Abstract

Titanite, fersmite, pyrochlore-group minerals and romeite in two small dikes of relatively poorly fractionated pegmatite, located in the parent Hercynian Prasiva biotite granodiorite-granite, in central Slovakia, were generated by hydrothermal alteration of primary columbite, titanian ixiolite and niobian-tantalian rutile. The early titanite has elevated contents of Nb, Ta, Al and Fe, and the fersmite is very REE-poor. Pyrochlore, microlite, betafite, uranpyrochlore, uranmicrolite, stibiomicrolite, stibiobetafite, plumbomicrolite and several transitional compositions were identified in the next generation, most of them Si-bearing. The late romeite is considerably enriched in Nb, Ta, U and Si. The hydrothermal fluids mobilized Nb, Ta, Ti, U, Fe, Si, and probably also Ca and Na from the primary minerals of the pegmatite, but Sb and Pb must have been imported from an external source. The hydrothermal overprint is attributed to the same metamorphic-magmatic solutions that caused the nearby Sb+ or -Au and Pb-Zn-Sb sulfide deposits.

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