GEOLOGY OF WEST COAST REGION OF UNITED STATES 

 lies the desert region of California, which presents 

 scores of irregular ranges, half buried in the sur- 

 rounding mantles of desert debris. Many of these 

 ranges contain small granitic masses which intrude 

 the upturned Palaeozoic strata. Each of these small 

 intrusives has its "metallic aureole," or boundary 

 zone, in which deposits of gold, copper, silver, and 

 iron, with subordinate lead and zinc, are developed. 

 Near Randsburg, Kern County, tungsten and gold- 

 bearing veins of importance occur in genetic rela- 

 tion to one of these small granitic masses. This 

 complex group belongs to the general type of Ari- 

 zona contact deposits. While no deposit of magni- 

 tude has been developed in California, this type is 

 destined to produce a larger proportion of the min- 

 eral wealth of the State than it has up to the present. 

 In Oregon the mineral regions are confined^ to 

 two small areas, one already mentioned lying im- 

 mediately north of California and containing the 

 continuation of the California gold belt. The second 

 area appears in the Blue Mountains in the north- 

 eastern portion of the State. Here a number of 

 intrusive masses occur, similar in age and type 

 to those mentioned for southeastern California, and 

 are bordered by groups of gold veins best known 

 in the Cracker Creek district and the adjacent min- 

 ing districts of Baker County. The rest of the State 

 is either covered by the great Tertiary lava flows 

 already mentioned, or near the coast r>y the later 

 Tertiary sedimentary rocks, which contain few me- 

 tallic deposits in this State. Similarly the southern 

 half of Washington and the Olympic peninsula are 

 either covered by lavas or contain Cretaceous and 

 Tertiary sedimentary rocks without important de- 

 posits of metals. The Cascade Ranges and the strip 

 of country adjacent to the Canadian boundary line 

 in the eastern part of the State, however, contain 

 many ore deposits of various types, especially in 

 Ferry, Stevens and Okanogan counties. All tnese 

 deposits lie in or near granitic intrusives (granodio- 

 rite) , which are probably related to the great Idaho 

 batholith. 



In addition to copper and nickel mentioned 

 above, the mineral products of the older metamor- 

 phosed rocks of the Coast Ranges and of the in- 

 trusive serpentines include manganese, occurring in 

 small amounts in bedded cherts; chromite occurring 

 as lenses in the serpentine; magnesite, found in large 

 amounts, but as yet only slightly developed; talc 

 and soapstone. We also must include here the gem 

 mineral benitoite, which not only has great beauty 

 of color and crystal form, but also is the only 



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