Iron isotope fractionation during oceanic crust alteration

Rouxel, Olivier; Dobbek, Nicolas; Ludden, John; Fouquet, Yves

doi:10.1016/j.chemgeo.2003.08.011

Cited by 243 publications

(198 citation statements)

References 43 publications

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“…Fluid-rock interaction and exsolution of aqueous fluids could preferentially remove light iron isotopes from bulk rock and is an important mechanism for iron chemical and isotope fractionation in both low-and high-temperature processes on Earth (Rouxel et al, 2003;Poitrasson and Freydier, 2005;Chapman et al, 2009). Thus, the fingerprint of aqueous fluid interaction in eucritic rocks could be detected using Fe isotopes.…”

Section: Iron Isotopes and Fluid-rock Interactions On Asteroidal Bodiesmentioning

confidence: 99%

Iron isotope fractionation in planetary crusts

Wang

Moynier

Dauphas

et al. 2012

Geochimica et Cosmochimica Acta

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We present new high precision iron isotope data (d 56 Fe vs. IRMM-014 in per mil) for four groups of achondrites: one lunar meteorite, 11 martian meteorites, 32 howardite-eucrite-diogenite meteorites (HEDs), and eight angrites. Angrite meteorites are the only planetary materials, other than Earth/Moon system, significantly enriched in the heavy isotopes of Fe compared to chondrites (by an average of +0.12& in d 56 Fe). While the reason for such fractionation is not completely understood, it might be related to isotopic fractionation by volatilization during accretion or more likely magmatic differentiation in the angrite parent-body. We also report precise data on martian and HED meteorites, yielding an average d 56 Fe of 0.00 ± 0.01&. Stannern-trend eucrites are isotopically heavier by +0.05& in d 56 Fe than other eucrites. We show that this difference can be ascribed to the enrichment of heavy iron isotopes in ilmenite during igneous differentiation. Preferential dissolution of isotopically heavy ilmenite during remelting of eucritic crust could have generated the heavy iron isotope composition of Stannern-trend eucrites. This supports the view that Stannern-trend eucrites are derived from main-group eucrite source magma by assimilation of previously formed asteroidal crust.These new results show that iron isotopes are not only fractionated in terrestrial and lunar basalts, but also in two other differentiated planetary crusts. We suggest that igneous processes might be responsible for the iron isotope variations documented in planetary crusts.

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Section: Iron Isotopes and Fluid-rock Interactions On Asteroidal Bodiesmentioning

confidence: 99%

Iron isotope fractionation in planetary crusts

Wang

Moynier

Dauphas

et al. 2012

Geochimica et Cosmochimica Acta

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“…Nevertheless, relatively thick Fe-Si rich hydrothermal deposits have been documented in the recent rock record. For example, silicaand iron-rich deposits as much as 20 m thick have been reported at ODP Site 801 within Jurassic oceanic crust in the western Pacific (Alt et al, 1992;Rouxel et al, 2003), and fossil hydrothermal Si-Fe deposits, with umber, jasper, and iron formation, have been reported in ophiolites as old as 490 Ma (Little et al, 2004).…”

