Restricted internal oxygen isotope exchange in calcite veins: Constraints from fluid inclusion and clumped isotope-derived temperatures

Internal Water Facilitates Thermal Resetting of Clumped Isotopes in Biogenic Aragonite

“…The superscripts "UH" and "H" refer to the heated and unheated samples, respectively. Equation 1 was refined by Nooitgedacht et al, (2021) so that exchange between oxygen isotopes occurs only within the confines of CEF and exchange between fluid inclusions is temperature dependent, governed by the temperature-dependent fractionation factor α (e.g., Coplen, 2007;Daëron et al, 2019;Kim & O'Neil, 1997;Staudigel & Swart, 2018;Tremaine et al, 2011;Yan et al, 2012). The apparent fractionation of oxygen isotopes between carbonate and fluid inclusions is defined as follows:…”

“… Schematic representation of (a) a fluid inclusion in carbonate (i.e., liquid water trapped in carbonate) and (b) organic‐associated internal water in carbonate (i.e., carbonate bound to inter‐ and intracrystalline organic material). Hypothetically, the gray rim that surrounds the fluid inclusion, the Carbonate Exchange Fraction (CEF), marks the location where (1) oxygen isotope (δ 18 O) exchange by microscopic dissolution‐reprecipitation reactions occurs and (2) the clumped‐isotope (Δ 47 ) thermometer is reset (modified from Uemura et al., 2019 and Nooitgedacht et al., 2021). …”

“…A recent study investigated the covariance of fluid inclusion and host calcite oxygen isotope ratios as well as clumped isotopes of carbonate veins (Nooitgedacht et al., 2021). The oxygen isotope fractionation factor (α c‐fi ) between host carbonate (δ 18 O c ) and internal fluid (δ 18 O fi ) allows CaCO 3 precipitation temperature estimates assuming that precipitation took place in isotopic equilibrium (e.g., Coplen, 2007; Daëron et al., 2019; Kim & O'Neil, 1997; Staudigel & Swart, 2018; Tremaine et al., 2011; Yan et al., 2012).…”

“…The same idea was previously put forward by a heating experiment of speleothem calcite (Uemura et al., 2019). The fraction of calcite that is available for oxygen isotope exchange with the fluid inclusions has been termed as the Calcite Exchange Fraction (CEF; Nooitgedacht et al., 2021, Figure 1). This CEF, which is expected to vary between materials, could potentially explain the difference between inorganic and organic carbonate’s response to thermal alteration experiments: if in inorganic aragonite, less CaCO 3 is available for isotopic exchange (i.e., low CEF) than in biogenic aragonite, possibly reflecting a relatively low mineral‐fluid contact area or permeability, then fluid‐carbonate exchange is minimized and results in little change in ∆ 47 and δ 18 O fluid values.…”

“…More recently, it was proposed that clumped-isotope resetting in gastropod fossils occurred at very low NOOITGEDACHT ET AL. Hypothetically, the gray rim that surrounds the fluid inclusion, the Carbonate Exchange Fraction (CEF), marks the location where (1) oxygen isotope (δ 18 O) exchange by microscopic dissolution-reprecipitation reactions occurs and (2) the clumped-isotope (Δ 47 ) thermometer is reset (modified from Uemura et al, 2019 andNooitgedacht et al, 2021).…”