Abundance and distribution of uranium and thorium in the northern units of the Leinster granite, Ireland

Abstract

SummaryAbundance data, determined by epithermal neutron activation analysis, are reported for radioelements in the northern units of the Leinster granite. Compared to similar data for silicic igneous rocks and British Caledonian granites, the Leinster granite shows normal U and K contents but is low in Th. Inter-element correlations and fission-track results suggest that most Th and up to 40% of the U is bound in resistate accessory phases (zircon, sphene, apatite), but that the bulk of U is associated with late-stage alteration products and is located at interstitial labile sites within the host-rock matrix. Mobilization of U located at such sites in the Leinster granite by hydrothermal leaching could lead to redeposition and enrichment in marginal sediments of Old Red Sandstone or younger age.