Abstract

The magnetic anisotropy of oriented sulfide samples from four massive sulfide ore (Ni–Cu) deposits associated with the Sudbury Irruptive and two sulfide deposits near Timmins, Ontario, is commonly well above 10%. This indicates that the anisotropy is mainly due to preferred orientation or to thin layering of random crystals of the strongly anisotropic magnetic pyrrhotite type Fe7S8 which occurs in all deposits sampled. The directions of the principal susceptibilities show patterns for most of the deposits indicating a consistent magnetic fabric within these deposits. The directions of the principal susceptibilities show varying degree of scatter, suggesting local modifications of the general patterns. In general the standard errors on the principal susceptibilities are only a few (< 5) degrees indicating that the magnetic fabric is of single origin and did not result from superimposed anisotropies. It is emphasized that in most cases, the magnetic fabric differs from deposit to deposit in the Sudbury area, suggesting that the fabric depends strongly on the geological environment of the deposits.

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