CHICHAGOF COVE 
8l 
color than the mass. The rocks are much altered, the groundmass 
largely to chlorite and bluish fibrous hornblende, the hornblende 
phenocrysts to the same, with separation of magnetite grains on the 
borders. The feldspar is cloudy with kaolin and indeterminable. 
Some of the dark fragments prove to be aggregates of tourmaline 
needles, others are more basic portions of the diorite-porphyrite. 
These are apparently friction breccias formed near the border of the 
intrusion. 
The Dikes 
Dikes cutting the sedimentary rocks are found in all 
parts of the area studied but are especially numerous in 
the vicinity of the laccolithic mass. They are never of 
very great dimensions; a few reach a thickness of about 
twenty feet, but those from four to ten feet in width are 
most frequent. Their linear extent is rarely more than a 
few hundred feet, although one was found which could be 
traced continuously about half a mile. The dike rocks, 
being in general much more resistant than the shales and 
sandstones which they traverse, stand up in bold walls, 
StepovaXBeds DiotltCLparghyrltO Stepovak Bed® 
FIG. l8. DIAGRAMMATIC SECTION ON SOUTH FACE OF CHICHAGOF PEAK. 
sometimes fifteen or twenty feet high, as shown in the 
annexed sketch (fig. x8) ; and on the shore they generally 
stand out as prominent cliffs. 
The dikes have not been indicated on the sketch map. 
In a general way they are radial to the dome-shaped uplift 
of Chichagof Peak, and hence for the most part cut across 
the strike of the sedimentary beds at high angles. This 
was strikingly the case with the dozen or more dikes 
found along the shore of West Cove, all of which are 
