Production of carbonic fluids during metamorphism of graphitic pelites in a collisional orogen—An assessment from fluid inclusions

Huff, Timothy A.; Nábělek, Peter I.

doi:10.1016/j.gca.2007.08.001

Cited by 41 publications

(30 citation statements)

References 56 publications

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“…Pattison, 2006;Boiron et al, 2007). Fluid inclusion studies of metapelitic aureoles is compatible with such a scenario, with an initial CH 4 -H 2 O fluid later transforming to a H 2 O-CO 2 fluid as H 2 O reacts with residual graphite (Huff and Nabelek, 2007).…”

Section: Composition and Fate Of Fluidsmentioning

confidence: 77%

How contact metamorphism can trigger global climate changes: Modeling gas generation around igneous sills in sedimentary basins

Aarnes

Svensen

Connolly

et al. 2010

Geochimica et Cosmochimica Acta

221

195

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Large volumes of greenhouse gases such as CH 4 and CO 2 form by contact metamorphism of organic-rich sediments in aureoles around sill intrusions in sedimentary basins. Thermogenic gas generation and dehydration reactions in shale are treated numerically in order to quantify basin-scale devolatilization. We show that aureole thicknesses, defined as the zone of elevated metamorphism relative to the background level, vary within 30-250% of the sill thickness, depending on the temperature of the host-rock and intrusion, besides the sill thickness. In shales with total organic carbon content of >5 wt.%, CH 4 is the dominant volatile (85-135 kg/m 3 ) generated through organic cracking, relative to H 2 O-generation from dehydration reactions (30-110 kg/m 3 ). Even using conservative estimates of melt volumes, extrapolation of our results to the scale of sill complexes in a sedimentary basin indicates that devolatilization can have generated $2700-16200 Gt CH 4 in the Karoo Basin (South Africa), and $600-3500 Gt CH 4 in the Vøring and Møre basins (offshore Norway). The generation of volatiles is occurring on a time-scale of 10-1000 years within an aureole of a single sill, which makes the rate of sill emplacement the time-constraining factor on a basin-scale. This study demonstrates that thousands of gigatons of potent greenhouse gases like methane can be generated during emplacement of Large Igneous Provinces in sedimentary basins.

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Section: Composition and Fate Of Fluidsmentioning

confidence: 77%

How contact metamorphism can trigger global climate changes: Modeling gas generation around igneous sills in sedimentary basins

Aarnes

Svensen

Connolly

et al. 2010

Geochimica et Cosmochimica Acta

221

195

View full text Add to dashboard Cite

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“…The high N 2 content in these fluids indicates an influx of metamorphic fluids. 33 Nitrogen enrichment is also a feature in the greisen altered Skiddaw Granite and this together with the recorded decrease in countryrock N 2 from .800 ppm (2?5 km away from the contact) to ,410 ppm ,0?5 km from the contact 5 is further evidence of countryrock involvement in fluid compositions. The latter may also be suggested by the sub-ppm Re concentrations [0?75 ppm (0?47 ppm 187 Re), Table 1] in molybdenite from the Carrock deposit (DS4-06).…”

Section: The Weardale Granitementioning

confidence: 84%

Geochronology (Re–Os and U–Pb) and fluid inclusion studies of molybdenite mineralisation associated with the Shap, Skiddaw and Weardale granites, UK

Selby¹,

Conliffe²,

Crowley³

et al. 2008

Applied Earth Science

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Late Devonian magmatism in Northern England records key events associated with the Acadian phase of the Caledonian-Appalachian Orogen (C-AO). Zircon U-Pb and molybdenite Re-Os geochronology date emplacement and mineralisation in the Shap (405?2¡1?8 Ma), Skiddaw (398?8¡0?4 and 392?3¡2?8 Ma) and Weardale granites (398?3¡1?6 Ma). For the Shap granite, mineralisation and magmatism are contemporaneous, with mineralisation being directly associated with the boiling of CO 2 -rich magmatic fluids between 300 and 450uC, and 440 and 620 bars. For the Skiddaw granite, the Re-Os age suggests that sulphide mineralisation occurred post-magmatism (398?8¡0?4 Ma) and was associated with the boiling (275 and 400uC and at 375-475 bars) of a non-magmatic fluid, enriched in N 2 , CH 4 and S, which is isotopically heavy. In contrast, the co-magmatic molybdenite mineralisation of the Weardale granite formed from nonfluid boiling at 476 to 577uC at 1-1?7 kbars. The new accurate and precise ages indicate that magmatism and Mo-mineralisation occurred during the same period across eastern Avalonia (cf. Ireland). In addition, the ages provide a timing of tectonism of the Acadian phase of the C-AO in northern England. Based on the post-tectonic metamorphic mineral growth associated with the Shap and Skiddaw granite aureoles, Acadian deformation in the northern England continued episodically (before ,405 Ma) throughout the Emsian (,398 Ma).

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“…Below about 325°C, graphite‐bearing rocks may contain nearly pure and immiscible H 2 O and CH 4 fluids, rather than CO 2 [ Holloway , ]. This may explain CH 4 observed in some low‐grade metamorphic rocks [ Huff and Nabelek , , and references therein]. It is important to note that because graphite may result from metamorphism of sedimentary rocks, the carbon precursor of CH 4 in such an example is ultimately organic (i.e., from marine carbonates, kerogen or dispersed organic matter).…”

Section: Classification Of Abiotic Origins Of Ch4mentioning

confidence: 99%

Abiotic Methane on Earth

Etiope

Lollar

2013

Reviews of Geophysics

501

437

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[1] Over the last 30 years, geochemical research has demonstrated that abiotic methane (CH 4 ), formed by chemical reactions which do not directly involve organic matter, occurs on Earth in several specific geologic environments. It can be produced by either high-temperature magmatic processes in volcanic and geothermal areas, or via low-temperature (<100 C) gas-water-rock reactions in continental settings, even at shallow depths. The isotopic composition of C and H is a first step in distinguishing abiotic from biotic (including either microbial or thermogenic) CH 4 . Herein we demonstrate that integrated geochemical diagnostic techniques, based on molecular composition of associated gases, noble gas isotopes, mixing models, and a detailed knowledge of the geologic and hydrogeologic context are necessary to confirm the occurrence of abiotic CH 4 in natural gases, which are frequently mixtures of multiple sources. Although it has been traditionally assumed that abiotic CH 4 is mainly related to mantle-derived or magmatic processes, a new generation of data is showing that low-temperature synthesis related to gas-water-rock reactions is more common than previously thought. This paper reviews the major sources of abiotic CH 4 and the primary approaches for differentiating abiotic from biotic CH 4, including novel potential tools such as clumped isotope geochemistry. A diagnostic approach for differentiation is proposed.

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Production of carbonic fluids during metamorphism of graphitic pelites in a collisional orogen—An assessment from fluid inclusions

Cited by 41 publications

References 56 publications

How contact metamorphism can trigger global climate changes: Modeling gas generation around igneous sills in sedimentary basins

How contact metamorphism can trigger global climate changes: Modeling gas generation around igneous sills in sedimentary basins

Geochronology (Re–Os and U–Pb) and fluid inclusion studies of molybdenite mineralisation associated with the Shap, Skiddaw and Weardale granites, UK

Abiotic Methane on Earth

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