Fluid Inclusions In Marine Halite Research Articles

Seafloor hydrothermal systems control long-term changes in seawater [Li+]: Evidence from fluid inclusions.

Secular variations in the major ion chemistry and isotopic composition of seawater on multimillion-year time scales are well documented, but the causes of these changes are debated. Fluid inclusions in marine halite indicate that the Li concentration in seawater [Li+]SW declined sevenfold over the past 150 million years (Ma) from ~184 μmol/kg H2O at 150 Ma ago to 27 μmol/kg H2O today. Modeling of the lithium geochemical cycle shows that the decrease in [Li+]SW was controlled chiefly by long-term decreases in ocean crust production rates and mid-ocean ridge and ridge flank hydrothermal fluxes without requiring changes in continental weathering fluxes. The decrease in [Li+]SW parallels the 150 Ma increase in seawater Mg2+/Ca2+ and 87Sr/86Sr, and the change from calcite to aragonite seas, KCl to MgSO4 evaporites, and greenhouse to icehouse climates, all of which point to the importance of plate tectonic activity in regulating the composition of Earth's hydrosphere and atmosphere.

Plate tectonic control of strontium concentration in Phanerozoic and Neoproterozoic seawater: Evidence from fluid inclusions in marine halite

Chemical analyses of 1371 fluid inclusions in 131 halite samples with marine 87Sr/86Sr values were used to reconstruct the strontium concentrations [Sr]SW of Phanerozoic and Neoproterozoic seawater. [Sr]SW varied seven-fold and oscillated twice between high- and low-Sr concentrations over the past 550 million years (Myr), in rhythm with Ca-rich and SO4-poor paleoseawater intervals and calcite-aragonite seas. Variations in the [Sr]/[Ca]SW ratio from fluid inclusions were not significant over the past ∼270 Myr, and are within ±3 µmol/mmol of the modern [Sr]/[Ca]SW ratio of ∼8.5 µmol/mmol. These results agree with the [Sr]/[Ca]SW ratios obtained from fossil corals, benthic foraminifera, brachiopods, belemnites, and rudists. [Sr]/[Ca]SW in the early and middle Paleozoic was ∼2 times the modern [Sr]/[Ca]SW ratio. A major shift of the [Sr]/[Ca]SW ratio in the late Permian coincided with the initial rifting of the Pangean supercontinent. Seawater 87Sr/86Sr ratios plotted against 1/[Sr]SW show two distinct linear correlations: negative correlation from 515 to 252 Ma and positive correlation from 150 to 0 Ma, suggesting different controls on the global Sr cycle between these intervals. The negative correlation coincides with the long-term assembly of Pangea in the Paleozoic (∼500–250 Ma). The positive correlation from 150 to 0 Ma parallels the break-up of Pangea and the decrease of mid-ocean ridge (MOR) hydrothermal fluid flux and subduction zone length in the Mesozoic and Cenozoic.

Ca2+] and [SO[formula omitted]] in Phanerozoic and terminal Proterozoic seawater from fluid inclusions in halite: The significance of Ca-SO4 crossover points

