| 英文摘要: | 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. |