Devonian granites and Tin mineralization in the footwall of the Dybendal Detachment in Hudson Land (North-East Greenland)

During the Middle Devonian-earliest Carboniferous, the sedimentation in North-East Greenland was characterised by the deposition of Old Red Sandstone (ORS) molasse in the Hudson Land Basin. In this area, Givetian conglomerates of the Vilddal Group, which postdate a first stage of Caledonian folding, unconformably sit on the core of large-scale anticlines and above a deep erosional surface that exposed Late Silurian migmatitic rocks of the lower part of the Nathorst Land Group. The ORS succession records folding and intrabasinal unconformities that are associated with the activation of extensional faults and subsequent compression and thrusting (Guarnieri 2021).

In Parkinson Bjerg, Middle Devonian sandstones of the Ankerbjergselv Fm rests in tectonic contact with Neoproterozoic metasandstones of the Nathorst Land Group in the footwall of a top-to-SW brittle/ductile extensional fault: the Dybendal Detachment. Rhyolitic and basaltic flows are intercalated within the sedimentary package at different stratigraphic levels and lie in the hanging wall of the detachment. The Dybendal Detachment is probably a splay of the Payer Land Detachment (Gilotti and Elvevold 2002) along which Lower Paleozoic carbonate rocks rest tectonically in contact with Paleoproterozoic gneisses that reached HP/HT granulite facies conditions, along a SW-dipping mylonitic zone. The peak metamorphism was dated at c. 405 Ma (Gilotti and Elvevold 2002) followed by partial melting of metapelites associated with isothermal decompression, probably during the Middle-Late Devonian, leading to the emplacement of a metamorphic core complex.

Tin mineralization associated with granitic intrusions in Parkinson Bjerg has been known since the mid-fifties of the last century (Harpøth et al., 1986) and recent U-Pb ages from cassiterite found in greisen floats, established a Devonian age for the mineralization (Keulen et al., 2024).

The structural setting of the Devonian intrusions in the footwall of the Dybendal Detachment suggests a correlation between magmatism and partial melting of the Payer Land gneisses during the emplacement of the metamorphic core complex.

 

References

Gilotti, J. A., & Elvevold, S. 2002. Extensional exhumation of a high-pressure granulite terrane in Payer Land, Greenland Caledonides: Structural, petrologic and geochronologic evidence from metapelites. Canadian Journal of Earth Sciences, 39, 1169–1187. https://doi.org/10.1139/e02-019. 

Guarnieri 2021. Devonian–Early Carboniferous thrust tectonics in the Old Red Sandstone Molasse Basin, North-East Greenland. Terra Nova 33, 521-528. https://doi.org/10.1111/ter.12544

Harpøth, O., Pedersen, J.L., Schønwandt, H.K. & Thomassen, B. 1986. The mineral occurrences of central East Greenland. Meddelelser om Grønland, Geoscience 17, 139 pp.

Keulen, N., Rosa, D., Heredia, B., Malkki, S., Whitehead, D., Thomsen, T. B. 2025. Tungsten and tin occurrences in East-Greenland, Geology & Ore 39, 12p.