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Geological Survey of Denmark and Greenland (GEUS)
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The North Atlantic Igneous province

The province comprises Paleogene volcanic rocks and intrusions stretching from West Greenland over South-East and East Greenland and the Faeroes to Denmark. The objectives of the studies are to describe stratigraphic and structural relations and establish regional correlations, and to understand the processes of melt formation, evolution and crystallisation and the interplay between volcanic and tectonic processes during rifting and continental break-up. The research supports exploration activities for hydrocarbons in the basins and for deposits of metals such as Ni, Pt , Au and Mo in intrusions and lavas.

Volcanic development in the Nuussuaq Basin, West Greenland
Lotte Melchior Larsen in collaboration with Asger Ken Pedersen and Gunver Krarup Pedersen (Univ. Copenhagen) and Keld S. Dueholm (Techn. Univ. Copenhagen), as well as with several departments within GEUS.

The Nuussuaq Basin extends onshore from Disko to Svartenhuk Halvø and is part of a series of linked basins extending offshore along the west coast of Greenland. The Nuussuaq basin was a depositional area for clastic sediments from at least the mid-Cretaceous to the Paleocene. Volcanism started in the Paleocene. Most of the voluminous onshore volcanics were deposited in a short period at c. 61-59 Ma. Younger volcanics occur sparingly onshore and are probably more extensive offshore.
The volcanic rocks erupted into a marine embayment that was gradualy filled out laterally by progradation from west to east. The net result is a very complex facies architecture of the lavas, hyaloclastites and contemporaneous sediments. Excellent exposures in >1000 m high cliffs are onshore analogues to seismic sections on the NW European shelf, sharing many features with these.
The oldest volcanics are voluminous picrites that formed from very Mg-rich and very hot magmas. Some of the magmas reacted with coal-bearing sediments and became so reduced that they precipitated native iron. The reactions also led to formation of Cu- and Ni-depleted lavas, and accumulations of these elements and PGEs are inferred to be present at depth. Further, oil seeps in the volcanics are widespread.
Recent work is centred in the Disko-Nuussuaq area which is covered by 7 geological maps at scale 1: 100 000 of which 6 are published and one is being mapped. In addition, five 80-120 km long vertical W-E sections through the basin have been compiled photogrammetrically at scale 1: 20 000. Three of these sections are published as 'geological sheets' equivalent to map sheets, while two are in production.
Present studies are concerned with stratigraphic and structural relations, and geochemical and petrological analysis and interpretation. The work is focussed on production of a synthesis of the volcanic development in the Disko-Nuussuaq area, to be published in the GEUS Bulletin Series.

Thin section of picrite pillow showing olivine crystals

Thin section of picrite pillow showing olivine crystals with small chromite octahedra, enclosed in clear yellow fresh glass.

The south coast of the Nuussuaq peninsula

The south coast of the Nuussuaq peninsula, showing Cretaceous - Tertiary sediments overlain by 300 m of foreset-bedded hyaloclastites followed by c. 500 m of subaerial picritic lava flows. The mountain peak is c. 1400m high.

Recent publications
Larsen, L.M. & Pedersen, A.K. 2000. Processes in high-Mg, high-T magmas: evidence from olivine, chromite and glass in Palaeogene picrites from West Greenland. Journal of Petrology 41, 1071–1098.
Pedersen, A. K., Larsen, L. M., Riisager, P. & Dueholm, K. S. 2002. Rates of volcanic deposition, facies changes and movements in a dynamic basin: the Nuussuaq Basin, West Greenland, around the C27n–C26r transition. In: Jolley, D. W. & Bell, B. R. (eds), The North Atlantic Igneous Province: stratigraphy, tectonics, volcanic and magmatic processes. Geological Society (London) Special Publication 197, 157–181.
Larsen, L. M., Pedersen, A. K., Sundvoll, B. & Frei, R. 2003: Alkali picrites formed by melting of old metasomatised lithospheric mantle: Manîtdlat Member, Paleocene of West Greenland. Journal of Petrology 44, 3–38.
Pedersen, A. K., Larsen, L. M., Pedersen, G. K., Heinesen, M. V. & Dueholm, K. S. 2003: Geological section along the south and south-west coast of Disko, central West Greenland. 1:20 000 coloured geological sheet. Copenhagen: The Geological Survey of Denmark and Greenland
For maps and other geological sections, see pp 36 (69-70 deg. N) and 41 in http://www.geus.dk/publications/cat-publ-greenland.pdf


Structure and stratigraphy of the plateau lavas between Kangerlussuaq and Scoresby Sund
Lotte Melchior Larsen and W. Stuart Watt in collaboration with Asger Ken Pedersen (Univ. Copenhagen) and Keld S. Dueholm (Techn. Univ. Copenhagen).

In central East Greenland, flood lavas cover c. 65 000 km 2 along the Blosseville Kyst between Kangerlussuaq and Scoresby Sund, the largest onshore lava plateau in the N Atlantic Province. Ages range from c 61 Ma for the oldest lavas through 56-54 Ma for the major part of the volcanics, to c 48 Ma for some subordinate lavas. The youngest volcanic rocks in Greenland are some small-volume lavas of Miocene age (c. 14 Ma) that cap the central East Greenland lava plateau.
Present work continues the studies initiated by the Danish Lithosphere Centre (DLC). Following extensive field work in 1995, the stratigraphy established in the Scoresby Sund area has been extended to the whole lava plateau. Further correlation has been established between the volcanic successions in East Greenland and the Faeroes, and the studies are extended to the coeval volcanic ash deposits in Denmark.

The East Greenland plateau basalts
The East Greenland plateau basalts. In the foreground light syenites of the Borgtinderne intrusion.

magnify  Pre-break-up reconstruction of the North Atlantic

Pre-break-up reconstruction of the North Atlantic, showing the extent of two basalt formations across the line of opening.

Pedersen, A. K., Watt, M., Watt, W. S. & Larsen, L. M. 1997: Structure and stratigraphy of the Early Tertiary basalts of the Blosseville Kyst, East Greenland. Journal of the Geological Society, London 154,  565–570.
Larsen, L.M., Waagstein, R., Pedersen, A.K. & Storey, M.S. 1999. Trans-Atlantic correlation of the Palaeogene volcanic successions in the Faeroe Islands and East Grenland. Journal of the Geological Society, London 156, 1081–1095.
Fitton, J.G., Larsen, L.M., Saunders, A.D., Kempton, P.D. & Hardarson, B.S. 2000. Palaeogene continental to oceanic magmatism on the SE Greenland continental margin at 63ºN: a review of the results of Ocean Drilling Program Legs 152 and 163. Journal of Petrology 41, 951–966.
Storey, M., Pedersen, A. K., Stecher, O., Bernstein, S., Larsen, H. C., Larsen, L. M., Baker, J. & Duncan, R. A. 2004. Long-lived postbreakup magmatism along the East Greenland margin: Evidence for shallow-mantle metasomatism by the Iceland plume. Geology 32, 173–176.

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