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V.—The Petrographical Characters of the Darjíling Gneiss

Published online by Cambridge University Press:  01 May 2009

John Parkinson
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Extract

Well known as Darjiling is to nearly every stray traveller in India, the solid geology of the district has been left almost (I believe quite) untouched since the publication of Mallet's paper in 1874. There the Darjíling gneiss was described as the metamorphosed representative of the sedimentary Gondwana rocks of the south, and has so remained, albeit under protest, for a disclaiming paragraph appears in the Manual of the Geology of India. In the report of the Committee on the recent landslip at Darjíling it is stated that the rock of the country consists of “a well foliated and banded biotite gneiss with occasional lenses and deformed veins of granitic rock”; moreover, that “the foliation planes are often highly contorted”; and Mallet defines it as true gneiss “passing into mica schist or an intermediate variety.” These descriptions are meagre, and it is hoped that the following notes on specimens collected by the author may not be superfluous.

Type
Original Articles
Information
Geological Magazine , Volume 9 , Issue 1 , January 1902 , pp. 30 - 35
Copyright
Copyright © Cambridge University Press 1902

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References

page 30 note 2 Mem. Geol. Surv. Ind., 1874, vol. xi, pt. 1.Google Scholar

page 30 note 3 Geology of India, 2nd ed., p. 76.Google Scholar

page 30 note 4 Report of the Committee on the Landslip at Darjeeling, September, 1899; published October, 1899.

page 31 note 1 By this term is meant the thread-like intergrowth of quartz in felspar. The ranching threads are grouped often in a kind of bunch, not uncommonly radiating rom a point. In the examples I have met with I believe it to be an original tructure.

page 31 note 2 This rock differs in appearance from the others that I collected. The specimen s browner in colour, the flakes of mica more conspicuous, and the foliation less arked.

page 33 note 1 Occasionally ·02 inch long. The slide contains a little augite.

page 35 note 1 See Mr.Teall's Pres, J. J. H.. Address to Geol. Assoc., Proc. Geol. Assoc., 1899, vol. xvi, pp. 72, 73.Google Scholar

page 35 note 2 See paper by Bonney, Canon T. G., Quart. Journ. Geol. Soc., 1891, vol. xlvii, p. 105.Google Scholar