Decompression P-T path of coesite eclogite to granulite from Weihai, eastern China

Granulitized coesite-bearing eclogite from Weihai, northeastern part of the Shandong peninsula, eastern China was studied in detail to reveal the modification of mineral chemistry during decompression metamorphism. Considerable modification of chemical composition is recorded in clinopyroxene that occurs both as inclusions in garnet and as a matrix mineral. Careful examination of chemical variation with the change in microstructure made it possible to estimate the equilibrium composition of minerals at the coesite eclogite and garnet granulite stages. We were able to define three reference points on the P-T path, namely, coesite eclogite (3 GPa, 660 +/- 40 degrees C), granulite (1 GPa, 700 +/- 30 degrees C) and amphibolite (0.9 Cpa, 600 +/- 20 degrees C). The path thus obtained is similar to those obtained by previous workers and supports nearly isothermal decompression of coesite eclogite. (C) 2000 Elsevier Science B.V. All rights reserved.