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III.—On the Lower Silurian Felsites of the South-East of Ireland1

Published online by Cambridge University Press:  01 May 2009

Frederick H. Hatch
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Extract

The felsites of the south-east of Ireland are shown on the maps, of the Geological Survey to extend over considerable areas in counties Wicklow, Wexford and Waterford. Like the Welsh felsites they are contemporaneous with Lower Silurian (Ordovician) strata, and were probably erupted on an old sea-bottom. They are accompanied by abundant deposits of tuffs and breccias, the component fragments of which consist mainly of felsite.

Type
Original Articles
Information
Geological Magazine , Volume 6 , Issue 12 , December 1889 , pp. 545 - 549
Copyright
Copyright © Cambridge University Press 1889

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Footnotes

1

Read at the Newcastle Meeting of the British Association, Sept. 13th, 1889.

References

page 545 note 2 Sheets 130, 139, 148, 149, 158, 167, 168, 169, 178, and 179.

page 545 note 3 Geol. Mag. 1889, p. 70.Google Scholar

page 545 note 4 Should the soda be in but slight excess of the potash, the rock might be termed a soda-potash-felsite. The term keratophyre (originally suggested by Gümbel) has been applied by Lossen to a rather indefinite group which includes rocks similar in character to those in Group III. The term soda-felsite appears more applicable to these rocks.

page 546 note 1 The whole of the potash has been calculated as orthoclase from the formula K2O. Al2O3. (SiO2)6; and the soda as albite from the formula Na2O. Al2O3. (SiO2)6.

page 546 note 2 See also three analyses of felsites from the counties of Wicklow, Wexford, and Waterford by the RevHaughton, S. (Trans. Roy. Irish Acad. vol. xxiii. part ii. 1859, p. 615).Google Scholar

page 546 note 3 See also two analyses of soda-felsites from the Waterford coast by the late Phillips, J. A. (Phil. Mag. 1870, vol. xxxix. p. 12;Google Scholar Geol. Mag. 06, 1889, p. 288),Google Scholar and an analysis of a Wicklow soda-felsite by the author (Geol.Mag. 02. 1889, p. 70).Google Scholar

page 548 note 1 Mikros. Physiog. vol. i. (1885), p. 550.Google Scholar

page 548 note 2 Zeitsch. f. Kryst vol. viii. (1884), p. 125.Google Scholar

page 548 note 3 Die Silurischen Etagen 2 and 3, 1882, p. 261.Google Scholar

page 548 note 4 Min. Mag. vol. vii. (1887), p. 131.Google Scholar

page 549 note 1 Jahrbuch d. k. Preus. Geol. Landesanst. für das Jahr 1884 (1885), p. xxxii.

page 549 note 2 Trans. Roy. Irish Acad. vol. xxii. pt. ii. (1859), p. 609.Google Scholar

page 549 note 3 Mikros. Phys. vol. ii. 1887, p. 528.Google Scholar

page 549 note 4 Nothing of the nature of microfelsite (in Rosenbusch's sense) has been observed by me during the examination of these rocks.

page 549 note 5 On the Pitchstones and Perlites of the Lower Silurian District of Shropshire, Q.J.G.S, vol. xxxiii. (1877), p. 449.Google Scholar

page 549 note 6 On Perlitic and Spherulitic Structures in the Lavas of the Glyder Fawr, N. Wales Q.J.G.S. 1879, p. 508;Google Scholar and in Memoir of Geol. Survey on the Felsitic Lavas of England and Wales.