Rheology And Fabric Characteristics Of Mantle Peridotite Xenoliths From Changbai Mountain

Mantle peridotite xenoliths are carried out by alkaline basalt or kimberlite from the upper mantle to the surface.It provides a unique"windows"for people to understand and study the upper mantle composition,structure,thermal state,lattice preferred orientation?LPO?of olivine and pyroxene and deep geological processes of the upper mantle.And thus,it is of great significance for the geodynamics.Mantle peridotite xenoliths in Changbai Mountain area,located near the northeast part of the edge of North China Craton constrain the nature and evolution of the underneath subcontinental lithospheric mantle?SCLM?.In fact,research on these peridotite xenoliths in Changbai Mountain are few and some extent will filled up the gaps in the previous studies that relying on geophysics or geochemistry.Here,we report major element composition of the xenoliths minerals,the P-T conditions,xenoliths microstructure,and olivines and pyroxenes fabric in Changbai Mountain area.And,the subcontinental lithospheric mantle in this area is constrained.Olivine in xenoliths is mainly belong to forsterite with Mg#value between 89-91.Microstructures are characterized by free dislocation,dislocation walls,kink bands,subgrains and so on,indicating a high temperature plastic deformation.The fabric of olivine is a typical A-type?010?[100]is considering as the dominant activation slip system,with low water contents and low stresses and maybe with a wide range of temperature).The equilibration temperature conditions,calculated based on equilibration mineral parts,indicate the evolution of peridotites in a the range of 850-1100?.The differential stress computed by the size of recrystallized grain is 22-36 MPa.Based on those condition parameters and flow law estimated by laboratory deformation data,we calculated the effective strain rate of the upper mantle is about 1.5×10^-15-1.1×10-11s^-1,and the effective viscosity 8.5×10¹¹-6.6×10¹⁵MPa·s.The study is the first time directly reveal rheological and fabric properties of the upper mantle in Changbai Mountain,of which will provide constraints for the geodynamic activities and give new data for further research.