Cobalt and Nickel Content in Pyrite from Gold Mineralization and Sulphide Facies Banded Iron Formation, Dickenson Mine, Red Lake, Ontario; Implication for Ore Genesis

Abstract

<p> The East South C (E.S.C.) ore zone at the Dickenson Mine, Red Lake, is a major auriferous banded sulphide orebody which cross-cuts sulphide facies banded iron formation (S.F.B.I.F.) near its eastern termination. Pyrite was obtained from sulphide-rich portions of the ore zone as well as from sulphide-poor E.S.C. mineralization not spatially associated with S.F.B.I.F., S.F.BI.F., shear zone hosted mineralization such as the 1492 and F ore zones, and from quartz-carbonate vein mineralization in the South C ore zone. Forty-three pyrite separates from the zones were analyzed by Atomic Absorption Spectrophotometry for Co and Ni, in order to determine the origin of the E.S.C. ore zone. The average Ni and Co content of these pyrites are as follows: S.F.B.I.F.,7.9 and 13.6 ppm respectively; remobilized S.F.B.I.F. 10.3 and 13.6; carbonatized S.F.B.I.F. 10.9 and 22.6; South C 14.9 and 50.6; 1492 zone 34.1 and 28.4; F-zone 11.2-27.6; sulphide-poor E.S.C. 26.2 and 48.4 and sulphide-rich E.S.C., 17.91 and 16.63.</p> <p> High and variable Co values were found to be associated with carbonate-rich samples, irrespective of the type of mineralization and low and similar Co values were found in all carbonate-poor samples irrespective of their origin. Therefore, the Co content of pyrite cannot be used as a discriminant of genetically dissimilar pyrite. The Ni content in pyrite from S.F.B.I.F. is low and constant, while in shear zone and vein mineralization it is higher and more variable. The E.S.C. ore zone has similar values to that found in the epigenetic mineralization, however, a few sulphide-rich samples are similar to those found in S.F.B.I.F., suggesting a bimodal source of sulphide for the E.S.C.. It is proposed that the hydrothermal system which produced the E.S.C., 1492, F and South C ore zones, locally incorporated sulphides from the S.F.B.I.F. to produce the sulphide-rich mineralization found at the eastern extremity of the E.S.C. ore zone.</p>