Helium,neon, and argon in the iron meteorites Dongling,Nantan and Ningbo

The light noble gases He, Ne and Ar have been measured in the iron meteorites Dongling, Nantan and Ningbo. Dongling and Ningbo show a deficit of cosmic-ray that produced³He of ca. 30% and 10%, respectively, which is argued to be caused by the loss of³H (tritium) from the meteoroids during the time of their exposure to the cosmic radiation. Nantan has the lowest content of noble gases as yet reported for any iron meteorite. Cosmogenic³He and³⁸Ar are only about 1/5000 of those in Dongling which has particularly interesting implications if the two meteorites belong to the same fall^[2]. In addition, Nantan contains nonspallogenic⁴He which we believe to be of radiogenic origin. This radiogenic⁴He, together with a U-content of 2.6×10⁻¹¹ g/g^[20] yields a⁴He retention age close to the cosmic-ray exposure age of Dongling. If Dongling and Nantan were part of the same meteoroid^[2], this result would indicate that He retention in the meteoroid age were 4,500 Ma, a U-content of less than 7.2×10⁻¹³ g/g is required to explain the non-cosmogenic₄He present. An upper limit to the number of transuranium or superheavy-element atoms which have decayed by α-emission in Nantan since onset of He retention is 2×10¹⁰ per gram.     

Trapped solar wind noble gases and exposure age of Luna 16 lunar fines

He, Ne, Ar, Kr and Xe concentrations and isotopic abundances were measured in three bulk grain size fractions prepared from sample L-16-19, No. 120 (C level, 20–22 cm depth) returned by the Luna 16 mission. The expected anticorrelation between the concentrations of trapped solar wind noble gases and grain size is observed. Elemental abundances of solar wind trapped noble gases are similar to those previously found in corresponding grain size fractions of the Apollo 11 and 12 fines. The trapped ratio ${}^4\text{He}{}^{20}\text{Ne}$ varies in the soils from different lunar maria due to diffusion losses. A rough correlation of ${}^4\text{He}{}^{20}\text{Ne}$ with the proportion of ilmenite in these samples is apparent. The elemental and isotopic ratios of the surface correlated noble gases in Luna 16 resemble those previously found in Apollo fines. Based on ²¹Ne, ⁷⁸Kr and ¹²⁶Xe a cosmic ray exposure age of 360 my was determined. This age is similar to those obtained for the soils from other lunar maria.     

Oxygen and bulk element abundances in Luna 20 fines

Abundances of O, Si, Al and Mn have been determined in Luna 20 fines sample 22001,9 by instrumental neutron activation analysis. The abundances of O, Si and Al are among the highest we have observed in lunar samples and reflect a highlands origin for much of this regolith sample. The Luna 20 abundances reported here most closely resemble those we have determined in four samples of two Apollo 16 fines, rock 14310, and a clast from breccia 15459. The Luna 20 $\text{O}\text{Si}$ ratio of 1.96 ± 0.05 is similar to that in most other lunar samples, but the $\text{Al}\text{Si}$ ratio of 0.532 ± 0.024 is exceeded only by our data on the Apollo 16 fines. This $\text{Al}\text{Si}$ ratio is in agreement with the value of 0.55 ± 0.06 determined by the remote X-ray fluorescence experiment for the highlands between Mare Crisium and Mare Smythii which lie near the Luna 20 site (Adleret al., 1972).     

The halogens in Luna 16 and Luna 20 soils

Cl and P₂U₅ do not appear to exhibit the same correlation in soils from the Luna 20 and possibly the Luna 16 sites as they do in samples from the Apollo 11–15 sites. Nevertheless, the coherence between labile Cl and other KREEP-related elements is maintained.     

