Australia: The Land Where Time Began

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Superplumes - Multiscale Seismic Tomography of Mantle Plumes and Subducting Slabs

In this paper Zhao reviews local, regional and global tomographic studies of mantle plumes and slabs that are subducting. Clear images of subducting slabs and magma chambers in the upper mantle wedge beneath active arc volcanoes have been gained by the use of applications of local and teleseismic tomography methods that are well-established.  These results indicate that geodynamic systems associated with arc magmatism and back-arc spreading are related to deep processes, such as mantle wedge convective circulation and dehydration occurring in slabs that are subducting. It is also shown by evidence that the generation of various types of earthquakes in subduction zones may be contributed to by arc magma and dehydration of slabs. Most of the slab materials are stagnant in the transition zone of the mantle before they finally collapse down to the core-mantle boundary as a result of large gravitational instability that is associated with phase transitions. 3-D crust and structure of the upper mantle has been determined for only a few hotspots such as Iceland, Yellowstone and Eifel which are covered by seismic networks, but most hotspots are located in continental and oceanic regions that are only poorly instrumented. In the upper mantle under these hotspots plume-like velocity anomalies have been revealed. For deep mantle plumes global tomographic studies have only recently begun, and much more study is required to image the conduits of plumes in the lower mantle. According to Zhao a combination of more effective seismic imaging techniques and dense coverage of global seismic networks, especially in the oceans, is needed to gain a thorough understanding of the seismic structure of mantle plumes and subducting slabs.

Sources & Further reading

  1. Dapeng Zhao in Yuen, D.A., Maruyama, S, Karato, Shun-ichiro & Windley, B., (Eds), 2007, Superplumes: Beyond Plate Tectonics, Springer

 

Author: M. H. Monroe
Email: admin@austhrutime.com
Last updated: 14/03/2015
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                                                                                           Author: M.H.Monroe  Email: admin@austhrutime.com     Sources & Further reading