云开地区变质基底岩性复杂,浅变质岩系与深变质岩系混杂,缺乏填图标志。在1/5万区调中,首次对云开地区的变质基底采用岩性段填图。根据岩性组合、特殊岩性段、空间展布、接触关系等特征,将云开岩群划分为第一岩组、第二岩组、第三岩组、山坪岩组及第四岩组5个组级构造岩石地层单位,并认为云开岩群与天堂山岩群为同一套地层。山坪岩组岩性以硅质岩为主,厚10~30m,广泛分布于两广云开地区,为云开岩群第三岩组与第四岩组之间的分界标志。 The metamorphic basement in the Yunkai area is complex in lithology, and the shallow metamorphic rocks and the deep metamorphic rocks are mixed with each other, which lacks the mapping symbols. In 1/50000 area adjustment, for the first time on the open area of ​​the metamorphic basement using lithology segment mapping. According to characteristics of lithologic assemblage, special lithology, spatial distribution and contact relationship, the group of Yun-Kai rocks are divided into the first rock group, the second rock group, the third rock group, the Shanping rock group and the fourth rock group 5 sets of tectonic units of lithostratigraphy, and think that the open rock group and the Tiantangshan rock group are the same set of strata. The Shanping rock group is dominated by siliceous rocks with a thickness of 10-30 m and is widely distributed in the Yun-Kai area of ​​Guangdong and Guangxi. It is the boundary marker between the third rock group and the fourth rock group in the Yunkai Group.