Evaporite minerals of the lower 538.5 m sediments in a long core from the Western Qaidam Basin, Tibet
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Keywords:
Halite
Ankerite
Anhydrite
Carbonate minerals
ABSTRACT The Middle Devonian Telegraph Member of the Muskeg Formation contains well-preserved primary depositional fabrics and textures similar to those found in modern shallow-water ephemeral brine pans. The Telegraph halite is the lowermost of a series of halite units deposited in the Elk Point basin in northeastern Alberta. The Telegraph Member contains two halite units, a lower and an upper, separated by dolomite and anhydrite. The lower Telegraph halite is characterized by vertical sequences 1 to 5 cm thick, beginning with: 1) a muddy anhydritic parting with an erosional base overlain by 2) cumulate textured equant cubes and hopper rafts of halite, 3) a framework of competitively grown, vertically oriented syntaxial chevron and cornet halite. The vertical framework is cut by mud and halite filled pipes descending from anhydrite partings. Depositional sequences are interpreted to have formed in a shallow brine pan that underwent repeated flooding and desiccation. The upper Telegraph halite is cyclic, containing cycles that are 2-4 m in thickness and consist of: 1) laminated anhydrite-calcite, 2) chaotically bedded anhydrite-calcite containing pseudomorphous and displacive halite, and 3) repeated sequences of halite similar to that of the lower Telegraph. The upper Telegraph cycles indicate deposition from a shallow brine body initially at gypsum saturation. Brine concentration to halite saturation and desiccation led to the development of a shallow-water salt-pan environment. MILIEU DE DEPOT DES SELS DU MEMBRE TELEGRAPH, DEVONIEN MOYEN, ALBERTA, CANADA RESUME Le membre Telegraph (Devonien moyen) de la formation Muskeg renferme des structures et des textures de depot primaires semblables a celles qu'on trouve dans les cuvettes a sel ephemeres et peu profondes du temps present. La halite Telegraph est la plus ancienne d'une serie de couches de halite deposees dans le bassin Elk Point, dans le nord-est de l'Alberta. Le membre Telegraph renferme deux couches de halite, une inferieure et une superieure, separees par de la dolomie et de l'anhydrite. L'halite Telegraph inferieure est caracterisee par des sequences verticales de 1 a 5 cm d'epaisseur, en commencant par 1) un plan de stratification boueux et a anhydrite, a base formee par erosion, recouvert par 2) une accumulation de cubes de halites a dimensions egales et de tremies de halite transportees, et 3) une charpente de cristaux de halite syntaxiaux en chevron et en cornet, a croissance concurrentielle et orientes a la verticale. La charpente verticale est taillee par des cheminees remplies de boue et de halite, qui sont issues des plans de stratification a anhydrite surjacents. Ces sequences sont interpretees comme depots de cuvettes a sel peu profondes, qui subirent plusieurs inondations et desiccations. La halite Telegraph superieure est cyclique, renfermant des cycles de sedimentation de 2 a 4 m d'epaisseur qui se composent 1) d'anhydrite et de calcite laminaires, 2) de lits chaotiques d'anhydrite et de calcite, renfermant de l'halite pseudomorphe et deplacive, et 3) de sequences repetees de halite semblables a celles du membre Telegraph inferieur. Les cycles du membre Telegraph superieur indiquent un depot dans un bassin de saumure peu profond et initiallement sature en gypse. La concentration de la saumure jusqu'a saturation en halite et la desiccation donna lieu au developpement d'un milieu de cuvettes a sel peu profondes. Traduit par Marc Charest
Halite
Anhydrite
Devonian
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The Artesia Group of the Texas Panhandle is an evaporite red-bed sequence which has been intensely altered by interaction of evaporites with ground water. Comparison of the upper, most altered part of the sequence with the lower, least altered part allows identification of the diagenetic sequence. The least altered lower part of the Artesia Group includes anhydrite beds, anhydritic halite, mudstone-halite mixtures, mudstone, claystone, siltstone, and sandstone. Diagenetic processes include cementation by halite, replacement of gypsum by anhydrite and minor polyhalite, and minor replacement of halite by dolomite and anhydrite. Halite is present throughout the lower part of the Artesia Group as bedded halite, as isolated halite crystals and veins, and as halite cement in clastic beds. The altered interval in the upper part of the Artesia Group is characterized by mudstone-anhydrite-dolomite breccias, thin, wavy laminae of anhydrite and dolomite, and abundant fractures filled with fibrous anhydrite and gypsum in mudstone, claystone, siltstone, and thin anhydrite beds. Halite is absent, and removal of halite is interpreted as the principal cause of the alteration, either directly, by dissolution and collapse, or indirectly, by increasing porosity and allowing increased ground-water penetration. At the top of the Artesia Group, anhydrite has been hydrated more » to gypsum, and minor amounts of gypsum have been replaced by calcite. The geochemistry of preserved halite in the lower part of the Artesia Group shows that meteoric waters have been included in halite and that halite has been recycled by dissolution and reprecipitation. The occurrence of this type of alteration might indicate that the halite of the Artesia Group was invaded by waters from the overlying aquifers. However, the stratigraphic and textural relationships in the halite indicate that the alteration reflects continental influences in the clastic-dominated depositional environment. 32 refs., 45 figs., 1 tab. « less
