Volatile elements in chondrites: metamorphism or nebular fractionation?

Three of the most highly metamorphosed meteorites of their respective classes, Shaw (LL7), Karoonda (C5), and Coolidge (C4), were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Te, Tl, U, and Zn. Comparison with data by Lipschutz and coworkers on artificially heated primitive meteorites shows that the natural metamorphism of meteorites cannot have taken place in a system open to volatiles. Shaw, metamorphosed at 1300°C for >10⁶ yr, is less depleted in In, Bi, Ag, Te, Zn, and Tl than Krymka heated at 1000°C for 1 week. Karoonda, metamorphosed at 600°C for many millennia, is less depleted in Bi and Tl than Allende heated at 600°C for 1 week.Data on primordial noble gases also show that the volatile-element patterns of ordinary and carbonaceous chondrites were established by nebular condensation, and changed little if at all during metamorphism. For enstatite chondrites, the evidence is still incomplete, but seems to favor a nebular origin of the volatile pattern.The general constancy of Tl/Rb, Tl/Cs and Tl/U ratios in terrestrial and lunar rocks suggests that loss of volatile metals such as Tl is rare during normal magmatism or metamorphism. Only impact melts show such loss with any frequency.     

Are C1 chondrites chemically fractionated? a trace element study

Six C1 chondrite samples and a C2 xenolith from the Plainview H5 chondrite were analyzed by radiochemical neutron activation for the elements Ag, Au, Bi, Br, Cd, Ce, Cs, Eu, Ge, In, Ir, Lu, Nd, Ni, Os, Pd, Pt, Rb, Re, Sb, Se, Sn, Tb, Te, Tl, Yb, and Zn. The data were combined with 9 earlier analyses from this laboratory and examined for evidence of chemical fractionation in C1 chondrites.A number of elements (Br, Rb, Cs, Au, Re, Os, Ni, Pd, Sb, Bi, In, Te) show small but correlated variations. Those of the first 8 probably reflect hydrothermal alteration in the meteorite parent body, whereas those of Sb, Bi, In, and Te may at least in part involve nebular processes. Br and Au show systematic abundance differences from meteorite to meteorite, which suggests hydrothermal transport on a kilometer scale. The remaining elements vary from sample to sample, suggesting transport on a centimeter scale.There is no conclusive evidence for nebular fractionation affecting C1 's. Though C1 chondrites have lower $\text{Zr}\text{Hf}$ and $\text{Ir}\text{Re}$ ratios than do other chondrite classes, these ratios vary in other classes, suggesting that those classes rather than C1's are fractionated. Three fractionation-prone REE—Ce, Eu, and Yb have essentially the same relative abundances in C1's and all other chondrite classes, and hence apparently are not fractionated in C1's. We did not confirm the large Tb and Yb variations in C1's reported by other workers.We present revised mean C1 abundances for 35 elements, based on the new data and a critical selection of literature data. Changes are generally less than 10%, except for Br, Rb, Ag, Sb, Te, Au, and the REE.The Plainview C2 xenolith has normal trace element abundances, except for 3 elements falling appreciably above the C2 range: Rb, Cs, and Bi. Hydrothermal alteration may be the reason for all 3, though nebular fractionation remains a possibility for Bi.     