Chemical analyses of 2,618 (1,640 new and 978 published) fluid inclusions in marine halite were used to define paleoseawater [Ca2+] and [SO2−4] over the past 550 million years (Myr). Three types of fluid inclusion brine chemistries were recognized based on measured [Ca2+] and [SO2−4]: (1) SO4-rich with [SO2−4] ≫ [Ca2+]; (2) Ca-rich with [Ca2+] ≫ [SO2−4]; and (3) Ca-SO4 crossover points with [Ca2+] ≈ [SO2−4]. The SO4-rich and Ca-rich fluid inclusion chemistries oscillated twice in the terminal Proterozoic and Phanerozoic. Transitions between SO4-rich and Ca-rich seas, here called “Ca2+−SO42−crossover points” occurred four times: terminal Proterozoic–Early Cambrian (544–515 Ma), Late Pennsylvanian (309–305 Ma), Triassic–Jurassic boundary (∼200 Ma), and Eocene–Oligocene (36–34 Ma). New fluid inclusion analyses using laser ablation-inductively coupled plasma-mass spectrometry better defined the [Ca2+] and [SO2−4] in seawater at the Late Pennsylvanian and Eocene–Oligocene crossover points and the timing of the Triassic–Jurassic crossover point. Crossover points coincide with shifts in seawater Mg2+/Ca2+ ratios, the mineralogies of marine non-skeletal carbonates and shell building organisms (aragonite vs. calcite) and potash evaporites (MgSO4 vs. KCl types). Phanerozoic and terminal Proterozoic trends in seawater [Ca2+] and [SO2−4] also coincide with supercontinent breakup, dispersal, and assembly cycles, greenhouse–icehouse climates, and modeled atmospheric pCO2. Paleoseawater [Ca2+] and [SO2−4] were calculated from the fluid inclusion data using the assumption that the [Ca2+] × [SO2−4] ranged from 150 to 450 mmolal2, which is 0.5–1.5 times the [Ca2+] = 11 × [SO2−4] = 29 product in modern seawater (319 mmolal2). Two additional end-member scenarios, independent of the [Ca2+] × [SO2−4] = 150–450 mmolal2 assumption, were tested using constraints from fluid inclusion [Ca] and [SO4]: (1) constant [SO2−4] = 29 mmolal as in modern seawater, and variable [Ca2+], and (2) constant [Ca2+] = 11 mmolal as in modern seawater and variable [SO2−4]. Mg2+/Ca2+ ratios calculated from the three scenarios were compared to independent data on the Mg2+/Ca2+ ratios from skeletal carbonates (echinoderms and corals) and mid-ocean ridge flank calcite veins. Constant [Ca2+] of 11 mmolal is unlikely because this relatively low concentration generated unreasonably low seawater [SO2−4] during most of the past 550 Myr and high Mg2+/Ca2+ ratios compared to independent data. Constant [SO2−4] of 29 mmolal produced unreasonably high seawater [Ca2+] and lower Mg2+/Ca2+ ratios than those derived from fluid inclusions, echinoderms, corals, and calcite veins. Variable [Ca2+] and [SO2−4] showed the best agreement with the Mg2+/Ca2+ ratios derived from fluid inclusions, echinoderms, corals, and calcite veins.

ОСОБЛИВОСТІ ХІМІЧНОГО СКЛАДУ ОКЕАНІЧНОЇ ВОДИ РАННЬОГО ПАЛЕОЗОЮ (за даними досліджень рідких включень у галіті ордовицького солеродного басейну Ордос, Китай)

The fluid inclusions in the marine Middle Ordovician halite of the Majiagou Salt Formation of the Ordos Basin (China) have been investigated. In addition to the primary inclusions the secondary ones of several generations were also detected. The fluid inclusions brine chemistry of halite was studied using an ultramicrochemical (UMCA) method, and the homogenization temperature of fluid inclusions was determined in a special thermal chamber designed by V. A. Kalyuzhny At the post-sedimentation stage, the studied salt strata were exposed to high temperature (58–72 °C) and high (up to several tens of MPa) pressure. Although there are opinions of the inability of primary inclusions in such halite to determine the physical and chemical conditions of sedimentation, however, the informative value of primary inclusions in halite of the Majiagou Formation has remained. The preservation of the integrity (and thus the informative value) of primary inclusions in halite is evidenced by the same chemistry of their brines, which differs from that of secondary inclusions The sedimentation brines of the basin were concentrated to the middle of halite stage and points to the Na-K-Mg-Ca-Cl seawater. The physical and chemical conditions of evaporites formation are not known enough. Currently, the results of the brine chemistry of primary fluid inclusions in marine halite are the best indicators of seawater composition in the Phanerozoic. It is established that the magnesium content in the brines of the Lower Paleozoic basins is lower comparing to modern seawater of the corresponding concentration, and the potassium ion concentration is higher. The chemical composition of the concentrated seawater from which the halite was crystallized in the Ordovician salt basin of Ordos, with the exception of the calcium ion content, is similar to the seawater chemistry of the Cambrian and Silurian basins, which indicates the relative constancy of Early Paleozoic seawater chemistry. Age-related changes in the chemical composition of seawater are always consistent with many quantitatively or qualitatively characterized processes of the Earth’s crust evolution. So we believe that the causes that led to more than twice the potassium content of Riphean-Devonian clays, unlike the younger ones, it were also the reason for the increase in potassium content in the Lower Paleozoic marine brines. The studies conducted also clarify the limits of oscillation of calcium ion content, which determines the type of seawater. Its content in the sedimentary brines of the Ordos basin of the Middle Ordovician reaches 66 g/l at the middle of halite stage. Therefore, at the beginning of the stage of halite precipitation, its content should be approximately 20 g/l (considering its theoretical content of 10 g/l with the modern composition of the atmosphere). Apparently, the cause of the abnormally high calcium content in the early Paleozoic Ocean was the direct flow of it with hydrothermal solutions into the ocean during the activation of global tectonics of the Earth and the increase of solubility of carbonates of continents and ocean floor due to high carbon dioxide atmospheric content.

