Thermal effects of gabbro accretion from a deeper second melt lens at the fast spreading East Pacific Rise

Abstract

Motivated by recent observations, a ridge model has been developed which includes both a shallow melt lens and a second deeper melt lens above the Moho to assess the thermal effect of the gabbro accretion from the lower melt lens at the fast spreading East Pacific Rise. Modeling results argue for a limited role of the lower melt lens in constructing the layer 3 gabbros. If significant (>10%) amount of the layer 3 gabbros is emplaced near the Moho, then the liberated latent heat during crystallization would generate a large "molten" section of the lower crust due to the inability of cold seawater to penetrate into this hot/ductile region. A large molten section of the lower crust is not consistent with recent seismic tomographic results of the East Pacific Rise. Thus it is likely that the amount of the gabbro being emplaced from the lower melt lens at the EPR is significantly less than that suggested by Oman ophiolite studies, such a lower melt lens is short-lived, or a large portion of the sill intrusions observed at Oman was emplaced at a few kilometers off axis (>3-4 km). Copyright 2001 by the American Geophysical Union.