Isotopic and element exchange during serpentinization and metasomatism at the Atlantis Massif (MAR 30°N): Insights from B and Sr isotope data

Boschi, Chiara; Dini, Andréa; Früh-Green, Gretchen L.; Kelley, Deborah S.

doi:10.1016/j.gca.2008.01.013

Cited by 180 publications

(145 citation statements)

References 124 publications

(224 reference statements)

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“…These are consistently lower than the B content of seawater and endmember hydrothermal fluids have been determined to 0.34-0.55 lg/g (31-51 lmol/kg), 2.57 lg/g (238 lmol/kg), and 3.62 lg/g (335 lmol/kg) for Lost City, Rainbow, and Logatchev, respectively (Schmidt et al 2007;Foustoukos et al 2008;Boschi et al 2008;Seyfried et al 2011Seyfried et al , 2015. Boron isotopic data for ultramafic-hosted vent fluids are not yet available, but have been estimated to þ 25 to +30‰ (Foustoukos et al 2008;Boschi et al 2008).…”

Section: Hydrothermal Vent Fluidsmentioning

confidence: 85%

“…8.4). This is accompanied by a small isotopic shift to lower d 11 B values between þ 8:8 and +13.5‰ for all but one sample (Boschi et al 2008;Harvey et al 2014). …”

Section: Serpentinizationmentioning

confidence: 89%

“…Most samples display d 11 B values between þ 7:0 and +19.9‰ ( Fig. 8.4; Table 8.1; Lécuyer et al 2002;Boschi et al 2008;Harvey et al 2014). Exceptionally high d 11 B values were found in serpentinites from ODP Leg 209 (Mid-Atlantic Ridge) of approximately þ 30 to +41‰ ( Fig.…”

Section: Serpentinizationmentioning

confidence: 97%

“…Metasomatic rocks produced by the interaction of serpentinites with silica-rich fluids derived from gabbroic intrusions have been investigated along with coexisting serpentinites (Boschi et al 2008;Harvey et al 2014). These rocks are rich in talc, as well as tremolite or chlorite, the formation of which postdates serpentinization (Boschi et al 2008;Harvey et al 2014).…”

Section: Serpentinizationmentioning

confidence: 99%

“…These rocks are rich in talc, as well as tremolite or chlorite, the formation of which postdates serpentinization (Boschi et al 2008;Harvey et al 2014). This steatitization process led to boron loss from the samples compared to the serpentinite precursor with concentrations ranging from 2.0 to 28.7 lg/g (Fig.…”

Section: Serpentinizationmentioning

confidence: 99%

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Boron Isotopes in the Ocean Floor Realm and the Mantle

Marschall

2017

Advances in Isotope Geochemistry

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This chapter reviews the boron isotopic composition of the ocean floor, including pristine igneous oceanic crust such as mid-ocean ridge basalts and ocean island basalts and their implications for the B isotopic composition of the mantle. The chapter further discusses the B isotopic effects of assimilation of altered crustal materials in mantle-derived magmas. The systematics of seawater alteration on oceanic rocks are discussed, including sediments, igneous crust and serpentinization of ultramafic rocks and the respective marine hydrothermal vent fluids. The chapter concludes with a discussion of the secular evolution of the B isotopic composition of seawater.

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Section: Hydrothermal Vent Fluidsmentioning

confidence: 85%

“…8.4). This is accompanied by a small isotopic shift to lower d 11 B values between þ 8:8 and +13.5‰ for all but one sample (Boschi et al 2008;Harvey et al 2014). …”

Section: Serpentinizationmentioning

confidence: 89%

Section: Serpentinizationmentioning

confidence: 97%

Section: Serpentinizationmentioning

confidence: 99%

Section: Serpentinizationmentioning

confidence: 99%

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Boron Isotopes in the Ocean Floor Realm and the Mantle

Marschall

2017

Advances in Isotope Geochemistry

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Serpentinization of mantle‐derived peridotites at mid‐ocean ridges: Mesh texture development in the context of tectonic exhumation