Oxide minerals in lithic fragments from Luna 20 fines

One hundred and seventy-six oxide mineral grains in the Luna 20 samples were analyzed by electron microprobe. Spinel is the most abundant oxide, occurring in troctolite fragments. Next most abundant is ilmenite, which occurs in all rock types except those containing spinel. Chromite also occurs in all rock types except those containing spinel. Minor amounts of ulvöspinel, armalcolite, zirkelite, baddeleyite and an unidentified TiO₂-rich phase were also found.Spinel grains are predominantly spinel-hercynite solid solutions, commonly with very minor chromite. The $\text{Fe}\text{(Fe + Mg)}$ ratio is generally lower than in spinel from Apollo 14 rocks. Chromites in non-mare rocks are similar to those from mare rocks. Ilmenite of mare origin is Mg-poor and Zr-rich compared to non-mare ilmenite; these elements may therefore be useful in determining the origin of ilmenite grains.Phase equilibria considerations suggest that spinel troctolite crystallized from a melt high in alumina; a likely candidate is the high-alumina basalt of Prinzet al. (1973a).Sub-micron wide rods of metallic Fe occur in plagioclase grains and may have formed by sub-solidus reduction processes.     

Carbon chemistry of Luna 16 and Luna 20 samples

Luna 16 and Luna 20 samples were analyzed for volatilizable species using vacuum pyrolysis to 1400°C. The major gaseous products evolved (ranging from 10–650 μg/g) were H₂O, CO, CO₂, N₂ and CH₄. Minor components (all < 10 μg/g) included NH₃, HCN, NO, SO₂, H₂S, C₂H₂, C₂H₄, C₂H₆, C₃H₆ and higher hydrocarbons, benzene, toluene, and the polymeric contaminants Teflon^® and silicone oil. The total carbon and nitrogen contents (μg/g) for these sieved samples (< 125 μm) were: Luna 16—C 418, N 134 and Luna 20—C 380, N 80.     

Helium and argon isotopes in spinel lherzolite from Damaping, northern Zhangjiakou

Spinel lherzolite found in Damaping, northern Zhangjiakou, Hebei Province occurs as xenoliths in the Hannuoba basalts that consist of alkali basalt and tholeiite. Spinel lherzolites contain 50%–70% olivine (Fo: 90%), 10%–20% clinopyroxene (predominantly Di), 10%–30% orthopyroxene (predominantly En), and less than 5% spinel.³He/⁴He and⁴⁰Ar/³⁸Ar ratios in the olivine are 7.56×10⁻⁷ and 299.1, respectively.³He/⁴He and⁴⁰Ar/³⁸Ar ratios in the orthopyroxene (enstatite) are 9.1×10⁻⁷ and 307, respectively. Olivine grains are fractured irregularly, and pyroxene grains characterized by well developed cleavages, which would have resulted from explosion during the rapid eruption of lava from the deep interior to the surface. The lower isotope ratios of helium and argon may indicate that the spinel lherzolite xenoliths were derived from the strongly degassed and depleted upper mantle, and that the mantle is inhomogeneous.³He losses to some extent might affect the helium isotope ratios. The project was financially supported by the National Natural Science Foundation of China (No. 49273185).     

Mineral phases on the fracture of a glass particle and in the fines of a Luna 24 regolith sample

This paper reports new findings of native molybdenum and iron from Mare Crisium. Native tin, copper, and nickel were detected for the first time in this area of the lunar surface. Native tantalum and indium, intermetallic compound Ta₂Mo, and barium titanate Ba₂TiO₄ were found for the first time on the Moon. The latter two phases were observed for the first time in nature. It was shown that the investigated mineral phases correspond to different genetic groups (preimpact, impact, and postimpact mineral assemblages), which is in general typical of lunar regolith. Based on the morphological features of the identified mineral phases, the history of the formation of impact glass particles was reconstructed in part. They were probably affected by at least three impact events. It was concluded that the peculiar molybdenum geochemical anomaly observed in a group of orange impact glass fragments was not related to the impactor material but rather to the intrinsic enrichment in molybdenum of lunar rocks (target) in the area of the impact events. It was supposed that this enrichment could be of exhalative (fumarole) nature.     

Helium and argon isotopes in rocks and minerals of the Lovozero Alkaline Massif

The contents and ratios of helium and argon isotopes were studied in rocks of the Lovozero Massif and related rare-metal (loparite) deposits. The gases were extracted by melting (from whole-rock and mineral samples) and crushing (mainly from fluid inclusions) methods. The wide variations in the He and Ar isotopic compositions can be explained by the fact that the trapped fluid represents a mixture of variable proportions of mantle, crustal, and atmogenic components and radiogenic in situ produced gas. The obtained gas-geochemical data reflect the complex evolution of the considered ore-magmatic system and the similar trends of melt evolution and complementary fluid phase in the magmatic chamber, in general, in three-rock (urtite-foyaite-lujavrite) units and, in each individual layers, the relative closeness of the system during magmatic crystallization and initial epimagmatic processes. It was also found that the earliest magmatic mineral was loparite and that ore units and mineralization could be partially transformed during a comparatively late postmagmatic stage. An important role of paleometeoric waters in the low-temperature mineral formation was shown.     

