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Third North Atlantic Workshop

Conveners: Gillian Foulger, Christian Schiffer & Alex Peace

First North Atlantic Workshop, 19-21 September, 2016

Second North Atlantic Workshop, 18-20 April, 2017

Frameworks for Earth-Science Reviews papers

 

Status of Earth-Science Reviews papers in preparation

updated: 20th Aug, 2018

No.
Placeholder title
Authors
Summary
Target timescale
1
A new paradigm for the NE Atlantic Ocean
Gillian R. Foulger, Tony Doré, C. Henry Emeleus, Laurent Geoffroy, Laurent Gernigon, Ahmad Ghassemi, Richard Hey, Robert E. Holdsworth, Malcolm Hole, Ármann Höskuldsson, Bruce Julian, Nick Kusznir, Fernando Martinez, James H. Natland, Alex Peace, Kenni Petersen, Oliver Sanford, Christian Schiffer, Randell Stephenson and Martyn Stoker +…

This paper will contain:

  1. Summary of the opening of the Labrador Sea/Davis Strait/Baffin Bay and NE Atlantic regions, the volcanic passive margins, Faroe-Shetland basin and crustal structure of the GIFR;
  2. Presentation of new model of evolution of the GIFR based on idea that Icelandic-type lower crust is magma-inflated mid- and lower continental crust, possibly with some serpentinised mantle;
  3. Numerical models including crack-propagation model (Ahmad) and thermo-mechanical model (Kenni);
  4. Geochemistry;
  5. Discussion, development of implications & conclusions.

Aug 30: Draft to co-authors

Sept 15: submission

2
3
Crustal fragmentation, magmatism, and the diachronous breakup of the Norwegian-Greenland Sea
Gernigon, L.; Franke, D.; Geoffroy, L.; Schiffer, C.; Foulger, G.; Stoker, M, +…
The Norwegian-Greenland Sea contains diverse tectonic regimes including microcontinents and conjugate volcanic passive margins ‘bridged’ to the south by the Greenland-Iceland-Faroe Ridge. The long period of rifting, structural style, and major breakup magmatism that included formation of seaward dipping reflectors distinguish the volcanic passive margins from non-volcanic margins. Thick sedimentary basin developed during drastic thinning of the continental crust associated with progressive exhumation of inherited, high-grade metamorphic rocks likely preserved beneath the seaward dipping reflectors. Breakup-related intrusions may localise deformation and guide the final axis of breakup along distal regions affected by pre-magmatic Late Cretaceous- Paelocene extension phase. Despite the common assumption that Norwegian-Greenland Sea breakup is essentially instantaneous, aeromagnetic data suggest it was diachronic, initiating isolated, segmented spreading centres. The early spreading system later developed and grew into atypical propagating systems that extended the time of breakup(s) and brought about step-by-step rupture of the lithosphere. The magnetic data also reveal an important mid-Eocene kinematic event at around magnetic chron C21r (46 Ma). This event coincides with the onset of diking, an increase in rifting and possibly oceanic accretion between the Jan Mayen microplate complex and the East Greenland margin. Complex rift reorganisation, deep inherited structures and magmatism likely influenced the final dislocation of the Jan Mayen microplate complex from Greenland in the Late Oligocene.

June 1: Final draft circulated to co-authors

end Aug: Definitely will be submitted by this time

4
Late Cretaceous-Cenozoic intraplate basin inversion in the North Atlantic-western Alpine-Tethys realm
Randell Stephenson, Scott Jess, Søren Nielsen, Alexander Peace & Christian Schiffer +…
Intraplate “basin inversion” occurs when normal faults developed during initial extensional basin formation are reactivated as reverse faults during post-rift periods of tectonic compression. Basin inversion is a good marker of (“far-field”) tectonic stress regime changes that are linked to plate boundary reorganisations. This premise is well-established in the literature: how Late Cretaceous- Palaeocene inversion of sedimentary basins has occurred in north-central Europe, for example, can be linked explicitly with the timing and style of plate break-up in the North Atlantic and its interactions with the Alpine-Tethys plate boundary of southern Europe. Periods of intraplate tectonics, marked primarily by structural inversion in initially extensional sedimentary basins in the North Atlantic realm, have been compiled from published literature. The focus is on the Late Cretaceous-Palaeocene, the Eocene and the Miocene. The aim is to establish a basis for investigating further if/how regional intraplate deformation/inversion in the North Atlantic-western Alpine-Tethys realm may be linked to rapid plate kinematic changes in this tectonic realm and, in turn, to plate tectonic boundary reorganisations taking place on a global scale.
August 25: draft for circulation
5

How hot was the mantle beneath the NAIP?