The major-ion composition of Carboniferous seawater

The major-ion chemistry (Na+, Mg2+, Ca2+, K+, SO42−, and Cl−) of Carboniferous seawater was determined from chemical analyses of fluid inclusions in marine halites, using the cryo scanning electron microscopy (Cryo-SEM) X-ray energy-dispersive spectrometry (EDS) technique. Fluid inclusions in halite from the Mississippian Windsor and Mabou Groups, Shubenacadie Basin, Nova Scotia, Canada (Asbian and Pendleian Substages, 335.5–330Ma), and from the Pennsylvanian Paradox Formation, Utah, USA, (Desmoinesian Stage 309–305Ma) contain Na+–Mg2+–K+–Ca2+–Cl− brines, with no measurable SO42−, which shows that the Carboniferous ocean was a “CaCl2 sea”, relatively enriched in Ca2+ and low in SO42− with equivalents Ca2+ >SO42−+HCO3−.δ34S values from anhydrite in the Mississippian Shubenacadie Basin (13.2–14.0 ‰) and the Pennsylvanian Paradox Formation (11.2–12.6 ‰) support seawater sources. Br in halite from the Shubenacadie Basin (53–111ppm) and the Paradox Basin (68–147ppm) also indicate seawater parentages.Carboniferous seawater, modeled from fluid inclusions, contained ∼22mmol Ca2+/kg H2O (Mississippian) and ∼24mmol Ca2+/kg H2O (Pennsylvanian). Estimated sulfate concentrations are ∼14mmol SO42−/kg H2O (Mississippian), and ∼12mmol SO42−/kg H2O (Pennsylvanian). Calculated Mg2+/Ca2+ ratios are 2.5 (Mississippian) and 2.3 (Pennsylvanian), with an estimated range of 2.0–3.2.The fluid inclusion record of seawater chemistry shows a long period of CaCl2 seas in the Paleozoic, from the Early Cambrian through the Carboniferous, when seawater was enriched in Ca2+ and relatively depleted in SO42−. During this ∼200Myr interval, Ca2+ decreased and SO42− increased, but did not cross the Ca2+–SO42− chemical divide to become a MgSO4 sea (when SO42− in seawater became greater than Ca2+) until the latest Pennsylvanian or earliest Permian (∼309–295Ma). Seawater remained a MgSO4 sea during the Permian and Triassic, for ∼100Myr.Fluid inclusions also record a long interval, from the Early Cambrian to the Middle Devonian, when seawater had low Mg2+/Ca2+ ratios (<2) that coincide with calcite seas. The Mg2+/Ca2+ ratio of seawater rose from 0.9 in the Middle Devonian, to 2.5 in the Middle/Late Mississippian, 2.3 in the Middle Pennsylvanian, and 3.5 in the Early Permian. The transition from calcite seas to aragonite seas, established from the mineralogy of oölites and early marine cements, occurred in the Late Mississippian. Fluid inclusions show that seawater Mg2+/Ca2+ ratios rose above 2 by the Middle to Late Mississippian coinciding exactly with the shift to aragonite seas. Aragonite seas existed for ∼100Myr, from the Late Mississippian until the Late Triassic/Early Jurassic.

