Heat flow and plate boundaries in Melanesia

Previous heat flow measurements in Melanesia are considered together with 23 new heat flow values. In the New Hebrides island arc, heat flow is generally normal in front (west) of the arc and high behind (east of) it. These high values are probably due in part to upwelling of asthenospheric material from the Benioff zone and volcanic activity in the interarc basins between the frontal and third arcs. Heat flow distribution behind the arc suggests that the Hazel Holme fracture zone at 15°S is a plate boundary and separates warm, newly generated Fijian lithosphere to the south from cooler, older Pacific lithosphere to the north. High heat flow in the region between Australia and the Melanesian island arcs correlates closely with seismic transmission anomalies in the area and suggests the presence of (1) a fossil island arc associated with the New Caledonia-Loyalty Islands system and (2) active sea floor spreading in the Woodlark basin.