The Ocean – Continent Transition Zones Along the Appalachian – Caledonian Margin of Laurentia: Examples of Large-Scale Hyperextension During the Opening of the Iapetus Ocean

Chew, David; Staal, Cees R. van

doi:10.12789/geocanj.2014.41.040

Cited by 43 publications

(29 citation statements)

References 92 publications

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“…Siedlecka et al, 2004;Nystuen et al, 2008). Evidence of crustal hyperextension at the pre-Caledonian continental margin of Baltica (Andersen et al, 2012) and its inferred conjugate margin of Laurentia (van Staal et al, 2013;Chew and van Staal, 2014) suggest that Iapetan rifting was magma-poor (e.g. Louden and Chian 1999;Dean et al 2000), and that comparably large volumes of rift-related igneous rocks such as those of the KIC were only locally emplaced at the very final stages of rifting, when the lithosphere was already substantially thinned, and magma supply could keep pace with crustal attenuation and plate separation (Robinson et al, 2008;Dilek and Furnes, 2014).…”

Section: Age Of the Kicmentioning

confidence: 99%

Root zone of a continental rift: the Neoproterozoic Kebnekaise Intrusive Complex, northern Swedish Caledonides

Kirsch

Svenningsen²

2015

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Mafic magmatic rocks formed between ca. 615 and 560 Ma along the Neoproterozoic margins of Baltica and Laurentia are classically attributed to continental rifting heralding the opening of the Iapetus Ocean. We report new data for the Kebnekaise Intrusive Complex (KIC) exposed in the Seve Nappes in northern Sweden. The KIC consists of sheeted dolerite dykes and gabbroic bodies with mutually intrusive relations. Major and trace element data exhibit a transitional-to normal-mid-ocean-ridge basalt-type geochemical signature. Differentiation processes and late-stage liquid immiscibility of a tholeiitic melt are considered to account for the compositional range exhibited by the KIC igneous rocks. U/Pb SIMS geochronological data from zircon rims yield an emplacement age of 578^9 Ma. The KIC is thus younger and more depleted than coeval mafic rocks found in the Seve Nappe, and is interpreted to represent a highlevel magma plumbing system in a late-stage continental rift. The composition and volume of rift-related igneous rocks in the Seve Nappes are inconsistent with a mantle plume origin, but are thought to record progressive lithospheric thinning and increasing involvement of an asthenospheric mantle component.

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Section: Age Of the Kicmentioning

confidence: 99%

Root zone of a continental rift: the Neoproterozoic Kebnekaise Intrusive Complex, northern Swedish Caledonides

Kirsch

Svenningsen²

2015

GFF

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“…Present‐day rifted margins are generally submerged and buried like the northeast Atlantic (e.g., Clerc et al, ; Faleide et al, ; Gernigon et al, ) and only rarely exposed, like in the Afar rift (e.g., Bastow & Keir, ; Stab et al, ) or in the Gulf of California (e.g., van Wijk et al, ). Some fossil rifted margin analogues can be found in Phanerozoic mountain belts around the world like in the southern Scandinavian Caledonides (Andersen et al, ; Jakob et al, ), Appalachians (Chew & van Staal, ), Alps (Manatschal, ; Manatschal & Müntener, ; Mohn et al, ), and Pyrenees (Lagabrielle et al, ), but these are generally classified as magma‐poor rifted margins. Their magma‐rich counterparts, on the other hand, are often lost by subduction due to metamorphic densification.…”

Section: Introductionmentioning

confidence: 99%

Timing of Breakup and Thermal Evolution of a Pre‐Caledonian Neoproterozoic Exhumed Magma‐Rich Rifted Margin

