Laser probe /sup 40/Ar//sup 39/Ar and conventional K/Ar dating of illites associated with the McClean Uranium deposits, N. Saskatchewan, Canada

Conference · Mon Dec 31 23:00:00 EST 1984 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6917958

Bray, C J; Spooner, E T.C.; Hall, C M; York, D; Bills, T M; Krueger, H W

Mineralization at McClean occurs in elongate pods at the unconformity between the Athabasca sandstone sequence and the underlying Archean/Aphebian basement. Laser probe /sup 40/Ar//sup 39/Ar and conventional K/Ar dates were obtained on illites from the following environments (i) alteration halo around high grade U(-Ni-Co) mineralization, (ii) recrystallized sedimentary layers within the sandstone sequence, (iii) interstitial to quartz grains in sandstone, and (iv) regolith. The alteration halo illites gave ages between 1321+/-44 and 1002+/-33 Ma (n=20) which are in good agreement with published U-Pb dates on other U deposits in the area. One sample was analyzed twice, and gave a significant age difference of 20 Ma. Hence the age range is interpreted as being either a reflection of variable argon retentivity or due to continued hydrothermal activity (i.e. U mineralization) or a combination of both. Dates obtained on (ii), (iii) and (iv) were 1438-1038 (n=8), 1459-1113 (n=3) and 1482-1262 (n=6) Ma respectively. The older ages are in good agreement with a published Rb-Sr whole rock age of 1470 Ma on tuffaceous sediments from the Athabasca group. The spread to younger ages is interpreted as due to resetting by the hot (approx. 200/sup 0/C) formation water which transported the U, and variable argon retentivity. Diffusion studies on a single sample of illite from the sedimentary sequence indicate a low blocking temperature of about 140/sup 0/C and imply that there have been very low temperatures in the area for the last 1000 Ma.

• Research Organization: Univ. of Toronto, Ontario (Canada)
• OSTI ID: 6917958
• Report Number(s): CONF-8510489-
• Journal Information: Geol. Soc. Am., Abstr. Programs; (United States), Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Vol. 17; ISSN GAAPB
• Country of Publication: United States
• Language: English

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