Planets differentiated

Figure P.2 shows the relative abundance of the elements in the universe. It is seen that 99.9% of the elements in the universe are H and He the abundance scale being a quasi-logarithmic one indicates H to be 10 times more abundant than He. Figure P.2 (right) shows planets differentiation in our solar system in relation to abundance of atmosphere, silicates (products with Si) and other metals. Planets are made up of rare materials that include elements with affinity for oxygen (litophile) Si, Al, Ti, Cr, Mn, Fe alkaline elements alkaline metals (crystals) rare elements those with affinity for sulfur and oxygen (calcophile) Cu, Co, Ni, Zn, Pb, Sb, Mo, Fe and metal alloy of iron sidemphile) Fe, Ni, Pt, Ir, Os, Re, Au, Rh.

FIGURE P.2 Left the (relative) abundance of elements in Universe right the planets differentiation in our solar system according to the (relative) abundance of atmosphere, silicates and metals after [Mineralogy (2001). Lectures Notes of Mineralogy, University of Bristol (Curator Prof D. M. Sherman)]. 

Purifications of elfamycins have been described in the Hterature using Craig distribution (2,34), chromatography on Sephadex LH-20 (2,14,26) and Amberlite XAD-2 (10,17,19,26), supercritical fluid extraction (37), and chromatography on an Ito multilayer cod planet centrifuge (26,38). and nmr assignments of most elfamycins have been accompHshed (3,24,26,32). The characteristic uv spectra permits some differentiation (12) and bathochromic shifts associated with Al " complexation have been used to quantify efrotomycin (2, R = CH ) in feed premixes (39,40). 

Rabinowicz M, Ceuleneer G, Monnereau M, Rosemberg C (1990) Three-dimensional models of mantle flow across a low-viscosity zone implications for hotspot dynamics. Earth Planet Sci Lett 99 170-184 Reid MR(1995) Processes of mantle enrichment and magmatic differentiation in the eastern Snake River Plain Th isotope evidence. Earth Planet Sci Lett, 131 239-254 Reid MR, Ramos FC (1996) Chemical dynamics of enriched mantle in the southwestern United States Thorium isotope evidence. Earth Planet Sci Lett, 138 67-81. 

Sigmarsson O, Condomines M, Fomcade S (1992) A detailed Th, Sr and O isotope study of Hekla differentiation processes in an Icelandic Volcano. Contrib Mineral Petrol 112 20-34 Sigmarsson O, Condomines M, Fourcade S (1992) Mantle and crustal contribution in the genesis of recent basalts from off-rift zones in Iceland constraints from Th, Sr and O isotopes. Earth Planet Sci Lett 110 149-162... 

Albarede F (2001) Radiogenic ingrowth in systems with multiple reservoirs applications to the differentiation of the mantle-crust system. Earth Planet Sci Lett 189 59-73... 

Reagan MK, Sims KW, Erich J, Thomas RB, Cheng H, Edwards RL, Layne G, Ball L (2003) Timescales of differentiation from mafic parents to rhyolite in North American continental arcs. J Petrol (in press) Regelous M, Collerson KD, Ewart A, Wendt JI (1997) Trace element transport rates in subduction zones evidence from Th, Sr and Pb isotope data for Tonga-Kermadec arc lavas. Earth Planet Sci Lett 150 291-302... 

The Earth s crust, mantle and core are strongly influenced by differentiation processes which could have resulted from gravitational separation ( smelting ) in an early molten phase of the planet, or from the sequence in which different chemical species condensed from the primitive solar nebula and were subsequently accreted. Seismology indicates that there is a liquid core (with a solid inner core) with radius 3500 km consisting mainly of iron (with some Ni and FeS) surrounded by a plastic (Fe, Mg silicate) mantle of thickness 2900 km. 

Hofmann, A. W. (1988). Chemical differentiation of the Earth the relationship between mantle continental crust, and oceanic crust. Earth Planet. Sci. Letters, 90,... 

