Paired stable isotopes (O, C) and clumped isotope thermometry of magnesite and silica veins in the New Caledonia Peridotite Nappe

Quesnel, Benoît; Boulvais, Philippe; Gautier, Pierre; Cathelineau, ‪Michel; John, Cédric M.; Dierick, Malorie; Agrinier, Pierre; Drouillet, Maxime

doi:10.1016/j.gca.2016.03.021

Cited by 37 publications

(37 citation statements)

References 66 publications

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“…While we cannot be definitive regarding fractionation and re-equilibration, our data agree well with recent studies where a near-surface, low-temperature, meteoricwater origin for ultramafic-hosted magnesites has been proposed (Oskierski et al 2012;Quesnel et al 2013Quesnel et al , 2016 and also in the classic work of O'Neil & Barnes (1971). Data fields from these studies are shown in Figure 9 for comparison with our values.…”

Section: Stable Isotopessupporting

confidence: 91%

“…The hydrothermal signature may be pre-and/or co-genetic with weathering, and while we cannot constrain temperatures attained in the past, the isotope data show that most of the Mg-(hydro)carbonates in this study formed (or re-equilibrated) at temperatures at or below 30 ˚C. This interpretation, supported by similar recent field case studies (Oskierski et al 2012;Quesnel et al 2013Quesnel et al , 2016) conflicts with earlier laboratory work (Hänchen et al 2008;Möller 1989;Sayles & Fyfe 1973;Stevula et al 1978) where magnesite does not precipitate until fluid temperatures are in the range 60-120 ˚C.…”

Section: Paragenesissupporting

confidence: 79%

“…In parallel to the carbon-storage context and often stimulated by economic interest in magnesite for industrial end-uses, there has been growing consensus that most ultramafic-hosted magnesites form under near surface conditions with involvement of meteoric water (see recent overviews in Keleman et al 2011;Oskierski et al 2013;Quesnel et al 2013Quesnel et al , 2016. While 'low' (typically <60 ˚C) temperatures of magnesite mineralization are often inferred (Keleman et al 2011) -usually from oxygen isotope data -precise temperatures of carbonation are difficult to ascribe, partly because the parent fluid is often not well-constrained, and because the magnesite-water oxygen isotope fractionation factor is still not fully resolved (Chako & Deines 2008).…”

mentioning

confidence: 99%

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Stable isotope evidence for near-surface, low-temperature formation of Mg-(hydro)carbonates in highly altered Greek Mesozoic serpentinites

Andrews

Stamatakis

Mitsis

et al. 2017

JGS

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Authigenic magnesite, hydromagnesite and huntite associated with intensely altered and serpentinized ophiolitic rocks in Attica (mainland Greece) occur predominantly as veinlets and nodules within a totally weathered former-serpentinite groundmass. Carbonate δ 18 O values are consistent with post-geothermal fluid temperatures between 25-70 ˚C, but mostly between 25-30 ˚C, from a dominantly meteoricsourced groundwater, indicating near-surface, low-temperature conditions. Despite the proximity of a volcanic centre with strong CO2 flux, 75% of the carbon isotope data imply little or no incorporation of this CO2 into the authigenic Mg-(hydro)carbonates. Indeed, many δ 13 C values are more negative than soil-zone calcrete values, and in this setting Mg-(hydro)carbonate δ 13 C below-6‰ VPDB probably indicate disequilibrium effects in alkaline groundwaters. Geothermal fluids and groundwaters were mainly routed through structural conduits. Some of the low temperature hydromagnesite subsequently dehydrated to magnesite under nearsurface conditions, while huntite is likely a diagenetic transformation of hydromagnesite, forming close to the volcanic centre where fluid Mg/Ca ratios were low. The isotopic signatures are distinct from previously published Balkan-East Mediterranean magnesite data arrays but are consistent with many other ultramaficassociated magnesium carbonates worldwide; their association with likely fluid compositions provide important context for Mg-(hydro)carbonate formation as geothermal conditions cool to near surface temperatures.

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Section: Stable Isotopessupporting

confidence: 91%

Section: Paragenesissupporting

confidence: 79%

mentioning

confidence: 99%

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Stable isotope evidence for near-surface, low-temperature formation of Mg-(hydro)carbonates in highly altered Greek Mesozoic serpentinites

Andrews

Stamatakis

Mitsis

et al. 2017

JGS

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“…Karbonátkiválások vizsgálatával meghatározható a törések és a vetők mentén mozgó fluidumok hőmérséklete, illetve a fluidum eredeti oxigénizotópos-összetétele (SWANSON et al 2012, BERGMAN et al 2013, LOYD et al 2013, CRUSET et al 2016, QUESNEL et al 2016. A töréskitöltő karbonátok ∆ 47 értékei geotermális rezervoárok hőmérsék -letének meghatározására is használhatóak (SUMNER et al 2015).…”

Section: Szerkezetföldtani Alkalmazásokunclassified

Kapcsolt izotópok (clumped isotopes) a földtudományi kutatásokban

Kele

Bajnai

2017

Földt. Közl.

