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III.—Inclusions in Some Volcanic Rocks

Published online by Cambridge University Press:  01 May 2009

J. Allan Thomson
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Extract

My attention was first drawn to this subject by the study of a remarkable crystal breccia, occurring at Kakanui, New Zealand, of which a description is given below. The only similar phenomena I could read of in the Colonial libraries at my disposal were those of the diamond pipes at Kimberley, described by Professors Carvill-Lewis, T. G. Bonney, and Miss Kaisin in this Magazine.2 Having since had the opportunity, thanks to the hospitality of Professor Lacroix, of studying in his laboratory at Paris, I found that the proper discussion of this subject comes under the study of the inclusions of volcanic rocks, of which he has given so admirable an account in his book “Les Enclaves des Roches volcaniques.”3 At his recommendation I collected some inclusions from the well-known dolerite of Portrush, and studied them under his guidance. The present paper consists of a discussion of rocks from these two localities, with descriptive notes on a few other inclusions that I have in my collection.

Two things stand out clearly from a cursoiy examination of this book, the frequency, almost the universality, of inclusions in igneous rocks, and the importance of the aid which they afford to the student of volcanic phenomena. Under these circumstances, it is remarkable how long this branch of study has escaped attention from. British geologists. Lacroix's useful nomenclature has not been adopted in our literature, although Phillips, Teall, Sollas, Harker, Judd,1 and others have paid considerable attention to some varieties of inclusion, and Harker has established a slightly different classificationof these phenomena.

Type
Original Articles
Information
Geological Magazine , Volume 4 , Issue 11 , November 1907 , pp. 490 - 500
Copyright
Copyright © Cambridge University Press 1907

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References

page 490 note 1 Sawyer, A. R., Report on the Geology and Mineral Resources of Prince Albert: Parliamentary Report, Cape Town, 1893.Google Scholar

page 490 note 2 Numerous scattered references to crystal tuffs occur in British petrological literature, and the subject is well presented by Sir A. Geikie in “The Ancient Volcanoes of Great Britain,” especially vol. i, p. 62, and vol. ii, p. 79, but the general paucity of information on this point in the standard textbooks is remarkable.

page 490 note 3 Lacroix, A.: “Les Enclaves des Roches volcaniques”: Macon, 1893.Google Scholar

page 491 note 1 For a discussion of the subject in 1893 and previous literature see Judd, Q.J.G.S., vol. xlix (1893), p. 176.

page 491 note 2 Eva½Ïλλs = different; ö6½µ=Similar; Yevv´=to beget.

page 491 note 3 Zirkel:, F. “Lehrbuch der Petrographie,” 2nd ed. (1893), vol. i, p. 794.Google Scholar

page 491 note 4 Doelter:, C. “Petrogenesis,” 1906, ch. vii, p. 101.CrossRefGoogle Scholar

page 491 note 5 Trans. Roy. Ir. Acad., vol. xxx (1894), p. 493.

page 491 note 6 Harker, A., “Igneous Rock Series and Mixed Igneous Rocks”: Journal of Geology, Chicago, 1900, p. 389.CrossRefGoogle Scholar

page 491 note 7 Harker, A. “The Tertiary Igneous Rocks of Skve”: Geol. Surv. Mem., 1904, p. 351.Google Scholar

page 492 note 1 Q.J.G.S., vol. xlii (1886), p. 71.

page 492 note 2 Lacroix has summed up his conclusions on this subject in a paper “E'tude sur le Metamorphisme de Contact des Eoches Volcaniques”: Memoires presented par divers savants a l'Académie des Sciences, tome xxxi (1894), No. 7.

page 492 note 3 See Laeroix, A. “Les Phénoméenes de contact de la Lherzolite et de quelques Ophites des Pyrénées”: Bull. Carte Geologique de la France, No. 42 (tome vi, 1895), ch. iii, p. 124.Google Scholar

page 493 note 1 Loc. cit., vol. ii, p. 299.

page 493 note 2 G. A J. Cole, “On Contact-Phenomena at the Junction of Lias and Dolerite at Portrush”: Proc. Roy. Ir. Acad., vol. xxvi, sect. B, No. 6, p. 62.

page 494 note 1 Loc. cit., p. 63.

page 494 note 2 “Les Enclaves des Bodies volcauiques,” p. 655.

page 495 note 1 Loc. cit., p. 59.

page 495 note 2 Loc. cit., p. 49.

page 495 note 3 “E'tude sur le Metamorphisme de Contact des Eoches Yolcaniques,” p. 47.

page 496 note 1 “Les Enclaves des Roches volcaniques,” p. 144.

page 496 note 2 Thomson, J. A. “The Gem Gravels of Kakanui“: Trans. Xew Zealand Institute, vol. xxxviii (1905), p. 481.Google Scholar

page 496 note 3 Q.J.G.S., vol. vi (1850), p. 324.

page 498 note 1 Loc. cit., p. 481.

page 499 note 1 Comptes Rendus viii International Geological Congress, 1900, p. 806.