H-chondrites: Trace element clues to their origin

We have analyzed 10 H-chondrites for 20 trace elements, using RNAA. The meteorites included 4 of petrologic type 4 and 2 each of types 3, 5 and 6.The data show that H-chondrites are not isochemical. H3's are depleted by some 10% not only in Fe (Dodd, 1976), but also in the siderophiles Os, Re, Ir, Ni, Pd, Au, and Ge. Moreover, the abundance pattern of siderophiles varies systematically with petrologic type. As similar fractionations of REE have been observed by Nakamura (1974), it appears that both the proportions and compositions of the main nebular condensates varied slightly during accretion of the H-chondrites. Thus the higher petrologic types are independent nebular products, not metamorphosed descendants of lower petrologic types.Abundances of highly volatile elements (Cs, Br, Bi, Tl, In, Cd, Ar³⁶) correlate with petrologic type, declining by ≤ 10^?3 from Type 3 to Type 6. The trends differ from those for artificially heated Type 3's (Ikramuddinet al., 1977b; Herzoget al., 1979), but agree passably with theoretical curves for nebular condensation. Apparently the low volatile contents of higher petrologic types are a primary feature, not the result of metamorphic loss.The mineralogy of chondrites suggests that they accreted between 405 K (absence of Fe₃O₄) and 560 K (presence of FeS), and the abundances of Tl, Bi, and In further restrict this interval to 420–500 K. Accretion at 1070 ± 100 K, as proposed by Hutchisonet al. (1979, 1980), leads to some extraordinary problems. Volatiles must be injected into the parent body after cooling, which requires permeation of the body by 10¹¹ times its volume of nebular gas. This process must also achieve a uniform distribution of the less volatile elements (Rb, Cu, Ag, Zn, Ga, Ge, Sn, Sb, Se, F), without freezeout in the colder outer layers.Factor analysis of our data shows 3 groupings: siderophiles (Os, Re, Ir, Ni, Pd, Au, and Ge), volatiles (Ag, Br, In, Cd, Bi, and Tl) and alkalis (Rb and Cs). The remaining 5 elements (U, Zn, Te, Se, and Sb) remain unassociated.     

Chemical fractionations in meteorites—X. Ureilites

Four ureilites (Dyalpur, Goalpara, Haverö, and Novo Urei) were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Rb, Re, Sb, Se, Te, Tl, and U. An attempt has been made to resolve the data into contributions from the parent ultramafic rock and the injected, carbon- and gas-rich vein material. Interelement correlations, supported by analyses of separated vein material (WANKE et al, 1972), suggest that the vein material is enriched about 10-fold in refractory Ir and Re over moderately volatile Ni and Au, and is low in volatiles except Ge, C, and noble gases. It appears to be a refractory-rich nebular condensate that precipitated carbon by surface catalytic reactions at ˜500K and trapped noble gases but few other volatiles. The closest known analogue is a Cr- and C-rich fraction from the Allende meteorite, highly enriched in heavy noble gases and noble metals. By analogy with Allende, the gas-bearing phase in ureilites may have been an Fe, Cr-sulfide.

The ultramafic rock contains siderophiles and chalcophiles (Ni, Au, Ge, S, Se) at ˜0.05 of Cl chondrite level, and highly volatile elements (Rb, Cs, Bi, Tl, Br, Te, In, Cd) at ˜0.01 Cl level. It probably represents the residue from partial melting of a C3V-like chondrite body, under conditions where phase separation was incomplete so that some liquid was retained. The vein material was injected into this rock at some later time.     

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.     

Trace elements in ocean ridge basalt glasses: implications for fractionations during mantle evolution and petrogenesis

Seven well-documented and fresh glassy selvages from ocean floor basalt pillows were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Te, Tl, U and Zn. The samples came from active spreading centers in the Indian and Atlantic Ocean. Glasses from DSDP Leg 24, site 238 (Indian Ocean) have a somewhat peculiar trace element pattern, but this is thought to reflect secondary processes operating at shallow depth, not an anomalous source region in the mantle. Our data rather indicate that heterogeneities in the mantle are confined to the highly incompatible lithophile elements.Chemical fractionations during petrogenesis of tholeiitic basalts are discussed in the light of literature data for primitive peridotitic upper mantle nodules. (Ir, Os), Au, Pd, Ni and Re are strongly fractionated from each other in igneous processes; the unfractionated chondritic mantle pattern thus imposes firm constraints on mantle evolution models. The potentially chalcophile elements Ag, Cd, In and Zn do not behave differently from lithophile elements of the same valency and comparable ionic radius. Residual sulfides are not abundant enough to efficiently control the partitioning of these elements during basalt petrogenesis. However, the poor coherence of Tl to Rb and U in ocean floor basalts could point to retention of Tl by residual sulfides during depletion of the MORB source regions. Sb is strongly depleted in the source regions of ocean ridge basalts; most likely, it was present as a highly incompatible Sb⁵⁺ cation. The limited Rb/Cs fractionation in oceanic tholeiites, as opposed to continental tholeiites and acidic rocks, appears to reflect the low abundance of volatile constituents and hydrous silicates in normal ocean ridge basalts.     

