The geometry of the Iapetus Suture Zone in central Ireland deduced from a magnetotelluric study

Rao, C. K.; Jones, Alan G.; Moorkamp, Max

doi:10.1016/j.pepi.2007.01.008

Cited by 27 publications

(27 citation statements)

References 25 publications

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“…Magnetotelluric data have been demonstrated to be very useful in revealing the shape of modern subduction zone [ Jones , ; Soyer and Unsworth , ; Jödicke et al ., ; Brasse et al ., ; Ichiki et al ., ; Wannamaker et al ., ; Matsuno et al ., ; Worzewski et al ., ; Burd et al ., ], as well as fossil subduction system along with frozen‐in structure [ Rao et al ., ; Chen et al ., ; Thiel et al ., ; Padilha et al ., ; Nieuwenhuis et al ., ; Yang et al ., ]. There are some common electrically conductive features for both the modern and fossil subduction zones, e.g., a resistive oceanic plate [ Constable and Cox , ] underlying a conductive oceanic upper mantle and several conductive zones in the overriding crust, ranging from the fore‐arc to the volcanic arc [ Jones , ; Ichiki et al ., ; Wannamaker et al ., ] and the back‐arc regions with well‐developed extension faults or shear zones triggered by the subduction.…”

Section: Introductionmentioning

confidence: 99%

Magnetotelluric imaging of a fossil paleozoic intraoceanic subduction zone in western Junggar, NW China

Yang

Sheng

et al. 2016

JGR Solid Earth

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The fate of subducted oceanic slabs can provide important clues to plate reconstruction through Earth history. Since oceanic slabs in continental collision zones are typically not well preserved, ancient subduction zones have rarely been imaged by geophysical techniques. Here we present an exception from the Darbut belt in the Junggar accretionary collage in the southern Altaids of Asia. We deployed a 182 km long magnetotelluric (MT) profile including 60 broadband sounding sites across the belt. Quality off‐diagonal impedances were inverted by a three‐dimensional scheme to image resistivities beneath the profile. The resistivity model along with MT impedance phase ellipses and induction vectors were tested and interpreted in detail. Combining geological and geophysical observations, mineral physical experiment, and geodynamic modeling results, the MT transect suggests a fossil intraoceanic subduction zone during the Late Paleozoic in the western Junggar that has been well preserved due to lack of significant subsequent tecto‐thermal events.

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Section: Introductionmentioning

confidence: 99%

Magnetotelluric imaging of a fossil paleozoic intraoceanic subduction zone in western Junggar, NW China

Yang

Sheng

et al. 2016

JGR Solid Earth

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“…With the availability of state-of-the-art MT equipment covering a wide frequency range (proxy for depth), together with modern and improved methods and techniques for processing, analysis, modelling and inversion, we conducted MT measurements across the ISZ during the years [2004][2005][2006]. Using the broad-band MT (BBMT) data from one NW-SE profile located in eastern Ireland, Rao et al (2007) identified a U-shaped highly conductive zone (vertically integrated conductance of 2000-7000 S) in the central part of eastern Ireland (from MT stations 105 to 110; Fig. 1) that was interpreted in terms of metamorphosed graphitic sediments within the ISZ.…”

mentioning

confidence: 99%

Implications for the lithospheric geometry of the Iapetus suture beneath Ireland based on electrical resistivity models from deep-probing magnetotellurics

Rao¹,

Jones²,

Moorkamp³

et al. 2014

Geophysical Journal International

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S U M M A R YBroad-band and long period magnetotelluric (MT) data were acquired at 39 stations along five NNW-SSE profiles crossing the Iapetus Suture Zone (ISZ) in Ireland. Regional strike analyses indicate that the vast majority of the MT data is consistent with an assumption of a 2-D geoelectric strike direction. Strike is N52 • E for the three easternmost profiles and N75 • E for the two westernmost profiles; these directions correlate well with the observed predominant geological strike of the study region. 2-D inversions of the galvanic distortion-corrected TE and TM mode data from each profile are shown and discussed. As mapped geological variations between the neighbouring profiles suggest a heterogeneous subsurface, it is important to verify the robustness of the presence and geometries of prominent conductivity anomalies by employing 3-D forward and inverse modelling. A high conductivity layer (resistivity of 1-10 m), found at middle to lower crustal depths and presumed to be indicative of metamorphosed graphitic sediments rich in sulphides deposited during the convergence of the Laurentian and Avalonian continents, essentially constitutes the electrical signature of the ISZ. Shallow conductors observed are probably due to black shales that were widely deposited within the sedimentary accretionary wedge during Ordovician time. We interpret the moderately low resistivity at shallow depths from west to east across Ireland as indicative of an increase in maturity of the black shales in the easterly direction. From our conductivity models the southern extent of the ISZ is inferred to lie between the Navan Silvermines Fault and the Navan Tipperary Line, and shows clear resistivity contrast along all the profiles at the southern MT stations. The change in resistivity deduced from the 2-D models is spatially related to the composition of Lower Palaeozoic Ordovician, Silurian, Devonian and Carboniferous rocks. At upper mantle depths of about 60 km, a high conductivity block below the central MT stations is found to lie within the accretionary wedge of the Iapetus suture, and the location of the conductive anomaly corroborates reasonably well with the inferred spreading head of the putative Iceland plume-related magmatic intrusion. The low resistivity upper crust beneath the ISZ is indeed rich in Ordovician rocks with black shale content in the eastern as well as the central part; the western part is largely underlain by a highly resistive block of volcanic and metamorphosed rocks forming crystalline basement.

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“…4). In addition to these mapped localities, it has been proposed that pyrrhotite in black shale is responsible for high conductivity anomalies in central Ireland (Rao et al 2007). Furthermore, the Navan ore body is also suspected to contain pyrrhotite.…”

Section: Distribution Of Pyrrhotite In Irelandmentioning

confidence: 99%

Implications of Pyrite Oxidation for Engineering Works

Hawkins¹,

John²

2014

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The geometry of the Iapetus Suture Zone in central Ireland deduced from a magnetotelluric study

Cited by 27 publications

References 25 publications

Magnetotelluric imaging of a fossil paleozoic intraoceanic subduction zone in western Junggar, NW China

Magnetotelluric imaging of a fossil paleozoic intraoceanic subduction zone in western Junggar, NW China

Implications for the lithospheric geometry of the Iapetus suture beneath Ireland based on electrical resistivity models from deep-probing magnetotellurics

Implications of Pyrite Oxidation for Engineering Works

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