SALIENT FEATURES OF THE GEOLOGY OF OREGON 115 



vailing intrusives. In this connection Becker and W. D. Smith 

 have repeatedly called attention to the relation between the igneous 

 rocks of the Philippines and of Oregon. If we pass a great circle 

 along the axis of the Cascades we shall find that it will pass remark- 

 ably close to the Cordilleras of Japan and the Philippines, and it 

 is only to be expected that we would find this petrographic similar- 

 ity along such a great and persistent tectonic line. 



Definite figures as to the size of the intrusive batholiths in 

 Oregon are at present unavailable. In the Blue Mountains the 

 granodiorite is very prominent and attains elevations close to 

 10,000 feet and covers hundreds of square miles, while in the Cas- 

 cade region it is seen in one or two localities only, and these low 

 down and in very limited exposures. In the Siskiyou region (south- 

 west) also there are large masses of granodiorite. 



ECONOMIC GEOLOGY 



In 1867 the mineral production of Oregon, according to govern- 

 ment estimates at that time, was about twenty million dollars and 

 was practically, if not entirely, from gold placers. 



In 19 1 7 the value of the mineral products of the state which 

 were mined amounted to about $3,500,000. The year 19 18 saw 

 slightly less, owing to war conditions. A few years ago the pro- 

 duction was almost nil, so that we are now on the upgrade again, and 

 a substantial gold-mining industry largely from quartz lodes is 

 being established. 



On the mineral map (Fig. 3) are shown the principal mineral 

 localities in the state. It will be seen from a glance that the two 

 metalliferous districts are in the southwest and in the northeast, 

 the Siskiyou and Blue Mountains respectively. Baker County 

 produces the larger part of the gold of Oregon, and the Cornucopia 

 district is the leading district of that county. 



While there are many copper prospects, the most noteworthy 

 are those near Homestead on the Snake River, and those near 

 Waldo, twenty miles southwest of Grant's Pass, in the southwestern 

 part of the state. 



During the war there was a rather notable development of the 

 chromite industry in these two regions, and one manganese locality 



