Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences



Occurrence number: 
Longitude: -24.62323, Latitude: 71.57169

The Revdal area of Scoresby Land, Semersooq, Greenland hosts a steep valley intruded by several dykes. These structures are subvertical, thin (0.1-0.5 m), striking between 116° and 154° N and intruding the conglomerates of the Huledal Formation, the evaporites of the Revdal Member of the Karstryggen Formation, and Early Permian continental sandstones. These dykes terminate at the contact with the limestone of the Karstryggen and Wegener Halvø Formations, with clasts of dyke rocks found within conglomerates ~5 m above the contact of the dykes and limestone, formed via hydraulic fracturing of wet sediment. Unexplained occurrences of dyke clasts occur at higher levels above the contact. Dyke rocks are alkaline lamprophyres, described as monchiquites, alnöitic monchiquites, and fourchites, with the main phenocryst being clinopyroxene. Pseudomorphed olivine is found only in the monchiquites and alnöitic monchiquites, and biotite or phlogopite phenocrysts restricted to alnöitic monchiquites. Whole rock data and CIPW norms can be found in Larsen et al. (1990).

Field observations suggest Late Permian, K-Ar of biotite and whole rock suggests Tertiary (50-33 Ma) (Larsen et al., 1990)

LARSEN, P.H., STEMMERIK, L., NIELSEN, T.F.D. & REX, D.C., 1990. Lamprophyric dykes in Revdal, Scoresby Land, East Greenland: conflicting field observations and K-Ar age determinations. Bulletin of the Geological Society of Denmark 38 pp 1-9

Fig 1. Location of dykes at Revdal (Larsen et al., 1990, Fig 2).
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