The fibrous Gypsum of Nottinghamshire

Richardson, W. Alfred

doi:10.1180/minmag.1920.019.91.01

Cited by 15 publications

(15 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The fibrous and acicular gypsum crystals from the laminated evaporites are similar to satin spar gypsum usually found filling fractures (e.g. Richardson, 1920;Shearman et al, 1972;Mossop & Shearman, 1973;Stewart, 1979;Gustavson et al, 1994;El Tabakh et al, 1998). In this instance, however, the satin spar gypsum is not related to fractures, but it records replacement of the chevron gypsum.…”

Section: Burial Overprint On Isotope Valuesmentioning

confidence: 61%

See 1 more Smart Citation

An Upper Aptian saline pan/lake system from the Brazilian equatorial margin: integration of facies and isotopes

2005

View full text Add to dashboard Cite

Facies and isotope (Sr and S) data were combined in order to discuss the genesis and palaeohydrology of an Upper Aptian evaporite succession formed during the initial development of an intra‐continental rift from northern Brazil. Comparison of facies distribution between two investigated areas shows: (i) stable, well‐stratified and hypersaline lakes with periods of anoxia and closure in the eastern margin of the basin, where there was evaporite precipitation only in central lake environments; and (ii) more ephemeral conditions in the eastern margin of the basin, where a saline pan complex developed and evaporite precipitation took place mainly in marginal salinas and surrounding mudflats. In both areas, expansion/contraction cycles developed as sedimentation took place, accompanied by a decrease and then an increase in 87Sr/86Sr‐ and δ34S‐isotope values. This, combined with the wide distribution of Sr‐ and S‐isotope data within individual depositional cycles, as well as petrographic and scanning electronic microscopic (SEM) images, led to the conclusion that diagenesis was not enough to obscure the primary geochemical signature. A non‐marine brine source is suggested by 87Sr/86Sr ratios between 0·707824 and 0·709280, which are higher than those from Upper Aptian sea water (i.e. between 0·70720 and 0·70735). The δ34S value varies from 16·12 to 17·89‰ in the eastern margin of the basin, which is in disagreement with Upper Aptian marine values (13 to 16‰). Both geochemical tracers were influenced by facies characteristics, and thus a model is provided, where 87Sr/86Sr values respond to changes in expansion and contraction episodes of saline pan/lake systems.

show abstract

Section: Burial Overprint On Isotope Valuesmentioning

confidence: 61%

Section: Discussionmentioning

confidence: 88%

An Upper Aptian saline pan/lake system from the Brazilian equatorial margin: integration of facies and isotopes

2005

View full text Add to dashboard Cite

show abstract

“…Almost all but the finest anhydrite sheets are characterized by a poorly-developed vertical fabric which resembles the cross-fibre structure present in calcite 'beef' (Kendall and Simpson 1974) and gypsum 'satin-spar' (Richardson 1920;Shearman et al 1972) veins. Like 'beef' and 'satin-spar' veins the 'fibrous' fabric is vertical regardless of the orientation of the anhydrite sheets relative to bedding.…”

Section: Features Of the Anhydrite Sheetsmentioning

confidence: 96%

“…In some anhydrite sheets the variations in anhydrite crystallinity and texture locally appear to define a former acicular texture, sometimes with the former crystals arranged into coneshaped aggregates similar to those in some calcite veins (Kendall and Simpson 1974, pl. 2) and recorded from satin-spar veins (Richardson 1920). Anhydrite replacement of former calcite veins is unlikely since the anhydrite sheets may Can.…”

Section: Origin Of Anhydrite Sheetsmentioning

confidence: 99%

Anhydrite Replacements of Gypsum (Satin-Spar) Veins in the Mississippian Caprocks of Southeastern Saskatchewan

Kendall¹

1975

Can. J. Earth Sci.

