Low Concentrations Of Trace Elements Research Articles

Trace Element (Se, As, Mo, B) Contamination of Evaporites in Hypersaline Agricultural Evaporation Ponds

Disposal of saline drainage waters containing elevated concentrations of the trace elements Se, As, B, and Mo poses a severe environmental hazard in the western part of the San Joaquin Valley of California. This study investigated the partitioning of these trace elements into evaporite minerals formed in agricultural evaporation ponds to determine trace element behavior during the evaporite formation stage and to provide information for development of management strategies to minimize environmental hazards. The trace elements were largely excluded from the evaporite minerals (∼100 times depleted relative to the solution phase), resulting in comparatively low trace element concentrations in these minerals. The affinity of trace element partitioning to the solid phase follows: Se B > As Mo. No differences in trace element partitioning were evident between summer and winter seasons, the type of evaporite formed, or whether the evaporites were collected wet or dry. Since trace elements accumulate in the solution phase, highly evapoconcentrated waters may exceed threshold levels for hazardous waste classification. Isolating these trace element-rich solutions during the latter stages of evapoconcentration into specialized treatment and handling facilities may provide an effective management strategy that minimizes both exposure to waterfowl and the amount of hazardous solid waste generated.

Is the Lower Duarte Igneous Complex (Hispaniola) a Remnant of the Caribbean Plume-Generated Oceanic Plateau?

Eleven samples of metapicrites, metaankaramites, diabases, and cumulates of the lower Duarte Complex in central Hispaniola were analyzed for major, trace element, and Nd-Sr isotopic compositions. The picrites are plagioclase-free and rich in phenocrysts of clinopyroxene and olivine pseudomorphs. The ankaramites differ from the picrites by the presence of abundant and large clinopyroxene phenocrysts. The diabases consist of plagioclase laths embedded with clinopyroxene. These rocks show E-MORB affinities. Relative to N-MORB, they exhibit high concentrations in Nb, Ta, Th, Ti, light and medium rare earth elements, and low Y contents. They are associated with olivine-clinopyroxene cumulates and gabbros. The olivine-clinopyroxene cumulates differ from the lavas by lower trace element contents and a lesser LREE enrichment. The gabbros exhibit flat REE patterns. All these clinopyroxene-rich rocks show homogeneous ratios ( + 5.3 to +7.1), which plot within the range of Ocean Island basalts. Their ratios are less homogeneous () but fall within the Mantle Array, with the exception of the gabbro and a picrite, which show the highest ratios (0.70374, 0.70406). The picrites are geochemically similar to the Enriched Basalts from Gorgona and southern Haiti. These data lead us to develop the hypothesis that the lower Duarte complex likely represents the remnants of an oceanic plateau generated by a Galapagos-type hotspot that collided with the proto-Caribbean arc during the Late Cretaceous.

Is the Lower Duarte Igneous Complex (Hispaniola) a Remnant of the Caribbean Plume-Generated Oceanic Plateau?

Eleven samples of metapicrites, metaankaramites, diabases, and cumulates of the lower Duarte Complex in central Hispaniola were analyzed for major, trace element, and Nd-Sr isotopic compositions. The picrites are plagioclase-free and rich in phenocrysts of clinopyroxene and olivine pseudomorphs. The ankaramites differ from the picrites by the presence of abundant and large clinopyroxene phenocrysts. The diabases consist of plagioclase laths embedded with clinopyroxene. These rocks show E-MORB affinities. Relative to N-MORB, they exhibit high concentrations in Nb, Ta, Th, Ti, light and medium rare earth elements, and low Y contents. They are associated with olivine-clinopyroxene cumulates and gabbros. The olivine-clinopyroxene cumulates differ from the lavas by lower trace element contents and a lesser LREE enrichment. The gabbros exhibit flat REE patterns. All these clinopyroxene-rich rocks show homogeneous $$\epsilon_{Nd(T = 150 Ma)}$$ ratios ( + 5.3 to +7.1), which plot within the range of Ocean Island basalts. Their $$\epsilon_{Sr(T = 150 Ma)}$$ ratios are less homogeneous ($$-16.7 < \epsilon_{Sr} < -3.7; 0.70315 < (^{87}Sr/^{86}Sr)_{i} < 0.70406$$) but fall within the Mantle Array, with the exception of the gabbro and a picrite, which show the highest $$(^{87}Sr/^{86}Sr)_{i}$$ ratios (0.70374, 0.70406). The picrites are geochemically similar to the Enriched Basalts from Gorgona and southern Haiti. These data lead us to develop the hypothesis that the lower Duarte complex likely represents the remnants of an oceanic plateau generated by a Galapagos-type hotspot that collided with the proto-Caribbean arc during the Late Cretaceous.

