NICKEL ISOTOPES IN THE DULUTH COMPLEX: EVIDENCE FOR HIGH TEMPERATURE ISOTOPIC FRACTIONATION DURING THE FORMATION OF CU-NI-PGE SULFIDE DEPOSITS
Initial results show a spread of δ60/58Ni values from -0.97 ‰ to -0.02 ‰, within the range of Ni isotopic values reported previously [1,2]. The least fractionated values come from unmineralized mafic intrusives (-0.02 ‰), while massive sulfides show values around -0.97 ‰. Till samples record intermediate values ranging from -0.50 ‰ to -0.17 ‰ and weathered surface samples, containing up to 15 % sulfides, range from -0.23 ‰ to -0.10 ‰. The isotopic data suggest a clear isotopic fractionation trend in the Duluth Complex from unfractionated values close to zero for early crystallizing phases to highly fractionated massive sulfides, accumulated at some later stage. Ni isotopic values for till and mineralized surface samples, and their correlation with known deposits, may be useful in distinguishing regions overlying Cu-Ni-PGE mineralization from barren areas. Data may also help to identify the entry point of the mineralizing magma based on the location and isotopic signature of individual sulfide deposits.
1. Wasilenski et al. (2015) Ni isotope fractionation during sorption to ferrihydrite: implications for Ni in banded iron formations. Chemical Geology (accepted for publication)
2. Hiebert RS., Rouxel, O., Houlé, MG., Bekker, A. (2014) Ni isotope fractionation between komatiite and sulfide mineralization at the Neoarchean Hart deposit, Abitibi greenstone belt, Canada. Geological Society of America Abstracts 46: 467