Sediment hosted lead–zinc deposits of the Neoproterozoic Bambuí Group and correlative sequences, São Francisco Craton, Brazil: A review and a possible metallogenic evolution model

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• 作者：Aroldo Misi ; Sundaram S.S. Iyer ; Carlos Eduardo S. Coelho ; Colombo C.G. Tassinari ; Washington J.S. Franca-Rocha ; Ion&#xe1 ; de Abreu Cunha ; Adriana S. Rocha Gomes ; Tolentino Fl&#xe1 ; vio de Oliveira ; Jo
• 关键词：Proterozoic Pb– ; Zn deposits ; S&#xe3 ; o Francisco Craton ; Isotopes ; Fluid inclusions ; Metallogeny
• 刊名：Ore Geology Reviews
• 出版年：2005
• 期刊代码：66_01691368
• 类别：ear
• 出版时间：2005
• 卷：26
• 期：3-4
• 页码：263-304
• 文件大小：2037 K

摘要

The Proterozoic sediment-hosted Zn–(Pb) sulfide and non-sulfide deposits of the São Francisco Craton, Brazil, are partially syn-diagenetic and epigenetic and were probably formed during extensional events. The majority of the deposits occur within shallow water dolomites. The Pb isotopic data of sulfides are relatively homogeneous for individual deposits and plot above the upper crust evolution curve of the Plumbotectonic model. Some of the deposits are characterized by highly radiogenic lead (²⁰⁶Pb/²⁰⁴Pb ≥ 21) originating from the highly radioactive crust of the São Francisco Craton. Pb and S isotopic data suggest the sources of metal and sulfur for the deposits to be the basement rocks and seawater sulfates in the sediments, respectively. The relatively high temperatures of formation (100 to 250 °C) and moderate salinity (3%to 20%NaCl equiv.) of the primary fluid inclusions in the sphalerite crystals suggest the participation of basinal mineralizing fluids in ore formation. The steep paleo-geothermal gradient generated by the radioactively enriched basement rocks probably assisted in heating up the circulating mineralizing fluids.