Abstract

Inductively coupled plasma-mass spectrometry (ICP-MS) was used as alternative to thermal ionization mass spectrometer (TIMS) for age dating of granite samples originating from different magmatic volcanic rock formations on the Arabian shield. Cation exchange chromatography was used to avoid isobaric overlap of ⁸⁷Rb with⁸⁷Sr and ²⁰⁴Hg with ²⁰⁴Pb ions signals to the largest possible extent, while mathematical correction was applied to correct for the remaining interference. Sr was separated from its matrix using a crown ether-Eichrom's Sr resin. Pb separated from its matrix by developing a method using a crown ether-Eichrom's Sr resin.  The accuracy of the method developed was evaluated by means of isotopic analysis of strontium carbonate SRM-987 and common lead SRM-981 isotopic standards from NIST. Precisions of ⁸⁷Sr/⁸⁶Sr and ²⁰⁶Pb/²⁰⁴Pb isotope ratios measurements are < 0.1% and 0.3% (1), respectively. Overall, this case study shows the merits of ICP-MS for exploratory age determinations and studies of ⁸⁷Sr/⁸⁶Sr and ²⁰⁶Pb/²⁰⁴Pb isotope ratios which can differentiate between magmatic origin of granite.

Key words: Age dating, ICP-MS, granite, U-Pb, Rb-Sr.