Geo-Tectonics, Geology, and Geo-Resources of the Southwest Pacific

Abstract

The Africa-sized SW Pacific region contains the greatest diversity of ocean tectonic features in the world. In this region, dominated by the Pacific and Australian mega-plates, in addition to several micro-plates, a large number of island arcs, ocean trenches, seamount chains, young ocean basins, ocean plateaux, and active volcanoes are situated. Curvilinear island arc systems, and related trenches, are dominant structures, with examples such as the Solomon Islands, Vanuatu, and Tonga arc systems. Island arcs are the sites of earthquakes and active arc-volcanoes. Some arcs, such as Fiji, now lie in positions at some distance from the trenches and subduction processes which once produced them. Other arcs, such as Solomon Islands, are also sites of collision with a large ocean plateau. Thick, basaltic, continental-sized ocean plateaux, formed from large mantle plumes, manifest as the great structures of Ontong Java and Manihiki. Linear trails of seamounts and islands, such as the Louisville and Samoan seamount/island chains form from lower-volume mantle hotspots, as the large Pacific plates pass over active, stationary, mantle plumes. Rifted and submerged remnants of more ancient continents form linear topographic aseismic ridges. Some of the deepest and largest magnitude earthquakes are located at trenches such as the Vanuatu and Tonga Trenches. Vanuatu, Solomon Islands, and Tonga, contain a number of subaerial and submarine arc-volcanoes, whilst Cook Islands and Samoa contain plume-related ocean basalt shield volcanoes. The region is mineralized, both on-land and in the deep ocean, which hosts abundant seabed minerals. The region has significant potential for geothermal energy.