A coesite inclusion in dolomite in Dabie Shan, China: Petrological and rheological significance
Schertl, Hans-Peter; Okay, Aral I.
European Journal of Mineralogy Volume 6 Number 6 (1994), p. 995 - 1000
published: Nov 30, 1994
manuscript accepted: Jul 8, 1994
manuscript received: Apr 5, 1994
ArtNo. ESP147050606018, Price: 29.00 €
Abstract Coesite partially inverted to quartz occurs as an inclusion within dolomite in a calc-silicate rock in Dabie Shan, China. The calc-silicate rock consists mainly of dolomite, calcite, quartz, and phengite that is partially replaced by phlogopite, plagioclase, and secondary phengite. There are also minor amounts of epidote, coesite, rutile, titanite, apatite, zircon, opaque, and calcic amphibole + oligoclase (± diopside)-symplectite after pyroxene. The calc-silicate intercalated with marble forms an over 8-m-thick band in felsic gneiss. It comprises calcium-rich eclogite blocks with coesite and diamond inclusions in both, pyroxene and garnet. Radial cracks are absent in dolomite surrounding the coesite/quartz inclusion suggesting that the volume increase 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 over 100 km, and that even a carbonate mineral like dolomite is able to preserve coesite during the process of eduction.