2.3.3. Constraints by isotope geology

Isotope geology uses analytical methods and techniques for geochronology, such as age determinations and definition of process rates, and isotopic tracer studies to analyze transport between various chemical reservoirs. In order to be able to answer questions concerning the chemical evolution of the Solid Earth through time and space, as well as feedback mechanisms between reservoirs contributing to the Solid Earth, it is necessary to identify, record and quantify the underlying processes. An aspect important to the understanding of forces driving these processes is the timing and quantification of mass transfer and chemical fluxes taking place at different scales - from global to mineral lattice.

Analytical techniques in isotope geology have improved considerably, owing to advances in mass-spectrometry and chemistry, and to the use of new techniques such as laser probing. It is now possible to analyze small quantities of material, single grains and spots within a crystal with high precision. Particularly promising techniques are fission track analysis, exposure age dating using noble gas isotopes of 21Ne and 3He, Ar-laser probing and U-series. TOPO-EUROPE researchers have in-depth experience in all of these techniques (Sanders et al., 1999; Necea et al., 2005; Ruszkiczay-Rudiger et al., 2005; Juez-Larré and Andriessen, 2006).

Thermochronologic methods provide estimates of regional variations in the timing, duration and rate of uplift and erosion over long-term periods. During the last decade, apatite fission track thermochronology has emerged as a powerful technique to unravel and quantify the denudation history of regionally elevated basement regions, owing to its ability to constrain the low-temperature (< 120°C) cooling history of rock samples (Fig. 19) (Ehlers and Farley, 2003; Reiners and Ehlers, 2005).