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VII.—Origin of the Crystalline Limestones of Ceylon

Published online by Cambridge University Press:  01 May 2009

A. K. Coomáraswámy
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Extract

It is generally supposed that the crystalline limestones which occur amongst the schists, associated with orthogneisses, in various parts of the world, are altered sedimentary limestones whose accessory minerals and crystalline structure have been developed by simple contact and dynamo-metamorphism; and no doubt many crystalline limestones are of sedimentary origin, and owe their peculiarities to these agencies. In other cases the peculiar mode of occurrence of such rocks or their manner of association with igneous rocks (orthogneisses or nepheline-syenites) has led to the suggestion of other theories.

Type
Original Articles
Information
Geological Magazine , Volume 9 , Issue 8 , August 1902 , pp. 375 - 378
Copyright
Copyright © Cambridge University Press 1902

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References

page 375 note 1 Geol. Fören. Stockholm. Förh., 1895, vol. xvii, pp. 100 and 214.Google Scholar

page 375 note 2 Phil. Trans. Roy. Soc., 1896, vol. clxxxvii a, pp. 151–228.Google Scholar

page 376 note 1 Rep. Brit. Assoc., 1887, p. 706.Google Scholar

page 376 note 2 Geol. Mag., 1902, p. 285.Google Scholar

page 376 note 3 Mem. Geol. Surv. India, 1901, vol. xxx, pt. 3, p. 175.Google Scholar

page 376 note 4 Holland, : Mem. Geol. Surv. India, loc. cit., p. 197Google Scholar. Adams, : Amer. Journ. Sci., 1894, vol. xlviii, p. 14.Google Scholar

page 376 note 5 Quart. Journ. Geol. Soc., 1900, vol. lvi, p. 606, also pl. xxxiii, fig. 1.Google Scholar

page 376 note 6 Quart. Journ. Geol. Soc., 1902, vol. lviii, p. 399.Google Scholar

page 376 note 7 I have met with rocks almost composed of dark mica in one or two localities (Yatirawana, near Wattegama, and Talbot Town, Galle) associated with the granulites. Almost any mineral occurring in the granulites may, however, be sometimes met with in this way as a main constituent of a local variety. It is, however, quite true that some varieties rich in garnet and biotite are not altogether unlike much altered sedimentary rocks, though I do not myself regard them as such. Lacroix has described some rocks in which andalusite, sillimanite, and corundum occur, but unfortunately the localities in Ceylon are unknown. Possibly these minerals indicate the existence of altered sedimentary rocks, but this is by no means necessarily the case.

page 377 note 1 The direct use of the term ‘molten’ is avoided, inasmuch as we can know but little of the conditions of matter under very great pressure, and it is inadvisable to use the same terms in the description of conditions which, though analogous, must yet be very different.

page 377 note 2 Cf. J. J. H. Teall, Geol. Mag., 1886, p. 349.Google Scholar

page 377 note 3 It is evident that the limestones have not (except very locally) suffered from deforming earth-movements since the development of the accessory minerals, whose varying abundance is largely the cause of the apparent foliation.