Abstract
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 8.66–9.72‰. 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.
Highlights
Albitites are uncommon rocks with usually more than 70–80% of albite
This type can be recognized by typical textures, such as albite inclusions along growth planes in quartz or other mineral, called snowball texture, or the alignment of albite laths in the rock matrix, which is interpreted as flow texture
This paper aims to study albitites that occur in a restricted area, i.e., the Goiás Tin Province, located in Central Brazil [12]
Summary
Most of the known albitites worldwide have their origin attributed to the action of hydrothermal fluids on granites [1,2,3] In this case, quartz and K-feldspar are leached by Na-rich fluids, in an albitization process, which is sometimes related to greisenization from evolved granites [4,5]. Albitites are formed by direct crystallization from Na-rich magmas, generally related to specialized and rare-metal granites [6,7,8,9]. This type can be recognized by typical textures, such as albite inclusions along growth planes in quartz or other mineral, called snowball texture, or the alignment of albite laths in the rock matrix, which is interpreted as flow texture. In addition to textural studies, geochemical characterization of associated granites is crucial to distinguish sodic enrichment in the magmatic stage from metasomatic enrichment [7,9,10,11]
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