Hydrothermal alteration of volcanic rocks in Seival Mine Cu–mineralization – Camaquã Basin – Brazil (part I): Chloritization process and geochemical dispersion in alteration halos

Fontana, Eduardo; Mexias, André Sampaio; Renac, Christophe; Nardi, Lauro Valentim Stoll; Lopes, Rodrigo Winck; Barats, Aurélie; Gomes, Márcia Elisa Boscato

doi:10.1016/j.gexplo.2017.02.004

Cited by 8 publications

(24 citation statements)

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“…The deformation of the Hilário Formation along the Lavras do Sul contact suggests that the Hilário Formation is older than the Lavras do Sul Intrusive Complex (Gastal et al, 2015). The Hilário Formation consists of dominantly andesitic rocks represented by andesitic lava flows, lapilli tuff, volcanic agglomerates, and dikes with a shoshonitic geochemical affinity (Lopes et al, 2014;Fontana et al, 2017). The Ar-Ar radiogenic dating of plagioclase suggests an age of 600 to 590 Ma (Janikian et al, 2008) that might be thermally influenced by intrusive magmas such as dikes or the Lavras do Sul granitoids.…”

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confidence: 99%

“…The Neoproterozoic Camaquã Basin and its associated igneous rocks contain significant Au, Cu and Ag ore deposits, such as the Uruguay-São Luiz mines and the Lavras do Sul Mining District (Remus et al, 2000;Bongiolo et al, 2011;Renac et al, 2014). In the central-western section of this basin, volcanogenic (Lopes et al, 2014;Fontana et al, 2017) and plutonic rocks (Mexias et al, 2005) show pervasive alteration described as latemagmatic albitization and hydrothermal alteration with the influx of meteoric fluids (Mexias et al, 1990a(Mexias et al, , 2005Bongiolo et al, 2011;Fontana et al, 2017). The largest Cu deposit in this basin is the Camaquã Mine, which is hosted in a Neoproterozoic sedimentary sequence and was exploited from the 18 th century until 1996 (Remus et al, 2000;Laux et al, 2005;Renac et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

“…The chalcopyrite, pyrite, chalcocite, bornite and covellite sulfides occurred in association with chlorite, hematite, calcite, barite and quartz disseminated in andesitic lapilli tuff and volcanic agglomerates or along fault planes cutting the volcanic sequence. A recent study on the Seival Mine (Fontana et al, 2017) improved current knowledge about the clay minerals in these ore deposits. Fontana et al (2017) described the zoning and lithotypes with the predominant occurrence of smectite, chlorite/smectite mixed-layers, chlorite and corrensite, and suggested that the base-metal deposition was related to the late-magmatic process of albitization and high-temperature hydrothermal alteration.…”

Section: Introductionmentioning

confidence: 99%

“…A recent study on the Seival Mine (Fontana et al, 2017) improved current knowledge about the clay minerals in these ore deposits. Fontana et al (2017) described the zoning and lithotypes with the predominant occurrence of smectite, chlorite/smectite mixed-layers, chlorite and corrensite, and suggested that the base-metal deposition was related to the late-magmatic process of albitization and high-temperature hydrothermal alteration. Later low-temperature hydrothermal alteration represented the mixing of magmatic and meteoric fluids.…”

Section: Introductionmentioning

confidence: 99%

“…The sulfides are represented by chalcopyrite, bornite, chalcocite and covellite (Fontana et al, 2017) and are part of the main Cu-bearing veins that fill fractures and faults. The alteration halos are related to the distances of mineralized structures (Lopes et al, 2014;Fontana et al, 2017).…”

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Mineral assemblages and temperature associated with Cu enrichment in the Seival area (Neoproterozoic Camaquã Basin of Southern Brazil)

Lopes

Renac

Mexias

et al. 2019

Journal of Geochemical Exploration

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The Neoproterozoic sequence of volcanic rocks in the Camaquã Basin included in the Lavras do Sul Shoshonitic Association hosts disseminated Cu deposits. The volcanic sequence in the Seival Mine area includes andesitic lava flows, lapilli tuff, volcanic agglomerate and andesitic dikes with pervasive alteration. The hydrothermal alteration is interpreted to be a product of late-magmatic fluids or the mixing of magmatic with meteoric fluids or basinal brines. The late-magmatic hydrothermal system started after volatile oversaturation and degassing in a magmatic system, which was partially segregated into vesicles. The similar REE contents in the andesine-labradorite and albite indicate that the fluid temperatures ranged from 600 to 250 °C. The crystallization of titanite and Feclinochlore to Mg-chamosite followed the albitization process. The temperature range associated with the chloritization process was estimated using a chlorite geothermometer

