Carbonate Clumped Isotope Thermometry of the Notch Peak Contact Metamorphic Aureole

是地球深处的水循环吗？地壳是一系列重要地质过程的基础，包括矿体的形成、地热田的热流以及地壳岩石和岩浆的热、矿学和化学演化。大多数地壳水循环发生在10公里以下的深度，因为在这个范围内，孔隙和裂缝在上覆岩石的压力下保持开放。我们对这一现象的理解面临的巨大挑战之一是，我们用来测量地壳上部岩石所经历的温度的工具通常只能提供半定量或相对的限制。而且，温度上的这种不确定性使人们难以确定与岩石发生反应的水的化学成分。由于这个原因，我们对地壳水-岩反应的最严格的把握仅限于侵入岩浆周围狭窄（约1公里）的热岩晕，在那里升高的温度驱动矿物反应，可以用作严格的温度约束。这个项目将使用一种最近发明的测温方法重新检查这个问题，该方法允许在地壳上部10公里的普遍温度范围内精确定量测量水-岩石反应的温度。这种名为“碳酸盐团块同位素测温法”的方法，是基于将方解石和白云石等矿物中稀有的碳和氧同位素组合成相同的分子群。这些稀有同位素分子的分析在技术上是具有挑战性的，但最近的质谱技术的创新使其成为可能，并导致了对过去气候、地球表面地形、断层温度、石油矿床的地质历史、恐龙体温和其他问题的研究取得了进展。该方法还应该确定与碳酸盐矿物共存的水的同位素组成，让人们“绘制”深度流体循环的地图。该项目将是该工具首次应用于深部地壳热化学演化的重大问题。研究区域位于犹他州的Notch Peak，该区域暴露得非常好，研究得也非常充分，这意味着该项目的测量结果可以与热量和流体分布的详细模型进行比较。该项目的预期结果是，该环境中温度和流体运移路径的定量预测模型将从围绕Notch峰岩浆侵入的狭窄热岩带扩展到更典型的地壳岩石的广阔周围区域。这一结果将有助于对矿体、油气田和热液能源的认识。

The circulation of water deep in the earth?s crust underlies a variety of highly significant geological processes, including formation of ore bodies, heat flow in geothermal fields, and the thermal, mineralogical and chemical evolution of crustal rocks and magmas. Most crustal water circulation occurs at depths of less than 10 kilometers because this is the range over which pores and fractures remain open against the pressure of overlying rocks. One of the great challenges to our understanding of this phenomenon is that our tools for measuring the temperatures experienced by rocks in this upper portion of the crust generally provide only semi-quantitative or relative constraints. And, this ambiguity in temperature confounds efforts to define the chemistry of waters that have reacted with rocks. For this reason, our firmest grip on crustal water-rock reaction is confined to narrow (~1 km) haloes of hot rock immediately surrounding intruding magmas, where elevated temperatures drive mineralogical reactions that can be used as rigorous temperature constraints. This project will re-examine this problem using a recently invented method of thermometry that allows for the precise quantitative measurement of temperatures of water-rock reaction over a wide range of temperatures common to the upper 10 km of the crust. This method, 'carbonate clumped isotope thermometry', is based on the grouping together of rare isotopes of carbon and oxygen into the same molecular groups in minerals such as calcite and dolomite. Analysis of these rare isotopic molecules is technically challenging but enabled by recent innovations in mass spectrometry, and has led to advances in the study of past climates, topography of the earth's surface, temperatures of faults, geologic histories of petroleum deposits, body temperatures of dinosaurs and other problems. The method should also define the isotopic compositions of waters that co-existed with carbonate minerals, letting one 'map' the circulation of fluid at depth. This project will be the first time this tool has been applied to a significant problem in the thermal and chemical evolution of the deep crust. The study area, Notch Peak, Utah, is exceptionally well exposed and well studied, meaning the results of this project's measurements can be compared to detailed models of the distribution of heat and fluids. An expected outcome of this project is that quantitative, predictive models of temperatures and fluid migration pathways in this environment will be extended out of the narrow belt of hot rocks that surrounds the Notch Peak magmatic intrusion and into the broad surrounding region of more typical crustal rocks. This result could lead to advances in understanding of ore bodies, oil and gas fields, and hydrothermal energy resources.