Origin of organic matter in the early solar system—VII. The organic polymer in carbonaceous chondrites

The insoluble polymer from the Murchison C2 chondrite was studied by a variety of degradation techniques: pyrolysis, depolymerization by Na₄P₂O₇ or CF₃COOH, and oxidation by HNO₃, Na₂Cr₂O₇, or O₂/UV light. Products were identified by IR spectroscopy, gas chromatography, and mass spectrometry (time-of-flight and high-resolution). In some cases, parallel measurements were made on a synthetic polymer produced by the Fischer-Tropsch reaction, a meteoritic polymer from the Allende C3V chondrite, and samples of coal or related materials.Our studies confirm the prevailing view that the meteoritic polymer has a bridged aromatic structure with functional groups such as COOH, OH, and CO, but provides much new detail. Oxidation with HNO₃ shows that the meteoritic and synthetic polymers have a similar degree of condensation, greater than that of high-volatile bituminous coal. Gentler oxidation with Cr₂O^2?₇ or O₂/UV led to the identification of 15 aromatic ring systems as the corresponding carboxylic acids: benzene, biphenyl, naphthalene and phenanthrene and their methyl derivatives, fluoranthene (or pyrene), chrysene, fluorenone, benzophenone, anthraquinone; and the heterocyclics dibenzofuran, benzothiophene, dibenzothiophene, pyridine, quinoline (or isoquinoline), and carbazole. Of 11 aliphatic acids identified, three dicarboxylic acids presumably came from hydroaromatic portions of the polymer, whereas eight monocarboxylic acids probably are derived from bridging groups or ring substituents.Depolymerization with CF₃COOH yielded some of the same ring systems, as well as alkanes (C₁–C₈) and alkenes (C₂–C₈), alkyl (C₁–C₅) benzenes and naphthalenes, and methyl- or dimethyl-indene, -indane, -phenol, -pyrrole, and -pyridine. All these compounds were detected below 200°C, and hence probably were indigenous constituents rather than pyrolysis products.Though the match between the synthetic and meteoritic polymer is only fair, several properties of the latter suggest that it, too, was produced by surface catalysis: the predominance of n-alkyl fragments, its occurrence as a surface coating on specific kinds of mineral grains, and the $\text{C}{}^{13}\text{C}{}^{12}$ fractionation between polymer and coexisting carbonates.     

Solar-system abundances of the elements

A new abundance table has been compiled, based on a critical review of all C1 chondrite analyses up to mid-1982. Where C1 data were inaccurate or lacking, data for other meteorite classes were used, but with allowance for fractionation among classes. In a number of cases, interelement ratios from meteorites or lunar and terrestrial rocks as well as solar wind were used to check and constrain abundances. A few elements were interpolated (Ar, Kr, Xe, Hg) or estimated from astronomical data (H, C, N, O, He, Ne).For most elements, the new abundances differ by less than 20% from those of Cameron (1982a). In 14 cases, the change is between 20 and 50% (He, Ne, Be, Br, Nb, Te, I, Xe, La, Gd, Tb, Yb, Ta and Pb) and in 5 others, it exceeds 50% (B, P, Mo, W, Hg). Some important interelement ratios ($\text{Na}\text{K}$, $\text{Se}\text{Te}$, $\text{Rb}\text{Sr}$, $\text{Kr}\text{Xe}$, $\text{La}\text{W}$, $\text{Th}\text{U}$, $\text{Pb}\text{U}$, etc.) are significantly affected by these changes.Three tests were carried out, to see how closely C1 chondrites approximate primordial solar system abundances. (1) A plot of solar vs Cl abundances shows only 7 discrepancies by more than twice the nominal error of the solar abundance: Ga, Ge, Nb, Ag, Lu, W and Os. Most or all apparently reflect errors in the solar data or f-values. (2) The major cosmochemical groups (refractories, siderophiles, volatiles, etc.) show no significant fractionation between the Sun and C1's, except possibly for a slight enrichment of volatiles in Cl's. (3) Abundances of odd-A nuclides between A = 65 and 209 show an almost perfectly smooth trend, with elemental abundances conforming to the slope defined by isotopic abundances. There is no evidence for systematic fractionation of the major cosmochemical groups from each other. Small irregularities (10–15%) show up in the Ag-Cd-In and Sm-Eu regions; the former may be due to a ~ 15% error in the Ag abundance and the latter, to a 10–20% fractionation of Eu during condensation, to contamination of C1 chondrites with interplanetary dust during regolith exposure, or to a change from s-process to r-process dominance.It appears that the new set of abundances is accurate to at least 10%, as irregularities of 5–10% are readily detectable. Accordingly, Cl chondrites seem to match primordial solar-system matter to ? 10%, with only four exceptions. Br and I are definitely and B is possibly fractionated by hydrothermal alteration, whereas Eu seems to be enriched by nebular condensation or regolith contamination.     

