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How Are Ultrahigh Temperatures Attained in Continental Crust? A Petrochronological Investigation of the Basin and Range Lower Crust

大陆地壳中的超高温是如何达到的？

基本信息

批准号：
2025122
负责人：
Andrew Smye
金额：
$ 27.98万
依托单位：
Pennsylvania State Univ University Park
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-09-01 至 2024-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2025122&HistoricalAwards=false
关键词：
How Ultrahigh Temperatures Attained Continental

项目摘要

Continental crust that is rich in the element silicon appears to be unique to planet Earth and is critical for life, but the mechanisms that facilitate the long-term stability of this crust are unclear. Preservation of rocks that have attained temperatures greater than 900°C in the cores of old continents implies that ultrahigh temperature metamorphism and associated partial melting of the crust is critical for crustal stabilization. This research will address the primary question: How are extreme temperatures attained within the continental crust? The project will reconstruct the pressure-temperature-time history of rocks that were erupted from a section of continental lower crust that is actively undergoing ultrahigh-temperature metamorphism: the Basin and Range Province of the United States and Mexico. A combination of analytical techniques will discriminate between potential heat sources. The research will support an early career scientist, foster the training of a graduate student, and engage undergraduates in academic research.Characterizing how the Earth’s crust attains extreme temperatures is relevant to the development and distribution of body forces, flow of crust and chemical differentiation of the Earth. Using a suite of complementary techniques, this project will use xenoliths to test three hypotheses (crustal thickening, mantle thinning, or magmatic underplating) for the attainment of ultrahigh temperatures in continental lower crust beneath a zone of active extension. Accessory-mineral (zircon, monazite, titanite, and rutile) U-Pb dating and trace element depth-profiles will be used to derive the pressure and temperature history of the lower crust over the lifespan of the Basin and Range province. Lu-Hf garnet dates will be used to constrain the timing of prograde metamorphism. Petrologic constraints will be derived from Pressure-Temperature pseudo-sections, optimal thermobarometry, and trace-element thermometry. In conjunction, these techniques will be used to measure the timing and duration of ultrahigh temperatures in addition to portions of the prograde Pressure-Temperature evolution. The complete dataset will allow for rigorous testing of the three hypotheses.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

富含硅元素的大陆地壳似乎是地球独有的，对生命至关重要，但促进这种地壳长期稳定的机制尚不清楚。在古老大陆的核心中保存温度超过900°C的岩石，意味着低温变质作用和相关的地壳部分熔融对地壳稳定至关重要。这项研究将解决主要问题：极端温度是如何在大陆地壳内达到的？该项目将重建岩石的压力-温度-时间历史，这些岩石是从正在积极经历超高温变质作用的大陆下地壳的一部分喷发出来的：美国和墨西哥的盆地和山脉省。分析技术的组合将区分潜在的热源。这项研究将支持一名早期职业科学家，促进研究生的培训，并使本科生参与学术研究。描述地壳如何达到极端温度与体力的发展和分布，地壳流动和地球化学分异有关。利用一套补充技术，该项目将使用捕虏体来检验三种假设（地壳增厚、地幔变薄或岩浆底侵作用），以确定活跃伸展区下方的大陆下地壳是否达到过冷温度。矿物（锆石，独居石，钛铁矿和金红石）U-Pb测年和微量元素深度剖面将被用来推导盆地和山脉省的生命周期的下地壳的压力和温度历史。Lu-Hf石榴石年龄将被用来约束的时间的俯冲变质作用。岩石学约束将来自压力-温度伪截面、最佳热压法和微量元素测温法。结合使用，这些技术将用于测量除部分压力-温度演变外的温度变化的时间和持续时间。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。