The Socorro Magma Body: Surface Uplift History and Crustal Dynamics

通过地球物理方法确定的索科罗岩浆体是地球上已知最大的岩浆体之一。它是一个面积约3400平方公里，厚度不到150米的板状体，位于新墨西哥州Socorro下方约19公里的深度，位于里约热内卢大裂谷内。该地区是新墨西哥州上地壳地震活动率最高的地区，这种活动可能是由索科罗岩浆体上方的变形和上升的含水流体引发的。平地和InSAR研究表明，岩浆体引起地表隆起的速率高达2.5至3mm /年。在这个项目中，新墨西哥矿业技术研究所的研究人员通过绘制和确定地表特征的年代，可以确定岩浆体的年龄和隆起历史。当与数值模拟相结合时，结果将有助于了解地壳生长，岩浆成因和裂谷过程中的应力变化。该项目通过支持早期职业女性PI充分参与STEM，提高公众科学素养和公众对科学和技术的参与，通过更好地了解新墨西哥州的地震和火山灾害，提高社会个人的福祉，从而促进了预期的社会成果。通过对本科生和研究生的培训以及对早期职业研究人员的支持，发展具有竞争力的STEM劳动力队伍。索科罗岩浆体提供了一个难得的机会来研究中地壳岩浆体（大多数其他岩浆体都较浅），将中地壳过程与地表变形联系起来，研究深部储层对伸展过程的影响，以及研究裂谷地壳中的岩浆地壳生长。该项目的总体目标是通过地貌测绘、地表暴露年代测定和地球动力学建模相结合，确定索科罗岩浆体的长期历史。该工程确定：(1)岩浆体的历史是否超过1 ka左右；(2)通货膨胀的偶然性和时代性；(3)地表变形轨迹随时间的变化；(4)地表断裂与岩浆体的关系；(5)隆升源几何特征。具体来说，研究小组绘制并关联了沿里约热内卢Grande及其支流形成的梯田，作为菌株标记。根据预期倾斜方向、倾斜长度和倾斜幅度的差异，区分了与索科罗岩浆体相关的地表变形和第四纪断层相关的地表变形。阶地对比包括高于溪流的相对高度、阶地踏面特征、沉积物和河床以及土壤分析。使用36Cl深度剖面法确定保存完好的关键梯田的年代。地球动力学建模通过与InSAR和GPS结果对比，验证了活动隆升源（膨胀、热膨胀、补给源、结晶岩浆收缩等）的几何和动力学特征，指导了阶地分析揭示的Socorro岩浆体地表变形的过去几期的解释。

The Socorro magma body, which was identified by geophysical methods, is one of the largest known magma bodies on Earth. It is a tabular body approximately 3,400 square kilometers in area and less than 150 m thick situated at about 19 km depth below Socorro, New Mexico, within the Rio Grande rift. The area has the highest rate of upper crustal seismicity in New Mexico, activity, which presumably is triggered by deformation and ascending hydrous fluids above the Socorro magma body. Leveling and InSAR studies indicate that the magma body causes surface uplift at rates of as much as 2.5 to 3 mm/yr. By mapping and dating surface features in this project, researchers from New Mexico Institute of Mining and Technology can constrain the age and uplift history of the magma body. When coupled with numerical modeling, the results will improve understanding crustal growth, magma genesis, and stress changes during rifting. The project advances desired societal outcomes through full participation of women in STEM through support of an early career female PI, increased public scientific literacy and public engagement with science and technology through outreach efforts, improved well-being of individuals in society through better understanding of earthquake and volcanic hazards in New Mexico, development of a competitive STEM workforce through training of undergraduate and graduate students and support of an early career researcher.The Socorro magma body affords a rare opportunity to study a mid-crustal magma body (most others are much shallower), to relate mid-crustal processes to surface deformation, to study the effects of a deep sill on extensional processes, and to study magmatic crustal growth in rifted crust. The overarching goal of this project is to determine the long-term history of the Socorro magma body through a combination of geomorphoological mapping, surface exposure dating, and geodynamic modeling. The project determines: (1) if the magma body has a history longer than about 1 ka; (2) episodicity and ages of inflation; (3) changes in the locus of surface deformation through time; (4) relationship between surface faulting and the magma body; and (5) geometry of uplift sources. Specifically, the research team maps and correlates terraces formed along the Rio Grande and its tributaries for use as strain markers. Socorro magma body-related and Quaternary fault-related surface deformation is distinguished based upon differences in expected tilt directions, length of tilting, and magnitude of tilting. Terrace correlation involves relative heights above streams, characteristics of terrace treads, deposits and straths, and soil analysis. Key, well-preserved terraces are dated using the 36Cl depth-profile method. Geodynamic modeling tests the geometry and dynamics of the active uplift source (inflation, thermal expansion, feeder source, contraction of crystallized magmas, etc.) by comparison with InSAR and GPS results, and guides interpretation of past episodes of Socorro magma body surface deformation revealed by the terrace analysis.