1. All these minerals were altered during the greenschist facies retromorphism. 2. The slates are highly cleaved and metamorphosed as high as lower greenschist facies . 3. They consist of interlayered sedimentary and volcanic flow rocks metamorphosed to low greenschist facies . 4. In greater detail the greenschist facies is subdivided into subgreenschist, lower and upper greenschist. 5. The greenstone belts of the various archean cratons are commonly altered to the greenschist facies . 6. These rocks therefore underwent chlorite ( chloritization ) indicating retrograde metamorphism under greenschist facies conditions. 7. The chloritization of the biotite is a clear sign for retrograde metamorphic overprinting under greenschist facies conditions. 8. The ophiolites of the Zermatt-Saas zone are mostly ultramafic rocks with greenschist facies mineralogy : serpentinites. 9. Regional metamorphism has converted the shale to a low greenschist facies , where clay is converted to chlorite. 10. The sedimentary rocks that were laid down in the basin are often weakly metamorphic ( greenschist facies ).