内蒙古哈达门沟金矿成矿流体来源的氦、氩同位素示踪

内蒙古包头市哈达门沟金矿床是华北陆块北缘乌拉山-大青山地区的大型金矿床,矿床赋存于新太古界乌拉山群黑云角闪斜长片麻岩、角闪黑云二长片麻岩和含石榴石黑云斜长片麻岩中,成矿流体性质不明。文章对哈达门沟金矿主要载金矿物黄铁矿开展了流体包裹体中的He、Ar同位素组成研究。研究表明,赋存于黄铁矿流体包裹体中的4He含量为(83.92~606.46)×10-8cm3STP/g,n(3He)/n(4He)值为0.19~0.91Ra,幔源He的含量为2.62%~13.73%,平均为9.95%,表明成矿流体中的He主要来源于地壳,大约10%来源于地幔。~(40)Ar含量为(71.22~308.22)×10~(-8)cm~3STP/g,~(40)Ar/~(36)Ar比值变化于2793.6~7253.5之间,在n(~(40)Ar)/n(~(36)Ar)与R/Ra图解和n(~(40)Ar*)/n(4He)与R/Ra图解中,显示地壳氩和地幔氩的混合来源特征。结合已有的氢、氧、硫同位素研究,认为哈达门沟金矿成矿流体主体为地壳来源,但幔源流体的加入清晰可辨,乌拉特前旗-呼和浩特山前断裂很可能为富钾质壳幔混合流体的运移提供了通道和动力。     

Helium and neon isotope geochemistry of some ground waters from the Canadian Precambrian Shield

Ground waters in a Precambrian granitic batholith at the Whiteshell Nuclear Research Establishment (WNRE) in Pinawa, Manitoba contain between 5 × 10^?5 and 10^?1 cc STP/g_H2O of radiogenic helium-4 but have relatively uniform ³He/⁴He ratios of between 0.6 × 10^?8 and 2.3 × 10³. The highest helium samples also contain radiogenic ^21,22Ne produced by (α,n) or (n,α) reactions with other isotopes. As much as 1.8 × 10^?9ccSTP/g_H2O of excess ²¹Ne and 3.8 × 10^?9ccSTP/gH₂O of excess ²²Ne have been measured. Helium and ²¹Ne ages of these ground waters, calculated on the basis of known crustal production rates of ⁴He and ²¹Ne, are unreasonably high (up to 2 × 10⁵ years) and incompatible with the ¹⁴C ages and other isotopic and hydrogeologic data. Uranium enrichment in the flow porosity of the granite may dominate ⁴He and ^21,22Ne production in this granite and mask the contributions from more typical U and Th concentrations in the rock matrix.At the Chalk River Nuclear Laboratories in Ontario helium concentrations in ground waters in a Precambrian monzonitic gneiss range from 1.5 × 10^?7 to 8.7 × 10^?4ccSTP/g_H2O with the ³He/⁴He ratios ranging from 2.0 × 10^?3 to 1.5 × 10^?7. The highest helium concentrations may be attributable to the presence of a thick uraniferous pegmatite vein and yield helium ages more than two orders of magnitude higher than the ¹⁴C ages. Application of He age dating equations to ground waters from Precambrian granitic rocks requires knowledge of the nature of uranium and thorium enrichment in the subsurface in order to select appropriate values for porosity and uranium and thorium concentration in the rock.     

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.     