Chemical fractionations in meteorites—IX. C3 chondrites

Four C3V chondrites (Grosnaja, Kaba, Mokoia, Vigarano) and three C3O chondrites (Felix, Kainsaz, and Lancé) were analyzed by radiochemical neutron activation for 17 trace elements. Both classes show a typical chondritic step pattern, reflecting loss of volatiles during chondrule formation. Elements condensing above 1300 K (U, Re, Ir, Ni) are present in essentially Cl chondrite proportions, while moderately volatile elements condensing between 1300 K and 800 K (Ge, Rb, Ag) are depleted by a factor of 0.44. However, elements condensing below 700 K (S, Cs, Bi, Tl, Br, Se, Te, In, Cd) are depleted to a still greater degree, and more so in the Ornans subclass (factor of 0.24, except Cd 0.007) than in the Vigarano subclass (factor of 0.29). This additional depletion may be due to a slight (less than 3-fold) dust-gas fractionation, by settling of dust to the median plane of the solar nebula. Among other chondrite classes, ordinary chondrites show a similar depletion, but C2 chondrites do not. Possibly the undepleted meteorites formed in one of the convection zones of the nebula predicted by Cameron and Pine, whereas the depleted meteorites formed in a quiescent region.The condensation of chalocophile elements as a function of H₂S partial pressure is discussed, in an attempt to explain the drastic difference in Cd abundance between the two subclasses. It appears that the $\text{H}{}_2\text{S}\text{H}{}_2$ ratio is the key variable. C3O's seem to have condensed in a region where enough metallic Fe was present to buffer the H₂S pressure, while C3V's condensed in a more oxidized region, where H₂S was in excess. Accretion temperatures, for an assumed nebular pressure of 10^?5 atm, were between 415 and 430 K for C3O's and less than 440 K for C3V's.Two slightly volatile elements, Sb and Au, show variable depletion, presumably reflecting variable loss during chondrule formation. Indeed, their depletion correlates with the abundance of iron-poor olivine, a measure of the peak temperature and time during chondrule formation.     

“Mysterite” : a late condensate from the solar nebula

We have attempted to clarify the nature of “mysterite”, a material that had been postulated to explain the overabundance of Tl, Bi and Ag in certain chondrites. Four dark clasts and a vein sample from the H6 chondrite Supuhee were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Rb, Re, Sb, Se, Te, Tl and Zn. One of the clasts is enriched in all volatile elements, while the other 4 samples are enriched only in the siderophile volatiles Ag, Bi and Tl. The enrichments range up to 100 times typical H6 chondrite abundances. The proportions of Ag, Bi, Tl suggest the presence of at least two, Tl-rich and Tl-poor, varieties of mysterite ($\text{Tl}\text{Bi}\text{= 7.2}$ and <0.1). The former seems to dominate in Supuhee and Krymka, and the latter in Mezö-Madaras. Apparently mysterite is a late condensate from the solar nebula that collected volatiles left behind by earlier generations of chondrites. It was incorporated in Supuhee and perhaps in other chondrites (mainly of low petrologic types) during brecciation events.     

