New evidence and possible origin of native iron in ophiolites of eastern Canada

THERMOMAGNETIC analysis has been used to detect traces of submicroscopic elemental iron in four bodies of Early Palaeozoic oceanic metabasalt (Fig. 1). The initial finding of iron in Newfoundland ophiolites1 is believed to be the first terrestrial discovery of native ferromagnetic metal through magnetism. A few rock samples in these four areas have unusually high Curie points indicating pure or nearly pure iron. In one basaltic pillow, previous magnetic evidence2 was confirmed by electron microprobe showing very fine Fe particles embedded in chlorite. We propose that such particles formed by reduction of olivine under water and became trapped in the chlorite host. Although native iron seems rare on Earth3,4, further suboptical discoveries through rock magnetism may be predicted. Such findings could prove valuable in identifying ancient oceanic crust generated in a reducing environment.