Moho depth and tectonic implications of the western United States: insights from gravity data interpretation

Abstract

In this research, we figure out the lithospheric structures of the western U.S. and assess its tectonic implications with a high resolution using dense gravity data. Gravity data with high spatial resolution enables detailed mapping capabilities, overwhelming other geophysical data. To investigate the physical basis for support of topography in the western U.S., we employed the parker-Oldenburg algorithm to gravity to calculate the depth to Moho. The estimated depth to Moho shows an excellent spatial correlation with the physiographic provinces in the study area following an eastward thicking pattern. Moho of the stable craton reaches 50 km, whereas the western margin shows a shallow Moho of 20 km. Moreover, to assess the tectonic implication of Moho in the study area, we calculated the crustal compensation load to evaluate the isostatic state in the study area. The calculated compensation loads provide isostatic compensation for large-scale crustal structures, such as the broad, elevated Basin and Range Province. To assess the contribution of the crust and mantle to the topographic deformation in the study area, we calculated the crust topography and mantle topography. The Wyoming Craton and Great Plains have negative mantle topography values, contrasting with the relatively constant values in the southern Rockies, Colorado Plateau, and Basin and Range. Crustal topography reveals significant crustal support from the southern Rockies and the Wyoming craton. In addition, we estimated the lithospheric mantle thickness and the depth of the Lithosphere–Asthenosphere Boundary (LAB); the mantle thickness has values reaching 90 km at the stable eastern craton with LAB depth reaching 140 km. This research demonstrates the effect of the tectonic regime on the study area and the implications of this tectonic on the lithospheric structures with a high spatial resolution of a few hundred meters.

Geophysical and Geochemical Constraints on Magma Storage Depths Along the Cascade Arc: Knowns and Unknowns

“…These RMSE mean that these two Cpx‐only barometers can identify magma storage depths within ∼15–18 km of the true value at 1 σ confidence. The relatively thick crust in the Cascades (∼40–50 km, Jiang et al., 2023; Kiser et al., 2016; Parsons et al., 1998; Shehata & Mizunaga, 2022) means that Cpx‐based barometry can roughly distinguish between storage in the upper, mid and lower crust at best. Another advantage of these two barometers is that they are independent of temperature and H 2 O content, which are difficult to estimate from Cpx compositions alone (Wieser et al., 2023b).…”

Geophysical and Geochemical Constraints on Magma Storage Depths along the Cascade Arc: Knowns and Unknowns

“…These RMSE mean that these two Cpx-only barometers can identify magma storage depths within a window spanning ~15-18 km at 1σ confidence. The relatively thick crust in the Cascades (~40-50 km, Jiang et al, 2023;Kiser et al, 2016;Parsons et al, 1998;Shehata and Mizunaga, 2022) means that Cpx-based barometry can roughly distinguish between storage in the upper, mid and lower crust at best. Another advantage of these two barometers is that they are independent of temperature and H2O content, which are difficult to estimate from Cpx compositions alone (Wieser et al, 2023b).…”

The role of crustal anatexis in porphyry copper ore formation during flat-slab subduction: Insights from the Laramide Belt, SW USA

“…4c and 6). This would imply that during peak Laramide orogenesis: (1) supra-solidus temperatures occurred at depths >25 km; and (2) the CPTZ crust must have been at least ~50-60 km thick, based on the addition of the ~28 km overburden to the present-day Moho depth of ~25-30 km beneath central Arizona 64 . This is consistent with paleo-crustal thickness estimates derived from Sr/Y and La/Yb ratios of Laramide granitic rocks 65 and indicates the crust was thinned by a factor of two during subsequent Basin and Range extension.…”