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sandstone. (E) Pervasive Kln 1 alteration in the sandstone filling well-developed secondary
porosity between detrital Qtz 0 grains. (F) Late Src 2 alteration replacing Kln 1 in sandstone.
The uranium mineralization was not observed in the overlying Coronation sandstone.
Ayres et al. (1975) observed minor uranium mineralization occurring within the Coronation
sandstone, close to the unconformity with the underlying mineralized Koolpin Formation.
4.5.1.2.4. Post-Ore alteration
Post-ore alteration in the basement rock is characterized by the occurrence of thin
veinlets of Chl 3 chlorite cutting through the syn-ore alteration assemblage. Late Kln 2
kaolinite alteration obliterates the pre-ore and syn-ore mineral assemblage (Fig. 4.9F).
Backscattered electron images indicate that U 1 uraninite is coarsely mottled and areas of
apparently pristine uraninite coexist with finely pitted altered U 2
uraninite. Post-ore
alteration in the Coronation sandstone is reflected also by the presence of minor Src 2
sericite that locally replaces Kln 1 kaolinite (Fig. 4.10F). Extensive secondary uranium
mineralization has been previously described associated with the overlying Coronation
sandstone (e.g. Valenta, 1991) (Fig. 4.3).
4.5.2. Crystal chemistry of the alteration minerals
4.5.2.1. Coronation Hill uranium deposit
4.5.2.1.1. Uraninite Crystal Chemistry
Electron microprobe analysis and backscatter images indicate that U 1 and U 2
uraninites have been variably altered to different forms of uranyl-silicates and have variable
U, Pb, Fe, Mg, Mn, and Ca contents (Table 4.1). These uraninites show considerable
variation in reflectance (Figs. 4.6E and 4.6F), suggesting significant heterogeneity in their
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