LE3 .A278 2011

2011

Raeside, Robert

Acadia University

Master of Science

Masters

Geology

Earth & Environmental Sciences

The Horton Group in the Maritimes Basin hosts a uranium (U) prospect at Three Mile Plains, near Windsor, Nova Scotia. Since its discovery in 1978, and largely because of a U exploration moratorium passed in 1981, the mineralogy and geochemistry of the deposit are inadequately understood. This study investigates the geochemistry of the Three Mile Plains U occurrence to determine what other metals exist within the deposit and whether they exhibit zoning like other U roll front deposits. Sedimentary strata of sandstone, mudstone and shale of the Cheverie and Horton Bluff formations were logged, sampled, and analyzed for 37 major and trace elements using an aqua regia digestion. Over 1100 rock samples from 16 drill cores through the deposit illustrate that several additional elements (Mo, Cu, As, Se, V and Ni) exhibit anomalous concentrations, and could serve as pathfinder elements in future exploration. At the same time, these elements may also pose human health and/or environmental risks. Petrographic examinations reveal close associations between U mineralized zones and disseminated pyrite and hematite, biotite, and calcite cement. The textural relationships amongst these minerals suggest that the host rocks have undergone a complex series of redox reactions during authigenesis and diagenesis. Oxidation likely occurred due to the influx of meteoric water, possibly during intense weathering episodes. Periods of reduction were probably driven by the maturation of organic matter in the underlying Horton Bluff Formation. These redox episodes were likely important mechanisms for heavy metal entrapment in the Horton Group. Petrographic data do not preclude the remobilization of U today, possibly derived from the weathering of local rocks with anomalous U concentrations. Fa 0

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