Trends in the Postsvecokarelian development of the Baltic Shield

The Postsvecokarelian development of the Baltic Shield shows a parallel development with tension and dolerite intrusions in the core zone and granite intrusions, compression and crustal shortening in the south-western margin. A crustforming event with calk-alkalic granitoid intrusions which with time moves westwards is followed by remelting and intrusion of alkali-intermediate granites and metamorphism. The south-western margin of the Shield probably was a stable ocean/continent border zone for a very long time. In spite of several attempts, no conclusive testable model for the development can be put forward today.

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Zusammenfassung Die postsvekokarelische Entwicklung des Baltischen Schildes ist von einer zeitgemäßen Parallelität mit Tension und Diabasintrusionen in der östlichen Kernzone und Granitintrusionen, Kompression und Krustenverkürzung in der südwestlichen Marginalzone gekennzeichnet. Eine Phase mit Krustenbildung, die mit der Zeit nach Westen rückt, und wo kalkalkalische Granitoide als wesentlichstes neugebildetes Gestein auftreten, wird von Metamorphose und erneutem Aufschmelzen und Intrusionen alkaliintermediärer Granite gefolgt. Die südwestliche Marginalzone des Schildes war ein stabiler Ozean/Kontinent-Grenzbereich während einer langen Zeitperiode. Ein testbares endgültiges Modell der Entwicklung kann heute trotz mehrerer Versuche nicht aufgestellt werden.

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Résumé Le développement postsvécokarélien du bouclier baltique est caractérisé par un parallélisme dans le temps entre l'extension et l'intrusion de diabases dans la zone centrale de l'Est et par des intrusions granitiques, une compression et un rétrécissement crustal dans la zone marginale du Sud-ouest. Une phase avec formation d'une croûte, qui se propage vers l'ouest, et au cours de laquelle les nouvelles roches formées sont essentiellement des granitoïdes calco-alcalins, est suivie d'un métamorphisme et d'une palingenèse avec intrusions de granites alcalins intermédiaires. La zone marginale du Sud-ouest du bouclier était un domaine-limite océan-continent »stable«, pendant une longue période de temps. Une modélisation controlable du développement ne peut être avancée aujourd'hui malgré plusieurs tentatives.

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Sorption of noble gases by solids,with reference to meteorites. II. Chromite and carbon

We studied trapping of noble-gases by chromite and carbon: two putative carriers of primordial noble gases in meteorites. Nineteen samples were synthesized in a Ne-Ar-Kr-Xe atmosphere at 440 K to 720 K, by the following reactions: Fe,Cr + 4H₂O → (Fe,Cr)₃O₄ + 4H₂ (1) or Fe,Cr + 4CO → (Fe,Cr)₃O₄ + 4C + carbides (2)The reactant metal films were prepared either by vacuum evaporation of alloy or by thermal decomposition of Fe- and Cr-carbonyls. The products—including Fe₃O₄, Cr₂O₃, carbides, and unreacted metal—were partially separated by selective solvents, such as HCl, H₂SO₄?H₃PO₄, or HClO₄. Samples were characterized by XRD, SEM, and atomic absorption; noble gases were measured by mass spectrometry. Surface areas, as measured by the BET method, were 2 to 100 m²/g.All samples are dominated by an adsorbed noble gas component that is largely released upon heating at ?400°C or slight etching. Elemental abundance patterns show that this component is derived from the highest-pressure noble gas reservoir seen by the sample—atmosphere or synthesis vessel—indicating that desorption or exchange rates at room T are slow on the time scale of our experiments (up to 1 year). Adsorptive capacity is reduced by up to 2 orders of magnitude upon light etching with HClO₄ (though the surface area actually doubles in this treatment) and, less drastically, by heating. Apparently some active adsorption sites are destroyed by these treatments. A trapped component (typically 30% of the total) is readily detectable only in samples synthesized at partial pressures close to or greater than atmospheric.Noble gas contents roughly obey Henry's Law, but show only slight, if any, correlations with composition, surface area, or adsorption temperature. (Geometric) mean distribution coefficients for bulk samples and HCl-residues are, in 10^?3 cc STP/g atm: Xe (100), Kr (15), Ar (3.5), Ne (0.62). Elemental fractionations are large and variable, but are essentially similar for the adsorbed and trapped components, or for chromite and carbon. They bracket the values for the corresponding meteoritic minerals.

