D. Gottfried R.I. Tilling L. P. Greenland 1974 <div id="abstracts" class="Abstracts u-font-serif"><div id="aep-abstract-id5" class="abstract author"><div id="aep-abstract-sec-id6"><p id="simple-para.0010">Neutron-activation determinations of Ir in rocks of the Southern California and Boulder (Montana) batholiths show that the Ir content is low and variable in both batholiths, extending over 1 to 2 orders of magnitude and having a combined median of 0.006 ppb Ir. The data suggest that the calc-alkalic Boulder batholith (0.002–0.5 ppb Ir, median 0.007) may be slightly enriched in Ir relative to the calcic Southern California batholith (&lt; 0.001–0.12 ppb Ir, median 0.005). No conspicuous relationship between Ir content and differentiation parameters is evident; however, the Boulder batholith rocks do show a slight tendency to concentrate Ir in the more mafic rocks. Our results in conjunction with previous analyses of mafic rocks leads to a crustal-abundance estimate of 0.03 ppb Ir</p></div></div></div> application/pdf 10.1016/0009-2541(74)90101-6 en Elsevier Iridium in some calcic and calc-alkalic batholithic rocks of the western United States article