Large igneous province in the North Atlantic, centered on Iceland
TheNorth Atlantic Igneous Province (NAIP) is alarge igneous province in theNorth Atlantic, centered onIceland. In thePaleogene, the province formed theThulean Plateau, a largebasalticlava plain,[1] which extended over at least 1.3 million km2 (500 thousand mi2) in area and 6.6 million km3 (1.6 million mi3) in volume.[2] The plateau was broken up during theopening of the North Atlantic Ocean leaving remnants preserved in northIreland, westScotland, theFaroe Islands, northwestIceland, eastGreenland,western Norway and many of the islands located in the north eastern portion of the North Atlantic Ocean.[3][4] The igneous province is the origin of theGiant's Causeway andFingal's Cave. The province is also known asBrito–Arctic province (also known as theNorth Atlantic Tertiary Volcanic Province) and the portion of the province in the British Isles is also called theBritish Tertiary Volcanic Province orBritish Tertiary Igneous Province.
The British Tertiary Volcanic Province (based on Emeleus & Gyopari 1992[5] and Mussettet al. 1988[6]) with UK map shown in context of the world map
Isotopic dating indicates the most activemagmatic phase of the NAIP was betweenc. 60.5[7] and c. 54.5Ma (million years ago)[8] (mid-Paleocene to early Eocene) – further divided into Phase 1 (pre-break-up phase) dated to c. 62–58 Ma and Phase 2 (syn-break-up phase) dated to c. 56–54 Ma.[9]
Studies have suggested that the modern dayIceland hotspot corresponds to the earlier 'North Atlantic mantle plume' that would have created the NAIP.[14] Through bothgeochemical observations and reconstructions ofpaleogeography, it is speculated that the present day Iceland hotspot originated as a mantle plume on theAlpha Ridge (Arctic Ocean) c. 130–120 Ma,[15] migrated downEllesmere Island, throughBaffin Island, onto the west coast of Greenland, and finally arrived on the east coast of Greenland by c. 60 Ma.[16]
Extensive outpourings of lava occurred, particularly in East Greenland,[17] which during the Paleogene was then adjacent to Britain. Little is known of thegeodynamics of the opening of the North Atlantic between Greenland and Europe.[18]
As the Earth's crust was stretched above themantle hotspot under stress from plate rifting,[19] fissures opened up along a line from Ireland to theHebrides andplutonic complexes were formed.[20] Hotmagma over 1000 °C surfaced as multiple, successive and extensivelava flows covered over the original landscape, burning forests, filling river valleys, burying hills, to eventually form the Thulean Plateau, which contained various volcanic landforms such aslava fields andvolcanoes.[5] There was more than one period of volcanic activity during the NAIP, in between which sea levels rose and fell anderosion took place.[21]
Volcanic activity would have started withvolcaniclastic accumulations, likevolcanic ash, quickly followed by vast outpourings of highlyfluid basaltic lava during successive eruptions through multiple volcanic vents or in linear fissures. Asmafic lowviscosity lava reached the surface it rapidly cooled and solidified, successive flows built up layer upon layer, each time filling and covering existing landscapes.Hyaloclastites andpillow lavas were formed when the lava flowed into lakes, rivers and seas. Magma that did not make it to the surface as flows froze in conduits asdikes andvolcanic plugs and large amounts spread laterally to formsills.Dike swarms extended across the British Isles throughout theCenozoic. Individual central complexes developed with arcuate intrusions (cone sheets,ring dikes andstocks), the intrusions of one centre cut through earlier centres recording magmatic activity with time. During intermittent periods of erosion and change in sea levels, heated waters circulated through the flows altering the basalts and deposited distinctive suites ofzeolite minerals.[6]
Activity of the NAIP 55 million years ago may have caused thePaleocene–Eocene Thermal Maximum, where a large amount of carbon was released into the atmosphere and the Earth substantially warmed.[22][23] One hypothesis is that the uplift caused by the NAIP hotspot causedmethane clathrates to dissociate and dump 2000 gigatons of carbon into the atmosphere.[24]
Basaltic volcanic rocks up to 2.5 kilometres (1.6 mi) thick cover 65,000 square kilometres (25,000 mi2) in east Greenland. Numerous intrusions related to hot-spot magmatism are exposed in the coastal region of east Greenland. The intrusions show a wide range of compositions. TheSkaergaard intrusion (Early Cenozoic or about 55 million year age) is a layeredgabbro (mafic) intrusion that has mineralized rock units enriched inpalladium andgold. In contrast, the Werner Bjerge complex is made up of potassium- and sodium-rich (alkaline)granitic rock, containingmolybdenum.[30]
