Recent craton growth by slab stacking beneath Wyoming

Abstract

Available online xxxx Editor: P. Shearer Keywords: Wyoming craton Shatsky conjugate tomography Laramide Sevier Colorado Mineral BeltSeismic tomography images high-velocity mantle beneath the Wyoming craton extending to >250 km depth. Although xenoliths and isostatic arguments suggest that this mantle is depleted of basaltic component, it is not typical craton: its NE elongate shape extends SW of the Wyoming craton; xenoliths suggest that the base of Archean mantle was truncated from ∼180-200 to ∼140-150 km depth since the Devonian, and that the deeper mantle is younger than ∼200 Ma. The Sevier-Laramide orogeny is the only significant Phanerozoic tectonic event to have affected the region, and presumably caused the truncation. Apparently, the base of the Wyoming craton was removed and young, depleted mantle was emplaced beneath the Wyoming craton during the Sevier-Laramide orogeny. We suggest that the Wyoming craton experienced a ∼75 Ma phase of growth through a three-stage process. First, flat-slab subduction removed 40-50 km off the base of the Archean Wyoming craton. This was followed by emplacement of basaltdepleted ocean plateau mantle lithosphere of the Shatsky Rise conjugate, which arrived in the early Laramide. The geologic recorded of vertical motion in the Wyoming region suggests that the plateau's crust escaped into the Earth's interior at 70-75 Ma. Initiation of Colorado Mineral Belt magmatism at this time may represent a slab rupture through which the ocean crust escaped.

Early Inception of the Laramide Orogeny in Southwestern Montana and Northern Wyoming: Implications for Models of Flat‐Slab Subduction

“…Previous studies of uplift, basin subsidence, and erosional histories of the Laramide in Wyoming indicate mostly early Cenozoic ages (e.g., Peyton et al, ; Stevens et al, ); these relatively young ages may represent thermal processes related to westward roll‐back of the subducting slab (Fan & Carrapa, ) or accretion of Shatsky conjugate depleted mantle lithosphere beneath Wyoming and the associated upper crustal deformation and subsequent removal (Humphreys et al, ; Stevens et al, ). Westward to southwestward migration of magmatism in the mid‐Cenozoic is consistent with the history of the stress field (Bird, ) and can be explained by westward migration of the Farallon plate hingeline and falling away of the slab (referred to as slab rollback ; Best et al, ; Coney & Reynolds, ; Constenius, ; Dickinson & Snyder, ).…”

Revised exhumation history of the Wind River Range, WY, and implications for Laramide tectonics

“…The timing of exhumation determined by thermokinetic modeling is consistent with timing of accretion of Shatsky Rise depleted mantle lithosphere under Wyoming and associated upper crustal deformation [ Humphreys et al , ]. Alternatively, our data could be interpreted to represent a tectonothermal response to plateau removal [ Liu et al , ; Liu and Gurnis , ].…”

“…This is consistent with timing of rapid sedimentation in nearby basins [ Dickinson et al , ]. The timing of exhumation recorded by AFT data in the Wind River Range is consistent with both accretion of Shatsky Rise depleted mantle lithosphere under Wyoming [ Humphreys et al , ] and with inverse convection model of Laramide deformation presented by Liu et al [] but does not distinguish between these models. Regionally, these results constrain the timing and rate of exhumation during Laramide deformation.…”

The meaning of midlithospheric discontinuities: A case study in the northern U.S. craton

“…Within the Wyoming craton, both pre‐Laramide deformation, thought to be recorded by Moho topography [ Yeck et al ., ], and Laramide crustal shortening [ Erslev and Koenig , ] occurred. However, xenolith data indicate that the mantle lithosphere appears to have remained intact [ Eggler et al ., ; Carlson et al ., ], except in the northern Wyoming craton where the mantle lithosphere deeper than 150 km may have been replaced [ Carlson et al ., ], possibly due to Laramide subduction [ Humphreys et al ., ].…”