A north-south seismic profile across the Caledonian Suture zone in Ireland

Lowe, C; Jacob, A. W. B.

doi:10.1016/0040-1951(89)90224-2

Cited by 66 publications

(67 citation statements)

References 16 publications

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“…The result 250 of this combination reveals that the minimum crustal thickness along P03 is ~5 km, corresponding to 251 a βc of ~6 (at ~120 km of profile distance; Fig. 4b), assuming an original crustal thickness of ~30 km 252 SW of Ireland [Lowe & Jacob, 1989;O'Reilly et al, 2010]. This amount of extension is well within 253 the range at which crustal embrittlement is expected [i.e.…”

Section: Results 179mentioning

confidence: 88%

Crustal strain-dependent serpentinisation in the Porcupine Basin, offshore Ireland

Prada

Watremez

Chen

et al. 2017

Earth and Planetary Science Letters

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15Mantle hydration (serpentinisation) at magma-poor rifted margins is thought to play a key role in 16 controlling the kinematics of low-angle faults and thus, hyperextension and crustal breakup. 17However, because geophysical data principally provide observations of the final structure of a margin, 18 little is known about the evolution of serpentinisation and how this governs tectonics during 19 hyperextension. Here we present new observational evidence on how crustal strain-dependent 20 serpentinisation influences hyperextension from rifting to possible crustal breakup along the axis of 21 the Porcupine Basin, offshore Ireland. We present three new P-wave seismic velocity models that 22show the seismic structure of the uppermost lithosphere and the geometry of the Moho across and 23 along the basin axis. We use neighbouring seismic reflection lines to our tomographic models to 24 estimate crustal stretching (βc) of ~2.5 in the north at 52.5 o N and > 10 in the south at 51.7 o N. These 25 values suggest that no crustal embrittlement occurred in the northernmost region, and that rifting may 26 have progressed to crustal breakup in the southern part of the study area. We observed a decrease in 27 mantle velocities across the basin axis from east to west. These variations occur in a region where βc 28 is within the range at which crustal embrittlement and serpentinisation are possible (βc 3-4). Across 29 the basin axis, the lowest seismic velocity in the mantle spatially coincides with the maximum amount 30 of crustal faulting, indicating fault-controlled mantle hydration. Mantle velocities also suggest that 31 2 the degree of serpentinisation, together with the amount of crustal faulting, increases southwards 32 along the basin axis. Seismic reflection lines show a major detachment fault surface that grows 33 southwards along the basin axis and is only visible where the inferred degree of serpentinisation is > 34 15 %. This observation is consistent with laboratory measurements that show that at this degree of 35 serpentinisation, mantle rocks are sufficiently weak to allow low-angle normal faulting. Based on 36 these results, we propose two alternative formation models for the Porcupine Basin. The first involves 37 a northward propagation of the hyperextension processes, while the second model suggests higher 38 extension rates in the centre of the basin than in the north. Both scenarios postulate that the amount 39 of crustal strain determines the extent and degree of serpentinisation, which eventually controls the 40 development of detachments faults with advanced stretching. 41 42 3

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Section: Results 179mentioning

confidence: 88%

Crustal strain-dependent serpentinisation in the Porcupine Basin, offshore Ireland

Prada

Watremez

Chen

et al. 2017

Earth and Planetary Science Letters

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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).…”

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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“…Hauser et al (1995) and O'Reilly et al (1996) observed that the slow stretching rates necessary to explain hyperextension without magmatism were most easily explained by a differential stretching model in which the upper and middle crust were more extended than the lower crust and upper mantle. This interpretation was supported by a comparison between the three-layer velocity model for adjacent, unstretched crust (Jacob et al 1985;Lowe & Jacob 1989) and the velocity structure observed beneath the central part of the basin. …”

Section: Southern Rockall Basinmentioning

confidence: 67%

“…A reference value of 30 km is estimated around Britain and Ireland on the basis of observed crustal thicknesses in areas where topography lies close to sea level and Mesozoic basins are absent (e.g. Jacob et al 1985;Lowe & Jacob 1989). In the Norwegian sector, larger crustal thicknesses have been detected in the coastal region (e.g.…”

Section: Southern Rockall Hatton and Porcupine Basinsmentioning

confidence: 99%

Controls on the location of compressional deformation on the NW European margin

Kimbell

Stewart

Gradmann

et al. 2016

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The distribution of Cenozoic compressional structures along the NW European margin has been compared with maps of the thickness of the crystalline crust derived from a compilation of seismic refraction interpretations and gravity modelling, and with the distribution of high-velocity lower crust and/or partially serpentinized upper mantle detected by seismic experiments. Only a subset of the mapped compressional structures coincide with areas susceptible to lithospheric weakening as a result of crustal hyperextension and partial serpentinization of the upper mantle. Notably, partially serpentinized upper mantle is well documented beneath the central part of the southern Rockall Basin, but compressional features are sparse in that area. Where compressional structures have formed but the upper mantle is not serpentinized, simple rheological modelling suggests an alternative weakening mechanism involving ductile lower crust and lithospheric decoupling. The presence of pre-existing weak zones (associated with the properties of the gouge and overpressure in fault zones) and local stress magnitude and orientation are important contributing factors.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.

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A north-south seismic profile across the Caledonian Suture zone in Ireland

Cited by 66 publications

References 16 publications

Crustal strain-dependent serpentinisation in the Porcupine Basin, offshore Ireland

Crustal strain-dependent serpentinisation in the Porcupine Basin, offshore Ireland

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

Controls on the location of compressional deformation on the NW European margin

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