Dating cassiterite using laser ablation ICP-MS

- Cassiterite U-Pb dating results using LA-ICP-MS are comparable to those using LA-MC-ICP-MS.
- Tera-Wasserburg U-Pb intercept age is far better than the 206Pb/207Pb versus 238U/207Pb “isochron” age.
- Multiple common Pb in cassiterite are often associated with fluid and mineral inclusions that may be identified and avoided.

Cassiterite is the main ore mineral of Sn deposits, and may be used to date tin mineralization processes/processes. Both isotope dilution thermal ionization mass spectrometer (ID-TIMS) and laser ablation multi-collector inductively coupled plasma mass spectrometer (LA-MC-ICP-MS) have been applied to cassiterite U-Pb dating. Here we show that cassiterite U-Pb dating results using LA-ICP-MS are comparable to those using LA-MC-ICP-MS. Our results also show that Tera-Wasserburg U-Pb intercept age is far better than the previously used 206Pb/207Pb versus 238U/207Pb “isochron” age because the latter weighted data points with low proportions of common Pb more heavily, such that introducing larger errors. Moreover, 206Pbi/207Pb changes with age and 238U/207Pb ratios, such that yields results younger than the real ages with larger errors. Samples with multiple common Pb sources are difficult to date. Nevertheless, multiple common Pb in cassiterite are often associated with fluid inclusions that may be identified and avoided. The precisions of cassiterite U-Pb ages are not as good as zircon ages, but they provide direct dating on the mineralization processes/processes. Therefore, coupled studies on zircon and cassiterite dating may provide constraints on the relation between magmatism ± hydrothermal activities and mineralization.