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Geological Sciences

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The North Qaidam and South Altyn terranes extend approximately 1000 km across the northern Tibetan Plateau, and five localities preserve evidence of Early Paleozoic high-pressure (HP) or ultrahigh-pressure (UHP) metamorphism, including the presence of coesite, coesite pseudomorphs, and diamond. A review of the geology, petrology, and geochronology collected over the past 10 years since these localities were discovered supports a correlation of the North Qaidam and South Altyn terranes, offset 350-400 km across the Altyn Tagh fault. Geochronology interpreted to reflect eclogite-facies metamorphism yields ages between 500 and 420 Ma; detailed geochronology from one locality supports a protracted (tens of m.y.) history of HP/UHP metamorphism. Rock associations and geochronology support a passive-margin origin for the protolith of the HP/UHP rocks, which received sediments from a Proterozoic-Late Archean source, and was intruded by Neoproterozoic granites derived from crustal melting.

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International Geology Review