Manganese ores of the Ghoriajhor-Monmunda area, Sundergarh District, Orissa, India: geochemical evidence for a mixed Mn source

Abstract The Proterozoic sedimentary manganese ores of the Gangpur Series, Orissa, India are of gonditic type and are variable in size, depth and grade of ore. The host sediments were deposited in a shallow shelf environment, as reflected in the variable clastic input into the sequence. Braunite and hollandite are the principal ore minerals, with bixbyite, rare jacobsite and rare vredenburgite. Manganese minerals in the gondites are spessartine and rhodite, together with quartz and aluminosilicates. Supergene weathering and enrichment of the ore horizon and gondite produced secondary ores composed of cryptomelane and pyrolusite. The geochemistry of the deposits shows Mn/Fe≈4, low trace element concentrations and arsenic enrichments that exceed 3000 mg kg −1 . These are interpreted as indicating a mixed hydrogenetic-hydrothermal source for the manganese oxides of the original precurser (pre-metamorphism) sediments. Regional metamorphism to amphibolite grade transformed this variable oxide-clastic sequence into manganese ores, sharply interbedded with gondites.

Optimization of PIXE analysis for Cu and other trace elements in cerebrospinal fluid to improve the detection limits

An external beam PIXE system was optimized for the determination of the extremely low trace element content of normal cerebrospinal fluid. In order to improve the detection limits of the elements of interest, the ultrafiltrated cerebrospinal fluid samples were deposited onto ultrathin Formvar foils and measured in a helium atmosphere. Since the main emphasis was on copper, the absorber used in the measurements was optimized to give a favourable peak/background ratio for this element. The resulting detection limits for Fe, Cu, Zn and Br were (6.3 ± 2.9), (4.1 ± 1.4), (8.5 ± 2.6) and (18.1 ± 1.1) ppb, respectively. This allowed sufficiently precise determination of the low elemental concentrations in 50 μl of human cerebrospinal fluid.

Relationship between moderate food restriction during pregnancy and Fe, Zn and Cu contents in maternal tissues and foetuses.

This study was undertaken to monitor Fe, Zn and Cu contents in several maternal tissues and the products of conception of rats submitted to moderate food restriction during pregnancy. Two groups of female rats, nonpregnant (NP) and pregnant (P1), were fed ad libitum. A second group of pregnant rats (restricted diet, P2) was fed for 14 days with the same intake as NP, then the intake was increased by 5% from day 14 to day 21. A significant decrease in liver Fe content was noted in P1 and P2 pregnant rats on day 21, being more marked in livers of P2. Increases in Cu and Zn contents in liver were induced during pregnancy, but the values were significantly lower in P2 than in P1. On day 21, no significant differences due to food restriction were noted in serum concentrations of these trace elements, placental weight and placental Fe. However, dam body weight gain, placental Zn and Cu contents were reduced in P2. Foetuses of undernourished dams exhibited at term lower weight and smaller amounts of Fe, Zn and Cu than those in P1. These results confirm that moderate food restriction during pregnancy produces intrauterine growth retardation and that newborns have low trace element contents (particularly in Cu), which make them dependent on correct postnatal supply.

Experimental, geological, and geochemical constraints on the origins of low‐K silicic magmas in oceanic arcs

