Deformation of the Subcontinental Lithospheric Mantle in NE China: Constraints from Rheological and Fabric Study of Mantle Peridotite Xenoliths from Jiaohe, Jilin Province

Mantle peridotite xenoliths in Jiaohe City, located near the northern part of the Tan-Lu fault, are key evidence for constraining the nature and evolution of the subcontinental lithospheric mantle (SCLM) of the NE China. Geochemical characteristics of Jiaohe peridotite xenoliths have been well studied, whereas the microstructures and associated fabrics remain poorly known. We report here major element composition of the constituent minerals, P-T conditions, microstructure, lattice preferred orientations (LPOs) of a set of xenoliths having coarse-grained and granuloblastic to porphyroclastic textures. These xenoliths are characterized by forsterite content of 89–91 in olivine. Dislocation microstructures, in olivine crystals revealed by oxidation decoration technique, are characterized by free dislocation, dislocation walls, dislocation loops and subgrains. Microstructures and deformation mechanism maps indicate that dislocation creep is the dominant deformation mechanism of almost anhydrous olivine in the SCLM. In most samples, the observed LPOs of olivine are typical A-type fabric. Stresses measured in the xenoliths using several olivine piezometers are ∼2.7–8.5 MPa. The equilibration temperature conditions, calculated using several geo-thermometers, indicate the equilibrium temperature condition of peridotites in a range of 891 to 993 °C. These results provide rheological constraint on the deformation of the SCLM in Jiaohe. Combined with the data for mantle xenoliths from adjacent regions, a heterogeneous evolution of the lithosphere deformation is inferred at the Jiaohe region. We propose that characteristics of the studied peridotite may be related to the Tan-Lu fault.