Bacterial and abiogenic carbonates formed in caves–no vital effect on clumped isotope compositions

Speleothems (dominated by cave-hosted carbonate deposits) are valuable archives of paleoclimate conditions. As such, they are potential targets of clumped isotope analyses that may yield quantified data about past temperature variations. Clumped isotope analyses of stalagmites, however, seldom provide useful temperature values due to various isotope fractionation processes. This study focuses on the determination of the microbially induced vital effect, i.e., the isotope fractionation processes related to bacterial carbonate production. A cave site with biologically mediated amorphous calcium carbonate precitation was selected as a natural laboratory. Calcite deposits were farmed under a UV lamp to prevent bacterial activity, as well as under control conditions. Microbiological analyses and morphological investigations using scanning electron microscopy showed that the UV lamp treatment effectively reduced the number of bacterial cells, and that bacterial carbonate production strongly influenced the carbonate’s morphology. Stable oxygen isotope analyses of calcite and drip waters, as well as clumped isotope measurements revealed that, although most of the studied carbonates formed close to oxygen isotope equilibrium, clumped isotope Δ47 values varied widely from equilibrium to strongly fractionated data. Site-specific kinetic fractionations played a dominant role in the distribution of Δ47 values, whereas bacterial carbonate production did not result in a detectable clumped isotope effect.

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Oxygen isotope fractionation between rutile and water and geothermometry of metamorphic eclogites

Mineralogical Magazine ◽

10.1180/minmag.1979.043.327.14 ◽

1979 ◽

Vol 43 (327) ◽

pp. 405-413 ◽

Cited By ~ 18

Author(s):

Alan Matthews ◽

Robert D. Beckinsale ◽

John J. Durham

Keyword(s):

Oxygen Isotope ◽

Isotope Fractionation ◽

Western Alps ◽

Titanium Metal ◽

Isotopic Equilibrium ◽

Oxygen Isotope Fractionation ◽

Tauern Window ◽

Theoretical Predictions ◽

Aqueous Oxidation ◽

Isotope Analyses

SummaryOxygen isotope fractionation between rutile and water has been studied from 300 °C to 700 °C, PH2O = 1 kb, using aqueous oxidation of titanium metal as the equilibration reaction. The mechanism of rutile formation (which is critical to the assessment of isotopic equilibrium) is an ‘armouring’ reaction in which rutile grows around grains of titanium metal by solution-precipitation processes. Mean fractionation factors expressed as 103 In αTiO2-H2O obtained in the present study are:−6.20±0.23‰ at 304±5 °C−6.64±0.27‰ at 405±6 °C−6.11±0.16%. at 508±6 °C−4.45±0.28%. at 608±6 °C−3.38±0.15%. at 698±6 °C.These data agree with those obtained at temperatures above 500 °C by Addy and Garlick (1974) but do not accord with theoretical predictions by Bottinga and Javoy (1973). A minimum in the calibration curve 103 ln α versus 106T−2 occurs between 300 °C and 500 °C but from 500 °C to 700 °C 18O fractionation between rutile and water may be expressed by the equation:103 ln α = −(4.72±0.40)106T−2+(1.62±0.53).Oxygen isotope analyses of rutile and quartz from metamorphic eclogites and schists from the Tauern Window, Austria, yield isotopic temperatures at about 550 °C in agreement with results obtained on similar rocks from the Sesia Zone (Western Alps, Italy) and elsewhere by other workers. Petrologic studies indicate that the latest metamorphism of the Tauern eclogites reached about 450 °C Thus the measured partitions of 18O between rutile and quartz indicating temperatures around 550 °C have been inherited from an earlier metamorphic event.

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Technical Note: A simple method for vaterite precipitation in isotopic equilibrium: implications for bulk and clumped isotope analysis

Biogeosciences Discussions ◽

10.5194/bgd-11-17361-2014 ◽

2014 ◽

Vol 11 (12) ◽

pp. 17361-17390 ◽

Cited By ~ 1

Author(s):

T. Kluge ◽

C. M. John

Keyword(s):