et al. 2019

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During the terminal stages of Wilson cycles, remnants of magma‐poor margins may be incorporated into the orogens, whereas the magma‐rich margins often are lost in subduction due to low buoyancy. The understanding of magma‐rich margins is therefore mostly based on drill holes and geophysical observations. In this contribution, we explore the temporal evolution and the ambient conditions of a magma‐rich rifted margin preserved within the Scandinavian Caledonides. The Scandinavian Dike Complex was emplaced into a sedimentary basin during the initial breakup and opening of the Iapetus Ocean 615 to 590 million years ago. The dike complex constitutes 70–90% of the magma‐rich, syn‐rift basins and is locally well preserved despite the complex Caledonian history. This contribution provides new observations about the geometry, relative timing, and development of the margin. Jadeite‐in‐clinopyroxene geothermobarometry, titanium‐in‐biotite geothermometry, and garnet isopleth modeling show that the ambient pressure and temperature conditions were similar for the entire dike complex at 0.25 to 0.45 GPa, with contact metamorphic temperatures up to approximately 700 °C. In the northernmost part of the study area, U‐Pb dating of magmatic zircon shows that partial melting of the sedimentary host rock, at relatively shallow levels, occurred at 612 Ma. This shows that the crust was molten already 6 million years before the northernmost dike swarm was emplaced at 605.7 ± 1.8 Ma. We propose that the locally pervasive partial melting occurred due to high geothermal gradients and introduction of mafic melt in the lower crust. These processes significantly reduced the strength of the crust, eventually facilitating continental breakup.

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“…Other fossil margins have recently been identified within the Zagros (Wrobel-Daveau et al, 2010) and AppalachianCaledonian orogenic belts (Andersen et al, 2012;Chew et Van Staal, 2014). At present, the Pyrenean domain is also considered as hosting relevant analogs of distal passive margins, and its pre-orogenic evolution is being intensely revisited (Lagabrielle and Bodinier, 2008;Jammes et al, 2009;Lagabrielle et al, 2010;Masini 2011;Clerc et al, 2012;Clerc et al, 2013;Masini et al, 2014;Tugend et al, 2014).…”

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confidence: 99%

High-temperature metamorphism during extreme thinning of the continental crust: a reappraisal of the North Pyrenean passive paleomargin

et al. 2015

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Abstract. An increasing number of field examples in mountain belts show that the formation of passive margins during extreme continent thinning may occur under conditions of high to very high thermal gradient beneath a thin cover of syn-rift sediments. Orogenic belts resulting from the tectonic inversion of distal margins and regions of exhumed continental mantle may exhibit high-temperature, low-pressure (HT-LP) metamorphism and coeval syn-extensional, ductile deformation. Recent studies have shown that the northern flank of the Pyrenean belt, especially the North Pyrenean Zone, is one of the best examples of such inverted hot, passive margin. In this study, we provide a map of HT-LP metamorphism based on a data set of more than 100 peak-temperature estimates obtained using Raman spectroscopy of the carbonaceous material (RSCM). This data set is completed by previous PT (pressure and temperature) estimates based on mineral assemblages, and new 40 Ar-39 Ar (amphibole, micas) and U-Pb (titanite) ages from metamorphic and magmatic rocks of the North Pyrenean Zone. The implications on the geological evolution of the Cretaceous Pyrenean paleomargins are discussed. Ages range mainly from 110 to 90 Ma, and no westward or eastward propagation of the metamorphism and magmatism can be clearly identified. In contrast, the new data reveal a progressive propagation of the thermal anomaly from the base to the surface of the continental crust. Focusing on the key localities of the Mauléon basin, Arguenos-Moncaup, Lherz, Boucheville and the Bas-Agly, we analyze the thermal conditions prevailing during the Cretaceous crustal thinning. The results are synthetized into a series of three regional thematic maps and into two detailed maps of the Arguenos-Moncaup and Lherz areas. The results indicate a first-order control of the thermal gradient by the intensity of crustal thinning. The highest grades of metamorphism are intimately associated with the areas where subcontinental mantle rocks have been unroofed or exhumed.

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The Ocean – Continent Transition Zones Along the Appalachian – Caledonian Margin of Laurentia: Examples of Large-Scale Hyperextension During the Opening of the Iapetus Ocean

Cited by 43 publications

References 92 publications

Root zone of a continental rift: the Neoproterozoic Kebnekaise Intrusive Complex, northern Swedish Caledonides

Root zone of a continental rift: the Neoproterozoic Kebnekaise Intrusive Complex, northern Swedish Caledonides

Timing of Breakup and Thermal Evolution of a Pre‐Caledonian Neoproterozoic Exhumed Magma‐Rich Rifted Margin

High-temperature metamorphism during extreme thinning of the continental crust: a reappraisal of the North Pyrenean passive paleomargin

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