Halite
Anhydrite
Sabkha
Siltstone
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Inclusions in anhydrite crystals from blue halite veins in the Kłodawa Salt Dome (Zechstein, Poland)
The occurrence of both the blue and violet halites is one of the most interesting phenomena in nature. Despite numerous laboratory and field works, their origin in natural evaporitic environments has not been satisfactorily explained. In the Kłodawa Salt Dome (Zechstein, Central Poland), blue or violet halites occur relatively frequently. Their accumulations differ in size and intensity of colours. In this paper, petrological features of anhydrite crystals derived from one of the largest outcrops of the blue halite at the Kłodawa Salt Mine are presented. Anhydrite is one of solid inclusions encountered in blue-coloured halite crystals. Special attention was paid to fluid inclusions present in this anhydrite. The microthermometric measurements showed two directions of homogenisation, i.e., towards the liquid phase (LG → L, LL → L) or towards the gas phase (LG → G). In the former case, the temperatures ranged from 174 to 513°C, whereas in the latter one, the values from 224 to 385°C were measured. The composition of inclusions is relatively variable. We can observe transparent and opaque daughter minerals as well as CO 2 in the liquid phase accompanied by a variable amount of methane or hydrogen sulphide. These features of inclusions indicate that anhydrite crystals and, thus, blue halite were formed under the influence of hydrothermal conditions. Observations in the mine workings combined with petrological studies enable to conclude that blue colouration of halite crystals is controlled by three factors: a high temperature, reducing conditions and defects in halite lattice related to tectonic stress. Normal 0 21 false false false PL X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Standardowy; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Arial","sans-serif"; mso-bidi-font-family:"CG Times 12pt"; mso-fareast-language:EN-US;}
Halite
Anhydrite
Salt pan
Dome (geology)
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Citations (7)
ABSTRACT Halite pseudomorphs after gypsum crystals preserve depositional textures and record the early diagenetic history of anhydrite beds in cyclic Permian evaporites of the Texas Panhandle. The well-documented sedimentologic setting and good preservation of fabrics permit identification of a sequence of diagenetic processes in gypsum. Gypsum (rather than anhydrite) was the dominant sulfate precipitated, even at salinities near halite saturation. Large gypsum crystals grew vertically on floors of brine pools, surrounded by a matrix of autochthonous transported gypsum sand and silt. All gypsum has been diagenetically altered to anhydrite ± halite, but the diagenetic fabrics vary depending on position within regressive evaporite cycles. Because the composition and texture of the primary sediment were similar throughout the anhydrite bed, these different diagenetic fabrics are interpreted as the result of changes in the processes of replacement of gypsum by anhydrite and halite as the shallow burial environment became increasingly saline. In the lower parts of anhydrite beds, diagenesis in low-salinity brines favored obliteration of primary sedimentary structures by formation of nodules. In the middle parts of beds, introduction of high-salinity brine into the shallow burial environment favored alteration of gypsum to anhydrite and preservation of pseudomorphs after large gypsum crystals. At the top of anhydrite beds, introduction of halite-saturated brines into gypsum sediments on the floor of the brine pool resulted in pervasive replacement of gypsum by halite. Petrogr phic relationships indicate that most or all of the primary gypsum was altered to anhydrite in the very shallow (< 2 m) burial environment under the influence of saline diagenetic brines.
Anhydrite
Halite
Pseudomorph
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The Oldest Halite (Na1) (Zechstein, Upper Permian) played a significant role in the development of geological structure of the Fore-Sudetic Monocline (SW Poland) because of its different rheological properties in comparison to the adjacent rocks. Intercalations of anhydrite and anhydrite-halite occurring within the Na1 show a lot of features of tectonically disturbed rocks. Macroscopic petrological observations revealed that anhydrite rocks represent four rock types with different structural and textural properties. On the microscopic scale, five types of crystals have been distinguished in all macroscopic types. They vary in size, shape and distribution of primary fluid inclusion assemblages. The anhydrite-halite rocks show two groups with slightly different petrological features that are apparently related to their tectonic deformation and recrystallisation processes. The main recorded directions of tectonic movements seem to be horizontal or sub-horizontal.
