Abstract
A suite of pelitic rocks around Kandra, Singhbhum District, Bihar, displays a metamorphic gradient registered by the index minerals chlorite, biotite, garnet, staurolite and sillimanite in a Barrovian sequence. Metamorphism was by and large coeval with folding movements, and correlating the internal fabric of minerals and deformational characters, a regular sequence of the index minerals is derived. It is argued that the chronological order by itself is not sufficient to prove that metamorphism was progressive in time.
Among the index minerals, garnet appears to have formed by the reaction chlorite+biotitea+quartz ⇌ garnet+biotiteb+H2O. For the origin of sillimanite, a new reaction, 3 staurolite+muscovite+quartz=7 sillimanite+biotite+3H2O, is suggested on the basis of significant textural features. Textural and petrological indications regarding the formation of staurolite are in discordance. Staurolite was either derived from the biotite zone phases, or should be taken to have formed, against textural evidences, from chloritoids of the garnet zone.
Graphical analysis of the assemblages by Thompson's ‘AFM’ projection reveals that chlorite and staurolite are excess phases owing to retrogression and incomplete reaction. Shifting of apices of triangular fields and intersection of garnet-biotite tie lines within a zone can be satisfactorily explained in terms of extra components CaO and MnO or their ratios. It is pointed out that if MgO/(MgO + FeO) between two phases show a linear relation, their tie lines will be concurrent on the AF side of the projection, the point of concurrence reflecting equilibrium and temperature of recrystallisation.
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References
Albee, A. L.: Phase equilibria in three assemblages of kyanite-zone pelitic schists, Lincoln Mountain Quadrangle, Central Vermont. J. Petrology 6, 246–301 (1965).
Best, M. G., and L. E. Weiss: Mineralogical relations in some pelitic hornfelses from the southern Sierra Nevada, California. Am. Mineralogist 49, 1240–1266 (1964).
Billings, M. P.: Regional metamorphism of the Littleton-Moosilauke area, New Hampshire. Bull. Geol. Soc. Am. 48, 463–566 (1937).
Chakraborty, K. R.: A study of regional metamorphism of pelitic rocks from Kandra, Bihar, with special reference to garnet-biotite equilibria. Ph. D. Thesis, I.I.T., Kharagpur (1966).
Chinner, G. A.: Pelitic gneisses with varying ferrous/ferric ratios from Glen Clova, Angus, Scotland. J. Petrology 1, 178–217 (1960).
—: The origin of sillimanite in Glen Clova, Angus. J. Petrology 2, 312–323 (1961).
- The kyanite isograd in Glen Clova, Angus, Scotland. Mineral. Mag. Tilley volume, 132–143 (1965).
Clarke, F. W.: Data of Geochemistry. U.S. Geol. Survey Bull. 770 (1924).
Dunn, J. A., and A. K. Dey: The geology and petrology of Eastern Singhbhum and surrounding area. Mem. Geol. Survey India 69 (2), 281–456 (1942).
Eckel, E. C.: On the chemical composition of American shales and roofing slates. J. Geol. 12, 25–29 (1904).
Francis, G. H.: Facies boundaries in pelites at the middle grades of regional metamorphism. Geol. Mag. 93, 353–368 (1956).
Ghosh, S. K.: Structural, metamorphic and migmatitic history of the area around Kuilapal, Eastern India. Quart. J. Geol. Mining Met. Soc. India 35, 211–234 (1963).
Green, J. C.: High-level metamorphism of pelitic rocks in northern New Hampshire. Am. Mineralogist 48, 991–1023 (1963).
Halferdahl, L. B.: Chloritoid: Its composition, X-ray and optical properties, stability and occurrence. J. Petrology 2, 49–135 (1961).
Kretz, R.: Chemical study of garnet, biotite and hornblende from gneisses of southwestern Quebec, with emphasis on distribution of elements in coexisting minerals. J. Geol. 67, 371–402 (1959).
Miyashiro, A.: Thermodynamics of reactions of rock forming minerals with silica, Pt. IV. Japan. J. Geol. and Geography 31, 113–120 (1960).
Nanz, R. H.: Chemical composition of Precambrian slates with notes on the geochemical evolution of lutites. J. Geol. 61, 51–64 (1953).
Newton, R. C.: Kyanite-sillimanite equilibrium at 750° C. Science 151, 1222–1225 (1966a).
—: Kyanite-andalusite equilibrium at 700° C to 800° C. Science 153, 170–172 (1966b).
Pettijohn, F. J.: Sedimentary rocks. New York: Harper and Row 1956.
Phinney, W. C.: Phase equilibria in the metamorphic rocks of St. Paul Island and Cape North, Nova Scotia. J. Petrology 4, 90–130 (1963).
Ramberg, H.: The origin of metamorphic and metasomatic rocks. Chicago: The University of Chicago Press 1952.
Ray, S.: Zonal metamorphism in the eastern Himalaya and some aspects of local geology. Quart. J. Geol. Mining Met. Soc. India 19, 117–140 (1947).
Roy, A. B.: Structure and petrology of the area around Gamharia, Singhbhum. Unpublished Ph. D. Thesis, Jadavpur University (1964).
—: Interrelation of metamorphism and deformation in Central Singhbhum, Eastern India. Geol. en Mijnbouw 45, 365–374 (1966).
Segnit, R. E., and G. C. Kennedy: Reactions and melting relations in the system muscovitequartz at high pressures. Amer. J. Sci. 259, 280–287 (1961).
Sen, S. K., and K. R. Chakraborty: Magnesium-iron exchange equilibrium in garnet-biotite and metamorphic grade (in press).
Shaw, D. M.: Geochemistry of pelitic rocks, Part II. Major elements and general geochemistry. Bull. Geol. Soc. Am. 67, 919–934 (1956).
Streckeisen, A.: Geologie und Petrographie der Flüelagruppe (Graubünden). Schweiz. mineral, petrog. Mitt. 8, 87–239 (1928).
Suzuki, J.: Über die Staurolith-Andalusit-Paragenesis im Glimmergneiß von Pirodina bei Brissago (Tessin). Schweiz. mineral. petrog. Mitt. 10, 117–132 (1930).
Thompson jr., J. B.: The graphical analysis of mineral assemblages in pelitic schists. Am. Mineralogist 42, 842–858 (1957).
Tozer, C. F.: The mode of occurrence of sillimanite in the Glen dist. Cy. Donegal. Geol. Mag. 92, 310–320 (1955).
Turner, F. J., and J. Verhoogen: Igneous and metamorphic petrology. New York: McGraw-Hill Book Co. 1960.
Woodland, B. G.: A petrographic study of thermally metamorphosed pelitic rocks in the Burke area, northeastern Vermont. Am. J. Sci. 261, 354–375 (1963).
Yoder jr., H. S.: Experimental studies on micas: a synthesis. Proc. 6th Nat. Conf. Clays and Clay Minerals, p. 42–66. New York: Pergamon Press 1959.
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Chakraborty, K.R., Sen, S.K. Regional metamorphism of pelitic rocks around Kandra, Singhbhum, Bihar. Contr. Mineral. and Petrol. 16, 210–232 (1967). https://doi.org/10.1007/BF00371093
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DOI: https://doi.org/10.1007/BF00371093