On low-grade metamorphic rock within Dabie-Sulu ultrahigh pressure metamorphic belt.
大别—苏鲁超高压变质带内部的浅变质岩

There are sparotic occurrences of low grade metamorphic rocks as tectonic relict flakes within the Dabie Sulu ultrahigh pressure (UHP) orogen. They are mainly composed of metaclastics, phyllites and marbles. They having, suffered from dynamic metamorphism at low greenschist facies and fold and fault deformation, are in tectonic contacts with the surrounding UHP rocks. Micro paleontologic fossils from the low grade metamorphic rocks suggest that their sedimentary protoliths were deposited in a shallow marine environment at Sinian in the northern margin of Yangze plate. Isotopic datings indicate that their igneous protoliths are of Late Proterozoic ages and experienced tectonic events at Caledonian and Indosinian like the surrounding UHP eclogites and gneisses. Oxygen isotope analysis shows that the low grade metamorphic rocks within the Dabie orogen are depleted in 18 O like the surrounding UHP rocks and thus their protoliths underwent hydrothermal alteration by ancient meteoric water at high temperatures. It appears that the low grade metamorphic rocks were originally the Sinian sedimentary rocks and enclosed volcaniclastic rocks in the northern margin of the Yangtze plate, and have the geological occurrence and formation mechanism similar to accretionary wedge that was scraped from the subducting Yangtze plate and accumulated in the subduction zone. Therefore, they may be a part of the tectonic accretionary wedge of continental plate subduction.