Carbon and Oxygen Isotope Studies in Rocks of the Vicinity of the Almadén Mercury Deposit (Province of Ciudad Real, Spain)

Eichmann, R.; Saupé, Francis; Schidlowski, Manfred

doi:10.1007/978-3-642-66806-7_26

Cited by 5 publications

(7 citation statements)

References 17 publications

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“…Most of the mafic volcanic rocks display high concentrations of CO 2 ranging from 8 to 15%, while in and around the mercury deposits, these figures can be as high as 20 and 30% in basalts and ultramafic xenoliths respectively (Higueras, 1995). The isotopic composition of these carbonates at about −6‰ (Eichmann et al, 1977;Rytuba et al, 1989) suggests a primary and probably a mantle origin for this component. The recent work of Helo et al (2011) for Mid Ocean Ridge basalts provides some useful insights into this matter.…”

Section: Whole-rock Geochemistry and Magmatic Sourcementioning

confidence: 95%

“…Oxygen isotope compositions reported by Eichmann et al (1977) range from + 12.8‰ to + 19.9‰ (versus SMOW) for carbonates in mafic lavas and from + 14.0‰ to + 18.9‰ for carbonates in mineralized veins and the Frailesca rocks. The study of the δ 18 O values for hydrothermal fluids in the Almadén case is difficult because the variable carbonate mineralogy (Eichmann et al, 1977), and by the well known susceptibility of carbonates to oxygen isotopic re-equilibration at low temperatures (O'Neil,, 1987). Carbonates in active geothermal systems may achieve isotopic equilibrium with fluids down to temperatures as low as 150°C.…”

Section: Hydrothermal Processesmentioning

confidence: 99%

“…et al (1977), and Saupé and Arnold (1992) reported the results of extensive research on the carbon, oxygen and sulfur isotope geochemistry of the country rocks and ores from the Almadén Hg deposits. Eichmann et al (1977) proposed a primary mantle source for the carbonate constituents in the metavolcanics, whereas Saupé and Arnold (1992) suggested that the Ordovician shales were the main source of carbon and sulfur.…”

Section: Whole-rock Geochemistry and Magmatic Sourcementioning

confidence: 99%

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Intraplate mafic magmatism, degasification, and deposition of mercury: The giant Almadén mercury deposit (Spain) revisited

Higueras

Oyarzún

Lillo

et al. 2013

Ore Geology Reviews

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The giant Almadén mercury deposit (Spain) is hosted by the Lower Silurian Criadero Quartzite; in turn this ore-bearing rock unit is cross-cut by the so-called Frailesca unit, a diatreme body of basaltic composition. The geochemical characteristics of the Silurian to Devonian Almadén District volcanic units indicate that these rocks originated from an enriched, evolving mantle source that ultimately yielded basanites-nephelinites to rhyolites, through olivine-basalts, pyroxene-basalts, trachybasalts, trachytes, very scarce rhyolites, and quartzdiabases. The Silurian intraplate alkaline volcanism developed in submarine conditions which triggered widespread hydrothermal activity resulting in Hg ore formation and pervasive alteration to carbonates. The δ 18 O, δ 13 C, and δ 34 S isotopic signatures for carbonates and pyrite suggest different sources for carbon and sulfur, including magmatic and organic for the former and magmatic and sea water for the latter. The most important and efficient natural source of mercury on Earth is by far the volcanic activity, which liberates mercury via quiescent degassing and catastrophic (Plinian) events when eruptions can overwhelm the atmospheric budget of Hg. Thus, we suggest that CO 2 degasification and coeval distillation of mercury from the volcanic rocks fed the huge hydrothermal system that led to massive deposition of mercury at Almadén. Build up of Hg 0 gas in magmatic chambers during waning rifting in the Late Ordovician, followed by renewed volcanism in the Early Silurian, would have resulted in massive degasification of the accumulated mercury. Part of this mercury went into the Criadero Quartzite leading to formation of the huge Almadén deposit and others (e.g., El Entredicho) along the same stratigraphic level. Progressive depletion of the deep seated magmatic Hg stock would have resulted in a drastic reduction in ore deposit size after the Lower Silurian when smaller deposits formed (e.g., Las Cuevas).

