Constraints on Plateau Architecture and Assembly From Deep Crustal Xenoliths, Northern Altiplano (Southern Peru)

该奖项将支持对部分地壳的岩石学和地球化学研究，这些部分被提取并嵌入曾被印加人用来建造秘鲁库斯科城的火山岩(包体)中。安第斯山脉这一部分的地质历史仍然知之甚少，特别是被称为高原的高海拔地区的原因。要分析的岩石采样了高原地壳最深的部分，这些部分没有暴露在该地区的其他任何地方。预计这些结果将使我们对大陆最深处是如何在山区演化的有一个新的了解。这项研究还将促进与秘鲁和智利专家在当地和区域安第斯地质学方面的科学合作。该项目的结果将纳入亚利桑那大学的教学课程，并将作为培养理科硕士的基础。学生和本科生也是如此。由于火山岩是库斯科印加人使用的主要建筑材料，从这个项目中获得的知识可能会影响我们对这个著名遗址的考古学的理解。对秘鲁高原最北端第四纪火山岩中新发现的下地壳捕虏体进行了岩石学、热压法、地球化学法、同位素和年代学研究。至少有8个单独的熔岩流含有捕捉体。它们加在一起，是已知的第二次发现来自高原的地壳捕虏体，可以提供关于高原起源和发展的宝贵信息。该奖项将支持对地壳捕捉体的研究，其目的是：(A)解决北部高原下地壳增厚和变质作用开始的时间问题；(B)了解地壳缩短主要是由来自西部(弧侧)或东部(褶皱和冲断带一侧)的底侵物质驱动的；以及(C)量化岩浆作用对地壳增厚/加载的作用。这些包体填补了我们汇聚边缘岩石记录中的一个重要空白。研究计划包括野外采样部分，然后是对捕虏体的岩石学和岩石学研究。Sm-ND和Lu-Hf石榴石年代学和独居石U-Th-Pb年代学将结合含石榴石组合的温压研究来确定变质年龄。火成岩和碎屑锆石年代学将分别用于确定阿尔蒂普拉诺地壳中岩浆侵入的年龄，并限制变质沉积岩的来源。元素和放射性成因的同位素地球化学将进一步阐明这里研究的组合的起源和地壳年龄。这个项目之后的主要交付成果是一份将提交给学术期刊的手稿。从这项研究中收集的样本将提供给社会上其他感兴趣的成员。

This award will support a petrologic and geochemical study of the portions of the crust that were picked up and embedded in volcanic rocks (xenoliths) once used by the Incas to build the city of Cuzco, in Peru. The geologic history of this part of the Andes is still poorly understood, specifically the reason for the high altitude that characterizes the region called the Altiplano. The rocks to be analyzed sampled the deepest portions of the crust in the Altiplano that are not exposed anywhere else in the region. It is expected that the results will provide us with a new understanding of how the deepest portions of continents evolve in mountainous areas. This study will also foster scientific collaborations with Peruvian and Chilean experts on local and regional Andean geology. Results of this project will be incorporated into the teaching curriculum at the University of Arizona, and will serve as the basis for the training of a M.Sc. student and also that of an undergraduate student. Because the volcanic rocks were the main building materials used by the Incas in Cuzco, knowledge derived from this project may impact our understanding of archeology in this famous heritage site. It is proposed to conduct a petrographic, thermobarometric, geochemical, isotopic and geochronologic study of newly discovered lower crustal xenoliths in Quaternary volcanic rocks from the northernmost Altiplano Plateau, Peru. At least eight individual lava flows contain xenoliths. Together, they are the second known occurrence of crustal xenoliths from the Altiplano and can provide invaluable information about the plateau's origin and development. This award will support a study of the crustal xenoliths aimed at (a) resolving the timing of crustal thickening and metamorphism initiation under the northern Plateau, (b) understanding whether crustal shortening was primarily driven by material underplated from the west (arc-side) or east (fold and thrust belt side), and finally (c) quantifying the role of magmatism to crustal thickening/loading. These xenoliths fill an important gap in our convergent margin rock record. The research plan comprises a field-sampling component followed by a petrographic and petrologic study of xenoliths. Sm-Nd and Lu-Hf garnet geochronology and monazite U-Th-Pb geochronology will be used to determine the age of metamorphism in conjunction with a thermobarometric study of the garnet-bearing assemblages. Igneous and detrital zircon geochronology will be employed to determine the age of magmatic intrusions in the Altiplano crust, and to constrain the origin of metasedimentary rocks, respectively. Elemental and radiogenic isotopic geochemistry will further illuminate the origin and crustal age of the assemblages studied here. The main deliverable after this project is a manuscript that will be submitted to a scholarly journal. Samples collected from this study will be made available to other interested members of the community.