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1.
The Luna 20 soil (< 125 μm fraction) has a relatively low δO18 (5.7%.), compared to other lunar soils (5.8 to 6.3%.). This implies either a low-O18 source material or an unusually small O18 enrichment in the processes of soil formation and maturation.  相似文献   

2.
The Upper Cretaceous (Campanian–Maastrichtian) Taveiro and Aveiro Formations belong to the northern sector of the Lusitanian basin (Portuguese western margin). The Taveiro Formation was deposited in alluvial fans, including mud flow beds, lakes and sinuous rivers. The Aveiro Formation was deposited in a flat region with low hydrodynamics channels, with the formation of a barrier island-tidal system. The reconstruction of this sedimentary basin may be difficult due to its complex architecture. This work aims a methodology to be used in the reconstruction of Cretaceous sedimentary environments of the Lusitanian basin, through the establishment of geochemical patterns of different size fractions of those deposits. Chemical analysis was performed by instrumental neutron activation analysis (INAA), and the mineralogical composition obtained by X-ray diffractometry (XRD). The whole rock and different size fractions (? ≥ 125 μm, 63–125 μm, 20–63 μm, 2–20 μm and ? < 2 μm) of selected samples were studied aiming the rare earth elements (REE) and other trace elements distribution and its correlation with the grain size and mineralogy.The results obtained for the studied Cretaceous sediments showed that REE patterns and other trace elements distribution in the different size fractions may be used as a tool to differentiate deposits within and between sedimentary formations. Within the Taveiro Formation, REE are concentrated in the silt fractions (20–63 μm and 2–20 μm) of the Reveles deposit, and in the clay size fraction of S. Pedro deposit, which is richer in kaolinite. The 1st transition elements, particularly Zn, are correlated with the presence of smectite in the clay fraction of Reveles deposit. In the sand and silt size fractions (>2 μm) of samples from Taveiro Formation correlations were found between: Ga and 1st transition elements, and phyllosilicates; Cs and mica; and Rb and Ba, and K–feldspars.The Bustos deposit (Aveiro Formation) samples are very fine-grained and with a high proportion of the fine silt fraction where REE are concentrated, especially the heavy ones. Incorporation of MREE, Co and U in carbonates of the coarser fraction appears to occur. The abundances of the 1st transition elements, Ga and As, are correlated with phyllosilicates.Significant differences were found in the trace elements patterns of the various analysed size fractions of the Lusitanian basin of Cretaceous sediments, between and even within formations, which can be used as a methodological approach for a fine paleogeographic reconstruction.  相似文献   

3.
Visible and near-infra-red spectra of chemically analyzed grains of glass and minerals from the Luna 20 sample were compared with diffuse reflectance spectra of the bulk soil. As in the spectra of soil samples from other localities on the Moon, pyroxene contributes two broad absorption features near 1 μm and 2 μm. The soil has a high integral reflectance (or albedo) arising from plagioclase, which appears to be the dominant mineral in the lunar highlands. The Luna 20 soil curve is most similar to the reflectance curves of the non-rayed soils at Apollo 16, in agreement with the generally similar mineralogy of these samples. The average pyroxene composition in the Luna 20 soil, as determined from the absorption bands in the diffuse reflectance spectra, and analyses of single crystals, is more calcic than in the lithic fragments. Thus, the soil appears to have a few per cent of admixed material derived from mare basalts. Comparison of the soil spectrum with telescopic curves of nearby areas reveals a close similarity; however, the Luna 20 sample is slightly less mature than expected. Luna 20 may have sampled subsurface material that is fresher than the regional surface soil, or alternatively, the Luna 20 area may contain an admixture of relatively recently exposed material from a ray crater.  相似文献   