View full text Add to dashboard Cite

Sheets of anhydrite, up to 5 cm thick, occur abundantly in southeastern Saskatchewan within dolomitized Mississippian carbonates where these are unconformably overlain by Watrous red beds. The sheets are interpreted as former gypsum veins that have lost structural water as a result of later burial. Replacement by anhydrite was accompanied by no loss of volume and the fibrous vein structure of the former gypsum is partially mimicked by the anhydrite.Gypsum veining is believed to have occurred as a result of the migration of calcium sulphate-rich brines through the Mississippian carbonates after the deposition of the Watrous red beds.

show abstract

“…Thus, the veins observed at Watchet are driven by fluid overpressure, and are thus primarily hydrofractures, although during precipitation the crystallization pressure of the gypsum may have contributed to the opening of the veins. Gustavson, Hovorka & Dutton (1994) summarized the main mechanisms for the formation of fibrous gypsum (satin spar) veins in sedimentary rocks overlying evaporates as follows: (1) Contraction of the host rock by dehydration (Richardson, 1920); (2) hydration of anhydrite to gypsum (Stewart, 1979); (3) tectonism (Forbes, 1958); (4) force of crystallization (Taber, 1916;Halferdal, 1960); (5) hydraulic overpressure (Shearman et al 1972); and (6) subsidence due to dissolution of underlying evaporites (Gustavson, 1980;Goldstein & Collins, 1984). Gustavson, Hovorka & Dutton (1994) explain that these mechanisms do not link the following processes, namely, the origin of fractures, the gypsum-saturated groundwater, and the precipitation of gypsum.…”

Section: Discussionmentioning

confidence: 99%

Geometry and formation of gypsum veins in mudstones at Watchet, Somerset, SW England

Philipp

2008

Geol. Mag.

View full text Add to dashboard Cite

-Gypsum veins and faults were studied in red mudstones of the Upper Triassic Mercia Mudstone Group, in the Bristol Channel Basin, exposed in E-W-trending cliffs at Watchet on the Somerset Coast (SW England). In nodular gypsum horizons, individual gypsum nodules are connected by subhorizontal gypsum veins. In evaporite-free mudstone layers, however, dense anastomosing networks of gypsum veins occur. In a 300 m long profile dissected by 28 (mostly) normal faults with small displacements, 24 faults have veins following them, indicating palaeofluid transport along the fault planes. Ninety-seven cross-cutting relationships and mostly perpendicular vein fibres indicate that the veins are primarily extension fractures. The thickest veins in the vein network are subhorizontal (160 measurements), indicating a vertical orientation of the minimum principal compressive stress (horizontal basin compression). Such a stress state may have existed during basin inversion associated with Alpine compression (late Cretaceous to early Tertiary). I propose that the gypsum veins are the result of hydrofracturing. In the gypsum nodules, then presumably consisting of anhydrite, overpressure was generated related to the hydration of anhydrite to gypsum. Stress concentration around the nodules led to rupturing and injection of thin subhorizontal hydrofractures. Some of the calcium-sulphate saturated fluids were then transported upwards along the faults and gained access to evaporite-free mudstone layers where dense anastomosing vein networks developed. Most veins were arrested during their propagation by layers with contrasting mechanical properties (stress barriers). Some veins, however, propagated through the barriers along faults to shallower levels. The dense networks of mineral veins observed in Watchet indicate that hydrofractures can generate a very high temporary permeability in fluid reservoirs.

show abstract

The fibrous Gypsum of Nottinghamshire

Cited by 15 publications

References 5 publications

An Upper Aptian saline pan/lake system from the Brazilian equatorial margin: integration of facies and isotopes

An Upper Aptian saline pan/lake system from the Brazilian equatorial margin: integration of facies and isotopes

Anhydrite Replacements of Gypsum (Satin-Spar) Veins in the Mississippian Caprocks of Southeastern Saskatchewan

Geometry and formation of gypsum veins in mudstones at Watchet, Somerset, SW England

Contact Info

Product

Resources

About