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V.—The Crawfordjohn Essexite and Associated Rocks

Published online by Cambridge University Press:  01 May 2009

Extract

Another type, which is found in both quarries and which under the microscope has the aspect of a monchiquite or limburgite,. probably represents the actual marginal rock of the intrusion. It consists of small microphenocrysts of augite and olivine in a dark matrix, which can be resolved into granular augite and magnetite in a nearly isotropic base. The latter, which sometimes contains felspar microlites, seems to be mainly analcite with some nephelite, as it can be readily gelatinized and stained, while the refractive index is very low. The felspar microlites are small and sometimes have a rough trachytic structure resembling that of the mugearites. Following Harker's suggestion that augite-olivine rocks with an isotropic base should be classed as limburgites when the base is glass and as monchiquites when it is analcite, this rock can be included in the latter, group. The parts which are richer in felspar may be termed analcite-basalts.

Type
Original Articles
Copyright
Copyright © Cambridge University Press 1915

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References

page 513 note 1 This rock was first brought to my notice by Mr. W. R. Smellie.

page 513 note 2 Petrology for Students, 4th ed., 1908, p. 158.Google Scholar

page 514 note 1 Bailey, E. B. in Geology of East Lothian (Mem. Geol. Surv.), 1910, p. 99, pp. 105–13.Google Scholar

page 514 note 2 Geological Congress, Canada, 1913, Guide-book No. 3, p. 46.Google Scholar

page 514 note 3 Quoted in Iddings, Igneous Rocks, vol. li, p. 413, 1913.Google Scholar

page 514 note 4 Compiled from Rosenbusch, H., Elements der Gesteinslehre, 3rd ed., 1908Google Scholar, and Iddings, J. P., Igneous Rocks, vol. ii, 1913.Google Scholar

page 514 note 5 W. C. Brögger, loc. cit., p. 26.

page 514 note 6 A. Lacroix, loc. cit., p. 138.

page 514 note 7 Cf. Flett, J. S., loc. cit., p. 316; Bailey, E. B. in Geology of Glasgow District (Mem. Geol. Surv.), 1911, p. 138.Google Scholar

page 514 note 8 Cf. E. B. Bailey, loc. cit.

page 515 note 1 Bowen, N. L., Amer. Journ. Sci. [4], xxxviii, pp. 256–8, 1914.Google Scholar

page 515 note 2 Harker, A., Natural History of Igneous Rocks, 1908, pp. 317–20.Google Scholar

page 515 note 3 Becker, G. F., Amer. Journ. Sci. [4], iii, pp. 21–8, 1897.CrossRefGoogle Scholar

page 515 note 4 Pirsson, L. V., Bull. U.S. Geol. Surv., No. 237, pp. 187–90, 1905.Google Scholar

page 515 note 5 Washington, H. S., Bull. Geol. Soc. Amer., xi, pp. 409–10, 1900.Google Scholar

page 515 note 6 Bowen, N. L., Amer. Journ. Sci. [4], xxxix, pp. 175–90, 1915.CrossRefGoogle Scholar

page 516 note 1 W. C. Brögger, loc. cit.

page 516 note 2 Harker, A., The Naturalist, pp. 121–3, 1906.Google Scholar

page 517 note 1 Cf. Roth, J., Chemische Geologie, vol. iii, 1893, pp. 141–4;Google ScholarDewey, H. & Flett, J. S., Geol. Mag. [5], vol. viii, pp. 243–4, 1911.Google Scholar

page 518 note 1 Flett, J. S. in Geology of Newton Abbot (Mem. Geol. Surv.), 1913, p. 62.Google Scholar

page 518 note 2 Teall, J. J. H. in The Silurian Rocks of Scotland (Mem. Geol. Surv.), 1899, pp. 88–9.Google Scholar

page 518 note 3 Quoted in Rosenbusch, Elemente der Gesteinslehre, 3rd ed., 1910, p. 343.

page 519 note 1 Cf. Gardiner, M. I., Quart. Journ. Geol. Soc., xlvi, pp. 569–81, 1890; J. J. H. Teall, loc. cit., pp. 632–49.CrossRefGoogle Scholar

page 519 note 2 Summary of Progress of Geological Survey for 1907–8, p. 55; ibid. for 1908–9, p. 45.

page 519 note 3 Bailey, E. B., Geology of Glasgow District (Mem. Geol. Surv.), 1911, p. 113.Google Scholar

page 519 note 4 Tyrrell, G. W., Trans. Glasgow Geol. Soc., xiii, p. 311, 1909; Geol. Mag. [5], ix, pp. 129–31.Google Scholar