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The Magnesian Group of Igneous Rocks1

Published online by Cambridge University Press:  01 May 2009

F. Dixey
Affiliation:
Government Geologist of Sierra Leone

Extract

Rocks rich in magnesium are abundantly developed in a certain few areas of the world, whereas they are rare or absent in the remaining areas. With reference to the abundance of magnesian rocks in Southern India, for example, Holland has stated:—

Type
Original Articles
Copyright
Copyright © Cambridge University Press 1921

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Footnotes

1

Paper read before Section C (Geology) of the British Association for the Advancement of Science, Edinburgh Meeting, September, 1921.

References

page 485 note 2 Charnockite Series of Igneous Rocks”: Mem. Geol. Surv. India, vol. xxviii, 1900, p. 192.Google Scholar

page 485 note 3 Lacroix, M. A., “Les Syénites Nephelinique de l'Archipel de Los”: Nouv. Arch, du Mus. d'Hist. Nat., Paris, 5éme Serie, Tome 3, 1911, p. 108.Google Scholar

page 485 note 4 Dixey, F., “The Norite of Sierra Leone”: Abs. Proc. Geol. Soc., 1921, p. 103.Google Scholar

page 485 note 5 Lacroix, M. A., “Sur l'Existence à la Côte d'lvoire d'une Série Petrographique comparable à celle de la Charnockite”: Comptes Bendus Hebdom. des Séances de l'cad. des Sci., 150, 1910, p. 18.Google Scholar

page 486 note 1 Dixey, F., Reps. Geol. Surv., Sierra Leone, 19191920.Google Scholar

page 486 note 2 Note.—An analogous arrangement has been suggested by Washington with regard to a small group of rocks, characterized by high content of titanium, which he proposes to distinguish as a “Titanium Province”. See H. S. Washington, “The Titaniferous Basalts of the Western Mediterranean”: Q.J.G.S., vol. lxiii, 1907, p. 69.Google Scholar

page 487 note 1 Op. cit., p. 196. See also Fermor below, p. 490.Google Scholar

page 487 note 2 See also Fermor on the ancient garnetiferous rocks of India, below, p. 490.Google Scholar

page 487 note 3 Metamorphic Rocks of Adelie Land”: Rep. Aust. Ant. Exped., vol. iii, 1918, pt. i, p. 13. See also below, p. 489.Google Scholar

page 487 note 4 In this connection it may be noted that Dr. J. W. Evans has recently postulated the formation of garnets, together with certain other minerals of small molecular volumes, in magmas crystallizing under conditions of high pressures and comparatively low temperatures. “The Origin of the Alkali Igneous Rocks”: Geol. Mag., Vol. LVII, 1920, p. 559. See also note below, p. 491, on garnets and “piezocrystallization”.Google Scholar

page 487 note 5 Op. cit., p. 197.Google Scholar

page 488 note 1 Lacroix, , op. oit., 1911.Google Scholar

page 488 note 2 Mem. Geol. Surv. India, vol. xxx, 1900, pt. ii.Google Scholar

page 488 note 3 Daly has commented upon the association of anorthositic and syenitic types both in the Adirondacks and in Western Norway. See Igneous Rocks and their Origin, 1914, p. 54.Google Scholar

page 488 note 4 Kolderup, C. F., Berg. Mus. Aarb., 1896, No. V; also 1903, No. 12.Google Scholar

page 488 note 5 Rosenbusch, , Elemente der Gesteinslehre, 1910, p. 187.Google Scholar

page 488 note 6 See Washington, H. S., “The Charnockite Series of Igneous Rocks”: Amer. Journ. Sci., 1916, p. 323. Also J. P. Iddings, Igneous Rocks, vol. ii, 1913, p. 511.CrossRefGoogle Scholar

page 488 note 7 Memoirs Geol. Surv. India.Google Scholar

page 488 note 8 See above, p. 486.Google Scholar

page 488 note 9 Bugge, C., Rep. 2nd Fram Exped., No. 22, 1910.Google Scholar

page 489 note 1 Iddings, J. P., Igneous Rocks, vol. ii, 1913. p. 358.Google Scholar

