Chinese Continental Scientific Drilling Program

Drilling Operations in the Dabie-Sulu UHPM Belt, East China

One of the most exciting geologic discoveries in the last 20 years is the finding of the presence of a major ultrahigh pressure (UHP) metamorphic belt in the Dabie-Sulu region of eastern China. In this belt, high-grade continental crustal rocks contain both diamond and coesite, clear evidence of crustal subduction to depths >150 km. This belt formed by collision between the North China and Yangtze blocks in the Mesozoic between about 210 and 220 Ma. Recent work has identified an older, parallel belt on the north side of the Dabie-Qinling Mountains dated as Ordovician (~500 - 440 Ma). A site in the Sulu segment of the belt where ultramafic rock and eclogite are hosted in coesite-bearing gneiss was selected for deep drilling. The seismic profile through the drill site is interpreted in terms of five stacked slices separated by northeast striking, gently southeast dipping ductile shear zones.

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