Shear Wave Splitting Evidence for Keel-Deflected Mantle Flow at the Northern Margin of the Ordos Block and Its Implications for the Ongoing Modification of Craton Lithosphere

Li，Shilin1; Guo，Zhen1,2,3; Chen，Yongshun John1,2; Yu，Yong1; Morgan，Jason P.1

2020-12-01

10.1029/2020JB020485

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH   影响因子和分区

2169-9313

2169-9356

We use 123 temporary seismic stations to determine shear wave splitting patterns beneath the northern Ordos block and its surrounding areas. The mapped pattern of anisotropy shows a dramatic arc-shaped anisotropy contrast beneath the northeastern Ordos block that closely follows the lateral fast/slow-velocity interface seen in a recent surface tomographic model at ~140 km depth. Both seismic anisotropy and velocity appear to demarcate the current boundary of cratonic lithosphere in the upper mantle at this depth, located >150 km south of the geological surface boundary of cratonic crust. We suggest that the craton's keel in the northeastern corner of Ordos block has already been eroded and replaced by warmer asthenospheric mantle, while the cratonic crust above this “missing” keel has yet to be destroyed by deformation and/or crustal metamorphism, thus creating the keel divot at the northeastern corner of the Ordos block. The fast polarization direction of anisotropy tends to wrap around the northeastern margin of the Ordos block, changing from predominantly NW-SE beneath the western part of the margin to nearly E-W beneath the east. We suggest this pattern reflects that plate motion-related asthenosphere flow is being deflected by the cratonic keel of the Ordos block. Such keel-deflected asthenospheric flow could enhance the erosion of the craton's keel, leading to the observed lithospheric reworking beneath this region.

craton crust and keel boundary craton reworking keel-deflected mantle flow Ordos block seismic anisotropy

SCI

英语

第一 ; 通讯

National Natural Science Foundation of China[41774052,41904056,41974052] ; Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou)[GML2019ZD0210] ; Science, Technology and Innovation Commission of Shenzhen Municipality[JCYJ20190809143817880] ; Shenzhen Key Laboratory of Marine Archaea Geo-Omics[ZDSYS20180208184349083]

Geochemistry & Geophysics

Geochemistry & Geophysics

WOS:000603664600017

AMER GEOPHYSICAL UNION

GEOSCIENCES

2-s2.0-85098210643

Scopus

1.Department of Ocean Science and Engineering,Southern University of Science and Technology,Shenzhen,China
2.Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou),Guangzhou,China
3.Shanghai Sheshan National Geophysical Observatory,Shanghai,China

Li，Shilin,Guo，Zhen,Chen，Yongshun John,et al. Shear Wave Splitting Evidence for Keel-Deflected Mantle Flow at the Northern Margin of the Ordos Block and Its Implications for the Ongoing Modification of Craton Lithosphere[J]. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,2020,125(12).

Li，Shilin,Guo，Zhen,Chen，Yongshun John,Yu，Yong,&Morgan，Jason P..(2020).Shear Wave Splitting Evidence for Keel-Deflected Mantle Flow at the Northern Margin of the Ordos Block and Its Implications for the Ongoing Modification of Craton Lithosphere.JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH,125(12).

Li，Shilin,et al."Shear Wave Splitting Evidence for Keel-Deflected Mantle Flow at the Northern Margin of the Ordos Block and Its Implications for the Ongoing Modification of Craton Lithosphere".JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 125.12(2020).