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[Display omitted] • Epigenetic Pb-Zn ore in carbonates formed by mixing of various metalliferous fluids. • Sphalerite composition indicating complex metalliferous fluid:rock interactions. • Zoned mineralizing system with distal pyrite-related geochemical signature. • Rare example of Proterozoic Mississippi-Valley type Pb-Zn mineralization. The Proterozoic Vazante-Paracatu mineral belt hosts distinct styles of mineralization in carbonate rocks, including world-class hypogene silicate-zinc deposits in the south and sulfide Zn-Pb deposits in the north. This study focuses on the Morro Agudo District (Morro Agudo deposit and Bento Carmelo, Sucuri, and Morro do Capão occurrences). The genesis of the Morro Agudo sulfide deposit is controversial (i.e., syn -diagenetic or syn -orogenic), and little was known about the other occurrences. Ore is stratigraphically controlled within distinct dolomitic units of the Morro do Calcário and Lapa formations and structurally controlled at the Morro Agudo deposit along a NW normal fault system. Mineralization is characterized by multiple generations of sphalerite and galena, coeval with hydrothermal Fe-rich dolomite, pyrite, and quartz, which overprint micritic and sparitic dolomite and diagenetic pyrite. The mineralized zones comprises Cd and Hg within the high-grade Zn-Pb ore and Ag, As, Cu, Fe, In, Se, Sb, and Tl extending into the hydrothermal halos surrounding the orebodies. The sphalerite compositions encompass variable proportions of Zn (58.75–66.92 wt%), Fe (0.15–5.03 wt%), and Cd (0.18–0.94 wt%) grouped in five populations based on Cd-Fe ratios and principal component analysis. Sphalerite from various generations and locations in the orebodies and occurrences do not show any specific signature, suggesting episodic contribution of multiple fluids with distinct Fe and Cd contents. The whole rock lithogeochemistry revealed similar trace element signatures for the orebodies of Morro Agudo deposit and surrounding occurrences indicating, despite the textural differences, that these orebodies formed from similar mineralizing fluids and processes, except for the Bento Carmelo occurrence. This study shows clear evidence that the mineralization at the Morro Agudo deposit, Sucuri and Morro do Capão occurrences is epigenetic, forming after the diagenesis of the host carbonate succession, and may have involved progressive mixing of multiple fluids with distinct compositions that interacted with sulfur reservoirs in the dolomitic rocks, similar to other MVT districts worldwide. The Morro Agudo district is one of the rare examples of Proterozoic MVT districts, and this study brings new insights to the exploration of this type of mineralization in similar basins. [ABSTRACT FROM AUTHOR]

• The Montevecchio-Ingurtosu district was one of the largest Italian Pb-Zn-Ag producers. • New field, microscopic, microchemical, isotopic, and fluid inclusion data were obtained. • The Montevecchio deposit shows several affinities with the class of Ag-Pb-Zn veins in metasediments as defined by Beaudoin & Sangster (1992). • Ore textures and mineralogical-chemical features at all scales document a multistage process of mineralization postdating the emplacement of the 304 ± 4 Ma Arbus pluton, and occurring in a tectonically active regime. • The exact age of mineralization is not constrained, although it might be related to regional, large-scale shear deformation in a late-post-orogenic context. • At least part of the mineralization is associated with relatively low temperature (≦200 °C), high salinity (>20 wt% equiv. mass NaCl) fluids analogous to basinal brines. The Montevecchio-Ingurtosu district (SW Sardinia) was among the largest historical Pb-Zn producers of Italy, with significant Ag output, and yields of metallic byproducts such as Cd, Co, Cu, Bi, Sb, Ge, In, and Ga. Despite this importance, detailed descriptions of orebodies and mineral assemblages are surprisingly scarce and old. Here we summarize all previously available information and contribute new textural, microchemical, fluid inclusion, and C-O isotopic data deriving from a recent sampling of currently exposed orebodies. Mineralization occurs as steeply dipping veins extending for almost 20 km at the northern and western flanks of the Variscan Arbus pluton; veins are hosted in phyllites of the Arburese Unit close to the thermometamorphic aureole. Ore enrichments range from massive to coarsely nodular, stockwork and brecciated. Vein filling consists of siderite (locally Zn-rich), quartz, sphalerite, galena (remarkably rich in micro-inclusions), with accessory chalcopyrite, fahlore, bournonite, barite, and Ni-Co sulfarsenides. Vein assemblages may vary, even within a single vein, from sphalerite- to galena-dominated. Cu-rich assemblages (fahlore + chalcopyrite) were locally observed. Wallrock is affected by silicification, sericitization and pyrite dissemination. Sphalerite shows a complex mineral chemistry, with marked variations in Fe (0.08 to 8.9 mol% FeS) and in Cd contents (from <0.05 to >1 wt%). Trace element analyses (LA-ICP-MS) document the presence of measurable amounts of Ga, Ge, In, Ag, Ni, Co, Tl and Mo. Fahlore varies from the Sb (tetrahedrite) and the As (tennantite) endmembers, with Ag-rich compositions corresponding to Sb endmembers. The occurrence of Cd-rich tetrahedrite (up to 14.5 wt%) is remarkable. Fluid inclusion studies on sphalerite and quartz are in agreement with previous literature data, and indicate comparatively low (in the range 90°–130 °C) homogenization temperatures (T h) and high salinities (14 to 25 equiv. mass % NaCl); both microthermometric data and SEM/EDS analyses of decrepitated inclusions indicate the presence of Ca and K beside Na. Pressure correction to T h is presumably low (in the order of 10 °C), considering a hydrostatic pressure regime. Application of the sphalerite-based GGIMFiS thermometer provided temperatures in excellent agreement with fluid inclusion data for the Montevecchio mineralization. Isotopic data on Montevecchio carbonates define mildy negative δ13C PDB values (between −1 and −5 per mil), and a larger spread of δ18O SMOW values, between +14 and +20 per mil. Other isotopic data from literature include a limited set of δ34S values for galena, sphalerite and pyrite, and a fairly large body of Pb isotopic data on galena. Comparatively narrow ranges for sulfur isotope signatures suggest a homogeneous, possibly igneous, sulfur source, whereas the large spread in Pb isotope signatures reflects the large-scale character of the hydrothermal process and indicates that the Arbus pluton may have been just one of the sources of ore lead. The Montevecchio vein system shows affinities with other late to post Variscan European deposits. The nature of the mineralizing fluids at Montevecchio is analogous to low temperature, basinal brines, and typical of several regional-scale, late to post-Variscan hydrothermal events across Europe. Mineralization at Montevecchio obviously postdates the emplacement of the Arbus plutonic complex, but its exact age remains unknown.. [ABSTRACT FROM AUTHOR]