history of geochemistry

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history of geochemistry Geochemistry deals with the distribution and migration of the chemical elements within the Earth and, as such, is distinct from mineralogy and petrology, which have a history of going back to classical times. This branch of Earth science has largely developed during the twentieth century, though the word itself was first used by the Swiss chemist, C. F. Schönbein, in 1813. Thus the discovery of the different elements marks episodes in the history of the subject. Perhaps it all began with Lavoisier, who recognized some 31 elements in 1789. Before the end of the eighteenth century another eight were known. The nineteenth century saw the virtual completion of the periodic table of D. I. Mendeleev. Some short-lived radioactive elements were soon to be added. Thus for about a hundred years geochemical data had been largely the by-products of mineralogical investigations of the outermost parts of the crust of the Earth.

In 1884, the US Geological Survey appointed a Chief Chemist, F. W. Clarke, and set up a laboratory to investigate the chemistry of the planet. It was to be concerned with analyses of all kinds of materials sent in by the Survey's field officers, and it amassed a wealth of sample data. With the establishment of the Geophysical Laboratory by the Carnegie Institution in Washington in 1904, the principles of physical chemistry were to be applied to the study of geological processes, especially the evolution of the rock-forming minerals.

A few years later V. M. Goldschmidt at the University of Oslo applied the phase rule to mineralogical changes brought about during contact metamorphism of sedimentary rocks. His subsequent studies in metamorphism all showed that metamorphic changes could be interpreted in terms of the principles of chemical equilibrium. Meanwhile X-ray crystallography had been initiated by M. T. F. von Laue in Germany, although it took some time to make an impact on geochemistry. Spectrographic methods were also developed. Geochemists were interested in the concept of the geochemical cycle and began to speculate on the nature of the matter in the interior of the Earth and on the chemical evolution of the planet. In the USSR a school of geochemistry was developed energetically by V. I. Vernadsky and his successors, such as A. P. Vinogradov. Their work was largely directed towards the search for and exploration of mineral resources.

After the Second World War, there was a surge of interest in radioactivity within the Earth, and new methods of analysis and instrumentation, such as the electron probe, were invented. Two of the most significant and rapidly expanding fields of research today are organic geochemistry and biogeochemistry. Organic materials are found in many sedimentary rocks of all ages from the Archaean onwards. Organic geochemical research has been concerned primarily with the origin and evolution of living materials and their fate after burial. Much research has been of interest to, and sponsored by, the petroleum industry, and many facets of the research are as significant to stratigraphy and basin analysis as to palaeobiology

D. L. Dineley

geochemistry, history of see history of geochemistry