Geoanalysis: Past, Present and Future†

Abstract

A review of trends in the use of techniques for the chemical analysis of geological samples has been undertaken by abstracting details from reference material characterisation programmes published over the period 1980–1997 and from papers published in Geochimica et Cosmochimica Acta over a similar period. An analysis of these details shows that whereas during the 1980s, XRF and INAA were the two most popular techniques chosen for the major and trace element analysis of silicate rocks, this role continues to be filled by XRF but now complemented by ICP-MS. An equivalent survey of the geochemical use of isotope measurements shows that improvements in the sensitivity and precision of mass spectrometry instrumentation has led to new analytical capabilities: for example, in the application to the Sm–Nd and U–Pb isotope systems in the 1980s and to Re–Os in the 1990s. If these instrument developments continue, the measurement of new isotope systems may become possible including, for example, those related to nucleosynthetic processes. However, it is argued that the greatest influence in future years will arise from the further development of microprobe techniques. Already some of these techniques have demonstrated the importance of providing data that takes into account zoning effects in individual minerals, as in the U–Pb dating of zircon by ion probe and the dating of selected minerals using the laser Ar–Ar technique. Indeed, in these applications, equivalent determinations on bulk samples are now largely discredited, because they mask variations at the mineralogical level. It is likely, therefore, that with further developments in microprobe instrumentation and refinements in geochemical models for interpreting microanalysis data, this area of endeavour will play an increasingly important role in future geochemical studies.