A kinetic approach to describe trace-element distribution between particles and solution in natural aquatic systems

The partitioning of radioactive trace elements between seawater and particulate matter from surface sediments and sediment traps was investigated in laboratory experiments. For the elements Na, Zn, Se, Sr, Cd, Sn, Sb, Cs, Ba, Hg, Th and Pa (group I) constant distribution coefficients (K_d) were found after a few days of equilibration, whereas the elements Be, Mn, Co and Fe (group II) showed an increasing K_d over the whole time of observation of 108 days. The time dependence of K_d is described by an adsorption-desorption equilibrium (group I elements), followed by a lattice transport reaction step (group II elements). The reaction rate constants are compared to Mn oxidation rates and to adsorption rate constants derived from in situ measurements of the $\text{U}\text{Th}$ disequilibrium as available from literature.     

An ion microprobe study of the partitioning of trace elements between clinopyroxene and liquid in the system diopside-albite-anorthite

The partitioning of trace elements (Sc, Ti, Sr and Sm) between diopsidic clinopyroxene and liquid was studied experimentally in the system diopside-albite-anorthite at 1250°C, 1300°C and 1345°C at 1 atm. Twelve different bulk compositions were selected to study the effects of temperature and chemical composition. A Cameca ion microprobe was used to determine trace element concentrations in both clinopyroxene and liquid. Experiments of different run duration $\text{1}\text{4}\text{8}\text{?}$ days) showed that equilibrium was approached in less than 4 days at 1275°C. Equilibrium was also evaluated by a reversal run. A series of runs of constant bulk composition but with variable trace element contents showed that Henry's Law was obeyed over concentration ranges of the trace elements similar to those encountered in natural systems. The partition coefficients show significant ranges: Sc, 0.345~2.61; Ti, 0.084~0.214; Sr, 0.075~0.136; Sm, 0.054~0.328; the values are comparable with those obtained experimentally by other investigators. The partition coefficients vary as a function of both temperature and chemical composition. The experimental results are discussed in terms of exchange equilibria using the Bottinga-Weill silicate melt model. It is demonstrated that analytical uncertainties of both major and trace elements play an important role in understanding trace element exchange equilibria; propagation of analytical errors in the thermodynamic treatment is equally important.     

Al-Sm-Eu-Sr systematics of eucrites and Moon rocks: Implications for planetary bulk compositions

Analysis of the Eu and Sr “anomalies” of eucrites and lunar rocks allows constraints to be placed on the bulk compositions of the eucrite parent body (EPB) and the Moon. The elements Al, REE, and Sr, all are essentially incompatible with the major minerals of these small, low-?(O₂) bodies, except for plagioclase, into which Al, Sr, and Eu tend to concentrate. Therefore, the hypothesis that Al, REE, and Sr in the EPB and the Moon are all in proportions close to those in the bulk solar system (i.e., chondrites) leads to certain predictions about the concentrations of these elements in samples affected by plagioclase fractionation. The predictions are almost ideally fulfilled by eucrites and lunar samples. For the EPB, the ratios $\text{REE}\text{Al}$, $\text{Sr}\text{Al}$, and $\text{Sr}\text{REE}$ are constrained to be probably within 10%, almost certainly within 20%, of the chondritic ratios. For the more complicated Moon, the constraints are less precise: $\text{REE}\text{Al}$ is very probably within 25% of chondritic; $\text{Sr}\text{Al}$ and $\text{Sr}\text{REE}$ are probably within 35% of chondritic. These findings are proof that there is a strong similarity between the bulk compositions of the planets and the compositions of chondritic meteorites.The eucrites' Sm-Eu-Sr systematics are also valuable sources of constraints on the distribution coefficients for Eu and Sr into plagioclase, at low ?(O₂). From the slope of data for noncumulate eucrites on a Eu-Sm plot, D(Eu,pl/liq) can be inferred to be 1.1_?0.1^0.2. From the slope on a Sr-Sm plot, D(Sr,pl/liq)) can be inferred to be 1.5 ± 0.3. In the case of D(Eu), this is in excellent agreement with experimental data. In the case of D(Sr), the empirical result is probably more appropriate for eucritic systems than most experimental data, which, due to compositional effects, scatter widely.     

