Crustal and mantle relationships as a function of geologic age and heat Flow from the east Pacific rise out into the Pacific basin

Abstract

It is found that the mean velocity of the crystalline rock crust, its thickness and the velocity of the upper mantle vary significantly and are inter-related in varying modes with geologic age and heat flow. Except for the zone of low heat flow on the flanks of the rise crest where the crust thins and mantle and mean crustal velocity appear to bear an inverse relations to each other, the thickness of the crust, the mean velocity of the crust and mantle velocity all increase as heat flow decreases with increase in depth of water, geologic age and distance from the rise crest out to approximately 63 MY. At this point, there is a significant decrease in mean crustal velocity, mantle velocity and crustal thickness attended by a small positive perturbation in heat flow. For ages greater than 76 MY out to 120 MY, the thickness of the crust again increases with age and distance from the rise crest and increase in depth of water. This increase in crustal thickness appears to be inversely related to the change in mantle velocity with little change in mean crustal velocity, and heat flow on an over-all basis decreases over this age period. For ages greater than 120 MY, there is no significant change in crustal thickness or depth of water, although the available data suggest that the velocity of the mantle increases with an attendant slight increase in mean crustal velocity and heat flow.