PETROLOGICAL ABSTRACTS AND REVIEWS 321 



2. Dynamic metamorphism. 



a) D5aiamo-hydral or slaty ( ?) metamorphism (low temperature) . 

 h) Dynamo-thermal or friction ( ?) metamorphism (high temper- 

 ature) 



3. Dynamo-static metamorphism. 

 B. Local metamorphism. 



1. Contact metamorphism. 



2. Load-contact metamorphism. 



Dresser, John A. "Granitic Segregations in the Serpentine 

 Series of Quebec," Trans. Roy. Soc. Canada, Vol. XIV (192 1), 

 PP- 7-13- 



Granitic dikes are limited to the peridotite-serpentine area of this 

 region, and are believed to be local fillings of contraction cracks in the 

 cooling peridotite by part of the still liquid acidic magmatic residues. 

 Larger irregular masses are beheved to be residual segregations from the 

 magma of the peridotite and to have been formed in situ by differen- 

 tiation. 



Du ToiT, Alex. L. "The Karoo Dolerites of South Africa: a 

 Study in Hypabyssal Injection," Trans. Geol. Soc. South 

 Africa, Vol. XXIII (1920), pp. 1-42. Figs. 5. 



The uneroded remnants of strata invaded by these South African 

 "dolerites" (British usage) cover fully 220,000 square miles, and fully 

 half as much more has been removed. The rocks are composed of 

 labradorite and augite, with or without olivine, and are of ophitic tex- 

 ture. They are almost exclusively confined to beds of the Karoo system, 

 and date from the Rhaetic or Lias, Middle Jurassic at latest. The 

 intrusions form intersecting dikes and a series of sheets, one above the 

 other. The latter are practically horizontal and vary in thickness from 

 100 to 3000 feet, although in some cases still thicker sheets are found. 

 Thus the curved sheets of the Queenstown district attain a thickness of 

 fully 1,500 feet and cover some 40 square miles, and the Ingeli mass is 

 over 3,000 feet in thickness. Metamorphic action is practically confined 

 to baking, of the sandstones and shales into quartzite and hornstone. 

 With the exception of a few isolated and small-scale cases, no signs of 

 assimilation of the strata by the invading magma were found. The 

 sheets, with the exception of decrease in size of grain at the margins, are 

 generally uniform in texture. In a few localities, enstatite partially or 



