Constraining the crustal composition of the continental U.S. using seismic observables.

The composition of the crust is one of the most uncertain and controversial components of continental estimates due to (1) limited direct access and (2) inconsistent indirect assessments. Here we show that by combining high-resolution shear velocity (Vs) models with newly measured with newly measured ratio of compressional wave velocity (Vp) and Vs, or Vp/Vs ratio, for the crystalline crust, a 3-D composition (SiO2 wt%) model of the continental crust can be derived with uncertainty estimates. Comparing the model with local xenolith data shows consistency at mid and lower crustal depths. The spatial patterns in bulk SiO2 content correlate with major geological provinces, including the footprints of Cenozoic and Mesozoic mafic volcanism in the western U.S., and offer new insight into the composition and evolution of the continental U.S. [ABSTRACT FROM AUTHOR]