The major-ion composition of Cenozoic seawater: The past 36 million years from fluid inclusions in marine halite

Fluid inclusions from ten Cenozoic (Eocene-Miocene) marine halites are used to quantify the major-ion composition (Mg^2+^, Ca^2+^, K^+^, Na^+^, SO~4~^2−^, and Cl^−^) of seawater over the past 36 My. Criteria used to determine a seawater origin of the halites include: (1) stratigraphic, sedimentologic, and paleontologic observations; (2) Br^−^ in halite; (3) δ^34^S of sulfate minerals; (4) ^87^Sr/^86^Sr of carbonates and sulfates; and (5) fluid inclusion brine compositions and evaporation paths, which must overlap from geographically separated basins of the same age to confirm a "global" seawater chemical signal. Changes in the major-ion chemistry of Cenozoic seawater record the end of a systematic, long term (\>150 My) shift from the Ca^2+^-rich, Mg^2+^- and SO~4~^2−^-poor seawater of the Mesozoic ("CaCl~2~ seas") to the "MgSO~4~ seas" (with higher Mg^2+^ and SO~4~^2−^\>Ca^2+^) of the Cenozoic. The major ion composition of Cenozoic seawater is calculated for the Eocene-Oligocene (36-34 Ma), Serravallian-Tortonian (13.5-11.8 Ma) and the Messinian (6-5 Ma), assuming chlorinity (565 mmolal), salinity, and the K^+^ concentration (11 mmolal) are constant and the same as in modern seawater. Fluid inclusions from Cenozoic marine halites show that the concentrations of Mg^2+^and SO~4~^2−^ have increased in seawater over the past 36 My and the concentration of Ca^2+^ has decreased. Mg^2+^ concentrations increased from 36 mmolal in Eocene-Oligocene seawater (36-34 Ma) to 55 mmolal in modern seawater. The Mg^2+^/Ca^2+^ ratio of seawater has risen from ∼2.3 at the end of the Eocene, to 3.4 and 4.0, respectively, at 13.5 to 11.8 Ma and 6 to 5 Ma, and to 5 in modern seawater. Eocene-Oligocene seawater (36-34 Ma) has estimated ranges of SO~4~^2−^ = 14--23 mmolal and Ca^2+^ = 11--20 mmolal. If the (Ca^2+^)(SO~4~^2−^) product is assumed to be the same as in modern seawater (∼300 mmolal^2^), Eocene-Oligocene seawater had Ca^2+^ ∼16 mmolal and SO~4~^2−^ ∼19 mmolal. The same estimates of Ca^2+^ and SO~4~^2−^ for Serravallian-Tortonian seawater (13.5-11.8 Ma) are SO~4~^2−^ = 19--27 mmolal and Ca^2+^ = 8--16 mmolal and SO~4~^2−^ ∼24 mmolal and Ca^2+^ ∼ 13 mmolal if the (Ca^2+^)(SO~4~^2−^) product is equal to that in modern seawater. Messinian seawater has an estimated range of SO~4~^2−^ ∼21--29 mmolal and Ca^2+^ ∼7--15 mmolal with SO~4~^2−^ ∼26 mmolal and Ca^2+^ ∼12 mmolal assuming the (Ca^2+^)(SO~4~^2−^) product is equal to that in modern seawater. Regardless of the estimation procedure, SO~4~^2−^ shows progressively increasing concentrations from 36 Ma to the present values, which are the highest of the Cenozoic.

Secular variation in the major-ion chemistry of seawater: Evidence from fluid inclusions in Cretaceous halites

The major-ion (Mg 2+, Ca 2+, Na +, K +, SO 4 2 - , and Cl −) chemistry of Cretaceous seawater was determined from analyses of seawater-derived brines preserved as fluid inclusions in marine halites. Fluid inclusions in primary halite from three evaporite deposits were analyzed by the environmental scanning electron microscopy (ESEM) X-ray energy dispersive spectrometry (EDS) technique: the Early Cretaceous (Aptian, 121.0–112.2 Ma) of the Sergipe basin, Brazil and the Congo basin, Republic of the Congo, and the Early to Late Cretaceous (Albian to Cenomanian, 112.2–93.5 Ma) of the Khorat Plateau, Laos, and Thailand. The fluid inclusions in halite indicate that Cretaceous seawater was enriched several fold in Ca 2+, depleted in SO 4 2 - , Na +, and Mg 2+, and had lower Na +/Cl −, Mg 2+/Ca 2+, and Mg 2+/K + ratios compared to modern seawater. Elevated Ca 2+ concentrations, with Ca 2+ > SO 4 2 - at the point of gypsum saturation, allowed Cretaceous seawater to evolve into Mg 2+–Ca 2+–Na +–K +–Cl − brines lacking measurable SO 4 2 - .The major-ion composition of Cretaceous seawater was modeled from fluid inclusion chemistries for the Aptian and the Albian-Cenomanian. Aptian seawater was extreme in its Ca 2+ enrichment, more than three times higher than present day seawater, with a Mg 2+/Ca 2+ ratio of 1.1–1.3. Younger, Albian-Cenomanian seawater had lower Ca 2+ concentrations, and a higher Mg 2+/Ca 2+ ratio of 1.2–1.7. Cretaceous (Aptian) seawater has the lowest Mg 2+/Ca 2+ ratios so far documented in Phanerozoic seawater from fluid inclusions in halite, and within the range chemically favorable for precipitation of low-Mg calcite ooids and cements. Results from halite fluid inclusions, together with Mg 2+/Ca 2+ ratios measured from echinoderm and rudist calcite, all indicate that Early Cretaceous seawater (Hauterivian, Barremian, Aptian, and Albian) had lower Mg 2+/Ca 2+ ratios than Late Cretaceous seawater (Coniacian, Santonian, and Campanian). Low Aptian-Albian Mg 2+/Ca 2+ seawater ratios coincide with negative excursions of 87Sr/ 86Sr ratios and δ 34S SO 4 , and peak Cretaceous ocean crust production rates, all of which suggests a link between seawater chemistry and midocean ridge hydrothermal brine flux.

