Nature and evolution of paleoproterozoic Sn and rare metal albitites from Central Brazil : constraints based on textural, geochemical, Ar-Ar, and oxygen isotopes
Economic and subeconomic concentrations of Sn, In, rare earth elements (REE), Ta, and Nb
are known in Central Brazil, in the Goias Tin Province. The Sn-P enriched albitites studied in this paper
occur in sharp contact with peraluminous granites of the Aurumina Suite (2.0–2.17 Ga) and schists of
the Archean to Paleoproterozoic Ticunzal Formation, as dikes or lenses from late-stage magma of the
peraluminous magmatism, probably in granite cupolas. Geological, petrological, and isotopic studies
were conducted. The albitites consist of albite, quartz, cassiterite, apatite, K-feldspar, and muscovite,
and have magmatic texture, such as alignment of albite laths, and snowball texture in quartz, apatite,
and cassiterite. They are enriched in Na2O, P2O5, Sn, Ta, and Nb (Ta > Nb), and depleted in CaO,
K2O, TiO2, MgO, Sr, Ba, Th, and REE. 40Ar/39Ar in muscovite gave a plateau age of 1996.55 ± 13 Ma,
interpreted as approaching the crystallization age. Oxygen isotope data in albite-cassiterite pairs
resulted in an equilibrium temperature of 653–1016 ◦C and isotopic fluid composition of 8.66–9.72h.
They were formed by crystallization of a highly evolved and sodic granitic magma. This study has
implications for Central Brazil’s economic potential and offers better understanding of tin behavior
in rare, evolved peraluminous granitic magmas
