DISINTEGRATION OF THE ARCHEAN QIANXI GROUP IN EASTERN HEBEI

On the basis of a lot of field geological surveys and stratigraphical, petrological and petrochemical studies, it is indicated that the Archean Qianxi Group in eastern Hebei is composed of over 80% felsic gneiss and less than 20% supracrustal rocks. Felsic gneiss is mainly represented by a plutonic granite complex of the tonalite-granodiorie-granite association. The supracrustal rocks include two parts: （1） stratified volcanic rocks, volcano-sedimentary rocks and sedimentary rocks, and （2） old dyke rocks and basic stratified intrusions, which generally occur as inclusions of small sizes and diverse shapes in the granite complex. Owing to strong metamorphism and deformation, these inclusions have been stretched to different degrees and are arranged alternately with the granite complex, thus forming "structural （or deformed）-composional layers" that change erratically both longitudinally and laterally. Therefore the stratigraphic sequence of the Qianxi Group defined previously is actually the product of combination and incorporation of "structural-compositional layers" rather than real stratigraphic sequence, so should be disintegrated.