Mineral Component of "Taishunshi" and Its Genetic Significance

The "Taishunshi" is a kind of pyrophyllite-type carving stone from Guihu town, Taishun county, Hangzhou, Zhejiang Province. The "Taishunshi" as the fifth largest carving stone has occupied a certain market share. Methods including 10× magnifying, optical microscope, X-ray diffraction (XRD), and laser Ramam spectroscopy (LRM) were employed to determine the mineral components of the "Taishunshi" samples and analyze its genetic significance. The results show that the main mineral component of samples is pyrophyllite (1Tc type). Minor quartz, diaspore, kaolinite, illite, hematite and corundum are also detected. Petrographic observation shows that pyrophyllite in the "Taishunshi" can be divided into two types which are hydrothermal metasomatic type and hydrothermal filling type. Pyrophyllite that is hydrothermal metasomatic type alters feldspar and diaspore in the wall rock forming metasomatic relict texture and metasomatic pseudomorphic texture. Pyrophyllite which is hydrothermal filling type fills the cracks in the later mineralizing process. Petrographic observation results provides direct evidence to the formation of the pyrophyllite. Diaspore and corundum existing as paragenetic minerals during the mineralizing process of pyrophyllite show as stone nails and blue nails in the "Taishunshi", respectively. The different mineral combination characteristics of the "Taishunshi" samples directly or indirectly record the metasomatism between hydrothermal solution and rhyolitic crystal tuff such as pyrophyllitization, diasporization, etc. The hematite in the red "Taishunshi" may indicate the change toward oxidization environment in the later mineralizing process. According to the results of experimental petrography, the mineral combination characteristics of the samples in this study indicate that "Taishunshi" should be mainly formed in an environment at a temperature ranging from 260-394±10 ℃.