THE TECTONIC EVOLUTIONARY SUCCESSION OF THE ARCHEANC CRUST IN THE ANSHAN AREA

The Archean crust in the Anshan area is composed mainly of two metamorphic rockseries, i.e. granitic rocks （making up about 90%） and supracrustal rocks （i. e. iron-bearing rock series）.Granite may be subdivided into the Tiejiashan granite and the Gongchangling granite, while thesupracurstal rocks are composed of itabirite and sericite -chlorite -quartz schist.The supracrustal rocks were deposited over 3000 Ma ago and the Tiejiashan granite was em-placed 2900 Ma ago. The first phase of ductile deformation took place slightly later. NE gneis-sosity occurred in the Tiejiashan granite, whereas homoclines with a NE axial direction and axialplane schistosity S₁ were formed in supracrustal rocks. The Gongchangling granite was emplacedabout 2600 Ma ago and slightly later the second phase of ductile deformation happened, givingrise to NNW reverse shear zones and ENE strike -slip shear zones and producing schistosity S₂ ofparallel ductile shear zones in iron -bearing rock series The third phase of ductile deformationtook place 2000 Ma ago. The characters of ENE and NNW shear zones formed in this phase arecontrary to those of the second phase. The deformation of ductile shear zones of the above-men-tioned ductile shear zones formed successively gneiss, mylonite and tectonic schist that correspondto the three phases.