Heat flow in the western equatorial Pacific Ocean

Abstract

One hundred and eleven previously unpublished heat flow measurements are reported from the western equatorial Pacific Ocean. The mean of 40 values (48 ± 2 mWm−2) obtained between the Line Islands and the Marshall, Gilbert, and Ellice island groups is comparable to the mean obtained for other deep-ocean basins. An anomaly appears to exist in the geological-geophysical relations across the Solomon Islands arc; i.e., the heat flow distribution (low to the northeast and high to the southwest) and the island geology suggest a trench and subduction zone on the Pacific Ocean (northeast) side of the arc, but seismic, bathymetric, and crustal thickness data show that a trench and subduction zone exist on the Coral Sea (southwest) side. This contradiction may be reconciled if it is assumed that at some time in the past the subduction of a downgoing plate, at that time on the northeast side of the arc, was stopped by the thick (>35 km) crust of the Ontong Java plateau, which collided with the arc. Continued crustal consumption being necessary because of plate tectonics, a new subduction zone then formed on the southwest side of the arc. The observed heat flow distribution can be viewed as a relict feature of a preexisting island arc-trench configuration. In most of the trenches in the western equatorial Pacific (New Britain, north Solomon, north New Hebrides, and Marianas) heat flow is low. However, in the Palau trench it is abnormally high. Four high values obtained on the northern margin (including the Palau trench) of the west Caroline basin agree well with high values previously reported in the southern part of the basin.