Burial, Uplift and Exhumation History of the Colorado Plateau

地壳处于动态运动中，这是由板块构造和一些鲜为人知的过程驱动的，比如地壳深处致密岩浆岩的增加或移除。这些运动的一种表现是大型洼地的下沉，这些洼地在下沉的过程中不断充满沉积物，形成了巨大的沉积岩盆地，这些盆地通常有数百公里宽，深度达到10公里以上。这些盆地中的岩石经历了加热和与渗透水的反应，然后由于后来的地壳运动而上升和侵蚀。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，也是关键地质资源——包括石油、天然气和矿藏——形成的坩埚。也许控制盆地地质过程的最重要因素是温度随时间的变化，它既反映了驱动沉陷和隆升的底层力量，也控制着与石油和矿石形成有关的化学过程。这个项目将带来一种新的工具，用于研究在出土盆地中暴露的沉积岩的温度历史，重点是科罗拉多高原的石灰岩，这些石灰岩暴露在大峡谷内部和周围。我们将使用“团块同位素测温法”来解决这个问题——这是一种检测稀有的、天然存在的碳和氧同位素在矿物结构的原子晶格中彼此形成键的程度的技术。这些同位素“团块”在较低的温度下形成的丰度更高，从而产生了一种测温方法。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，这就引入了第二种方法，即通过同位素组成的差异来记录热历史的差异。这项技术发明于大约10年前，但直到最近才被充分理解，可以作为一种工具来解开被挖掘出的盆地的神秘而复杂的热历史。本研究的重点是科罗拉多高原，因为它是北美主要的构造和地形域之一，其热史已被广泛研究，但其碳酸盐岩占主导地位的地层尚未适用于现有的技术。块状同位素测温法在该地区石灰石中的应用将补充和建立在早期研究的基础上。其次，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态。该项目还将成为一种方法的试验场，该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深层地壳水的理解。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了贡献，包括培养一项新兴同位素技术的博士后学者，以及为本科生和高中生提供STEM（科学、技术、工程和数学）学科的研究机会。本研究利用碳酸盐块状同位素测温技术，研究了科罗拉多高原的埋藏、隆起和挖掘历史。在埋藏和挖掘环境中，碳酸盐矿物的块状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、再结晶、脉状形成）的温度和同位素流动记录的温度-时间阈值，方解石的温度为90-180摄氏度，白云岩的温度为~250-300摄氏度。这些温度范围在研究盆地演化和油气勘探中具有重要意义，但常规的低温热时测定法只能部分覆盖这些温度范围。主要研究人员的研究将带来新的限制，以补充更知名的工具，如裂变径道和铀-钍/氦热时计。特别是，它们将表征科罗拉多高原地层中团块同位素表观温度的分布，包括通过暴露和岩心剖面的垂直断面以及区域尺度的水平梯度。这些数据将与现有的关于团块同位素重新排序速率的实验限制相结合，以限制峰值埋藏温度和峰值埋藏热梯度（基于垂直样条）；这些导出的数量将用于推断科罗拉多高原上最大埋藏深度的分布和总发掘模式（适当时，结合现有的铀钍/氦和裂变径迹数据）。更一般地说，这将是第一次使用团块同位素约束对大规模构造特征的埋葬和挖掘进行详细研究。这项提议的工作将促进对科罗拉多高原埋葬、隆起和挖掘历史的理解，更广泛地说，是对构造活动和地表过程之间相互作用的理解。

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.