Abstract

Mineral exploration for volcanogenic massive sulphide deposits in the Buchans area of central Newfoundland is hindered by thick and widespread Quaternary overburden comprising glacial, glaciolacustrine, glaciofluvial, and resedimented deposits. Mapping of striations and indicator erratics suggests that the area was affected by four ice-flow events: I, southward; II, northeastward and westward to southwestward; III, southward; and IV, northeastward and southwestward. Vertical and areal distributions of lead, copper, and zinc indicate that till and glaciolacustrine sediments overlying sulphide deposits can be enriched in mineralized debris. Near mines at Buchans surficial debris-flow deposits contain much material derived from the Topsails igneous terrane and are generally impoverished in mineralized debris. Southwest of Buchans, however, they can be enriched. Mineral exploration in the Buchans area must take into account that (i) sulphide-rich debris in till does not reflect only the youngest ice-flow event; (ii) glaciolacustrine sedimentation and resedimentation can result in burial of older sediments containing mineralized debris, in the redistribution of that debris, and in the geochemical masking of subcropping ore deposits; (iii) dispersal of sulphide debris during resedimentation is not necessarily related to ice-flow directions indicated by striations; (iv) a geochemical dispersal train originating at Buchans reflects both southwestward glacial transport and later redistribution of mineralized debris within debris-flow and glaciolacustrine deposits; and (v) marked geochemical variations with depth can occur with small variations in sampling depth, reflecting change in provenance and depositional process. The depositional and ice-flow model developed for the Buchans area likely has wider application in central Newfoundland.

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