Dissolution–reprecipitation of igneous zircon in mid-ocean ridge gabbro, Atlantis Bank, Southwest Indian Ridge

Schwartz, Joshua; John, Barbara E.; Cheadle, M. J.; Wooden, Joseph L.; Mazdab, Frank K.; Swapp, Susan M.; Grimes, C. B.

doi:10.1016/j.chemgeo.2010.03.017

Cited by 40 publications

(22 citation statements)

References 68 publications

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“…Another dataset includes zircons from a felsic vein intruding oxide gabbro, the sample of which was dredged during Leg 31 (Schwartz et al 2010). Generally, our analyses fit well with the database of Grimes et al (2009) and usually plot in the middle of a Fig.…”

Section: Zircon: Comparison With Other Datasetssupporting

confidence: 49%

“…The ages of the two stages could be tentatively related to the 206 Pb/ 238 U zircon ages of Schwartz et al (2010). Zircons with high incompatible element contents are old (12.76 ± 0.2 Ma) and are similar in composition to the zircons from Sections 3 and 4 and scarce zircons from the upper sections.…”

Section: Model Of Felsic Melt Formation In Slow-spreading Oceanic Crustmentioning

confidence: 87%

“…These two different scenarios could be perhaps distinguished by careful, precise dating of zircon of known composition as fractional crystallization of the gabbro pile and its remelting could be potentially spaced in time. Schwartz et al (2010) obtained old ages for zircons similar in composition to Group 3 zircon (12.46 Ma, therefore older than the assumed age of oceanic crust formation), which may suggest that they represent an early process of gabbro crystallization. Also, similar compositions of zircons from different depths may indicate that the zircons formed in early fractionated melts that travelled through the cumulate oceanic crust.…”

Section: Oxide Gabbro: Diverse Processes Of Felsic Melt Formation Recmentioning

confidence: 97%

“…This zircon has a different composition compared to Groups 1 and 2, and it also has the lowest δ 18 O of 3.5‰. In this study, the group is represented by a single grain, but grains of similar trace element composition were also sampled from a felsic vein crosscutting oxide gabbro (Schwartz et al 2010) and they also occur in plagiogranite from lower Section 2, 3and 4. Extremely high concentration of Hf, P, Y, REE, Th and U as well as Nb and Ta are consistent with crystallization in highly evolved melts formed by fractional crystallization.…”

Section: Oxide Gabbro: Diverse Processes Of Felsic Melt Formation Recmentioning

confidence: 99%

“…The zircon grains analysed in the sample described by Schwartz et al (2010) usually plot outside the compositional fields defined by the zircon analysed in this study. Their Hf concentration is higher and also most of the trace element concentrations are higher or similar to the maximum values observed in zircon from Sections 3 and 4.…”

Section: Zircon: Comparison With Other Datasetsmentioning

confidence: 99%

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Zircon record of fractionation, hydrous partial melting and thermal gradients at different depths in oceanic crust (ODP Site 735B, South-West Indian Ocean)

Pietranik

Storey

Koepke

et al. 2017

Contrib Mineral Petrol

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Site 735B gabbro. Zircons from oxide gabbro are scarce and variable in composition consistent with their crystallization from melts formed by both fractionation of mafic magmas and hydrous remelting of gabbro cumulate. On the other hand, zircon from plagiogranite is abundant and each sample is characterized by compositional trends consistent with crystallization of zircon in an evolving melt. However, the trends are different between the plagiogranite at 500 m bsf and the deeper sections, which are interpreted as the record of plagiogranite formation by two processes: remelting of gabbro cumulate at 500 m bsf and fractionation at deeper sections. Zircon from both oxide gabbro and plagiogranite has δ 18 O from 3.5 to 6.0‰. Values of δ 18 O are best explained by redistribution of δ 18 O in a thermal gradient and not by remelting of hydrothermally altered crust. Tentatively, it is suggested that fractionation could be an older episode contemporaneous with gabbro crystallization and remelting could be a younger one, triggered by deformation and uplift of the crustal pile.

