Abstract
Chlorite-muscovite porphyroblasts occur in the low-grade metapelites from Nurra (NW Sardinia). Although actually heterogeneous and built up by two different intermixed minerals, the porphyroblasts strongly simulate optical homogeneity and produce microprobe analyses that are typical for metamorphic vermiculite. Transmission and scanning electron microscopy, combined with analytical facilities, leads to a deeper characterization of the porphyroblasts, that actually consist of a random association of chlorite and muscovite.
As a further result, the present study also shows that the existing criteria used to identify metamorphic vermiculite, namely optical features and microprobe composition do not warrant the correct identification.
Finally, the present results once more confirm the importance of back-scattered electron imaging in the SEM as a powerful tool for the routine petrographic study of sedimentary and low-grade metamorphic rocks.
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References
Ahn JH, Peacor DR (1985) Transmission electron microscopic study of diagenetic chlorite in Gulf Coast argillaceous sediments. Clays and Clay Minerals 33:228–236
Albee A, Ray L (1970) Correction factors for electron-probe micro-analysis of silicates, oxides, carbonates, phosphates and sulphates. Anal Chem 42:1408–1414
Bailey SW (1980) Summary of recommendations of AIPEA nomenclature committee on clay minerals. Amer Mineral 65:1–7
Bayliss P (1975) Nomenclature of the trioctahedral chlorites. Can Mineral 13:178–180
Black PM (1975) Mineralogy of New Caledonian metamorphic rocks.IV. Sheet silicates from Ouégoa district. Contrib Mineral Petrol 49:269–284
Carmignani L, Franceschelli M, Pertusati PC, Memmi I, Ricci CA (1982) An example of compositional control of the celadonite content of muscovite and the incoming of biotite in metapelites (Nurra, NW Sardinia). N Jb Mineral Mh 7:289–311
Carmignani L, Franceschelli M, Pertusati PC, Ricci CA (1979) Evoluzione tettonico-metamorfica del basamento ercinico della Nurra (Sardegna NW). Mem Soc Geol It 20:57–84
Hey MH (1954) A new review of the chlorites. Mineral Mag 30:277–292
Lee JH, Ahn JH, Peacor DR (1985) Textures in layered silicates: progressive changes through diagenesis and low-temperature metamorphism. Journ Sedim Petrol 55:532–540
Lee JH, Peacor DR (1983) Intralayer transitions in phyllosilicates of Martinsburg shale. Nature 303:608–609
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
Maresch WV, Massonne HJ, Czank M (1985) Ordered and disordered chlorite/biotite interstratifications as alteration products of chlorite. N Jb Mineral Abh 152:79–100
Mellini M, Menichini R (1984) Proportionality factors for thin film TEM/EDS microanalysis of silicate minerals. Rend Soc Ital Miner Petrol 40:261–266
Mellini M, Oberti R, Rossi G (1983) Crystal chemistry and micro-structure of pyroxenes and amphiboles in the coronas of the Bergen Arcs and of the Sognefjord region, western Norway. Per Mineral 52:583–615
Mickledust RL, Fiori CE, Heinrich KFS (1978) A compact procedure for quantitative Energy Dispersive Electron Probe X-Ray Analysis. NBS Technical note
Mposkos E, Perdikatsis V (1982) Potassium-bearing chlorite in the metapelitic schists of the west region of Samos island (Greece). N Jb Mineral Mh 8:361–372
Nicot E (1981) Les phyllosilicates des terrains précambriens du Nord-Ouest du Montana (USA) dans le transition anchizone-èpizone. Bull Minéral 104:615–624
Olives J, Amouric M (1984) Biotite chloritization by interlayer brucitization as seen by HRTEM. Amer Mineral 69:869–871
Olives J, Amouric M, De Fouquet C, Baronnet A (1983) Interlayering and interlayer slip in biotite as seen by HRTEM. Amer Mineral 68:754–758
Page R (1980) Partial interlayers in phyllosilicates studied by transmission electron microscopy. Contrib Mineral Petrol 75:309–314
Page R, Wenk HR (1979) Phyllosilicate alteration of plagioclase studied by transmission electron microscopy. Geology 7:393–397
Pye K, Krinsley DH (1984) Petrographic examination of sedimentary rocks in the SEM using backscattered electron detectors. Journ Sedim Petrol 54:877–888
Russ JC (1979) Modifications and extensions to NBS Frame-C Microbeam Analysis. San Francisco, San Francisco Press
Veblen DR (1983) Microstructures and mixed layering in inter-grown wonesite, chlorite, talc, biotite and kaolinite. Amer Mineral 68:566–580
Veblen DR, Ferry JM (1983) A TEM study of the biotite-chlorite reaction and comparison with petrologic observations. Amer Mineral 68:1160–1168
Velde B (1978) High Temperature or Metamorphic Vermiculites. Contrib Mineral Petrol 66:319–323
White SH, Hugget JM, Shaw HF (1985) Electron-optical studies of phyllosilicates intergrowths in sedimentary and metamorphic rocks. Mineral Mag 49:413–423
Woodland BG (1985) Relationship of concretions and chlorite-muscovite porphyroblasts to the development of domainal cleavage in low-grade metamorphic deformed rocks from north-central Wales, Great Britain. J Struct Geol 7:205–215
Yan Y, Anovitz LM, Essene EJ, Peacor DR (1984) Phlogopite-chlorite reaction mechanisms and physical conditions during retrograde reactions in the Marble Formation, Franklin, New Jersey. Contrib Mineral Petrol 88:299–306
Ziebold TO, Ogilvie RE (1964) An empirical method for electron microanalysis. Anal Chem 36:322–327
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Franceschelli, M., Mellini, M., Memmi, I. et al. Fine-scale chlorite-muscovite association in low-grade metapelites from Nurra (NW Sardinia), and the possible misidentification of metamorphic vermiculite. Contr. Mineral. and Petrol. 93, 137–143 (1986). https://doi.org/10.1007/BF00371315
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DOI: https://doi.org/10.1007/BF00371315