Hydrating laterally extensive regions of continental lithosphere by flat subduction: A pilot study from the North American Cordillera

The formation of volcanic centers at the Colorado Plateau as a result of the passage of aqueous fluid through the oceanic lithosphere and the subcontinental mantle: New implications for the planetary water cycle in the western United States

“…2e and f). This observation corroborates the idea of Humphreys et al (2003) for the presence of a hydrous upwelling at the base of the subcontinental mantle; this upwelling is attributed to aqueous fluid in an interconnected network that can be detected in defect structures within nominally anhydrous minerals and to the formation of hydrous minerals such as antigorite (van der Lee et al, 2008;Gerya et al, 2009;Sommer et al, 2008;Sommer and Gauert, 2011).…”

“…According to Byerlee's law using data sets for a "wet" dunite rheology, the differential stress field in the lithospheric mantle would be up to 3 times higher at low temperatures (∼600 • C) compared to a hot rheology (∼1225 • C); this result is contradictory to the observed S-wave velocity anomalies (Fig. 2) and high stress would lead to a cracking process in the lithospheric mantle, mantle wedge and especially in the subcontinental mantle above (Strehlau and Meissner, 1987;Sommer and Gauert, 2011). These observations indicate that water in the lithospheric mantle and especially in the subcontinental mantle may also be present within monomineralic, interphase grain boundaries and lead to the formation of hydrous minerals such as antigorite at the temperature below ∼600 • C in the subcontinental mantle or/and in the mantle wedge (Sommer, 2009).…”

“…Sommer et al (2008) reported up to 10 times higher water concentrations at monomineralic and interphase grain boundaries than at the line and point defects in the crystal matrix. Temperatures in a flat subduction scenario are believed to be extremely low (Sommer, 2009;Gerya et al, 2009;Sommer and Gauert, 2011). According to Byerlee's law using data sets for a "wet" dunite rheology, the differential stress field in the lithospheric mantle would be up to 3 times higher at low temperatures (∼600 • C) compared to a hot rheology (∼1225 • C); this result is contradictory to the observed S-wave velocity anomalies (Fig.…”

“…The other model hypothesizes the subduction of an oceanic ridge or an earlier break-up of the Farallon plate at the edge of the Colorado Plateau and the resulting formation of a slab window during the Late Oligocene to Early Miocene (van der Lee and Nolet, 1997;Humphreys, 2008;Sommer and Gauert, 2011;Sigloch et al, 2008). Subduction of oceanic ridges, oceanic plateaus, and seamount chains can occur in different tectonic settings (Gerya et al, 2009).…”

A joint local and teleseismic tomography study of the Mississippi Embayment and New Madrid Seismic Zone

“…Water can reduce mantle seismic velocities by increasing the water content in minerals such as olivine, resulting in increased anelasticity and attenuation [ Dixon et al ., ]. Water can also reduce V p and V s by metasomatic alteration of mantle peridotite (or eclogite) [ Sobolev and Babeyko , ; Goes and Van der Lee , ; Mainprice et al ., ; Pollitz and Mooney , ], resulting in the formation of low‐velocity minerals such as phlogopite, chlorite, and talc [ Sommer and Gauert , ]. Possible sources of elevated water levels include rising, hydrated asthenosphere at hotspot locations [ Pollitz and Mooney , ] and dehydration of descending slabs [ Dixon et al ., ; Santosh et al ., ; Chen et al ., ].…”