Physics
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.v33d..03z&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #V33D-03
Physics
3621 Mantle Processes (1038), 7270 Tomography (6982, 8180), 8137 Hotspots, Large Igneous Provinces, And Flood Basalt Volcanism, 8177 Tectonics And Climatic Interactions, 8415 Intra-Plate Processes (1033, 3615)
Scientific paper
High-resolution regional and global tomographic studies are made for imaging the active mantle upwellings and understanding their origins (Zhao, 2001, 2004; Zhao et al., 2004, 2006). Global tomography shows plume-like slow anomalies clearly under the major hotspot regions in most parts of the mantle, in particular, under Hawaii, Iceland, Kerguelen, South Pacific and Africa (Zhao, 2001, 2004). The slow anomalies under South Pacific and Africa have lateral extensions of over 1000 km and exist in the entire mantle, representing two superplumes. The Pacific superplume has a larger spatial extent and stronger slow anomalies than that of the Africa superplume. The Hawaiian plume is not part of the Pacific superplume. The slow anomalies under hotspots usually do not show a straight pillar shape, but exhibit winding images, suggesting that plumes are not fixed in the mantle but can be deflected by the mantle flow. Most of the slab materials are stagnant in the mantle transition zone before finally collapsing down to the CMB as a result of large gravitational instability from phase transitions. The active intraplate volcanoes in East Asia continent (such as the Changbai and Wudalianchi volcanoes) are not plume-related hotspots, but are a kind of back-arc volcanoes whose formation was closely related to the deep subduction of the Pacific slab and its stagnancy in the mantle transition zone. The active Tengchong volcano in Southwest China is related to the subduction of the Burma microplate. A clear low- velocity anomaly exists down to 600 km depth under Lake Baikal, which may represent the Baikal plume causing the Baikal rift zone (Zhao et al., 2006). Zhao, D. (2001) Seismic structure and origin of hotspots and mantle plumes. Earth Planet. Sci. Lett. 192, 251- 265. Zhao, D. (2004) Global tomographic images of mantle plumes and subducting slabs: insight into deep Earth dynamics. Phys. Earth Planet. Inter. 146, 3-34. Zhao, D. et al. (2006) Deep structure and origin of the Baikal rift zone. Earth Planet. Sci. Lett. 243, 681-691.
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