Collaborative Research: The Jemez Tomography Experiment (JTEX)

杰梅兹断层成像实验（JTEX）是一项跨学科合作研究项目，涉及来自六所主要大学、美国能源部支持的洛斯阿拉莫斯国家实验室和美国地质调查局的科学家。耶梅斯山火山田是晚新生代一个重要的硅质火山体系。也许它最著名的特征是Valles火山口和相关的1.1至1.6 Ma爆炸性火山产物，包括Bandelier凝灰岩。与JMVF和其他近期硅质火山系统相关的基本问题是：1。在JMVF火山活动期间，地壳卷入和伴随的地壳变化的性质和程度是什么？在山谷破火山口和耶梅斯山脉下的地壳中是否存在地壳侵入、岩体或下覆区？2. 在过去的15 Ma中，JMVF是如何演变的，最终以Bandelier流纹岩火成岩的喷发和破火山口的崩塌而告终？硅质岩浆生成的岩石学模型表明，在主要硅质火山中心下方的地壳中存在大量的基性侵入物（大约是喷发物质体积的十倍）。我们能否对这些侵入体进行地球物理成像，并解释它们与观测到的火山地质的关系？为了解决这些问题和其他与JMVF有关的问题，以及与大陆岩浆作用有关的问题，主要研究人员将对JMVF进行深入的地球物理研究，分析收集到的数据，并结合岩石学和地球化学资料解释结果。新的地球物理数据将包括：地震折射/反射、远震延迟时间和波形、重力、磁场和大地电磁（MT）数据。该程序旨在提供JMVF下岩浆变化的c型铁锈的三维图像。爆炸地震和远震数据的层析反演，结合势场、MT和地质数据的解释，将产生目前可用的最高分辨率的地壳尺度特征三维研究。

The Jemez Tomography Experiment (JTEX) is a cooperative and interdisciplinary research program involving scientist from six major Universities, the Los Alamos National Laboratory with support from the DOE, and the U.S. Geological Survey. The Jemez Mountains volcanic field (JMVF) is a major Late Cenozoic silicic volcanic system. Perhaps its best-known feature is the Valles Caldera and associated 1.1 to 1.6 Ma explosive volcanic products including the Bandelier Tuff. The fundamental questions that relate to the JMVF and other recent silicic volcanic systems and which are addressed in the project are: 1. What is the nature and extent of crustal involvement and accompanying modifications of the crust during the volcanic activity in the JMVF? Are crustal intrusions, pluton, or underplated regions present in the crust beneath the Valles Caldera and Jemez Mountains? 2. How has the JMVF evolved through the last 15 Ma, culminating in eruption of the Bandelier rhyolite ignimbrite and caldera collapse? Petrologic models of silicic magma generation suggest that large volumes of mafic intrusions (on the order of ten times the volume of erupted material) are present in the crust beneath major silicic volcanic centers. Can we image these intrusions geophysically and interpret their relationships to the observed volcanic geology? In order to address these and other questions related specifically to the JMVF and generally to continental magmatism, the principal investigators will conduct intensive geophysical studies of the JMVF, analyze the data collected and interpret the results in concert with petrologic and geochemical information. The new geophysical data will include: seismic refraction/reflection, teleseismic delay time and waveform, gravity, magnetic, and magnetotelluric (MT) data. The program is designed to provide a three-dimensional image of the magmatically modified c rust beneath the JMVF. Tomographic inversion of the explosion seismic and teleseismic data and combined interpretation with the potential field, MT and geologic data will produce the most high resolution 3-D study of crustal scale features that is currently available.