Rapid isotope analysis of lead and strontium by laser ablation ICP multi-collector mass spectrometry: a feasibility study based on gold occurrences in the Scottish Dalradian

摘要

Radiogenic isotope studies (e.g. ~(208)Pb/~(204)Pb, ~(207)Pb/~(204)Pb, ~(206)Pb/~(204)Pb and ~(86)Sr/~(87)Sr) provide important information that helps constrain fluid processes and metal sources in studies of mineral deposits. However, the complex chemical separation and analytical procedure required for conventional thermal-ionization mass spectrometry (TIMS) often means that data on a specific deposit or region are limited in scope. Laser ablation ICP multi-collector mass spectrometry offers an alternative technique for rapid acquisition of considerable amounts of high-precision isotope data on regional and deposit scales using a variety of sample types, without the need for chemical preparation.Several sample presentations were tested. These included millimetric hand-picked mineral fragments, standard polished thin sections (20-30 #mu#m in thickness), fluid inclusion wafers (+100 #mu#m thick), thick polished sections (100-200 #mu#m) and polished blocks. Lead isotope determinations were undertaken on galena, pyrite, chalcopyrite, arsenopyrite, tetrahedrite, sphalerite, native bismuth, iron oxide (?goethite) and tellurides. For strontium isotope analysis calcite and dolomite were the principal minerals. In total, 81 samples from mineralized localities were analysed (e.g. Lagalochan, Calliachar-Urlar Burns, Corrie Buie, Tomnadashan, Inverneil and Meall Mor).