Anomalies in rare earth distributions in seawater: Gd and Tb

We have measured profiles of the rare earth elements (REE) in Atlantic and Pacific Ocean waters. The data, normalized versus shales, exhibit a pronounced anomaly in Gd relative to its neighbors Eu and Tb in the REE series such that the Gd concentrations are high by 30–50%. Closer inspection reveals that the anomaly is made up of both elevated Gd and depressed Tb concentrations, likely associated with solution chemistry shifts in the transition from an exactly half filled 4f electron shell. Anomalies in Gd and Tb solution complexation are also indicated by the Turner-Whitfield-Dickson speciation model. The overall trend of heavy REE(III) enrichment in seawater and the $\text{Gd}\text{Tb}$ anomaly described here tend to support scavenging as an important removal mechanism for the REE from seawater.     

Sulphur content and sulphur isotope composition of orange and black glasses in Apollo 17 drive tube 74002/1

The sulphur contents and δ³⁴S values have been determined for the bulk and various grain size fractions of three $\text{74002}\text{1}$ lunar drive tube samples. The sulphur contents of the bulk samples ate much lower than those of other lunar soils. These samples, along with the surface orange soil 74220 analysed previously, show an increase of sulphur concentration with decreasing particle size which is more marked than for other soils and indicates that the orange and black glass droplets have a coating enriched in sulphur and other volatile elements.In sharp contrast with other soils, the orange and black glasses have slight positive δ³⁴S values for large particles while the smallest particle sizes show negative δ³⁴S values. This indicates that the coating of the glassy droplets is enriched in isotopically light sulphur. These observations favour the theory that the orange and black glasses were generated by a volcanic fire fountain.The anomalously high δ³⁴S values of the fine fractions of the core bottom sample, 74001-135, combined with the results of an acid leaching experiment, indicate that these fractions are contaminated, possibly by a mature soil of high sulphur content and relatively positive δ³⁴S value.     

Stable isotopic investigations of early development in extant and fossil chambered cephalopods I. Oxygen isotopic composition of eggwater and carbon isotopic composition of siphuncle organic matter in Nautilus

Eggwaters from the chambered cephalopod Nautilus are depleted in both ¹⁸O and deuterium relative to ambient seawater. Eggwaters from six other species, including the related chambered cephalopod Sepia, do not show such depletion. These observations indicate that the previously observed step towards more positive $\text{δ}{}^{18}\text{O}$ values in calcium carbonate laid down after Nautilus hatches, relative to carbonate precipitated prior to hatching, can be explained by equilibration of the carbonate with water in the egg before hatching and with seawater after hatching. The presence of an oxygen isotope difference between eggwater and seawater for Nautilus and its absence for Sepia suggest that hatching will be recorded in the $\text{δ}{}^{18}\text{O}$ values of shell carbonates for some but not all extinct and extant chambered cephalopods.The $\text{δ}{}^{13}\text{C}$ values of the organic fraction of the siphuncle in Nautilus do not show any consistent pattern with regard to the time of formation before or after hatching. This observation suggests that the minimum in $\text{δ}{}^{13}\text{C}$ values previously observed for calcium carbonate precipitated after Nautilus hatches is not caused by a change in food sources once the animal becomes free-swimming, as has been suggested.     

Variations in composition and δ18O values within the Kaffo albite—Riebeckite granite of Liruei Complex,Younger Granites of Nigeria

The peralkaline Kaffo albite—riebeckite granite is an albitised, low-temperature intrusion in Liruei Complex, one of the oldest of the ring-complexes in the Younger Granite province of Nigeria. Analyses of borehole samples from different parts of the intrusion show it to be compositionally heterogeneous, especially in respect of Si, Al, Na, K and F distribution and this, in part, can be correlated with the variable degree of albitisation. Isotopically the granite is a normal plutonic type with δ¹⁸ O values of $\text{+ 8.1 ± 0.2‰}$, and albitisation does not seem to have been accompanied by exchange of isotopes between albitising fluid and the granite. Co-existing riebeckitic-arfvedsonite and aegirine pairs from borehole samples show extreme enrichment in Na and Fe; the amphibole also shows considerable substitution of Fe by Ti, Zn and Mn, and of OH by F. Isotopically the amphibole and pyroxene are different from others, having low, variable δ¹⁸ O values (+5.3–+6.4 and $\text{+4.4–+5.1‰}$, respectively), and the fractionation value Δ Px — Am is always large, negative and constant (—$\text{1.2 ± 0.2‰}$). The low δ¹⁸ O values are considered to be due to special features of the crystal chemistry of the alkali amphiboles and pyroxenes, and the spread of each set of values may be due to sub-solidus isotope exchange between the minerals and albitising fluid.     

