Gold particle chemistry and vein architecture in the Serrita–Salgueiro District, Western Transversal Zone of the Borborema Province, Brazil
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Abstract
Gold occurrences are distributed across the Serrita-Salgueiro District in the western part of the Transversal Zone, Borborema Province, Brazil. The host rocks are sulfide quartz veins in metasedimentary rocks attributed to the Salgueiro Complex and quartz-monzodiorites, granodiorites, and tonalites of the Serrita Suite. The Au-Ag-(As) and Au-Pb-(Cu) mineralizations in the Salgueiro and Serrita areas of the Salgueiro-Serrita District are hosted in quartz veins arranged in fractures and faults of extensional systems, sheeted veins, and hydrothermal breccias, which range from 0.1 to 1.5 meters in thickness. These veins are vertical to sub-vertical and oriented in an east-west (E-W), northeast-southwest (NE-SW), and north-northwest-southeast (NNW-SSE) direction. In the Salgueiro area, free gold is included in pyrite, chalcopyrite, arsenopyrite, hematite, and martite. In contrast, in the Serrita area, gold occurs alongside pyrite, chalcopyrite, and centimetric galena. Gold particles from the Salgueiro area exhibit Au contents ranging from 44 to 92.5 wt%. Au and 6.8 to 51.5 wt% of Ag. In Serrita, the Au content ranges from 74.4 to 94.7 wt%, and the Ag content ranges from 6 to 22 wt%. The fineness of Au varies from 770 to 930 (with an average of 875) in the Serrita area, and in Salgueiro, it ranges from 461 to 930, with an average value of 707. The chemical variations and hydrothermal halos next to granitic associations favor the contribution of magmatic-hydrothermal fluids. However, major shear zones close to deposits, chlorite-carbonate halos in metasediments, favor orogenic gold deposits at shallower emplacement. Recognizing hybrid fluid sources such as magmatic and metamorphic hydrothermal could enhance the understanding of gold deposition, which has implications for exploration strategies in similar geological settings.
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