The auriferous quartz lode of the Veloso deposit, Quadrilátero Ferrífero of Minas Gerais, Brazil: geological characterisation and constraints from tourmaline boron isotopes

IF 1.4 4区地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS

Mineralogy and Petrology Pub Date : 2023-11-28 DOI:10.1007/s00710-023-00848-9

Júlia S. Pimenta, Alexandre R. Cabral, Glaucia Queiroga, Cristiano Lana, Miguel Tupinambá, Armin Zeh, Rogerio Kwitko-Ribeiro

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Abstract

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.

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巴西米纳斯吉拉斯州Quadrilátero Ferrífero Veloso矿床含金石英矿脉:电气石硼同位素的地质特征和限制

维罗索是欧鲁普雷图(Ouro Preto)众多的含金矿床之一，而欧鲁普雷图是17世纪初巴西淘金热的象征。本文介绍了地下地质填图的结果，并结合了电气石的硼(B)同位素研究，电气石是历史上Veloso矿床含金石英矿脉中的一种难以捉摸的矿物。它的矿脉在没有碎裂构造的寄主岩中呈角化特征。赋矿岩为橄榄岩，为变质条带状铁组。电气石是镁电气石和当地丰富的针铁矿晶体breccia-cementing口袋里,发生由硫化矿物的氧化。在富含针铁矿的岩穴中，金在空间上与电气石伴生。B同位素原位测量的δ11B值在−21 ~−9‰之间。该范围与报道的Passagem de Mariana矿床的电气石相似，该矿床是Quadrilátero Ferrífero东南边缘记录最好的含金矿脉矿床。电气石B同位素数据反映了来自变质沉积岩的含金地壳流体，其中可能包括非海相蒸发成分。

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来源期刊

Mineralogy and Petrology 地学-地球化学与地球物理

CiteScore

2.60

自引率

0.00%

发文量

审稿时长

1 months

期刊介绍： Mineralogy and Petrology welcomes manuscripts from the classical fields of mineralogy, igneous and metamorphic petrology, geochemistry, crystallography, as well as their applications in academic experimentation and research, materials science and engineering, for technology, industry, environment, or society. The journal strongly promotes cross-fertilization among Earth-scientific and applied materials-oriented disciplines. Purely descriptive manuscripts on regional topics will not be considered. Mineralogy and Petrology was founded in 1872 by Gustav Tschermak as "Mineralogische und Petrographische Mittheilungen". It is one of Europe''s oldest geoscience journals. Former editors include outstanding names such as Gustav Tschermak, Friedrich Becke, Felix Machatschki, Josef Zemann, and Eugen F. Stumpfl.