A “chondritic” eucrite parent body: inference from trace elements

A total of 33 elements (Ag, Al, Au, Bi, Br, Cd, Ce, Co, Cr, Cs. Eu, Fe, Ge, Hf, Ir, Lu, Na, Ni, Os, Pd, Rb, Re, Sb, Se, Se, Si, Sm, Tb, Te, Tl, U, Yb and Zn) were analyzed by radiochemical and instrumental neutron activation in four eucrites: Juvinas (brecciated), Ibitira (vesicular, unbrecciated) and Moore County and Serra de Magé (cumulate, un brecciated).When arranged in order of volatility. Cl—normalized abundance patterns allow nebular and planetary effects to be distinguished. The stepped lithophile pattern reveals the dominance of nebular processes; in Ibitira, refractory elements (Hf, Lu, Tb, Ce, Sm, Yb, U, Eu) are (13.1 ± 0.7) × Cl chondrites; volatile elements (Rb. Cs, Br, Bi) are (6.0 + 1.5) × 10^?2 Cl. The depletion of Tl seems inherent to the eucrite parent body and is mirrored in the chalcophile elements by the marked deficit of Te relative to Se; apparently volatiles were accreted as a fractionated C3-like component. Consistent but subtle Cl-normalized abundance differences between eucrites (Serra de Magé < Moore County < Juvinas < Ibitira) result from crystal/liquid differentiation; Ibitira approximates the composition of an undifferentiated eucrite magma. The siderophile pattern retains little sign of nebular processes, but reflects planetary metal-silicate partition.The bulk composition of the eucrite parent body closely resembles that of H-chondrites, except for two features: moderately volatile elements (e.g. Na, K. Rb) are very much lower, apparently due to the accretion of more chondrule-like material; the metallic Fe-Ni content is only ~13%, even though total iron is very similar.     

Luna 20 soil: abundance of 17 trace elements

Luna 20 soil is remarkably similar to Apollo 16 soil, in its content of 17 mainly volatile or siderophile elements: Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Rb, Re, Sb, Se, Te, Tl, U, and Zn. Like other highland soils, it seems to contain an ancient meteoritic component of fractionated, volatile-poor composition. The bulk soil has a high $\text{Tl}\text{Cs}$ ratio (9.4 × 10^?2), similar to that in Apollo 16 soils (5.4 × 10^?2), but higher than that in samples from other sites (1.1 × 10^?2). It is severely contaminated with Ag, Cd, Re, and Sb, judging from a comparison with a 1.7 mg soil breccia sample from the coarse fraction of the soil.     

Abundance of 17 trace elements in carbonaceous chondrites

Seventeen trace elements (Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Rb, Re, Sb, Se, Te, Tl, U and Zn) were measured by neutron activation analysis in 8 C1 samples (1 Alais, 3 Ivuna, 4 Orgueil) and in 3 C2 samples (one each of Mighei, Murchison, Murray). The results show far less scatter than earlier literature data. The standard deviation of a single measurement from the mean of 8 C1 samples lies between 2 and 14 per cent, except for the following 4 elements: Au ±18 per cent, Ag ±22 per cent, Rb ±19 per cent and Br ±33 per cent. The first two probably reflect contamination and sample heterogeneity, the last two, analytical error. Apparently C1 chondrites have a far more uniform composition than some authors have claimed.The new data suggest significant revisions in cosmic abundance for the following elements (old values in parentheses): Zn 1250 (1500), Cd 1.51 (2.12), Ir 0.72 (0.43) atoms/10⁶ Si atoms. The Br value is also lower, 6.8 vs 20.6, but may be affected by analytical error.Relative to C1 chondrites, the C2 chondrites Mighei, Murchison and Murray are depleted in volatile elements by a factor of 0.508 ± 0.038, much more constant than indicated by oldor data. Ordinary chondrites also show a more uniform depletion relative to the new C1 data. The mean depletion factor of Sb, F, Cu, Ga, Ge, Sn, S, Se, Te and Ag is 0.227 ± 0.027 in H-chondrites. This constancy further strengthens the case for the two-component model of chondrite formation.     

