The potential of flood basalts for hosting magmatic sulphide deposits: an application of exploration criteria to the Sverdrup basin, Nunavut, Canadian Arctic. (Geological Association of Canada 2000 Annual Technical Meeting Newfoundland Section).
The Sverdrup Basin is a northeast-trending, intracratonic basin that extends along the Arctic polar margin from the northern tip of Ellesmere Island to Prince Patrick and Melville Islands. It is 1300 km long and 400 km wide (after compressive deformation), and contains up to 13 km of Carboniferous to Tertiary strata. The basin originated during a Carboniferous-Early Permian rifling event accompanied by minor, episodic volcanic activity of alkaline character. Renewed rifling during the Cretaceous led to widespread magmatism in areas close to the Mesozoic depocentre. As a result, the sedimentary succession is intruded by a large number of mafic sills and dykes, most of which have not been mapped in detail. Volcanic successions, however, are included on recent 1:250,000 geological maps compiled by the Geological Survey of Canada, and their Cretaceous ages have in many cases been confirmed by [Ar.sup.40]/[Ar.sup.39] radiometric dating. The peak of volcanic activity was marked by the emplacement of flood basalts d uring the Albian and is contemporaneous with the age of the breakup unconformity in the Canadian Arctic Islands. The volcanic nature of the Alpha Ridge also suggests a tectonic link with the opening of the Arctic ocean. During the Late Cretaceous and earliest Tertiary, bimodal volcanic rocks were emplaced along the northern margin of the Sverdrup Basin. Following the waning of igneous activity, the basin was segmented and deformed during the Eurekan Orogeny, producing a foreland-style fold and thrust belt cut by major arches and high-angle reverse faults.
Volcanic and intrusive rocks of the Sverdrup Basin magmatic province remain virtually unexplored for their economic potential. A comparison of the attributes of the SBMP with the Noril'sk, Voisey's Bay and Midcontinent Rift regions, however, suggests many similarities. The following observations will be illustrated in the talk:
* The presence and eruptive style of the flood basalt province, and the evidence for widespread intrusion of basaltic magma during continental rifling.
* The possibility that major sills that could have acted as magma reservoirs or conduits.
* The geochemical evidence for a mantle plume origin and the selective crustal contamination of basaltic magmas.
* The presence of black shales and evaporites in the stratigraphic succession.
* The identification of major faults and their intersection with volcanic systems.
* The presence of magnetic anomalies that could represent large, deep mafic bodies.
* The possibility that lithospheric-scale faults acted as magma conduits.
The striking similarities to regions such as Noril'sk promote the Sverdrup Basin as a natural laboratory to test the exploration guidelines proposed by Naldrett (1992), for areas of flood basalt volcanism. We discuss the application of this exploration model to the SBMP, in light of the existing geochemical database, economic indicators, and remaining gaps in geoscience knowledge.