Collaborative Research: Testing Models for Extension in the Rio Grande Rift-Basin and Range Transition Zone of Southern New Mexico

合作研究：测试新墨西哥州南部里奥格兰德裂谷盆地和山脉过渡带的延伸模型

• 批准号: 1624538
• 负责人: Jason Ricketts
• 金额: $ 16.69万
• 依托单位: University of Texas at El Paso
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-15 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1624538&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; Models; Extension

The Basin and Range province and the Rio Grande rift in the western United States are two tectonic domains where the lithosphere has slowly pulled apart over the past 25 million years. The stretching is distributed across wide areas in the Basin and Range and is more focused along a narrow zone from southern New Mexico to northern Colorado in the Rio Grande rift, which in many ways resembles other significant rift zones around the world. A variety of tectonic models have been proposed to explain the extension in these two domains. Some models attribute their development to the same mechanisms whereas others implicate different mechanisms for each domain. In this project, a research team from the University of Texas El Paso and New Mexico State University aims to distinguish which tectonic forces drive extension in the two provinces where they merge in southern New Mexico. To do so, they will determine the uplift ages for many of the ranges in the region in order to determine if the Basin and Range province and the Rio Grande rift experience the same extension history. Desired societal outcomes will be achieved through the full participation of students and researchers of Hispanic heritage in the research project.The Rio Grande rift is one of the world?s best exposed and most thoroughly studied continental rifts, yet there still remains considerable uncertainty and debate on the driving forces that produced it and why it formed when and where it did. Many researchers view the Rio Grande rift as the easternmost segment of the adjacent Basin and Range province, but others view it as a separate structural entity. Despite the observation that the southern Rio Grande rift physiographically resembles the adjacent Basin and Range, it can be distinguished by higher heat flow, thinner crust, deeper basins, and an abundance of Quaternary normal faults. These observations lead to uncertainty as to whether these two structural domains evolved contemporaneously or not, as well as different interpretations of the underlying causes(s) driving crustal extension in the southwest U.S. The objective of this project is to constrain times of extension in the region where these two structural domains merge to test models for formation of the Rio Grande rift. Specifically, the project aims to be addressed are: (1) the timing of the main phase of extension in the Basin and Range Province of southeastern Arizona/southwestern New Mexico and the southern Rio Grande rift of southern New Mexico; (2) the difference in style/timing of extension between the Rio Grande rift and Basin and Range; and (3) the main driver of extension in the southern Rio Grande rift. To these ends, the research team will use apatite (U-Th)/He, apatite fission-track, and zircon (U-Th)/He thermochronologic methods on samples collected from thirteen individual fault block uplifts in the Rio Grande rift-Basin and Range transition of eastern Arizona, southern New Mexico, and western Texas. These results will fill a data gap between the Basin and Range and the northern Rio Grande rift. For each sample, U and Th zoning profiles will be obtained for apatite and zircon, and inverse models will be produced that incorporate all new thermochronologic data, zoning information, as well as existing geologic constraints. These data will be able to place very tight constraints on each samples' time-temperature history. The resulting models will delineate times of rapid exhumation from times of tectonic quiescence at each location, which will be the principle method for testing between models for extension.

美国西部的盆地山脉省和格兰德河裂谷是两个构造域，岩石圈在过去 2500 万年里慢慢地分开。这种伸展分布在盆地和山脉的广大地区，并且更集中在格兰德河裂谷中从新墨西哥州南部到科罗拉多州北部的狭窄区域，该区域在许多方面与世界上其他重要的裂谷带相似。人们提出了多种构造模型来解释这两个领域的伸展。一些模型将其发展归因于相同的机制，而另一些模型则暗示每个领域的不同机制。在这个项目中，来自德克萨斯大学埃尔帕索分校和新墨西哥州立大学的一个研究小组旨在区分哪些构造力推动了新墨西哥州南部合并的两个省份的扩张。为此，他们将确定该地区许多山脉的隆起年龄，以确定盆地山脉省和里奥格兰德裂谷是否经历过相同的扩张历史。通过西班牙裔学生和研究人员对研究项目的充分参与，将实现预期的社会成果。里奥格兰德裂谷是世界上暴露最充分、研究最彻底的大陆裂谷之一，但关于其产生的驱动力以及其形成时间和地点的原因，仍然存在相当大的不确定性和争论。许多研究人员将格兰德河裂谷视为邻近盆地和山脉省的最东段，但其他人则将其视为一个独立的结构实体。尽管观察发现，格兰德河裂谷南部在地貌上与邻近的盆地和山脉相似，但它的特点是热流较高、地壳较薄、盆地更深、以及丰富的第四纪正断层。这些观察结果导致了关于这两个结构域是否同时演化的不确定性，以及对驱动美国西南部地壳扩张的根本原因的不同解释。该项目的目的是限制这两个结构域合并的区域的扩张时间，以测试格兰德河裂谷形成的模型。具体而言，该项目要解决的问题是：（1）亚利桑那州东南部/新墨西哥州西南部盆地山脉省和新墨西哥州南部里奥格兰德裂谷南部主要阶段延伸的时间安排； (2)里奥格兰德裂谷与盆岭之间的伸展方式/时间差异； (3) 里奥格兰德裂谷南部扩张的主要驱动力。为此，研究小组将使用磷灰石 (U-Th)/He、磷灰石裂变径迹和锆石 (U-Th)/He 热年代学方法，对从亚利桑那州东部、新墨西哥州南部和德克萨斯州西部的里奥格兰德裂谷盆地和山脉过渡区的 13 个独立断块隆起采集的样本进行分析。这些结果将填补盆地山脉与里奥格兰德裂谷北部之间的数据空白。对于每个样本，将获得磷灰石和锆石的 U 和 Th 分区剖面，并将生成包含所有新热年代学数据、分区信息以及现有地质约束的反演模型。这些数据将能够对每个样品的时间-温度历史施加非常严格的限制。由此产生的模型将描绘每个位置的构造静止时间和快速折返时间，这将是测试模型之间的伸展的主要方法。