pp 309-314

The Origin of Gold Deposits— The Exhalite Theory

  • Robert W. BoyleAffiliated withGeological Survey of Canada

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The volcanic exhalite theory has had a long history. Initiated during the early studies of volcanism in the first quarter of the nineteenth century, the theory has been revived from time to time. Its most recent rebirth, concerning mainly the origin of massive sulfide deposits and iron-formations (both of which may be auriferous), is due to Oftedahl (1958), followed later by Stanton (1959, 1960), Sangster (1972), Hutchinson (1973), and numerous others. There are a number of variants of the exhalite theory; as conceived by most advocates of the theory the massive sulfide bodies are coeval with their enclosing rocks (generally volcanics or volcaniclastic sediments), and their constituent sulfides were laid down in a sedimentary manner as a result of exhalative volcanic processes, or as an alternative, the masses were deposited as a sulfide replacement of unconsolidated or slightly consolidated sediments. Later the deposits are supposed to have been metamorphosed and sheared or otherwise deformed, and the resulting textures in both the enclosing rocks and deposits are said to reflect these processes. Many thorny issues have been stirred up by this theory, most of which have not yet been adequately explained either by the syngencticists or hydrothermalists.