Chemical dating uraninite
It is malleable, ductile, and slightly paramagnetic.When exposed to air, uranium metal becomes coated with a layer of oxide.However, as this event altered the ∼1.24–1.20 Ga uraninites and as spot ages of the altered grains yield ages largely between ∼1.24 and 0.96 Ga, it is reasonable to place this event between the second and third stages of uranium mineralization/mobilization at ∼1.20 Ga and ∼1.01 Ga, respectively.The last event that took place at ∼1.01–0.96 Ga most likely represent an episode of recrystallization/alteration of existing uraninite leading to complete Pb-loss and resetting of the isotopic clock.The ∼1.24–1.20 Ga event appears to be somewhat enigmatic in the context of well-known geological events in the area.However, based on some very recently published data, we interpret this to be a post-peak metamorphic (∼1.37–1.35 Ga) hydrothermal event or even a new metamorphic event, hitherto unknown.Uranium Properties: Uranium generally has a valence of 6 or 4.
The discrete events deciphered from uraninite in the Samarkiya area can also be broadly linked to some major magmatic-metamorphic events, identified from other independent studies, in the ADFB.
Acids will dissolve the metal, but it is not affected by alkalis.
Finely divided uranium metal is attached by cold water and is pyrophoric. Uranium and its (uranyl) compounds are highly toxic, both chemically and radiologically.
Uraninite occurs as inclusions in the major rock forming minerals, viz. Based on the shape, location in the host mineral (well inside/at the grain boundary/along or connected to micro-cracks etc.) and association with other secondary uranium minerals, uraninites are classified into different groups, which are compositionally distinct, barring some exceptions.
Integrating texture, geochemistry and in situ electron probe dating we propose that in addition to an old event at ∼1.88 Ga in the basement rocks, there are two major events of uraninite formation at ∼1.24–1.20 Ga and ∼1.01–0.96 Ga in both the basement and supracrustal rocks.