MINERALS PRODUCED IN CONNECTION WITH INTRUSION. 719 



t 



(2) die Zone der Fleck-, Frucht- oder Knotenschiefer mit deutlich grober krys- 

 tallin entwickelter Schiefergrundmasse oder Knotenglimmerschief&r; 



(3) die Zone der Horn/else, speciell der weitaus vorwiegenden Andalusithom- 

 fdse. a 



In the Erzgebirge granite intrudes phyllite. Dalmar summarizes as 

 follows : 



Sonach lassen sich also innerhalb derfortschreitenden Reihe von Urnwandlungen, 

 welche die Ph} T llite im Contact mit den Granitstocken erlitten haben, folgende vier 

 Stadien unterscheiden: 



(1) Das Stadium der FrucJitscliiefer mit unveranderter Schiefermasse. 



(2) Das Stadium der Fruehtschiefer mit hrystallvnisch veranderter Schiefermasse. 



(3) Das Stadium der schieferigen Glimmerfelse. 



(4) Das Stadium der Andalusitglimmerfelse und Andalusithornfelse. 1 



In the Hartz granite has intruded the sedimentary rocks, and here 

 Lessen finds three contact zones. Says Lossen: 



Im Allgemeinen aber doch sehr wohl ausgepragte, concentrisch urn den Granit 

 verlaufende Steigerungszonen der nach dem Eruptivgestein hinwachsenden Umbil- 

 dung: die Aeussere Knotenschieferzone, die mittlere Hornfelszone und die innere 

 Zone der Glimmerschieferahnlichen Hornfelse gegliedert werden." 



Near Monzoni in the Predazzo district of Tyrol is a set of zones charac- 

 terized in passing from the intrusive by a succession of garnet, augite, 

 serpentine, and bracked This is a very interesting case, because the first 

 two minerals are those which ordinarily develop in the zone of anamorphism, 

 whereas the third and fourth minerals commonly develops in the zone of 

 katamorphism. So far as I know this is unique. It suggests, if all these 

 minerals be original, that near the intrusive mass the pressure was sufficient 

 to require reactions giving decrease in volume, and therefore the condi- 

 tions were those of the zone of anamorphism; whereas at a greater distance 

 the pressure was not so great but that reactions could take place with 

 increase of volume, and therefore the conditions were those of the zone of 

 katamorphism. However, before this can be regarded as established it 

 must be shown that the serpentine and brucite developed simultaneously 

 with the garnet and augite, and are not later alteration products. 



« Rosenbuseh, cit., pp. 177-178. 



&Dalmer, K., Erlauterungen zur geologischen Specialkarte des Konigreichs Sachsen: Section 

 Kirchberg: Leipzig, 1884, Blatt 125, pp. 26-27. 



<" Lossen, K. A., Erlauterungen zur geologischen Specialkarte von Preussen und den Thuringisehen 

 Staaten: Blatt Harzgerode, Berlin, 1882, p. 45. 



''Teller, F., and John, C. von, Geologisch-petrographisehe Beitriige zur Kenntniss der dioritischen 

 Gesteine von Klausen in Sudtyrol: Jahrbuch k.-k. geol. Eeichsanstalt, 1882, XXXII, 589-684. 

 Irving, A., Metamorphism of rocks: Longmans, Green & Co., London, 1889, p. 80. 



