The Role of LA–ICP–MS in Palaeoclimate Research

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is both versatile and widely applicable and, arguably, has become the key microanalytical technique over the past 15 years. This technique owes much of its success to the unrivalled combination of limited sample preparation with no vacuum requirements, sub-ng/g detection limits, highest-precision isotope capability, very large dynamic (concentration) range, limited matrix dependency, relatively simple mass spectra due to the high-temperature ICP-excitation source and, not least, an overall comparatively low capital cost.

The initial applications of LA–ICP–MS in the Earth sciences focused on trace element analyses of high-temperature minerals and the development of U–Pb dating of zircons. Consequently, there were only a few pioneering low-temperature applications (e.g. Perkins et al. 1991). This was largely the direct result of the poor absorption of key low-temperature minerals, such as carbonates, at the infrared or visible laser wavelengths used during early LA–ICP–MS development. This changed fundamentally with deep-UV lasers during the late 1990s (Jeffries et al. 1998; Sinclair et al. 1998).

In many ways, there is a natural match between LA–ICP–MS and low-temperature palaeoclimate and environmental applications. As such, it is hardly surprising that LA–ICP–MS analysis – as applied to carbonates, phosphates, wood and even ice cores – has seen an enormous increase from the 2000s onwards. Figure 1 shows some common palaeoclimate and environmental archives suitable for LA–ICP–MS analysis and some typical used proxies. No other microanalytical technique matches the versatility, applicability and low-cost approach of LA–ICP–MS (Table 1). Secondary ion mass spectrometry (SIMS) will remain, for some time, the method of choice for spatially resolved isotope ratio analysis of the light elements (chiefly O, C). However, SIMS cannot compete in terms of analysis time, sample throughput, sensitivity, ease of operation, lack of sample preparation and availability with LA–ICP–MS, neither for trace elemental nor highest-precision isotope ratio analysis (e.g. Sr). Alternatively, electron microprobe analysis (EMPA) offers μm-scale spatial resolution but suffers from low emission yields, which restricts analytical capabilities to major or minor elements, and EMPA cannot provide isotope ratio analysis.

Here, we briefly review the early development of LA–ICP–MS for palaeoclimate applications, showcase selected current methodological practices and achievements and present an outlook onto emerging fields.