Sm-Nd in marine carbonates and phosphates: Implications for Nd isotopes in seawater and crustal ages

This study explores the possibility of establishing Nd isotopic variations in seawater over geologic time. Calcite, aragonite and apatite are examined as possible phases recording seawater values of ?_Nd. Modern, biogenic and inorganically precipitated calcite and aragonite from marine environments were found to have Nd concentrations of from 0.2 to 70 ppb, showing that primary marine CaCO₃ contains little REE and that Nd/Ca is not greatly enhanced relative to seawater during carbonate precipitation. Very young marine limestone and dolomite containing no continental detritus have ~200 ppb Nd. All the carbonates are LREE enriched ($\text{?0.16 ≤f}{}^{\mathrm{<mtext>Sm</mtext><mtext>Nd</mtext>}}\text{≤?0.45}$). Modern and very young Atlantic and Pacific carbonates have ?_Nd in the range of shallow Atlantic and Pacific seawater respectively, implying that they derive their REE from local seawater. The Nd in well preserved carbonate fossils is ≤4 × 10⁴ ppb, much greater than in their modern counterparts but like the high values found for carbonates in other studies. We believe the high REE contents (at the 500 ppb level) in some detritusfree carbonates are due to REE-rich Fe-hydroxide in/on the carbonate. In favorable cases, such material may record seawater ?_Nd values, however introduction of extraneous REE may obscure the original isotopic composition of pure CaCO₃ because of its very low intrinsic primary REE abundance.Modern biogenic apatite is also shown to have very low REE content (<150 ppb Nd) but appears to quickly scavenge REE from seawater. Inorganically precipitated apatite from phosphorites has high concentrations of seawater-derived REE. Young phosphorite apatite from the Atlantic and Pacific oceans has ?_Nd in the range of the seawater from these oceans. Older apatite samples of similar age from different localities bordering common oceans record similar values of ?_Nd(T). Sedimentary apatite has ?_Sr(T) values in good agreement with the curves for ${}^{87}\text{Sr}{}^{86}\text{Sr}$ of seawater as a function of time. Individual conodonts from a single formation yield the same ?_Sr(T) and ?_Nd(T). Other workers have shown that sedimentary apatite preserves seawater REE patterns. These characteristics suggest that sedimentary apatite can be used to determine ?_Nd(T) in ancient seawater. The seawater values so inferred range between ?1.7 and ?8.9 over the last 700 my and lie in the range of modern seawater, showing no evidence for drastic changes. High values of seawater ?_Nd(T) in the Triassic and latest Precambrian may correlate with the breakup of large continental landmasses. The initial ?_Nd(T) =?15.0 of a 2 AE old phosphorite implies the presence of ~ 1.5 AE old continental crust at 2 AE ago. The approach outlined here can be used to constrain the age of the exposed crust as a function of time.     

Effet de la température sur les distributions de Na,Rb et Cs entre la sanidine,la muscovite,la phlogopite et une solution hydrothermale sous une pression de 1 kbar

The distribution of trace amounts of Na, Rb and Cs, between muscovite, phlogopite, sanidine and hydrothermal solution have been studied by ion exchange in a temperature range from 400 to 800°C.These distributions have been expressed with a partition ratio P^aq?m_x = $\text{(}\text{X}\text{K}\text{)}{}^{\mathrm{aq}}\text{(}\text{X}\text{K}\text{)}{}^{\mathrm{m}}$ (where X is Na, Rb or Cs).In the case of Na and Cs in muscovite, even for the dilute solutions, the ratio P^aq?m_x is not the equilibrium constant k_x of exchange reactions. In other cases, P^aq?m_x does not depend on the trace alkali ion concentration in silicates (X) and is equal to k_x. Variations of P_x or k_x with T are greater for Na and Cs than for Rb. Generally, k_x decreases with increase in T. The function log $\text{P}{}_{\mathrm{x}}\text{= f(}\text{1}\text{T}\text{)}$ is not linear for Na or Cs, but in the case of Rb, $\text{f(}\text{1}\text{T}\text{)}$ is linear and the standard enthalpy and entropy of exchange reactions have been estimated by applying the Arrhenius relation.The distribution relations obtained between silicate and vapour phase permit the determination of distributions of Na, Rb and Cs between two minerals mI and mII, relative to K. These have been expressed with the partition ratio Q_x =$\text{(}\text{X}\text{K}\text{)}{}^{\mathrm{mI}}\text{(}\text{X}\text{K}\text{)}{}^{\mathrm{mII}}$. Variations of Q_x with T are not remarkable, and even for Rb between phlogopite and feldspar are negligible. Nevertheless, one may use the distributions of Rb and Cs between muscovite and feldspar for geothermometry. Experimental results have been applied to some rocks by effecting corrections from the major element composition of the natural minerals. Estimated temperatures are near to 400°C in the granites and pegmatite studied here.     

