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| Keywords: The Quarterly journal of the Geological Society of London (14053290326).jpg 140 <br> J J H TEALL OX THE lIETAMOPvPHOSIS OF <br> Witli regard to the development of foliation the evidence is very <br> satisfactory The transition from a crystalline granular rock to a <br> perfectly typical schist may occur in the space of an inch The <br> specimen figured fig 1 was accidentally fractured and a little of <br> Pig 1 ” Block shoiving Passage from Granular to Foliated Structure <br> Three fourths natural size <br> Mechanisraus der Grebirgsbildung Band ii p 55 calls attention to the fact <br> that in a cleaved ci'vstalline limestone belonging to the Hoch ebirgskalk the <br> individual calcite grains are of unequal dimensions in the different directions <br> and have their longest diameters lying parallel to each other in the plane of <br> cleavage although in the uncleaved rock the crystalline grains are of nearly- <br> equal dimensions in the different directions He suggests that this is due to the <br> plastic deformation of the individual grains of calcite Lehmann Die <br> Entstehung der altkrystallinischen Schiefergesteine p 197 objects to this <br> view and calls attention to the evidences of fracture and crush occurring in the <br> rocks investigated by him The fact established by Heim requires an expla- <br> nation however and the most obvious one is the assumption that a molecular <br> rearrangement occurs in the calcite under the mechanical conditions which <br> determine the cleavage The following important questions remain to be <br> solved ” <br> Lender what conditions is the deformation of rocks accompanied b ' a crushing <br> of the individual constituents Under what conditions is it accompanied by <br> entire molecular rearrangement And lastly Under what conditions do these <br> two more or less opposite phases of metamorphism occur at one and the same <br> time <br> In the north-west of Scotland there are schists that have been formed by 37046984 114009 51125 Page 140 Text 41 http //www biodiversitylibrary org/page/37046984 1885 Geological Society of London NameFound Mechanisraus der Biodiversity Heritage Library The Quarterly journal of the Geological Society of London v 41 1885 Geology Periodicals Smithsonian Libraries bhl page 37046984 dc identifier http //biodiversitylibrary org/page/37046984 smithsonian libraries Information field Flickr posted date ISOdate 2014-04-30 Check categories 2015 August 26 CC-BY-2 0 BioDivLibrary https //flickr com/photos/61021753 N02/14053290326 2015-08-26 04 59 34 cc-by-2 0 PD-old-70-1923 The Quarterly journal of the Geological Society of London 1885 Photos uploaded from Flickr by Fæ using a script | ||||
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