Rouméjon

Cannat

2014

Geochem Geophys Geosyst

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At slow spreading ridges, axial detachment faults exhume mantle-derived peridotites and hydrothermal alteration causes serpentinization in a domain extending more than 1 km next to the fault. At the microscopic scale, serpentinization progresses from a microfracture network toward the center of olivine relicts and forms a mesh texture. We present a petrographic study (SEM, EBSD, and Raman) of the serpentine mesh texture in a set of 278 abyssal serpentinized peridotites from the Mid-Atlantic and Southwest Indian Ridges. We show that serpentinization initiated along two intersecting sets of microfractures that have consistent orientations at the sample scale, and in at least one studied location, at the 100 m scale. We propose that these microfractures formed in fresh peridotites due to combined thermal and tectonic stresses and subsequently served as channels for serpentinizing fluids. Additional reaction-induced cracks developed for serpentinization extents <20%. The resulting microfracture network has a typical spacing of $60 mm but most serpentinization occurs next to a subset of these microfractures that define mesh cells 100-400 mm in size. Apparent mesh rim thickness is on average 33 6 19 mm corresponding to serpentinization extents of 70-80%. Published laboratory experiments suggest that mesh rims formation could be completed in a few years (i.e., quasi instantaneous at the plate tectonic timescale). The depth and extent of the serpentinization domain in the detachment fault's footwall are probably variable in time and space and as a result we expect that the serpentine mesh texture at slow spreading ridges forms at variable rates with a spatially heterogeneous distribution.

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Fluid circulation and carbonate vein precipitation in the footwall of an oceanic core complex, Ocean Drilling Program Site 175, Mid‐Atlantic Ridge

Schroeder

Bach

Jöns

et al. 2015

Geochem Geophys Geosyst

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Carbonate veins recovered from the mafic/ultramafic footwall of an oceanic detachment fault on the Mid‐Atlantic Ridge record multiple episodes of fluid movement through the detachment and secondary faults. High‐temperature (∼75–175°C) calcite veins with elevated REE contents and strong positive Eu‐anomalies record the mixing of up‐welling hydrothermal fluids with infiltrating seawater. Carbonate precipitation is most prominent in olivine‐rich troctolite, which also display a much higher degree of greenschist and sub‐greenschist alteration relative to gabbro and diabase. Low‐temperature calcite and aragonite veins likely precipitated from oxidizing seawater that infiltrated the detachment fault and/or within secondary faults late or post footwall denudation. Oxygen and carbon isotopes lie on a mixing line between seawater and Logatchev‐like hydrothermal fluids, but precipitation temperatures are cooler than would be expected for isenthalpic mixing, suggesting conductive cooling during upward flow. There is no depth dependence of vein precipitation temperature, indicating effective cooling of the footwall via seawater infiltration through fault zones. One sample contains textural evidence of low‐temperature, seawater‐signature veins being cut by high‐temperature, hydrothermal‐signature veins. This indicates temporal variability in the fluid mixing, possibly caused by deformation‐induced porosity changes or dike intrusion. The strong correlation between carbonate precipitation and olivine‐rich troctolites suggests that the presence of unaltered olivine is a key requirement for carbonate precipitation from seawater and hydrothermal fluids. Our results also suggest that calcite‐talc alteration of troctolites may be a more efficient CO2 trap than serpentinized peridotite.

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Isotopic and element exchange during serpentinization and metasomatism at the Atlantis Massif (MAR 30°N): Insights from B and Sr isotope data

Cited by 180 publications

References 124 publications

Boron Isotopes in the Ocean Floor Realm and the Mantle

Boron Isotopes in the Ocean Floor Realm and the Mantle

Serpentinization of mantle‐derived peridotites at mid‐ocean ridges: Mesh texture development in the context of tectonic exhumation

Fluid circulation and carbonate vein precipitation in the footwall of an oceanic core complex, Ocean Drilling Program Site 175, Mid‐Atlantic Ridge

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