Exploration carried out by North Broken Hill under fairly thick Cainozoic cover in the Sedan - Cambrai district initially sought possible economic deposits of epithermal base metals associated with known basic and ultrabasic rocks of the Black Hill igneous intrusion. After the discovery of magmatic sulphide minerals by early diamond drilling, the emphasis shifted to exploration for economic copper - nickel sulphides deposited in settings likely to mimic those found in the Zambian Copperbelt and Sudbury, Ontario, layered irruptives. A variety of prospecting techniques were tried, including re-interpretation of previous aeromagnetic data plus limited auger drilling and ground magnetic, IP and gravity survey traverses, in repeated attempts to delineate plugs and sills of gabbro and lesser norite that intrude the local Cambrian Kanmantoo Group sediments. Only the detailed ground magnetics proved broadly useful for defining drill targets. The ensuing drilling addressed an interpreted magnetic layer within the norite intrusions which was considered to lie not at, but some distance inside, the outer (or lower) intrusive contact with the country rocks (predominantly biotite schist, with associated metamorphosed Precambrian quartz diorite, granitic gneiss, granulite and pegmatite). 19 diamond drillholes totalling 4424.6 m were put down at Black Hill and near the Marne River at Cambrai to test selected magnetic anomalies. Drill cores from 6 of the holes disclosed finely disseminated sulphides including chalcopyrite, pyrrhotite, pyrite and molybdenite within the more basic differentiates, usually accompanied by magnetite in quantities sufficient to explain the geophysical response. Very low grade copper mineralisation of this kind was found in holes S1, S2b, S5, S10, S11 and S19 (best values found in S11, where there was 5% disseminated sulphides including 2% chalcopyrite over the depth interval 276.8-301.4 m, with 2.7 m below 298.1 m assaying 0.4% Cu and 0.1 % Ni (the latter as exsolved pentlandite and millerite present within pyrrhotite).