LITHODEMIC UNITS OF GRANITOID ROCKS OF THE HUICHIZI COMPOSITE INTRUSION AND ITS GEOLOGICAL SIGNIFICANCE IN EAST QINLING

During the 1:50000 regional geological surveys of the Shiziping Sheet,the Huichizi com-posite intrusion occurring in the Qinling Group was disintegrated using the principle andmethod for the classification of granitoid rocks. The intrusion is divided into about 80 small in-trusions,and nine units are established,which are grouped from older to younger into the Caiji-.agou, Qihe and Minglanghe sequences. The authors briefly describe the types, mineralogicalcompositions, textural features, contact relationships and evolutionary features of the rocks ofvarious units and sequences。 This intrusion generally shows an evolutionary succession fromtonalite through granodiorite to monzonitic granite, implying that the magmatic rocks resuItedfrom multiple fusion,differentiation and emplacement.