LITHOGEOCHEMICAL INSIGHTS INTO THE NI-CU-PGE PROSPECTIVITY OF MAFIC-ULTRAMAFIC LARGE IGNEOUS PROVINCES AND USES IN EXPLORATION TARGETING (Invited Presentation)

Large Igneous Provinces (LIPs) are large volume, short duration intraplate magmatic events that generate significant volumes of volcanic rocks (mainly flood basalts) and plumbing systems that may contain mafic dyke swarms, sill complexes, and mafic-ultramafic layered intrusions. The processes that form mafic–ultramafic LIPs also generated significant to world-class magmatic sulfide mineralization in some (but certainly not all) LIPs, as exemplified by the Noril’sk-Talnakh deposits in Russia (251 Ma Siberian Trap LIP), Cu-Ni-PGE mineralization of the Duluth Complex, Minnesota, USA (1114-1085 Ma Keweenawan LIP), the 1885-1865 Ma Raglan and Thompson deposits in Canada (Circum-Superior LIP) and Archean komatiite-hosted magmatic sulfide mineralization in the Yilgarn Craton of Western Australia (Eastern Goldfields and other Archean LIPs). These mineral deposits formed from fertile mantle-derived mafic magmas generated by high degree partial melting that ascended through the crust where they became sulfide-saturated, segregating immiscible Ni-Cu-PGE sulfide melts and generating ore deposits.

Different parts of LIPs may also be prospective and unprospective depending on variations in magmatic processes. Mantle source regions and magmatic processes change over time; hence, the prospectivity of a given LIP may vary both spatially and temporally even though differing sections of a LIP may have very similar geological and geophysical features. Lithogeochemistry provides insights into Ni-Cu-PGE prospectivity of individual sections of LIPs and the processes that controlled the S-saturation status of LIP magmas. Knowledge of these processes and the prospectivity of entire LIPs, subsections of LIPs, and different phases in the evolution of a LIP can be directly used in exploration targeting at regional and local scales. For instance, chalcophile element depleted units can be used to identify potential mineralization “upstream” in the plumbing system.

Here, we outline key lithogeochemical techniques and their uses in mineral exploration, including case studies of the 130-90 Ma High Arctic LIP in northern Canada and LIP events spanning 1070 to 409 Ma within the Arunta region of central Australia.