     

226.

GeoRef. thesaurus and guide to indexing | C. Heckman et al. (Editors), 1978. American Geological Institute,Falls Church,Va., 2nd ed., 456 pp., U.S. $ 35.00     

Anders Martinsson 《Earth》1980,15(4):422-423

     

227.

Chemical fractionations in meteorites—XI. C2 chondrites     

Rainer Wolf  Gerhard R. Richter  Alicia B. Woodrow  Edward Anders 《Geochimica et cosmochimica acta》1980,44(5):711-717

Six C2M chondrites (Boriskino, Cold Bokkeveld, Erakot, Essebi, Haripura and Santa Cruz) and the C2R chondrite Al Rais were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Sn, Te, Tl, U, and Zn. Abundances (relative to Cl chondrites) show a systematic dependence on volatility, apparently reflecting volatile loss during formation of chondrules and other high-T components. Elements of nebular condensation temperature (T_c) > 1200 K are undepleted, those of T_c < 700 K are depleted by a constant factor (0.482 ± 0.049 for C2M's) and elements of intermediate volatility are depleted by intermediate factors. The abundances do not “tend to fall monotonically as a function of [T_c],” as previously claimed by Wai and Wasson (1977) for a more restricted temperature range. For meteorites that have suffered little aqueous alteration (Mighei, Murchison, Murray), the mean abundance of volatiles agrees with the matrix content, but for the more altered meteorites, matrix contents are 20–30% higher. Only a few meteorites deviate appreciably from the mean abundance pattern. Al Rais, a C2R chondrite with a significant metal content, is systematically lower in 12 volatiles, but is enriched in Ni and Pd. Haripura and Erakot are enriched in Bi and Tl, possibly from the late condensate, mysterite.     

228.

Isotopic anomalies in meteorites and their origins—V. Search for fission fragment recoils in Allende sulfides     

Roy S. Lewis  Jan Hertogen  Leo Alaerts  Edward Anders 《Geochimica et cosmochimica acta》1979,43(11):1743-1752

Three troilite- and pentlandite-rich samples from the Allende C3 chondrite were analyzed for Xe (and in one case Ne and Ar) by mass spectrometry, in 13–22 temperature steps. All samples released a small ‘CCFXe’ component (enriched in the heavy isotopes Xe^{134, 136}) at the relatively low temperature of 700–800°C, ahead of adsorbed atmospheric Xe (~900°C), radiogenic Xe¹²⁹ (1000°C), and primordial Xe (1250°C). Though such a labile component suggests implanted fission recoils, the simultaneous release of Ne, Ar, and Xe^{124, 126} shows that it instead comes from carbon and perhaps chromite, two major host phases of CCFXe. Apparently small amounts of these phases are occluded in sulfides, and decompose by chemical reaction upon heating. Thus the experiment fails to resolve the nature of CCFXe.A marked enrichment of Xe¹²⁴, without corresponding enrichments in Xe¹²⁶ or Xe^131–136, was observed in the 550–650° and 1400–1500° fractions. Though requiring confirmation, it supports earlier evidence for the complexity and variability of the light xenon component, contrary to claims that it is an integral part of CCFXe.     

229.

Chemical composition of Mars     

John W Morgan  Edward Anders 《Geochimica et cosmochimica acta》1979,43(10):1601-1610

The composition of Mars has been calculated from the cosmochemical model of Ganapathy and Anders (1974) which assumes that planets and chondrites underwent the same 4 fractionation processes in the solar nebula. Because elements of similar volatility stay together in these processes, only 4 index elements (U, Fe, K and Tl or Ar³⁶) are needed to calculate the abundances of all 83 elements in the planet. The values chosen are U = 28 ppb, K = 62 ppm (based on $\text{K}\text{U}\text{= 2200}$ from orbital γ-spectrometry and on thermal history calculations by Toksöz and Hsui (1978) Fe = 26.72% (from geophysical data), and Tl = 0.14 ppb (from the Ar³⁶ and Ar⁴⁰ abundances measured by Viking).The mantle of Mars is an iron-rich [Mg/(Mg + Fe) = 0.77] garnet wehrlite (ρ = 3.52?3.54 g/cm³), similar to McGetchin and Smyth's (1978) estimate but containing more Ca and Al. It is nearly identical to the bulk Moon composition of Morgan et al. (1978b). The core makes up 0.19 of the planet and contains 3.5% S—much less than estimated by other models. Volatiles have nearly Moon-like abundances, being depleted relative to the Earth by factors of 0.36 (K-group, T_cond = 600–1300 K) or 0.029 (Tl group, T_cond < 600 K). The water abundance corresponds to a 9 m layer, but could be higher by as much as a factor of 11.Comparison of model compositions for 5 differentiated planets (Earth, Venus, Mars, Moon, and eucrite parent body) suggests that volatile depletion correlates mainly with size rather than with radial distance from the Sun. However, the relatively high volatile content of shergottites and some chondrites shows that the correlation is not simple; other factors must also be involved.     

