Veloso is one of numerous and poorly documented auriferous deposits of Ouro Preto, the town that symbolises the gold rush in Brazil at the turn of the seventeenth century. We present the results of underground geological mapping, combined with a boron (B) isotopic study of tourmaline, an elusive mineral in the auriferous quartz lode of the historical Veloso deposit. Its lode is characteristically brecciated in a host rock that shows no cataclastic fabric. The host rock is itabirite, a metamorphosed banded iron formation. Tourmaline is essentially dravite and locally occurs as abundant crystals in breccia-cementing pockets of goethite, formed from the oxidation of sulfide minerals. Gold is spatially associated with tourmaline in the goethite-rich pockets. In situ measurements for B isotopes yielded δ¹¹B values in the range of −21 to −9‰. This range is similar to that reported for tourmaline of the Passagem de Mariana deposit, the best documented auriferous lode deposit at the south-eastern edge of the Quadrilátero Ferrífero. The tourmaline B isotopic data reflect auriferous fluids of crustal origin that sourced B from metasedimentary rocks, which may include a non-marine evaporitic component.

维罗索 (Veloso) 是欧鲁普雷图 (Ouro Preto) 众多但文献记载很少的金矿之一，这座小镇象征着 17 世纪初巴西的淘金热。我们展示了地下地质测绘的结果，并结合了电气石的硼 (B) 同位素研究，电气石是历史悠久的维罗索矿床含金石英矿脉中难以捉摸的矿物。其矿脉在主岩中呈角砾状，没有碎裂构造。主岩是铁铁矿，一种变质带状铁矿。电气石本质上是透镁石，局部以丰富的晶体形式存在于针铁矿的角砾胶结袋中，由硫化物矿物的氧化形成。黄金在空间上与富含针铁矿的矿区中的电气石相关。B 同位素的原位测量得出的 δ ¹¹ B 值在 -21 至 -9‰ 范围内。该范围与 Passagem de Mariana 矿床报告的电气石范围相似，该矿床是位于 Quadrilátero Ferrífero 东南边缘的有据可查的含金矿脉矿床。电气石 B 同位素数据反映了地壳来源的含金流体，其 B 来源于变沉积岩，其中可能包括非海洋蒸发岩成分。