Quantitative Separation of Molybdenum and Rhenium from Geological Materials for Isotopic Determination by MC‐ICP‐MS

Pearce, Christopher R.; Cohen, A. S.; Parkinson, I. J.

doi:10.1111/j.1751-908x.2009.00012.x

Cited by 68 publications

(79 citation statements)

References 45 publications

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“…3 Mo with the TDS content of both samples (Fig. 4) Mo seawater =2.4‰; Barling et al, 2001;Siebert et al, 2003;Pearce et al, 2009), as this is ultimately the source of the water within the glacier (via rain and snowfall), and there is no evidence for significant anthropogenic pollution in this part of Iceland (Caritat et al, 2005). The preservation of such heavy δ…”

Section: /95mentioning

confidence: 99%

“…∼0‰; Siebert et al, 2003;Pearce et al, 2009) implies that the direct transfer of Mo from bedrock to solution during basalt weathering occurs with little accompanying isotope fractionation. This is consistent with leaching experiments on granite, which show that the Mo released is isotopically indistinguishable from the source rock (Siebert et al, 2003).…”

Section: /95mentioning

confidence: 99%

“…Molybdenum behaves conservatively in the oceans, with a uniform concentration of ∼ 120 nM and δ 98/95 Mo composition of ∼ 2.4‰ (Barling et al, 2001;Siebert et al, 2003;Anbar, 2004;Pearce et al, 2009). The relatively high abundance of Mo in present-day seawater reflects the stability of the dissolved MoO 4 2− species under oxidising conditions (Savenko, 1996), and results in a long oceanic residence time of ∼ 780 kyr (Manheim and Landergren, 1974;Colodner et al, 1995;Morford and Emerson, 1999).…”

Section: Borgarfjörður Estuary δ 98/95 Mo Profilementioning

confidence: 99%

“…Although artificial, the resulting ironprecipitates provide an analogue for natural Fe-Mn oxides that form in the river system. Riverine bedload samples were taken where possible, and have been found to contain a mixture of unweathered material and secondary clay phases (Pogge von Strandmann et al, 2006 Mo reproducibility of ±0.12‰ (2 standard deviation; Pearce et al, 2009). …”

Section: Sample Localitiesmentioning

confidence: 99%

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Molybdenum isotope behaviour accompanying weathering and riverine transport in a basaltic terrain

Pearce

Burton

Strandmann

et al. 2010

Earth and Planetary Science Letters

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101

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Editor: M.L. DelaneyKeywords: molybdenum (Mo) isotopes basaltic weathering riverine inputs estuarine mixingThe application of the molybdenum (Mo) isotope system as a proxy for determining changes in the redox state of the oceans is predicated on the assumption that the composition of continental input can be characterised from crustal rock types, and remains constant. However, it has recently been shown that the δ 98/95 Mo composition of global rivers varies between 0.15‰ and 2.4‰ and is therefore systematically heavier than the average composition of the continental crust (∼ 0‰ 4‰).Systematic changes in the dissolved Mo-isotope composition are also observed within river catchments, with δ 98/95 Mo values increasing from ∼ 0‰ in glacial rivers (close to the source) to ∼ 1‰ downstream, consistent with Mo-isotopes being fractionated during weathering. Analysis of other riverine phases (bedload, colloids and iron-precipitates) demonstrates that these phases preferentially incorporate light Moisotopes, and remain coupled to the dissolved load during riverine transportation. A δ 98/95 Mo profile through the Borgarfjörður estuary exhibits a predominantly conservative mixing behaviour, but suggests that the release of isotopically light Mo from the particulate and/or colloidal phases may occur in the low salinity part of the estuarine mixing zone.

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Section: /95mentioning

confidence: 99%

Section: /95mentioning

confidence: 99%

Section: Borgarfjörður Estuary δ 98/95 Mo Profilementioning

confidence: 99%

Section: Sample Localitiesmentioning

confidence: 99%

See 2 more Smart Citations

Molybdenum isotope behaviour accompanying weathering and riverine transport in a basaltic terrain

Pearce

Burton

Strandmann

et al. 2010

Earth and Planetary Science Letters

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101

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“…Recent developments in analytical techniques, particularly the advent of multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), have allowed the precise determination of differences in the isotopic composition of Mo between samples and reference standards Siebert et al, 2001;Pietruszka et al, 2006;Nakagawa et al, 2008;Pearce et al, 2009). The reactivity of Mo in aqueous solution is very dependent on redox conditions and coexisting ligands, leading to significant variations in Mo isotopic composition as well as Mo concentrations in natural waters (Bertine, 1972;Helz et al, 1996;Zheng et al, 2000;Vorlicek and Helz, 2002; Helz posed by Helz et al (1996) have a heavy isotopic signature (δ 98/95 Mo = 2.2 to 2.5‰; Barling et al, 2001;Arnold et al, 2004;Nägler et al, 2005;Neubert et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

