Development of a 4-D Model of Crustal Evolution in the Northern Rocky Mountains

为了优化落基山脉北部/大平原地球范围(ES)资源的当前和未来部署，来自佛罗里达大学、蒙大拿州立大学和美国地质调查局的一组地球科学家正在进行研究，旨在为该地区的地壳演化建立一个综合的时间和空间(即4-D)框架。特别是，该地区包含北美大陆地壳最神秘的部分之一--大瀑布构造带(GFTZ)。这种长寿的地壳结构在时间上是北美最广泛的岩石记录(年龄可达40亿年)，并对该地区的地质史产生了重大影响，包括年轻的断裂和地震活动、岩浆活动和矿藏的分布以及资源丰富的沉积盆地的形成。例如，约18亿年前开发的GFTZ和Trans-Hudson造山带的交汇处，现在是一个主要的石油资源省-威利斯顿盆地的所在地。同样，落基山脉北部显生宙的构造复活、岩浆作用、地震活动和成矿作用集中在GFTZ，这导致了古代构造和事件如何控制现代地球过程和资源分布的额外可能性。研究小组正在将现代地质年代学(离子探针U-Pb)、热年代学(多和单颗粒40Ar-39Ar)和地球化学(常量和微量元素)技术应用于露头、深部试井和捕虏体(通过火山喷发带到地表的地幔和下地壳碎片)的样品中。这些结果将对优化ES资源的部署和最终为北美落基山脉北部/大平原北部开发一个综合的4-D框架至关重要。这一四维框架对于：1)解开地质记录中最有趣的大陆形成事件之一--劳伦斯式北美的形成；2)了解合并碰撞事件是如何记录在地壳和地幔中的；以及3)这些古代事件在多大程度上影响了落基山脉北部/大平原的地壳和岩石圈演化。研究小组利用了所有三个组织(佛罗里达大学、蒙大拿州立大学和美国地质调查局)的设施。研究生和本科生的参与正在提供关键的地质学和分析技能方面的劳动力培训。这项研究的结果将被整合到蒙大拿州州立大学正在开发的不断演变的蒙大拿州地理信息系统/数字高程模型地质图库中。所有的地球化学和地质年代学数据将以交互式网络格式在数字和空间上显示，地球科学家、教育工作者和普通公众都可以访问。结果还将通过会议报告和同行评议的期刊进行传播。

0545751MuellerIn order to optimize current and future deployment of EarthScope (ES) resources in the northern Rocky Mountains/Great Plains, a group of earth scientists from the University of Florida, Montana State University, and the U.S. Geological Survey are conducting research directed toward development of an integrated temporal and spatial (i.e., 4-D) framework for crustal evolution in this region. In particular, this region contains one of the most enigmatic segments of continental crust in North America, the Great Falls tectonic zone (GFTZ). This long-lived crustal structure has the most temporally extensive rock record in North America (ages to 4 billion years) and has had a major impact on the geologic history of this region, including younger episodes of faulting and seismicity, distribution of magmatism and ore deposits, and the creation of resource-rich sedimentary basins. For example, the intersection of the GFTZ and Trans-Hudson orogen, which developed ~ 1.8 billion years ago, is now the site of a major petroleum resource province, the Williston basin. Similarly, Phanerozoic structural reactivation, magmatism, seismicity, and mineralization in the northern Rocky Mountains is concentrated in the GFTZ, which leads to additional possibilities of how ancient structures and events may control modern earth processes and the distribution of resources.The research group is applying modern geochronologic (ion probe U-Pb), thermochronologic (multi-and single grain 40Ar-39Ar), and geochemical (major and trace elements) techniques to samples from outcrops, deep test wells, and xenoliths (pieces of the mantle and lower crust brought to the surface via volcanic eruptions). These results will be critical for both optimizing the deployment of ES resources and ultimately developing an integrated 4-D framework for the northern Rocky Mountain/northern Great Plains portion of North America. This 4-D framework is essential to: 1) unraveling one of the most intriguing episodes of continent formation in the geologic record, the formation of Laurentian North America; 2) understanding how the amalgamating collisional events were recorded in the crust and mantle; and 3) to what extent these ancient events affected subsequent crustal and lithospheric evolution in the northern Rocky Mountains/Great Plains. The research team is utilizing facilities from all three organizations (University of Florida, Montana State University, and the U.S. Geological Survey). Student participation at the graduate and undergraduate level is providing critical workforce training in geologic and analytical skills. The results of this research will be integrated into the evolving Montana GIS/DEM geologic map base being developed at Montana State University. All of the geochemical and geochronologic data will be numerically and spatially displayed in an interactive web format and accessible to geoscientists, educators, and the general public. Results will also be disseminated via meeting presentations and peer reviewed journals.