Meteoritic trace elements in lunar rock 14321, 184

The 16 trace elements (Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Rb, Re, Sb, Se, Te, Tl and Zn) were measured by radiochemical neutron activation analysis in six samples of 14321, 184: microbreccia-2 (15), microbreccia-3 (14A, 16A and 19A), basaltic clast (1A), and light matrix material (9A). The 14321 microbreccias typically contain a siderophile-rich ancient meteoritic component, poor in volatiles, which is characterized by low $\text{Ir}\text{Au}$ and $\text{Re}\text{Au}$ ratios (0.25-0.38 and 0.34-0.50, respectively, normalized to Cl). This component also occurs in Apollo 12 KREEP glasses, norite fractions of Apollo 14 1–2 mm soils, Apennine Front breccias, and Cayley Formation material, and may represent ejecta from the Imbrian basin.The basaltic clast 14321, 184-1A closely resembles 14053 in trace element content, and both are 5–10 times higher than mare basalts in volatile trace elements (Br, Cd, Tl). The light matrix material contains 9.2 ± 0.5 per cent of microbreccias, judging from its siderophile content.     

Enstatite chondrites: Trace element clues to their origin

We have analyzed by RNAA 3 EH and 3 EL chondrites for 20 trace elements. Interelement correlations were examined visually and by factor analysis, to assess the effects of nebular fractionation and metamorphism.Refractory siderophiles (Ir, Os, Re) correlate with “normal siderophiles” (Ni, Pd, Au, Sb, and Ge) in EL's but not EH's; presumably these two element groups originally condensed on separate phases (CAI and metal), but then concentrated in metal during metamorphism. Sb and Ge are more depleted than the other three elements of the “normal” group, presumably by volatilization during chondrule formation.Volatiles are consistently more depleted in EL's than EH's, by factors >10× for the more volatile elements. Some of the stronger correlations are found for In-Tl, Tl-Bi, and Zn-Cd-In. These correlations are about equally consistent with predicted condensation curves for the solar nebula (especially for host phases with negative heats of solution, or for P = 0.1?1 atm) and with volatilization curves for artificially heated Abee, as determined by M E. Lipschutz and coworkers at Purdue. No decisive test between these alternatives is available at present, but the close correlation of Zn, Cd, In may eventually provide a crucial test.Factor analysis shows that 3 factors account for 93% of the variance; they seem to reflect volatile (F1), siderophile (F2), and chalcophile (F3) behavior. The element groupings agree largely with those recognized visually; they are listed with the inferred host phases. F1 (minor sulfide, probably ZnS): Zn, Cd, In, Br; F2 (CAI, later metal): Ir, Os. Re; F1, F2 (metal): Ni, Pd, Au, Ge, Sb; F3, F1 (FeS): Se, Te, Bi, Tl. These correlations differ to some extent from those obtained by Shaw (1974) in an earlier factor analysis, presumably because the new data are more homogeneous and extensive, especially for siderophiles. The new correlations also show that the cosmochemical behavior of some volatiles in E-chondrites differs from that predicted for ordinary chondrites, so that condensation curves for the latter are not strictly applicable.     

Ureilites: Trace element clues to their origin

Carbonaceous vein separates from Kenna and Haverö, as well as bulk Kenna, were analyzed by RNAA for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Pd, Os, Rb, Re, Sb, Se, Te, Tl. U, and Zn. The data are reviewed together with four earlier Chicago analyses of bulk ureilites. Linear regressions confirm the presence of two metal components, with the following Cl-normalized ratios: Ir/Ni = 14.6, ≤ 1; Ge/Ni = 5.4, 2.4; Au/Ni = 2.3, 0.9. The high-Ir component is enriched in vein separates and hence belongs to veins; the lowIr component belongs to the ultramafic rock. Vein material is enriched in all elements analyzed by us except Zn, and accounts for most of the C, noble gases, and presumably siderophiles in the meteorite. Most of the properties of ureilites apparently can be explained by the cumulate model of Berkley et al. (1980), with certain modifications. Comparison of ureilites with three other ultramafic rocks from different planets (Earth's mantle, lunar dunite, and Chassigny) suggests that the ureilite parent body had a primitive chondritic composition, similar to C3V chondrites but richer in metal and carbon. It melted, causing depletion of incompatibles to a mean abundance of ~0.02 × Cl and incomplete segregation of metal, FeS, and C. Fractional crystallization or melting of metal in the presence of S and C apparently can explain the fractionations of Ir, Re, Ni, Au, and perhaps Ge, obviating the need for extraneous sources of vein metal or unusual parent-body compositions. Noble gases from the parent material may have been retrapped in carbon during magmatism, provided the system was closed.     

