Hot and Dry Deep Crustal Xenoliths from Tibet

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Science  31 Mar 2000:
Vol. 287, Issue 5462, pp. 2463-2466
DOI: 10.1126/science.287.5462.2463

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Anhydrous metasedimentary and mafic xenoliths entrained in 3-million-year-old shoshonitic lavas of the central Tibetan Plateau record a thermal gradient reaching about 800° to 1000°C at a depth of 30 to 50 kilometers; just before extraction, these same xenoliths were heated as much as 200°C. Although these rocks show that the central Tibetan crust is hot enough to cause even dehydration melting of mica, the absence of hydrous minerals, and the match of our calculated P-wave speeds and Poisson's ratios with seismological observations, argue against the presence of widespread crustal melting.

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