Deformation and seismic anisotropy of the lithospheric mantle in southern Songliao Basin:Constraints from peridotite xenoliths
SKS wave splitting measurements revealed that the distribution of fast wave direction in the Songliao Basin is complex.The formation of seismic anisotropy is restricted by the lack of study in lithospheric mantle deformation.To better understand lithospheric deformation and upper mantle anisotropy observed in this region,we performed studies on petrology,geochemistry,microstructures and seismic anisotropy of peridotite xenoliths collected from Shuangliao,southern Songliao Basin.The results show that equilibrium temperature of peridotite xenoliths in Shuangliao is 893～1152℃,which suggest that peridotite xenoliths were derived from the lithospheric mantle.The mantle peridotite xenoliths show three types crystallographic preferred orientation(CPO)of olivine,which are A-type,D-type and AG-type CPO.The AG-type and D-type olivine CPO were probably formed by lithospheric deformation caused by the subduction and retreat of western Pacific Plate.Moreover,the AG-type olivine CPO may be formed by deformation in the presence of melt.The VP anisotropy(AVP)and maximum shear wave anisotropy(AVSmax)of peridotite xenoliths calculated from the fabric of xenoliths are 4.79％～11.80％and 3.13％～7.93％,respectively.Based on the seismic properties of peridotite xenoliths and geophysical measurements,it is inferred that the complex SKS wave splitting is attributed to the lithospheric mantle in the southern Songliao Basin with a vertical structural frame.
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