Ion-exchange experiments and RbSr dating on celadonites from the Troodos ophiolite, Cyprus

Booij, Ernst; Gallahan, William E.; Staudigel, Hubert

doi:10.1016/0009-2541(95)00116-1

Cited by 29 publications

(13 citation statements)

References 40 publications

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“…2.9a). This is consistent with geophysical (Stein and Stein 1994;Fisher and Becker 2000;Jarrard 2003) and geochemical (Hart and Staudigel 1986;Peterson et al 1986;Booij et al 1995) lines of evidence suggesting that vigorous seawater circulation and oxidative alteration take place especially in young crust. Although the timing for the termination of the circulation and alteration is still uncertain, a simple model of age-dependent oxidative alteration was employed in this study, based on the change in geophysical parameters sensitive to crustal hydration (Jarrard 2003).…”

Section: Ironsupporting

confidence: 73%

Geochemical Constraints on Potential Biomass Sustained by Subseafloor Water–Rock Interactions

Nakamura

Takai

2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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Since the first discovery of macrofaunal and microbial communities endemic to hydrothermal vents, chemolithoautotrophic microorganisms at and beneath the seafloor have attracted the interest of many researchers. This type of microorganism is known to obtain energy from inorganic substances (e.g., reduced sulfur compounds, molecular hydrogen, and methane) derived from subsurface physical and chemical processes, such as water-rock interactions. As the primary producers, they sustain chemosynthetic ecosystems, which are fundamentally different from terrestrial and shallow marine ecosystems that are sustained by photosynthetic primary production. It is possible that the chemosynthetic ecosystems at and beneath the seafloor are vast and metabolically active, playing an important role in the global geochemical cycles of many bio-essential elements. However, even today, the spatial and temporal distributions of the unseen chemosynthetic biosphere are largely uncertain. Here, we present geochemical constraints on the estimate of the potential biomass in seafloor and subseafloor chemosynthetic ecosystems sustained by high-temperature deep-sea hydrothermal activities and low-temperature alteration/weathering of oceanic crust. The calculations are based on the fluxes of metabolic energy sources (S, H 2 , Fe, and CH 4 ), the chemical energy yields for metabolic reactions, and the maintenance energy requirements. The results show that for deep-sea hydrothermal vent ecosystems, most bioavailable energy yields (86 %) are due to oxidation reactions of S. In contrast, for subseafloor oceanic crust ecosystems, oxidation reactions of Fe and S generally yield the same amounts of bioavailable energy (59 % and 41 %, respectively). The estimated biomass potential in the subseafloor oceanic crust ecosystems (0.14 Pg C) is one order of magnitude higher than that in global deep-sea hydrothermal vent ecosystems (0.0074 Pg C), most likely reflecting the greater flux of

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Section: Ironsupporting

confidence: 73%

Geochemical Constraints on Potential Biomass Sustained by Subseafloor Water–Rock Interactions

Nakamura

Takai

2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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“…11), implying that celadonite might be the stabilizing mineral phase. Celadonites also contain significant Rb (Booij et al, 1995;Innocent et al, 1997), an element that was consistently found in association with oxidation-resistant Tc(IV) (Fig. 8).…”

Section: Initialmentioning

confidence: 95%

Oxidative dissolution potential of biogenic and abiogenic TcO2 in subsurface sediments