4.
An orientation survey was undertaken in northwest Ngamiland to evaluate, among other criteria, an optimum size fraction for trace element analysis in the Kalahari sandveld regolith samples for a regional geochemical mapping project in the area. The most prominent geomorphological features of the region are the longitudinal rolling sand dunes and floodplain sediments adjacent to the unique, mid-continent Okavango Delta. Most of the dune sands were deposited in the Late Quaternary, and they show evidence of both pluvial and and environments. Presently the a lab dunes support varied shrub/grass vegetation with intermittent tree cover. Extensive forest fires have affected the region for generations, and the occurrences of remnants of large trees indicate that the region may have also supported large forests at some stage.The sandveld regolith comprises 70% quartz sand (−1000 + 63 μm) and 10–20% silt/clay (< 63 μm) material. There are no size variations between material from dune crests, dune depressions and down the soil profile to a depth of a metre. The process of regolith formation is relatively young and dynamic, being widely churned by a variety of boring animals, termites, ants and other insects. Hence no distinct zonation of soil horizons in the top 100 cm of the soil catena were observed. Remarkably, the significant proportion of the silt/clay fraction in the regolith indicates progressive weathering and possible deposition of precipitates.Trace element contents are invariably enhanced in the fine fractions, a characteristic widely observed elsewhere in residual soils. On the Xaxa-Cheracheraha traverse Zn values range from 2 to 98 ppm (mean 9 ppm); Pb varies from 1 to 101 ppm (mean 27 ppm) and Cu from 0 to 18 ppm (mean 5 ppm) in the −75 μm fraction. Contents in the −180 + 75 μm are, however, significantly lower than in the fine fractions. The variations in element concentrations along each of the orientation survey traverses at Qangwa-Nokaneng, Nxaunxau-Qurube and Nxaunxau-Ghane, in the coarse and fine fractions, generally remain sympathetic, showing that the enhanced values in the fines are a result of secondary dispersion, rather than mere compositional differences in the sandveld regolith.  相似文献   

5.
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.  相似文献   

6.
Four volatile, six siderophile and 18 generally lithophile elements were determined in six sieve fractions of mare soil 15100 and seven sieve fractions of highlands soil 66080; 15100 is a moderately and 66080 a highly mature soil.Two size fractions of 66080 were subjected to leaching with HCI and etching with HF. Leaching removed ca. 25% of the rare earths in both the 500-177 μm and 62-20 μm fractions; the soluble phase, probably a phosphate, is enriched in light rare earths relative to the bulk soil. The leach and etch removed a larger portion of Zn and Cd than expected on the basis of surface concentrations inferred from size distribution data apparently because of selective dissolution of minor volatile-rich phases.Lithophile concentrations in 66080 are nearly independent of grain size. In 15100 decreasing grain sizes show moderately increasing amounts of KREEP and anorthosite related elements, and decreasing amounts of basalt related elements. In 66080 a maximum in siderophile concentration occurs at ca 150 μm, as previously observed in our studies of 61220, 63500 and 65500. This peaking appears to result from a gradual increase with time in the size of metal grains as a result of welding during micrometeorite impacts. The coarse fraction maximum is not observed in the siderophile data for 15100, probably because of the much smaller fluence of extralunar projectiles at the Apollo 15 site. A modest rise in siderophile concentrations in the smallest size fractions of all soils probably results from recondensation of impact-vaporized materials.The concentrations of highly volatile Zn, Cd and In in 15100 and 66080 show a marked increase with decreasing size, but the fine/coarse ratios are about a factor of two lower than those in soils 61220 and 63500. The lower ratio in 66080 results entirely from higher concentrations in the coarser fractions. It appears that this is a reflection of the higher maturity of 66080, and that the volume-correlated component in lunar soils increases with increasing near-surface residency. The high amount of volume-correlated component in 15100 may be related to the more efficient formation of agglutinates in basalt-rich soils. The observed increase in rare gas and volatile metal concentration with decreasing grain size results from an increasing bias in surface exposure of fine grain sizes, probably as a result of the adhesion of smaller to larger grains.  相似文献   

