Sulfur isotopic composition of mineral-hosted sulfide inclusions from Tristan, Inaccessible, Nightingale and Gough island lavas

Sulfur isotopes were analyzed by SIMS on 47 sulfide inclusions, a total of 81 spot analyses, hosted in phenocrysts (olivine, clinopyroxene, plagioclase, Ti-magnetite or ilmenite) of basaltic rocks from Tristan Island group (6 samples from Tristan da Cunha, two from Inaccessible and one from Nightingale) and three samples from Gough Island. These islands represent the most recent activity of the major 130 Ma-long-lived EMI-type Tristan-Gough plume system with a root at the core-mantle boundary related to the African large low shear wave velocity province (LLSVP). Sulfur isotopes have emerged in the last few years as a promising tool to address questions of age and surface origin of mantle plume precursor material. The Archean/earliest Proterozoic is with >2.45 billion years older than half the age of the Earth. Only during those early times when there was little oxygen in the atmosphere, sulfur was changed in the atmosphere by solar radiation, forming so-called mass-independently fractionated sulfur isotopic compositions (MIF-S) that then rained onto the oceanic plate and was subducted into the mantle. So when we measure MIF-S in mineral-hosted sulfide inclusions in volcanic rocks, it tells us that the magma formed from material that once resided at the surface of the Earth and that this surface material is older than 2.45 billion years.