Young Silicic Magmatism of the Greater Caucasus, Russia, with implication for its delamination origin based on zircon petrochronology and thermomechanical modeling

Building a Young Mountain Range: Insight Into the Growth of the Greater Caucasus Mountains From Detrital Zircon (U‐Th)/He Thermochronology and 10Be Erosion Rates

“…If the apparent acceleration in exhumation rates was driven by slab detachment (Forte et al, 2016;Mumladze et al, 2015;Vincent et al, 2020), it would require detachment to have occurred within this broad window of ∼4-0.5 Ma. This range implies a slightly more recent time frame than that proposed by Vincent et al (2020) or as suggested by modeling of silicic volcanism generation (Bindeman et al, 2021) both of which suggest detachment at ∼5 Ma. However, models of the isostatic response to slab detachment do suggest a time lag between detachment and a change in rock uplift, which depending on the depth of the detachment could range from ∼0.6 to 1.6 Myr (Duretz et al, 2011), so detachment could still occur at ∼5 Ma and result in the acceleration of exhumation we see here.…”

“…Importantly, our data do not directly refute the occurrence of slab detachment or other form of mantle upwelling in the western GC, but rather highlight that there is not a clear indication of this event influencing either long‐term or millenial exhumation rates. Given the variety of evidence consistent with detachment in the western GC (e.g., Bindeman et al., 2021; Hafkenscheid et al., 2006; Kaban et al., 2018; Koulakov et al., 2012; Mumladze et al., 2015; van der Meer et al., 2018; Zor, 2008) or more broadly the presence of some form of mantle upwelling beneath this portion of the range (e.g., Ershov et al., 2003; Faccenna & Becker, 2010; Motavalli‐Anbaran et al., 2016; Ruppel & McNutt, 1990), the lack of a clear exhumation signal remains puzzling and highlights the necessity of more detailed work in the region to provide a more complete record of upper‐crustal shortening along‐strike, exhumation records in the central and eastern portion of the GC, and refined local tomographic models of the crustal and lithospheric structure as the majority of the geophysical results for the western GC rely on global datasets as opposed to local observations. Specifically, this hypothesis could be further constrained with more low‐temperature thermochronology within the “thermochronologic gap” and perhaps the addition of more comparable detrital thermochronology datasets throughout the range to allow for more direct comparisons along‐ and across‐strike.…”

“…There is independent evidence for possible slab detachment from petrochronology, stable isotopic analyses of zircons, and thermomechanical modeling of the origin of magmas that erupted ignimbrite sequences around Mt. Elbrus in the western GC (Figure 1a), where Bindeman et al (2021) relate their analysis of the silicic volcanism in the GC to this hypothesized slab detachment and date its occurrence to ∼5 Ma.…”

“…Elbrus in the western GC (Figure 1a), where Bindeman et al. (2021) relate their analysis of the silicic volcanism in the GC to this hypothesized slab detachment and date its occurrence to ∼5 Ma.…”

A Preliminary Framework for Magmatism in Modern Continental Back‐Arc Basins and Its Application to the Triassic‐Jurassic Tectonic Evolution of the Caucasus

“…Jurassic volcanic rocks exposed on the southern flank have been interpreted by some authors as arc rocks (Hässig et al., 2020; Hess et al., 1995; Mengel et al., 1987), but most studies view them as resulting from extension within the Caucasus Basin (e.g., Cowgill et al., 2016; Lordkipanidze et al., 1989; McCann et al., 2010; Saintot et al., 2006; Vincent et al., 2016). Although Jurassic magmatic rocks with geochemical signatures indicating a depleted mantle source similar to that of D‐MORB have been reported (Lordkipanidze et al., 1989; McCann et al., 2010), some authors have asserted that these rocks represent extreme thinning of continental lithosphere rather than true back‐arc spreading (McCann et al., 2010; Vincent et al., 2016, 2018), though this view is contested (Bindeman et al., 2021; Cowgill et al., 2016, 2018; Mumladze et al., 2015).…”