Oxygen Isotope ◽

Isotope Fractionation ◽

Isotope Analysis ◽

Technical Note ◽

Major Constituent ◽

Simple Method ◽

Oxygen Isotope Fractionation ◽

Clumped Isotope ◽

Synthetic Precipitation ◽

A Minor

Abstract. Calcium carbonate (CaCO3) plays an important role in the natural environment as a major constituent of the skeleton and supporting structure of marine life and has high economic importance as additive in food, chemicals and medical products. Pure CaCO3 occurs in the three different polymorphs calcite, aragonite and vaterite, whereof calcite is the most abundant and best characterized mineral. In contrast, little is known about the rare polymorph vaterite, in particular with regard to the oxygen isotope fractionation between H2O and the mineral. Synthetic precipitation of vaterite in the laboratory typically involves rapid processes and isotopic non-equilibrium, which excludes isotope studies focused on characterization of vaterite at equilibrium conditions. Here, we used a new experimental approach that enables vaterite mineral formation from an isotopically equilibrated solution. The solution consists of a ~ 0.007 mol L-1 CaCO3 solution that is saturated with NaCl at room temperature (up to 6.5 mol L-1). Vaterite precipitated as single phase or major phase (≥ 94%) in experiments performed between 23 and 91 °C. Only at 80 °C was vaterite a minor phase with a relative abundance of 27%. The high mineral yield of up to 235 mg relative to a total dissolved CaCO3 amount of 370 mg enables an investigation of the oxygen isotope fractionation between mineral and water, and the determination of clumped isotope values in vaterite.

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Belemnites, clumped isotopes and oxygen fractionation

10.5194/egusphere-egu2020-260 ◽

2020 ◽

Author(s):

Madeleine Vickers ◽

Stefano Bernasconi ◽

Clemens Ullmann ◽

Stephen Hesselbo ◽

Gregory Price ◽

...

Keyword(s):

Oxygen Isotope ◽

Isotope Fractionation ◽

Clumped Isotopes ◽

Fractionation Factor ◽

Oxygen Isotope Fractionation ◽

Temperature Reconstructions ◽

Life Habits ◽

Stable Oxygen ◽

Clumped Isotope ◽

Low Precipitation

Belemnite calcite has been used extensively for Jurassic and Cretaceous stable oxygen isotope temperature reconstructions since the 1950s. However, with the advent of clumped isotope thermometry, a consistent offset between reconstructed &#948;18O temperatures vs &#916;47 temperatures from the same belemnites has been observed. We investigate the causes of this offset by analyzing samples from the aragonitic phragmacone and calcitic rostrum from the same Cylindroteuthis belemnites, along with other aragonitic benthos, from the Callovian-aged Christian Malford Lagerst&#228;tte, U.K. Our new clumped isotope data suggest that the water-calcite 18O-fractionation factor in belemnite calcite was larger than that of the commonly used &#948;18O thermometry equations (e.g. Kim and O&#8217;Neil, 1997), and which is currently observed in other marine calcifiers. Our reconstructions suggest that the oxygen isotope fractionation is compatible with that observed in slow-forming abiotic calcites (e.g. Coplen, 2007) and in rapidly precipitating Travertines (Kele et al. 2015). The application of more established &#948;18O thermometry equations (Kim and O&#8217;Neil, 1997) to belemnite calcite for temperature reconstructions has resulted in a consistent underestimation of belemnite calcification temperatures, which has led to erroneous conclusions about belemnite life habits, and underestimation of global temperatures during these greenhouse times. We therefore advocate the use of calcite equations based on low precipitation rate experiments (e.g. Coplen, 2007; Kele et al., 2015) for belemnite rostra temperature reconstructions.

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Technical Note: A simple method for vaterite precipitation for isotopic studies: implications for bulk and clumped isotope analysis

Biogeosciences ◽

10.5194/bg-12-3289-2015 ◽

2015 ◽

Vol 12 (11) ◽

pp. 3289-3299 ◽

Cited By ~ 4

Author(s):

T. Kluge ◽

C. M. John

Keyword(s):

Oxygen Isotope ◽

Isotope Fractionation ◽

Isotope Analysis ◽

Technical Note ◽

Major Constituent ◽

Simple Method ◽

Oxygen Isotope Fractionation ◽

Clumped Isotope ◽

Synthetic Precipitation ◽

A Minor

Abstract. Calcium carbonate (CaCO3) plays an important role in the natural environment as a major constituent of the skeleton and supporting structure of marine life and has high economic importance as an additive in food, chemicals and medical products. Anhydrous CaCO3 occurs in the three different polymorphs calcite, aragonite and vaterite, whereof calcite is the most abundant and best characterized mineral. In contrast, little is known about the rare polymorph vaterite, in particular with regard to the oxygen isotope fractionation between H2O and the mineral. Synthetic precipitation of vaterite in the laboratory typically involves rapid processes and isotopic non-equilibrium, which excludes isotope studies focused on the characterization of vaterite under equilibrium conditions. Here, we used a new experimental approach that enables vaterite mineral formation from an isotopically equilibrated solution. The solution consists of a ~0.007 mol L−1 CaCO3 solution that is saturated with NaCl at room temperature (up to 6.4 mol L−1). Vaterite precipitated as single phase or major phase (≥94%) in experiments performed between 23 and 91 °C. Only at 80 °C was vaterite a minor phase with a relative abundance of 27%. The high mineral yield per experiment of up to 235 mg relative to the initially dissolved CaCO3 amount of on average 360 mg enables an investigation of the oxygen isotope fractionation between the mineral and water, and the determination of clumped isotope values in vaterite.

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