Nature, Extent, and Timing of Ultrahigh-temperature Metamorphism, Acadian Orogen, Connecticut

在过去的二十年里，人们已经清楚地认识到，大陆地壳可以被加热到极端，超高？在变质作用和造山活动期间，大部分地区的温度（UHT）超过900°C（约1650°F）。地壳的变质岩如何达到如此极端的温度，仍然是地球科学中一个尚未解决的基本问题，它对岩石强度、岩浆的产生（岩浆可能从深处上升，产生矿床和火山喷发）、热传递和地球都有重大影响。S总体热量预算。该项目将重点关注康涅狄格州东北部新发现的UHT岩石，这是在美国发现的第一个区域UHT地点。在泥盆纪阿巴拉契亚造山期间，这些岩石在地表以下至少35公里（约22英里）的深处经历了大约1000°C（超过1800°F）的极端温度条件。这一发现将迫使人们重新思考阿巴拉契亚山脉深处的岩石是如何形成的，并为如何达到UHT条件提供了新的思路。此外，岩石中含有丰富的证据，表明在超高温下富含二氧化碳的流体曾经存在，因此可能对地壳中的碳循环和长期碳循环具有重要意义。将对超高温变质作用的基本假设进行检验，包括：从地幔中快速掘出；放射性成因地壳逆冲作用；asthenospheric上升流;机械应变加热；幔源岩浆的热输入；以及流体的热传递。基本数据收集将包括实地测绘地质关系；矿物的电子探针分析；岩石的整体化学分析；离子探针法测定锆石U-Pb年龄以及矿物和流体包裹体类型的微拉曼分析。这些数据将用于确定岩石的压力-温度-时间历史；地壳流体成分；由于铀、钍和钾的衰变而产生的放射性热；以及其他对假设检验至关重要的地质变量。该项目将支持和培训耶鲁大学的博士和本科生，并将研究成果整合到耶鲁大学皮博迪自然历史博物馆的公共科学推广项目中。

Over the past two decades it has become clear that the continental crust can be heated to extreme, ?ultrahigh? temperatures (UHT) in excess of 900 °C (about 1650 °F) over large regions during metamorphism and mountain building events. How metamorphic rocks of the crust reach such extreme temperatures remains a fundamental unresolved problem in the geosciences, with major implications for rock strength, generation of magmas (which may ascend from depth to produce ore deposits and volcanic eruptions), heat transfer, and Earth?s overall heat budget. This project will focus on newly-discovered UHT rocks in northeastern Connecticut, the first regional UHT locality found in the United States. The rocks underwent extreme temperature conditions of roughly 1000 °C (more than 1800 °F) at depths of at least 35 km (about 22 miles) below the surface during Appalachian mountain building in the Devonian Period. This discovery will force a rethinking of how the deep rocks of the Appalachian mountains were formed, and shed new light on how UHT conditions can be reached. Moreover, the rocks contain abundant evidence for the former presence of CO2-rich fluids at ultrahigh temperatures, and thus could have important implications for carbon cycling in the crust and the long-term carbon cycle. Fundamental hypotheses for UHT metamorphism will be tested including: rapid exhumation from the mantle; underthrusting of radiogenic crust; asthenospheric upwelling; mechanical strain heating; heat input from mantle-derived magmas; and heat transfer by fluids. Basic data collection will involve field mapping of geologic relations; electron microprobe analyses of minerals; bulk chemical analyses of rocks; U-Pb dating of zircons by ion microprobe; and micro-Raman analyses of mineral and fluid inclusion types. These data will be used to determine pressure-temperature-time histories for the rocks; crustal fluid compositions; radiogenic heat production due to the decay of uranium, thorium, and potassium; and other geologic variables critical for hypothesis testing. The project will support and train Yale Ph.D. and undergraduate students, and integrate research results into public science outreach programs at the Yale Peabody Museum of Natural History.