The molybdenum isotopic composition of the modern ocean

et al. 2012

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Wang et al., 2011 (1) and is converted to δ 97/95 Mo by multiplying 0.67 when the system follows mass-dependent fractionation. Though no commonly-used Mo isotopic standard currently exists (see later), the standards used by different laboratories do appear to be isotopically similar at the level of 0.1-0.2‰. Continental rock samples, such as granite, basalt, and clastic sediments, have δ 98/95 Mo of ~0.1‰ Siebert et al., 2003). Ferromanganese oxides, which scavenge Mo from seawater in oxic conditions, have a light isotopic signature (δ 98/95 Mo = -1.0 to -0.5‰; Siebert et al., 2003), whereas sediments formed in euxinic conditions (aqueous H 2 S concentrations higher than ~11 µM, the action point pro-The molybdenum isotopic composition of the modern ocean (Received September 13, 2011; Accepted January 5, 2012) Natural variations in the isotopic composition of molybdenum (Mo) are showing increasing potential as a tool in geochemistry. Although the ocean is an important reservoir of Mo, data on the isotopic composition of Mo in seawater are scarce. We have recently developed a new method for the precise determination of Mo isotope ratios on the basis of preconcentration using a chelating resin and measurement by multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), which allows us to measure every stable Mo isotope . In this study, 172 seawater samples obtained from 9 stations in the Pacific, Atlantic, and Southern Oceans were analyzed, giving global coverage and the first full depth-profiles. The average isotope composition in δ Three-isotope plots for the Mo isotopes were fitted with straight lines whose slopes agreed with theoretical values for mass-dependent isotope fractionation. These results demonstrate that Mo isotopes are both uniformly distributed and follow a mass-dependent fractionation law in the modern oxic ocean. In addition, Mo isotopic analysis revealed that δ 98/95 Mo of the standard used in this study was 0.117 ± 0.009‰ lighter than the Mo standard that was used by Archer and Vance (2008). A common Mo standard is urgently required for the precise comparison of Mo isotopic compositions measured in different laboratories. On the other hand, our results strongly support the possibility of seawater as an international reference material for Mo isotopic composition.

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The spread of marine anoxia on the northern Tethys margin during the Paleocene-Eocene Thermal Maximum

et al. 2014

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Records of the paleoenvironmental changes that occurred during the Paleocene-Eocene Thermal Maximum (PETM) are preserved in sedimentary rocks along the margins of the former Tethys Ocean and Peri-Tethys. This paper presents new geochemical data that constrain paleoproductivity, sediment delivery, and seawater redox conditions, from three sites that were located in the Peri-Tethys region. Trace and major element, iron speciation, and biomarker data indicate that water column anoxia was established during episodes when inputs of land-derived higher plant organic carbon and highly weathered detrital clays and silts became relatively higher. Anoxic conditions are likely to have been initially caused by two primary processes: (i) oxygen consumption by high rates of marine productivity, initially stimulated by the rapid delivery of terrestrially derived organic matter and nutrients, and (ii) phosphorus regeneration from seafloor sediments. The role of the latter process requires further investigation before its influence on the spread of deoxygenated seawater during the PETM can be properly discerned. Other oxygen-forcing processes, such as temperature/salinity-driven water column stratification and/or methane oxidation, are considered to have been relatively less important in the study region. Organic carbon enrichments occur only during the initial stages of the PETM as defined by the negative carbon isotope excursions at each site. The lack of observed terminal stage organic carbon enrichment does not support a link between PETM climate recovery and the sequestration of excess atmospheric CO 2 as organic carbon in this region; such a feedback may, however, have been important in the early stages of the PETM.

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Quantitative Separation of Molybdenum and Rhenium from Geological Materials for Isotopic Determination by MC‐ICP‐MS

Cited by 68 publications

References 45 publications

Molybdenum isotope behaviour accompanying weathering and riverine transport in a basaltic terrain

Molybdenum isotope behaviour accompanying weathering and riverine transport in a basaltic terrain

The molybdenum isotopic composition of the modern ocean

The spread of marine anoxia on the northern Tethys margin during the Paleocene-Eocene Thermal Maximum

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