Heat flow on the Pacific-Antarctic Ridge

Twenty-four heat flow measurements are clustered in 5–20 m.y. and 60–80 m.y. old seafloor on the crest and northern flank of the Pacific-Antarctic Ridge. The crestal heat flow stations are characterized by (1) low mean heat flow relative to that predicted by theoretical models, (2) thin sediment cover, and (3) high ratio of standard deviation to mean heat flow, all of which indicate a system dominated by convective heat transfer. The measurements made on older seafloor of the northern flank have (1) mean heat flow equal to the theoretical predictions of conductively-cooling lithospheric plate models, (2) thick sediment cover, and (3) low ratio of standard deviation to mean heat flow. Thus convective loss associated with hydrothermal circulation is not considered to be important in 60–80 m.y. old seafloor on the Pacific-Antarctic Ridge. The pattern of heat flow on this ridge is thus similar to that in the Atlantic, Indian and Pacific Oceans: hydrothermal circulation is dominant on the ridge crest but is suppressed on the flanks, possibly due to a difference in the hydraulic admittance of the sediment between the two regions.