An unusual occurrence of gypsum-anhydrite at Falkland, British Columbia, that supplied more than 1 250 000 tons of commercial gypsum between its opening in 1926 and its closing in 1956, has been considered to be of hydrothermal replacement origin. Evidence is here presented to show that the gypsum-anhydrite bodies were originally deposited as part of a sedimentary sequence and that they have "intruded" into their present positions as lenses and smears by plastic mobility along well-marked fault zones that supplied avenues of migration rather than conduits for sulphate-rich solutions.

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