7.
The Nickel Plate deposit, in which gold occurs as <25 μm blebs associated with arsenopyrite in garnet-pyroxene skarns, is in the subalpine zone near the southern limit of the Thompson Plateau. During the last glaciation the Cordilleran ice sheet moved south-southwest across the deposit and deposited a stony basal till. A dispersion train with anomalous concentrations of gold in tills and soils now extends 2 km down ice from the deposit.Gold contents of samples of humus (LFH horizon) and the −212 μm fraction of mineral soils (A, B and C horizons) was determined by instrumental neutron activation and fire assay-atomic absorption, respectively. Selected samples were examined in detail to determine distribution of gold between different size and density fractions.Despite erratic variability, Au contents of the −212 μm fraction generally decrease from 200–400 ppb close to the mine site to <50 ppb at distal sites. At most sites there is also a twofold increase of gold values down the soil profile. Within samples concentrations of Au in the −420 + 212 μm, −212 + 106 μm, −106 + 53 μm and −53 μm fractions are usually roughly constant. However, because of its abundance, the −53 μm fraction contains more than 70% of the gold. Amenability of gold in this fraction to cyanidation suggests that it is largely free gold. For size fractions > 53 μm the contribution of the heavy mineral (SG > 3.3) fraction to total gold content increases with decreasing grain size.Distribution of gold between size and density fractions is consistent with its release from the bedrock or pre-glacial regolith by glacial abrasion. The bulk of the gold was incorporated into the fine fractions of the till at or close to the source. However, differences between down ice dilution ratios for gold in different heavy mineral size fractions suggest that comminution of host minerals continued to transfer gold to the finer size fractions during glacial transport.For exploration purposes, B and C horizon samples provide the best anomaly contrast. Estimates of the abundance of gold particles in different size fractions indicate that the nugget effect, which causes erratic gold values in the −212 μm fraction, can be avoided by analysis of 30 g of −53 μm material.  相似文献   

8.
Major element analyses of nineteen Luna 20 glass particles indicate that most of the Luna 20 glasses have Al2O3 contents greater than 21 wt.% and compositions similar to Apollo 10 and Luna 20 rocks and soils. Three of the glass particles have low Al2O3 (< 13 wt.%) and high FeO (> 18 wt.%) contents and were probably derived from one of the adjacent maria. The low glass content of the Luna 20 soil indicates that it is relatively young or less mature than most mare soils that have been studied.  相似文献   

9.
The manned Apollo 11, 12, 14 and 15 and the automated Luna 16 lunar missions have provided us with lunar rock and regolith (soil) samples from a number of geologically distinct sites. The mare regions were sampled by Apollo 11, 12 and Luna 16, whereas Apollo 14 landed on a terrain with more relief, the Fra Mauro Formation which represents an ejecta blanket from the Imbrian Basin, and Apollo 15 touched down near the lunar highlands. The samples collected consist of a mixture, mainly of basalt, breccia and regolith (soil-particulate matter, generally < 1 cm in size). The basalts show considerable variation in texture, mineralogy and chemistry and probably represent fragments from various parts of relatively thin and extensive lava flows in the maria. The breccias represent regolith material which was indurated to varying degrees by impact events. The regolith is a product of the breakdown, again by impact, of coherent rock masses of basalt and breccia.  相似文献   

10.
Two milligrams of less than 125 μm size particles from the Luna 20 soil sample (22001,17) have been examined. The results of the mineral identification and analysis verify earlier assumptions that the nature of the lunar highlands is predominantly anorthositic in composition. The presence of highly magnesian clinopyroxene, orthopyroxene and olivine suggests crystallization of Highland rocks in an ultrabasic environment. No fragments were observed that could be unequivocally assigned to mare basalt types.  相似文献   

11.
Samples were collected near known gold mineralization from anomalous and background soils developed on glacial till in British Columbia and Ontario, and in residual soils in Nevada, Utah and the Yukon Territory. After wet sieving to five size fractions finer than 2000 mm, and separation of heavy minerals (S.G. > 3.3) for the − 212 + 106 μm and − 106 + 53 μm fractions, gold concentrations in each fraction were determined by fire assay-atomic absorption.In all cases more than 60% of the gold resides in the − 53 μm fraction. For the residual soils most of the remaining gold is associated with the light mineral fractions and only a negligible proportion resides in the heavy minerals. Estimates of the numbers of gold particles and subsampling variability suggest that gold, in both heavy and light mineral fractions, is largely present as inclusions of fine gold. For exploration purposes, optimum sample representativity would be obtained with the − 53 μm fraction. However, because this fraction is a major component of the soils, use of a coarser size fraction (e.g., − 212 μm) will only slightly reduce sample representativity. Also, because most of the gold is associated with the − 53 μm and light mineral fractions, use of heavy mineral concentrates offers no significant advantage and in some cases would result in anomalous conditions being overlooked.  相似文献   

12.
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 4He20Ne varies in the soils from different lunar maria due to diffusion losses. A rough correlation of 4He20Ne 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.  相似文献   

