Seismic reflections from the mantle represent relict subduction zones within the continental lithosphere

Warner, Michael; Morgan, J. V.; Barton, P. J.; Morgan, Peter; Price, Claire; Jones, K.A.

doi:10.1130/0091-7613(1996)024<0039:srftmr>2.3.co;2

Cited by 104 publications

(55 citation statements)

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“…In two places in northern Europe, spectacular Caledonian structures have been imaged in the upper mantle (Warner et al, 1996;MONA LISA Working Group, 1997). A significant wide-angle observation of variation in seismic velocity across the dipping mantle reflectors was observed at the MONA LISA profiles, as well as indication for anisotropy with the fast axis along a dipping slab (Abramovitz and Thybo, 2000).…”

Section: Accepted Manuscriptmentioning

confidence: 98%

Geophysical constraints on geodynamic processes at convergent margins: A global perspective

2016

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Section: Accepted Manuscriptmentioning

confidence: 98%

Geophysical constraints on geodynamic processes at convergent margins: A global perspective

2016

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“…Deep seismic experiments, summarized by Landes et al (2005), record variations in Moho depth and anomalously low middle and lower crustal Pwave velocities (Lowe & Jacob, 1989), which may reflect a change in basement composition. Deep seismic reflection studies have also revealed lithospheric mantle reflectors, which are thought to represent fossil, possibly Palaeoproterozoic, subduction zones (Warner et al 1996;Snyder, England & McBride, 1997). These structures led Long & McConnell (1999) to suggest that Archaean crust may be buried at depth in NW Ireland.…”

Section: A Laurentian Basementmentioning

confidence: 99%

Hidden Archaean and Palaeoproterozoic crust in NW Ireland? Evidence from zircon Hf isotopic data from granitoid intrusions

et al. 2009

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-The presence of major crystalline basement provinces at depth in NW Ireland is inferred from in situ Hf isotope analysis of zircons from granitoid rocks that cut structurally overlying metasedimentary rocks. Granitoids in two of these units, the Slishwood Division and the Tyrone Central Inlier, contain complex zircons with core and rim structures. In both cases, cores have average εHf values that differ from the average εHf values of the rims at 470 Ma (the time of granitoid intrusion). The Hf data and similarity in U-Pb age between the inherited cores and detrital zircons from the host metasedimentary rocks suggests local contamination during intrusion rather than transport of the grains from the source region at depth. Rims from the Slishwood Division intrusions have average εHf 470 values of −7.7, consistent with a derivation from juvenile Palaeoproterozoic crust, such as the Annagh Gneiss Complex or Rhinns Complex of NW Ireland, implying that the deep crust underlying the Slishwood Division is made of similar material. Rims from the Tyrone Central Inlier have extremely negative εHf 470 values of approximately −39. This isotopic signature requires an Archaean source, suggesting rocks similar to the Lewisian Complex of Scotland, or sediment derived wholly from it, occurs at depth in NW Ireland.

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“…Their detection is therefore fundamental in the understanding of the earth's dynamic. In particular, the pres-ence of eclogite bodies within the continental lithosphere could explain high velocity patches detected in seismic tomography models or bright seismic reflectors on deep seismic reflection profiles (Butler, 1986;Laubscher, 1990;Nicolas et al, 1990;Austrheim, 1991;Warner et al, 1996). Laboratory measurements of P-and S-wave velocities (e.g.…”

Section: Introductionmentioning

confidence: 99%

EBSD-measured lattice-preferred orientations and seismic properties of eclogites

Bascou¹,

Barruol²,

Vauchez³

et al. 2001

Tectonophysics

132

102

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measured lattice-preferred orientations and seismic properties of eclogites. Tectonophysics, Elsevier, 2001, 342, pp.61 -80. <10.1016/S0040-1951 AbstractWe investigated the deformation mechanisms and the seismic properties of 10 eclogite samples from different localities (Alps, Norway, Mali and eastern China) through the analysis of their microstructures and lattice-preferred orientations (LPO). These samples are representative of various types and intensity of deformation under eclogitic metamorphic conditions. Omphacite and garnet LPO were determined from electron backscatter diffraction (EBSD) technique. Garnet appears to be almost randomly oriented whereas omphacite develops strong LPO, characterized by the [001]-axes concentrated sub-parallel to the lineation, and the (010)-poles concentrated sub-perpendicular to the foliation. In order to analyze the deformation mechanisms that produced such omphacite LPO, we compare our observations to LPO simulated by viscoplastic selfconsistent numerical models. A good fit to the measured LPO is obtained for models in which the dominant slip systems are 1/2h110i{110}, [001] {110} and [001] (100). Dominant activation of these slip systems is in agreement with TEM studies of naturally deformed omphacite. Seismic properties of eclogite are calculated by combining the measured LPO and the single crystal elastic constants of omphacite and garnet. Although eclogite seismic anisotropies are very weak (less than 3% for both P-and S-wave), they are generally characterized by a maximum P-wave velocity sub-parallel to the lineation and by a minimum velocity approximately normal to foliation. The mean P-and S-wave velocities are high (respectively, 8.6 and 4.9 km/s). The S-wave anisotropy pattern displays complex relationships with the structural frame but the fast polarization plane generally tends to be parallel to the foliation. Calculated reflection coefficients show that an eclogite/crust interface is generally a good reflector (Rc > 0.1), whereas an eclogite body embedded in the upper mantle would be hardly detectable. D

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Seismic reflections from the mantle represent relict subduction zones within the continental lithosphere

Cited by 104 publications

References 0 publications

Geophysical constraints on geodynamic processes at convergent margins: A global perspective

Geophysical constraints on geodynamic processes at convergent margins: A global perspective

Hidden Archaean and Palaeoproterozoic crust in NW Ireland? Evidence from zircon Hf isotopic data from granitoid intrusions

EBSD-measured lattice-preferred orientations and seismic properties of eclogites

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