Triple Oxygen Isotope Trend Recorded by Precambrian Cherts: A Perspective from Combined Bulk and in situ Secondary Ion Probe Measurements

A CO 2 greenhouse efficiently warmed the early Earth and decreased seawater 18 O/ 16 O before the onset of plate tectonics

“…2). This is presently acknowledged as a strong argument against low δ 18 O sw as an explanation for the low δ 18 O of Precambrian chemical sediments (24)(25)(26)(27)31). Most of the Δ' 17 O chert data do not fall on the black equilibrium curve in Fig.…”

“…In order to explain the enigmatic shift in δ 18 O of ∼15‰ of chemical sediments through time (21)(22)(23)(24)(25)(26)(27)(28), extreme and difficult-to-reconcile changes of oxygen fluxes F i are required (20,29). As shown in Fig.…”

Reconstructing Past Elevations From Triple Oxygen Isotopes of Lacustrine Chert: Application to the Eocene Nevadaplano, Elko Basin, Nevada, United States

“…We generated O 2 gas from silicates using the laser fluorination method after Sharp (1990), on the setup described in Chamberlain et al (2020) (see also Sharp et al, 2016;Wostbrock et al, 2018Wostbrock et al, , 2020Lowe et al, 2020;Kukla et al, 2021). This setup is similar to recent studies from other labs producing triple oxygen isotope measurements of chert and silica (Pack and Herwartz, 2014;Levin et al, 2014;Liljestrand et al, 2020;Sengupta et al, 2020;Zakharov et al, 2021). Two to four micrograms of samples are loaded into the vacuum line sample chamber.…”

“…We are interested in oxygen isotope fractionation between water and minerals (CaCO 3 -H 2 O and SiO 2 -H 2 O), as well as oxygen isotope fractionation between liquid and vapor water during lake water evaporation. Following the recent triple oxygen isotope literature (e.g., Pack and Herwartz, 2014;Passey et al, 2014;Sharp et al, 2018;Barkan et al, 2019;Passey and Ji, 2019;Liljestrand et al, 2020;Bindeman, 2021;Herwartz, 2021;Zakharov et al, 2021), we report our oxygen isotope data using linear notation, which removes curvature when comparing δ 18 O and δ 17 O variations (Hulston and Thode, 1965;Miller, 2002):…”

“…variations in θ for Earth-surface processes like the temperature dependence of equilibrium fractionation during mineral precipitation (θ = 0.5237-0.5255 for SiO 2 -H 2 O fractionation from 0 to 100 • C; Cao and Liu, 2011;Sharp et al, 2016;Hayles et al, 2017;Wostbrock et al, 2018), equilibrium condensation and evaporation of water vapor (θ = 0.529; Barkan and Luz, 2005), and water vapor diffusion (θ = 0.5185; Barkan and Luz, 2007;θ = 0.5194;Yeung et al, 2018), all of which are lower than the theoretical infinite-temperature end-member (θ = 0.5305; Matsuhisa et al, 1978;Young et al, 2002). To visualize variations graphically and normalize to a specific process (Meijer and Li, 2006;Passey et al, 2014;Sharp et al, 2016Sharp et al, , 2018Barkan et al, 2019;Passey and Ji, 2019;Sha et al, 2020;Bindeman, 2021;Herwartz, 2021;Miller and Pack, 2021;Zakharov et al, 2021) we define a reference slope λ RL to look at small deviations in δ 17 O relative to δ 18 O using 17 O notation (sometimes also denoted 17 O-excess):…”