13.
A new mineral phase was discovered in the course of studies at the Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry (IGEM) of fine-grained fractions of the lunar regolith delivered to the Earth by the Luna 16, Luna 20, and Luna 24 automatic stations. The grain of native niobium was identified in the regolith sample from the Mare Crisium. Presumably, this phase was formed during the fractioning process in a gas–plasma cloud under an impact event on the Moon.  相似文献   

14.
Urban roadside soils are the “recipients” of large amounts of heavy metals from a variety of sources including vehicle emissions, coal burning waste and other activities. The behavior of heavy metals in urban roadside soils depends on the occurrence as well as the total amount. Accordingly, knowledge of the interactions between heavy metals and other constituents in the soil is required to judge their environmental impact. In this study, correlations of heavy metal concentrations (Pb, Zn, Cu, Ag, Se, Ni, Cr and Ba) to iron extracted using dithionite–citrate–bicarbonate (DCB) buffer (FeDCB), fulvic acids and particle size fractions were examined from the Xuzhou urban roadside soils. Heavy metals except for Cr and fulvic acids had a positive significant correlation with FeDCB, indicating these metals and fulvic acids are principally associated with the surfaces of iron oxides of the soils. Significant positive correlations were also found between the contents of fulvic acids and heavy metals, showing these heavy metals (especially for Cu, Ni and Cr) form stable complexes with fulvic acids. Such finding is of importance with regard to the increased mobilization of heavy metals, e.g., into freshwater ecosystems. Ag, Se and Cr are independent of particle size fractions because of their low concentrations of Ag and Se in the studied soils. Pb, Zn, Cu, Ba and Ag are mainly enriched in the finer soil particles (especially <16 μm).  相似文献   

15.
Bioturbation is generally not a strongly size-dependent or shape-dependent process in deep-sea sediments. Different sizes of ash (11–250 μm) deposited during a single eruption are usually mixed about equally, although in a few cores we found minor tendencies toward greater mixing of finer ash. Platey volcanic ash and spherical microtektites initially deposited within a few centimeters of each other in the sediment column are mixed with roughly comparable intensity. Radiocarbon dating of three sizes of CaCO3 near the top of one box core produced ages within the analytical error; this also suggests no size dependency in the mixing process. Another core showed age differences opposite in sense to those that would be predicted if the finer fractions were more intensely mixed than the coarser fractions.The sizes examined (11–250 μm) encompass most of the sedimentary components used in paleoclimatic analyses of deep-sea cores. From these findings, we infer that significant artificial lead/lag offsets in paleoclimatic signals will not be created by size-selective or shape-selective mixing. Mixing models calibrated on one sediment size fraction should be generally applicable to other sizes and kinds of material.  相似文献   

16.
Membrane filtration technique was applied to study the distribution of iodine and some other chemical elements (iron, manganese, aluminum, and silicon) in natural waters between different sized fractions (>0.45, 0.45–0.22, 0.22–0.1, and <0.1 μm). The paper presents analysis of factors able to modify the proportions of the adsorbed and dissolved species of the elements in waters. It is proved that up to 90% of the total amount of the iodine ion occurs in aquatic environments in the form of dissolved species (according to the current standard, in the fraction < 0.45 μm), with approximately 49% of the total concentration corresponding to the fraction of <0.10 μm. An increase in the acidity of the waters and their enrichment in finely divided organic and mineral material, and also an increase in Fe and Mn concentrations, may increase in the concentrations of the trace element in the particulate matter (up to 26% of the total iodide concentration). The greatest variations in iodine distribution between different fractions are found in the surface waters.  相似文献   

17.
Heavy metal distribution in sediments of Krishna River basin,India   总被引：1，自引：0，他引：1  
Suspended and bed sediments collected from the entire region of the Krishna River and its major tributaries were analyzed for heavy metals (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb) by the thin-film energy dispersive x-ray fluorescence technique. There is considerable variation in the concentration of elements towards downstream, which may be due to the variation in the subbasin geology and various degrees of human impact. Suspended particles are enriched in heavy metals throughout the basin relative to bed sediments. The heavy metals are enriched in coarse size fractions (10–90 µm) throughout the Krishna River except its tributary Bhima, where finer fractions (2 µm) dominate. Transition elements correlate very well with each other. There is a striking similarity between the bed sediments of Krishna River and the Indian average. When the annual heavy metal flux carried by the Krishna River was estimated, and viewed in relation to the other major riverine transport, the Krishna is seen to be a minor contributor of heavy metals to the Bay of Bengal.  相似文献   

