THE INTRUSIVE CONTACT STRUCTURAL SYSTEM OF THE DAYUNSHAN INTRUSION

Through a study of the metallotectonics of the Taolin lead-Zinc deposit o Hunan, the author has found that there exists a special structural type in the Dayunshan area.It consists of three major parts:intraintrusion.structure, contact zone structure and wall rock structure adjacent to the contact zone, which exhibit different deformation features.Genetically this structural type is not only related to the internal agent generated in the process of emplacement of the intrusion, but also incorporated in the teconic stress field controlling the regional structural disburbance.The authors hold that it should be a unique structural system that has not yet attracted enough attention, i.e.the intrusive contact structural system. The fundamental characteristics and mechanism of formation of the structural system are discussed in terms of the field information and model experiments and computer analysis. It is considered that one of the important factors causing the shaping of the structural system is the existence of intrtusive contact planes—weakness planes,while the formation of this special boundary condition is associated with the preexisting structural space of"dual weakn ess"in the Dayunshan area and the forceful injection of the magma along the space.A vast amount of data show that the generation,development and evolution of the structural system experienced a lengthy geologic history from late Yanshanian to middle Himalayan time and a complex deformation process. This kind of structural type has also been noticed by the authors in other areas.Therefore an in-depth study of the intrusive contact structural system will be of major theoretical and practical significance for understanding some undetermined structural types and some ore deposit types which are genetically unclear but obviously related to them.