The results of recent experimental and geochemical studies demonstrate that typical, low‐K, island arc dacites (IAD) and tonalites have liquidus water contents below 6 wt %, while many arc basalts, including evolved, low‐Mg high‐alumina basalt (HAB; H2O ≥ 4 wt%) and magnesian arc tholeiites (H2O ≥ 2 wt %) are water‐rich. If these water contents are typical of arc basalts, fractionation at pressures of 200 MPa or more would produce water‐rich magmas with major element chemical characteristics unlike &gt;99% of observed IAD. In light of this, plausible mechanisms for IAD genesis include (1) dehydration melting of amphibolitized arc crust and (2) low‐pressure (less than 200 MPa) fractionation or assimilation/fractional crystallization (AFC) (accompanied by devolatilization) of hydrous arc basalts. In general, a partial melting origin is favored for tonalitic plutons emplaced at pressures ≥200 MPa, for bimodal suites where geochemistry rules out a genetic relationship between the mafic and silicic end‐members, and for IAD with isotopic characteristics distinct from potential basaltic or andesitic parents. Evidence for partial melting of amphibolite yielding IAD melts has been documented in several ancient island arc complexes. A fractionation origin is favored where there is isotopic homogeneity in a basalt‐dacite system and for dacites having very low concentrations of incompatible trace elements. Bimodal magmatism in general and high concentrations of incompatible elements in silicic magmas appear to favor a partial (batch) melting origin over Raleigh fractionation but can also result from convectively driven batch fractionation processes (Brophy, 1991). Although both fractionation/AFC and partial melting may be legitimately invoked to explain dacitic magmatism in a given situation, a general model must also account for the absence of high‐pressure fractionates of hydrous basalts. This observation seems to favor an important role for amphibolite melting in IAD genesis. It is also possible, however, that physical factors (e.g., neutral buoyancy) promote the formation of basaltic magma chambers in the upper crust or that convective processes, enhanced by large temperature gradients in the upper crust, may favor upper crustal over lower crustal fractionation.

Chemical composition of banded iron-formations of the Griqualand West Sequence, Northern Cape Province, South Africa, in comparison with other Precambrian iron formations

Mesobanded lithotypes (band rhythmites) of banded iron-formation (BIF) from the Griquatown and Kuruman Iron Formations of the Asbestos Hills Subgroup (Transvaal Supergroup, South Africa) have been sampled. 142 major and trace element analyses from diamond drill cores, an underground mine and an open pit mine were carried out. Out of these 19 open pit mine samples were excluded from the interpretation of the analytical results because of a different behaviour of the alkali elements. It is shown that other published data seem to suffer from the same effect. The results show that the chemical composition of the iron-formations is virtually independent of their stratigraphic and geographic localities over hundreds of kilometres across Griqualand West, if averaged element distribution patterns are compared. The major element composition of mesobanded iron-formation samples (magnetite chert and magnetite-carbonate chert, riebeckite-carbonate chert and ironsilicate chert) varies between 30 and 51 wt.% SiO 2, 23 and 66 wt.% Fe 2O 3T, < 0.02 and 0.14 wt.% TiO 2, < 0.04 and 1.9 wt.% Al 2O 3, < 0.02 and 1.05 wt.% MnO, 1.48 and 7.5 wt.% MgO, 0.14 and 12.09 wt.% CaO, 0.11 and 4.26 wt.% Na 2O, < 0.007 and 2.39 wt.% K 2O and < 0.01 and 1.57 wt.% P 2O 5. The trace element contents are generally low and range from < 1 to 2 ppm Nb (detected in only one sample), < 2 to 23 ppm Zr, < 3 to 31 ppm Y, < 2 to 152 ppm Sr, < 4 to 5 ppm U (detected in only one sample), < 2 to 240 ppm Rb, < 4 to 4 ppm Th, < 4 to 19 ppm Pb, < 3 to 4 ppm Ga, < 4 to 33 ppm Zn, < 6 to 69 ppm Cu, < 7 to 17 ppm Ni (detected in only one sample), < 5 to 59 ppm Cr, < 4 to 16 ppm V and < 10 to 177 ppm Ba. The intercalated stilpnomelane lutites have a very similar gross composition but regularly display higher concentrations of Al 2O 3, TiO 2, K 2O, and Zr. They have a different origin but certainly bear the imprint of the BIF environment and must be considered a clastic contaminant of the otherwise chemically or biochemically precipitated iron-formations. Clastic contamination and subsequent hydrothermal alteration are the most plausible agents which effected the element distribution pattern of the BIF, because they are best to reconcile with a model which assumes hydrothermal fluids as major sources of BIF. It can be concluded, from the general geochemical uniformity of BIF throughout the depository and from the absence of clear-cut relations of elemental distributions and ratios to crustal components (documented by low K/Rb, high Rb/Sr ratios, no relevant correlation between TiO 2 and Al 2O 3), that a basinward hydrothermal system acted as a source for the Fe and Si in the BIF. The geochemical similarity between the microbanded Kuruman Iron Formation and the interbedded granular and microbanded Griquatown Iron Formation suggests deposition of the iron-formations in the same chemical environment over the entire basin from the inception of these conditions until their termination by clastic input. The somewhat lower trace element concentrations in the Griquatown Iron Formation as compared to the Kuruman Iron Formation probably do not mean an environmental change, but may reflect the diagenetic and tectonic evolution of the iron-formations. Regular but short-lived interruptions by distal volcanic ash had no influence on the bulk BIF composition. On the contrary, the volcanics reveal a strong overprint by the regional major element BIF chemistry. Therefore, the relationship between volcanogenic rocks and banded iron-formation seems to be coincidental and related to basin development. The general geochemical similarity of the Griquatown and Kuruman Iron Formations with other Proterozoic and Archaean iron-formations in the world and especially with those of the Hamersley Basin, leads us to the conclusion that the BIF of the Griqualand West Sequence are representatives of typical, large-scale iron-formations of the Precambrian, which all formed in chemically very similar environments.

