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 modi fication of mineral chemistry during decompression metamorphism. Considerab le modification of chemical composition is recorded in clinopyroxene that o ccurs both as inclusions in garnet and as a matrix mineral. Careful examina tion of chemical variation with the change in microstructure made it possib le to estimate the equilibrium composition of minerals at the coesite eclog ite and garnet granulite stages. We were able to define three reference poi nts 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 prev ious workers and supports nearly isothermal decompression of coesite eclogi te. (C) 2000 Elsevier Science B.V. All rights reserved.