Stony Meteorites Research Articles

Certain peculiarities in the distribution of mercury in meteorites

This paper presents chemical analyses of mercury in 123 specimens of 58 meteorites. A statistical comparison is made of the mercury content in meteorites (using all available data) as a function of their composition and texture. The average mercury abundance in stony meteorites is estimated as 6.6 ppm. Stony and iron meteorites differ significantly in mercury content. Among stones, chondrites and achondrites show significant differences in the mercury content. In ordinary cbondrites, mineralogy and texture do not seem to have a significant influence on the distribution of mercury, judging from the available number of analyses. Carbonaceous chondrites, in which we found up to 500 ppm mercury, stand out among all other varieties of chondrites. Iron meteorites fall at the other extreme, having the lowest mercury concentrations (generally 0-0x ppm). In specimens of several meteorite classes, troilite is a good mercury concentrator, having a consistently higher mercury content than the meteorite as a whole. Nonetheless, troilite generally accounts for less than one-half the total mercury content of the meteorite.

The geology of the Moon

With traditional astronomical methods in the background, geological exploration of the Moon has developed rapidly, but logically, since the dawn of the space age. As a result of these tremendous strides forward, we have been forced to revise our views of a cold, rigid moon built predominantly from stony meteorites. The interior of the moon is hot; the distant past has seen not only major impacts but also extensive volcanism altering the lunar surface, and major motions within the moon. Even today, weak moonquakes remain to remind us of the past upheavals that accompanied the geological processes now being unraveled through detailed studies of the lunar rocks.

Non-destructive activation analysis of some elements in stony meteorites by proton and bremsstrahlen irradiation

Proton activation was applied for the instrumental analysis of Fe, Ni, Ca, Ti and Cr in stony meteorites. Error sources are discussed, some results are reported, and a comparison is made between this method and photon activation.

A PRELIMINARY SORTING‐OUT OF “NESS COUNTY” METEORITES

With the exception of a distinctive olivine‐bronzite chondrite recognized by H. H. Nininger: “Ness County (1938)”, most of the numerous stony meteorites found in Ness County, Kansas, have been lumped together under the designation “Ness County (1894)”. It is the purpose of this paper to show that at least three separate falls are covered by this name

Bismuth in stony meteorites and standard rocks

Bismuth has been determined by alpha counting of the 210 Po daughter activity of the 210 Bi formed by thermal neutron activation. Results are presented for thirty chondrites, six achondrites, eight separated meteoritic phases, and six U.S. Geological Survey standard rocks. There is no resolvable difference in Bi abundances among the different groups of ordinary chondrites. Bismuth concentration decreases with increasing petrologic grade among the ordinary chondrites. The enstatite chondrites are separable into two groups on the basis of Bi data.

The elemental and isotopic abundance of metallic ions in the lower E-region as measured by a cryogenically pumped quadrupole mass spectrometer

A quadrupole mass spectrometer designed to measure the positive and negative ion composition in the lower ionosphere has been used to study the mettalic ion population in the lower E-region. Ions Na +, Mg +, Al +, K +, Ca +, Cr +, Fe +, Co + and Ni + have been found. Elemental abudances agree within 30% with those in stony meteorites suggesting a meteoritic origin of metallic ions in the ionosphere. Na and K possibly are more abundant than in stony meteorites due to a selective evaporation during the ablation process.

Terrestrial Age of Nineteen Stony Meteorites derived from their Radiocarbon Content

THE effects of cosmic radiation on meteorites have been studied thoroughly during the past 15 yr1,2. 14C is chiefly produced by three nuclear reactions: 14N(n,p)14C, 16O(p,3p)14C and 16O(n,2pn)14C. The first reaction occurs in the Earth's atmosphere3–4 and provides the basis for the well known radiocarbon dating method. The 14N(n,p)14C reaction has its largest cross-sections (σ=1.7 bar) in the thermal neutron energy region. The 16O spallation reactions (σ=2 mbar) require energies above 10 MeV. The air mass of 1 kg cm−2 above the surface of the Earth dissipates most of the energy of the primary cosmic rays. Therefore, 14C production in rocks on the Earth's surface is negligible. The surface of an object in space, however, is exposed to the full flux of the primary cosmic radiation. Meteorites, therefore, contain a measurable amount of high-energy spallation products. Meteorites contain very little nitrogen, and hence the 14C production is dominated by 16O spallation. The equilibrium 14C activity in stony meteorites per unit weight has a different value from that of the terrestrial atmosphere. The approximate average values for the 14C production rate are 120 14C atoms min−1 cm2 at the Earth's surface (containing 1 kg of air) and 60 14C atoms min−1 kg of meteorite5.

