Collaborative Research: The Jemez Tomography Experiment (JTEX)

Jemez断层扫描实验(JTEX)是一个合作和跨学科的研究计划，由来自六所主要大学、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参与。耶梅兹山脉火山场是晚新生代主要的硅质火山岩系统。也许它最著名的特征是Valles Caldera和相关的1.1到1.6 Ma的爆炸性火山产物，包括班德利耶凝灰岩。与JMVF和其他最近的硅质火山系统有关的基本问题是：1.地壳的性质和范围是什么JMVF火山活动过程中地壳的参与和伴随的改造？Valles Caldera和Jemez山脉之下的地壳中是否存在地壳侵入体、深成岩体或下垫区？2.JMVF在过去15 Ma是如何演化的，最终导致班德利埃流纹岩喷发和火山口坍塌？硅质岩浆生成的岩石学模型表明，在主要硅质火山中心之下的地壳中存在大量的镁铁质侵入体(大约是喷发物质体积的十倍)。我们能想象这些侵入的地球物理现象，并解释它们与观测到的火山地质的关系吗？为了解决这些和其他具体与联合MVF和大陆岩浆活动有关的问题，首席调查员将对JMVF进行深入的地球物理研究，分析收集的数据，并结合岩石学和地球化学信息解释结果。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、磁和大地电磁(MT)数据。该程序旨在提供JMVF下神奇修改的外壳的三维图像。对爆炸地震和远震数据进行层析反演，并结合位场、大地电磁和地质数据进行解释，将产生目前可用的对地壳尺度特征的最高分辨率的三维研究。

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.