Alkali differentiation in LL-chondrites

The LL-group chondrites Krähenberg (Krbg) and Bhola are heterogeneous agglomerates containing a variety of lithic fragments and chondrules as well as crystal fragments. The $\text{Fe}\text{Fe}$ + Mg content of most olivine grains is uniform (Fa₂₈), although a few with distinctly lower Fe contents were found (Fa₁₉). Both meteorites contain large, cm-sized, fragments with high enrichments of K (~12×), Rb (~45×) and Cs (~70×) relative to LL-chondrites, while the REE concentrations are normal (except for a negative Eu anomaly); Na and Sr are depleted (~0.5×) and the $\text{Na}\text{K}$ weight ratio is 0.33 compared to 11 in the host. However, there is no difference in the sum of Na + K atoms. Also, the major elements, Si, Al, Mg, Ca and Fe, are nearly the same in fragments as in the host material. The K-rich igneous lithic fragments have a microporphyritic texture of euhedral to skeletal olivines in a partly devitrified glass with ~4% K₂O. The main pans of both Krbg and Bhola contain mesostasis glasses in porphyritic chondrules and lithic fragments with varying K content (0.1–8.6% K₂O) and $\text{Na}\text{K}$ ratios (0.2–100). Crystalline plagioclase is depleted in K with an average $\text{Na}\text{K}$ ratio of 22, i.e. higher than that for ordinary chondritic plagioclase, 8.4. Olivines in the large, K-rich fragments and in the host meteorites have the same iron content (Fa₂₈), indicating that both formed under the same oxygen fugacity and probably on the same parent body.Conceivable mechanisms for the formation of the K-rich rocks from normal LL-chondrite parent material are: 1, magmatic differentiation: 2. Na-K exchange via a vapor phase; 3. silicate liquid immiscibility; 4. volatilization and condensation in impact events. Process 2 appears most feasible for forming a rock enriched only in K and heavier alkalies and depleted in Na without noticeably changing other elements including the REE.     

The effect of pressure on the ionization of boric acid in sodium chloride and seawater from molal volume data at 0 and 25°C

The apparent molal volume, φ_V of boric acid, B(OH)₃ and sodium borate, NaB(OH)₄, have been determined in 35%. salinity seawater and 0·725 molal NaCl solutions at 0 and 25°C from precise density measurements. Similar to the behavior of nonelectrolytes and electrolytes in pure water, the φ_V of B(OH)₃ is a linear function of added molality and the φ_V of NaB(OH)₄ is a linear function of the square root of added molarity in seawater and NaCl solutions. The partial molal volumes, $\text{V}\text{?}\text{1}$, of B(OH)₃ and NaB(OH)₄ in seawater and NaCl were determined from the φ_V's by extrapolating to infinite dilution in the medium. The $\text{V}\text{?}\text{1}$ of B(OH)₃ is larger in NaCl and seawater than pure water apparently due to the ability of electrolytes to dehydrate the nonelectrolyte B(OH)₃. The $\text{V}\text{?}\text{1}$ of NaB(OH)₄ in itself, NaCl and seawater is larger than the expected value at 0·725 molal ionic strength due to ion pair formation [Na⁺ + B(OH)₄^? → NaB(OH)₄⁰]. The volume change for the formation of NaB(OH)₄⁰ in itself and NaCl was found to be equal to 29·4 ml mol^?1 at 25°C and 0·725 molal ionic strength. These large $\text{Δ}\text{V}\text{?}\text{1}$'s indicate that at least one water molecule is released when the ion pair is formed [Na⁺ + B(OH)₄^? → H₂O + NaOB(OH)₂⁰]. The observed $\text{V}\text{?}\text{1}$ in seawater and the $\text{Δ}\text{V}\text{?}\text{1}$ (NaB⁰) in water and NaCl were used to estimate $\text{Δ}\text{V}\text{?}\text{1 (MgB}{}^{\mathrm{+}}\text{) = Δ}\text{V}\text{?}\text{1 (CaB}{}^{\mathrm{+}}\text{) = 38·4 ml mol}{}^{\mathrm{?1}}$ for the formation of MgB⁺ and CaB⁺. The volume change for the ionization of B(OH)₃ in NaCl and seawater was determined from the molal volume data. Values of $\text{Δ}\text{V}\text{?}\text{1 = ?29·2 and ?25·9 ml mol}{}^{\mathrm{?1}}$ were found in seawater and $\text{Δ}\text{V}\text{?}\text{1 = ?21·6 and ?26·4}$ in NaCl, respectively, at 0 and 25°C. The effect of pressure on the ionization of B(OH)₃ in NaCl and seawater at 0 and 25°C determined from the volume change is in excellent agreement with direct measurements in artificial seawater (culberson and Pytkowicz, 1968; Disteche and Disteche, 1967) and natural seawater (Culberson and Pytkowicz, 1968).     

