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II.—On some Epi-diorites of N.W. Ireland

Published online by Cambridge University Press:  01 May 2009

J. Shearson Hyland
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Extract

In an Appendix to the Explanatory Memoir on Sheet 17 of the Map of the Geological Survey of Ireland (Dublin, 1889), I have furnished a description of the petrographical characters of the Epi-diorites of the district. Some of the facts elicited by the examination of the rocks are sufficiently interesting to deserve a wider circulation.

Type
Original Articles
Information
Geological Magazine , Volume 7 , Issue 5 , May 1890 , pp. 205 - 208
Copyright
Copyright © Cambridge University Press 1890

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References

page 205 note 1 Read before the Royal Geological Society of Ireland, 10th February, 1890.

page 205 note 2 The dark bluish-grey mica-schist is seen under the microscope to consist of a plexus of light-green, uniaxial mica and minute grains of quartz. Calcite, hematite, tourmaline, and rutile are also present. Strain-slip cleavage is well developed. Iron-pyrites is to be observed macroscopically, also rutile according to Giesecke.

page 205 note 3 Prof. Hull in Memoir to Sheet 17, p. 7.

page 205 note 4 Teall, “The Metamorphosis of Dolerite into Hornblende-schist,” Q.J.G.S. 1885, p, 139, and “The Metamorphosis of the Lizard Gabbros,” GEOL. MAG. Dec. III. Vol. I. p. 487.

page 206 note 1 Uebersicht ueber den Schichtenaufbau Ostthüringens, Abhandl. zur geol. Spezialkarte von Preussen u. d. Thüring. Staaten, Band V. Heft 4, p. 83.

page 206 note 2 Tremolite occurs in the district comprised in Sheet 17, viz. near Curley Hill, Co. Tyrone, but in limestone. (Giesecke, C. L., Minerals of the Koyal Dublin Society, to which is added an Irish Mineralogy, Dublin, 1832, p. 227.Google Scholar)

page 206 note 3 For crystallographic details, see Memoir, Sh. 17, pp. 35 and 36. The occurrence of zoisite in this district, at Holly Hill, near Strabaue, Co. Tyrone, was known to Portlock (Report of the Geology of the Co. Londonderry, etc., Dublin, 1843, p. 209); also to Giesecke (loc. cit. p. 208).

page 206 note 4 Pogg. Ann. d Ph. 1833, 1 St. p. 103. “Immer aber haben sie (Uralite) sich nach den gemachten Erfahrungen nur in den Grünsteinen gefunden in welchen Albit oder Feldspath niclit vorkommen oder wenigstens nicht deutlich ausgeschieden vorkommen; mit der Bildung dieser Mineralien scheint die Bildung des Uralits aufzuhören und statt dessen Hornblende an seine Stelle zu treten.” The term “uralite” is used in a strict sense as applying to a mineral possessing the outer form of augite and the cleavage planes of bornblende (V. Pogg. Ann. 1831, xxii. p. 321; and Jahrb. f. Min. 1832, p. 237).

page 206 note 5 “Reise nach d. Ural,” Band II. 575.

page 207 note 1 Judd, “On the Processes by which a Plagioclase Felspar is converted into a Scapolite,” Min. Mag. viii. No. 39, p. 186 (13).

page 207 note 2 Grünsteine des Harzes,” Göttingen, 1869.

page 207 note 3 “Studien an metamorphischen Eruptiv- und Sedimentgest,” preuss, Jahrbueh d. k.. geol. Landesanstalt für 1883. Berlin, pp. 619–640.Google Scholar Also, Erläuterungen zur geol. von Preussen, Specialkarte, Blatt Wippra, 1883, pp. 50 and 83Google Scholar.

page 207 note 4 “Diepaläolithischen Eruptivgesteinedes Fichtelgebirges,” München, 1874, p. 14.

page 207 note 5 British Petrography, p. 155.