Dating techniques zircon geochronology

Since the middle of the 1980s, the traditional method of zircon geochronology was complemented by the use of the sensitive high-resolution ion microprobe (SHRIMP) [17], with which 15 pm diameter spots on zircons can be dated, and metamict or mixed-age domains avoided. Since minimal amounts of material are used, this method is still preferred in cases where the material to be analyzed is scarce, such as zircons from extraterrestrial samples, or the early Archean ( 4.4 Ga) [18]. Unfortunately, the number of SHRIMP instmments is limited, and in cases where scarcity of material is not a problem, and a precision on the level of a few million years is acceptable, SHRIMP and TIMS techniques for zircon dating have been largely replaced by LA-ICP-MS analyses, pioneered in the early 1990s [19,20]. Here a laser beam is used to excavate a small (15-90 pm diameter) pit in the mineral, from which the ablated material is transferred to the plasma of an ICP-MS instrument, where ionization and analysis take place (see also Chapters 2 and 4). 

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