Hot and dry deep crustal xenoliths from Tibet

Anhydrous metasedimentary and mafic xenoliths entrained in 3-million-year-o ld shoshonitic Lavas of the central Tibetan Plateau record a thermal gradie nt reaching about 800 degrees to 1000 degrees C at a depth of 30 to 50 kilo meters; just before extraction, these same xenoliths were heated as much as 200 degrees C, Although these rocks show that the central Tibetan crust is hot enough to cause even dehydration melting of mica, the absence of hydro us minerals, and the match of our calculated P-wave speeds and Poisson's ra tios with seismological observations, argue against the presence of widespr ead crustal melting.