page 489 note 2 Rogers, G. S., Ann. X. Y. Ac. Sci., xxi, 1911, p. 11.Google Scholar

page 489 note 3 Watson, , Bull. Geol. Soc. Amer., 1915.Google Scholar

page 489 note 4 See Washington, H. S., op. cit. supra.Google Scholar

page 489 note 5 Tilley, C. E., “The Granite-Gneisses of Southern Eyre Peninsula (South Australia) and their Associated Amphibolites”: Q.J.G.S., vol. lxxvii, 1921, p. 75.CrossRefGoogle Scholar

page 489 note 6 Stillwell, F. L.. “The Metamorphic Rocks cf Adelie Land”: Rep. Aust. Ant. Exped., vol. iii, pt, i, 1918.Google Scholar

page 489 note 7 The North-Western Highlands of Scotland”: Mem. Geol. Surv. Great Britain, 1907.Google Scholar

page 489 note 8 Igneous Rocks and their Origin, 1914, p. 55.Google Scholar

page 489 note 9 Op. cit., p. 469.Google Scholar

page 489 note 10 See Daly, , Igneous Rocks and their Origin, 1914, p. 171.Google Scholar

page 490 note 1 Daly, , op. cit. Also L. L. Fermor, Rec. Geol. Surv. India, vol. xliii, 1913, p. 41.Google Scholar

page 490 note 2 Holland, T. H., “The Charnockite Series”: Mem. Geol. Surv: India, xxviii, 1900, p. 196.Google Scholar

page 490 note 3 Op. cit.Google Scholar

page 490 note 4 Preliminary Note on Garnet as a Geological Barometer and on an Infra-plutonic Zone in the Earth's Crust”: Rec. Geol Surv. India, vol. xliii, 1913. p. 41.Google Scholar

page 490 note 5 Cf. also Dr. J. W. Evans; see footnote on p. 487 above.Google Scholar

page 490 note 6 Id., p. 44.Google Scholar

page 491 note 1 See also Holland on garnets in ancient rocks of Southern India, above, p. 485. Moreover, E. Weinschenk has brought forward evidence to show that the garnets, as well as the granularity, of the central granitic gneisses of the Alps may be regarded as having been produced during the crystallization of a viscous magma under the operation of a powerful directed pressure (“piezo-crystallization”), and not by later metamorphism. Cong. Géol. Inter., C.R., viii, 1900, p. 326.Google Scholar

page 491 note 2 Op. cit. supra, p. 196.Google Scholar

page 491 note 3 Granularity cannot necessarily be regarded as evidence of metamorphism; many igneous rocks are known to possess well-developed granular texture as a result of disturbance of some kind during crystallization. See Weinschenk re “piezocrystallization”, op. cit. supra, and also F. Dixey, “The Norite of Sierra Leone”: Proc. Geol. Soc., 1921, p. 103.Google Scholar

page 491 note 4 Op. cit., p. 121.Google Scholar

page 491 note 5 Abs. Proc. Geol. Soc., 1921, p. 46.Google Scholar

page 492 note 1 Tilley, C. E., “The Granite Gneisses of Southern Eyre Peninsula (South Australia) and their Associated Amphibolites”: Q.J.G.S., vol. lxxvii, 1921. p. 75.CrossRefGoogle Scholar

page 492 note 2 Elemente der Gesteinslehre, 1910, p. 187.Google Scholar

page 492 note 3 The Charnockite Series”: Mem. Geol. Surv. India, vol. xxviii, 1900, p. 131.Google Scholar

page 493 note 1 Les Syénites Nepheliniques de l'Archipel de Los”: Nouv. Arch, du Mus. d'Hist. Nat., Paris, 5me Série, Tome 3, 1911, p. 108.Google Scholar

page 493 note 2 Some British Pillow-Lavas and Associated Rocks”: Geol. Mag., 1911.Google Scholar

page 493 note 3 See Daly, R. A., Igneous Rocks and their Origin, 1914, p. 340.Google Scholar

page 493 note 4 Wolff, F. v., Vulkanismus, i, 1914, p. 153.Google Scholar

page 493 note 5 The Charnockite Series of Igneous Rocks”: Amer. Journ. Sci., 1916, p. 323.Google Scholar