00747nam a2200193 a 450000500170000000800410001703500150005804100070007305000240008010000320010424501290013626000490026530000140031444000710032850000580039965000120045765000440046971000400051320260817161346.0                                          a.b100504980 aEN  aQE75 P9 no. 1049 -B  aArmbrustmacher, Theodore J. 0aAbundance and distribution of thorium in the carbonatite stock at Iron Hill,bPowderhorn District, Gunnison County, Colorado  aWashington :bU. S. Govt. Print. Off.,c1980  aiii, 11 p 0aUnited States. Geological Survey. Professional paper ;vno. 1049-B  aPrepared in cooperation with the Department of Energy 0aThorium 0aCarbonatitesxColoradoxGunnison County  aUnited States. Department of Energy