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Metamorphism associated with lithospheric extension

  • Roger Mason
Chapter

Abstract

The Earth’s oceanic crust has formed by extension from oceanic ridges. In oceans where subduction zones are not yet extensively developed, such as the Atlantic, these ridges are close to the centre of the ocean basin. In oceans such as the Pacific, which are surrounded by active subduction zones, the ridges are not central. Oceanic crust and the upper mantle, together constituting the oceanic lithosphere, are constructed by extension at the ridges. Geophysical studies indicate that oceanic ridge extension creates new crust symmetrically on either side of relatively narrow extensional rift regions, often marked by topographical graben structures. The oceanic crust so formed is mostly composed of basic igneous rocks (basalts when erupted on the ocean floor, dolerites and gabbros when intruded into previously constructed oceanic crust), and the oceanic mantle of ultrabasic rocks.

Keywords

Oceanic Crust Ocean Floor Oceanic Ridge White Mica LITHOSPHERIC Extension 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© R. Mason 1991

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  • Roger Mason

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