Malcolm Hole, Jim Natland +…
  1. There are consistencies in the data for Baffin Island and Disko Island lavas that suggest derivation from mantle of higher than ambient TP and probably up to 1500°C.  The inability to produce anomalously high TP estimates for these lavas by olivine accumulation in a melt formed at ambient TP, coupled with TSp estimates and TOl-Sp up to 1450°C implies a mantle temperature at least 150°C greater than ambient mantle.  
  2. The clear continuum of data that relates the Vaigat Formation picrites and overlying Maligat Formation lavas also suggest that the magmatic system developed at elevated TP.  The only detractors from this are a small number of glass analyses (9 in total) from Baffin Island that are suggesting of crystallization along a low temperature L+Ol+Pl cotectic.   However, these might also represent end-stage melts formed at shallow levels in the melting column.
  3. For BPIP picrites there are inconsistencies between TOl-Sp and model Tsp, the former giving temperatures that are ~100°C hotter than would be expected from spinel alone.   Melt inclusions in olivine in lavas from MPLF picrites suggest TP~1480°C (Hole & Millett 2016) and we consider this the upper TP estimate for the BPIP.
  4. For Iceland the situation is less clear.  PRIMELT3 solutions for Iceland are suspect, and there is little evidence from TSp or TOl-Sp for temperatures approaching those determined for picrites from the West of Greenland.  Consequently, there is little compelling evidence for TP>1450°C beneath modern Iceland assuming melting of dry peridotite.
  5. Melting of a mixed pyroxenite-peridotite source at TP~1480°C cannot account for the geophysical estimates of crustal thickness beneath parts of eastern and central Iceland. Crustal thicknesses of up to 40 km most likely requires Iceland to be underlain by about 20 km of older crust.
  6. Evidence from H2O contents of undegassed pillow glasses on Iceland suggests that their source might have been damp, a similar situation to that at the Azores.
  7. If it is accepted that the maximum thickness of melt at Iceland rift zones is ~20km then all of the Iceland melt layer could have been formed by damp melting of mantle peridotite at TP ≤1450°C.  For 15 km of crust, this would drop to TP <1400°C.
  8. Adding pyroxenite to a damp melt would not change significantly the TP needed for 15 or 20 km of crust because the solidi of the most likely compositions of pyroxenite in the source have similar slopes in P-T space to the damp solidus.  It is not, therefore possible to separate damp melting from that produced by melting of a hybrid pyroxenite-peridotite source.
The widespread early magmatism in the NAIP may be related to a short-lived pulse of hot mantle, but there is little evidence to suggest that this lasted more than two or three million years and up to ~55 Ma. After this time there is no evidence of mantle at a with TP more than 100°C above ambient.

submitted

6

The role of tectonic inheritance in the evolution of the North Atlantic

Christian Schiffer, A.G. Doré, G.R. Foulger, Dieter Franke, Laurent Geoffroy, Laurent Gernigon, Bob Holdsworth, Nick Kusznir, Erik Lundin, Ken McCaffrey, Alex Peace, Kenni Petersen, Randell Stephenson, Martyn Stoker, Kim Welford +…
The North Atlantic (defined here as extending from the Iberia-Newfoundland conjugates to the north Norway-Greenland-Svalbard margins) is often regarded as a classic case of inheritance and as a model for the Wilson-cycle concept. This paper examines tectonic inheritance in the North Atlantic in two ways; 1) as a function of reactivation at different scales, ranging from lithospheric to local, and 2) in terms of development of the ocean and its margins through time.

Sept 30: submission date

7

Reykjanes Ridge Evolution by plate kinematics, propagating small-scale mantle convection, and a regional thermo-chemical mantle anomaly