The major-ion composition of Permian seawater

The major-ion (Mg 2+, Ca 2+, Na +, K +, SO 4 2−, and Cl −) composition of Permian seawater was determined from chemical analyses of fluid inclusions in marine halites. New data from the Upper Permian San Andres Formation of Texas (274–272 Ma) and Salado Formation of New Mexico (251 Ma), analyzed by the environmental scanning electron microscopy (ESEM) X-ray energy-dispersive spectrometry (EDS) method, along with published chemical compositions of fluid inclusions in Permian marine halites from North America (two formations of different ages) and the Central and Eastern European basins (eight formations of four different ages) show that Permian seawater shares chemical characteristics with modern seawater, including SO 4 2− > Ca 2+ at the point of gypsum precipitation, evolution into Mg 2+-Na +-K +-SO 4 2−-Cl − brines, and Mg 2+/K + ratios ∼5. Permian seawater, however, is slightly depleted in SO 4 2− and enriched in Ca 2+, although modeling results do not rule out Ca 2+ concentrations close to those in present-day seawater. Na + and Mg 2+ in Permian seawater are close to (slightly below) their concentrations in modern seawater. Permian and modern seawater are both classified as aragonite seas, with Mg 2+/Ca 2+ ratios >2, conditions favorable for precipitation of aragonite and magnesian calcite as ooids and cements. The chemistry of Permian seawater was modeled using the chemical composition of brine inclusions for three periods: Lower Permian Asselian-Sakmarian (296–283 Ma), Lower Permian Artinskian-Kungurian (283–274 Ma), and Upper Permian Tatarian (258–251 Ma). Parallel changes in the chemistry of brine inclusions from equivalent age evaporites in North America, Central Europe, and Eastern Europe show that seawater underwent secular variations in chemistry over the 50 million years of the Permian. Modeled SO 4 2− concentrations are 20 mmol per kg H 2O (mmolal) and 19 mmolal in the Asselian-Sakmarian and Artinskian-Kungurian, with higher concentrations in the Upper Permian Tatarian (23 mmolal). Modeled Ca 2+ is at or above its concentration in modern seawater throughout the Permian. Mg 2+ is close to (slightly below) its concentration in modern seawater (55 mmolal) in the Asselian-Sakmarian (52 mmolal), and Tatarian (52 mmolal), but slightly higher than modern seawater in the Artinskian-Kungurian (60 mmolal). Mg 2+/Ca 2+ ratios are 3.5 (total range = 2.7 to 5.5) in the Lower Permian and rose slightly to 3.7 (total range = 3.1 to 5.8) in the Upper Permian, primarily due to decreases in Ca 2+. These results are consistent with models that predict oscillations in the major-ion composition of Phanerozoic seawater on the basis of changes in the midocean ridge/river water flux ratio driven by changes in the rate of midocean ridge crust production. The Permian was characterized by low sea levels, icehouse conditions, and southern hemisphere glaciation. Such conditions, analogous to the present ice age, and the similarities between Permian seawater and modern seawater, all suggest that general Phanerozoic supercycles, driven by mantle convection and global volcanicity, also control the major-ion chemistry of seawater.