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Section: Whole-rock Geochemistry and Magmatic Sourcementioning

confidence: 95%

Section: Hydrothermal Processesmentioning

confidence: 99%

Section: Whole-rock Geochemistry and Magmatic Sourcementioning

confidence: 99%

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Intraplate mafic magmatism, degasification, and deposition of mercury: The giant Almadén mercury deposit (Spain) revisited

Higueras

Oyarzún

Lillo

et al. 2013

Ore Geology Reviews

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“…d 13 C isotopic data from carbonates associated with the Hg mineralization in the Almadén district (Eichmann et al, 1977;Rytuba et al, 1988) suggested a mantle origin for the carbon. This possible cause of the high aCO 2 would agree with an early hydrothermal alteration of the primary igneous Cr-rich spinels.…”

Section: G E N E S I S O F T H E C R -R I C H P H Y L L O S I L I C Amentioning

confidence: 99%

Fuchsite and other Cr-rich phyllosilicates in ultramafic enclaves from the Almadén mercury mining district, Spain

Morata¹,

Higueras²,

Domínguez‐Bella³

et al. 2001

Clay miner.

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Fuchsite and other Cr-rich phyllosilicates, paragenetic with dolomite, are present in some ultramafic enclaves from the ‘frailesca’ rock (a lapilli- to block-size pyroclastic lithic-tuff), in the Almadén mercury mining district, Spain. Analyses (EMPA and TEM) of fuchsite and Cr-chlorite showed a relatively large range in levels of Cr2O3. Petrographic relationships between these phyllosilicates and primary relics of Cr-spinel crystals, as well as their high Cr content, indicate that these Cr-rich minerals originated from primary chromian spinels through an early hydrothermal alteration stage. The hydrothermal fluids accounting for this early alteration would be of relatively high temperature, high aCO2 and aK, and variable aNa/K. In a later alteration stage, fuchsite was partially or totally replaced by illite and Cr-illite, giving rise to an argillitic alteration.

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“…Moreover, SaupeÂ (1990) discusses the possibility of kinetic isotopic disequilibrium in the district. Eichmann et al (1977) and Arnold and SaupeÂ (1985) analyzed d 13 C and d 18 O in carbonate and d 13 O in quartz. d 13 C measurements on calcites suggest that hydrothermal CO 2 was derived largely from a deep-seated source.…”

Section: Metallogenymentioning

confidence: 99%

The Almadén mercury mining district, Spain

Hernández¹,

Jébrak

Higueras³

et al. 1999

Mineralium Deposita

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The AlmadeÂ n district is the largest mercury concentration in the world, with a total content of about 250 000 t of mercury, nearly one third of the known total mercury resources of the Earth. Mercury has been exploited since the Celtic and Roman times, with peak production during the Renaissance and between 1939± 1945. The district is hosted by a Paleozoic synclinorium overlying Precambrian rocks. The Paleozoic sequence comprises epicontinental quartz arenite rocks, including black shales and quartzites. Diatremes, alkaline lavas of dierent composition, and late tholeiitic diabases account for the Ordovician to Devonian magmatism. The tectonic setting of this complex suite corresponds to the intraplate type. The mercury deposits of AlmadeÂ n can be classi®ed into two main types: type 1, early stratiform type ores characterized by cinnabar deposition on the lower Silurian quartzites (Criadero quartzite; e.g. the AlmadeÂ n and El Entredicho deposits), and type 2, late discordant orebodies (e.g. Las Cuevas), largely hosted or related to diatremes (the`frailesca rocks') of alkaline basaltic composition. In type 1 cinnabar was deposited during diagenesis, in relation to hydrothermal circulation driven by magmatic activity. Type 2 include a variety of deposits having in common the discordant character of the orebodies (e.g. veins, stockworks, massive replacements), and their wide dispersion along the stratigraphic column, i.e. from Lower Silurian (e.g. Nueva ConcepcioÂ n) to Upper Devonian (e.g. Corchuelo).

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Carbon and Oxygen Isotope Studies in Rocks of the Vicinity of the Almadén Mercury Deposit (Province of Ciudad Real, Spain)

Cited by 5 publications

References 17 publications

Intraplate mafic magmatism, degasification, and deposition of mercury: The giant Almadén mercury deposit (Spain) revisited

Intraplate mafic magmatism, degasification, and deposition of mercury: The giant Almadén mercury deposit (Spain) revisited

Fuchsite and other Cr-rich phyllosilicates in ultramafic enclaves from the Almadén mercury mining district, Spain

The Almadén mercury mining district, Spain

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