Locations of submarine central complexes within the NAIP include:[20]
The British portion of the NAIP, particularly West Scotland, provides relatively easy access, compared to the largely inaccessible basalt fields of West Greenland, to deeply eroded relics of the central volcanic complexes.[31]
Locations of major intrusion complexes within the British part of the NAIP include:
Those occurrences within theHebrides are sometimes referred to as theHebridean Igneous Province.[50]
Other notable NAIP landform locations in the United Kingdom include:
Giant's Causeway – Polygonal basalt columns, which seen from above are large hexagonal pavements[51]
Canna andSanday – Basalt lava field with great thicknesses of boulder conglomerate, examples of periods of erosion by fast flowing rivers in between the lava flows.[52]
The intensity of scientific investigation within the NAIP has made it one of the most historically important and deeply studied igneous provinces in the world. Basalt petrology was born in the Scottish Hebrides in 1903 led by the eminent British geologist SirArchibald Geikie. From the outset Geikie studied the geology of Skye and other Western Isles taking a keen interest in volcanic geology and in 1871 he presented the Geological Society of London with an outline of the 'Tertiary Volcanic History of Britain'.[58] Following Geikie many have tried, and continue to study and understand the NAIP, and in doing so have advanced knowledge in geology, mineralogy and in more recent decades geochemistry and geophysics.[5]
^Eldholm, Olav; Kjersti Grue (10 February 1994). "North Atlantic volcanic margins: Dimensions and production rates".Journal of Geophysical Research: Solid Earth.99 (B2):2955–2968.Bibcode:1994JGR....99.2955E.doi:10.1029/93JB02879.Quantitative calculations of NAVP dimensions, considered minimum estimates, reveal an areal extent of 1.3{{e|6}} km2 and a volume of flood basalts of 1.8×106 km3, yielding a mean eruption rate of 0.6 km3/yr or 2.4 km3/yr if two-thirds of the basalts were emplaced within 0.5 m.y. The total crustal volume is 6.6×106 km3, resulting in a mean crustal accretion rate of 2.2 km3/yr. Thus NAVP ranks among the world's larger igneous provinces if the volcanic margins are considered.
^Rousse, S.; M. Ganerød; M.A. Smethurst; T.H. Torsvik; T. Prestvik (2007)."The British Tertiary Volcanics: Origin, History and New Paleogeographic Constraints for the North Atlantic"(PDF).Geophysical Research Abstracts.9.Archived(PDF) from the original on 2013-12-17. Retrieved2013-12-17.The NAIP formed during two major magmatic phases: a pre-break-up phase (62–58 Ma) and a syn-break-up phase (56-54 Ma) contemporaneous with the onset of North Atlantic sea floor spreading.
^Torsvik, T.H.; B. Steinberger; C. Gaina (2007)."North Atlantic Plate Motions and Plumes"(PDF).Geophysical Research Abstracts.9.Archived(PDF) from the original on 2013-12-17. Retrieved2013-12-17.Fixed hotspot frames show uniform NE movement of the coupled North American, Greenland, and Eurasian plates from ~95 to 80 Ma.
^Faleide, Jan Inge; Tsikalas, F.; Breivik, A. J.; Mjelde, R.; et al. (2008)."Structure and evolution of the continental margin off Norway and the Barents Sea".Episodes.31 (1): 82.doi:10.18814/epiiugs/2008/v31i1/012.Breakup in the NE Atlantic was preceded by prominent Late Cretaceous-Paleocene rifting. At the onset of this rifting, the area between NW Europe and Greenland was an epicontinental sea covering a region in which the crust had been extensively weakened by previous rift episodes. Ren et al. (2003) suggested onset of rifting at about 81 Ma
^Chalmers, J. A.; Pulvertaft, T.C.R. (1 January 2001). "Development of the continental margins of the Labrador Sea: a review".Geological Society, London, Special Publications.187 (1):77–105.Bibcode:2001GSLSP.187...77C.doi:10.1144/GSL.SP.2001.187.01.05.S2CID140632779.The Labrador Sea is a small oceanic basin that developed when the North American and Greenland plates separated. An initial period of stretching in Early Cretaceous time formed sedimentary basins now preserved under the continental shelves and around the margins of the oceanic crust. The basins subsided thermally during Late Cretaceous time and a second episode of tectonism took place during latest Cretaceous and early Paleocene time, before the onset of sea-floor spreading in mid-Paleocene time.
