Abstract
High-resolution transmission electron microscopy (HRTEM) measurements of the thickness of white mica crystallites were made on three pelite samples that represented a prograde transition from diagenetic mudstone though anchizonal slate to epizonal slate. Crystallite thickness, measured normal to (001), increases as grade increases, whereas the XRD measured 10 Å peak-profile, the Kubler index, decreases. The mode of the TEM-measured size population can be correlated with the effective crystallite size N(001) determined by XRD. The results indicate that the Kubler index of white mica crystallinity measures changes in the crystallite size population that result from prograde increases in the size of coherent X-ray scattering domains. These changes conform to the Scherrer relationship between XRD peak broadening and small crystallite size. Lattice ‘strain’ broadening is relatively unimportant, and is confined to white mica populations in the diagenetic mudstone. Rapid increases in crystallite size occur in the anchizone, coincident with cleavage development. Changes in the distribution of crystallite thickness with advancing grade and cleavage development are characteristic of grain-growth by Ostwald ripening. The Kubler index rapidly loses sensitivity as an indicator of metapelitic grade within the epizone.
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Ahn JH, Peacor DR (1986) Transmission and analytical electron microscopy of the smectite-to-illite transition. Clays Clay Miner 34:165–186
Ahn JH, Peacor DR, Essene EJ (1986) Cation-diffusion-induced characteristic beam damage in transmission electron microscope images of micas. Ultramicroscopy 19:375–382
Árkai P (1977) Low-grade metamorphism of Palaeozoic sedimentary formations of the Szendrö Mountains (NE-Hungary). Acta Geol Acad Sci Hung 21:53–80
Árkai P, Tóth MN (1983) Illite crystallinity: combined effects of domain size and lattice distortion. Acta Geol Hung 26:341–358
Árkai P, Horváth ZA, Tóth M (1981) Transitional very low- and low-grade regional metamorphism of the Palaeozoic formations, Uppony Mountains NE-Hungary: mineral assemblages, illite-crystallinity, bo and vitrinite reflectance data. Acta Geol Acad Sci Hung 24:265–294
Austin GS, Glass HD, Hughes RE (1989) Resolution of the poly-type structure of some illitic clay minerals that appear to be 1Md. Clays Clay Miner 37:128–134
Bevins RE, Merriman RJ (1988) Compositional controls on coexisting prehnite-actinolite and prehnite-pumpellyite facies assemblages in the Tal y Fan metabasite intrusion, North Wales: implications for Caledonian metamorphic field gradients. J Metamorphic Geol 6:17–39
Blenkinsop TG (1988) Definition of low-grade metamorphic zones using illite crystallinity. J Metamorphic Geol 6:623–636
Cashman KV, Ferry JM (1988) Crystal size distribution (CSD) in rocks and the kinetics and dynamics of crystallization III. Metamorphic crystallization. Contrib Mineral Petrol 99:401–415
Eberl DD, Środoń J (1988) Ostwald ripening and interparticle-diffraction effects from illite crystals. Am Mineral 73:1335–1345
Eberl DD, Velde B (1989) Beyond the Kubler index. Clay Miner 24:571–577
Eberl DD, Środoń J, Lee M, Nadeau P, Northrop HR (1987) Sericite from the Silverton caldera, Colorado: correlation among structure; composition, origin, and particle thickness. Am Mineral 72:914–934
Fortey NJ (1989) Low grade metamorphism in the Lower Ordovician Skiddaw Group of the Lake District, England. Proc Yorks Geol Soc 47:325–337
Frey M (1969) A mixed-layer paragonite/phengite of low-grade metamorphic origin. Contrib Mineral Petrol 24:63–65
Frey M (ed) (1987) Low Temperature Metamorphism. Blackie and Son Ltd., Glasgow
Howells MF, Reedman AJ, Campbell SDG (1990) Ordovician (Caradoc) marginal basin volcanism in Snowdonia (NW Wales). Mem Geol Surv GB (in press)
Ishii K (1988) Grain growth and re-orientation of phyllosilicate minerals during the development of slaty cleavage in the South Kitakami Mountains, northeast Japan. J Struct Geol 10:145–154
Jiang WT, Peacor DR, Merriman RJ, Roberts B (1990) Transmission and analytical electron microscopic study of mixed-layer illite/smectite formed as a apparent replacement product of diagenetic illite. Clays Clay Miner (in press)
Kisch HJ (1980) Incipient metamorphism of Cambro-Silurian clastic rocks from the Jämtland Supergroup, central Scandinavian Caledonides, western Sweden: illite crystallinity and ‘vitrinite’ reflectance. J Geol Soc London 137:271–288
Kisch HJ (1983) Mineralogy and petrology of burial diagenesis (burial metamorphism) and incipient metamorphism in clastic rocks. In: Larsen G, Chilinger GV (eds) Diagenesis in sediments and sedimentary rocks 2, Elsevier, Amsterdam, 289–493
Kisch HJ (1989a) Discordant relationship between degree of very low-grade metamorphism and the development of slaty cleavage. In: Cliff RA, Yardley BWD (eds) Evolution of Metamorphic Belts. Geol Soc Spec Publ 43:173–185
Kisch HJ (1989b) Calibration of the anchizone: a critical comparison of illite ‘crystallinity’ scales used for definition. J Metamorphic Geol 8:31–46
