An occurrence of palygorslcite in the Shetland Isles

Stephen, I.

doi:10.1180/minmag.1954.030.226.07

Cited by 28 publications

(8 citation statements)

References 4 publications

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“…The results almost coincided with those of Gerstl et alU and Heller et af.l 6 who, however, studied these variations using SEM. The measurements of length, breadth and L/ B ratios of fibres reveal some interesting features (Table I).…”

supporting

confidence: 88%

Dehydration Transformation in Palygorskite

Bhattacherjee¹,

Lokanatha²

1984

Transactions of the Indian Ceramic Society

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supporting

confidence: 88%

Dehydration Transformation in Palygorskite

Bhattacherjee¹,

Lokanatha²

1984

Transactions of the Indian Ceramic Society

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“…These rocks usually form under tropical to subtropical conditions preferably in continental lacustrine or in shallow marine environments (e.g., Singer 1979;Callen 1984;Jones and Conko 2011). Palygorskite and Al-sepiolite may also form hydrothermally and occur in fractures or as monomineralic veins in mainly magmatic host rocks (Stephen 1954;Christ et al 1969;Furbish and Sandow 1976;Gibbs et al 1993). Furthermore, these minerals are found in discrete clay-rich layers of strongly hydrothermally overprinted volcanic rocks (Irkec and Ü nlü 1993) providing a link to the metasomatically altered protoliths described before.…”

Section: Discussionmentioning

confidence: 99%

“…For instance, Stephen (1954) found hydrothermal palygorskite on the Shetland Isles, Christ et al (1969) investigated hydrothermal palygorskite and calcite in hydrothermal veins from New Mexico (USA), and Furbish and Sandow (1976) described direct precipitation of palygorskite in fractures of the Day Book dunite (North Carolina, USA). Gibbs et al (1993) describes hydrothermal palygorskite-associated with ferromanganese mineralization-that formed due to interaction of hydrothermal fluids with oceanic basalt and/or ultramafic rocks in boxworktextured veins and by direct precipitation in mudstone at the seafloor.…”

Section: Sepiolite-bearing Hydrothermally Altered Volcanic Rocks Fromentioning

confidence: 99%

Protoliths and phase petrology of whiteschists

Franz

Romer

Capitani

2013

Contrib Mineral Petrol

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Whiteschists appear in numerous high-and ultrahigh-pressure rock suites and are characterized by the mineral assemblage kyanite ? talc (?-quartz or coesite). We demonstrate that whiteschist mineral assemblages are well stable up to pressures of more than 4 GPa but may already form at pressures of 0.5 GPa. The formation of whiteschists largely depends on the composition of the protolith, which requires elevated contents of Al and Mg as well as low Fe, Ca, and Na contents, as otherwise chloritoid, amphibole, feldspar, or omphacite are formed instead of kyanite or talc. Furthermore, the stability field of the whiteschist mineral assemblage strongly depends on XCO 2 and fO 2 : already at low values of XCO 2 , CO 2 binds Mg to carbonates strongly reducing the whiteschist stability field, whereas high fO 2 enlarges the stability field and stabilizes yoderite. Thus, the scarcity of whiteschist is not necessarily due to unusual P-T conditions, but to the restricted range of suitable protolith compositions and the spatial distribution of these protoliths: (1) continental sedimentary rocks and (2) hydrothermally and metasomatically altered felsic to mafic rocks. The continental sedimentary rocks that may produce whiteschist mineral assemblages typically have been deposited under arid climatic conditions in closed evaporitic basins and may be restricted to relatively low latitudes. These rocks often contain large amounts of the clay minerals palygorskite and sepiolite. Marine sediments generally do not yield whiteschist mineral assemblages as marine shales commonly have too high iron contents. Sabkha deposits may have too high CO 2 contents. Protoliths of appropriate geochemical composition occur in and on continental crust. Therefore, whiteschist assemblages typically are only found in settings of continental collision or where continental fragments were involved in subduction. Our calculations demonstrate that whiteschists can form by closed-system metamorphism, which implies that the chemical and isotopic composition of these rocks provide constraints on the development of the protoliths.

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“…Stephen (1954) also reported the formation of palygorskite by hydrothermal action directly on igneous rocks. On the other hand, palygorskite is also reported to form either in fresh-water or lagoonal sediments (Kerr, 1937) or in shallow marine environments as a result of the action Mg-rich solution on terrigenous clays (Mùller, 1961).…”

Section: Zδmentioning

confidence: 97%

Clay Mineralogy of Deep-Sea Sediments in the Northwestern Pacific, DSDP, Leg 20

Okada¹,

Tomita²

1973

Initial Reports of the Deep Sea Drilling Project

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INTRODUCTIONClay mineral study of samples collected during Leg 20 of the Deep Sea Drilling Project in the western north Pacific was carried out mainly by means of X-ray diffraction analyses. Emphasis was placed on determining vertical changes in mineral composition of sediments at each site.Results of the semiquantitative and quantitative determinations of mineral compositions of analyzed samples are shown in Tables 1, 2, 3, 5, and 7. The mineral suites presented here show some unusual characters as discussed below. The influence of burial diagenesis is also evidenced in the vertical distribution of some authigenic minerals.These results may contribute to a better understanding of deep-sea sedimentation on the northwestern Pacific plate. ANALYTICAL PROCEDURESEach sample was dried in air, and X-ray diffraction patterns were obtained using aggregates on glass slides. The clay minerals were identified as follows:1) X-ray analysis: (a) untreated, (b) treated with ethylene glycol, and (c) heated for 1 hour at each of the following temperatures: 300°C, 500°C, and 600°C. In each case X-ray examination was performed at room temperature immediately upon cooling.2) Differential thermal analysis for selected samples.3) Electron microprobe X-ray analyses by the Shimadzu-ARL Electron Microprobe X-Ray Analyzer EMX-SM for selected samples. Intensity Ratios of Basal Reflections of Clay MineralsIn the case where principal basal reflections of clay minerals do not overlap with one another, it is easy to obtain the intensity ratio of reflections. When a specimen has a complex clay-mineral composition, the reflections of respective clay minerals sometimes overlap. In such cases, the specimen must be treated either thermally or chemically to eliminate or move X-ray reflections of certain minerals, so that the reflection intensity of individual minerals can be obtained.When montmorillonite and chlorite coexist in one specimen and the (001) reflections of both minerals overlap with each other, the reflection intensity of each mineral cannot be obtained without any treatment. In this case, by heating the specimen at 300°C, the 15 Å reflection of montmorillonite is moved to 9 to 10 Å, and the intensity of the (001) reflection of chlorite is obtained. Treatment with ethylene glycol or glycerol usually shifts the reflection of montmorillonite from 15 Å to 17 Å. The (001) reflection intensity of montmorillonite can be obtained by subtracting the (001) reflection intensity of chlorite from the preheating or pretreating reflection intensity at 15 Å.In a specimen with coexisting kaolinite and chlorite, their overlapping reflections make it difficult to determine quantitatively these mineral compositions. For such specimens Wada's method (Wada, 1961) and heat treatment were adopted.The following shows examples of the determination of some intensity ratios of reflections of clay minerals.Case 1 Montmorillonite (two layers of water molecules between silicate layers)-kaolinite mixture. This is the situation in which samples contain both montmoril...

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An occurrence of palygorslcite in the Shetland Isles

Cited by 28 publications

References 4 publications

Dehydration Transformation in Palygorskite

Dehydration Transformation in Palygorskite

Protoliths and phase petrology of whiteschists

Clay Mineralogy of Deep-Sea Sediments in the Northwestern Pacific, DSDP, Leg 20

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