Burial, Uplift and Exhumation History of the Colorado Plateau

科罗拉多高原的埋藏、抬升和挖掘历史

• 批准号: 1624827
• 负责人: John Eiler
• 金额: $ 34.8万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-15 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1624827&HistoricalAwards=false
• 关键词: Burial; Uplift; Exhumation; History; Colorado

The Earth's crust is in dynamic motion, driven by plate tectonics and less understood processes, like addition or removal of dense magmatic rocks in the deep crust. One manifestation of these motions is the sinking of large depressions that are continuously filled with sediment as they sink, creating great basins of sedimentary rock, often hundreds of kilometers across and reaching depths of 10 kilometers or more. Rocks in these basins experience heating and reaction with percolating water, before uplifting and eroding due to later crustal motions. These great cycles of burial and exhumation are responsible for creating some of the most important records of earth history, and are the crucibles where key geological resources are forged -- including petroleum, natural gas and ore deposits. Perhaps the most important factor controlling the geological processes in basins is the change in temperature with time, which both reflects the underlying forces driving subsidence and uplift, and controls the chemical processes associated with petroleum and ore formation. This project will bring to bear a new tool for the study of the temperature histories of sedimentary rocks exposed in exhumed basins, focusing on the limestones of the Colorado Plateau, which are exposed in and around the Grand Canyon. We will approach this problem using 'clumped isotope thermometry' -- a technique that examines the extent to which rare, naturally occurring isotopes of carbon and oxygen form bonds with one another in the atomic lattices of mineral structures. These isotopic 'clumps' form in greater abundance at lower temperatures, leading to a kind of thermometry. And, these isotopic clumps can only form or disperse by atomic diffusion above a certain temperature, introducing a second way in which differences in thermal history can be recorded in differences in isotopic composition. This technique was invented about a decade ago, but has only recently become well enough understood to be used as a tool for unraveling the cryptic, often complex thermal histories of exhumed basins. This research focuses on the Colorado Plateau because it is one of the major tectonic and topographic domains of North America and its thermal history has been studied extensively, yet its carbonate-dominated strata have not been amenable to established techniques. The application of clumped isotope thermometry to limestones of this region will complement and build on what has been learned by earlier studies. Second, the exhumation of the Colorado Plateau was associated with incision of the Grand Canyon, and our work will constrain the timing and dynamics of the formation of this important landscape. This project will also be a proving ground for a method that could be used to reconstruct thermal histories in many resource-rich sedimentary basins, expanding our understanding of petroleum and ore formation and of deep-seated crustal waters. In addition to the scientific objectives of the research, the project is contributing to other important societal goals, including the training of postdoctoral scholar in a new and emerging isotopic technique, as well as providing research opportunities for undergraduate and high school students in a STEM (science, technology, engineering, and mathematics) discipline. This proposal examines burial, uplift and exhumation history of the Colorado Plateau, using carbonate clumped-isotopes thermometry. In burial and exhumation settings, the clumped-isotope compositions of carbonate minerals constrain the thermal history of carbonate minerals, possibly including both temperatures of discrete events (cementation, recrystallization, vein formation) and temperature-time thresholds recorded by isotopic mobility, which occurs at 90-180 degrees celsius in calcites and ~250-300 degrees celsius in dolomites. These temperature ranges are important in the study of basin evolution and hydrocarbon exploration, but are only partially covered by conventional, low-temperature thermochronometry. The principal investigators research will bring new constraints that complement better known tools such as fission track and Uranium-Thorium/Helium thermochronometry. In particular, they will characterize the distribution of clumped-isotope apparent temperatures in strata of the Colorado Plateau, including both vertical transects through exposed and cored sections and regional scale horizontal gradients. These data will be combined with existing experimental constraints on the rates of clumped-isotope re-ordering to constrain peak-burial temperatures and peak-burial thermal gradients (based on vertical transects); these derived quantities will be used to infer the distribution of maximum burial depth and total-exhumation pattern across the Colorado Plateau (where appropriate, in combination with existing Uranium-Thorium/Helium and fission track data). More generally, this will be the first detailed study of burial and exhumation of a large-scale tectonic feature using clumped-isotope constraints. The proposed work will advance understanding of the Colorado Plateau burial, uplift and exhumation history, and more generally, of the interactions between tectonic activity and surface processes.

