The ‘pargasosphere’ hypothesis: Looking at global plate tectonics from a new perspective

Multi‐Stage Evolution of the South Australian Craton: Petrological Constraints on the Architecture, Lithology, and Geochemistry of the Lithospheric Mantle

“…The accumulation of seismically slow (hydrous) minerals such as amphibole (pargasite) has been a favored explanation for global MLDs (Aulbach et al, 2017;Kovács et al, 2017;Rader et al, 2015;Selway et al, 2015). This hypothesis has petrological support because, (a) the maximum P of the stability field of amphibole (pargasite) in the upper mantle is 3 GPa, broadly corresponding to the depth range of most mid-lithosphere discontinuities (80-120 km) (Kovács et al, 2017(Kovács et al, , 2021Niida & Green, 1999;Rader et al, 2015), and (b) amphibole-forming reactions are known to take place beneath the thickened, metasomatized roots of cratons where most mid-lithosphere discontinuities are observed (Aulbach et al, 2017;Niida and Green., 1999). The deeper geochemical MLDs observed beneath the South Australian Craton (130-160 km) are inconsistent with the limited stability range of pargasite in depleted mantle peridotite (Niida & Green, 1999), but may be related to pargasite occurring in highly fertile (or refertilized) peridotite, where pargasite has a pressure stability limit exceeding 35 kbar (Mandler & Grove, 2016).…”

Craton Destruction Induced by Drastic Drops in Lithospheric Mantle Viscosity

“…Moreover, a mid‐lithospheric discontinuity (generally at depths between ∼80 and ∼100 km) has been proposed in the NCC, which shows low seismic velocities and could be interpreted by a “pargasosphere” hypothesis (Kovács et al., 2021; Z. S. Wang et al., 2017, 2018). The disturbance of such prominent weakness zones may decouple the lithosphere, along which the lower part of the cratonic roots can be removed (Kovács et al., 2021; Z. S. Wang et al., 2018), enhancing and accelerating craton destruction.…”

“…Strongly weakened cratonic roots are unable to resist entrainment by the surrounding mantle flow and are susceptible to modification and disturbance by other mechanisms, such as redox melting and/or delamination (Foley, 2008, 2011; S. Gao et al., 2002; Lee et al., 2011; Y. Wang et al., 2015; Wu et al., 2019). Moreover, a mid‐lithospheric discontinuity (generally at depths between ∼80 and ∼100 km) has been proposed in the NCC, which shows low seismic velocities and could be interpreted by a “pargasosphere” hypothesis (Kovács et al., 2021; Z. S. Wang et al., 2017, 2018). The disturbance of such prominent weakness zones may decouple the lithosphere, along which the lower part of the cratonic roots can be removed (Kovács et al., 2021; Z. S. Wang et al., 2018), enhancing and accelerating craton destruction.…”

“…S. Wang et al, , 2018. The disturbance of such prominent weakness zones may decouple the lithosphere, along which the lower part of the cratonic roots can be removed (Kovács et al, 2021;Z. S. Wang et al, 2018), enhancing and accelerating craton destruction.…”

Petrogenesis of Lava from Christmas Island, Northeast Indian Ocean: Implications for the Nature of Recycled Components in Non-Plume Intraplate Settings

“…Petit-spot volcanism is believed to be the result of plate-flexure allowing the direct sampling of an underlying asthenosphere melt lying at the lithosphere-asthenosphere boundary (LAB) [117]. Thus petit-spot volcanism gives strong support for the long-standing idea that the LAB is defined and marked by the presence of a melt phase [116,[118][119][120][121].…”