The record of temperature, wind velocity and air humidity in the δD and δ18O of water inclusions in synthetic and Messinian halites

Rigaudier, Thomas; Lécuyer, Christophe; Gardien, Véronique; Suc, Jean‐Pierre; Martineau, François

doi:10.1016/j.gca.2011.05.034

Cited by 27 publications

(36 citation statements)

References 73 publications

(81 reference statements)

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“…The calculated mean d 18 OH 2 O value for the Touissit-Bou Beker mineralizing fluid (3 ± 2‰; Bouabdellah et al, 2012) falls within the known range of oxygen isotope values for Messinian seawater (-2.2 to 12.9‰, mean 2.7‰; Rigaudier et al, 2014), and constitutes supporting evidence for the involvement of Messinian-derived brines during mineralization in the Touissit-Bou Beker district.…”

Section: Alternative Genetic Modelsupporting

confidence: 70%

The Touissit-Bou Beker Mississippi Valley-Type District of Northeastern Morocco: Relationships to the Messinian Salinity Crisis, Late Neogene-Quaternary Alkaline Magmatism, and Buoyancy-Driven Fluid Convection

Bouabdellah¹,

Niedermann²,

Velasco³

2015

Economic Geology

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The Touissit-Bou Beker Mississippi Valley-type (MVT) district of northeastern Morocco includes five major strata-bound Pb-Zn-Ag deposits that produced, over a century of mining, more than 70 Mt of ore at an average grade of 4.0 wt % Pb, 3.5 wt % Zn, ~1 wt % Cu, and 120 g/t Ag. Economic orebodies are hosted by a 25-m-thick sequence of unmetamorphosed, flat-lying, diagenetically and hydrothermally dolomitized carbonate platform rocks of Aalenian-Bajocian (174-168 Ma) age. The sulfide mineralization consists principally of galena and sphalerite, and occurs as open-space fillings and partial to massive replacements of medium-to coarse-grained dolostones.Throughout the district and surrounding prospects, sulfur isotope compositions of sulfide minerals range from -8.6 to 12.9‰ CDT (n = 194) and display spatial and temporal variations characterized by an overall progressive decrease of d 34 S values: (1) with advancing paragenetic sequence, and upward stratigraphic position; (2) toward distal prospects; and (3) within single grains from core to rim. Similarly, the distribution of 3 He/ 4 He ratios shows an overall lowering from 0.5 RA to <0.01 RA with advancing paragenetic stage. Conversely, lead isotope compositions of galena display fairly uniform 206 Pb/ 204 Pb (18.31-18.37), 207 Pb/ 204 Pb (15.61-15.66), and 208 Pb/ 204 Pb (38.45-38.62) ratios, which contrast significantly with the highly heterogeneous isotopic compositions ( 206 Pb/ 204 Pb = 17.76-18.49, 207 Pb/ 204 Pb = 15.61-15.70, 208 Pb/ 204 Pb = 37.76-39.55) shown by potential metal source rocks.The large variations in d 34 S values are explained in terms of inorganic and/or bacteriogenic reduction, at different rates, of seawater sulfate in seawater or pore fluids, in reservoirs both open and closed with respect to sulfate. The highly variable 3 He/ 4 He values reflect different degrees of mixing between mantle and crustal He components along the fluid flow path. Estimated contributions of the mantle-derived ( 4 He) component involved in the mineralizing fluids of the paragenetically early Zn-rich ore-stage I, and in the later Pb-rich main ore-stage II, are in the range of ~3 to 8%. With time, the mantle-derived input to the mineralizing fluids decreased, and contemporaneously the involvement of surface waters increased, consistent with the lowering of d 34 S with advancing paragenetic stage. This geochemical evolution toward lower isotopic values indicates that the Touissit-Bou Beker hydrothermal system became exclusively dominated by crustally derived fluids, and probably incorporated at shallower levels the influx of progressively larger volumes of cooler, dilute, and oxidized meteoric waters.Whole-rock and galena lead isotope compositions are consistent with a model in which metals were extracted from the local country rocks, particularly the basement Visean rhyodacites and associated siliciclastic rocks, and from the overlying Triassic to Upper Bajocian sediments. The extraction of lead likely occurred during the late Neogene, coincident with the Messin...

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Section: Alternative Genetic Modelsupporting

confidence: 70%

The Touissit-Bou Beker Mississippi Valley-Type District of Northeastern Morocco: Relationships to the Messinian Salinity Crisis, Late Neogene-Quaternary Alkaline Magmatism, and Buoyancy-Driven Fluid Convection

Bouabdellah¹,

Niedermann²,

Velasco³

2015

Economic Geology

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“…On average, the standard deviations from those Precambrian halite analyses are 5.4‰, and δ 2 H VSMOW values vary from −89.1‰ to −37.6‰. Laboratory experiments revealed that the amount of evaporation required to precipitate halite is accompanied by a D enrichment of 90‰ to 120‰ depending on ambient parameters such as air temperature, relative humidity, and wind velocity . It means that the original aqueous solutions had δD values lower than −150‰.…”

Section: Resultsmentioning

confidence: 93%

“…The average value for the synthetic Lyon salt samples is δ 2 H VSMOW = +15.8 ± 6.6‰ (Table ). According to Rigaudier et al, the 2 H/ 1 H isotopic values of water from the halite fluid inclusions reflect the range of isotopic values during the last stages of evaporation. 2 H/ 1 H isotopic ratios of evaporating waters sampled between the stage of halite nucleation and that of final stage of crystallization bracket the compositions of water inclusions as shown by Rigaudier et al This is also what we measured from our synthetic salt experiments, as shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

