The Damiao anorthosite complex occurs in the high-grade metamorphic Precambrian rocksin the axial part of the Nei Mongol(Inner Mongolia)Anticline.It is a monoclinat,layeredintrusion,with distinguishable layers of anorthosite,monzonite and quartz-monzonite frombottom to top.Gradation evidence can be noticed between these layers.Accumulation struc-ture is obvious in anorthositic rocks.In the anorthositic rocks feldspars,mainly antiperthiteand plagioclase,are hosted with An 44—49,while in the acid rock facies,perthite and plagio-clase are present.The complex investigated can be assigned to andesine-type rocks.Both the Damiao anorthosites and the Miyun rapakivi granites are calc-alkaline in termsof petrochemical characteristics,and the latter exhibits a very close petrochemical similarity,i.e..high in Al and K,with the acid members in the upper layers of the complex at Damiao.In view of the close temporal-spatial relationship and the resemblance of rock structure,itis thought that the two suites are resulted from a single parent magma under approximate tec-tonic environments,and that gravitative fractionation may have played an important role intheir evolution.Calculations show that the parent magma responsible for the suites bears obvious re-semblance to quartz diorite and quartz monzonite in composition,which is in agreement withthe experiments by T.H.Green.The Damiao anorthosite complex is characterized by deepsource and shallow emplacement as evidenced by high-pressure and high-temperature experi-ments,geothermometry and petrochemical features as well as the occurrence of both pigeoniteand primary“Al-pyroxene”. The Damiao anorthosite complex occurs in the high-grade metamorphic Precambrian rocks in the axial part of the Nei Mongol (Inner Mongolia) Anticline. It is a monoclinat, layered intrusion, with distinguishable layers of anorthosite, monzonite and quartz-monzonite from bottom to top. Gradation evidence In the anorthositic rocks feldspars, mainly antiperthite and plagioclase, are hosted with An 44-49, while in the acid rock facies, perthite and plagio-clase are present. The complex investigated can be assigned to andesine-type rocks.Both the Damiao anorthosites and the Miyun rapakivi granites are calc-alkaline in termsof petrochemical characteristics, and the latter exhibits a very close petrochemical similarity, ie. High in Al and K, with the acid members in the upper layers of the complex at Damiao. In view of the close temporal-spatial relationship and the resemblance of rock structures, itis thought that the tw o suites are resulted from a single parent magma under approximate tec-tonic environments, and that gravitative fractions may have played an important role intheir evolution. Calculations show that the parent magma responsible for the suites bears obvious re-semblance to quartz diorite and quartz monzonite in composition, which is in agreement with the experiments by TH Green. The Damiao anorthosite complex is characterized by deep sources and shallow emplacement as evidenced by high-pressure and high-temperature experi-ments, geothermometry and petrochemical features as well as the occurrence of both pigeonite and primary “Al-pyroxene”.