Deformation and rheological properties of Dashiqiao Formation of Liaohe Group in Hupiyu area, eastern Liaoning Province

Abstract

The study on deformation characters of the Liaohe Group, exposed in eastern Liaoning Province, NE China, provides a key constraint on the tectonic evolution of the Palaeoproterozoic Liao–Ji active belt in the eastern part of the North China Craton (NCC). In this paper, the deformation pattern and mechanism of the Dashiqiao Fm. from Liaohe Group in Hupiyu area have been systematically studied. The present results show that the structure of the investigated Dashiqiao Fm. exhibits a SW bedding‐parallel thrust shearing which is dominated by simple shearing. Simultaneously, S‐SL tectonites were formed under directional flattening. The deformed quartz grains show obvious dislocation slip which is mainly controlled by the low temperature system of the basal <a> slip system, while calcites mainly develop in low temperature with <e> twin slip. Based on microstructural analysis coupled with fabric features, we estimated that the strain rate is 10−12.78–10−8.32 s−1 under the deformation temperature of 350–400°C with a differential stress of 27.3–44.9 MPa. Our macrostructural–microstructural investigation together with previous researches indicates that the Liaohe Group suffered a bedding‐parallel sliding with top‐to‐outside away from the granite body in the core of Hupiyu anticline, corresponding to the uplift of the Hupiyu granite in the early extensional stage. Subsequently, the Hupiyu area suffered SW–NE compression which resulted in the overturn of the southern limb of the Hupiyu anticline and the top‐to‐SW thrusting.