Emplacement of Large Crustal Sills and The Mechanics of Magmatic Underplating

California Institute Of Technology, Pasadena CA

Investigators

Abstract

Simons 9980664 Intrusion of large sill-like magma bodies plays a major role in the accretion of the Earth's crust and ultimately in the chemical differentiation of the lithosphere. However, the particular mechanisms that control initiation, emplacement, and termination of horizontal magma sheets are poorly understood. Major outstanding problems include the relative importance of ambient stresses and rock strength anisotropy in governing sill initiation and growth, the relationships between sills, feeder dikes, and magma source regions, the character and extent of inelastic deformation accompanying sill emplacement, and intrusion-induced seismicity. This project aims to develop a detailed quantitative understanding of individual underplating events by solving boundary value problems of solid mechanics that explicitly include realistic variations in the host rock properties, effects of the free surface, and inelastic deformation of the host based on reasonable failure laws. The investigators will gain further insight into the dynamics of sill-like intrusions by performing physical analog experiments in collaboration with the Department of Experimental Tectonophysics of Kiev Institute of Geophysics (Kiev, Ukraine). This work will be directly relevant to interpretations of seismicity in the regions of the inferred contemporaneous sill-like magma bodies. By using satellite radar interferometry (InSAR), surface deformation will be measured in the area of Socorro, New Mexico, where anomalous mid-crustal reflector and geodetic uplift have been interpreted as indicating the presence of magma at depth. The investigators will invert the observed deformation to constrain the geometry of the inferred magma body and the dynamics of magma supply.