A coesite inclusion in dolomite in Dabie Shan, China; petrological and rheological significance
A coesite inclusion in dolomite in Dabie Shan, China; petrological and rheological significance
European Journal of Mineralogy (December 1994) 6 (6): 995-1000
Coesite partially inverted to quartz occurs as an inclusion in dolomite in a calc-silicate rock in Dabie Shan, central China. The calc-silicate rock consists mainly of dolomite, calcite, quartz and phengite that is partially replaced by phlogopite, plagioclase and secondary phengite. This calc-silicate rock is intercalated with marble forming a band >> 8 m thick in felsic gneiss; it contains Ca-rich eclogite blocks with coesite and diamond inclusions in both pyroxene and garnet. Radial cracks are absent surrounding the coesite/quartz inclusion, suggesting that the increase in volume associated with the coesite-quartz inversion was largely accommodated by movement along the cleavage planes. The presence of coesite within dolomite in calc-silicate rocks confirms that sedimentary rocks deposited on continental crust can be subducted to depths of >> 100 km, and that even a carbonate mineral like dolomite is able to preserve coesite during the process of eduction.