Geochemistry

The geochemistry implements tools and concepts of the Chimie to carry out an exhaustive scientific study of the Ground and, to a certain extent, beyond. With regard to the Earth, this discipline gives itself for objective the description of the cycles by which the majority of the chemical elements are led alternatively surfaces some and in-depth within the Earth. Bound to the Cosmochimie, it is interested in the planetary formation processes and intraplanétaires.

From a applicatif point of view, the goals of geochemistry are, inter alia:

  • determination of the composition of the various terrestrial envelopes and their evolution, of the high layers of the atmosphere to the Seed;
  • the quantification of the transfers of Matter and energy within the Earth; the quantification of the interactions between its various envelopes;
  • determination of the age of the rocks and the events having affected the Earth, by the means of the Géochronologie;
  • the study of the last environmental conditions (Paléoenvironnement S).

In its ramifications theoretical and applied, geochemistry as well covers endogenous processes as exogenic, on organic material or not organics. Thus, the application of the methods of geochemistry to the study of the living beings gave rise to the Biogéochimie. The two greater fields remains about it however the Géochronologie and the study of the “hot” rocks (in-depth) or “cold” (on the surface), on Earth or in the other planetary systems.

Historical elements

The invention of the term of “geochemistry” is allotted to Schönstein. Initially extension of chemistry through surface mineralogy, geochemistry acquired a statute of discipline to whole share after the Second world war, at the time of the development of the isotopic Géologie (absolute geochronology). By its approach transdisciplinaire, geochemistry is an good example of “glue” between several fields with the distinct objectives, like the Physique, the Biologie, paleontology (also multidisciplinary discipline), etc

Methods of analysis

The recognition of the rocks calls upon three types of analyzes:

  • the Micrography: preparation of a thin blade of rock and observation to the optical Microscope, in particular to the polarized light;
  • the chemical Analysis elementary: to determine the composition in elements of a rock (mass Concentration of the various elements, in general translated in the form of Oxide S for the major elements); initially made with reactions chemical (proportionings) element by element, these analyzes are now made with total physical methods giving the concentration in all the elements like the mass spectrometry to source plasma or the Spectrométrie of x-ray fluorescence;
  • analysis of phase by Diffraction of x-rays: one has access to the crystalline Structure components, and one can thus determine the nature of the phases, for example to recognize the various forms of crystallization of the Silice or to know if the Calcium is present in the form of CAD or of CaCO3.

See too

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