Online oxygen (δ 18 O) and hydrogen (δ 2 H) isotope analysis of fluid inclusion water entrapped in minerals is widely applied in paleo-fluid studies. In the state of the art of fluid inclusion isotope research, however, there is a scarcity of reported inter-technique comparisons to account for possible analytical offsets.Along with improving analytical precisions and sample size limitations, interlaboratory comparisons can lead to a more robust application of fluid inclusion isotope records.Methods: Mineral samples-including speleothem, travertine, and vein materialwere analyzed on two newly setup systems for fluid inclusion isotope analysis to provide an inter-platform comparison. One setup uses a crusher unit connected online to a continuous-flow pyrolysis furnace and an isotope ratio mass spectrometry (IRMS) instrument. In the other setup, a crusher unit is lined up with a cavity ringdown spectroscopy (CRDS) system, and water samples are analyzed on a continuous standard water background to achieve precisions on water injections better than 0.1‰ for δ 18 O values and 0.4‰ for δ 2 H values for amounts down to 0.2 μL.Results: Fluid inclusion isotope analyses on the IRMS setup have an average 1σ reproducibility of 0.4‰ and 2.0‰ for δ 18 O and δ 2 H values, respectively. The CRDS setup has a better 1σ reproducibility (0.3‰ for δ 18 O values and 1.1‰ for δ 2 H values) and also a more rapid sample throughput (<30 min per sample). Fluid inclusion isotope analyses are reproducible at these uncertainties for water amounts down to 0.1 μL on both setups. Fluid inclusion isotope data show no systematic offsets between the setups. Conclusions:The close match in fluid inclusion isotope results between the two setups demonstrates the high accuracy of the presented continuous-flow techniques for fluid inclusion isotope analysis. Ideally, experiments such as the one presented in this study will lead to further interlaboratory comparison efforts and the selection of suitable reference materials for fluid inclusion isotopes studies.
DR 1: Determining conservativeness of Brand Mg 2+ in pore fluids Regression analysis was employed to assess the magnitude of conservativeness for Brand Mg 2+ (DR Fig. 1B and 1C) in all pore fluid samples. This was carried out by plotting the relative degree of evaporation (D.E), or molal concentrations (mol•Kg(H 2 O)-1) normalized to Dead Sea concentrations (Eq.1), against each other (i.e. D.E. Br vs. D.E. Mg ; DR Fig. 2). Assuming a relatively stable inventory of Brand Mg 2+ (chemical species i) in the deep lake over the past 220 kyrs, the degree of evaporation should be approximate to the ratio of H 2 O (kg) in the modern Dead Sea, relative to pore fluids H 2 O (kg): (1) The plot yields values along a linear trend of y= x, as should be expected for conservative ions (DR Fig. 2). 95% of values fall within a confidence interval of y = x ±0.14. Data points outside the confidence intervals indicate relative non-conservativity and are removed from the pore fluid records (DR table 1). On the plot (DR Fig. 2) a theoretical 139.6 43.946 ± 0.717 Radiocarbon 157.94 55.864 ± 5.627 Radiocarbon
Thick halite intervals recovered by the Dead Sea Deep Drilling Project cores show evidence for severely arid climatic conditions in the eastern Mediterranean during the last three interglacials. In particular, the core interval corresponding to the peak of the last interglacial (Marine Isotope Stage 5e or MIS 5e) contains ~30 m of salt over 85 m of core length, making this the driest known period in that region during the late Quaternary. This study reconstructs Dead Sea lake levels during the salt deposition intervals, based on water and salt budgets derived from the Dead Sea brine composition and amount of salt in the core. Modern water and salt budgets indicate that halite precipitates only during declining lake levels, while the amount of 2 dissolved Na + and Claccumulates during wetter intervals. Based on the compositions of Dead 24 Sea brines from pore waters and halite fluid inclusions, we estimate that ~12-16 cm of halite 25 precipitated per meter of lake-level drop. During periods of halite precipitation, the Mg 2+ 26 concentration increases and the Na + /Clratio decreases in the lake. Our calculations indicate 27 major lake-level drops of ~170 m from lake levels of 320 and 310 m below sea level (mbsl) 28 down to lake levels of ~490 and ~480 mbsl, during MIS 5e and the Holocene, respectively. 29These lake leves are much lower than typical interglacial lake levels of around 400 mbsl. These 30 lake-level drops occurred as a result of major decreases in average fresh water runoff, to ~40% 31 of the modern value (pre-1964, before major fresh water diversions), reflecting severe droughts 32 during which annual precipitation in Jerusalem was lower than 350 mm/y, compared to ~600 33 mm/y today. Nevertheless, even during salt intervals, the changes in halite facies and the 34 occurrence of alternating periods of halite and detritus in the Dead Sea core stratigraphy reflect 35 fluctuations between drier and wetter conditions around our estimated average. The halite 36 intervals include periods that are richer and poorer in halite, indicating (based on the 37 sedimentation rate) that severe dry conditions with water availability as low as ~20% of present 38 day, continued for periods of decades to centuries, and fluctuated with wetter conditions that 39 spanned centuries to millennia when water availability was ~50-100% of present day. These 40 conclusions have potential implications for the coming decades, as climate models predict 41 greater aridity in the region. 42 3 Mediterranean, reflecting both natural variability and increased anthropogenic greenhouse gas 47 concentrations and predict up to 20% decreases in water availability by the end of the 21 st 48 century (
Microbial sulfate reduction (MSR) occurs commonly in reducing redox environment (Canfield & Berner, 1987; Morse & Cornwell, 1987; Wilkin & Barnes, 1997) where it can affect significantly the magnetic properties of sediments by causing titanomagnetite dissolution and by triggering authigenic greigite (Fe 3 S 4) precipitation (
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