The Socorro Magma Body: Surface Uplift History and Crustal Dynamics

索科罗岩浆体：地表隆起历史和地壳动力学

• 批准号: 1348076
• 负责人: Gary Axen
• 金额: $ 30.34万
• 依托单位: New Mexico Institute of Mining and Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1348076&HistoricalAwards=false
• 关键词: Socorro; Magma; Body; Surface; Uplift

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.

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。它是一个板状体，面积约3，400平方公里，厚度不到150 m，位于新墨西哥州索科罗下方约19公里深处，位于格兰德河裂谷内。在新墨西哥州，该地区的上地壳地震活动率最高，据推测，这是由索科罗岩浆体上方的变形和上升的含水流体引发的。水准测量和干涉合成孔径雷达研究表明，岩浆体造成的地表抬升速率高达2.5至3毫米/年。通过对该项目中的地表特征进行测绘和测年，来自新墨西哥州矿业与技术研究所的研究人员可以限制岩浆体的年龄和隆升历史。当与数值模拟相结合时，结果将有助于理解地壳生长，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，提高公众科学素养和公众对科学技术的参与，通过更好地了解新墨西哥州的地震和火山灾害，改善社会中个人的福祉，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。索科罗岩浆体为研究中地壳岩浆体提供了难得的机会（大多数其他的浅得多），将中地壳过程与地表变形联系起来，研究深岩床对伸展过程的影响，以及研究裂陷地壳中的岩浆地壳生长。该项目的首要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。该项目确定：（1）岩浆体的历史是否超过1 ka;（2）膨胀的幕式性和年龄;（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）隆升源的几何形状。具体来说，研究小组绘制了沿着格兰德河及其支流形成的梯田的地图，并将其作为应变标志。索科罗岩浆体相关的和第四纪断层相关的地表变形是根据预期的倾斜方向，倾斜长度和倾斜幅度的差异来区分的。阶地相关性包括河流以上的相对高度，阶地踏面、沉积物和河床的特征，以及土壤分析。关键的，保存完好的阶地使用36 Cl深度剖面法。地球动力学模拟测试了活动隆升源（膨胀、热膨胀、补给源、结晶岩浆收缩等）的几何形状和动力学。通过与干涉合成孔径雷达和GPS测量结果的对比，指导了对阶地分析揭示的索科罗岩浆体地表变形的解释。