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.     

Alteration of basaltic glass: Mechanisms and significance for the oceanic crust-seawater budget

Alteration of basaltic glass to palagonite is characterized by a nearly isomolar exchange of SiO₂, Al₂O₃, MnO, MgO, CaO, Na₂O, P₂O₅, Zn, Cu, Ni, Cr, Hf, Sc, Co and REE for H₂O and K₂O, whilst TiO₂ and FeO are passively accumulated during removal of the remaining cations. The network forming cations Al and Si are removed from the glass in proportion to the gain in Ti and Fe, whilst the other cations do not show a significant relationship to the amount of Ti and Fe accumulation. Sr isotopic data show that during palagonite formation approximately 85% of the basaltic Sr is lost to the hydrous solutions and 40% of seawater Sr is added to the glass, yielding an average loss of the same order of magnitude as of the network forming cations. Losses and gains of oxides yield an average increase of +105% TiO₂.K, Rb, and Cs show high increases, but $\text{K}\text{Rb}$ and $\text{K}\text{Cs}$ ratios indicate two different alteration processes: (1) formation of palagonite involves a drastic decrease in these ratios, indicating structural similarities between palagonite and smectite; (2) surface alteration of glass is characterized by an increase in $\text{K}\text{Rb}$ and $\text{K}\text{Cs}$ ratios, probably best interpreted as sorption of alkalies in ratios approximating those of seawater.The total fluxes involved in alteration of glass in the upper portion of the oceanic crust are estimated from the modal abundance of palagonite in the oceanic crust and the abundance of the vein materials smectite and carbonate. Smectite and carbonates act as a sink for a significant portion of the elements liberated up during alteration of basaltic glass except for Na and Al, which are probably taken up by zeolites and/or albite, possibly hidden in the macroscopic estimate of carbonate. Formation of the observed quantity of secondary phases requires additional sources for Si, Fe. Ca and K. K is provided in excess from the inflowing seawater at reasonable water/rock ratios. The remaining excess Ca, Si and Fe required may be derived by alteration of interstitial glass and breakdown of anorthite rich plagioclase and titano-magnetite, and/or by supply of deeper seated metamorphic reactions.     

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.     

