STRUCTURAL TRANSPOSITION OF METAMORPHIC COMPLEXES AND ITS SIGNIFICANCE——A CASE STUDY OF THE ARCHEAN CHONGLI GROUP AND WULASHAN GROUP IN THE NORTHERN PART OF THE NORTH CHINA PLATFORM

This paper reviews the concept of structural transposition.Outstanding examples of transposition are cited from the Archean Chongli Group and Wulashan Group rocks in the northern part of the North China platform to discuss the process of transposition and its implication for regional deformation. Detailed structural mapping and special structural study of selected areas suggest that that transposition is a complex chemical and mechanical process and a combined effect of such processes as compressive strain or strong flatte- ning,heterogeneous simple shear（flow）and metamorphic differentiation.As a result,a strongly transposed sequence and layering(i.e.pseudo-stratigraphic sequence in the metamorphic complexes are produced,which contains continuosly intraformational disrupted and rotated segments.Thus in these areas,what are seen in plan and on steep mountain slopes are not a stratigraphic succession,but a tectonic pile or stack.The bedding information collected from small outcrops tells nothing of the gross distribution of stratigraphic horizons,direction of younging and stratigraphic thickness on a regional scale.To obtain this information it is necessary to make an inegrated analysis of the data of the of the regional structures and carry out detailed mapping.