Triple oxygen isotope systematics of evaporation and mixing processes in a dynamic desert lake system

Abstract. This study investigates the combined hydrogen deuterium and triple oxygen isotope hydrology of the Salar del Huasco, an endorheic salt flat with shallow lakes at its centre that is located on the Altiplano Plateau, N Chile. This lacustrine system is hydrologically dynamic and complex because it receives inflow from multiple surface and groundwater sources. It undergoes seasonal flooding, followed by rapid shrinking of the water body at the prevailing arid climate with very high evaporation rates. At any given point in time, ponds, lakes, and recharge sources capture a large range of evaporation degrees. Samples taken between 2017 and 2019 show a range of δ18O between −13.3 ‰ and 14.5 ‰, d-excess between 7 ‰ and −100 ‰, and 17O-excess between 19 and −108 per meg. A pan evaporation experiment conducted on-site was used to derive the turbulence coefficient of the Craig–Gordon isotope evaporation model for the local wind regime. This, along with sampling of atmospheric vapour at the salar (-21.0±3.3 ‰ for δ18O, 34±6 ‰ for d-excess and 23±9 per meg for 17O-excess), enabled the accurate reproduction of measured ponds and lake isotope data by the Craig–Gordon model. In contrast to classic δ2H–δ18O studies, the 17O-excess data not only allow one to distinguish two different types of evaporation – evaporation with and without recharge – but also to identify mixing processes between evaporated lake water and fresh flood water. Multiple generations of infiltration events can also be inferred from the triple oxygen isotope composition of inflow water, indicating mixing of sources with different evaporation histories. These processes cannot be resolved using classic δ2H–δ18O data alone. Adding triple oxygen isotope measurements to isotope hydrology studies may therefore significantly improve the accuracy of a lake's hydrological balance – i.e. the evaporation-to-inflow ratio (E / I) – estimated by water isotope data and application of the Craig–Gordon isotope evaporation model.

Download Full-text

Supplementary material to "Triple oxygen isotope systematics of evaporation and mixing processes in a dynamic desert lake system"

10.5194/hess-2020-255-supplement ◽

2020 ◽

Author(s):

Claudia Voigt ◽

Daniel Herwartz ◽

Cristina Dorador ◽

Michael Staubwasser

Keyword(s):

Oxygen Isotope ◽

Mixing Processes ◽

Lake System ◽

Supplementary Material ◽

Isotope Systematics ◽

Desert Lake

Download Full-text

Oxygen isotope composition of zircons from the Talnakh economic intrusion of the Noril’sk province: first data

Доклады Академии наук ◽

10.31857/s0869-56524892170-173 ◽

2019 ◽

Vol 489 (2) ◽

pp. 170-173

Author(s):

I. Yu. Badanina ◽

E. A. Belousova ◽

K. N. Malitch ◽

S. F. Sluzhenikin

Keyword(s):

Oxygen Isotope ◽

Isotope Composition ◽

Oxygen Isotope Composition ◽

Primary Magma ◽

Crustal Component ◽

Layered Series ◽

Isotope Data ◽

Oxygen Isotope Data ◽

First Results ◽

Isotope Analyses

This study presents the first results of oxygen isotope analyses (18O) collected on zircons from the Talnakh economic intrusion within the Norilsk province. Zircons from gabbro-diorite, gabbroic rocks of the layered series and plagioclase-bearing wehrlite have similar mantle-like mean 18O values (5,39 0,49; 5,64 0,48 and of 5,28 0,34, respectively), which differ from 18O in zircons from sulfide-bearing melanocratic troctolite with a taxitic texture in the lower part of the intrusion (mean 18O = 6,50 0,98). These new oxygen isotope data support (i) the mantle-derived origin of the primary magma(s), parental to the Talnakh intrusion, and (ii) possible involvement of a crustal component during the formation of sulfide-bearing taxitic-textured rocks.

Download Full-text

Quantitative reconstruction of past climate mean states in the Atacama Desert using hydrogen and triple oxygen isotopes of gypsum hydration water

10.5194/egusphere-egu2020-18469 ◽

2020 ◽

Author(s):

Claudia Voigt ◽

Daniel Herwartz ◽

Michael Staubwasser

Keyword(s):

Wind Speed ◽

Isotopic Composition ◽

Oxygen Isotope ◽

Atacama Desert ◽

Variable Degree ◽

State Variables ◽

Isotopic Data ◽

Evaporation Model ◽

Isotope Data ◽

Mean State

Gypsum crystals capture the isotopic composition (&#948;2H, &#948;17O, and &#948;18O) of ambient water in their structurally bonded water and may serve as a useful tool to reconstruct paleoclimate. Relative humidity, water temperature, wind speed, along with the isotopic composition of atmospheric vapor and inflowing water control, to a variable degree, the relative proportion of equilibrium and kinetic isotope fractionation during evaporation, and, thus, ultimately determine the d-excess and 17O-excess of gypsum-bonded water. Here, we demonstrate that the respective best fit of these variables through measured gypsum-bonded water isotope data using the classic Craig-Gordon evaporation model provides apparent absolute values for the fundamental climate mean state variables humidity and temperature and an empirical wind speed parameter of the geologic past.In this proof-of-concept study, we sampled gypsum crystals within individual stratigraphic units of Pliocene lacustrine deposits from the Atacama Desert, extracted their structurally bonded water, and analyzed the hydrogen and triple oxygen isotope composition. The spread of measured isotope data within each sampled stratigraphic unit suggests variable degrees of evaporation between individual gypsum samples along a common evaporation trajectory. We used the Craig-Gordon evaporation model together with a Monte Carlo simulation to determine the limits of climate mean state variables that fit the measured isotopic data.Our results demonstrate that primary isotope signatures of marine and continental source waters are preserved in structurally bonded gypsum waters. The data coherently suggest a slightly warmer (18-35&#176;C), less windy and much more humid (50-75%) climate for the Pliocene Atacama, which is consistent with marine records and global circulation climate models that agree on &#8220;permanent El Ni&#241;o&#8221; conditions for the Pliocene in the equatorial East Pacific.Under the assumption that mixing of different brines or multiple sources is insignificant - as would be evident from scattering of isotopic data below the evaporation trajectory in 17O-excess over &#948;18O &#8211; the combined hydrogen and triple oxygen isotope analyses of gypsum-bonded water provides a powerful tool to quantify past mean states of humidity and temperature, and to estimate paleo-wind conditions.

