Abstract
A statistical study of about 550 chemical analyses of amphiboles in the hornblende-actinolite series makes it possible to recognize their paragenetic types. The similarities or differences in the above types have been demonstrated by applying Student's t-test and Fischer's test. Typical hornblendes of regional metamorphic rocks are stable within the range 900 to 550°C. Actinolite is characteristic of greenschist facies rocks that formed at temperatures below 550°C. The contents of AlIV and alkalies decrease with decreasing temperatures and the content of AlIV increases with significant increase of pressure. The Al content also increases (due to AlvI) during the transition from clinopyroxene bearing rocks to garnet bearing rocks. Correlations revealed some peculiarities in isomorphism which confirmed the scheme Fe+3AlIV → MgSi, but failed to confirm the replacement of AM AlIv by MgSi. The role of a glaucophane component has been shown. Curves showing the relationship of Ng and f in the various paragenetic types of amphiboles have been derived using regression equations.
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