18.
Dissolved (<1 kDa), colloidal (1 kDa–0.45 μm) and particulate (>0.45 μm) size fractions of 30 elements were determined for four rivers (Sirppujoki, Laajoki, Mynäjoki and Paimionjoki), including 12 low-order inflow streams, largely affected by soil erosion and acidity in SW Finland. In addition, geochemical modelling was used to predict the formation of free ions and complexes in these rivers. Total metal concentrations were relatively high but most of the elements occurred mainly in a colloidal or particulate form and even elements expected to be very soluble occurred to a large extent in colloidal form. According to geochemical modelling these patterns could be explained by in-stream metal complexation/adsorption only to a limited extent. Instead there were strong indications that the high metal concentrations and dominant solid fractions were largely caused by erosion of metal bearing phyllosilicates. A strong influence of acid sulphate (AS) soils, known to exist in the catchment, could be clearly distinguished in Sirppujoki river as it had very high concentrations of dissolved metals, while in the two nearby rivers (Laajoki and Mynäjoki) the influence of AS soils was largely masked by eroded phyllosilicates. In Paimionjoki river the colloidal and particulate fractions dominated very strongly, indicating that total metal concentrations are almost solely controlled by erosion of phyllosilicates. Consequently, rivers draining clay plains sensitive to erosion, like those in SW Finland, have generally high “background” metal concentrations due to erosion of relatively non-toxic colloidal/particulate phyllosilicates. Thus, relying on only semi-dissolved (<0.45 μm) concentrations obtained in routine monitoring and/or speciation modelling can lead to a great overestimation of the water toxicity in this environment.  相似文献   

19.
The chemical status of ∼40 major and trace elements (TE) and organic carbon (OC) in pristine boreal rivers draining the basaltic plateau of Central Siberia (Putorana) and interstitial solutions of permafrost soils was investigated. Water samples were filtered in the field through progressively decreasing pore size (5 μm → 0.22 μm → 0.025 μm → 10 kDa → 1 kDa) using cascade frontal filtration technique. Most rivers and soil porewaters exhibit 2-5 times higher than the world average concentration of dissolved (i.e., <0.22 μm) iron (0.03-0.4 mg/L), aluminum (0.03-0.4 mg/L), OC (10-20 mg/L) and various trace elements that are usually considered as immobile in weathering processes (Ti, Zr, Ga, Y, REEs). Ultrafiltration revealed strong relationships between concentration of TE and that of colloidal Fe and Al. According to their partition during filtration and association with colloids, two groups of elements can be distinguished: (i) those weakly dependent on ultrafiltration and that are likely to be present as truly dissolved inorganic species (Li, Na, K, Si, Mn, Mo, Rb, Cs, As, Sb) or, partially (20-30%) associated with small size Fe- and Al-colloids (Ca, Mg, Sr, Ba) and to small (<1-10 kDa) organic complexes (Co, Ni, Cu, Zn), and (ii) elements strongly associated with colloidal iron and aluminum in all ultrafiltrates largely present in 1-100 kDa fraction (Ga, Y, REEs, Pb, V, Cr, Ti, Ge, Zr, Th, U). TE concentrations and partition coefficients did not show any detectable variations between different colloidal fractions for soil porewaters, suprapermafrost flow and surface streams. TE concentration measurements in river suspended particles demonstrated significant contribution (i.e., ?30%) of conventionally dissolved (<0.22 μm) forms for usually “immobile” elements such as divalent transition metals, Cd, Pb, V, Sn, Y, REEs, Zr, Hf, Th. The Al-normalized accumulation coefficients of TE in vegetation litter compared to basalts achieve 10-100 for B, Mn, Zn, As, Sr, Sn, Sb, and the larch litter degradation is able to provide the major contribution to the annual dissolved flux of most trace elements. It is hypothesized that the decomposition of plant litter in the topsoil horizon leads to Fe(III)-, Al-organic colloids formation and serves as an important source of elements in downward percolating fluids.  相似文献   

20.
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 SmEu 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.  相似文献   

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