PdS Receiver Function Evidence for Mafic Underplating in the Superior Craton: A Discussion About Cratonic Stabilization

Abstract:

The Trans-Hudson orogen (THO) in the north central United States represents a major suturing event between the Wyoming and Superior Archean provinces. It is bounded to the south by the NE-SW striking Yavapai province, which was accreted along the southeastern margin of North America between 1.71 and 1.68 Ga and was one of a series of major collisional events responsible for the assembly of Laurentia. In this study, PdS teleseismic receiver functions were used to investigate the deep crustal structure associated with these collisions. Using data from over 800 broadband seismic stations distributed throughout the Great Plains/Midcontinent region, we calculated .5 Hz receiver functions using 245 M > 6.0 teleseismic events. The receiver functions were then CCP (common conversion point) stacked to create a 3D image volume. Profiles through this image volume show evidence of crustal scale thrusting of the Wyoming province in the west over the Superior province in the east and structural underplating associated with the Yavapai-Superior boundary. We also performed a density analysis of the region using the 2p1s and 0p1s receiver function phases from 233 stations. These data indicate a relatively low Moho density contrast throughout the THO and northern Yavapai region associated with a region of thickened crust (> 50 km), which we interpret to be evidence of a dense lower crustal layer that may be the result mafic underplating. Additionally, we investigate the role that this dense layer may have on the stabilization of the Superior craton and others relative to compositionally and thermally derived density variations in the mantle lithosphere.