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 SnO2= 96–100 wt. %, with the sum FeOtotal, TiO2, WO3, Ta2O5, Nb2O5, In2O3, and UO2 content below 4 wt.%, while wolframite contains WO3= 71.5–74.5 wt.%, FeOtotal= 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 δ18O 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.

Abstract Beryl is usually found in granite-pegmatite systems. The addition of chromophore elements (V, Cr, Mn, Fe) into the crystalline structure favors color changes in beryl and thus generates some of the world’s expensive gems such as emerald, morganite, heliodor and aquamarine. The Massangana polyphasic batholith is a well-known cassiterite, wolframite and gems deposit in the Rondônia state. These metals and blue-gems (topaz and aquamarine) are located in feldspar-rich pegmatite granite bodies. The aquamarine crystals show color ranging from light- to medium-blue and display concentric growth zones. Electron-probe microanalyses revealed that the Fe is the main chromophore element, occupying the octahedral Al-site, while Na had an important role in the charge balance, inserted in the channel sites together with H2O. The irregular supply of Fe and Na during the nucleation and growth of aquamarine was the main cause for the color change. A fluid inclusion study indicated that the aquamarine growth under an aqueous fluid system (H2O-NaCl), with low salinity, low density and total homogenization temperature between 243º-315º C, is compatible with final temperatures in the pegmatite pocket zone.