230.

A carbonaceous inclusion from the Krymka LL-chondrite: noble gases and trace elements     

Roy S. Lewis  Leo Alaerts  Jan Hertogen  Marie-Josée Janssens  Herbert Palme  Edward Anders 《Geochimica et cosmochimica acta》1979,43(6):897-903

A black inclusion from the Krymka LL3 chondrite was analyzed for 20 trace elements and five noble gases, by radiochemical neutron activation and mass spectrometry. The trace element pattern somewhat resembles that of C1 or C2 chondrites, but with several unique features. Elements of nebular condensation T ? 1000 K (U, Re, Os, Ir, Ni, Pd, Au, Sb and Ge) are essentially undepleted, as in C1 chondrites, but $\text{Re}\text{Ir}$ is 1.49 × higher than the characteristic Cl value. Among elements condensing below 1000 K, Cs, Se, Te, and In are depleted to approximately C2 levels (~0.6 × C1), whereas Ag, Bi, Tl are enriched to ~ 1.6 × C1. Such enrichments are thought to be characteristic of late nebular condensates.The noble-gas pattern also is unique. Gas contents are higher than in C1s, by factors of 2.6 to 19 for Ne through Xe. The $\text{Ar}{}^{36}\text{Xe}{}^{132}$ ratio of 500 is higher than mean values for C1s or C2s (109 or 89) and exceeds even the highest value seen in C3Os, 420, whereas the $\text{He}{}^4\text{Ne}{}^{20}$ ratio of 62 is much lower than the values for C1s and C2s (200–370). The $\text{Xe}{}^{129}\text{Xe}{}^{132}$ and $\text{Xe}{}^{136}\text{Xe}{}^{\mathrm{l32}}$ ratios of 1.040 and 0.320 resemble those of C1 chondrites, and seem to imply typical proportions of radiogenic Xe¹²⁹ and ‘fissiogenic’ xenon.It appears that the inclusion represents a new primitive meteorite type, similar to C-chondrites, but probably a late condensate from a region of higher nebular pressure.     

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	$\text{Ne}\text{Xe}$	$\text{Ar}\text{Xe}$	$\text{Kr}\text{Xe}$
Geom. mean	0.006	0.035	0.15
Range	0.0004-0.03	0.01-0.2	0.06-0.4

Chemical fractionations in meteorites—XI. C2 chondrites

Six C2M chondrites (Boriskino, Cold Bokkeveld, Erakot, Essebi, Haripura and Santa Cruz) and the C2R chondrite Al Rais were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Sn, Te, Tl, U, and Zn. Abundances (relative to Cl chondrites) show a systematic dependence on volatility, apparently reflecting volatile loss during formation of chondrules and other high-T components. Elements of nebular condensation temperature (T_c) > 1200 K are undepleted, those of T_c < 700 K are depleted by a constant factor (0.482 ± 0.049 for C2M's) and elements of intermediate volatility are depleted by intermediate factors. The abundances do not “tend to fall monotonically as a function of [T_c],” as previously claimed by Wai and Wasson (1977) for a more restricted temperature range. For meteorites that have suffered little aqueous alteration (Mighei, Murchison, Murray), the mean abundance of volatiles agrees with the matrix content, but for the more altered meteorites, matrix contents are 20–30% higher. Only a few meteorites deviate appreciably from the mean abundance pattern. Al Rais, a C2R chondrite with a significant metal content, is systematically lower in 12 volatiles, but is enriched in Ni and Pd. Haripura and Erakot are enriched in Bi and Tl, possibly from the late condensate, mysterite.     

