Quarternary multi-stage alkaline volcanism at Vesteris Seamount (Norwegian—Greenland Sea): evidence from laser step heating 40Ar/ 39Ar experiments
Vesteris Seamount is a high-latitude intraplate volcano located in the Norwegian—Greenland Sea (ca 73°30'N/9°W). Based on its tectonic setting as a single isolated seamount far from an active ridge regime, Vesteris differs from near-ridge seamounts, hotspot-generated seamounts associated with a seamount chain, or from seamounts thought to be genetically related to propagating fracture zones. During cruise ARK VII/1 with R.V. "Polarstern" volcanic rocks from Vesteris summit and flank regions were sampled in order to evaluate the volcanic history of this seamount and the development of intraplate volcanism within the Norwegian—Greenland Sea. Laser step heating 40Ar/ 39Ar measurements indicate a mugearitic eruption at 0.010-0.085 Ma (groundmass plateau ages) and earlier trachybasaltic and tephritic eruptions at 0.50-0.65 Ma (kaersutite and plagioclase phenocryst plateau ages). Based on geological models, the earliest volcanic phase is considered unlikely to be older than 7-13 Ma. Volcanic activity younger than the mugearitic eruption can not be ruled out. The 40Ar/ 39Ar measurements suggest multi-stage volcanism over geological periods of time for the isolated intraplate Vesteris seamount. From the age data it appears that Vesteris volcanism is neither genetically related to the hypothetical Jan Mayen hotspot nor to the mid-Atlantic ridge system. The laser heating 40Ar/ 39Ar method has proved to be suitable for dating very young (Mugearite: Upper Late Pleistocene) oceanic intraplate volcanic rocks.