Niobium mineralization of sedimentary carbonates, Lewisian Complex, UK

Abstract

Proterozoic limestone in a north British terrane contains a newly recognised occurrence of Nb-REE minerals. The mineralized Loch Shin Limestone is in the Lewisian Complex of the Northern Highlands of Scotland, intruded by alkaline plutons above a Caledonian (∼0.43 Ga) subduction zone. The mineral assemblage includes columbite, calcium niobate minerals, and niobian rutile and also includes W-and Sn-bearing phases. The interval between limestone deposition and mineralization was over a billion years. Other limestones in the Lewisian Complex that were not affected by alkaline plutons are not mineralized by Nb. The occurrence indicates that there may be exploration potential for Nb in limestones mineralized by hydrothermal activity above subduction zones with alkaline intrusions.

Seawater signatures in the supracrustal Lewisian Complex, Scotland

“…Coeval supracrustal rocks in adjacent Greenland and Scandinavia contain ore deposits in which evaporites are implicated as a source of mineralizing fluids (Frietsch et al 1997;Horn et al 2019). Metalliferous ores and mineral showings in the Lewisian supracrustals (Coats et al 1997;Drummond et al 2020;Parnell et al 2021) suggest that there may also be potential deposits in Scotland, to which evaporite-derived fluids could have contributed.…”