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BevezetésA geokémiai vizsgálatok mára a geológia minden terü -letén -az őslénytantól a rétegtanon át, a paleoklíma kutatásig -megkerülhetetlenné váltak. Az izotóp-geokémia tör té nete a XX. század első felére nyúlik vissza. Az első tömegspektrométer megalkotása 1947-ben Alfred NIER nevé hez fűződik. Ebben az időben publikálta UREY (1947), valamint BIGELEISEN & MAYER (1947 O egy többszörösen helyettesített CO 2 izotopológ). Mivel az ilyen izotopológok rendkívül alacsony előfordulási aránya a mérésüket korábban lehetetlenné tette, a többszörösen helyettesített izotopológok egészen az 1980-as évek végéig érintetlen kutatási területnek számítottak. Az első, kifejezetten erre a témára irányuló kutatás az atmoszféra metán -jának izotópos összetételét vizsgálta (MROZ et al. 1989 O isotopes within one molecule. Using the clumped isotope thermometer, the temperature of the carbonate precipitating fluids can be determined with high precision, based solely on the clumped isotope value (∆ 47 ) of carbonates. Besides palaeoclimatology, the method can be used in several research fields in geology, including palaeoceanography, atmospheric research, reservoir geology, geomorphology, structural geology, diagenesis, biogeochemistry, low temperature metamorphic processes, and meteorite research. Due to continuous developments, the number of applications is still significantly increasing. This paper briefly introduces the reader to the principles of clumped isotope geochemistry, reviewing its theoretical basis, and possible applications, and also looks at available calibrations. Furthermore, it provides an overview of the current state-of-the-art.Keywords: stable isotopes, clumped isotopes, geochemistry, thermometry, climate reconstruction, methodology Összefoglalás A kapcsoltizotóp-geokémia (clumped isotope geochemistry), egy olyan új, dinamikusan fejlődő kutatási módszer, amely a 13 C és a 18 O izotópok egy molekulán belüli kapcsolódásának hőmérsékletfüggésén alapszik. Segítségével a karbonátok kiválási hőmérséklete nagy pontossággal meghatározható, kizárólag a karbonát fázis kapcsoltizotóp-értéke (∆ 47 ) alapján. A paleoklimatológiai alkalmazások mellett a módszer a geológiai kutatások számos területén (pl. paleooceanográfia, atmoszféra-kutatás, rezervoár-geológia, geomorfológia, tektonika, diagenezis, biogeokémia, alacsony hőmérsékletű metamorf folyamatok, meteorit-kutatás, stb.) alkalmazható, és a műszerfejlesztések révén az alkal mazá -sok köre folyamatosan bővül. A cikk röviden áttekinti a kapcsolt izotópos módszert, bemutatva annak alapjait, a rendelkezésre álló kalibrációkat, a lehetséges alkalmazási területeket és a témában eddig megjelent publikációkat.

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“…Due to its position right above the presumed major thrust system, the frontal part of the Peridotite Nappe may have undergone renewed tangential shear on this occasion. In line with this hypothesis, top‐to‐SW shearing along the serpentine sole of the Koniambo Massif involves synkinematic magnesite veins [ Quesnel et al ., , ] formed at temperatures of only ~30°C [ Quesnel et al ., ], which suggests that the thickness of the Peridotite Nappe had already been much reduced when this deformation occurred.…”

Section: Obduction Tectonics In New Caledoniamentioning

confidence: 99%

The emplacement of the Peridotite Nappe of New Caledonia and its bearing on the tectonics of obduction

2016

Self Cite

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The Peridotite Nappe of New Caledonia is one of the few ophiolites worldwide that escaped collisional orogeny after obduction. Here we describe the deformation associated with serpentinization in two klippes of the nappe in northwestern New Caledonia. The klippes are flat lying and involve S/SW vergent reverse‐slip shear zones which are true compressional structures in origin. Further northeast, the nappe is folded in association with the development of a steep schistosity in low‐grade metasediments. This difference in structural style indicates that the Peridotite Nappe experienced compression at greater depths toward its root zone, suggesting a “push from the rear” mechanism of emplacement. This supports the view that the nappe has been emplaced through horizontal contraction sustained by plate convergence. We establish a crustal‐scale cross section at the end of the obduction event, before Neogene extension. This involves a large fold nappe of high‐pressure rocks bounded from below by a major thrust. Furthermore, we show that obduction in New Caledonia occurred through dextral oblique convergence. Oblique convergence probably resulted from the initial obliquity between the subduction trench and the continental ribbon that became incorporated in it. This obliquity can solve the paradox of the Peridotite Nappe seemingly being emplaced at the same time the high‐pressure rocks were exhumed. Oblique convergence together with focused erosional denudation on the northeastern flank of the island led to exhumation of the metamorphic rocks in a steep fold nappe rising through the rear part of the orogen.

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Paired stable isotopes (O, C) and clumped isotope thermometry of magnesite and silica veins in the New Caledonia Peridotite Nappe

Cited by 37 publications

References 66 publications

Stable isotope evidence for near-surface, low-temperature formation of Mg-(hydro)carbonates in highly altered Greek Mesozoic serpentinites

Stable isotope evidence for near-surface, low-temperature formation of Mg-(hydro)carbonates in highly altered Greek Mesozoic serpentinites

Kapcsolt izotópok (clumped isotopes) a földtudományi kutatásokban

The emplacement of the Peridotite Nappe of New Caledonia and its bearing on the tectonics of obduction

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