R. E. Zartman
Ignatius T. Nkomo
J. S. Stacey
1968
<p><span>The leads </span>in<span> </span>feldspars<span> from the main Tertiary intrusive bodies </span>in<span> each of three </span>mining<span> regions </span>in<span> </span>Utah<span> are isotopically similar to the </span>lead<span> deposits immediately associated with them. These deposits are the largest and also the least radiogenic </span>in<span> each region, whereas the smaller deposits are more radiogenic. Throughout each region the 'ore leads appear to be mixtures </span>in<span> various proportions of </span>lead<span> derived from the intrusive magma and </span>a<span> radiogenic </span>lead<span> component derived from the upper crustal rocks through which the mineralizing fluids passed. Linear relationships are exhibited between the </span>lead<span> </span>isotope<span> ratios within each </span>mining<span> region, and these enable the ages of the upper crustal basement rocks to be determined. </span>A<span> simple tvo-stage model theory for the development of the </span>lead<span> ores yields the folloving data: Oquirrh Mountains region, t 1,650 4-150 m.y., p-Cottonwood-Park City region, t = 2,415 4-30 m.y., p- = 8.87. Tintlc region, t 2,075 4-30 m.y., Milford region, t 1 765 4-70 m.y., p-T ( Us ) = , = 8.83. An alternative "mixing" model is also proposed which requires only 1,650-m.y. and 2,400-m.y. events </span>in<span> these regions. </span>In<span> either case these ages confirm and supplement our present geochronological knowledge of the basement rocks of </span>Utah<span>. </span></p>
application/pdf
10.2113/gsecongeo.63.7.796
en
Society of Economic Geologists
A lead isotope study of galenas and selected feldspars from mining Districts in Utah
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