THE EFFECTS OF WATER FLUID AT TEMPERATURE S UP TO 850-DEGREES-C AND PRESSURE OF 300-MPA ON COMPRESSIONAL WAVE VELOCITY, POROSITY AND PERMEABILITY OF AMPHIBOLITE

The compressional wave velocities were measured in amphibolite under g as and water fluid pressure of 300 PMa and temperatures up to 850 degr ees C. Fluid and confining pressures were equal during the experiments . The data obtained under water pressure differ from that of gas press ure by the reversion of upsilon(p) temperature trend. For the initial and quenched amphibolite samples porosity, permeability and pore size distribution were measured and microstructure studies were carried out . It was found that the changes in elastic properties of rock with tem perature rise are determined by the changes of its porosity. There are two types of processes responsible for the transformation of pore str ucture: phase transitions within the narrow temperature range (high-lo w quartz transition at T similar to 650 degrees C, P = 300 PMa, partia l melting of the amphibolite at T = 700-760 degrees C, P = 300 MPa) an d processes which take place within the complete temperature range: ge neration of microfissures and local mass transfer.