R-mode factor analysis on enstatite chondrite analyses

R-mode factor analysis on 11 specimens of 9 enstatite chondrites, analysed for Ga, Se, Te, Zn, Cd, Bi, Tl, In, Sb, As, Co, showed three factors (rotated) to account for 92 per cent of the elemental variations (variance).Factor 1 dominates the first 8 elements listed, all volatile and mostly chalcophile: factors 2 and 3 express Sb and As variations, respectively, probably dependent on siderophile and less volatile behaviour; factors 1 and 2 contribute to Co.Factor-scores for individual meteorites indicate compositional differences (for these elements) between the E4 as against E5 and E6 stones (which are indistinguishable).Factor analysis of a second suite of 10 specimens analysed for Zn, Cd, Bi, Tl, In, Ag, Rb, Cs showed one factor to account for 93 per cent of the elemental variance. This expresses the association of Ag, Rb, Cs with the volatile-chalcophile factor.     

四川省癌死亡率与土壤环境中化学元素的关系

利用中国癌死亡率与土壤坏境中化学元素的相关性成果，研究了四川省癌死亡率与土壤环境中化学元素：As、Cd、Co、Cu、Hg、Mn、Ni、Pb、Se、V、Li、Na、K、Rb、Cs、Mg、Ca、Sr、Ba、B、Al、Ga、In、Tl、Sc、Y、La、Ce、Pr、Nd、Tb、Dy、Ho、Er、Tm、Yb、Lu、Th、U、Sn、Ti、Zr、Hf、Sb、Bi、Ta、Te、Mo、W、Br、I、Fe等52个元素含量的关系     

Pedo-geochemical baseline content levels and soil quality reference values of trace elements in soils from the Mediterranean (Castilla La Mancha, Spain)

To evaluate trace element soil contamination, geochemical baseline contents and reference values need to be established. Pedo-geochemical baseline levels of trace elements in 72 soil samples of 24 soil profiles from the Mediterranean, Castilla La Mancha, are assessed and soil quality reference values are calculated. Reference value contents (in mg kg^?1) were: Sc 50.8; V 123.2; Cr 113.4; Co 20.8; Ni 42.6; Cu 27.0; Zn 86.5; Ga 26.7; Ge 1.3; As 16.7; Se 1.4; Br 20.1; Rb 234.7; Sr 1868.4; Y 38.3; Zr 413.1; Nb 18.7; Mo 2.0; Ag 7.8; Cd 4.4; Sn 8.7; Sb 5.7; I 25.4; Cs 14.2; Ba 1049.3; La 348.4; Ce 97.9; Nd 40.1; Sm 10.7; Yb 4.2; Hf 10.0; Ta 4.0; W 5.5; Tl 2.3; Pb 44.2; Bi 2.2; Th 21.6; U 10.3. The contents obtained for some elements are below or close to the detection limit: Co, Ge, Se, Mo, Ag, Cd, Sb, Yb, Hf, Ta, W, Tl and Bi. The element content ranges (the maximum value minus the minimum value) are: Sc 55.0, V 196.0, Cr 346.0, Co 64.4, Ni 188.7, Cu 49.5, Zn 102.3, Ga 28.7, Ge 1.5, As 26.4, Se 0.9, Br 33.0 Rb 432.7, Sr 3372.6, Y 39.8, Zr 523.2, Nb 59.7, Mo 3.9, Ag 10.1, Cd 1.8, Sn 75.2, Sb 9.9, I 68.0, Cs 17.6, Ba 1394.9, La 51.3, Ce 93.5, Nd 52.5, Sm 11.2, Yb 4.2, Hf 11.3, Ta 6.3, W 5.2, Tl 2.1, Pb 96.4, Bi 3.0, Th 24.4, U 16.4 (in mg kg^?1). The spatial distribution of the elements was affected mainly by the nature of the bedrock and by pedological processes. The upper limit of expected background variation for each trace element in the soil is documented, as is its range as a criterion for evaluating which sites may require decontamination.     

