Research
Isotope geochemistry addresses questions related to origin, structure, composition and evolution of the Earth, and contributes to the understanding of how the Earth operates. Isotope geochemistry and geochronology are vital to all aspects of Earth Sciences. Isotope geochemistry provides (1) the only way to obtain absolute ages and rates of geological processes to constrain the timing of geological events, and (2) powerful tracers of transport between various chemical reversoirs. Especially important in this respect is the observation that progress of our understanding of how the Earth System operates are derived from development of new techniques for the acquistion of original data on the Earth itself. Analytical techniques in isotope geochemistry to constrain parameters relevant to Earth System Science have improved considerable, because of advances in mass-spectrometry and chemistry, and the use of new techniques like laser-probing. Nowadays it is possible to analyse small quantities of material, single grains and spots within a crystal, with high precision, in particular using noble gas isotopes, fission track analytical techniques, Ar-laser probing and U-Pb system. The isotope geochemistry group at the faculty of Earth Sciences, VU, has broad experience in all these techniques, together with the common methods like Rb-Sr, Sm-Nd and U-Pb. All these techniques require a different analytical approach, are labor intensive and time consuming, and need high skilled analytical-technical support.
In the last ten years the scope of research in isotope geochemistry in the Netherlands has been evolved to address geological problems in an integrated way. In the early nineties the focus of the research was aimed at a variety of magmatic and hydrothermal processes in the continental lithosphere, largely on the chemical processing in igneous and metamorphic systems and the underlying thermal causes.
In 1992 the section Isotope Geology has defined a scientific working plan with the following goals and purposes to be achieved.
Geochronology and the determination of rates of processes
The application of natural occurring isotopic decay systems to determine the timing, duration and quantification of geological processes with emphasis on vertical motions in both sedimentary basins and crystalline basement,
Isotopic tracer studies
To study and quantify exchange of material between various reservoirs in lithosphere and mantle, and
Development and improvement of analytical techniques
Development and implication of analytical techniques for rare gas isotope analyses, laser Ar-probe and improvement of solid source chemical and spectrometric analytical procedures to measure with great precision and accuracy very tiny amounts of geological sample material. All the defined goals in the field of developing and improving analytical techniques for the application of radiogenic decay systems have been achieved and the analytical procedures are now being applied. The experimental basis to apply cosmogenic nuclides of rare gas isotopes -3He and 21,22 Ne- for determination of exposure age dating is present (Dr. T.J. Dunai), the facilities for high precision Ar-geochronology with the laser techniques is operational on a routine basis (Dr. J.R. Wijbrans), and for the determination of nuclides of the U-series (234U, 230Th, 231Pa and 226Ra) the analytical procedures are developed and tested (Dr. T.R. Elliott). Also the chemical and mass-spectrometric procedures for measuring Li-isotopes have been developed (Dr. T.R. Elliott). The improvement and expansion of the analytical facilities have been achieved in close collaboration and with intense support of the chemical and mass-spectrometric laboratories, under supervision of Dr. P.Z. Vroon and Dr. G.R. Davies, respectively.
With the development and implication of new methodologies and improvement of existing analytical procedures the isotope geochemistry group of the VU has realized an excellent position to do scientific research in an integrated way. The success of the group is clearly recognized in the increase of both second and third stream money position the group managed to achieve in the last couple of years.