Fernando Martinez & Richard N. Hey

Draft Abstract

  1. The Reykjanes Ridge was originally one arm of a RRR triple junction that together accommodated opening between North America, Greenland and Eurasia.
  2. It initiated as a linear spreading center over a regional mantle thermo-chemical anomaly with a strong gradient in properties leading to maximum melting beneath Iceland and grading to near normal crustal thickness south of the Bight FZ.
  3. The linear ridge configuration and mantle gradient induced propagation of small-scale mantle convective cells along the Reykjanes Ridge axis forming the ridge flank V-shaped crustal ridges.
  4. When the Greenland-North America plate boundary failed joining Greenland to North America, an abrupt 30° change in opening direction occurred across the Reykjanes Ridge as it became the new North America-Eurasia plate boundary.
  5. The Reykjanes Ridge abruptly became segmented into an orthogonal ridge-transform stair-step pattern oriented in the new spreading direction.  The offset of ridge segments led to the segmented crustal accretion pattern of this phase of spreading.
  6. The ridge segments promptly began to diachronously reorganize from north to south, eliminating the just-formed segmentation to re-establish the original linear configuration of the plate boundary.
  7. This was likely driven by the persistence of the deep, low viscosity and voluminous asthenospheric melting regime which remained in a linear configuration following the abrupt fragmentation of the shallow lithospheric plate boundary to a stair-step pattern. 
  8. As the plate boundary became linear, but now obliquely spreading, V-shaped crustal ridges formed again as a consequence of the axially-propagating small-scale convective cells.
  9. The regional mantle thermo-chemical anomaly may have resulted from the slow advection deep mantle, as suggested in some seismic tomographic images, or it may have formed in the shallow mantle from ancient subduction events.
  10. The regional mantle thermo-chemical anomaly may have existed passively below its solidus depth beneath the thick North American continental lithosphere long before breakup.
  11. On continental rifting, this mantle anomaly would have been advected above its solidus, initiating melting and small-scale mantle advection to produce voluminous volcanism.
  12. Propagation of small-scale convective cells along the rift and subsequent spreading ridge was driven by gradients in mantle properties (as inferred from the current axial depth profile and residual basement depth anomalies) and led to the linear configuration of the breakup and initial Reykjanes Ridge.
  13. The model explains the initial distribution of voluminous volcanism following breakup, the pattern of residual crustal thickness anomalies on the ridge flanks and the current axial depth and crustal thickness variation along the Reykjanes Ridge without a mantle plume.
on target
8
The anomalous North Atlantic Region: Anomalous topography, crust and lithospheric mantle
Irina Artemieva, Hans Thybo & Alexey Shulgin
paper in preparation may or may not make the ESR special section
9

Pangea dispersal and large igneous provinces - in search of causative mechanisms

Alexander Peace, Dieter Franke, Tony Doré, Gillian Foulger, Nick Kusznir, Gregory McHone, Jordan Phethean, Sergio Rocchi, Christan Schiffer & Michael Schnabel +…
This paper reviews the dispersal of the Pangaea and Gondwana supercontinents and the relationship with large igneous provinces. The main finding of this work is that there exists a disparity between the initiation of rifting, breakup and the locations of large igneous provinces.
Aug 30: something to circulate around the wider North Atlantic meeting group
10
Nick Kusznir +…
updated details coming shortly
end Oct: submission
11

Davis Strait Paleocene Picrites: Products of a Plume or Plates?

D. Barrie Clarke & Erin K. Beutel

The Davis Strait picrites represent a unique petrogenetic and structural event in the Early Tertiary separation of Greenland from North America. We show that the intersection of the developing Labrador Sea-Baffin Bay rift with thickened lithosphere in central Greenland created the appropriate plate-tectonic conditions for extensive decompression melting in a depleted sub-continental lithospheric mantle. No mantle plume was involved

Submitted
12
Mantle density and temperature structure of the North Atlantic ocean, Europe, and the Mediterranean
Alexey Shulgin & Irina Artemieva
paper in preparation may or may not make the ESR special section
 

 

Drafts/frameworks of papers

  1. General overview (Leader: Gillian Foulger, everyone a co-author) File 1

  2. What is the nature of Iceland? Does it contain a continental sliver? Structure, gravity, kinematics. (Leader: Ármann Höskuldsson & Gillian Foulger)

  3. Diachronic breakup and spreading development of the North Atlantic (Leaders: Laurent x 2) File1

  4. A review of Late Cretaceous-Cenozoic intraplate basin inversion in the North Atlantic-western Tethys realm (Leader: Randell Stephenson)
    Post-meeting paper plan files: FileA

  5. North Atlantic thermochronology/vertical motions  (Leader: Søren Nielsen)

  6. Mantle potential temperature and the role of pyroxenite and dry and damp peridotite in magmatism in the NAIP (Leader: Malcolm Hole) File1 File2 File3

  7. Inheritance. (Leaders: Tony Doré & Christian Schiffer) File1

  8. Reykjanes Ridge (Leader: Fernando Martinez) File1 File2

  9. Structure from top to bottom, crust, mantle. (Leaders: Hans Thybo & Irina Artemieva)

  10. Dispersal of Pangea and its relationship with large igneous provinces (Leaders: Alex Peace & Dieter Franke) File1 File2 File3 File4
    Post-meeting paper plan files: FileA FileB

  11. Comparisons/extensions to other regions (Leader: Nick Kusznir) File1 File2

  12. Davis Strait Palaeocene Picrites: Products of a Plume or Plates? (D. Barrie Clarke & Erin K. Beutel) File1

 

Upcoming target dates

31st March, 2018: Submission deadline to Earth-Science Reviews

 

Structure of the meeting

Our third meeting will focus on:

  • key questions and ideas that have emerged in discussion since the last workshop, and
  • integrating the papers in preparation for ESR.

Please email Christian Schiffer or Gillian Foulger with suggestions, ideas and updates.

 

last updated 17th May, 2018

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