Aubrites and diogenites: Trace element clues to their origin

We have analyzed by RNAA 25 aubrite and 9 diogenite samples for 13 to 29 siderophile, volatile, and lithophile trace elements. Both meteorite classes show a typically igneous siderophile element pattern, with Ir, Os, Re, Ge more depleted than Au, Ni, Pd, Sb. But aubrites tend to have about 10 × higher abundances (10^?3 ? 10 ^{? 4} × Cl for the first 4 and 10^?2?10^?3 × Cl for the last 4 siderophiles), apparently reflecting smaller metal/silicate distribution coefficients at lowerf(O₂), or less complete segregation of metal. Se is surprisingly abundant in aubrites (up to 0.4 × Cl), but Te is less so ($\text{Se}\text{Te}\text{? 5 × Cl}$), apparently due to its stronger siderophile character. Other volatiles (Ag, Zn, In, Cd, Bi, T1) show depletions intermediate between lunar dunite and the Earth's mantle.Of 7 aubrites analyzed for REE (Ce, Nd, Eu, Tb, Yb, Lu), 6 are depleted in REE (0.08?0.5 × Cl) and 5 show negative Eu anomalies (the exceptions are Bishopville and Mt. Egerton silicate). This supports an igneous origin, as already noted by Boynton and Schmitt (1972). No samples of the complementary, basaltic and feldspathic rocks have been found thus far, but one of our samples of Khor Temiki dark is a candidate for the basalt. It is 5?7 × enriched in REE and only slightly less so in Rb, Cs, and U. Though shocked and enriched in siderophiles to ~0.05 × Cl, it apparently represents a new meteorite class.Three diogenites analyzed for REE show very diverse patterns, from strongly depleted in light REE for Tatahouine (Ce = 0.01 × Cl) to flat for Garland (~2.5 × Cl). The data confirm the trends found by Fukuokaet al. (1977) as well as their interpretations.Factor analysis shows several parallel groupings for aubrites and diogenites: siderophiles (Re, Ir, Os, Pd, Ge), chalcophiles (Se, Te), volatiles (Ag, In, Tl) and incompatibles (U, REE, and Cs or Rb). But there are some differences for elements such as Ni, Sb, Cd, Bi, Au, and Zn, most of which behave more sensibly in aubrites than in diogenites.Several element pairs that differ greatly in volatility (Cs-U, Ge-Ir) correlate closely in aubrites, in approximately Cl-chondrite proportions. These correlations, and other lines of evidence, suggest strongly that aubrites originated by igneous processes in their parent body, not by direct nebular condensation. The source material may have resembled EL chondrites in oxidation state and depletion of refractories, metal, and volatiles.     

Volatile and siderophile trace elements in anorthositic rocks from Fiskenaesset. West Greenland: comparison with lunar and meteoritic analogues

