Geology dating in austarlia

There are two discrete uranium orebodies at Koongarra, separated by a 100 m wide barren zone (see Figure 2).

The main (No.1) orebody has a strike length of 450 m and persists to 100 m depth.

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As with other radiometric “dating” methods, the U-Pb and Pb-Pb isochron methods have been questioned in the open literature, because often an excellent line of best fit between ratios obtained from a set of good cogenetic samples gives a resultant “isochron” and yields a derived “age” that has no geological meaning.

At the Koongarra uranium deposit, Australia, there is ample evidence of open system behaviour, or repeated migration, of U and Pb — ore textures, mineral chemistry, supergene alteration, uranium/daughter disequilibrium, and groundwater and soil geochemistry.

The open system behaviour of the U-Th-Pb system is clearly the norm, as is the resultant mixing of radiogenic Pb with “common” or background Pb, even in soils in the surrounding region, apparently even up to 17 km away!

Because no geologically meaningful results can be interpreted from the U-Th-Pb data at Koongarra (three uraninite grains even yield a Pb “age” of 0 Ma), serious questions must be asked about the validity of the fundamental/foundational basis of the U-Th-Pb “dating” method.

But the method does not always give the “expected” results, leading to fundamental questions about its validity.

Last modified 21-Aug-2017 08:16