Metamorphic mineral assemblage and metamorphic zones of Yangshigou area in western Beijing

The division of contact thermal metamorphic zones provides a strong basis for the study of metamorphic processes. According to metamorphic mineral assemblage of Yangshigou in western Beijing and its spatial distribution in strata, the contact thermal metamorphic zones of this area is divided and the formation stages of metamorphism were analyzed. Due to the intrusion of the Fangshan magmatic rock, surrounding rocks suffered from different degree of contact thermal metamorphism, which formed various metamorphic minerals. In particular types of rocks, there are regular combinations of characteristic metamorphic minerals. Using polarizing microscope and X-ray fluorescence spectroscopy, it is divided into the diopside-tremolite zone, the mica zone, the andalusite zone and the sericite zone, indicating that the degree of rock metamorphism decreased with the distance from magmaticrock.With the formation of different metamorphic minerals at different stages of magmatic intrusion, the contact thermal metamorphism is divided into five progressive stages.