Evidence for a serpentinized plate interface favouring continental subduction

Abstract

The dynamics of continental subduction is largely controlled by the rheological properties of rocks involved along the subduction channel. Serpentinites have low viscosity at geological strain rates. However, compelling geophysical evidence of a serpentinite channel during continental subduction is still lacking. Here we show that anomalously low shear-wave seismic velocities are found beneath the Western Alps, along the plate interface between the European slab and the overlying Adriatic mantle. We propose that these seismic velocities indicate the stacked remnants of a weak fossilised serpentinite channel, which includes both slivers of abyssal serpentinite formed at the ocean floor and mantle-wedge serpentinite formed by fluid release from the subducting slab. Our results suggest that this serpentinized plate interface may have favoured the subduction of continental crust into the upper mantle and the formation/exhumation of ultra-high pressure metamorphic rocks, providing new constraints to develop the conceptual and quantitative understanding of continentalsubduction dynamics.

Seismotectonics at the Transition Between Opposite‐Dipping Slabs (Western Alpine Region)

“…The complex upper crustal structure of the western Alpine region mirrors the complexity documented by geophysical studies in the underlying upper mantle (e.g., Giacomuzzi et al, 2011; Hua et al, 2017; Kästle et al, 2018; Lippitsch et al, 2003; Malusà et al, 2018; Piromallo & Morelli, 2003; Solarino et al, 2018; Sun et al, 2019; Zhao et al, 2016, 2020). The western Alpine area is in fact located at the transition between the SE dipping Alpine slab, to the north, and the SW dipping Apenninic slab, to the south (Figure 1d).…”

“…Arrows summarizing the observations of Figure 5 are color coded according to the depth range (blue: 0 < Z < 12 km; green: 12 < Z < 30 km; orange: Z > 30 km). Cross sections based on Frei et al (1990), Malusà et al (2017), Roure et al (1990), Solarino et al (2018), and Zhao et al (2015, 2020). Acronyms as in Figure 1.…”

“…The resulting data set of relocated events and fault plane solutions was analyzed for different depth ranges and subareas within the framework of the geological and geophysical constraints available for the western Alpine area. In order to evaluate the impact of the exhumed mantle wedge, imaged at depths as shallow as 10–12 km beneath the Dora‐Maira by recent tomography models (Solarino et al, 2018; Zhao et al, 2020), we have considered events in the 0–12 and 12–30 km depth ranges separately. We have also plotted separately the fault plane solutions for events of magnitude M l < 4.0 and M l > 4.0, as the latter are potentially more representative of the reactivation of major faults described in section 2.2.…”

“…It shows relatively minor seismicity (Chiarabba et al, 2005; Giardini et al, 1999) due to slow convergence between tectonic plates (Sánchez et al, 2018; Serpelloni et al, 2016). However, it is a key area to understand how deformation is partitioned at the transition between subduction zones with opposite polarities, as surface geology has been investigated for more than a century, seismicity has been continuously recorded since the 1960s (Amato et al, 1997; Eva et al, 2010), and the deep tectonic structure is increasingly well‐known thanks to recent geophysical investigations (e.g., Kästle et al, 2018; Salimbeni et al, 2018; Solarino et al, 2018; Zhao et al, 2015, 2020). Several kinematic models have been proposed to explain the postmetamorphic evolution of the Alpine region, either invoking horizontal indentation (e.g., Laubscher, 1988; Schmid et al, 2017; Tapponnier, 1977), microplate rotation (e.g., Ménard, 1988; Vialon, 1990), or synorogenic to postorogenic gravitational collapse (Eva et al, 1997; Eva & Solarino, 1998; Sue et al, 1999, 2007).…”

WITHDRAWN: Can Traditional Chinese Medicine provide insights into controlling the COVID-19 pandemic: Serpentinization-induced lithospheric long-wavelength magnetic anomalies in Proterozoic bedrocks in a weakened geomagnetic field mediate the aberrant transformation of biogenic molecules in COVID-19 via magnetic catalysis

“…A severe, locally-restricted COVID-19 outbreak was first recorded on the Yangtze craton (in Wuhan and surrounding cities) ( Peng et al, 2012 ) in the eastern portion of the Eurasian plate. The subsequent severe outbreaks spread westerly on the Eurasian plate along the Greater Tethyan Eurasian orogenic belt (the Alpine-Himalayan orogenic belt ( Guillot et al, 2015 ; Giampouras et al, 2019 ; Zhao et al, 2020 ; Hirth and Guillot, 2013 ; Reynard, 2013 ; Debret et al, 2013 )) and subsequently along the Appalachian-Ouachita orogenic belt on the North American plate and to the South American tectonic plate. Severe COVID-19 outbreaks predominately co-localize with the troughs of the lithospheric LWMAs ( Idoko et al, 2019 ) in tectonic plates with Proterozoic cratons, which are basin regions with population centers ( Fig.…”