Section: Modern Iron-rich Sedimentsmentioning

confidence: 99%

Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes

Bekker¹,

Krapež²,

Slack³

et al. 2010

Economic Geology

849

494

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Iron formations are economically important sedimentary rocks that are most common in Precambrian sedimentary successions. Although many aspects of their origin remain unresolved, it is widely accepted that secular changes in the style of their deposition are linked to environmental and geochemical evolution of Earth. Two types of Precambrian iron formations have been recognized with respect to their depositional setting. Algoma-type iron formations are interlayered with or stratigraphically linked to submarine-emplaced volcanic rocks in greenstone belts and, in some cases, with volcanogenic massive sulfide (VMS) deposits. In contrast, larger Superior-type iron formations are developed in passive-margin sedimentary rock successions and generally lack direct relationships with volcanic rocks. The early distinction made between these two iron-formation types, although mimimized by later studies, remains a valid first approximation. Texturally, iron formations were also divided into two groups. Banded iron formation (BIF) is dominant in Archean to earliest Paleoproterozoic successions, whereas granular iron formation (GIF) is much more common in Paleoproterozoic successions. Secular changes in the style of iron-formation deposition, identified more than 20 years ago, have been linked to diverse environmental changes. Geochronologic studies emphasize the episodic nature of the deposition of giant iron formations, as they are coeval with, and genetically linked to, time periods when large igneous provinces (LIPs) were emplaced. Superior-type iron formation first appeared at ca. 2.6 Ga, when construction of large continents changed the heat flux at the core-mantle boundary. From ca. 2.6 to ca. 2.4 Ga, global mafic magmatism culminated in the deposition of giant Superior-type BIF in South Africa, Australia, Brazil, Russia, and Ukraine. The younger BIFs in this age range were deposited during the early stage of a shift from reducing to oxidizing conditions in the ocean-atmosphere system. Counterintuitively, enhanced magmatism at 2.50 to 2.45 Ga may have triggered atmospheric oxidation. After the rise of atmospheric oxygen during the GOE at ca. 2.4 Ga, GIF became abundant in the rock record, compared to the predominance of BIF prior to the Great Oxidation Event (GOE). Iron formations generally disappeared at ca. 1.85 Ga, reappearing at the end of the Neoproterozoic, again tied to periods of intense magmatic activity and also, in this case, to global glaciations, the so-called Snowball Earth events. By the Phanerozoic, marine iron deposition was restricted to local areas of closed to semiclosed basins, where volcanic and hydrothermal activity was extensive (e.g., backarc basins), with ironstones additionally being linked to periods of intense magmatic activity and ocean anoxia.Late Paleoproterozoic iron formations and Paleozoic ironstones were deposited at the redoxcline where biological and nonbiological oxidation occurred. In contrast, older iron formations were deposited in anoxic oceans, where ferrous iron oxid...

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“…depleted fluids, indicating that the production of high-metal hydrothermal fluids itself is a fractionating process (ROUXEL et al, 2003;ROUXEL et al, 2004;SEVERMANN et al, 2004). Second, the precipitation of Fe sulfides has a kinetic isotope effect Δ…”

Section: Dissolved Iron Distribution Size Partitioning and Stable Imentioning

confidence: 99%

The marine biogeochemistry of dissolved and colloidal Iron

Fitzsimmons¹

2013

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Iron is a redox active trace metal micronutrient essential for primary production and nitrogen acquisition in the open ocean. Dissolved iron (dFe) has extremely low concentrations in marine waters that can drive phytoplankton to Fe limitation, effectively linking the Fe and carbon cycles. Understanding the marine biogeochemical cycling and composition of dFe was the focus of this thesis, with an emphasis on the role of the size partitioning of dFe (<0.2µm) into soluble (sFe<0.02µm) and colloidal (0.02µm1 nmol/kg) concentrations coincident with the oxygen minimum zone were determined to be caused by remineralization of a high Fe:C organic material (vertical flux), instead of a laterally advected low oxygen-high dFe plume from the African margin. In the South Pacific Ocean, dFe maxima near 2000m were determined by comparison with dissolved manganese and 3 He to be caused by hydrothermal venting. The location of these stations hundreds to thousands of kilometers from the nearest vents confirms the "leaky vent" hypothesis that enough dFe escapes precipitation at the vent site to contribute significantly to abyssal dFe inventories.The size partitioning of dFe was also investigated in order to trace the role of dFe composition on its cycling. First, the two most commonly utilized methods of sFe filtration were compared: cross flow filtration (CFF) and Anopore filtration. Both were found to be robust sFe collection methods, and sFe filtrate through CFF (10 kDa) was found to be only 74±21% of the sFe through Anopore (0.02µm) filters at 28 locations, a function of both pore size differences and the natural variability in distribution of 10kDa-0.02µm colloids. In the North Atlantic, a colloidal-dominated partitioning was observed in the surface ocean underlying the North African dust plume, in and downstream of the TAG hydrothermal system, and along the western Atlantic margin. However, cFe was depleted or absent at the deep chlorophyll maximum. A summary model of dFe size partitioning in the North Atlantic open ocean is presented in conclusion, hypothesizing that a constant dFe exchange between soluble and colloidal pools modulates the constant partitioning of nearly 50% dFe into the colloidal phase throughout the subsurface North Atlantic Ocean, while sFe and cFe cycle independently in the upper ocean.Thesis supervisor: Edward A. Boyle, Professor of Ocean Geochemistry, MIT 4 5

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Iron isotope fractionation during oceanic crust alteration

Cited by 243 publications

References 43 publications

Iron isotope fractionation in planetary crusts

Iron isotope fractionation in planetary crusts

Iron Formation: The Sedimentary Product of a Complex Interplay among Mantle, Tectonic, Oceanic, and Biospheric Processes

The marine biogeochemistry of dissolved and colloidal Iron

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