NICKEL ISOTOPE ABUNDANCES OF TYPE-I DEEP-SEA SPHERES AND OF IRON-NICKEL SPHERULES FROM SEDIMENTS IN ALBERTA, CANADA

Nickel isotope abundances were measured by ICP-MS in twenty-one whole, type I deep-sea spheres, in Ni-rich cores and oxide shells separated from three others, and in Fe-Ni alloy spherules from Alberta, Canada. The nickel isotopes in the whole deep-sea spheres are mass fractionate d from 0.4 to 2.4%/AMU. These values correspond to open system vaporiz ation losses of ii as high as 94% (relative). The degree of mass fract ionation correlates well with bulk nickel content in most cases. Taken together with published iron isotope data, the nickel isotope results indicate a pre-loss Fe/Ni ratio of about 12 for many spheres. Similar ratios are observed in the following types of meteoritic material: EL -chondrite metal; IA, IIE, IIIA, and IVA iron meteorites; and metal fr om pallasites and mesosiderites. Metal cores separated from three deep -sea spheres contain between 40 and 52% Ni, with mass fractionations r anging from undetectable to a high of 0.8%/AMU. Within experimental er ror, the degree of ii mass fractionation in each oxide shell was the s ame as that in the corresponding core. No mass-dependent isotopic frac tionation of nickel was observed in Ni-rich spherules recovered from A lberta sands of pleistocene age. In general, ii-rich samples have low degrees of isotopic fractionation which suggests that the most rapid v aporization of Ni occurs when both Fe and ii have been oxidized.