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，例如地壳深处致密岩浆岩的添加或去除。 这些运动的表现之一是大型洼地的下沉，这些洼地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，深度可达 10 公里或更深。这些盆地中的岩石经历加热并与渗透水发生反应，然后由于后来的地壳运动而抬升和侵蚀。这些伟大的埋藏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（包括石油、天然气和矿床）的熔炉。 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，它既反映了驱动沉降和隆起的潜在力量，又控制着与石油和矿石形成相关的化学过程。该项目将为研究发掘盆地中暴露的沉积岩的温度历史提供新的工具，重点关注暴露在大峡谷内部和周围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”在较低温度下会大量形成，从而产生一种测温法。而且，这些同位素团块只能通过高于一定温度的原子扩散来形成或分散，这就引入了第二种方式，即热历史的差异可以通过同位素组成的差异来记录。这项技术是大约十年前发明的，但直到最近才被充分理解，可以用作解开挖出盆地神秘且通常复杂的热历史的工具。 这项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，其热历史已被广泛研究，但其碳酸盐岩为主的地层尚不适合现有技术。团块同位素测温法在该地区石灰岩中的应用将补充并建立在早期研究成果的基础上。其次，科罗拉多高原的剥露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。 该项目也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域的了解。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，包括对新兴同位素技术的博士后学者进行培训，以及为本科生和高中生提供 STEM 的研究机会（科学、技术、工程和数学）学科。该提案利用碳酸盐团块同位素测温法研究了科罗拉多高原的埋藏、隆升和折返历史。在埋藏和折返环境中，碳酸盐矿物的团块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，发生在方解石为 90-180 摄氏度，白云石为 ~250-300 摄氏度。这些温度范围对于盆地演化和碳氢化合物勘探研究非常重要，但传统的低温测温法仅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，以补充裂变径迹和铀-钍/氦热测时法等更知名的工具。特别是，他们将描述科罗拉多高原地层中团块同位素表观温度的分布，包括通过暴露和取芯部分的垂直横断面以及区域尺度水平梯度。这些数据将与现有的对聚集同位素重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（基于垂直横断面）；这些导出的量将用于推断科罗拉多高原最大埋藏深度的分布和总折返模式（在适当情况下，结合现有的铀-钍/氦和裂变径迹数据）。更一般地说，这将是首次使用簇同位素约束对大规模构造特征的埋藏和挖掘进行详细研究。拟议的工作将增进对科罗拉多高原埋藏、隆起和折返历史的了解，更广泛地了解构造活动与地表过程之间的相互作用。