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The Trindade Island is located in the South Atlantic Ocean, 1170km from the Brazilian coast and represents the eastern end of the submarine E-W Vitória-Trindade Chain. This is interpreted as the Trindade plume track beneath the South American plate during the Cenozoic. Almeida (1961) recognized five volcanogenic successions at Trindade in decreasing age: the Trindade Complex (TC) and the Desejado (DF), Morro Vermelho (MV), Valado (VF) and Paredão (PF) formations, composed of nephelinitic to phonolitic effusive-pyroclastic deposits, dykes and necks. Here, we present new 40Ar/39Ar ages and re-evaluation of available 40K/40Ar* data that, coupled with previous petrological information, allowed us to reconstruct the volcanic history of the island (i.e., 3.9-0.25Ma) distinguishing near synchronous volcanic episodes and solving several stratigraphic uncertainties reported in the literature.The geochronological dataset show that the nephelinitic-phonolitic volcanism at Trindade was discontinuous throught time, being marked by periods of high volcanic activity and periods of quiescence, which suggests variable melt production and eruption rates. The peak of the volcanic activity occurred between 3.9 and 2.5. Ma (i.e., Lower Pliocene to Lower Pleistocene) that is represented by the TC, which correspond to the largest volume of volcanic deposits preserved in the island. The volcanic activity slows down progressively from 2.5. Ma to cease at ca. 1.6. Ma, period that is represented by the DF. This volcanism was followed by a quiescent period that lasted until the ephemeral nephelinitic volcanism of the MV (no age), VA (no age) and PF (ca. 0.25. Ma). Thus, the volcanic activity in Trindade was ceased completely at ca. 0.25. Ma, event registered in the uppermost volcanic deposits of the PF and that represents the last volcanic activity in the Brazilian territory.

Piaba is an orogenic gold deposit (~ 3.5 Moz) of the São Luís cratonic fragment in north-northeastern Brazil. The deposit is epizonal–mesozonal and associated with the development of a subvertical strike–slip fault that cut across Rhyacian metavolcano-sedimentary rocks and granitoids. The metavolcano-sedimentary sequence comprises carbon-bearing schists, andesite/dacite, ultramafic rocks and felsic tuffs formed at 2240 ± 5 Ma to 2227 ± 33 Ma that were intruded at 2214 ± 3 Ma by fine-grained, subvolcanic granophyric granodiorite. Whole-rock geochemistry indicates that the hosting metavolcano-sedimentary sequence formed in a subduction-related (arc, back-arc?) setting, which has previously been interpreted as the early-arc stage of an accretionary orogen (2240–2214 Ma) that was followed by voluminous subduction-related calc-alkaline arc magmatism (2168–2145 Ma) and by a collisional phase (2100 ± 15 Ma) that produced several bodies of peraluminous granites. The hydrothermal alteration of the host rocks produced early, distal carbonization and hematitization and proximal, ore-related chlorite–sericite–carbonate–sulfide alteration.Two styles of mineralization, occurring in association, are present: (1) a network of thin quartz ± sulfide veinlets and subordinate narrow breccia veins with refractory- to free-milling gold dissemination in hydrothermally-altered host rocks, and (2) subordinate low-sulfide Au-quartz veins with free-milling gold. Fluid inclusions and stable isotopes characterize the mineralizing solution as a relatively reduced (log fO2 = − 30 to − 35), neutral to slightly alkaline (pH 5 to 6.2), low-salinity (average 5% NaCl), aqueous-carbonic (XCO2 = 5 to 59 mol%, XH2O = 40 to 93 mol%, XN2 and XCH4 < 1 mol%) metamorphic fluid (δ18OH2O = + 5.5 to + 8.9‰, δDH2O = − 8 to − 69‰), and suggest that gold mineralization occurred at 250° to 330 °C and 1.25 to 2.8 kbar in response to phase separation and fluid–rock interactions that produced sulfidation and minor carb

