectonic processes throughout Earth history. Over the next 5 years, the proposed research will focus on testing hypotheses that suggest >800 km southward displacement of the outer western portion of the Cordillera in Late Jurassic-Early Cretaceous time. Short-term objectives involve dating of structural and petrologic processes coupled with detailed field investigations within southwest BC and Yukon where critical geological relationships will be carefully analyzed using state-of-the-art techniques. Specifically, we will: 1) Test hypotheses that invoke significant southward displacement of western portions of the Cordillera in Late Jurassic-Early Cretaceous time, and (2) Evaluate alternative hypotheses that suggest the western Cordillera is separated by a Cretaceous suture zone from the more inboard portion of the Cordillera. Our findings will provide a more sophisticated understanding of Cordilleran mountain building processes. This will benefit a broad base of researchers working on similar problems in the Cordillera and worldwide. Canadian Industry will also benefit from the additional insight that can help inform exploration strategies for ore deposits in Yukon and BC.

地壳碎片在会聚板块边界（俯冲带）的碰撞是一个基本的造山过程，称为增生造山作用。对我们来说，更好地理解这一过程很重要，因为它产生了广阔的山脉（造山带），深刻地影响了长期的全球气候模式，拥有多种类型的矿床，并创造了地球上最危险的地质环境。北美科迪勒拉山脉是一个典型的增生造山带，是与大洋板块沿大陆西缘沿着长期斜向会聚的产物，时间超过2亿年。随着时间的推移，结晶度的变化导致了构造环境在挤压和拉伸机制之间切换，两者都伴随着不同程度的左旋（左旋）和右旋（右旋）横向剪切。这种剪切作用使科迪勒拉造山带的外西部先向南，然后向北移动。许多用于评估这些位移的结构和其他地质关系已被较新的叠印事件所掩盖。由此产生的不确定性估计这些位移（100到1000公里）阻碍了我们的能力，重建北美西部的地质演化，是最有争议的方面之一，科迪勒拉地质。 我的研究计划的长期愿景是以创新的方式应用我的研究优势，以解开复杂和神秘的过程中涉及的造山运动，并促进整个地球历史的构造过程的长期变化的分析。在接下来的5年里，拟议的研究将侧重于测试假设，这些假设表明在晚侏罗世-早白垩世时期，科迪勒拉的外部西部向南位移>800公里。短期目标包括确定构造和岩石学过程的年代，并在不列颠哥伦比亚省西南部和育空地区进行详细的实地调查，使用最先进的技术仔细分析关键的地质关系。具体而言，我们将：1）测试假设，调用在晚侏罗世-早白垩世时间的科迪勒拉西部的显着向南位移，（2）评估替代假设，表明西科迪勒拉是由白垩纪缝合带从科迪勒拉更内侧的部分分开。我们的研究结果将提供一个更复杂的理解科迪勒拉山脉的建设过程。这将使科迪勒拉山脉和全世界研究类似问题的广泛研究人员受益。加拿大工业也将受益于额外的洞察力，可以帮助通知勘探战略的矿床在育空地区和不列颠哥伦比亚省。