Crystal-melt partitioning of noble gases (helium, neon, argon, krypton, and xenon) for olivine and clinopyroxene

Mineral-melt partition coefficients of all noble gases (^min/meltD_i) have been obtained for olivine (ol) and clinopyroxene (cpx) by UV laser ablation (213 nm) of individual crystals grown from melts at 0.1 GPa mixed noble gas pressure. Experimental techniques were developed to grow crystals virtually free of melt and fluid inclusions since both have been found to cause profound problems in previous work. This is a particularly important issue for the analysis of noble gases in crystals that have very low partition coefficients relative to coexisting melt and fluid phases. The preferred partitioning values obtained for the ol-melt system for He, Ne, Ar, Kr, and Xe are 0.00017(13), 0.00007(7), 0.0011(6), 0.00026(16), and , respectively. The respective cpx-melt partition coefficients are 0.0002(2), 0.00041(35), 0.0011(7), 0.0002(2), and . The data confirm the incompatible behaviour of noble gases for both olivine and clinopyroxene but unlike other trace elements these values show little variation for a wide range of atomic radius. The lack of dependence of partitioning on atomic radius is, however, consistent with the partitioning behaviour of other trace elements which have been found to exhibit progressively lower dependence of ^min/meltD_i on radius as the charge decreases. As all noble gases appear to exhibit similar ^min/meltD_i values we deduce that noble gases are not significantly fractionated from each other by olivine and clinopyroxene during melting and fractional crystallisation. Although incompatible, the partitioning values for noble gases also suggest that significant amounts of primordial noble gases may well have been retained in the mantle despite intensive melting processes. The implication of our data is that high primordial/radiogenic noble gas ratios (³He/⁴He, ²²Ne/²¹Ne, and ³⁶Ar/⁴⁰Ar) characteristic of plume basalt sources can be achieved by recycling a previously melted (depleted) mantle source rather than reflecting an isolated, non-degassed primordial mantle region.     

Helium and argon isotopes in lower crustal xenoliths from the belomorian mobile belt

The isotopic systematics of noble gases (He and Ar) were studied in Neoarchean and Paleoproterozoic lower crustal xenoliths from the Belomorian mobile belt. The xenolith suite is dominated by garnet granulites (Grt + Cpx + Pl ± Opx ± Qtz ± Kfs ± Phl ± Hbl) and two-pyroxene or garnet pyroxenites (Cpx + Pl ± Grt ± Opx ± Hbl ± Qtz). The xenoliths and the host Devonian ultramafic lamprophyres forming diatremes and explosion dikes contain fluid with similar He and Ar isotopic compositions. It was found that the fluid was trapped by the rocks and xenolith minerals approximately simultaneously with the formation of the lamprophyres. This conclusion is based on the identical K-Ar ages of the majority of xenoliths and ultramafic lamprophyres. When the xenoliths were transported toward the surface by high-temperature ultrabasic melts, the noble gases occurring in them were partly (Ar) or completely (He) lost. The melts were contaminated by meteoric waters during their emplacement in the upper crust, which resulted in that the Ar isotopic composition of lamprophyres approached the composition of atmospheric Ar. The fluid phase that was liberated during melt crystallization severely affected the xenoliths, diminishing the difference between the isotope compositions of He and Ar in the xenoliths and ultramafic lamprophyres. The He isotope composition includes an admixture of mantle ³He, which is suggested by the high measured ³He concentrations, exceeding the calculated values, and high ³He/³⁶Ar ratios in the xenoliths and their host lamprophyres. The fraction of the mantle component in the fluid trapped by the xenoliths was estimated as ～20%.     

东天山黄土坡铜锌矿床成矿流体的氦-氩同位素示踪

黄土坡铜锌矿床是东天山卡拉塔格地区一中型海相火山岩型块状硫化物（VHMS）矿床,赋存于早志留世海相火山-沉积岩系中。矿体产于酸性火山角砾岩与凝灰岩之间,主矿体呈厚大的扁豆状,矿石主要呈块状、浸染状、条带状和网脉状构造。本文报道了黄土坡铜锌矿床成矿流体的氦和氩同位素组成,黄铁矿流体包裹体的³He 含量低,介于0.039×10^-12 cm³ STP/g～0.64×10^-12 cm³ STP/g,n（³He）/n（⁴He）值为 0.11～0.94 Ra,介于壳源He与幔源He之间。⁴⁰Ar 含量变化于 3.49×10^-8cm³ STP/g～34.25×10^-8 cm³ STP/g 之间,n（⁴⁰Ar）/n（³⁶Ar）介于301.40～425.98 之间。成矿流体中有幔源 He（1.71%～10.97%）和放射性成因 Ar（⁴⁰Ar*含量为1.96%～30.63%）。结合矿床包裹体及 H-O-S 同位素特征,认为幔源流体和富放射性成因He 和Ar 的海水参与了成矿。     