Studies have been carried out of microstructures and related fluid inclusions in the MM1 and BA1 boreholes along the Azer fault in France. The results show that during the Triassic, the Cevenole margin was flushed by diluted waters with remaining circulating fluids at BA1 being halite-contaminated. The development of fluid-assisted structures in sediments shows that the fault was an avenue for fluids. Also, hot saline fluids partly originating from the deep basin percolated upward through cracks. At the base of BA1, the replacement of anhydrite by dolomite during burial marks the thermal reduction of sulphates by CH4 flowing up from Stephanian sediments. The dolomitised and silicified evaporites observed at BA1 and MM1, along with related sulphides, are geochemically similar to the Cevenole mineralisation. The source rocks for Pb-Zn ores can be found on continental margins, particularly along growth faults., Studies have been carried out of microstructures and related fluid inclusions in the MM1 and BA1 boreholes along the Azer fault in France. The results show that during the Triassic, the Cevenole margin was flushed by diluted waters with remaining circulating fluids at BA1 being halite-contaminated. The development of fluid-assisted structures in sediments shows that the fault was an avenue for fluids. Also, hot saline fluids partly originating from the deep basin percolated upward through cracks. At the base of BA1, the replacement of anhydrite by dolomite during burial marks the thermal reduction of sulphates by CH4 flowing up from Stephanian sediments. The dolomitised and silicified evaporites observed at BA1 and MM1, along with related sulphides, are geochemically similar to the Cevenole mineralisation. The source rocks for Pb-Zn ores can be found on continental margins, particularly along growth faults.

The Trepca Pb-Zn-Ag skarn deposit, estimated to have contained 29 000 000 t ore at 3.45% Pb, 2.30% Zn, and 80 g/t Ag, is located in the Kopaonik block of the western Vardar zone. The mineralisation, hosted by recrystallised limestone of Upper Triassic age, was structurally and lithologically controlled. Ore deposition was spatially and temporally related to postcollisional magmatism of Oligocene age (23-26 Ma). The deposit was formed during two distinct mineralisation stages: an early prograde closed-system and a later retrograde open-system stage. The principal ore minerals, galena, sphalerite, pyrite and minor chalcopyrite, were deposited from a moderately saline Ca-Na chloride fluid at around 350 degrees C. According to the isotopic composition of fluid inclusions in sphalerite, the fluid responsible for ore deposition was predominantly meteoric in origin. The 34-S isotope values of the sulphides, spanning between -5.5 and +10 per mille, point to a magmatic origin of sulphur. Ore deposition appears to have been largely contemporaneous with the retrograde stage of the skarn development. The post-ore stage involved precipitation of significant amount of carbonates, including travertine deposits, with mineralogical composition varying from calcite to siderite and all containing significant amounts of Mn. Decreased formation temperature and depletion in the REE content point to an influence of pH-neutralised cold groundwater and a dying magmatic system., The Trepca Pb-Zn-Ag skarn deposit, estimated to have contained 29 000 000 t ore at 3.45% Pb, 2.30% Zn, and 80 g/t Ag, is located in the Kopaonik block of the western Vardar zone. The mineralisation, hosted by recrystallised limestone of Upper Triassic age, was structurally and lithologically controlled. Ore deposition was spatially and temporally related to postcollisional magmatism of Oligocene age (23-26 Ma). The deposit was formed during two distinct mineralisation stages: an early prograde closed-system and a later retrograde open-system stage. The principal ore minerals, galena, sphalerite, pyrite and minor chalcopyrite, were deposited from a moderately saline Ca-Na chloride fluid at around 350 degrees C. According to the isotopic composition of fluid inclusions in sphalerite, the fluid responsible for ore deposition was predominantly meteoric in origin. The 34-S isotope values of the sulphides, spanning between -5.5 and +10 per mille, point to a magmatic origin of sulphur. Ore deposition appears to have been largely contemporaneous with the retrograde stage of the skarn development. The post-ore stage involved precipitation of significant amount of carbonates, including travertine deposits, with mineralogical composition varying from calcite to siderite and all containing significant amounts of Mn. Decreased formation temperature and depletion in the REE content point to an influence of pH-neutralised cold groundwater and a dying magmatic system.