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Metasomatism associated with the greenstone-hornfelses of Kenidjack and Botallack, Cornwall

Published online by Cambridge University Press:  14 March 2018

C. E. Tilley
C. E. Tilley*
Affiliation:
University of Cambridge
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Extract

In a paper entitled 'Hornfelses from Kenidjack, Cornwall' 1 the nature and origin of the rock types characterized by anthophyllite and cummingtonite occurring in the aureole of the Land's End granite were discussed.

Since these rocks were 'investigated in 1928 the writer has extended his study of them both in the field and in the laboratory, with the result that further light on the origin of these rock types has been obtained. It is the purpose of these notes to examine in more detail the evidence which is considered to add to their understanding. In the Kenidiack paper the petrography of the rocks was described at some length and in the present paper petrographic data will be given only in so far as they supplement the previous account, which may be consulted for a detailed statement.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 24 , Issue 151 , December 1935 , pp. 181 - 202
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1935

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References

page 181 note 1 Tilley, C. E. and Flett, J. S., Summ. Progr. Geol. Surv. Great Britain, 1930, for 1929, pt. 2, pp. 24-41,Google Scholar hereafter referred to as the Kenidjack paper. [M.A. 4-402.]

page 182 note 1 Allport, S., Quart. Journ. Geol. Soc. London, 1876, vol. 32, p. 407.CrossRefGoogle Scholar

page 183 note 1 Phillips, J. A., Quart. Journ. Geol. Soc. London, 1876, vol. 32, p. 167.CrossRefGoogle Scholar

page 188 note 1 Hall, A. L. and Molengraaff, G. A. F. (Verh. Akad. Wetenschappen, Amsterdam, 1925, vol. 24, no. 3, pp. 128-131)Google Scholar have recorded the association cordierite. actinolitic hornblende in amygdules and in the body of a basic igneous rock-the basal amygdaloid of the Vredefort area. Some doubt may be expressed on this reported co-existence of cordierite and hornblende, and it may be questioned whether a cordierite-cummingtonite or anthophyllite association is not indicated. A further genetic study of this unusual occurrence would be of interest.

page 191 note 1 Alderman, A. R., Min. Mag., 1935, vol. 24, p. 42.CrossRefGoogle Scholar

page 192 note 1 Tilley, C. E., Min. Mag., 1926, vol. 21, p. 47.CrossRefGoogle Scholar

page 193 note 1 G. P. Merrill, Rocks, rock weathering and soils. 1906.

page 193 note 2 The analysis of the weathered product of the Rowley Regis dolerite given by Warth, H. (Geol. Mag., 1905, p. 21)CrossRefGoogle Scholar is in some ways exceptional. The analyses of the fresh rock (I) and the weathered top (II) are given as follows : Here the chief contrast between the fresh and weathered basalt is the loss of CaO and Na2O, enrichment in K20, and gain in water. MgO has suffered little change. The unusual character of this analysis merits further investigation of the weathering products of the Rowley Regis dolerite.

page 200 note 1 Cooke, H. C., Summ. Report Geol. Surv. Canada, 1925, part C, p. 41 Google Scholar; Walker, T. L., Univ. of Toronto Studies, Geol. Series, 1930, no. 29, p. 9 Google Scholar [M.A. 4-401] ; Cooke, H. C., James, W. F., and Mawdsley, J. B., Mere. Geol. Surv. Canada, 1931, no. 166, pp. 206-218.Google Scholar

page 201 note 1 Brögger, W. C., Vid..Selsk. Skrifter, I. Math. Naturv. KI. 1934, no. 1, p. 225.Google Scholar

page 201 note 2 Johansson, H. E., Geol. För. Förh., 1910, vol. 32,, p. 239 CrossRefGoogle Scholar ; Eskola, P., Bull. Comm. Géol. Finlande, 1914, no 40 Google Scholar; Geijer, P., Årsbok Sveriges Geol. Unders.. 1916, vol. 10, no. 1 Google Scholar, and Kungl. Kommerskoll. beskriv, mineralfyndig., 1923, no. 1.