Distribution and sources of pre-anthropogenic lead isotopes in deep ocean water from FeMn crusts

Blanckenburg, Friedhelm von; O’Nions, R.K.; Heinz, J.

doi:10.1016/s0016-7037(96)00310-9

Cited by 93 publications

(48 citation statements)

References 29 publications

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“…If the Tethyan mantle from which Troodos had formed had a composition similar to that of the present-day Indian Ocean, this would limit the requirement for a subducted sediment component to explain the high 207 (Doe and Zartman, 1979;Spooner and Gale, 1982;Hamelin et al, 1988), glasses (Rautenschlein et al, 1985), Troodos sediments (Hamelin et al, 1988 and this study), and the Indian MORB array (Ito et al, 1987;Mahoney et al, 1989;Mahoney et al, 1998;Rehkämper and Hofmann, 1997). Fields for seawater were plotted using data from Mn nodules (Abouchamie and Goldstein, 1995;von Blanckenburg et al, 1996;Ling et al, 1997 Pb ratios of the epidosites and greenschist-altered dikes are especially puzzling because this ratio is nearly independent of any age correction. Therefore, it is clear that either these rocks are not the source rocks for the massive sulphides, or the supposed source rocks underwent a second "alteration event" that apparently did not influence the Pb isotopic composition of the sulphides enclosed in them.…”

Section: Resultsmentioning

confidence: 99%

Pb-isotope systematics of a fossil hydrothermal system from the Troodos ophiolite, Cyprus: Evidence for a polyphased alteration history

Booij

Bettison-Varga

Farthing

et al. 2000

Geochimica et Cosmochimica Acta

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Abstract-Pb-isotopic ratios have been determined on massive sulphides from the Troodos ophiolite and their inferred source rocks: epidosites and greenschist altered dikes. The latter have distinctly higher Pb-isotope ratios than the sulphides. The high 207 Pb/ 204 Pb ratios for the whole rocks indicate the involvement of an old (sedimentary) Pb-component. Extensive leaching of three epidosite samples shows that the radiogenic Pb can be removed and the resulting trend for the leached samples is consistent with a Pb-Pb age of ϳ95 Ma for these rocks. Inferred initial Pb isotope ratios are similar to those of the sulphides (this study) and fresh glasses from the Akaki Canyon in Cyprus. Therefore the Pb incorporated in the massive sulphides may originate from these greenschist facies hydrothermally altered rocks.The isotopic composition of the leachate Pb points toward a sedimentary origin. Calculation of the Pb-isotopic ratios for 90 Ma old "average" Troodos sediment shows that the "foreign" Pb in the epidosites may very well be derived from this source. This Pb probably does not reside within the mineral lattices of these metamorphic rocks, but rather is adsorbed on mineral surfaces or is present in microscopic particulate matter that may have been filtered from the circulating seawater. Unmodified seawater is considered an unlikely Pb source because of the extremely small dissolved Pb contents of seawater. Furthermore, no seawater or sedimentary signature is evident in the sulphides. Several models of Pb transport from different sources into these rocks may be envisaged, such as dissolution of Miocene evaporites and brine formation, equilibration of pore waters to the Pb isotope ratios of host sediments, and direct infiltration of deep sea particulate matter from the nepheloid layer. With the limited amount of data presently available it is impossible to critically determine the most likely processes of Pb transport.

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Section: Resultsmentioning

confidence: 99%

Pb-isotope systematics of a fossil hydrothermal system from the Troodos ophiolite, Cyprus: Evidence for a polyphased alteration history

Booij

Bettison-Varga

Farthing

et al. 2000

Geochimica et Cosmochimica Acta

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“…Further studies (Abouchami and Goldstein, 1995;von Blanckenburg et al, 1996) have shown that lead-isotope ratios from the surface layers of Fe-Mn nodules and crusts have similar patterns to neodymium isotopes. That is, they are consistent with an older continental provenance in the Atlantic and a younger one in the Pacific, and the present-day geographical distribution is consistent with dispersion of the signals by ocean circulation.…”

Section: Radiogenic Isotopes In Authigenic Ferromanganese Oxidesmentioning

confidence: 97%

Long-lived Isotopic Tracers in Oceanography, Paleoceanography, and Ice-sheet Dynamics

Goldstein

Hemming

2014

Treatise on Geochemistry

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“…Pb isotopes are suitable for the reconstruction of local inputs from land and their short distance mixing due to the shorter average residence time of Pb (50-200 years) in seawater (cf. von Blanckenburg et al, 1996).…”

Section: Tracing Weathering Inputs and Water-mass Mixing With Radiogementioning

confidence: 99%

The evolution of climatically driven weathering inputs into the western Arctic Ocean since the late Miocene: Radiogenic isotope evidence

Dausmann

Siebert

Christl

et al. 2015

Earth and Planetary Science Letters

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Distribution and sources of pre-anthropogenic lead isotopes in deep ocean water from FeMn crusts

Cited by 93 publications

References 29 publications

Pb-isotope systematics of a fossil hydrothermal system from the Troodos ophiolite, Cyprus: Evidence for a polyphased alteration history

Pb-isotope systematics of a fossil hydrothermal system from the Troodos ophiolite, Cyprus: Evidence for a polyphased alteration history

Long-lived Isotopic Tracers in Oceanography, Paleoceanography, and Ice-sheet Dynamics

The evolution of climatically driven weathering inputs into the western Arctic Ocean since the late Miocene: Radiogenic isotope evidence

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