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confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Mineral assemblages and temperature associated with Cu enrichment in the Seival area (Neoproterozoic Camaquã Basin of Southern Brazil)

Lopes

Renac

Mexias

et al. 2019

Journal of Geochemical Exploration

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Shoshonitic Magmatic Series and the High Ba-Sr Granitoids: A Review with Emphasis on Examples from the Neoproterozoic Dom Feliciano Belt of Southern Brazil and Uruguay

et al. 2021

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Fractional crystallization of parental magmas of shoshonitic or silica-saturated, ultrapotassic affinity, with variable amount of concurrent crustal assimilation, may result in granitic and syenitic rocks. Typical plutonic members of the shoshonitic series are monzonites and quartz monzonites, whilst syenites and quartz syenites are the dominant plutonic products of the ultrapotassic series. Lamprophyric magmas are commonly found in association with both series and are frequently part of coeval mingling/ mixing systems. Ultrapotassic and shoshonitic primary magmas, including lamprophyric ones, are derived from amphibole-phlogopite-bearing mantle sources produced by previous, subduction-related metasomatism. Acidic and intermediate rocks can be derived from such parental magmas, generally through AFC processes. Shoshonitic-like granitoids, which have not clear relation with intermediate or basic shoshonitic rocks, or are produced dominantly by crustal melting, should be named high-Ba-Sr granitoids. This study focuses mainly on Neoproterozoic shoshonitic and silica-saturated ultrapotassic rock associations formed in post-collisional settings from southern Brazil and Uruguay. The source of magmas, their evolution, the role played by crustal contamination in modifying pristine geochemical signatures and their tectonic control are discussed based on elemental and Sr-Nd isotope geochemistry. The main features of plutonic rocks related to the shoshonitic series are their potassic, silica-saturated alkaline character, predominance of monzonitic to syenitic compositions, high Sr and Ba contents, monotonous, light REE-enriched patterns, and moderate HFSE contents. Syntectonic shoshonitic and high Ba-Sr granitoids within shear zones show lower alkali, LREE, HFSE, and Sr contents than those formed away from the main deformation sites. Plutonic rocks related to the extended silica-saturated ultrapotassic series are mostly syenites, alkalifeldspar granites and lamprophyres with K 2 O/Na 2 O ratios above 2. The typical values of 87 Sr/ 86 Sr i for shoshonitic plutonic rocks are 0.706-0.708, ranging from 0.704 to 0.710. The ε Nd (t) values are negative and vary from 0 to -24. Crustal contribution tends to increase 87 Sr/ 86 Sr i and decrease ε Nd (t) values, depending on protolith isotope signature, melting conditions and volume of assimilated material. Ultrapotassic rocks, on the other hand, show higher 87 Sr/ 86 Sr i ratios, from 0.709-0.711 up to 0.720. Geochemical evidence, including Sr-Nd isotope data, indicates that the shoshonitic and ultrapotassic rocks discussed in this study were formed from OIB-like sources with strong influence of previous subduction, probably a phlogopite, K-amphibole bearing veined mantle. Lithological variability in ultrapotassic-shoshonitic associations is interpreted to result from (i) variation of source composition, (ii) different melt fractions from similar sources, (iii) mixing-mingling, fractional crystallization, and assimilation processes.

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Mass balance and origin of fluids associated to smectite and chlorite/smectite alteration in Seival Mine Cu–Mineralization – Camaquã Basin – Brazil (Part II)

Fontana

Renac

Mexias

et al. 2019

Journal of Geochemical Exploration

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Hydrothermal alteration of volcanic rocks in Seival Mine Cu–mineralization – Camaquã Basin – Brazil (part I): Chloritization process and geochemical dispersion in alteration halos

Cited by 8 publications

References 44 publications

Mineral assemblages and temperature associated with Cu enrichment in the Seival area (Neoproterozoic Camaquã Basin of Southern Brazil)

Mineral assemblages and temperature associated with Cu enrichment in the Seival area (Neoproterozoic Camaquã Basin of Southern Brazil)

Shoshonitic Magmatic Series and the High Ba-Sr Granitoids: A Review with Emphasis on Examples from the Neoproterozoic Dom Feliciano Belt of Southern Brazil and Uruguay

Mass balance and origin of fluids associated to smectite and chlorite/smectite alteration in Seival Mine Cu–Mineralization – Camaquã Basin – Brazil (Part II)

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