Seventeen trace elements (Ag, Au, Bi, Br, Cd, Cs, Ge, Ir, Ni, Rb, Re, Sb, Se, Te, Tl, U, Zn) were analyzed by radiochemical neutron activation and 13 other elements (Ce, Co, Cr, Eu, Fe, Hf, La, Lu, Na, Sc, Sm, Tb, Yb) by instrumental neutron activation in a total of 12 rocks from the layered anorthositic complex at Fiskenaesset, West Greenland and in the plagioclase-rich unbrecciated eucrite, Serra de Magé.Garnet anorthosite 84428, which has an unusually sodic plagioclase, is spectacularly enriched in Cs, K, Rb. Tl and, to a lesser degree, Te. This appears to be the result of later metasomatism and not a reflection of fractionation trends within the anorthositic complex. For the remaining Fiskenaesset rocks, a factor analysis yields 5 principal factors for linear data for 22 elements and 6 factors for data transformed (log, ³√, √) to give approximately normal distributions. Linear correlations are controlled by high values, whereas the logarithmic transform increases the influence of the lowest values. Enrichment of several elements in chromitite 132022 underlies linear Factor 1. Six of these elements Co, Cr, Fe, Ir, Ni, Zn and possibly Re are probably hosted by chromite. In other zones of the intrusion, different fractionation trends may be more important, since in the transformed analysis these elements divide between Factor 1 (Co, Zn, Ni, Fe) and Factor 4 (Ir, Cr and also Au). Linear Factor 2 reflects the strong mutual correlation between Tl, Rb and An, the anorthite content of plagioclase. Transformed Factor 3 emphasizes the anticorrelation of Na and Sm with An. The positive correlations of Cs, U and Ge (linear Factor 3; transformed Factor 2) are largely due to their concentration in later crystallizates, but enrichment in lower zone gabbros of high An content perhaps indicates concentration in minor or accessory cumulate minerals. Flat chondrite-normalized rare earth element patterns in several anorthosites (except for a small positive Eu anomaly) suggests that the Fiskenaesset magma was relatively unfractionated.Factor 4 (linear) and Factor 5 (transformed) reflects the geochemical coherence of Se and Te. The sympathetic enrichment of Sb and Cd in 3 rocks, resulting in Factor 5 (linear) and Factor 6 (transformed) may be due to the lack of a suitable Zn sulfide host for Cd.In 3 rocks of true anorthosite composition, 8 volatile elements show rather constant abundance when normalized to Cl chondrites (mean 4.2 ± 0.4% Cl), possibly suggesting that volatile-rich material was accreted late in the Earth's formation, perhaps after core segregation. These anorthosites are higher than lunar anorthosite 15415 by a factor of 58 ± 9 in volatile elements. Siderophile and chalcophile elements are much more variable in Cl-normalized abundances in both lunar and terrestrial anorthosites, but surprisingly give somewhat similar Earth/Moon abundance ratios.Volatile elements in terrestrial oceanic basalts and lunar mare basalts are not as uniformly abundant as in anorthosites. but nevertheless yield a similar Earth/Moon ratio of 44 ± 8.Volatile elements in Serra de Magé are more abundant than in lunar anorthosites, but lower than in terrestrial equivalents, averaging (3.6 ± 0.8) × 10^?3C1.     

流域上游基岩与下游冲积平原土壤化学组成的对比

对海河水系流域、鄱阳湖水系流域上游的基岩与下游的冲积平原土壤之间化学组成的对比研究显示,下游冲积物土壤的化学组成明显地受源岩成分、形成过程和形成环境的影响。流域上游基岩的一些特征元素在冲积物土壤中被明显地继承,如海河流域基岩和土壤中的CO2、CaO、MgO、FeO、Sr,鄱阳湖流域基岩和土壤中的W、Sn、Bi、U、Th、Pb、Rb、Tl、As、Sb、Se、Hg、Nb、Ta、Hf、B、Be、Ge、Pt、Pd、Y。受形成过程和形成环境的影响,处于暖温带半湿润季风气候下的海河流域冲积平原土壤以极富集CO2、CaO、Na2O、Cl,显著富集MgO、FeO、Sr,富集P、S为特征;而处于亚热带湿润季风气候下的鄱阳湖流域冲积平原土壤则以显著富集Hg、Se和富集Al2O3、Fe2O3H2O^＋、W、Sn、Bi、Mo、U、Th、Pb、Rb、Cs、Tl、Li、Be、B、Ga、Ge、Nb、Ta、Zr、Hf、As、Sb、Co、Cr、Ti、V、Zn、Pt、Pd、REE、Y为特征。无论是海河流域还是鄱阳湖流域的冲积平原土壤,均富集As、Sb、Hg、B、Cl、W、Sn、Bi、Pb、Se、Ge、Li、Cs、Cu、Au、Fe2O3、V、Cr、Ni、Zr、Hf、Y。