Die obere Stabilitätsgrenze von Tremolit bei der Metamorphose von kieseligen Karbonaten

During the metamorphism of siliceous carbonates, decomposition of tremolite yields diopside, enstatite, quartz and H₂O according to the following reaction: 1 tremolite 2 diopside + 3 enstatite + 1 quartz + 1 H₂O.For the application to natural processes, it is of special interest to evaluate the equilibrium temperature of this reaction, as a function of the CO₂-content of the H₂O-CO₂ fluid phase for several total pressures. These values were calculated for the total pressures of 1000 and 2000 bars, usingBoyd's experimentally determined univariant equilibrium data Fig. 1 (Boyd, 1954 and 1959)]. Curves (a) and (b) of Fig. 3 give the results in a temperature-X _{CO 2}-diagram.The decomposition curves of tremolite intersect the equilibrium curves of other reactions which also take place during metamorphism of siliceous carbonates. If the total pressure can be estimated, these points of intersection together with the appropriate field observations will give information on the temperature and composition of the fluid phase during metamorphism.