RE: U in coal and minerals

["Karam, Andrew" <Andrew_Karam@URMC.Rochester.edu>]

>Also,precipitation of uranium minerals would probably be induced in the
>mixing zone of groundwaters with two different geochemistries.


You see exactly this effect in "roll-front" deposits.  Uraniferous,
oxygenated groundwater will reach a "redox front", where the environment
changes from oxidizing to reducing, causing uranium minerals to precipitate
into the matrix (sandstone, usually, I think).  Photos of these deposits
show a very sharp and obvious dividing line where precipitation began.  

Many papers by Langmuir talk about U geochemistry.  In addition, "Origin of
a South Texas Roll-Type Uranium Deposit" (Economic Geology, December 1978,
Reynolds and Goldhaber) discusses specifics of the geology and geochemistry
behind precisely this sort of behavior.  In fact, that entire issue of
Economic Geology is devoted to the geology and geochemistry of uranium.
Good reading, for anyone interested in this topic.

Andy
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