Shallow magma storage and volcanism at Beerenberg volcano, Jan Mayen

The Beerenberg volcano lies on the island of Jan Mayen and represents the northernmost active surface volcano in the world. Jan Mayen island is situated in the Arctic north-Atlantic Ocean, just south of the junction between the Mohn’s ridge and the Jan Mayen fracture zone, where the mid-ocean ridge transitions to the Kolbeinsey ridge further west. The Beerenberg volcano has gently dipping flanks and a more prominent central crater, reaching a maximum altitude of 2272 m a.s.l. The geology of the Jan Mayen island was studied extensively in the 1970s and 1980s and three primary magma types were identified: primitive basalts, ne-normative basalts and trachytes. The volcanism from the Beerenberg central volcano is limited to primitive basalts, and alkaline basalts, with some more intermediate volcanics near the central crater. Most of, if not all, the recent eruptions of Beerenberg have been in the form of flank eruptions of primitive basaltic and trachybasaltic compositions. However, the shallow magma storage systems of the Beerenberg volcano remain unstudied, and geophysical data from past eruptions are lacking, limiting our insights into this.In this study we investigate the shallow magma storage systems under Beerenberg by analysing a selection of samples from Jan Mayen and the surrounding seas: tephra from soil sections on the flanks of Beerenberg, rock samples from the summit crater and tephra from sediments in the seas around Beerenberg. These samples have been analysed using EPMA on glass shards, olivine, pyroxene and feldspar crystals, and we present the results from these analyses along with geothermobarometric calculations to infer the shallow magma storage conditions under the Beerenberg volcano. Our findings give new insights into the magmatic process and plumbing beneath Beerenberg that can be valuable during future volcanic unrest.