“…According to Rigaudier et al, the 2 H/ 1 H isotopic values of water from the halite fluid inclusions reflect the range of isotopic values during the last stages of evaporation. 2 H/ 1 H isotopic ratios of evaporating waters sampled between the stage of halite nucleation and that of final stage of crystallization bracket the compositions of water inclusions as shown by Rigaudier et al This is also what we measured from our synthetic salt experiments, as shown in Figure . As fluid inclusions are continuously trapped in the defects of the halite crystal lattice over the complete stage of growth, their formation is not an instantaneous process, and they record the isotopic composition of the residual waters across a time range during which the isotopic values of the water still evolve.…”

Section: Resultsmentioning

confidence: 99%

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Improved online hydrogen isotope analysis of halite aqueous inclusions

et al. 2019

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We demonstrate an improved method based on continuous‐flow elemental analyser pyrolysis isotopic ratio mass spectrometry (CF‐EA‐PY‐IRMS) to measure the 2H/1H ratios of water trapped in halite crystals. Two challenges to overcome are the low hydrogen concentration of samples (10‐50 μmol H2·g−1) and the high chloride concentration released when reacting halite in an elemental analyser. We describe an optimization procedure for determining the 2H/1H ratio of this trapped water with an acceptable accuracy. This technique involves the use of a high‐temperature Cr reactor to quantitatively convert H2O into H2. The initial step was performed on halite crystals precipitated from a water reservoir where 2H/1H ratios were monitored from its initial stage until the end of evaporation. The 2H/1H isotopic analyses were automated online in continuous‐flow mode. Precision of the method was determined for those “synthetic” samples with hydrogen concentrations ranging from 0.2 to 0.5 wt%. 2H/1H isotopic ratios of evaporating waters bracket the compositions of water inclusions. The formation of fluid inclusions is not instantaneous and records the isotopic signature of the residual waters across a time range during which the isotopic values of the water still evolve. This property explains why the δ2HVSMOW standard deviation of ±5‰ (2σ) observed for 10‐mg aliquots of halite exceeds the instrumental error (about ±1.5‰ 2σ) determined on the basis of IAEA‐CH7, NBS 30, and NBS 22 references along with calibrated waters with and without added halite crystals. We also applied this method to Mesoproterozoic (1.4 Ga) and Neoproterozoic (0.8 Ga) halite samples with relatively low hydrogen concentrations (300‐1500 ppm). The measured δ2HVSMOW values for Precambrian waters range from −89‰ to −54‰. We propose that this technique offers a new perspective and great potential for palaeoenvironmental reconstructions based on the 2H/1H analyses of water trapped in halite.

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“…For example, according to Rigaudier et al . [], homogenization temperatures of fluid inclusions obtained by microthermometry in halite crystals from the Realmonte salt mine revealed precipitation temperatures of at least 35°C. This temperature is well above the present‐day annual SST of the Mediterranean Sea around Tuscany and Sicily, which averages 18–20°C, with oscillations between 14–15°C and 23–25°C in winter and summer [ World Ocean Atlas , ].…”

Section: Introductionmentioning

confidence: 99%

Paleoclimate reconstruction during the Messinian evaporative drawdown of the Mediterranean Basin: Insights from microthermometry on halite fluid inclusions

Speranza

Cosentino

Tecce

et al. 2013

Geochem Geophys Geosyst

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[1] Data constraining the paleoenvironmental conditions during the Messinian evaporative drawdown of the Mediterranean basin are still conflicting. Here we present a comprehensive paleoclimatic reconstruction during Messinian halite deposition from several Italian sites. We performed fluid inclusion analyses to define better both the composition of the Mediterranean water body and the paleotemperatures of the Messinian brine during halite crystallization. We measured homogenization temperatures on 218 primary all-liquid fluid inclusions in Messinian halite from the Volterra, Crotone, and Caltanissetta evaporite basins. These measurements provided mean homogenization temperatures of 17-18 C, with a range between 10-11 C and 28-29 C, which should be close to the SST of the Mediterranean Sea during halite deposition. The occurrence of major elements such as Cl, Na, Mg, S, Ca, and K within the halite fluid inclusions, together with the presence of minerals such as pentahydrite, polyhalite, and Ca-, K-, and Mg-sulfates, indicates that these salt bodies originated from mainly marine water. Taking into account both the present-day annual SST of the Mediterranean Sea around the sampling sites, which ranges between 18 and 20 C, and the lower latitude of the Mediterranean Basin during the Messinian Salinity Crisis, our homogenization temperatures point to a colder climate during the Messinian halite deposition compared to the present interglacial climate stage. This conclusion is consistent with halite deposition during a Late Miocene glacial interval (TG12).

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The record of temperature, wind velocity and air humidity in the δD and δ18O of water inclusions in synthetic and Messinian halites

Cited by 27 publications

References 73 publications

The Touissit-Bou Beker Mississippi Valley-Type District of Northeastern Morocco: Relationships to the Messinian Salinity Crisis, Late Neogene-Quaternary Alkaline Magmatism, and Buoyancy-Driven Fluid Convection

The Touissit-Bou Beker Mississippi Valley-Type District of Northeastern Morocco: Relationships to the Messinian Salinity Crisis, Late Neogene-Quaternary Alkaline Magmatism, and Buoyancy-Driven Fluid Convection

Improved online hydrogen isotope analysis of halite aqueous inclusions

Paleoclimate reconstruction during the Messinian evaporative drawdown of the Mediterranean Basin: Insights from microthermometry on halite fluid inclusions

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