GAS EMISSION IN FAILURES OF YUNNAN MARBLE
Yang Xinhua Wang Fujiang Yao Baoshu Zhang Bochong (Seismogeologkal Brigade, State Seismologicd Bureau)
A triaxial compression test has been carried out on the Yunnan marble. The result shows that in samples the failures occurred in different forms at various confining pressures. When the confining pressure was lower than 392 bars, the samples failed in shear and a smell of H2S could be taken at the surface of the fracture. When the pressure was between 589-1177 bars, in samples occurred ductile failures and more than 10 c.c. gas was emitted from each of the samples. When the confining pressure was 1350 bars, a cataclastic flow was produced and about 7 c.c. gas emitted from the sample. The main content of the emitted gas was CO2 and there were also a certain amount of other gases, such as H2S and CH4 etc.The authors suggest that the emitted CO2 was a decomposition product of the CaCO3 at the surface of the shear microfractures under high temperatures. The significance of the gas emission is also discussed for the research of earthquake premonitory phenomena.