A seismic discontinuity in the lithosphere

Heterogeneity of the uppermost mantle beneath Russian Eurasia from the ultra‐long‐range profile quartz

“…The possible explanations are a gradational compositional variation, a phase change, and anisotropy. Within this depth range, garnet should appears in peridotitc [Hales, 1969;Wyllie, 1995] leading to an increase in velocity. Likewise, recrystallization to form jadeitc and garnet in an eclogite, leading to a more piclogitic composition [Dufj• and Anderson, 1989], would also form a velocity gradient.…”

Mantle discontinuity structure from midpoint stacks of converted P to S waves across the Yellowstone hotspot track

“…olivine phase transformation and/or transformation of garnet and pyroxene to calcic-perovskite [Revenaugh and Jordan, 1991b]. Average magnitudes of the olivine Clapeyron slopes (3 MPa/øC [Bina and Helffrich, 1994]) predict that 20 km of equilibrium dis-ing: partial melting [Anderson and Sammis, 1970;Hales, 1991], discontinuities in rock fabric [Leven et al, 1981; Gaherty and Jordan, 1995], spinel to garnet phase transition [Hales, 1969], or chemical layering of eclogitic and peridotitic rocks [Anderson, 1989]. Below the 660-km discontinuity, discontinuities have been reported at depths of 720 km [Revenaugh and Jordan, 1991b], 920 km [Kawakatsu and Niu, 1994;Stunffet al, 1995], and 1200 km [Stunff et al, 1995].…”

Lithospheric and upper mantle structure of the Indian Shield, from teleseismic receiver functions

“…Sophisticated stacking techniques have enabled investigators to gain new knowledge about global 1-D as well as regional 3-D structure. Of particular interest is the structure of the upper mantle and the topography of its most prominent discontinuities, as well as the eventual existence of 0Adi-tional, though possibly not global interfaces within the mantle [Hales, 1969;Shearer, 1990;Bastack, 1996]. In this paper we investigate the stratigraphy of the crust and, for the first time, upper mantle beneath the central Indian Shield using teleseismic P waves recorded at GEOSCOPE station Hyderabad (HYB), the only FDSN station currently operating in India.…”