Teaching Atlas of Nuclear Medicine - Tapa blanda

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1889 edition. Excerpt: ... contact-metamorphism (Ibid. pp. 407-10,) seem to run fairly parallel with those of such foreign workers as are cited in this work, (pp. 81-82). He notes the developement of new minerals (quartz, mica, tourmaline) in the contact-zone of the slates, and the conversion of previously-cleaved clay-slate into a crystalline foliated rock (mica-schist, tourmaline-schist), the arrangement of the new minerals appearing to follow the original lamination of the fine sedimentary material. The intruded granite is also schorlaceous. He also describes a case of developement of crystals of orthoclase felspar, as well as quartz and mica, in the altered Silurian slates of Wexford, in immediate contiguity with the granite (Ibid. fig. iij, thus giving us a gneiss as an alteration-product. Yet in spite of such local phases of metamorphism in the contact-zone, the distinction between the granite and the metamorphosed rocks seems to him absolute and incontestable. 4. He notes (Ibid, p. 412 that outside the contact-zone of schists, "indurated slates traversed by quartz-veins form a wide zone, and beyond these the rock is ordinary clay-slate." With this we may compare Lehmann's example of Knotenschiefer ( Allkr. Gest. Tafel xxviii, fig. 1) which that author describes as showing "the splitting of the original slate visibly into small bits, between which quartz and biotite have separated-out, the secondary quartz (Neubildungen) forming in places wider qnartz-layers." All this, in the one case and in the other, looks very like the kind of work we should expect to be done in the third ataye of contact-metamorphism supra, pp. 82-83). The alteration described by Allport (loc. cit.) of crystalline minerals into 'chloritic pseudomorphs' consisting of...