Interstellar graphite in meteorites: Isotopic compositions and structural properties of single graphite grains from Murchison

Abstract— One hundred forty‐three carbon grains, ranging in size from 2 to 8 μm, from two chemical and physical separates from the Murchison CM2 chondrite, were analyzed by ion microprobe mass spectrometry for their C‐ and N‐isotopic compositions. Both separates are enriched in the exotic noble gas component Ne‐E(L). Ninety grains were also analyzed for their H and O contents and 118, for Si. Thirteen grains were analyzed by micro‐sampling laser Raman spectroscopy.Round grains have large C‐isotopic anomalies with 12C/13C ratios ranging from 7 to 4500 (terrestrial ratio = 89). Nitrogen in these grains is also anomalous but shows much smaller deviations from the terrestrial composition, 14N/15N ratios ranging from 193 to 680 (terrestrial ratio = 272). Spherulitic aggregates and non‐round compact grains have normal C‐isotopic ratios but 15N excesses (up to 35%). Raman spectra of the analyzed grains indicate varying degrees of crystalline disorder of graphite with estimated in‐plane crystallite dimensions varying from 18 Å (highly disordered, similar to terrestrial kerogen) to ∼750 Å (well‐crystallized graphite). Element contents of H, O, and Si are correlated with one another, and H and O are probably present in the form of organic molecules. On the basis of morphology, the round grains fall into two groups: grains with smooth, shell‐like surfaces (“onions”) and grains that appear to be dense aggregates of small scales (“cauliflowers”). “Onions” tend to have lower trace element contents, isotopically light C (12C/13C &gt; 89) and a high degree of crystalline order, whereas “cauliflowers” have a larger spread in trace element contents and C‐isotopic ratios (they range from isotopically light to heavy) but tend to have a low degree of crystalline order. However, these differences exist only on average, and no clear distinction can be made for individual grains.A few limited conclusions can be drawn about the astrophysical origin of the carbon grains of this study. The 15N excesses in spherulitic aggregates and non‐round grains can be explained as the result of ion‐molecule reactions in molecular clouds. The round grains, on the other hand, must have formed in stellar atmospheres (circumstellar grains). Grains with isotopically light C must have formed in stellar environments characterized by He‐burning, either in the atmosphere of Wolf‐Rayet stars during the WC phase or in the He‐burning, 12C‐rich zone of a massive star, ejected by a supernova explosion. Isotopically heavy C is produced by H‐burning in the CNO cycle. Possible sources for grains with heavy C are carbon stars (AGB stars during the thermally pulsing phase) or novae, but the detailed distribution of 12C/13C ratios agree neither with the distribution observed in carbon stars nor with theoretical predictions for these two types of stellar sources.

Alteration of uraninite from the Nopal I deposit, Pen˜a Blanca District, Chihuahua, Mexico, compared to degradation of spent nuclear fuel in the proposed U.S. high-level nuclear waste repository at Yucca Mountain, Nevada

