Meteorites glassy

The Se/ Se ratios of CDT and 3 other iron meteorite samples were determined by Rouxel et al. (2002). CDT had the greatest ratio, and the other meteorites ranged from -0.2%o to -0.6%o relative to CDT. Four basaltic reference materials, two glassy MORB s, and one peridotite also analyzed by Rouxel et al. (2002) were within 0.2%o of CDT. These results suggest that the earth s mantle is close in Se isotope composition to CDT, and that CDT is, tentatively, a reasonable proxy for the bulk composition of the earth. 

Tektites Glassy rocks that range up to a few centimeters in length. Formation is thought to have been a result of meteorite impacts that liquefied and ejected molten crustal rocks. As the ejecta feU back to Earth, they cooled and froze into teardrop and dumbbell shapes. Small tektites are called microtektites. 

Tektite Glassy spheroids that probably form from meteorite impacts. Most tektites are less than 1 mm in... 

Several types of the early Solar System materials are available for laboratory analysis (see Chapter 1 and Table 1.1 and Fig. 1.1). Each material has unique characteristics and provides specific constraints on the chemistry of the solar nebula. Major components of this sample are meteorites, fragments of asteroids, that serve as an excellent archive of the early Solar System conditions. Primitive chondritic meteorites contain glassy spherical inclusions termed chondrules, some of the oldest solids in the Solar System. Most chondrites were modified by aqueous alteration or metamorphic processes in parent bodies but there are some chondrites that are minimally altered (un-equilibrated chondrites, UCs). They have yielded a wealth of information on the chemistry, physics, and evolution of the young Solar System. 

In contrast to Earth, Martian Xe apparently did not evolve from a U-Xe progenitor. Modeling derivation of primordial Xe composition on Mars is based on analyses of atmospheric gases trapped in glassy phases of SNC meteorites (Swindle 2002, this volume). Present ambiguities in this data base are such that two different solar-system Xe compositions, carbonaceous chondrite (Cl)-Xe and SW-Xe, are possible candidates—but not U-Xe. Exclusion of U-Xe as the dominant primordial atmospheric inventory on Mars, despite the implication of the terrestrial modeling that it was a major component of the nebular gas phase, requires that accretion of Cl- or SW-Xe-rich materials from sources more localized in space or time has overwhelmed the isotopic signature of its presence. 

Some glassy materials in meteorites and from the moon are assumed to be original condensed matter which never has undergone melting. The oldest ages seem all to converge at 4.6 X10 y. Thus we conclude that this was the time when our planetary system began to form (the basis for the estimate of the age of our sun in 17.1.4). 

The East Antarctic ice sheet transports not only meteorite specimens that have fallen onto its surface, but it also contains a mixture of small particles of terrestrial and extraterrestrial origin (Cassidy 1964). The extraterrestrial component of this sediment consists of unmelted micrometeorites (MMs), glassy cosmic spherules, and interplanetary dust particles (IDPs) which include the particles released by comets as they pass through the solar system (Faure and Mensing 2005, 2007). 

Meteorite-ablation spherules Form when the molten layer of stony meteoroids passing through the terrestrial atmosphere is stripped off and congeals into glassy spherules that fall to the surface of the Earth. 

Shima M (1966) Glassy spherules (microtektite ) found in ice at Scott Base, Antarctica J Geophys Res 71(14) 3595-3596 Shinonaga T, Endo K, Ebihara M, Heumann KG, Nakahara H (1994) Weathering of Antarctic meteorites investigated from contents of Fe +, chlorine, and iodine. Geochim Cosmochim Acta 59 3735-3740... 

This modern classification is depicted briefly in Table 13.33. Glassy meteorites known as tektites are also found and will be presented at the end of this section. 

Two major features formed to break up the smooth texture. Calcium and aluminum stuck to each other and dissolved in residual water, gathering together as whitish, glassy drops. Also, in big meteorites, heavy iron and nickel sank down into a dense core with traces of copper and zinc. In this way the number of minerals in the region of the newly accumulating Earth increased to 250. 

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