科研之友
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摘要
Upper mantle fabric, as detected by shear wave splitting measurements, records lithospheric strain history that may be related to past tectonic events. We present SKS (core-refracted shear wave) splitting measurements taken around the western Great Lakes, North America: the Archean Superior Province (SP) and surroundings. We analyze 40 sites in the USA and 5 in Canada and outline a region of strong anisotropy corresponding to a high-velocity zone in tomographic models, which we dub the Western Superior Mantle Anomaly (WSMA) and interpret to represent a preserved fabric from accretion of the SP. To the southwest of the WSMA, we locate a region of rotated fast direction corresponding to a linear low-velocity feature observed by tomography and which may represent a failed branch of the Mid-Continent Rift. Further south, within the Minnesota River Valley Terrane, the split times drop to near zero, suggesting isotropic lithosphere resulting from vertical (diapiric) rather than horizontal tectonic processes.
- 出版日期2013-9-16
