Subduction Zones, Magmatism, and the Breakup of Pangea

Abstract

Paleoreconstructions of the lithospheric plates with major subduction zones indicated are reviewed for every 40 million years from 200 Ma to Present. Relative major plate motions are based on marine magnetic anomalies, seafloor lineations including fracture zones and transform faults, and paleomagnetic data. Pangea as an entity existed for only about 100 million years, until seafloor spreading in the central North Atlantic began at ~ 175 Ma and it separated into Gondwana and Laurentia. Although Gondwana was ringed on its southern margin by continentward subduction zones, eventual breakup mostly occurred thousands of kilometers from the subduction zones. Major plate reorganizations are often associated in time with continental flood basalts, although it is unclear whether the flood basalts represent a cause or are an effect of major plate breakup. Around 130 Ma, there were three significant rifting events: the South Atlantic opened between South America and Africa, India rifted from Antarctica, and the Canada Basin in the Arctic opened between Arctic Canada and Arctic Alaska. At ~ 120 Ma, the nearly continuous subduction zone that had existed along the southern margin of Pangea since at least 200 Ma began to break apart with the subduction of the Pacific-Aluk spreading center along eastern Australia and northern New Zealand. By 40 Ma, the major subduction zones seem to have migrated from high latitude regions to lower latitudes.