R. J. Knight C.J. Allegre M. Tatsumoto 1973 <div class="panel-pane pane-highwire-panel-tabs-container article__body"><div class="pane-content"><div id="panels-ajax-tab-container-highwire_article_tabs" class="panels-ajax-tab-container" data-panels-ajax-tab-preloaded="jnl_sci_tab_art"><div class="panels-ajax-tab-wrap-jnl_sci_tab_art"><div class="panel-display panel-1col clearfix"><div class="panel-panel panel-col"><div><div class="panel-pane pane-highwire-markup"><div class="pane-content"><div class="highwire-markup"><div id="content-block-markup" data-highwire-cite-ref-tooltip-instance="highwire_reflinks_tooltip" data-highwire-glossary-tooltip-instance="highwire_reflinks_tooltip"><div class="article abstract-view "><div id="abstract-1" class="section abstract"><p id="p-1">Measurements of the lead isotopic composition and the uranium, thorium, and lead concentrations in meteorites were made in order to obtain more precise radiometric ages of these members of the solar system. The newly determined value of the lead isotopic composition of Canyon Diablo troilite is as follows:<span>&nbsp;</span>²⁰⁶Pb/²⁰⁴Pb = 9.307,<span>&nbsp;</span>²⁰⁷Pb/^2O4Pb = 10.294, and<span>&nbsp;</span>²⁰⁸Pb/²⁰⁴Pb = 29.476. The leads of Angra dos Reis, Sioux County, and Nuevo Laredo achondrites are very radiogenic, the<span>&nbsp;</span>²⁰⁶Pb/²⁰⁴Pb values are about 200, and the uranium-thorium-lead systems are nearly concordant. The ages of the meteorites as calculated from a single-stage<span>&nbsp;</span>²⁰⁷Pb/²⁰⁶Pb isochron based on the newly determined primordial lead value and the newly reported<span>&nbsp;</span>²³⁵U and<span>&nbsp;</span>⁸³⁸U decay constants, are 4.528 x 10⁹<span>&nbsp;</span>years for Sioux County and Nuevo Laredo and 4.555 x 10⁹<span>&nbsp;</span>years for Angra dos Reis. When calculated with the uranium decay constants used by Patterson, these ages are 4.593 x 10⁹<span>&nbsp;</span>years and 4.620 x 10⁹<span>&nbsp;</span>years, respectively, and are therefore 40 to 70 x 10⁶<span>&nbsp;</span>years older than the 4.55 x 10⁹<span>&nbsp;</span>years age Patterson reported. The age difference of 27 x 10⁶<span>&nbsp;</span>years between Angra dos Reis and the other two meteorites is compatible with the difference between the initial<span>&nbsp;</span>⁸⁷Sr/⁸⁶Sr ratio of Angra dos Reis and that of seven basaltic achondrites observed by Papanastassiou and Wasserburg. The time difference is also comparable to that determined by<span>&nbsp;</span>¹²⁹1-¹²⁹Xe chronology. The ages of ordinary chondrites (H5 and L6) range from 4.52 to 4.57 x 10⁹<span>&nbsp;</span>years, and, here too, time differences in the formation of the parent bodies or later metamorphic events are indicated. Carbonaceous chondrites(C2 and C3) appear to contain younger lead components.</p></div></div><span id="related-urls"></span></div></div></div></div></div></div></div></div></div></div></div> application/pdf 10.1126/science.180.4092.1279 en AAAS Time differences in the formation of meteorites as determined from the ratio of lead-207 to lead-206 article