Halite
Anhydrite
Monocline
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Studies of boreholes penetrating the Dewey Lake, Rustler, and uppermost Salado Formations in the northern Delaware basin (southeastern New Mexico) have investigated subsurface of bedded evaporites in the vicinity of Nash Draw, a depression 5 to 10 mi (8 to 16 km) wide and about 250 ft (75 m) deep. The thickness of the section between the top of the Salado Formation and the base of marker bed 103 ranges from an intact 210 ft (64 m, east of Nash Draw) to a residual 45 ft (14 m in the Draw), where gypsification of Rustler anhydrite and removal of Rustler halite are virtually complete. The uppermost Permian halite has been previously described as a zone (the brine aquifer). Within 130 ft (40 m) below this zone are halite-filled fractures, cubic-shape cavities, and gypsum after anhydrite. Above are remnant islets of halite and anhydrite, gypsum replacing anhydrite and polyhalite, and breccia. The mineralogy and stratigraphy suggest that the shallow-seated dissolution front is a series of fingers moving laterally along bedding planes, rather than a single surface migrating downward. The sequence of alterations appears to be: (1) fracture of brittle rock, (2) of halite adjacent to the fracture rock, (3) gypsification of interbedded polyhalite and then anhydrite, and (4) of gypsum. Waters of higher salinity and lower flow rate in the brine aquifer east of Nash Draw show an oxygen isotope enrichment with respect to meteoric waters, indicating that the low fluid-to-rock ratio there has thus far recluded significant alteration of rock by water. End_of_Article - Last_Page 764------------
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The development of basal Zechstein (Wuchiapingian) strata inSW Polandindicates the existence of a diversified relief inherited after the flooding of the pre-existing depression by the transgressing Zechstein sea. The deeper parts of the basin were the place of development of thin basinal Zechstein Limestone showing sedimentary condensation manifested by bored and encrusted grains and thick evaporites (mostly halite), and in shallow parts Zechstein Limestone reefs followed by thinner evaporite sequences (dominated by anhydrite) occur. The analysis of 3D seismic sections showed that instead of three conventionally recognized evaporite units of stratigraphic potential in the PZ1 cycle, five units occur (from the base to the top: Lower Anhydrite, Lower Oldest Halite, Middle Anhydrite, Upper Oldest Halite, Upper Anhydrite). In a particular place their number may vary from two (Lower Anhydrite at the base of the PZ1 cycle and Upper Anhydrite at the top of the PZ1 cycle) to five. There are two complexes of Lower Anhydrite occurring throughout the platform and basinal zones showing deepening-upward (transgressive) trend. The halite sedimentation in the deepest parts of salt basins began shortly after the deposition of the upper Lower Anhydrite complex while in the sulphate platform areas the sulphate deposition lasted still for a long time. The Lower Oldest Halite deposits occur in the depressions. Between the halite basins, anhydrite platforms occur, and the thickness of anhydrite platform deposits is smaller than it is observed in salt basins. The Upper Oldest Halite in turn is recorded above the anhydrite platform. The two halite units represent different phases of development of halite basins. The Lower Oldest Halite basins are related to the pre-Zechstein depressions, although in some cases their syndepositional subsidence was controlled by reactivation, during the deposition of basal Zechstein strata, of former faults. In turn, the Upper Oldest Halite basins used the accommodation space created due to anhydritization of the Lower Anhydrite deposits composed originally of selenitic gypsum. The 3D seismics evidences that the PZ1 evaporites inSW Polandhave been deposited in far more complex and dynamic system than it was assumed before.
Anhydrite
Halite
Sabkha
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Aragonite, low‐magnesian calcite, gypsum and halite were identified by X‐ray diffraction and electron microbeam techniques in mineral precipitates near a salt seep 50 km southwest of Charters Towers in north Queensland. The chemistry of water from the creek and from the groundwater at the salt seep shows that Mg:Ca ratios are greater than or equal to 1.5 throughout the year. The formation of halite and gypsum is due to evaporative concentration of the water at the seep and that of the carbonates, in particular aragonite, is probably due to a combination of evaporation and photosynthetic activity by diatoms.
Halite
Petroleum seep
Saline water
Sabkha
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Bimineralic, polycrystalline rocksalt specimens ranging in composition from pure halite to pure anhydrite have been fabricated in hydrostatic compression at 150 MPa and 100°C for 15 minutes. Resulting porosities of the compacted samples increased with increasing anhydrite content, ranging from .02 for pure halite to .14 for pure anhydrite. Twenty‐three compacted samples were then deformed in triaxial compression experiments at confining pressures of 10, 100 and 200 MPa, a nominal strain rate of 10 −4 sec −1 and a temperature of 200°C. Sample strength at 10 percent axial strain was directly related to both anhydrite content and pressure. Relatively small strength increases were observed for increases in anhydrite content up to 75 percent, by weight, and for all pressure increases. Much larger increases in strength were observed when the anhydrite content was increased from 75 to 100 percent. Ductilities of less than 10 percent were seen in only two sets of data, the 100 and 75 percent anhydrite samples run at 10 MPa confining pressure, and these data indicated a trend of increasing ductility with increasing halite content and/or confining pressure. All samples exhibited strain hardening except for the 75 percent halite samples at all three pressures and the 50 percent sample at 10 MPa, which exhibited slight strain softening.
Anhydrite
Halite
Hydrostatic pressure
Overburden pressure
Strain hardening exponent
Ductility (Earth science)
Hydrostatic equilibrium
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Halite
Anhydrite
Brine
Salt lake
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