Chemical composition of Luna 20 rocks and soil and Apollo 16 soils

The abundances of 24 major, minor and trace elements have been measured by INAA in Luna 20 metaigneous rocks 22006,1 and 22007,1, breccia 22004 and soil 22001,9 and in Apollo 16 soils 62281, 66041 and 66081. An additional 12 trace meteoritic and non-meteoritic elements have also been determined in 22001 and 62281 soils by RNAA. The bulk compositions of L 20 and Ap 16 rocks and soils show close similarity between the two highland sites. There are appreciable differences in bulk compositions between the L 20 highland and the L 16 mare site (120 km apart), suggesting little intermixing of rocks and soils from either site. Luna 20 rocks 22006 and 22007 are nearly identical in chemical composition to Ap 16 metaigneous rocks 61156 and 66095. Luna 20 rocks are feldspathic and are similar to low K-type Fra Mauro basalts. Such rocks and anorthositic gabbros appear to be the major components in highland soils. Luna 20 soil can be distinguished from Ap 16 soils by lower abundances of Al₂O₃, CaO and large ion lithophilic elements. Luna 20 breccia 22004 probably is compacted soil. All L 20 samples show negative Eu anomalies with $\text{Sm}\text{Eu}$ ratios of 5.8, 7.2, 3.9 and 3.3 for rocks 22006, 22007, breccia 22004 and soil 22001, respectively. Norite-KREEP is insignificant, ≤1 per cent, at the L 20 highland site. The derivation of the L 20 soil may be explained by ≈33 per cent of L 20 metaigneous rocks and ≈ 65 per cent anorthositic gabbroic breccia rocks like 15418 (with a positive Eu anomaly) and ≈ 2 per cent meteoritic contributions. Interelement correlations observed previously for maria are also found in highland samples. Luna 20 and Ap 16 soils are low in alkalis. Both soils show an apparent Cd-Zn rich component similar to that observed at the mare sites and high 11 abundances relative to mare sites. The Ap 16 (62281) soil contains a fractionated meteoritic component (probably ancient) of ≈ 1.5 per cent in addition to ≈ 1.9 per cent Cl like material. Luna 20 soil may simply contain 1.9 per cent Cl equivalent.     

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.     

The distribution of trace elements in carbonaceous chondrites

12 carbonaceous chondrites, amongst them representatives of nearly all known petrologic types were analyzed for twenty trace elements by spark source mass spectrography combined with the isotope dilution method. Data on different element groups (refractory, moderately volatile and volatile) show that the distribution of the trace elements in the carbonaceous chondrites, with the exception of Renazzo, can be well explained by Anders' two-component model. This is also valid for the highly metamorphosed CV5 chondrite Karoonda.Furthermore, it is observed that the $\text{Zr}\text{Hf}$-ratios in the carbonaceous chondrites increase with increasing petrologic type which is interpreted as the result of mixing two components with different $\text{Zr}\text{Hf}$-ratios     

Rare earth element geochemistry of Archean metasedimentary rocks from Kambalda,Western Australia

Archean sedimentary rocks of very limited lateral extent from horizons within basaltic and ultramafic volcanic sequences at Kambalda, Western Australia, are extremely variable in major elements, LIL and ferromagnesian trace element compositions. The REE patterns are uniform and do not have negative Eu anomalies. Two samples have very low total REE abundances and positive Eu anomalies attributed to a very much greater proportion of chemically deposited siliceous material. Apart from these two samples, the Kambalda data are similar to REE abundances and patterns from Archean sedimentary rocks from Kalgoorlie, Western Australia and to average Archean sedimentary rock REE patterns. These show a fundamental distinction from post-Archean sedimentary rock REE patterns which have higher $\text{La}\text{Yb}$ ratios and a distinct negative Eu anomaly.     

Geochemistry of Archean shales from the Pilbara Supergroup,Western Australia

Archean clastic sedimentary rocks are well exposed in the Pilbara Block of Western Australia. Shales from turbidites in the Gorge Creek Group (ca. 3.4 Ae) and shales from the Whim Creek Group (ca. 2.7 Ae) have been examined. The Gorge Creek Group samples, characterized by muscovite-quartzchlorite mineralogy, are enriched in incompatible elements (K, Th, U, LREE) by factors of about two, when compared to younger Archean shales from the Yilgarn Block. Alkali and alkaline earth elements are depleted in a systematic fashion, according to size, when compared with an estimate of Archean upper crust abundances. This depletion is less notable in the Whim Creek Group. Such a pattern indicates the source of these rocks underwent a rather severe episode of weathering. The Gorge Creek Group also has fairly high B content (85 ± 29 ppm) which may indicate normal marine conditions during deposition.Rare earth element (REE) patterns for the Pilbara samples are characterized by light REE enrichment ($\text{La}{}_{\mathrm{N}}\text{Yb}{}_{\mathrm{N}}\text{≥ 7.5}$) and no or very slight Eu depletion ($\text{Eu}\text{Eu}{}^1\text{= 0.82 – 0.99}$). A source comprised of about 80% felsic igneous rocks without large negative Eu-anomalies (felsic volcanics, tonalites, trondhjemites) and 20% mafic-ultramafic volcanics is indicated by the trace element data. Very high abundances of Cr and Ni cannot be explained by any reasonable provenance model and a secondary enrichment process is called for.