Dear Dr. Majumdar:

You are on the right track. There are two types of U deposits, one called intramagmatic bound to alaskites and another named U metasomatites.

The first group hosts davidite, uraninite, thorite, bedafite, eudyalite, and pyrochlore and is categorized as low grade-large tonnage (e.g. Roessing 300 ppm U3O8). They are mainly located  in southern Africa. The second one encompasses uranium mineralizations which occur in structurally-deformed rocks altered by metasomatic processes, and associated with the introduction of Na, K and Ca. Their mineralogy resembles the afore-mentioned ones (U-, Th-, P- and REE –bearing minerals). Their reference deposits are located in Brazil and Cameroon.

Partial melting of a granodioritic source rock produced a restite-bearing I-type monzogranite in the magmatic stage. The granite ascended synorogenically.

Residual late-magmatic melts are enriched in K or Na causing

different generations of albitization which led to the replacement of plagioclase by albite, and the formation of a Zr-Ce-La mineralization.

The hydrothermal phase gave rise to the uraninite mineralization

U-albitite deposits are normally in S- and A-type granites.

Best regards

H.G.Dill

Dear Dr. Majumdar,

your question is as valid as the following: "Why Th, U enrichment in Grenville age (granulite facies) granitic rocks of South Africa?".   Why do we have a monazite lode up to 10 m thick in a granite-trondhjemite-enderbite-charnockite dyke at Steenkampskraal?

IN my experience a new approach, new geochemical tools are needed to answer these and related questions!

Regards,

Marco

Mr. Harald G. Dill

Your answer is really interesting...thanks for sharing your knowledge.

Dear all,

I am so thankful to you all for your valuable expert comments. I find that the granitoids in my study area is really a challenging;  right from geochronology (Pan-African) to lack of metamorphism and enrichment in LILE components.

Regards

D. Majumdar