Mineral chemistry and oxygen isotope studies on Sn (±W) mineralization from Pedra Branca Granite Massif, Central Brazil

Abstract

Central Brazil hosts Paleo-Mesoproterozoic A-type granitic suites related to the Goiás Tin Province (GTP) that contain Sn ( ± W, Nb-Ta, REE) mineralization associated with greisen, veins, and small pegmatite bodies. The Pedra Branca granite massif (1.77–1.74 Ga) is the main representative of GTP, marked by important cassiterite ( ± wolframite) contents. The cassiterite contains SnO 2 = 96–100 wt. %, with the sum FeO total , TiO 2 , WO 3 , Ta 2 O 5 , Nb 2 O 5 , In 2 O 3 , and UO 2 content below 4 wt.%, while wolframite contains WO 3 = 71.5–74.5 wt.%, FeO total = 14.3–17.4 wt.% and MnO = 6.3–9.9 wt.%, as well as Sn, Ca, Ti, Ta, Nb, Pb, In, and U as trace elements. The δ 18 O data on the quartz-cassiterite pair (quartz = 9.4–10.4‰, cassiterite = 2.6–2.9 ‰) from greisen reveal a magmatic-hydrothermal signature with calculated crystallization temperatures between 410 and 485°C. However, during the Neoproterozoic Brasiliano/Pan-African Orogeny (800–500 Ma), all lithologies and ore sites were subjected to flattening, fragmentation, and mylonitic deformation. Fluid inclusion data revealed the presence of low-salinity aqueous solutions with homogenization temperatures between 215 and 100°C related to Neoproterozoic deformation. Finally, during the Phanerozoic, prolonged erosive produced Sn ( ± W)-rich alluvium around the Pedra Branca granitic massif.