Fredrickson

Zachara

Plymale

et al. 2009

Geochimica et Cosmochimica Acta

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Technetium-99 (Tc) is an important fission product contaminant associated with sites of nuclear fuels reprocessing and geologic nuclear waste disposal. Tc is highly mobile in its most oxidized state ½TcðVIIÞO 4 À and less mobile in the reduced form [Tc(IV)O 2 ÁnH 2 O]. Here we investigate the potential for oxidation of Tc(IV) that was heterogeneously reduced by reaction with biogenic Fe(II) in two sediments differing in mineralogy and aggregation state; unconsolidated Pliocene-age fluvial sediment from the upper Ringold (RG) Formation at the Hanford Site and a clay-rich saprolite from the Field Research Center (FRC) background site on the Oak Ridge Site. Both sediments contained Fe(III) and Mn(III/IV) as redox active phases, but FRC also contained mass-dominant Fe-phyllosilicates of different types. Shewanella putrefaciens CN32 reduced Mn(III/ IV) oxides and generated Fe(II) that was reactive with Tc(VII) in heat-killed, bioreduced sediment. After bioreduction and heat-killing, biogenic Fe(II) in the FRC exceeded that in RG by a factor of two. More rapid reduction rates were observed in the RG that had lower biogenic Fe(II), and less particle aggregation. EXAFS measurements indicated that the primary reduction product was a TcO 2 -like phase in both sediments. The biogenic redox product Tc(IV) oxidized rapidly and completely in RG when contacted with air. Oxidation, in contrast, was slow and incomplete in the FRC, in spite of similar molecular scale speciation of Tc compared to RG. X-ray microprobe, electron microprobe, X-ray absorption spectroscopy, and micro X-ray diffraction were applied to the whole sediment and isolated Tc-containing particles. These analyses revealed that non-oxidizable Tc(IV) in the FRC existed as complexes with octahedral Fe(III) within intra-grain domains of 50-100 lmsized, Fe-containing micas presumptively identified as celadonite. The markedly slower oxidation rates in FRC as compared to RG were attributed to mass-transfer-limited migration of O 2 into intra-aggregate and intraparticle domains where Tc(IV) existed; and the formation of unique, oxidation-resistant, intragrain Tc(IV)-Fe(III) molecular species.

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“…added to the Troodos upper oceanic crust requires an estimate of the Li-isotopic composition of the ocean ~70 to 90 Myr ago when alteration occurred (Staudigel et al, 1986;Booij et al, 1995). The only estimate we are aware of comes from Pogge von Strandmann et al 2013; their data suggest that ~93 Myr seawater had a  7 Li of ~22±2‰ based on bulk carbonate analyses.…”

Section: Estimating the Bulk Isotopic Fractionation Between Cretaceoumentioning

confidence: 99%

The role of low-temperature (off-axis) alteration of the oceanic crust in the global Li-cycle: Insights from the Troodos ophiolite

Coogan

Gillis

Pope

et al. 2017

Geochimica et Cosmochimica Acta

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Changes in the global Li-cycle, as recorded in the Li concentration and/or isotopic composition of seawater, have the potential to provide important insight into the controls on the long-term C-cycle. Understanding the magnitude and isotopic composition of the fluxes of Li into and out-of the ocean, and the controls on any variability in these, is necessary if we are to correctly interpret the paleo-record of the Li-cycle. Here the lowtemperature hydrothermal sink is investigated using the volcanic section of the exceptionally preserved Troodos ophiolite. Using glass to define the protolith Li content, the uptake flux of Li is determined using bulk-rock analyses from four hydrologically distinct sections through the lava pile of the ophiolite. Differences in paleo-hydrological conditions in the crust appear to have played a significant role in controlling the uptake *Manuscript 2 flux of Li with an 'average' uptake flux of equivalent to 14-21x10 9 mol yr-1this is considerably larger than generally assumed. Bulk-rock samples that contain a large seawater Li component have  7 Li of ~10±2‰. Celadonite separates have a  7 Li of ~6±1‰, considerably lighter than bulk-rock samples with the same Li content. Because celadonite is a significant repository for Li within the Troodos upper crust this means that another phase(s) must have markedly heavier  7 Li than the average bulk-rock; i.e. changes in the average mineralogy of altered crust will lead to changes in the bulk isotopic fractionation between the Li added to the upper oceanic crust and seawater ( SWlava). The shallowest samples in three of the four studied sections are isotopically lighter than deeper samples (but do not contain significant celadonite), again indicating that variations in alteration conditions and/or mineralogy can lead to variations in  SW-lava. Comparison with other studies of altered upper oceanic crust suggests that changes in alteration conditions (probably largely temperature) lead to significant changes in  SW-lava. These changes likely reflect both a temperature dependence of the isotopic fractionation factor and a change in the fractionation factor due to changing mineral assemblage and/or mineral compositions and abundances. A significant portion of the increase in  7 Li of seawater over the past 50 Myr may be due to an increase in the bulk fractionation factor between seawater and Li added to the upper oceanic crust due to cooling bottom water.

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Ion-exchange experiments and RbSr dating on celadonites from the Troodos ophiolite, Cyprus

Cited by 29 publications

References 40 publications

Geochemical Constraints on Potential Biomass Sustained by Subseafloor Water–Rock Interactions

Geochemical Constraints on Potential Biomass Sustained by Subseafloor Water–Rock Interactions

Oxidative dissolution potential of biogenic and abiogenic TcO2 in subsurface sediments

The role of low-temperature (off-axis) alteration of the oceanic crust in the global Li-cycle: Insights from the Troodos ophiolite

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