768 A TREATISE ON METAMOEPHISM. 



As typical cases of sedimentary formations altered in tli3 intermediate 

 belt may be mentioned the Wewe and Siamo slates of the Lower Marquette 

 series, the Goodrich quartzite, and the eastern half of the Michigamme 

 formation of the Upper Marquette series, all in the Marquette district of 

 Michigan." Within these formations almost every one of the multifarious 

 reactions described, both within the zone of katamorphism and within the 

 zone of anamorphism, are beautifully illustrated. Indeed, it was a study of 

 these formations which first suggested to me the idea of a combination of 

 the phenomena of different alterations near the surface and at depth, and 

 the very great difference in the alterations which often occur at the same 

 depth under mass-static conditions and under mass-dynamic conditions. 



In Calaveras Creek, a short distance below Calaveras Valley, south of 

 San Francisco, in the Coast Ranges of California, may be seen all stages of 

 transition between a brecciated igneous rock and a schist. The first 

 was deformed under the conditions of spaced fractures. The second was 

 deformed by granulation and recrystallization. ( In passing from the breccia 

 to the schist one first finds about the blocks of igneous rock which have 

 their characteristic textures mere films of schist. Farther toward the schist 

 is found an intermediate stage in which unmashed blocks lie in a schistose 

 background or matrix. But a short distance from this place is the com- 

 pletely altered schist, in which no unmashed fragments remain. Every stage 

 of the transition is seen. The alterations within the blocks are those of the 

 zone of katamorphism. (See pp. 160-167, 187-191, 599-602.) Within 

 the films and layers of schists constituting the matrix in which the blocks 

 rest and in the main mass of schist the alterations are those of the zone 

 of anamorphism. (See pp. 167-170, 187-191, 657-659.) 



These cases of the combination of the phenomena of metamorphism of 

 the zone of katamorphism and those of the zone of anamorphism are but 

 typical of almost innumerable illustrations. The phenomena in -Any one 

 case are very complex and intricate. Detailed consideration of any single 

 instance would require much space, and it is } r et too early to attempt to 

 classify the different cases of various combinations of the alterations of the 

 zones of anamorphism and katamorphism. 



°Van Hise, C. K,., and Bayley, W. S., The Marquette iron-bearing district of Michigan: Mon. U. S. 

 Geol. Survey, vol. 28, 1897, pp. 1-608. 



