Reyðarártindur is a granophyre pluton exposed in East Iceland, which prior to this field season had not been mapped in detail. Dated at 7.30 ± 0.06 Ma, the ~ 15 km² pluton was emplaced into the flat-lying basaltic lava flows of the Neogene rift zone and felsic volcanic deposits of the Lon Central Volcano (Padilla, 2015). The intrusion is the oldest of the South-East Iceland Intrusive Suite, and these plutons are interpreted to be the shallow plumbing systems of late Tertiary volcanic centres (Cargill et al., 1928; Furman et al., 1992; Padilla, 2015).

Glacial erosion has carved a valley through the centre of Reyðarártindur, exposing cross sections of the roof, the pluton interior and overlying volcanic rocks likely associated to Reyðarártindur. These features make it an ideal study area of pluton-volcano connection. We have conducted field mapping, sampling and photogrammetry with the aim to investigate plutonic-volcanic-tectonic processes.

The pluton is NNW-SSE trending, which is in contrast to the NE-SW regional dyke trend. While the pluton walls are steeply-dipping, the pluton roof is mostly flat but offset up to 100m by steep dip-slip faults. Many of these faults are intruded by felsic dykes, in some cases connecting the pluton to overlying volcanic rocks. Using photogrammetry, we have mapped the shallowly dipping basaltic host rock, the faults and dykes in the pluton roof. We will present first results on the shape of the magma body and the pluton roof structure. We will then discuss the implications of the roof structures and the pluton shape for the plutonic-volcanic connection and the evolution of the Reyðarártindur intrusion.

References

Cargill, H., Hawkes, L., and Ledeboen, J. (1928). The major intrustions of South-Eastern Iceland. Q. J. Geol. Soc. London 84, 505–539.

Furman, T., Meyer, P. S., and Frey, F. (1992). Evolution of Icelandic central volcanoes: evidence from the Austurhorn intrusion, southeastern Iceland. Bull. Volcanol. 55, 45–62. doi:10.1007/BF00301119.

Padilla, A. (2015). Elemental and isotopic geochemistry of crystal-melt systems: Elucidating the construction and evolution of silicic magmas in the shallow crust, using examples from southeast Iceland and southwest USA [PhD Dissertation: Vanderbilt University].