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Before the late 1960's, the VMS class of deposits was unknown. Bateman (1950) noted that the Flin Flon deposits formed "by hydrothermal replacement of a large shear zone by solutions that emanated from the granite magma reservoir". Lindgren (1933) presciently related VMS deposits to "iron-magnesium, high-temperature metasomatism". Both astutely placed VMS deposits in a single group, recognizing that the asymmetric alteration zones were genetically important. Exploration guides were based primarily on proximity to "granite sources" and "appropriate structures". Replacement processes best explained their paragenetic, structural and compositional relationships. In the late 1950's Knight and Oftedahl presented the heretical view that the stratiform nature of these orebodies indicated a syngenetic origin. Ten years later, Stanton, Roscoe, Hutchinson and Gilmour described attributes that engendered (reluctantly) a paradigm shift to the syngenetic model. The careful observations but apparently erroneous interpretations of earlier workers were "explained" (sic) using the new theory. The syngenetic model was zealously adopted in the late 1960's; exploration successes were attributed to its application at Noranda and Timmins. The careful observations made by earlier workers are still key exploration guides but the interpretations have changed! "Granite bodies" became synvolcanic heat sources and possible metal sources. The "controlling" faults are synvolcanic conduits for the discharging metalliferous fluids. The alteration assemblages are products of regionally metamorphosed syndepositional Fe-Mg metasomatism. "Impregnated siliceous tuffs" are volcanogenic sediments, formed contemporaneously with sulfide precipitates. The syngenetic model was irrevocably validated in the 1980s by the discovery of active high-temperature, sulfide-producing vents on oceanic spreading ridges. This research has validated many earlier interpretations. Sulfide replacement processes abound, with much of the mineralizing process occurring below the sea floor, within the sulfide mounds that grow by "inflation", via a complex history of precipitation, re-dissolution, replacement and displacement. Mg- alteration is generated from progressively heated seawater, but Fe- alteration forms from the high-temperature metalliferous fluid, as early workers suggested! Research on modern systems shows that early interpretations were partially correct and the resultant exploration guides still applicable.

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