地壳处于动态运动中，受到板块构造和不太了解的过程的驱动，例如在地壳深处增加或移除致密的岩浆岩。 这些运动的一个表现是大型凹陷的下沉，这些凹陷在下沉时不断充满沉积物，形成巨大的沉积岩盆地，通常直径数百公里，深度达10公里或更深。这些盆地中的岩石经历了加热和与蒸发水的反应，然后由于后期地壳运动而抬升和侵蚀。这些巨大的埋葬和挖掘循环创造了地球历史上一些最重要的记录，也是锻造关键地质资源的熔炉，包括石油，天然气和矿床。 控制盆地地质作用的最重要因素也许是温度随时间的变化，它既反映了驱动沉降和抬升的基本力量，又控制了与石油和矿石形成有关的化学过程。该项目将为研究在挖出的盆地中暴露的沉积岩的温度历史带来一种新的工具，重点是在大峡谷内和周围暴露的科罗拉多高原的石灰岩。 我们将使用“聚集同位素测温法”来解决这个问题--这是一种检查稀有的、天然存在的碳和氧同位素在矿物结构的原子晶格中相互形成键的程度的技术。这些同位素“团块”在较低温度下形成的丰度更大，导致了一种测温法。而且，这些同位素团块只能在一定温度以上通过原子扩散形成或分散，从而引入了第二种方式，其中热历史的差异可以记录在同位素组成的差异中。这项技术是在大约十年前发明的，但直到最近才被充分理解，可以作为一种工具来解开挖掘盆地的神秘，往往是复杂的热历史。 这项研究的重点是科罗拉多高原，因为它是北美的主要构造和地形域之一，其热历史已被广泛研究，但其碳酸盐岩为主的地层还没有服从既定的技术。聚集同位素测温法在该地区石灰岩的应用将补充和建立在早期研究的基础上。第二，科罗拉多高原的发掘与大峡谷的切割有关，我们的工作将限制这一重要景观形成的时间和动力学。 该项目还将成为一个试验场，以检验一种方法，可用于重建许多资源丰富的沉积盆地的热历史，扩大我们对石油和矿石形成以及地壳深层沃茨的了解。除了研究的科学目标外，该项目还为其他重要的社会目标做出贡献，包括在新兴同位素技术方面培养博士后学者，以及为STEM（科学，技术，工程和数学）学科的本科生和高中生提供研究机会。本提案利用碳酸盐凝块同位素测温法研究了科罗拉多高原的埋藏、抬升和折返历史。在埋藏和折返环境中，碳酸盐矿物的聚集同位素组成限制了碳酸盐矿物的热历史，可能包括离散事件（胶结作用，重结晶，脉形成）的温度和同位素迁移率记录的温度-时间阈值，方解石中的温度为90-180 ℃，方解石中的温度为250-300 ℃。这些温度范围在研究盆地演化和油气勘探中很重要，但传统的低温热年代学方法只能部分地涵盖这些温度范围。主要研究人员的研究将带来新的限制，补充更知名的工具，如裂变径迹和铀钍/氦热计时。特别是，他们将表征聚集同位素表观温度在科罗拉多高原的地层，包括通过暴露和取芯部分和区域尺度水平梯度的垂直断面的分布。这些数据将与现有的实验约束条件相结合的速度聚集同位素重新排序，以限制峰值埋藏温度和峰值埋藏温度梯度（基于垂直断面）;这些派生的数量将被用来推断分布的最大埋藏深度和总的剥露模式在整个科罗拉多高原（在适当的情况下，结合现有的铀钍/氦和裂变径迹数据）。更一般地说，这将是第一个详细的研究埋葬和折返的大规模构造功能使用聚集同位素的限制。拟议的工作将促进对科罗拉多高原埋藏、隆起和折返历史的理解，更一般地说，将促进对构造活动和地表过程之间相互作用的理解。