Model of seawater composition for the Phanerozoic

We present an inverse model of Phanerozoic seawater com- position calibrated against updated paleoseawater compositions from fluid inclusions in marine halites. The model considers step- wise alteration of seawater composition via: (1) variable input of river water, (2) variable rates of alteration of seawater through reactions at mid-ocean ridges, and (3) variable rates of alteration of seawater through reactions on ridge flanks and across the ocean floor in general. The model achieves agreement with paleoseawater fluid inclusion data for Na 1 ,C a 2 1 ,S O 4 2 2 , and K 1 , particularly when variable runoff is considered. Variable rates of basalt- seawater interactions at both ridges and ridge flanks are required to understand the evolution of seawater, particularly the observed, near-constant concentration of K 1 through time.

Chemical evolution of seawater during the Phanerozoic: Implications from the record of marine evaporites

The chemical evolution of seawater during the Phanerozoic is still a matter of debate. We have assembled and critically analyzed the available data for the composition of fluid inclusions in marine halite and for the mineralogy of marine evaporites. The composition of fluid inclusions in primary marine halite reveals two major long-term cycles in the chemistry of seawater during the past 600 myr. The concentration of Mg2+, Ca2+, and SO42− has varied quite dramatically. The Mg2+ concentration in seawater during most of the early Paleozoic and Jurassic to Cretaceous was as low as 30 to 40 mmol/kg H2O; it reached maximum values ≥50 mmol/kg H2O during the Late Neoproterozoic and Permian. The Ca2+ concentration in seawater during the Phanerozoic has reached maximum values two to three times greater than the concentration in seawater today (10.6 mmol/kg H2O), whereas SO42− concentrations may have been as low as 5 to 10 mmol/kg H2O (a third to a fifth of the modern value) during the Jurassic and Early Paleozoic. The Mg2+/Ca2+ ratio in seawater ranged from 1 to 1.5 during the early to middle Paleozoic and Jurassic-Cretaceous to a near-modern value of 5.2 during the Late Neoproterozoic and Permian. This change in seawater Mg2+/Ca2+ ratio is consistent with the notion of alternating “calcite-aragonite seas” recorded in oölites and marine carbonate cements.Several models have been proposed to explain the chemical evolution of seawater. These have invoked significant changes in one or more of the major geochemical processes that control the composition of seawater. The pattern and magnitude of the variations in the composition of seawater proposed in this study are similar to those proposed elsewhere that suggest that seawater fluxes through midocean ridges have played a major role in the evolution of seawater during the past 600 myr. Two Phanerozoic supercycles of the Earth’s exogenic processes were recognized in the literature that are caused by mantle convection and plate activity. The composition of seawater has apparently undergone dramatic secular changes in phase with these supercycles and as a consequence of biological evolution. Analyses of fluid inclusions containing unevaporated seawater and a better understanding of the processes that affect the composition of seawater are needed to refine our understanding of the history of Phanerozoic seawater.

Oscillations in Phanerozoic Seawater Chemistry: Evidence from Fluid Inclusions

Systematic changes in the chemistry of evaporated seawater contained in primary fluid inclusions in marine halites indicate that seawater chemistry has fluctuated during the Phanerozoic. The fluctuations are in phase with oscillations in seafloor spreading rates, volcanism, global sea level, and the primary mineralogies of marine limestones and evaporites. The data suggest that seawater had high Mg2+/Ca2+ ratios (>2.5) and relatively high Na+ concentrations during the Late Precambrian [544 to 543 million years ago (Ma)], Permian (258 to 251 Ma), and Tertiary through the present (40 to 0 Ma), when aragonite and MgSO4 salts were the dominant marine precipitates. Conversely, seawater had low Mg2+/Ca2+ ratios (<2.3) and relatively low Na+ concentrations during the Cambrian (540 to 520 Ma), Silurian (440 to 418 Ma), and Cretaceous (124 to 94 Ma), when calcite was the dominant nonskeletal carbonate and K-, Mg-, and Ca-bearing chloride salts, were the only potash evaporites.

Tertiary seawater chemistry; implications from primary fluid inclusions in marine halite

Tertiary seawater chemistry; implications from primary fluid inclusions in marine halite