Our chemical experiences suggest that differential equations seem to be something stable, and by that we mean that, if there is a small change in one of the conditions, either initial concentrations or rate constants, we expect small changes in the outcomes as well. The classical example for a stable system is our solar system of planets orbiting the sun. Their trajectories are defined by their masses and initial location and velocity, all of which are the initial parameters of a relatively simple system of differential equations. As we all know, the system is very stable and we can predict the trajectories with an incredible precision, e.g. the eclipses and even the returns of comets. For a long time, humanity believed that the whole universe behaves in a similarly predictable way, of course much more complex but still essentially predictable. Descartes was the first to formally propose such a point of view. 

Caro G, Bourdon B, Birck JL, Moorbath S (2003) Sm- Nd evidence from Isua metamorphosed sediments for early differentiation of the Earth s mantle. Nature 423 428-432 Chen JH, Wasserburg GJ (1981) The isotopic composition of uranium and lead in Allende inclusions and meteoritic phosphates. Earth Planet Sci Lett 52 1-15... 

Mullane E, Russel SS, Gounelle M (2002) Iron isotope fractionation within a differentiated asteroidial sample suite. 65 Annual Meteoritical Society Meeting, abstract number 5157 Mullane E, Russel SS, Gounelle M, Mason TED (2003a) Iron isotope composition of Allende and Chainpur chondrules effects of equilibration and thermal history. Lunar Planet Sci Conf XXXIV, abstract number 1027... 

Planet Earth acquired an ocean early in its history, probably by 3.8 billion years before present. Most of the water is thought to have been released during the process of differentiation in which density-driven convection and cooling caused the still-molten planet to separate into layers of decreasing density, i.e., core, mantle, crust, and atmosphere. Once the crust had cooled sufficiently, gaseous water condensed to form a permanent ocean. 

Weyer S, Anbar AD, Brey GP, Miinker C, Mezger K (2005) Iron isotope fractionation during planetary differentiation. Earth Planet Sci Lett 240 251-264 White JWC (1989) Stable hydrogen isotope ratios in plants a review of current theory and some potential applications. In Stable isotopes in ecological research. Ecological Studies 68. Springer Verlag, New York, p. 142-162... 

The interiors of planets, moons, and many asteroids either are, or have been in the past, molten. The behavior of molten silicates and metal is important in understanding how a planet or moon evolved from an undifferentiated collection of presolar materials into the differentiated object we see today. Basaltic volcanism is ubiquitous on the terrestrial planets and many asteroids. A knowledge of atomic structure and chemical bonding is necessary to understand how basaltic melts are generated and how they crystallize. Melting and crystallization are also important processes in the formation of chondrules, tiny millimeter-sized spherical obj ects that give chondritic meteorites their name. The melting, crystallization, and sublimation of ices are dominant processes in the histories of the moons of the outer planets, comets, asteroids, and probably of the Earth. 

Some meteorites, and all planetary samples, have undergone melting and differentiation at some stage. Hence, the compositions of differentiated materials do not resemble solar system abundances. These samples can, however, tell us about various geochemical processes within asteroids and planets. 

Planetary differentiation is a fractionation event of the first order, and it involves both chemical fractionation and physical fractionation processes. Planetary crusts are enriched in elements that occur in silicate minerals that melt at relatively low temperatures. Recall from Chapter 4 that the high solar system abundances of magnesium, silicon, and iron mean that the silicate portions of planetesimals and planets will be dominated by olivine and pyroxenes. Partial melting of sources dominated by olivine and pyroxene ( ultramafic rocks ) produces basaltic liquids that ascend buoyantly and erupt on the surface. It is thus no surprise that most crusts are made of basalts. Remelting of basaltic crust produces magmas richer in silica, eventually resulting in granites, as on the Earth. 

Accretion, differentiation, and igneous history of planets and the Moon... 

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