An overview of vis-nir-swir field spectroscopy - Spectral International

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2003, for Shea Creek; and Bruneton, 1993, for Cigar Lake). This alteration
typically envelops the main ore-controlling structures, forming plume-shaped or
flattened elongate bell-shaped halos that taper gradually upward from the base of
the sandstone (Hoeve and Quirt, 1987) Figure 70. Potassium, magnesium and
aluminum ratios are diagnostic of the different clay types.
Hydrothermal, ore-related alteration effects are superimposed on pre-existing
alteration assemblages, including the paleo-weathering alteration recorded by
the red-green profile below the basal unconformity, and the initial detrital clay
mineralogy that is locally preserved in silicified zones (Mwenifumbo et al., 2005).
This has led to confusion as to which process generated the red-green transition
at the basement-sandstone unconformity. Ore-related white clay alteration is
superimposed on the red hematitic paleo-weathering alteration (McDonald,
1980). Very dark coarse grained hematite alteration forms a cap over ore
deposits such as Cigar Lake (Andrade 2002).. This very dense, crystalline,
hydrothermal hematite alteration contrasts with the brick red, fine-grained
hematite that is interpreted as a detrital or very early diagenetic mineral, and is
intimately interlayered with clay minerals to form micro-laminae in oncoidal
hematite beds (Yeo et al., 2005a).
Figure 71 - Simplified mineral paragenesis of the Paleo- to Mesoproterozoic Athabasca, Thelon
and Kombolgie basins, after Figure 10.21 of Kyser et al. (2000). The ages of primary uraninite,
the first deposition of U in a given deposit, may be different for different deposits, hence U1
(~1500-1600) and U1' (~1350-1400) might both be primary in the Athabasca Basin. Depositional
ages in the Athabasca Group are Zv: U-Pb on volcanic zircon in Wolverine Point Formation, and
Os-Re: primary organic matter in Douglas Formation.
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