Kisch HJ, Frey M (1987) Effect of sample preparation on the measured 10 Å peak width of illite (illite ‘crystallinity’). In: Frey M (ed) Low temperature metamorphism. Blackie and Son Ltd., Glasgow, 301–304
Klug HP, Alexander LE (1974) X-ray Diffraction Procedures, 2nd edn. Wiley, New York
Knipe RJ (1981) The interaction of deformation and metamorphism in slates. Tectonophysics 78:249–272
Kreutzberger ME, Peacor DR (1988) Behaviour of illite and chlorite during pressure solution of shaly limestone of the Kalkberg Formation, Catskill, New York. J Struct Geol 10:803–811
Kubler B (1964) Le argiles, indicateurs de métamorphisme. Rev Inst Fr Pet 19:1093–1112
Kubler B (1967) Le cristallinité de l'illite et les zones tout à fait superieures du métamorphisme. In: Étages tectoniques. Colloque de Neuchâtel, pp 105–121
Kubler B (1968) Evaluation quantitative du métamorphisme par la cristallinité de l'illite. Bull Cent Rech Pau SNPA 2:385–397
Kubler B (1984) Les indicateurs des transformations physiques et chimiques dans la diagenèse, températeure et calorimétrie. In: Lagache M (ed) Thermométrie et barometrie géologiques. Soc Fr Minéral Cristallogr Paris:489–596
Lee JH, Peacor DR, Lewis DD, Wintsch RP (1984) Chlorite-illite/muscovite interlayered and interstratified crystals: a TEM/STEM study. Contrib Mineral Petrol 88:372–385
Lee JH, Ahn JH, Peacor DR (1985) Textures in layered silicates: Progressive changes through diagenesis and low-temperature metamorphism. J Sediment Petrol 55:532–540
Lee JH, Peacor DR, Lewis DD, Wintsch RP (1986) Evidence for syntectonic crystallisation for the mudstone to slate transition at Lehigh Gap, Pennsylvania, U.S.A. J Struct Geol 8:767–780
Livi KJT, Veblen DR, Ferry JM (1988) Electron microscope study of anchizone and epizone metamophosed shales from the Central Swiss Alps (abstract). Geol Soc Am Abstracts Program 20:244
Merriman RJ, Roberts B (1985) A survey of white mica crystallinity and polytypes in pelitic rocks of Snowdonia and Llyn, North Wales. Mineral Mag 49:305–319
Milodowski AE, Zalasiewicz JA (1990) The origin, deposition and prograde evolution of chlorite-mica stacks in Llandovery sediments of the central Wales Basin. Geol Mag (in press)
Ostwald W (1900) Über die vermeintliche Isomeric des roten und gelben Quecksilberoxyds und die Oberflächenspannung fester Körper. Z Phys Chem Stoechiom Verwandtschafts 34:495–503
Pesquera A, Velasco F (1988) Metamorphism of the Palaeozoic Cinco Villas massif (Basque Pyrenees): illite crystallinity and graphitization degree. Mineral Mag 52:615–625
Roberts B (1979) The Geology of Snowdonia and Llyn. Adam Hilger Ltd., Bristol
Roberts B (1981) Low grade and very low grade regional metabasic Ordovician rocks of Llyn and Snowdonia, Gwynedd, North Wales. Geol Mag 118:189–200
Roberts B, Merriman RJ (1985) The distinction between Caledonian burial and regional metamorphism in metapelites from North Wales: an analysis of isocryst patterns. J Geol Soc London 142:615–624
Roberts B, Merriman RJ (1990) Cambrian and Ordovician metabentonites and their relevance to the origins of associated mudrocks in the northern sector of the Lower Palaeozoic Welsh marginal basin. Geol Mag 127:31–43
Roberts B, Evans JA, Merriman RJ, Smith M (1989) Discussion on low grade metamorphism of the Welsh Lower Palaeozoic succession: an example of diastathermal metamorphism? J Geol Soc London 146:885–890
Roberts B, Morrison C, Hirons S (1990) Low grade metamorphism of the Manx Group, Isle of Man: a comparative study of white mica ‘crystallinity’ techniques. J Geol Soc London 147:271–277
Robinson D, Bevins RE (1986) Incipient metamorphism in the Lower Palaeozoic marginal basin of Wales. J Metamorphic Geol 4:101–113
Shau Y-H, Feather ME, Essene EJ, Peacor DR (1990) Genesis and solvus relations of submicroscopically intergrown paragonite and phengite in a blueschist from Northern California. Contrib Mineral Petrol (in press)
Środoń J (1984) X-ray diffraction of illitic materials. Clays Clay Miner 32:337–349
Środoń J, Andreoli C, Elass F, Robert M (1990) Direct HRTEM measurement of expandability of mixed-layer illite/smectite in bentonite rock. Clays Clay Miner (in press)
Veblen DR (1985) Direct TEM imaging of complex structures and defects in silicates. Annu Rev Earth Planet Sci 13:119–146
Weber F, Dunoyer de Segonzac G, Economou C (1976) Une nouvelle expression de la ‘cristallinité’ de l'illite et des micas. Notion d'‘épaisseur apparente’ des cristallites. CR Somm Soc Geol Fr 5:225–227
Weber K (1972) Notes on the determination of illite crystallinity. Neues Jahrb Mineral Monatsh 1972:267–276
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Merriman, R.J., Roberts, B. & Peacor, D.R. A transmission electron microscope study of white mica crystallite size distribution in a mudstone to slate transitional sequence, North Wales, UK. Contr. Mineral. and Petrol. 106, 27–40 (1990). https://doi.org/10.1007/BF00306406
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DOI: https://doi.org/10.1007/BF00306406