Valence state of iron in a condensate from the Luna 16 regolith

This paper reports the results of an X-ray photoelectron spectroscopic study of the condensate phase of regolith sample L1639 returned by the Luna 16 mission. The reduced Si⁰, Si²⁺, Al⁰, Ti²⁺, and Ti³⁺ forms were detected in the sample. Iron occurs in all valence states, and Fe³⁺ species were detected for the first time in the condensate. Minor Fe³⁺ concentrations were observed in the upper layers of the sample containing the maximum amounts of condensate products. The fraction of ferric Fe is 22%, and the Fe⁰: Fe²⁺: Fe³⁺ proportion is 33: 45: 22. The appearance of ferric Fe in the lunar condensate is explained by the reaction of FeO disproportionation occurring either at the stage of the expansion and cooling of impact-related vapor or directly in the condensed phase on the surface of regolith particles. This interpretation is supported by the results of a model experiment on augite vaporization and condensation. The experiment simulating impact vaporization was carried out on a laser set-up at a temperature of ∼3000–4000 K and a pulse duration of ∼10⁻³ s in a He atmosphere (P = 1 atm). The results of analyses provided compelling evidence that the condensate produced after augite vaporization contains Fe in all oxidation states, and the proportions of different valence forms approach the stoichiometry of the disproportionation reaction.     

On the origins of trapped helium,neon and argon isotopic variations in meteorites—II. Carbonaceous meteorites

Data are presented from stepwise heating experiments on five carbonaceous chondrites: Alais, Ivuna, Orgueil, Cold Bokkeveld and Nogoya. The data indicate the presence of two isotopically distinct major trapped components, components A and B. Two additional components, ‘C’ and ‘E,’ were isolated on the basis of neon isotopic structure. Components B and C, found in. gas-rich meteorites, are attributed to ion implantation by the present day solar wind and solar flares respectively. Component A is interpreted as a mixture of component E and component D (Paper I), where component D is identified with the primitive solar wind and component E is assigned an extra solar system origin.     

Helium and Argon Isotopic Composition of Cenozoic Alkali Basalts and Mantle-Derived Xenoliths from Kuandian, Liaoning Province, China

The noble gas isotopic composition and content data of 2 alkali basalts, 3 Iherzolite xenoliths and one clinopyroxene megacryst from the Kuandian region have confirmed the occurrence of a fractionation of noble gases during magmatism. Light noble gases such as He and Ne are high in mobility and appear to be incompatible as compared with heavy ones ( such as Kr and Xe). Therefore, light noble gases are abundant in volcanics, especially in the volcanics with bubbles; lherzolite xenoliths have relatively high heavy noble gases. The clinopyroxene megacryst has the lowest abundance of noble gases, probably due to its high P-T origin. Noble gas isotopic composition of the clinopyroxene megacryst reveals that the mantle source beneath the Kuandian area has an MORB-like reservoir with^3 He/^4He ratio of—10 Ra(Ra: atmospheric^3 He/^4He ratio) and^40 Ar/^36 Ar ratio of 345.6. The Iherzolite xenoliths possess moderate^3 He/^4He ratios of 2.59 -4.53 Ra, reflecting the loss of primary helium during rock deformation or metasomatism caused by enriched mantle fluids during the up-lifting. The alkali volcanics have very low^3 He/^4 He ratios(0.47—0.61 Ra),indicating a contribution of radiogenic^4 He, probably having resulted from crust contamination. Most of the samples have excess^21 Ne and^22 Ne as compared with atmospheric neon, but Kr and Xe isotopic compositions are indistinguishable from atmospheric values within uncertainties with only individual samples having excess^129Xe,^134Xeand^136 Xe.     

18O16O ratios in Luna 16 fines

Partial fluorination experiments developed on a 26 mg sample of Luna 16 fines show a big ¹⁸O enrichment in the first oxygen evolved similar to those observed by Epstein and Taylor on Apollo samples and probably related to the high solar wind content of this sample.