Partitioning of potassium between silicates and sulphide melts: Experiments relevant to the earth's core

The partitioning of potassium between roedderite, K 2Mg 5Si 12O 30 and an FeFeS melt was investigated at temperatures about 40°C above the FeFeS eutectic. Roedderite was considered a prime candidate for one of the potassium-bearing phases in the primitive Earth because roedderite and merrihueite are the only two silicates containing essential potassium which have been identified in stony meteorites. A mean K 2S/FeS weight ratio of (3.340 ± 0.015) × 10 −3 was determined in these experiments; a K 2S FeS weight ratio of about 1.0 × 10 −2 would be sufficient to extract all potassium in a chondritic Earth into the core. Application of these results to a primitive chondritic Earth is discussed and it is concluded that extraction of most of the Earth's potassium into the FeFeS core would occur under the conditions in the early Earth.

Isotopic Ratio of Lithium in Chondrite Measured by an Ion Probe Mass Spectrometer

Isotopic abundance ratios of lithium, 7Li/6Li, for four stony meteorites and for a terrestrial granite sample, G-1, are measured by an ion probe mass spectrometer. The measured ratios for the meteorites are about 13 percent lower than the ratio for G-1. The results are inconsistent with those obtained by conventional mass spectrometers with surface ionization ion sources at other laboratories. The mass discrimination effects and the systematic errors, which may lower the measured ratios preferentially for the meteorites, are thoroughly investigated in connection with the characteristics of the ion probe mass spectrometer. The origin of the instrumental bias, however, is not found. Although further experimental work with both types of mass spectrometer should be required to reach the final conclusion, the difference is likely existent from the results.

First Nitride (CrN) in Iron Meteorites

TWO nitrides have been reported previously in stony meteorites; TiN, osbornite1, in enstatite achondrites and Si2N2O, sinoite2, in enstatite chondrites. This communication reports the first nitride, chromium nitride, to be found in iron meteorites; we made the discovery independently of each other. The mineral and its name, carlsbergite, have been approved by the Commission on New Minerals.

Absolute scale for radiation ages of stony meteorites

Absolute production rates of He 3 and Ne 21 in average L-chondrites have been determined from a least-squares fit of noble-gas to Al 26 data, for meteorites of age <2 × 10 6 yr in which Al 26 has not been built up to saturation levels. The values obtained, 2.48 ± 0.23 and 0.466 ± 0.031 × 10 14cc STP g −1 yr −1, are 24% higher than conventional values, based on H 3 measurements. Apparently all published radiation ages of stony meteorites based on conventional production rates are too high by 24%.

RELICT STRUCTURES OF STONY METEORITES IN A MESOZOIC FORMATION OF THE CENTRAL URALS

MeteoriticsVolume 6, Issue 2 p. 99-103 RELICT STRUCTURES OF STONY METEORITES IN A MESOZOIC FORMATION OF THE CENTRAL URALS I. A. Yudin, I. A. YudinSearch for more papers by this author I. A. Yudin, I. A. YudinSearch for more papers by this author First published: June 1971 https://doi.org/10.1111/j.1945-5100.1971.tb00414.xCitations: 4AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume6, Issue2June 1971Pages 99-103 RelatedInformation

The composition of stony meteorites (X) The Ca/Al ratio in mesosiderites

Numerous authors have referred to mesosiderites as mixtures of howardite and (Ni Fe) metal. Modern, accurate analyses suggest that distinct differences exist between the silicate portions of mesosiderites and howardites. In particular, the Ca/Al ratio of mesosiderites (0.88) is distinctly lower than that of the howardites (1.09). It is concluded that mesosiderites cannot be regarded simply as mixtures of metal and howardite.

Asymmetric Distribution of Thermoluminescence in the Ucera Meteorite

THIS article reports the variations of the thermoluminescence (TL) output with depth below the fusion crust of the recently fallen Ucera meteorite. The effects of atmospheric heating on the TL of meteorites have been described by several workers1,2. It has been shown that the TL emission of the material near the surface of stony meteorites is lower than that of the material farther inside. No systematic sampling of the TL of meteorites has, however, been carried out to show the effect of the thermal pulse on the TL distribution within the meteorite. The measurement of the depth of penetration of the heat wave generated by friction when a meteorite falls through the atmosphere is of importance in the determination of meteorite ages using cosmic-ray-produced gases and radiation damage methods. Some of the effects of atmospheric heating on the natural TL output of the Ucera meteorite, as well as possible evidence of non-uniform shielding of the meteorite from cosmic rays, are presented in this communication.

