Compositional variation within some sedimentary chlorites and some comments on their origin

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Authors:Curtis, C. D.; Hughes, C. R.; Whiteman, J. A.; Whittle, C. K.
Author Affiliations:Primary:
Univ. Sheffield, Dep. Geol. and Metall., Sheffield, United Kingdom
Volume Title:Diagenesis and low-temperature metamorphism
Volume Authors:Robinson, D., editor
Source:Mineralogical Magazine, 49 Part 3(352), p.375-386; Diagenesis and low-temperature metamorphism, Bristol, United Kingdom, April 12-13, 1984, edited by D. Robinson. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0026-461X
Publication Date:1985
Note:In English. 20 refs.; illus. incl. 1 table
Summary:A range of authigenic sedimentary chlorites from sandstones has been studied by analytical transmission electron microscopy. Selected area (single crystal) electron diffraction patterns are of the Ib (β = 90°) polytype confirming the earlier observations of Hayes (1970). TEM analyses show all samples to be relatively rich in both Al and Fe. In the general formula (Mg,Fe,Al)n [Si8-xAlxO20](OH)16, x varies between 1.5 and 2.6; Fe/(Fe + Mg) between 0.47 and 0.83 and n between 10.80 and 11.54. Octahedral Al is close to 3 in this formulation and Fe2+ predominates over Fe3+. Swelling chlorites have significantly different compositions which are consistent with smectite/chlorite interstratifications. The Ib (β = 90°) polytype appears to be stable under conditions of moderate to deep burial. It replaces berthierine and swelling chlorites formed at lower temperatures. As commonly seen in grain coatings, however, it precipitates from porewater; solutes probably being contributed from several mineral decomposition reactions. [R.A.H.]
Subjects:Chamosite; Chlorite; Chlorite group; Clastic rocks; Clay mineralogy; Clinochlore; Diagenesis; Electron diffraction data; Materials; Mineral data; Sandstone; Sedimentary rocks; SEM data; Sheet silicates; Silicates; TEM data; X-ray data
Abstract Numbers:85M/3529
Record ID:1985075827
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland
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008 190110e198506 xxka 1 0 eng d
040 |a ViAlAGI  |c ViAlAGI 
072 7 |a 06A  |2 georeft 
100 1 |a Curtis, C. D.  |e analytic author  |u Univ. Sheffield, Dep. Geol. and Metall., Sheffield 
245 1 0 |a Compositional variation within some sedimentary chlorites and some comments on their origin 
300 |a p. 375-386 
500 |a In English. 20 refs. 
500 |a Abstract number: 85M/3529 
500 |a Abstractor: R.A.H. 
500 |a Affiliation: Univ. Sheffield, Dep. Geol. and Metall.; Sheffield; GBR; United Kingdom 
500 |a Key title: Mineralogical Magazine 
500 |a Source note: Mineralogical Magazine, 49 Part 3(352), p.375-386; Diagenesis and low-temperature metamorphism, Bristol, United Kingdom, April 12-13, 1984, edited by D. Robinson. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0026-461X 
500 |a Publication type: conference paper or compendium article 
504 |b 20 refs. 
510 3 |a GeoRef, Copyright 2019 American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland 
520 |a A range of authigenic sedimentary chlorites from sandstones has been studied by analytical transmission electron microscopy. Selected area (single crystal) electron diffraction patterns are of the Ib (β = 90°) polytype confirming the earlier observations of Hayes (1970). TEM analyses show all samples to be relatively rich in both Al and Fe. In the general formula (Mg,Fe,Al)<n` [Si<8-x`Al<x`O<20`](OH)<16`, x varies between 1.5 and 2.6; Fe/(Fe + Mg) between 0.47 and 0.83 and n between 10.80 and 11.54. Octahedral Al is close to 3 in this formulation and Fe>2+` predominates over Fe>3+`. Swelling chlorites have significantly different compositions which are consistent with smectite/chlorite interstratifications. The Ib (β = 90°) polytype appears to be stable under conditions of moderate to deep burial. It replaces berthierine and swelling chlorites formed at lower temperatures. As commonly seen in grain coatings, however, it precipitates from porewater; solutes probably being contributed from several mineral decomposition reactions. 
650 7 |a Chamosite  |2 georeft 
650 7 |a Chlorite  |2 georeft 
650 7 |a Chlorite group  |2 georeft 
650 7 |a Clastic rocks  |2 georeft 
650 7 |a Clay mineralogy  |2 georeft 
650 7 |a Clinochlore  |2 georeft 
650 7 |a Diagenesis  |2 georeft 
650 7 |a Electron diffraction data  |2 georeft 
650 7 |a Materials  |2 georeft 
650 7 |a Mineral data  |2 georeft 
650 7 |a Sandstone  |2 georeft 
650 7 |a Sedimentary rocks  |2 georeft 
650 7 |a SEM data  |2 georeft 
650 7 |a Sheet silicates  |2 georeft 
650 7 |a Silicates  |2 georeft 
650 7 |a TEM data  |2 georeft 
650 7 |a X-ray data  |2 georeft 
700 1 |a Hughes, C. R.,  |e analytic author 
700 1 |a Whiteman, J. A.,  |e analytic author 
700 1 |a Whittle, C. K.,  |e analytic author 
711 2 |a Diagenesis and low-temperature metamorphism  |d (1984 :  |c Bristol, United Kingdom)  
773 0 |a Robinson, D., editor  |t Diagenesis and low-temperature metamorphism  |d London : Mineralogical Society, Jun. 1985  |k Mineralogical Magazine  |x 0026-461X  |y MNLMBB  |n Mineralogical Magazine, 49 Part 3(352), p.375-386; Diagenesis and low-temperature metamorphism, Bristol, United Kingdom, April 12-13, 1984, edited by D. Robinson. Publisher: Mineralogical Society, London, United Kingdom. ISSN: 0026-461X Publication type: conference paper or compendium article  |g Vol. 49 , Part 3, no. 352  |h illus. incl. 1 table