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Section: Zircon: Comparison With Other Datasetssupporting

confidence: 49%

Section: Model Of Felsic Melt Formation In Slow-spreading Oceanic Crustmentioning

confidence: 87%

Section: Oxide Gabbro: Diverse Processes Of Felsic Melt Formation Recmentioning

confidence: 97%

Section: Oxide Gabbro: Diverse Processes Of Felsic Melt Formation Recmentioning

confidence: 99%

Section: Zircon: Comparison With Other Datasetsmentioning

confidence: 99%

See 3 more Smart Citations

Zircon record of fractionation, hydrous partial melting and thermal gradients at different depths in oceanic crust (ODP Site 735B, South-West Indian Ocean)

Pietranik

Storey

Koepke

et al. 2017

Contrib Mineral Petrol

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U‐Pb dating of interspersed gabbroic magmatism and hydrothermal metamorphism during lower crustal accretion, Vema lithospheric section, Mid‐Atlantic Ridge

et al. 2015

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New U/Pb analyses of zircon and xenotime constrain the timing of magmatism, magmatic assimilation, and hydrothermal metamorphism during formation of the lower crust at the Mid-Atlantic Ridge. The studied sample is an altered gabbro from the Vema lithospheric section (11°N). Primary gabbroic minerals have been almost completely replaced by multiple hydrothermal overprints: cummingtonitic amphibole and albite formed during high-temperature hydration reactions and are overgrown first by kerolite and then prehnite and chlorite. In a previous study, clear inclusion-free zircons from the sample yielded Th-corrected 206 Pb/ 238 U dates of 13.528 ± 0.101 to 13.353 ± 0.057 Ma. Ti concentrations, reported here, zoning patterns and calculated Th/U of the dated grains are consistent with these zircons having grown during igneous crystallization. To determine the timing of hydrothermal metamorphism, we dated a second population of zircons, with ubiquitous <1-20 μm chlorite inclusions, and xenotimes that postdate formation of metamorphic albite. The textures and inclusions of the inclusion-rich zircons suggest that they formed by coupled dissolution-reprecipitation of metastable igneous zircon during or following hydrothermal metamorphism. Th-corrected 206 Pb/ 238 U dates for the inclusion-rich zircons range from 13.598 ± 0.012 to 13.503 ± 0.018 Ma and predate crystallization of all but one of the inclusion-free zircons, suggesting that the inclusion-rich zircons were assimilated from older hydrothermally altered wall rocks. The xenotime dates are sensitive to the Th correction applied, but even using a maximum correction, 206 Pb/ 238 U dates range from 13.341 ± 0.162 to 12.993 ± 0.055 Ma and postdate crystallization of both the inclusion-rich zircons and inclusion-free igneous zircons, reflecting a second hydrothermal event. The data provide evidence for alternating magmatism and hydrothermal metamorphism at or near the ridge axis during accretion of the lower crust at a ridge-transform intersection and suggest that hydrothermally altered crust was assimilated into younger gabbroic magmas. The results of this study show that high-precision U-Pb dating is a powerful method for studying the timing of magmatic and hydrothermal processes at mid-ocean ridges.

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Zircon U–Pb geochronology of lower crust and quartzo-feldspathic clastic sediments from the Balagne ophiolite (Corsica)

et al. 2017

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Dissolution–reprecipitation of igneous zircon in mid-ocean ridge gabbro, Atlantis Bank, Southwest Indian Ridge

Cited by 40 publications

References 68 publications

Zircon record of fractionation, hydrous partial melting and thermal gradients at different depths in oceanic crust (ODP Site 735B, South-West Indian Ocean)

Zircon record of fractionation, hydrous partial melting and thermal gradients at different depths in oceanic crust (ODP Site 735B, South-West Indian Ocean)

U‐Pb dating of interspersed gabbroic magmatism and hydrothermal metamorphism during lower crustal accretion, Vema lithospheric section, Mid‐Atlantic Ridge

Zircon U–Pb geochronology of lower crust and quartzo-feldspathic clastic sediments from the Balagne ophiolite (Corsica)

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