Abstract

The literature of ore deposits indicates that magnetite occurs in a large number of sulphide deposits as an epigenetic mineral. Tabulation of 130 deposits or districts shows that the common sulphides, listed in order of number of occurrences, are: chalcopyrite, pyrite, pyrrhotite, sphalerite, galena, arsenopyrite, bornite, and chalcocite. Many lesser sulphides such as molybdenite, pentlandite, marcasite, cubanite, enargite, tetrahedrite, and covellite, also occur less commonly. Hematite (specularite) is a common associate of magnetite in these deposits.Magnetite with sulphides occurs in deposits generally classified as of magmatic, pyrometasomatic, and hypothermal origin. It is practically absent in other types of deposits.Tabulation of the order of formation of minerals in 52 magnetite-sulphide deposits shows that magnetite is normally the first metallic mineral to form. This suggests that, as a rule, magnetite forms only at high temperatures, possibly at a temperature which under existing conditions inhibits the formation of sulphides. In a few deposits, however, magnetite is preceded by pyrite or less commonly by other sulphides. In exceptional examples, as at Kaveltorp, Sweden, a series of sulphides are reported as preceding magnetite in a complex order of paragenesis.Once formed, magnetite is evidently stable, as it shows only moderate evidence of replacement by later minerals.

First Page Preview

First page PDF preview
You do not currently have access to this article.