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

该奖项将支持对地壳部分的岩石学和地球化学研究，这些地壳部分被捡起并嵌入火山岩（捕虏体）中，这些火山岩曾被印加人用来建造秘鲁的库斯科市。人们对安第斯山脉这部分的地质历史仍然知之甚少，特别是对高原地区的高海拔特征的原因知之甚少。待分析的岩石取样于高原地壳的最深处，而在该地区其他任何地方都没有暴露出来。预计这些结果将使我们对大陆最深处在山区是如何演变的有新的认识。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方面的科学合作。该项目的成果将被纳入亚利桑那大学的教学课程，并将作为培养硕士学生和本科生的基础。由于火山岩是印加人在库斯科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。拟对秘鲁Altiplano高原最北端第四纪火山岩中新发现的下地壳捕虏体进行岩石学、热气压学、地球化学、同位素和年代学研究。至少有8个单独的熔岩流含有捕虏体。总之，它们是第二次在高原发现的地壳捕虏体，可以为高原的起源和发展提供宝贵的信息。该资助将支持对地壳包体的研究，旨在(a)确定高原北部地壳增厚和变质作用的起始时间；(b)了解地壳变短主要是由西部（弧侧）或东部（褶皱和冲断带侧）的下垫物质驱动的；最后(c)量化岩浆作用对地壳增厚/加载的作用。这些捕虏体填补了我们收敛边缘岩石记录的一个重要空白。研究计划包括实地取样部分，然后是捕虏体的岩石学和岩石学研究。Sm-Nd和Lu-Hf石榴石年代学和单氮石U-Th-Pb年代学将用于确定变质作用的年龄，并结合含石榴石组合的热压研究。火成岩年代学和碎屑锆石年代学将分别用于确定Altiplano地壳岩浆侵入的年龄和约束变质沉积岩的起源。元素和放射性成因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。该项目后的主要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其他感兴趣的社区成员。

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.