Report on the Geology of a Portion of the Laurentian Area Lying to the North of the Island of Montreal

Report on the Geology of a Portion of the Laurentian Area Lying to the North of the Island of Montreal

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1896 edition. Excerpt: ...anorthosite, which occurs not only in Canada, but in Norway, Russia and other countries, constitutes a well defined rock type, and one which, not only on account of its peculiar composition, but also owing to the enormous size of the masses in which it occurs and the constancy of its character, occupies an important position in the petrographical series. The anorthosite of this Morin area exhibits a great variation in structure and colour and in certain places even a considerable variation in composition, but is in mineralogical composition a gabbro or norite free from olivine and very rich in plagioclase. Hand specimens from about fifty different places in the area have been sliced and microscopically examined, and the following description of thefe rocks is based on the results thus obtained. The number of minerals which the rock contains is not large, the variations in composition resulting principally from their irregular distribution. The following minerals have been observed in the rock: --Plagioclase Muscovite and Paragonite Epidote Augite Bastite Zoisite Hypersthene Chlorite Garnet Ilmenite Quartz Zircon Orthoclase Magnetite Spinel Hornblende Apatite Biotite, Calcite Of these plagioclase, augite, hypersthene and ilmenite are by far the most important. As above mentioned, Hunt adopted the name anorthosite for these rocks on account of the great preponderance in them of plagioclase or anorthose. He considered the type which contains only felspar as the true anorthosite and estimated that three-fourths of the anorthosites in the Dominion did not contain over five per cent of other minerals. Like the other constituents of the rock, the plagioclase is quite fresh, showing but very rarely any traces of decomposition, and when it is not..show more

Product details

  • Paperback | 74 pages
  • 189 x 246 x 4mm | 150g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236610601
  • 9781236610607