Download Full-text

Triple oxygen isotope variations in magnetite from iron-oxide deposits, central Iran, record magmatic fluid interaction with evaporite and carbonate host rocks

Geology ◽

10.1130/g46981.1 ◽

2019 ◽

Vol 48 (3) ◽

pp. 211-215 ◽

Cited By ~ 3

Author(s):

Stefan T.M. Peters ◽

Narges Alibabaie ◽

Andreas Pack ◽

Seann J. McKibbin ◽

Davood Raeisi ◽

...

Keyword(s):

Iron Oxide ◽

Oxygen Isotope ◽

Carbonate Rocks ◽

Isotope Composition ◽

Central Iran ◽

Magmatic Fluid ◽

Isotope Data ◽

O Isotopes ◽

Magmatic Fluids ◽

O Isotope

Abstract Oxygen isotope ratios in magnetite can be used to study the origin of iron-oxide ore deposits. In previous studies, only 18O/16O ratios of magnetite were determined. Here, we report triple O isotope data (17O/16O and 18O/16O ratios) of magnetite from the iron-oxide–apatite (IOA) deposits of the Yazd and Sirjan areas in central Iran. In contrast to previous interpretations of magnetite from similar deposits, the triple O isotope data show that only a few of the magnetite samples potentially record isotopic equilibrium with magma or with pristine magmatic water (H2O). Instead, the data can be explained if magnetite had exchanged O isotopes with fluids that had a mass-independently fractionated O isotope composition (i.e., MIF-O), and with fluids that had exchanged O isotopes with marine sedimentary carbonate rocks. The MIF-O signature of the fluids was likely obtained by isotope exchange with evaporite rocks of early Cambrian age that are associated with the IOA deposits in central Iran. In order to explain the triple O isotope composition of the magnetite samples in conjunction with available iron isotope data for magnetite from the deposits, we propose that magnetite formed from magmatic fluids that had interacted with evaporite and carbonate rocks at high temperatures and at variable water/rock ratios; e.g., magmatic fluids that had been released into the country rocks of a magma reservoir. Additionally, the magnetite could have formed from magmatic fluids that had exchanged O isotopes with SO2 and CO2 that, in turn, had been derived by the magmatic assimilation and/or metamorphic breakdown of evaporite and carbonate rocks.

Download Full-text

The U-Pb Zircon Geochronology (LA-ICP-MS) of Geological Processes in Granulites of Middle Bouh Area. Article 3. Rock association in the lower reaches of the Yatran river

Mineralogical Journal ◽

10.15407/mineraljournal.43.01.034 ◽

2021 ◽

Vol 43 (1) ◽

pp. 34-50

Author(s):

L.M. STEPANYUK ◽

L.V. SHUMLYANSKYY ◽

S.I. KURYLO ◽

V.O. SYOMKA ◽

S.M. BONDARENKO ◽

...

Keyword(s):

Isotope Composition ◽

Hf Isotope ◽

Zircon Geochronology ◽

Pb Isotope ◽

Isotope Data ◽

Geological Processes ◽

Icp Ms ◽

Isotope Systematics ◽

Isotope Analyses ◽

Rock Association

LA-ICP-MS method was applied to investigate U-Pb and Lu-Hf isotope systematics of zircon crystals from charnockitic gneiss and biotite-garnet-hypersthene enderbite that occur in the lower reaches of the Yatran river (Yatran block of the Bouh river area). According to the obtained isotope data, charnockitic gneiss hosts three zircon populations. The oldest one is represented by three crystals that have isotope age between 3125 and 3300 Ma, and εHf values between –2.3 and –7.5. The next population is well-defined, it has an age of 2038±25 Ma and large variations of Hf isotope composition: 176Hf/177Hf — from 0.28122 to 0.28261, εHf — from –9.3 до 4.6. However, the ages of most of the analyzed zircons spread along the concordia between 2300 and 2800 Ma. All zircons in this population have a similar Hf isotope composition 176Hf/177Hf = 0.28072 to 0.28092, which does not depend on the age. It is characteristic that the oldest (with preserved U-Pb isotope systematics) crystals have positive or slightly negative εHf values. Most of the U-Pb isotope analyses of zircons from enderbite fall on the discordia line that has an upper interception age of 2029 ± 18 Ma. A small number of discordant grains have 207Pb/206Pb ages up to 2500 Ma. Hafnium isotope composition in zircons from enderbite varies widely: 176Hf/177Hf = 0.28131 to 0.28151, and εHf from –6.2 to 1.8.

Download Full-text