Eruption age of the Sverrefjellet volcano, Spitsbergen Island, Norway

摘要

Sverrefjellet is a Pleistocene-age basaltic volcanic construct on north-western Spitsbergen Island (Svalbard Archipelago, Norway). Published ages for the Sverrefjellet eruption range between 6000 years and ca. 1 million years before present. The age of eruption is dated here as 1.05±0.07 (1σ) My, consistent with Ar–Ar isochron and plateau ages of several analysed samples. Radiogenic Ar represents a small proportion of the released Ar, 15% in nearly all samples. Non-radiogenic Ar components include air, excess 40Ar (seen as inverse isochron intercept values 40Ar/36Ar?=?295.5), low-temperature alterations (Ar release at low temperature, with high Cl/K), carbonates and zeolites (Ar release at intermediate temperature) and xenolithic material (Ar release at high temperature, high Ca/K). The effects of the largely non-radiogenic argon sources are also seen in the total-gas Ar–Ar “ages”, which range from 1.3 to 10.3 My, significantly larger than the inferred eruption age. It is likely that total-gas Ar–Ar “ag...