Collaborative Research: Testing the Timescale and Geometry of Incremental Pluton Assembly Through 3-D Modeling and Thermochronology

合作研究：通过 3D 建模和热年代学测试渐进式冥王星组装的时间尺度和几何形状

• 批准号: 0538094
• 负责人: John Bartley
• 金额: $ 5.9万
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-01-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0538094&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; Timescale; Geometry

This research is designed to test the hypothesis that plutons record geochronologic, thermochronologic and field evidence for incremental assembly. Although suggested by theoretical considerations, geochronologic and field data in support of incremental growth (particularly over millions to tens of millions of years) are hotly debated. Hornblende, biotite and potassium-feldspar argon thermochronology of rocks in the Sierra Nevada batholith are being used to address several broad questions. First, slow incremental pluton assembly has largely been inferred from uranium-lead zircon ages, and argon-argon dates from the same samples are providing a robust test of the reliability of the uranium-lead results. Second, if large "homogeneous" plutons were assembled incrementally, then contacts between increments have been overlooked in the field, and new mapping using bulk rock magnetic susceptibility is being used to identify cryptic contacts. Finally, modeling pluton and wall rock temperature histories indicates that cooling paths are sensitive to both the rate and the geometry of incremental pluton assembly. Therefore, cooling histories based on the zircon and titanite uranium-lead systems, and hornblende, biotite and potassium-feldspar argon systems, are being compared to modeled cooling histories in order to resolve spatial arrangements of intrusive increments and the rates at which they are added. This research is addressing the physical and chemical evolution of magma chambers, including mechanisms of intrusion, development of pluton fabrics, and permissible magmatic differentiation processes. The complex thermal histories of plutons and their wall rocks suggested by our modeling bear on interpretation of hornblende argon-argon dates from plutons; the maximum temperatures and durations of contact metamorphism; the thermal, structural and petrologic evolution of early intrusions as they become the wall rocks for later intrusions; the interpretation of paleomagnetic data collected from plutons; and the extent to which formation of large-volume eruptible magma bodies is recorded by plutons. This research focuses on the rates of assembly of magma chambers that feed volcanoes at the surface of the Earth. It employs a variety of dating techniques that act as checks and balances on each other in an effort to understand how, and how fast, the magma bodies are constructed, and their potential for catastrophic eruption. The incremental assembly hypothesis predicts that growth of "super volcano" magma chambers will be profoundly different than the construction and thermal histories of magma chambers that feed other volcanoes. We should be able to use this understanding to assess the potential for catastrophic eruption of huge volcanic complexes such as Yellowstone. The research is supporting the Ph.D. research of a student from the University of North Carolina, as well as the educational activities of other M.Sc. and undergraduate students at the University of North Carolina and the University of Utah. The project includes the development of new collaborative ties between Los Alamos National Laboratory, New Mexico Tech, University of North Carolina, and the University of Utah. The research is also an ongoing part of our support of the National Parks. It is contributing to our efforts to update the geology exhibits in Yosemite National Park, and play a role in Ranger training for the Park.

这项研究的目的是检验假设，岩体记录的地质年代学，热年代学和现场证据的增量组装。虽然理论上的考虑，支持增量增长（特别是在数百万至数千万年）的地质年代学和现场数据的建议是激烈的辩论。内华达州岩基中岩石的角闪石、黑云母和钾长石氩热年代学正被用来解决几个广泛的问题。首先，缓慢增量的岩体组装在很大程度上是从铀-铅锆石年龄推断出来的，而来自相同样品的氩-氩年代测定为铀-铅结果的可靠性提供了一个可靠的测试。其次，如果大型“同质”深圳湾是增量聚集的，那么增量之间的接触在该领域就被忽视了，而使用大块岩石磁化率的新制图正在被用来识别神秘的接触。最后，模拟的岩体和围岩温度的历史表明，冷却路径是敏感的速率和增量岩体组装的几何形状。因此，冷却历史的锆石和钛铀矿铀铅系统的基础上，角闪石，黑云母和钾长石氩系统，进行比较，以解决侵入增量的空间布置和速度，他们被添加到模拟冷却历史。这项研究涉及岩浆房的物理和化学演化，包括侵入机制、深成岩组构的发展和允许的岩浆分异过程。我们模拟的岩体及其围岩复杂的热历史关系到对岩体的角氩-氩年龄的解释;接触变质作用的最高温度和持续时间;早期侵入体成为后期侵入体围岩时的热、构造和岩石学演化;从岩体收集的古地磁数据的解释;以及深成岩体记录了大体积可喷发岩浆体形成的程度。这项研究的重点是在地球表面供给火山的岩浆房的组装速度。它采用了各种各样的测年技术，这些技术相互制衡，以了解岩浆体的构造方式和速度，以及它们发生灾难性喷发的可能性。增量组装假说预测，“超级火山”岩浆房的增长将与其他火山的岩浆房的建造和热历史有着深刻的不同。我们应该能够利用这种认识来评估像黄石公园这样的巨大火山复合体灾难性喷发的可能性。这项研究正在支持博士学位。来自北卡罗来纳州大学的一名学生的研究，以及北卡罗来纳州大学和犹他州大学的其他硕士和本科生的教育活动。该项目包括在洛斯阿拉莫斯国家实验室、新墨西哥州理工学院、北卡罗来纳州大学和犹他州大学之间建立新的合作关系。这项研究也是我们支持国家公园的一个持续部分。它有助于我们努力更新约塞米蒂国家公园的地质展品，并在公园的护林员培训中发挥作用。