Oxygen isotopic composition of phosphorites from marine formations

Longinelli, A.; Nuti, S.

doi:10.1016/s0012-821x(68)80003-2

Cited by 60 publications

(13 citation statements)

References 5 publications

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“…1; Veizer et al, 1999). In addition, parallel secular trends, offset by their mineral-specific fractionation factors, have been documented also for siliceous (e.g., Perry, 1967;Knauth and Epstein, 1976;Kolodny and Epstein, 1976;Knauth and Lowe, 1978) and phosphatic (e.g., Longinelli and Nuti, 1968;Kolodny and Luz, 1991;Song et al, 2019) minerals and shells. All of this demonstrates that the δ 18 O secular trends are primary features of the geologic record, where the secondary resetting phenomena contribute only superimposed scatter, mostly within the secular bands.…”

Section: Introductionmentioning

confidence: 87%

On plate tectonics and ocean temperatures

Vérard

Veizer

2019

Geology

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Plate tectonics, the principal vehicle for dissipation of planetary energy, is believed to buffer the δ18O of seawater at its near-modern value of 0‰ SMOW (Standard Mean Ocean Water) because the hot and cold cells of hydrothermal circulation at oceanic ridges cancel each other. The persistence of plate tectonics over eons apparently favors attribution of the well-documented oxygen isotope secular trends for carbonates (cherts, phosphates) to progressively warmer oceans, from 40–70 °C in the early Paleozoic to 60–100 °C in the Archean. We argue that these oceanic hydrothermal systems are dominated by low-temperature (<350 °C) cells that deplete the percolating water in 18O. Seawater δ18O is therefore a proxy for, rather than being buffered by, the intensity of plate tectonics. Detrending the Phanerozoic carbonate δ18Oc secular trend for its “tectonic” component yields a stationary time series that, interpreted as a proxy for Phanerozoic climate, indicates low-latitude shallow ocean temperatures oscillating between 10 and 30 °C around a baseline of 17 °C, attributes comparable to modern temperature values.

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Section: Introductionmentioning

confidence: 87%

On plate tectonics and ocean temperatures

Vérard

Veizer

2019

Geology

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“…Shemesh and others were able to attribute some of the change in <518O over time to differences in the <518O of sea water that precipitated the phosphorites, but they also attributed some of the change to phosphorite formation at higher temperatures in the past. The lowest <518O value in phosphates was measured on samples from Montana and Tennessee (Longinelli and Nuti, 1968), both with a value of +8.6 %0.…”

mentioning

confidence: 85%

Compilation of minimum and maximum isotope ratios of selected elements in naturally occurring terrestrial materials and reagents

Coplen¹,

Hopple²,

Böhlke³

et al. 2002

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“…There has been much debate in the literature concerning the significance of the secular trends of l8 O-depletion with geological age noted for carbonates by Veizer & Hoefs (1976), and also for cherts (Knauth & Epstein, 1976;Knauth & Lowe, 1978) and apatites (Longinelli & Nuti, 1968;Shemesh, Kolodny & Luz, 1983, 1988. The debate has centred around the question of whether the ancient (Precambrian) oceans were depleted in 18 O relative to present-day oceanwater, or if the older oceans were warmer.…”

Section: Sa Dolomitesmentioning

confidence: 99%

Chemical and stable isotope fractionation in manganese oxide—phosphorite mineralization, Timna Valley, Israel

Bar‐Matthews

Matthews

1990

Geol. Mag.

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Element, carbon and oxygen isotope fractionations have been studied in laminated deposits, manganese nodules and phosphorite lenses in clastic sediments of the Cambrian Timna Formation, southern Israel. Comparisons of element abundances show that only manganese, phosphorus and uranium were mobilized and concentrated during diagenesis: element fractionations among the diagenetic manganese components particularly resemble those observed in present-day suboxic pelagic marine sediments. Epigenetic processes involving reducing solutions reversed the diagenetic geochemical trends, with the redox-sensitive elements manganese and uranium showing considerable depletions in nodules, and iron and lead showing corresponding enrichments. The manganese oxides of nodules have calculated δ18O compositions varying from –1.6 to 3.1 ‰. These compositions are significantly lower than a δ18O value of 7.9 ‰ obtained for the manganese oxides of an ocean floor nodule and are taken to largely represent temperature differences between the ocean floor and the shallow marine Timna conditions. Slight decreases in δ18O accompany the transformation from diagenetic type A to epigenetic type B manganese nodules; corresponding shifts to lower δ18O are also inferred for the structural carbonate of apatites. Such shifts are compatible with re-equilibration accompanying a slight temperature increase and/or low temperature meteoric-water alteration. δ13C values of –7 to –12‰ obtained for the apatites of laminated deposits and phosphorite lenses are consistent with phosphorite diagenesis in suboxic to anoxic pore-waters. Early diagenetic redox conditions are indicated to be major controls governing the development of the assemblages.

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Oxygen isotopic composition of phosphorites from marine formations

Cited by 60 publications

References 5 publications

On plate tectonics and ocean temperatures

On plate tectonics and ocean temperatures

Compilation of minimum and maximum isotope ratios of selected elements in naturally occurring terrestrial materials and reagents

Chemical and stable isotope fractionation in manganese oxide—phosphorite mineralization, Timna Valley, Israel

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