NOTES
Feb., 1949
743
TABLE I COMPARISON O F AGEWITH Description of sample
Quartz, Cornucopia formation Soda feldspar
Location from which obtained
Cornucopia, N. E. Oregon
Ohanepecosh Hot Springs, Washington Potash feldspar, Cornucopia, N. E. Oregon Cornucopia formation Bostonite Marblehead, Massachusetts Granite, Silver Silver Plume, Colorado Plume Formation Granite Sudbury, Ont. Granite gneiss
Sudbury, Ont.
THE He cc./g.'at S. T.P.
RATIOA/K
IN
A cc./gI a t S. T.P.
ROCKS K, %
G. ats, A G. ats. K
Approximate age in millions of years
0,027 8.4 x 10-4 10-4
0.43
0.19 X lo-*
3.25 X lo-'
12.8
lo-'
0.81 X lo-'
2.08
1.4 X
1.91
100 (Late Mesozoic) 7 . 7 x IO-' 30 (Tertiary) 4.4 x lo-' 100 (Late Mesozoic) 300 6 . 8 X 10-8 (Carboniferous) 1.3 X 10-6 9403
10-4
3.33
2.4
5 . 2 X IO-'
1.05
8 . 6 X 10-6
0,022 X 0.062
x
