Isotopic Traces of Atmospheric O2 in Rocks, Minerals, and Melts

Pack, Andreas

doi:10.2138/rmg.2021.86.07

Cited by 27 publications

(21 citation statements)

References 95 publications

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“…Measured isotopic values are anchored to VSMOW using the composition of San Carlos olivine and UWG2 garnet (Pack, 2021; Pack et al., 2016; Sharp et al., 2016; Wostbrock et al., 2020). Data reduction was performed using either offset correction or intensity correction as required.…”

Section: Methodsmentioning

confidence: 99%

Isotopically Heavy Micrometeorites—Fragments of CY Chondrite or a New Hydrous Parent Body?

et al. 2022

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Cosmic dust grains sample a diverse range of solar system small bodies. This includes asteroids that are not otherwise represented in our meteorite collections. In this work we obtained 3D images of micrometeorite interiors using tomography before collecting destructive high‐precision oxygen isotope measurements. These data allow us to link textures in unmelted micrometeorites to known chondrite groups. In addition to identifying particles from ordinary chondrites, CR and CM chondrites we report two micrometeorites derived from an anomalous 16O‐poor source (δ17O: +16.4‰, δ18O: +28.4‰, and Δ17O: +1.4‰). Their compositions overlap with a previously reported micrometeorite (TAM50‐25) from Suttle et al. (2020), https://doi.org/10.1016/j.epsl.2020.116444 (EPSL: 546:116444). These particles represent hydrated carbonaceous chondrite material derived either from a new group or from the CY chondrites (thereby extending the isotopic range of this group). In either scenario they demonstrate close petrographic and isotopic connections to the CO‐CM chondrite clan. Furthermore, their position in O‐isotope space makes them the most likely candidate for the parent body of the anomalous “group 4” cosmic spherules previously reported by Suavet et al. (2010), https://doi.org/10.1016/j.epsl.2010.02.046 (EPSL: 293:313‐320) and several subsequent isotopic studies. We conclude that the “group 4” cosmic spherules originate from hydrated C‐type asteroid parents.

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Section: Methodsmentioning

confidence: 99%

Isotopically Heavy Micrometeorites—Fragments of CY Chondrite or a New Hydrous Parent Body?

et al. 2022

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“…Here, δ x O represents the deviation in parts per thousand (&, or "permil") from the x O/ 16 O ratio in an isotopic standard, and λ RL is a reference line slope that we take to be equal to 0.528, following Young et al (28) and Pack (27). For small fractionations, this reduces to…”

Section: Significancementioning

confidence: 99%

“…1) in all calculations, as the fractionation in ozone is not small. The positive Δ 017 O signal from ozone (∼26& at the surface) is transferred to CO 2 , and O 2 acquires a negative Δ 017 O signal (∼À0.43& at the surface) by mass balance (27). The Δ 017 O signal from atmospheric O 2 can be transferred to the rock record via weathering of pyrite, FeS 2 , and the subsequent burial of oxidized sulfur phases at Earth's surface (25,29,30).…”

Section: Significancementioning

confidence: 99%

“…The Δ 017 O signal from atmospheric O 2 can be transferred to the rock record via weathering of pyrite, FeS 2 , and the subsequent burial of oxidized sulfur phases at Earth's surface (25,29,30). (32,33) and À0.43& in tropospheric O 2 (27). By comparison, the existing oxygen isotope record from sedimentary sulfate minerals deposited during the Proterozoic shows values as light as À0.9& (25), requiring tropospheric O 2 values significantly lighter than those of the modern atmosphere.…”

Section: Significancementioning

confidence: 99%

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Triple oxygen isotope constraints on atmospheric O ₂ and biological productivity during the mid-Proterozoic