Isotopic anomalies in meteorites and their origins—V. Search for fission fragment recoils in Allende sulfides

Three troilite- and pentlandite-rich samples from the Allende C3 chondrite were analyzed for Xe (and in one case Ne and Ar) by mass spectrometry, in 13–22 temperature steps. All samples released a small ‘CCFXe’ component (enriched in the heavy isotopes Xe^{134, 136}) at the relatively low temperature of 700–800°C, ahead of adsorbed atmospheric Xe (~900°C), radiogenic Xe¹²⁹ (1000°C), and primordial Xe (1250°C). Though such a labile component suggests implanted fission recoils, the simultaneous release of Ne, Ar, and Xe^{124, 126} shows that it instead comes from carbon and perhaps chromite, two major host phases of CCFXe. Apparently small amounts of these phases are occluded in sulfides, and decompose by chemical reaction upon heating. Thus the experiment fails to resolve the nature of CCFXe.A marked enrichment of Xe¹²⁴, without corresponding enrichments in Xe¹²⁶ or Xe^131–136, was observed in the 550–650° and 1400–1500° fractions. Though requiring confirmation, it supports earlier evidence for the complexity and variability of the light xenon component, contrary to claims that it is an integral part of CCFXe.     

Chemical composition of Mars

The composition of Mars has been calculated from the cosmochemical model of Ganapathy and Anders (1974) which assumes that planets and chondrites underwent the same 4 fractionation processes in the solar nebula. Because elements of similar volatility stay together in these processes, only 4 index elements (U, Fe, K and Tl or Ar³⁶) are needed to calculate the abundances of all 83 elements in the planet. The values chosen are U = 28 ppb, K = 62 ppm (based on $\text{K}\text{U}\text{= 2200}$ from orbital γ-spectrometry and on thermal history calculations by Toksöz and Hsui (1978) Fe = 26.72% (from geophysical data), and Tl = 0.14 ppb (from the Ar³⁶ and Ar⁴⁰ abundances measured by Viking).The mantle of Mars is an iron-rich [Mg/(Mg + Fe) = 0.77] garnet wehrlite (ρ = 3.52?3.54 g/cm³), similar to McGetchin and Smyth's (1978) estimate but containing more Ca and Al. It is nearly identical to the bulk Moon composition of Morgan et al. (1978b). The core makes up 0.19 of the planet and contains 3.5% S—much less than estimated by other models. Volatiles have nearly Moon-like abundances, being depleted relative to the Earth by factors of 0.36 (K-group, T_cond = 600–1300 K) or 0.029 (Tl group, T_cond < 600 K). The water abundance corresponds to a 9 m layer, but could be higher by as much as a factor of 11.Comparison of model compositions for 5 differentiated planets (Earth, Venus, Mars, Moon, and eucrite parent body) suggests that volatile depletion correlates mainly with size rather than with radial distance from the Sun. However, the relatively high volatile content of shergottites and some chondrites shows that the correlation is not simple; other factors must also be involved.     

A carbonaceous inclusion from the Krymka LL-chondrite: noble gases and trace elements

A black inclusion from the Krymka LL3 chondrite was analyzed for 20 trace elements and five noble gases, by radiochemical neutron activation and mass spectrometry. The trace element pattern somewhat resembles that of C1 or C2 chondrites, but with several unique features. Elements of nebular condensation T ? 1000 K (U, Re, Os, Ir, Ni, Pd, Au, Sb and Ge) are essentially undepleted, as in C1 chondrites, but $\text{Re}\text{Ir}$ is 1.49 × higher than the characteristic Cl value. Among elements condensing below 1000 K, Cs, Se, Te, and In are depleted to approximately C2 levels (~0.6 × C1), whereas Ag, Bi, Tl are enriched to ~ 1.6 × C1. Such enrichments are thought to be characteristic of late nebular condensates.The noble-gas pattern also is unique. Gas contents are higher than in C1s, by factors of 2.6 to 19 for Ne through Xe. The $\text{Ar}{}^{36}\text{Xe}{}^{132}$ ratio of 500 is higher than mean values for C1s or C2s (109 or 89) and exceeds even the highest value seen in C3Os, 420, whereas the $\text{He}{}^4\text{Ne}{}^{20}$ ratio of 62 is much lower than the values for C1s and C2s (200–370). The $\text{Xe}{}^{129}\text{Xe}{}^{132}$ and $\text{Xe}{}^{136}\text{Xe}{}^{\mathrm{l32}}$ ratios of 1.040 and 0.320 resemble those of C1 chondrites, and seem to imply typical proportions of radiogenic Xe¹²⁹ and ‘fissiogenic’ xenon.It appears that the inclusion represents a new primitive meteorite type, similar to C-chondrites, but probably a late condensate from a region of higher nebular pressure.