Collaborative Research: Assessment of the Role of Water in Cratonic Roots and their Post-Archean Margins on the Strength and Longevity of Continental Lithosphere

智力优点：这项合作提案要求提供3年的资金，通过傅里叶变换红外光谱法（FTIR）分析水在矿物中的橄榄岩捕虏体所带来的金伯利岩岩浆在火山及其边缘。在这个项目中引起的关键物理性质是水解弱化橄榄石（和潜在的辉石和石榴石）时发生的氢（H）被纳入作为微量元素的矿物缺陷，这些？名义上无水？矿物主要目的是测试Slave克拉通（加拿大）和西伯利亚克拉通（俄罗斯）岩石圈底部的橄榄石是否具有与Kaapvaal克拉通下可能观察到的相似的低含水量（以ppm H2O计算的H量）（Peslier等人，2010年a）。如果是这样的话，假设干燥的橄榄石在岩石圈的底部是一个强大的较低的岩石圈和更易变形的软流圈之间的高粘度对比部分负责将被证实为克拉通寿命的一般机制。如果Kaapvaal以外的克拉通在其岩石圈底部没有干燥的橄榄石，那么就必须提出克拉通长寿的其他机制，并且必须重新评估水在克拉通根生存中的作用。该建议的第二部分是探索克拉通边缘地幔矿物中的水分布，使用来自后太古代移动的带周围的卡普瓦尔克拉通（元古宙纳马夸-纳塔尔和Rehoboth盆地，南非和纳米比亚），并在基尔本孔（古生代大陆裂谷，南部新墨西哥州，美国）捕虏体，并破译这些地形的保存水的作用？外套根在建议书的所有部分，将对所有橄榄岩矿物（不仅是橄榄石）进行分析，以确定其在岩相学、主要元素和微量元素以及放射性同位素方面的特征。每个捕虏体套件将选择10个样品，涵盖尽可能广泛的平衡压力范围。将评估地幔中的熔融、交代作用或再受精作用对含水量的影响，以及寄主岩浆上升过程中的水分损失或增加。这项工作还将提供有关地幔矿物中氢形态的信息。然后将水含量纳入橄榄石组合的粘性蠕变规律，以估计其对地幔流变学的影响。该项目将提供有关地球动力学和大陆岩石圈历史和寿命的关键数据和制约因素。 分析将在NSF资助的FTIR上进行。两名研究生和两名本科生将从这项研究中受益。研究生将通过执行复杂的分析任务，结合数据的综合建模，提高他们在地球科学领域未来就业的技能。本科生将通过各种可用的实习，高级论文和勤工俭学计划包括在研究中。来自代表性不足人口的学生（休斯顿大学入学学生的很大一部分）将有重要的机会获得最先进的设备和岩石学和地球化学方面的尖端研究。这项合作是跨机构和国际性的，工作将在国际会议上提出，同行评审的论文将从这项研究中产生。这项工作的结果对于我们了解地球至关重要？地球动力学的地幔动力学，并将带来基础数据的科学家感兴趣的地球动力学建模，岩石变形，地震学，地幔热导率和电阻率，火山学，和大陆的历史。

Intellectual merit: This collaborative proposal requests funds for 3 years to analyze water by Fourier transform infrared spectrometry (FTIR) in minerals from peridotite xenoliths brought up by kimberlite magmas in cratons and their margins. The key physical property evoked in this project is the hydrolytic weakening of olivine (and potentially pyroxene and garnets) that occurs when hydrogen (H) is incorporated as a trace element in mineral defects of these ?nominally anhydrous? minerals. The main purpose is to test in the Slave craton (Canada) and the Siberian craton (Russia) whether the olivines at the bottom of the lithosphere have low water contents (amount of H calculated as ppm H2O) similar to what may be observed beneath the Kaapvaal craton (Peslier et al., 2010a). If this is the case, the hypothesis that dry olivines at the base of the lithosphere are in part responsible for a high viscosity contrast between a strong lower lithosphere and a more deformable asthenosphere would be confirmed as a general mechanism for craton longevity. If cratons other than the Kaapvaal do not have dry olivines at the bottom of their lithosphere, then other mechanisms will have to be proposed for craton longevity and the role of water in cratonic root survival will have to be re-assessed. A second part of this proposal is to explore the water distribution in mantle minerals at craton margins, using xenoliths from post-Archean mobile belts surrounding the Kaapvaal craton (Proterozoic Namaqua-Natal and Rehoboth terranes, South Africa and Namibia), and at Kilbourne Hole (Phanerozoic continental rift, southern New Mexico, USA), and decipher the role of water in the preservation of these terrains? mantle roots. In all parts of the proposal, all peridotite minerals (not only olivine) will be analyzed for water on well-characterized xenoliths in terms of petrography, major and trace elements, and radiogenic isotopes. Ten samples per xenolith suite will be selected, spanning the widest possible range of equilibration pressures. The effect on water content of melting, metasomatism or refertilization in the mantle, and water loss or gain during host magma ascent will be assessed. This work will also provide information on hydrogen speciation in mantle minerals. The water contents will then be incorporated into laws of viscous creep of olivine assemblages to estimate their effect on mantle rheology. This project will provide crucial data and constraints on Earth geodynamics and continental lithosphere history and longevity.Broader impacts. The analyses will be performed on a NSF-funded FTIR. Two graduate students, and two undergraduate students will benefit from this study. The graduate students will have enhanced their skills for future employment in the geosciences by performing complex analytical tasks in combination with comprehensive modeling of the data. Undergraduate students will be included in the research via various available internship, senior thesis, and work-study programs. Students from underrepresented populations (a large portion of enrolled students at the University of Houston) will have important access to state-of-theart equipment and cutting-edge research in petrology and geochemistry. The collaboration is cross-institutional and international, work will be presented at international conferences, and peer-reviewed papers will come out of this study. The results from this work will be crucial for our understanding of Earth?s mantle dynamics and will bring fundamental data to scientists interested in geodynamic modeling, rock deformation, seismology, mantle thermal conductivity and electrical resistivity, volcanology, and the history of continents.