La halite du bassin potassique sud-pyreneen (Eocene superieur, Espagne)

Cabo, Federico Ortí; Mur, Juan José Pueyo; Ortiz, Laura Rosell

doi:10.2113/gssgfbull.i.6.863

Cited by 11 publications

(3 citation statements)

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“…The core plugs were extracted from two anhydrite-dominated surface outcrop field samples (ID prefix 'Ò') of the Òdena Gypsum Formation. This is the marginal equivalent of the salt deposits of the Cardona Saline Formation (upper Eocene) in the South Pyrenean foreland basin, Spain (Ortí Cabo et al, 1985).…”

Section: Sample Description and Preparationmentioning

confidence: 94%

Rapid hydration and weakening of anhydrite under stress: Implications for natural hydration in the Earth’s crust and mantle

Heeb

Healy

Timms

et al. 2023

Preprint

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Abstract. Mineral hydration is an important geological process that influences the rheology and geochemistry of rocks, and the fluid budget of the Earth’s crust and mantle. Steady-state differential compaction (SSDC), dry and ‘wet’ tests under confining pressure, and axial stress were conducted, for the first time, to investigate the influence of triaxial stress on hydration in anhydrite-gypsum aggregates. Characterization of the samples before and after triaxial experiments were performed with optical and scanning electron microscopy, including energy dispersive spectroscopy and electron backscatter diffraction mapping. Stress-strain data reveal that samples that underwent steady state differential compaction in the presence of fluids are ~14 to ~41 % weaker than samples deformed under ‘wet’ conditions. The microstructural analysis shows that there is a strong temporal and spatial connection between the geometry, distribution, and evolution of fractures and hydration products. The increasing reaction surface area in combination with pre-existing gypsum in a gypsum-bearing anhydrite rock led to rapid gypsification. The crystallographic orientations of newly formed vein-gypsum have a systematic preferred orientation for long distances along veins, beyond the grain boundaries of wall-rock anhydrite. Gypsum crystallographic orientations in {100} and {010} are systematically and preferentially aligned parallel to the direction of maximum shear stress (45° to σ1). Gypsum is also not always topotactically linked to the wall-rock anhydrite in the immediate vicinity. This study proposes that the selective inheritance of crystal orientations from favourably oriented wall-rock anhydrite grains for the minimization of free energy for nucleation under stress leads to the systematic preferred orientation of large new gypsum grains. A sequence is suggested for hydration under stress that requires the development of fractures accompanied by localised hydration. Hydration along fractures with a range of apertures up to 120 µm occurred in under 6 hours. Once formed, gypsum-filled veins represent weak surfaces and are the locations of further shear fracturing, brecciation, and eventual brittle failure. These findings imply that non-hydrostatic stress has a significant influence on hydration rates and subsequent mechanical strength of rocks. This phenomenon is applicable across a wide range of geological environments in Earth’s crust and upper mantle. Please find a graphical abstract in the PDF manuscript document and as PNG with the supplements.

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Section: Sample Description and Preparationmentioning

confidence: 94%

Rapid hydration and weakening of anhydrite under stress: Implications for natural hydration in the Earth’s crust and mantle

Heeb

Healy

Timms

et al. 2023

Preprint

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show abstract

“…The mineral has very large crystal sizes, inverted twinned crystals, and fanning cluster of upward-growing crystals, all of which are very similar to those of selenite (a variety of gypsum) (Fig. S4) generally formed by subaqueous free-growth precipitation 32,33 in water with high salinity 34,35 .…”

Section: Hydrous Mineral-rich Duricrust At the Zhurong Landing Regionmentioning

confidence: 98%

“…These promote the formation of crystals with large sizes because the size of crystals is inversely related to nucleation density 43 . Selenite gypsum must have formed under high-salinity environments 34,35 . The silica would have precipitated due to the increasing salinity of the liquid water with progressive freezing because the solubility of silica decreases with increasing salinity 44 .…”

Section: Upwelling Meltwater and Alteration Of Surface Materialsmentioning

confidence: 99%

Ground ice-magma interaction resurfaced the landing region of the Zhurong rover during the Amazonian

Michalski

Liu

et al. 2023

Preprint

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Despite a consensus view that Mars has been cold and icy throughout the Amazonian (3 billion years ago until present), the Zhurong rover has provided striking evidence for aqueous resurfacing processes in and around the landing site during this time period. Here, we report a close association of magmatism (i.e. dikes) and several distinctive landforms (e.g. mud volcanoes and troughs) indicating that ground ice in the Vastitas Borealis Formation (VBF) was thawed by the magma heating causing the collapse of VBF to form distinct landforms and alteration mineralogy. This collapse released pressurized meltwater and mud, producing mud volcanoes and muddy water. Upon freezing, the slurry materials were further buried by younger porous sediments. Freezing of the upwelled chemical-rich groundwater potentially circulated by cryosuction produced large crystals of sulphate (probably selentite) unlike sulphates previously identified on Mars, evidencing relatively young aqueous alteration on Mars driven by magma-ice interactions.

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Selenite facies in marine evaporites: a review

Ortı́

2010

Quaternary Carbonate and Evaporite Sedimentary Facies and Their Ancient Analogues

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The term "selenite facies" describes evaporitic, primary precipitates of coarse-crystalline gypsum formed on a depositional floor. The crystals comprising these autochthonous facies commonly display competitive growth patterns. Modern marine selenite facies have been studied in coastal salt works (evaporative salinas) and in some natural coastal lakes where gypsum is precipitating or has been precipitating in recent times. In ancient marine formations, selenite crystals display two major facies groups: bedded to massive selenites; and domal selenites. Good examples of selenite facies occur in the Miocene of the Mediterranean region (Messinian) and in the Carpathian Foredeep (Badenian). In ancient examples, selenite facies have been preserved as pseudomorphic anhydrite at depth and as pseudomorphic secondary gypsum at outcrop. In such cases, their identification may be difficult, owing to the intense diagenetic transformations undergone by many evaporites. Ancient occurrences of selenite facies cover a wide range of settings:(1) flanking selenite shelves; (2) narrow flanking selenite shelves; (3) selenite platforms covering salt-filled basins; and (4) selenite basins. All occurrences are sensitive to changes in sedimentological conditions and require specific environmental configurations. In particular, they depend on the existence of an outflow of heavy brines to prevent oxygen depletion in the water column, and the accumulation of chlorides on the platforms and in the basins.

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La halite du bassin potassique sud-pyreneen (Eocene superieur, Espagne)

Cited by 11 publications

References 0 publications

Rapid hydration and weakening of anhydrite under stress: Implications for natural hydration in the Earth’s crust and mantle

Rapid hydration and weakening of anhydrite under stress: Implications for natural hydration in the Earth’s crust and mantle

Ground ice-magma interaction resurfaced the landing region of the Zhurong rover during the Amazonian

Selenite facies in marine evaporites: a review

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