自然体系中元素的分布.ppt

1 The Chemical Composition of the Solar System and the Earth Two suggestions Expertise comes from making all possible mistakes (Niels Bohr) Nothing can be obtained in geochemistry without careful analytical work (C.J. Allegre) Further readings W.M. White, Geochemistry. A on-line text book. S.R. Taylor and S.M., 1995. The Continental Crust: Its Composition and Evolution. Blackwell, Oxford. W.F. McDonough and S.Sun, The Composition of the Earth, Chemical Geology, 120: 223-253. Geochemical Earth Reference Model (GERM) www.EarthR Why do we study element abundances? Fundamental for any geochemical studies Confusing terms Abundance: for a large system, e.g., Cosmos, Sun, Moon, Earth, crust, regional crust Content/concentration: for a smaller system, e.g., rocks, minerals, natural water. Part 1 The Solar/Cosmic system Sources for studies Meteorite Sun’s Photosphere Cosmic rays Earth and moon Classification of meteorites according to texture and chemical composition (White, 2001) Relative abundance of major types of meteorite falls Characteristics of chondrite groups Ivuna meteorite What does the classification CI1 mean? Condensation（冷凝） sequence of a gas with a solar composition Condesation sequence of minerals Goldschmidt’s classification of elements Classification of elements(McDonough and Sun, 1995) Classification of elements according to volatility There is much interest in high T component, i.e., the so-called Refractory Inclusions (RI) or Ca-Al inclusions (CAI), because their composition represents that of the first condensates from a high T gas. Carton illustrating the process involved in formation of chondrites and their components Abundances of elements in sun’s photosphere vs their abundances in CI chondrites (White, 2001) Comparison of element abundances in solar photosphere and CI carbonaceous chondrites (Taylor and McLennan, 1995) Solar system abundances of elements relative to Si=106 Characteristic of element abundances of the solar system H