Abstract: The distribution of uranium in a suite of variably deformed and metamorphosed rocks from the leucocratic member of the Glendessarry syenite has been determined using the fission track method. The uranium content of the magma increased during crystallization and uranium was concentrated in accessory minerals such as monazite, zircon, sphene, allanite, apatite, and microinclusions of a Zr- and Ti-rich phase. Contamination of the magma by pelitic metasediment enhanced the uranium content and monazite and zircon formed instead of sphene, allanite, and apatite.

Evidence of subsolidus uranium mobility in late stage magmatic or metamorphic fluids is presented here and shows: (a) Intracrystalline redistribution of uranium, especially in grains of sphene. (b) Intergranular mobility in a fluid phase, which affected the uraniferous accessory minerals in several ways.