A non‐local source for slate on the roof of Chingford Stables, Dunedin, New Zealand (note)

Chingford Stables in Dunedin, New Zealand was constructed in 1880 and is the only remaining building of the former Chingford Estate. In 2020 Chingford Stables was re-roofed because of decay of the roof slate. The question arose as to whether the pre-2020 slate had been obtained from a local North Otago quarry, which was active when the stables were built, or from Wales like many nineteenth-century New Zealand roofs of the time. Rb and Sr isotopic analysis of a Chingford slate sample was used to answer this question. On an ⁸⁷Rb/⁸⁶Sr vs. ⁸⁷Sr/⁸⁶Sr diagram, the Chingford slate clearly lies on 430-400 Ma Welsh slate isochron lines and is distinctly more radiogenic (older) than 250-170 Ma Otago Schist isochrons. The Chingford Stables roof slate did therefore not have a local provenance.