The deep crustal structure of the mafic–ultramafic Seiland Igneous Province of Norway from 3-D gravity modelling and geological implications

Pastore, Zeudia; Fichler, Christine; McEnroe, Suzanne A.

doi:10.1093/gji/ggw362

Cited by 14 publications

(19 citation statements)

References 45 publications

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“…In NW Finnmark, Paleoproterozoic basement rocks occur in several tectonic windows of the Caledonides, e.g., Repparfjord-Komagfjord and Alta-Kvaenangen tectonic windows (Zwaan and Gautier, 1980;Pharaoh et al, 1982Pharaoh et al, , 1983Bergh and Torske, 1988;Fig. 1), and consist of lowgrade supracrustal metavolcanics and metasedimentary rocks of the Raipas Group.…”

Section: Precambrian Basement Rocksmentioning

confidence: 99%

“…Recent geophysical studies by Pastore et al (2016) show that the base of the Seiland Igneous Province defines two deep-reaching roots located below the islands of Seiland and Sørøya constraining the thickness of the Kalak Nappe Complex in this area to a maximum of 10 km. On the Porsanger and Varanger peninsulas, ENE-WSW-to NNE-SSW-trending Ediacaran metadolerite dyke swarms are particularly common, and they are associated with the rifting of the Iapetus Ocean as well (see Roberts, 1972;Siedlecka et al, 2004;Nasuti et al, 2015).…”

Section: Caledonian Nappesmentioning

confidence: 99%

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Middle to Late Devonian–Carboniferous collapse basins on the Finnmark Platform and in the southwesternmost Nordkapp basin, SW Barents Sea

et al. 2018

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Abstract. The SW Barents Sea margin experienced a pulse of extensional deformation in the Middle-Late Devonian through the Carboniferous, after the Caledonian Orogeny terminated. These events marked the initial stages of formation of major offshore basins such as the Hammerfest and Nordkapp basins. We mapped and analyzed three major fault complexes, (i) the Måsøy Fault Complex, (ii) the Rolvsøya fault, and (iii) the Troms-Finnmark Fault Complex. We discuss the formation of the Måsøy Fault Complex as a possible extensional splay of an overall NE-SW-trending, NW-dipping, basement-seated Caledonian shear zone, the Sørøya-Ingøya shear zone, which was partly inverted during the collapse of the Caledonides and accommodated top-NW normal displacement in Middle to Late Devonian-Carboniferous times.

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Section: Precambrian Basement Rocksmentioning

confidence: 99%

Section: Caledonian Nappesmentioning

confidence: 99%

Middle to Late Devonian–Carboniferous collapse basins on the Finnmark Platform and in the southwesternmost Nordkapp basin, SW Barents Sea

et al. 2018

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“…The SIP has an exposed area of more than 5,000 km 2 and an estimated minimum volume of~17,000 km 3 of Ediacaran mafic and ultramafic rocks (Pastore et al, 2016;Pastore, Fichler, & McEnroe, 2018). The SIP was emplaced at approximately 570-560 Ma at depths of 25-35 km (Larsen et al, 2018;Roberts, 2007;Roberts et al, 2006).…”

Section: Regional Settingmentioning

confidence: 99%

Magnetic Mineralogy and Petrophysical Properties of Ultramafic Rocks: Consequences for Crustal Magnetism

Maat

McEnroe

Church

et al. 2019

Geochem Geophys Geosyst

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Magnetic properties from the Reinfjord Ultramafic Complex, in northern Norway, which formed as part of a deep magmatic conduit system, have been investigated to determine the magnetic signature of ultramafic rocks now exposed at the surface and deeper in the lower crust. The dominant carriers in these ultramafic rocks are a chrome‐spinel with Fe‐rich exsolution blebs and exsolution lamellae of magnetite in clinopyroxene. Except locally, in a fault zone and in discrete small fractures, these rocks show only minor to no alteration. We infer that the magnetic oxides characterized here are representative of pristine magnetic carriers in similar rocks deeper in the crust. These oxides can be stable in lower crustal, possibly upper mantle, depths when temperatures are below the Curie temperature of magnetite, taking into account pressure effects. These ultramafic rocks are candidates for potential sources of long‐wavelength anomalies.

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“…The bedrock geology of NW Finnmark consists of Archean-Paleoproterozoic metavolcanic and metasedimentary rocks that occur in tectonic windows, e.g., the Alta-Kvaenangen (Bøe and Gautier, 1978;Zwaan and Gautier, 1980;Gautier et al, 1987;Bergh and Torske, 1988), Altenes (Jensen, 1996) and Repparfjord-Komagfjord tectonic windows (Reitan, 1963;Pharaoh et al, 1982Pharaoh et al, , 1983Torgersen et al, 2015a), overlying Caledonian nappes, e.g., Kalak Nappe Complex (Ramsay et al, 1979(Ramsay et al, , 1985Kirkland et al, 2005) and Magerøy Nappe (Andersen, 1981(Andersen, , 1984, and intruded by igneous rocks of the Seiland Igneous Province (Robins and Gardner, 1975;Elvevold et al, 1994;Pastore et al, 2016) and Honningsvåg Igneous Complex (Robins, 1998;Corfu et al, 2006). U-Pb ages on titanite from northern Troms provide a minimum estimate of approximately 440-420 Ma for retrograde (< 550 • C) Caledonian shearing (Gasser et al, 2015).…”

