Crustal structure across the Costa Rican Volcanic Arc

Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 14 (2013): 1087–1103, doi:10.1002/ggge.20079.Island arcs are proposed to be essential building blocks for the crustal growth of continents; however, island arcs and continents are fundamentally different in bulk composition: mafic and felsic, respectively. The substrate upon which arcs are built (oceanic crust versus large igneous province) may have a strong influence on crustal genesis. We present results from an across-arc wide-angle seismic survey of the Costa Rican volcanic front which test the hypothesis that juvenile continental crust is actively forming at this location. Travel-time tomography constrains velocities in the upper arc to a depth of ~15 km where average velocities are