An Estimate of Heat Flow on the Meteor Rise, Site 704

Abstract

Heat-flow determinations require more than one reliable temperature measurement to obtain an estimate of the temperature gradient and, subsequently, the heat flow. Two temperature readings were taken on ODP Leg 114, both in Hole 704B. One of these readings appears to be reliable, but the other may not be valid. We can try to estimate a temperature gradient on the basis of these two points alone, or we may try to estimate the temperature from the induction log resistivity and the laboratory-measured porosity using a modified Archie's law. Using the two temperature measurements, the temperature gradient is 20 ± 2 mK/m and the computed heat flow is 32 ± 6 mW/m 2 . Alternatively, we can use the one reliable temperature measurement to calibrate the temperature derived from the resistivity and porosity. The temperature and heat flow computed for individual units can be different and depend on the shape factor used in the modified Archie's law. The temperature gradient obtained from the resistivity and porosity is 38 ± 4 mK/m and the average heat flow is 60 ± 13 mW/m 2 , which is consistent with the age of the Meteor Rise. These values are also consistent with the heat flow that is computed when we assume a simple linear temperature gradient from the seafloor through the sediment section.