Section: Precambrian Basement Rocks and Caledonian Nappesmentioning

confidence: 99%

“…Metasedimentary rocks of the Kalak Nappe Complex were metamorphosed to amphibolite-facies conditions and are composed of psammites, schists and paragneisses cross-cut by low-angle thrusts and shear zones (Ramsay et al, 1979(Ramsay et al, , 1985. The Kalak Nappe Complex is intruded by mafic and ultramafic rocks of the Seiland Igneous Province (Robins and Gardner, 1975;Elvevold et al, 1994) that form two deep roots below the island of Seiland and Sørøya (Pastore et al, 2016). The struc-turally overlying Magerøy Nappe is made of tightly folded, greenschist-facies, metasedimentary rocks that are separated from the Kalak Nappe Complex by a low-angle thrust onshore Magerøya (Andersen, 1981(Andersen, , 1984.…”

Section: Precambrian Basement Rocks and Caledonian Nappesmentioning

confidence: 99%

Neoproterozoic and post-Caledonian exhumation and shallow faulting in NW Finnmark from K–Ar dating and <i>p</i>∕<i>T</i> analysis of fault rocks

2018

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Abstract. Well-preserved fault gouge along brittle faults in Paleoproterozoic, volcano-sedimentary rocks of the Raipas Supergroup exposed in the Alta–Kvænangen tectonic window in northern Norway yielded latest Mesoproterozoic (approximately 1050 ± 15 Ma) to mid-Neoproterozoic (approximately 825–810 ± 18 Ma) K–Ar ages. Pressure–temperature estimates from microtextural and mineralogy analyses of fault rocks indicate that brittle faulting may have initiated at a depth of 5–10 km during the opening of the Asgard Sea in the latest Mesoproterozoic–early Neoproterozoic (approximately 1050–945 Ma) and continued with a phase of shallow faulting to the opening of the Iapetus Ocean–Ægir Sea and the initial breakup of Rodinia in the mid-Neoproterozoic (approximately 825–810 Ma). The predominance and preservation of synkinematic smectite and subsidiary illite in cohesive and non-cohesive fault rocks indicate that Paleoproterozoic basement rocks of the Alta–Kvænangen tectonic window remained at shallow crustal levels (< 3.5 km) and were not reactivated since mid-Neoproterozoic times. Slow exhumation rate estimates for the early–mid-Neoproterozoic (approximately 10–75 m Myr−1) suggest a period of tectonic quiescence between the opening of the Asgard Sea and the breakup of Rodinia. In the Paleozoic, basement rocks in NW Finnmark were overthrusted by Caledonian nappes along low-angle thrust detachments during the closing of the Iapetus Ocean–Ægir Sea. K–Ar dating of non-cohesive fault rocks and microtexture mineralogy of cohesive fault rock truncating Caledonian nappe units show that brittle (reverse) faulting potentially initiated along low-angle Caledonian thrusts during the latest stages of the Caledonian Orogeny in the Silurian (approximately 425 Ma) and was accompanied by epidote–chlorite-rich, stilpnomelane-bearing cataclasite (type 1) indicative of a faulting depth of 10–16 km. Caledonian thrusts were inverted (e.g., Talvik fault) and later truncated by high-angle normal faults (e.g., Langfjorden–Vargsundet fault) during subsequent, late Paleozoic, collapse-related widespread extension in the Late Devonian–early Carboniferous (approximately 375–325 Ma). This faulting period was accompanied by quartz- (type 2), calcite- (type 3) and laumontite-rich cataclasites (type 4), whose cross-cutting relationships indicate a progressive exhumation of Caledonian rocks to zeolite-facies conditions (i.e., depth of 2–8 km). An ultimate period of minor faulting occurred in the late Carboniferous–mid-Permian (315–265 Ma) and exhumed Caledonian rocks to shallow depth at 1–3.5 km. Alternatively, late Carboniferous (?) to early–mid-Permian K–Ar ages may reflect late Paleozoic weathering of the margin. Exhumation rates estimates indicate rapid Silurian–early Carboniferous exhumation and slow exhumation in the late Carboniferous–mid-Permian, supporting decreasing faulting activity from the mid-Carboniferous. NW Finnmark remained tectonically quiet in the Mesozoic–Cenozoic.

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The deep crustal structure of the mafic–ultramafic Seiland Igneous Province of Norway from 3-D gravity modelling and geological implications

Cited by 14 publications

References 45 publications

Middle to Late Devonian–Carboniferous collapse basins on the Finnmark Platform and in the southwesternmost Nordkapp basin, SW Barents Sea

Middle to Late Devonian–Carboniferous collapse basins on the Finnmark Platform and in the southwesternmost Nordkapp basin, SW Barents Sea

Magnetic Mineralogy and Petrophysical Properties of Ultramafic Rocks: Consequences for Crustal Magnetism

Neoproterozoic and post-Caledonian exhumation and shallow faulting in NW Finnmark from K–Ar dating and <i>p</i>∕<i>T</i> analysis of fault rocks

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The deep crustal structure of the mafic–ultramafic Seiland Igneous Province of Norway from 3-D gravity modelling and geological implications

Cited by 14 publications

References 45 publications

Middle to Late Devonian–Carboniferous collapse basins on the Finnmark Platform and in the southwesternmost Nordkapp basin, SW Barents Sea

Middle to Late Devonian–Carboniferous collapse basins on the Finnmark Platform and in the southwesternmost Nordkapp basin, SW Barents Sea

Magnetic Mineralogy and Petrophysical Properties of Ultramafic Rocks: Consequences for Crustal Magnetism

Neoproterozoic and post-Caledonian exhumation and shallow faulting in NW Finnmark from K–Ar dating and &lt;i&gt;p&lt;/i&gt;∕&lt;i&gt;T&lt;/i&gt; analysis of fault rocks

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Neoproterozoic and post-Caledonian exhumation and shallow faulting in NW Finnmark from K–Ar dating and <i>p</i>∕<i>T</i> analysis of fault rocks