^Lundin, Erik R.; Anthony G. Doré (2005).Fixity of the Iceland "hotspot" on the Mid-Atlantic Ridge: Observational evidence, mechanisms, and implications for Atlantic volcanic margins. Vol. 388. pp. 627–651.doi:10.1130/0-8137-2388-4.627.ISBN978-0-8137-2388-4.{{cite book}}:|journal= ignored (help)
^Saunders, A.D.; S. Drachev; M.K. Reichow (2005)."Tracking the Iceland Plume across the Arctic Ocean"(PDF).Geophysical Research Abstracts.7.Archived(PDF) from the original on 2013-12-17. Retrieved2013-12-17.It is widely assumed that Iceland sits above a mantle plume or hotspot. Plate reconstructions place the plume beneath what is now northeastern Canada at about 80 Ma. This correlates with an episode of basaltic volcanism in the Queen Elizabeth Islands, dated at around 90 Ma. The aseismic Alpha Ridge is bathymetrically linked to northern Ellesmere Island, and extends northwards beneath the Arctic Ocean.
^Tegner, C; Duncan, R; Bernstein, S; Brooks, C; Bird, D; Storey, M (15 March 1998). "40Ar/39Ar geochronology of Tertiary mafic intrusions along the East Greenland rifted margin: Relation to flood basalts and the Iceland hotspot track".Earth and Planetary Science Letters.156 (1–2):75–88.Bibcode:1998E&PSL.156...75T.doi:10.1016/S0012-821X(97)00206-9.The East Greenland Tertiary Igneous Province includes the largest exposed continental flood basalt sequence within the North Atlantic borderlands. Plate-kinematic models indicate the axis of the ancestral Iceland mantle plume was located under Central Greenland at ~60 Ma and subsequently crossed the East Greenland rifted continental margin.
^Riisager, Janna; Riisager, Peter; Pedersen, Asger Ken (September 2003). "Paleomagnetism of large igneous provinces: case-study from West Greenland, North Atlantic igneous province".Earth and Planetary Science Letters.214 (3–4):409–425.Bibcode:2003E&PSL.214..409R.doi:10.1016/S0012-821X(03)00367-4.
^abHitchen, K.; Ritchie, J. D. (1 May 1993). "New K–Ar ages, and a provisional chronology, for the offshore part of the British Tertiary Igneous Province".Scottish Journal of Geology.29 (1):73–85.Bibcode:1993ScJG...29...73H.doi:10.1144/sjg29010073.S2CID140557766.
^Williamson, I. T.; Bell, B. R. (3 November 2011). "The Palaeocene lava field of west-central Skye, Scotland: Stratigraphy, palaeogeography and structure".Transactions of the Royal Society of Edinburgh: Earth Sciences.85 (1):39–75.doi:10.1017/S0263593300006301.S2CID131299688.
^Tarney, J.; Wood, D. A.; Saunders, A. D.; Cann, J. R.; Varet, J. (24 July 1980). "Nature of Mantle Heterogeneity in the North Atlantic: Evidence from Deep Sea Drilling".Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.297 (1431):179–202.Bibcode:1980RSPTA.297..179T.doi:10.1098/rsta.1980.0209.S2CID93530327.Studies of dredged and drilled samples from the North Atlantic ocean have revealed that basalts with a wide range of major and trace element compositions have been generated at the Mid-Atlantic Ridge. Drilling along mantle flow lines transverse to the ridge has shown that different segments of the MAR have produced basalts with a distinct compositional range for tens of millions of years.
^Heister, L. E.; O'Day, P. A.; Brooks, C. K.; Neuhoff, P. S.; Bird, D. K. (1 March 2001). "Pyroclastic deposits within the East Greenland Tertiary flood basalts".Journal of the Geological Society.158 (2):269–284.Bibcode:2001JGSoc.158..269H.doi:10.1144/jgs.158.2.269.S2CID131414316.Stratigraphic, geochemical and mineralogical characterization of pyroclastic deposits on the Gronau WestNunatak of East Greenland indicates that both alkaline and basaltic tephras occurred during the eruption of flood basalts associated with the opening of the North Atlantic ocean in the early Tertiary.
^Brooks, C. K.; Nielsen, T. F. D.; Petersen, T. S. (1976). "The Blosseville Coast basalts of East Greenland: Their occurrence, composition and temporal variations".Contributions to Mineralogy and Petrology.58 (3):279–292.Bibcode:1976CoMP...58..279B.doi:10.1007/BF00402356.S2CID129787285.Major and trace element compositions are presented for basalts from the area betweenKangerdlugssuaq andScoresby Sound, East Greenland. The bulk of these lavas have a very uniform composition and are tholeiites... The only significant variation is minor and represents a change to a more evolved type to the south, a variation which may be similar to that observed in Postglacial Icelandic lavas. The earliest lavas are of a picritic type...
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This article incorporatespublic domain material fromNokleberg, W.J.; Baweic, W.J.; Doebrich, J.L.; Lipin, B.R.; et al. (2005).Geology and Nonfuel Mineral Deposits of Greenland, Europe, Russia, and Northern Central Asia(PDF). USGS. Open File Report 2005–1294D.Archived(PDF) from the original on 2016-03-05. Retrieved2016-01-10.