The Platreef is a platinum-group element (PGE) deposit in the form of a mafic-ultramafic, tabular body at the base of the northern (Potgietersrus) limb of the 2050 m.y. Bushveld Igneous Complex. The reef transgresses sedimentary floor rocks (footwall) of the 2600-2200 m.y. Transvaal Supergroup and the Archaean granite basement. The roof rocks (hangingwall) of the reef are PGE-free Main Zone gabbronorites of the Rustenburg Layered Suite. At the Sandsloot open-pit mine the Platreef consists of coarse to pegmatoidal pyroxenites and gabbros with accessory phlogopite, base-metal sulphides and oxides. Thermal metamorphism of siliceous dolomites that form the footwall has produced clinopyroxenites and calcsilicate hornfelses with a variety of skarn assemblages. These were subjected to later hydrothermal alteration and serpentinization that also affected parts of the Platreef. The link between sulphides and PGE in the Platreef has led previous authors to consider the mineralization as an orthomagmatic sulphide deposit, where sulphide separation collected PGE from a large volume of melt. In the reef and footwall, however, the development of extensive alteration zones with high concentrations of PGE-and semi-metal (Te, Sb, Se, Bi and Ge)-bearing platinum-group minerals that are typical of many low-temperature PGE deposits suggests syn-to postmagmatic crystallization or redistribution of PGE by hydrothermal fluids. The results obtained to date in a new study suggest that the Platreef at Sandsloot is a complex PGE deposit that has been subject to a number of different processes during its development.

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The analytical results of a total of 205 metabasic specimens from 10 palaeomagnetic sites collected from Oscar II Land in Western Spitsbergen are presented. Petrographic, structural and palaeomagnetic data all demonstrate that the pre-Caledonian ferromagnetic fabric of the metabasic rocks has been extensively reoriented and intensively remineralized. New in situ laser ablation inductively coupled plasma mass spectrometry 40 Ar/ 39 Ar age determinations suggest that the host rocks have been subject to three resetting events during the 426 – 380 Ma (Caledonian sensu lato ), 377 – 326 Ma and c. 300 Ma intervals. The latter two resetting events coincide in time with the Barents Shelf-wide rift-controlled subsidence events. The derived palaeomagnetic data do not fall on the expected apparent polar wander path of Laurussia for syn- to post-Caledonian time. Consequently, four models invoking palaeogeographical great and small circle rotations, regional tectonism involving thrusting and normal listric faulting have been investigated to account for this lack of correspondence. The palaeomagnetic data do not lend support to reconstructions linking Western Svalbard with Pearya but point instead to the importance of listric faulting related to the opening of the North Atlantic Ocean that modified the geometry of the West Spitsbergen Fold and Thrust Belt. Supplementary material: (1) Field characteristics of metabasic sites, (2) detailed description of applied rock magnetic and palaeomagnetic procedures, (3) microscopic images of investigated geochronological samples, (4) in situ LA-ICP-MS 40 Ar/ 39 Ar isotopic age determination results, (5) microscopic, SEM and BSE images of investigated metabasites, and (6) anisotropy of magnetic susceptibility are available at https://doi.org/10.6084/m9.figshare.c.3673924 .