Liu

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Reconstructing the history of biological productivity and atmospheric oxygen partial pressure (pO2) is a fundamental goal of geobiology. Recently, the mass-independent fractionation of oxygen isotopes (O-MIF) has been used as a tool for estimating pO2 and productivity during the Proterozoic. O-MIF, reported as Δ′17O, is produced during the formation of ozone and destroyed by isotopic exchange with water by biological and chemical processes. Atmospheric O-MIF can be preserved in the geologic record when pyrite (FeS2) is oxidized during weathering, and the sulfur is redeposited as sulfate. Here, sedimentary sulfates from the ∼1.4-Ga Sibley Formation are reanalyzed using a detailed one-dimensional photochemical model that includes physical constraints on air–sea gas exchange. Previous analyses of these data concluded that pO2 at that time was <1% PAL (times the present atmospheric level). Our model shows that the upper limit on pO2 is essentially unconstrained by these data. Indeed, pO2 levels below 0.8% PAL are possible only if atmospheric methane was more abundant than today (so that pCO2 could have been lower) or if the Sibley O-MIF data were diluted by reprocessing before the sulfates were deposited. Our model also shows that, contrary to previous assertions, marine productivity cannot be reliably constrained by the O-MIF data because the exchange of molecular oxygen (O2) between the atmosphere and surface ocean is controlled more by air–sea gas transfer rates than by biological productivity. Improved estimates of pCO2 and/or improved proxies for Δ′17O of atmospheric O2 would allow tighter constraints to be placed on mid-Proterozoic pO2.

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“…Beyond the past ∼0.8 Ma covered by cores from inland ice sheets, no atmospheric O 2 is preserved in the geological record and proxies have been introduced for paleo‐[CO 2 ] reconstruction. A review on the traces of the isotope anomaly of air O 2 in the lithospheric materials has recently been published by Pack (2021). Bao et al.…”

Section: Introductionmentioning

confidence: 99%

I‐Type Cosmic Spherules as Proxy for the Δ′¹⁷O of the Atmosphere—A Calibration With Quaternary Air

Fischer

Oeser

Weyer

et al. 2021

Paleoceanog and Paleoclimatol

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No consensus has yet been reached on which slope of the reference line should be chosen. We choose a reference line with a slope of 0.528 in order to have a consistent terminology across disciplines (see discussion, e.g., in Miller & Pack, 2021, Pack & Herwartz, 2014, or Sharp & Wostbrock, 2021). However, any of the definitions of Δ' 17 O used in the literature, does not change the interpretation of triple oxygen isotope data. Modern tropospheric O 2 has a composition of δ 18 O = 24‰ (i.e., the 18 O/ 16 O ratio is 2.4% higher than in ocean water) and Δ′ 17 O = −0.432 ± 0.010‰ (

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Isotopic Traces of Atmospheric O2 in Rocks, Minerals, and Melts

Cited by 27 publications

References 95 publications

Isotopically Heavy Micrometeorites—Fragments of CY Chondrite or a New Hydrous Parent Body?

Isotopically Heavy Micrometeorites—Fragments of CY Chondrite or a New Hydrous Parent Body?

Triple oxygen isotope constraints on atmospheric O ₂ and biological productivity during the mid-Proterozoic

I‐Type Cosmic Spherules as Proxy for the Δ′¹⁷O of the Atmosphere—A Calibration With Quaternary Air

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Isotopic Traces of Atmospheric O2 in Rocks, Minerals, and Melts

Cited by 27 publications

References 95 publications

Isotopically Heavy Micrometeorites—Fragments of CY Chondrite or a New Hydrous Parent Body?

Isotopically Heavy Micrometeorites—Fragments of CY Chondrite or a New Hydrous Parent Body?

Triple oxygen isotope constraints on atmospheric O 2 and biological productivity during the mid-Proterozoic

I‐Type Cosmic Spherules as Proxy for the Δ′17O of the Atmosphere—A Calibration With Quaternary Air

Contact Info

Product

Resources

About

Triple oxygen isotope constraints on atmospheric O ₂ and biological productivity during the mid-Proterozoic

I‐Type Cosmic Spherules as Proxy for the Δ′¹⁷O of the Atmosphere—A Calibration With Quaternary Air