SML 434 was taken out to enable making a re-assessment of the economic potential of exposed molybdenite-scheelite mineralisation first identified along the southern shores of Spilsby Island during 1963. There, outcropping equigranular Lower Proterozoic granite basement forms a sheet-like body outlining a gently south-eastwards plunging synclinal trough. Quartzitic lenses, veinlets and aplitic dykelets are abundant, and are thought to follow fractures of small-scale fault zones formed after consolidation of the granite. The subject metalliferous minerals occupy six distinct syngenetic modes of occurrence within the relatively fresh and unaltered granitic host rock and these lesser structures.The current investigations by Abadon Holdings consisted of their consultants' relogging of the Kennecott Explorations / SADM diamond drill cores, which covered the island on a 1000 foot grid spacing, plus detailed geological mapping of the known mineralised zone and reconnaisance geological mapping of the entire island, infill rotary percussion drilling of the mineralised syncline (7 holes, total 1000 feet), and detailed petrographic studies of drill core and cuttings samples. This work has clearly identified a magmatic origin for the deposits. The granitic melt appears to have intruded an older metamorphic complex along planes of weakness nearly parallel to the metamorphic banding, and then solidified into equigranular and porphyritic varieties of rock with which the molybdenite-scheelite minerals became intimately associated, via late-stage circulation of hydrothermal fluids along fracture zones and subsequently into intergranular open spaces caused by cooling contraction of the intrusive mass. The aplitic dykes seem to have been intruded during the same episode, as indicated by their field relationships with the granite, whereas the unmineralised pegmatite dykes must have been intruded later, as construed from their offsets to each other and their cutting relationships to the aplitic dykes.