Terrestrial and Meteorite Carbon Appear to Have the Same Isotopic Composition

The carbon-isotope ratio recently obtained for the carbon found in the Murchison meteorite, which has been shown (by the racemic nature of twelve component amino acids) to be free of terrestrial contamination, agrees with that for average terrestrial sediments. This finding indicates that the earth and the stony meteorites contain carbon of the same isotopic composition.

624 Hektor: A Binary Asteroid?

Dunlap and Gehrels (1969) have published lightcurves of the Trojan asteroid 624 Hektor. They proposed a conventional explanation in which Hektor is regarded as having the shape of a cigar. Two circumstances suggest, but do not prove, that Hektor is a binary asteroid. (1) The cigar shape at the conventional density of stony meteorites (3.7 g-cm-3) appears to produce stresses that may well exceed the crushing strength of meteoritic stone. (2) The lightcurves exhibit an asymmetry changing with time that suggests librations of two ellipsoidal components. Observations are clearly required to look for these periodicities when we shall again be nearly in the plane of Hektor’s revolution (or rotation) in 1973. An additional supporting lightcurve is desirable in 1972 and also in 1974. The periods of libration are probably nearly 1 day, if they exist, so that observations should be made from more than one geographic longitude in 1973. The present paper is an exposition on these considerations.

The composition of stony meteorites (VI): a) The Mg [sbnd]Cr relationship in some basaltic achondrites, Apollo 11 soil and Apollo 12 rock 12038 b) The Ba-rare Earth relationship in stony meteorites and Apollo 11 rocks and soil

Several elements, mainly lithophile, have been classified into three groups, according to tendencies and relationships in the basaltic achondrites: (i) Fe, Si and Mn - concentrations uniform and equivalent, in eucrites and howardites (ii) Ca, Al, Sc, Ti, Sr, Y, Zr, Nb, Ba, rare earths, Hf, Ta, Th and U - concentrations in eucrites greater than in howardites. (iii) Mg and Cr - concentrations in howardites greater than eucrites In part (a) of this paper, the Mg Cr relationship is discussed, and in (b) the relationship between Ba and one rare earth, Nd. In both (a) and (b), the relationships are such that there appears to be a close connection between the composition of basaltic achondrites and the lunar surface.

The composition of stony meteorites (VII) the special significance of eucrites Stannern and Nuevo Laredo in lunar-meteorite comparative studies

Several refractory elements (Sc, Sr, Ba, Ti, Y and rare earths, U and Zr) which are strongly enriched in the lunar surface, are enriched in eucrites Nuevo Laredo and Stannern relative to other eucrites and the howardites. Th appears to be an exception. The degrees to which these elements enrich, between average eucrite and eucrites Stannern and Nueavo Laredo, vary considerably. For Sc and Sr, the degree of enrichment is small (∼5–10%) whereas other elements (Zr, Ti, Ba and particularly the rare earths, for example) are more strongly enriched (∼25–100%). Nuevo Laredo and Stannern appear to contain either similar or equivalent amounts of the refractory elements considered here.

The composition of stony meteorites (VII) observations on fractionation between the L and H chondrites

Quantitative concentration differences of the elements Fe, Si, Mg, Ca, Al, Ti, Mn, K and P between the L and H group common chondrites are compared. The Fe difference (26%) is by far the largest. P is positively correlated with Fe, indicating that P may have some siderophile character despite the fact that it occurs either as apatite or merrilite in the common chondrites. P is distinctly enriched in the Fe-high enstatite chondrites. The degree of fractionation of most of the lithophile elements examined is 7–12%; fractionation of Ti appears to be a little less. A critical comparison of the Si Mg relationship in the L and H groups of chondrites indicates that these two abundant lithophile elements are slightly fractionated between these two chondrite groups.

High Voltage (800 Kv) Electron Petrography of Unequilibrated Stony Meteorites — Allende and Parnallee

Electron petrography (transmission study of thin foils of rock prepared from bulk material) has been performed on specimens of the Pueblito de Allende Carbonaceous Chondrite (Type III of Wiik) and on the Parnallee unequi1ibrated ordinary chondrite (Type LL3 of Van Schmus and Wood). Specimens ∼30 μm. thick were prepared by grinding; then further thinned by a low-angle ion-bombardment process until electron-transparency was attained. Polarizing optical petrography in both transmission and reflection was performed at various stages in the thinning process. No damage due to the thinning method was observed in any phases examined, nor was any damage noted due to the high voltage electron beam.