Tectonic Deformation And Evolution Of Liaohe Group In Lianshanguan Area,Liaodong Peninsula

The Paleoproterozoic Liaohe Group in the Lianshanguan area of the Liaodong Peninsula is distributed in the southern margin of the Longgang block of Archean.It is a part of the Jiao-Liao-Ji paleoproterozoic orogenic belt and one of the intact outlying areas of all rock groups in the liaohe group.The previous tectonic evolution in this area is mainly a three-stage tectonic deformation event,which is successively a extension-contract-contract deformation event.At present,the understanding of the formation environment of the early tectonic deformation events in the Liaohe Group is still controversial.Therefore,clarifying the tectonic deformation characteristics and evolution sequences of each group of the Liaohe Group is of great significance for elucidating the early tectonic properties of the Jiao-Liao-Ji orogenic belt.This paper takes the Liaohe group in Lianshanguan area as the research object.We carried out morphological statistics and classification of fold structures developed in each rock group of the liaohe group,statistical analysis and analysis of linear structures associated with fold structural elements,and EBSD fabric analysis and statistical analysis of mechanical twinning morphology of calcite in large area of exposed calcite marble.By indicating the outcrop observations and the measured occurrence data,the rock deformation characteristics of the Liaohe group in Lianshanguan area are very similar,which is embodied in the unity of linear structure development and the deformation characteristics of multiple stages of fold structure development.The structural trace mainly shows that fold structure and mineral tensile lineation are generally developed in all rock groups.In the early stage of tectonic activity,due to the large thickness of rock strata in each rock group,the folds caused by contraction and compression were not obvious,and they were mainly composed of bedding shear,sheath folds in multiple cambium and mineral stretching lineation.In the later stage,with the progress of orogeny,the compressive effect became more obvious,which mainly resulted in the significant development of stratified folds,but did not affect the linear structure.It mainly resulted in the increase of the tight degree of the two wings of the intra-layer sheath folds and the development of the structure of boudinage.The marble of Langzishan formation,Gaojiayu formation and Dashiqiao formation is analyzed by calcite EBSD fabric analysis,data shows that the rock group have suffered different degrees of shearing action,combined with its macroscopic deformation performance known in ductile shear zone in contact with the rock group,but because of the difference of lithology show the strength of the ductile shear zone is not the same.Based on the typical strata in the area of marble calcite mechanical twin morphology and calcite CPO fabric characteristics,Lianshanguan region of the Liaohe group of ductile deformation temperature at 170? to 400?.Based on the above studies,we conclude that Lianshanguan region,the north liaohe group are mainly composed of a period of progressive deformation event,the progressive deformation event took the form of transpression,namely vertical horizon is given priority to with shrink extrusion structure,parallel to the horizon is given priority to with simple shearing action,the harmonious and unified,due to different depth in the crust rock group,its deformation performance is different.