At the Nopal I uranium deposit, primary uraninite (nominally UO 2+ x ) has altered almost completely to a suite of secondary uranyl minerals. The deposit is located in a Basin and Range horst composed of welded silicic tuff; uranium mineralization presently occurs in a chemically oxidizing and hydrologically unsaturated zone of the structural block. These characteristics are similar to those of the proposed U.S. high-level nuclear waste (HLW) repository at Yucca Mountain, Nevada. Petrographic analyses indicate that residual Nopal I uraninite is fine grained (5–10 μm) and has a low trace element content (average about 3 wt%). These characteristics compare well with spent nuclear fuel. The oxidation and formation of secondary minerals from the uraninite have occurred in an environment dominated by components common in host rocks of the Nopal I system (e.g. Si, Ca, K, Na and H 2O) and also common to Yucca Mountain. In contrast, secondary phases in most other uranium deposits form from elements largely absent from spent fuel and from the Yucca Mountain environment (e.g. Pb, P and V). The oxidation of Nopal I uraninite and the sequence of alteration products, their intergrowths and morphologies are remarkably similar to those observed in reported corrosion experiments using spent fuel and unirradiated UO 2 under conditions intended to approximate those anticipated for the proposed Yucca Mountain repository. The end products of these reported laboratory experiments and the natural alteration of Nopal I uraninite are dominated by uranophane [nominally Ca(UO 2) 2Si 2O 7·6H 2O] with lesser amounts of soddyite [nominally (UO 2) 2SiO 4·2H 2O] and other uranyl minerals. These similarities in reaction product occurrence developed despite the differences in time and physical—chemical environment between Yucca Mountain-approximate laboratory experiments and Yucca Mountain-approximate uraninite alteration at Nopal I, suggesting that the results may reasonably represent phases likely to form during long-term alteration of spent fuel in a Yucca Mountain repository. From this analogy, it may be concluded that the likely compositional ranges of dominant spent fuel alteration phases in the Yucca Mountain environment may be relatively limited and may be insensitive to small variations in system conditions.

The role of early lithification in development of chalky porosity in calcitic micrites: Upper Cretaceous chalks, Egypt

Petrological and geochemical examination of Upper Cretaceous chalks from the Abu Roash area and Bahariya Oasis (Egypt) provide insights into factors which control porosity development in fine-grained calcitic carbonates. Petrological studies indicate that primary skeletal fabrics of coccoliths and foraminifera in micrites of Abu Roash are well preserved. In contrast, primary skeletal fabrics of the Bahariya Oasis chalks are pervasively altered. Geochemical analysis of these chalks reveals a striking contrast in composition. The high porosity chalks at Bahariya Oasis have depleted isotopic values ( δ 13C = −5.0‰, δ 18O = −8.9‰ PDB ) and low concentrations of trace elements (Sr and Na). In contrast, the low porosity chalks at Abu Roash are less depleted in terms of their isotopic values ( δ 13C = 1.0‰, δ 18O = −4.0‰ ) and possess elevated concentrations of Sr, Na, Fe and Zn. Importantly, fracture and collapse veins, present only at Abu Roash, are filled with calcite whose δ 18O value is coincident with that of altered micrites at Bahariya Oasis. The lithic fragments cemented by this calcite, however, retain compositions identical to other lithified limestones at Abu Roash. Differences in fabric and chemistry of the pelagic marine micrites observed between Abu Roash and Bahariya Oasis reflect the degree of early lithification and compaction prior to exposure and meteoric diagenetic alteration associated with regional Late Cretaceous/pre-Eocene subaerial unconformity.

完全静脈栄養施行中の亜鉛欠乏による発症した皮膚炎の１例

This paper reports a case of dermatitis which was caused by zinc deficiency during total parenteral nutrition (TPN). A 61-year-old male with hemiplegia and dyslalia induced by cerebral hemorrhage developed carcinoma of the maxillary sinus. In spite of intensive cancer therapy, the tumor continued to grow and gradually destroy the tissue of the orofacial area. Since he had dysphagia due to the orofacial tissue defect in addition to hemiplegia and his nutritional state deteriorated, We started TPN. Although TPN improved his poor nutritional state, skin rash and erosion appeared on the face, extremities and perineum about 42 days after starting TPN. The patient's clinical symptoms and the low concentrations of trace elements in blood led us to suspect dermatitis due to trace element deficiency. We started to administer a preparation containing the essential trace-elements intravenously. Consequently, the dermatitis disappeared rapidly and the concentrations of trace elements, particularly zinc, entered the normal range. Therefore, in this case zinc deficiency during TPN most likely caused dermatitis which was cured by the administration of a preparation containing essential trace elements including zinc.

Trace element analysis of Geological Survey of Japan silicate reference materials: Comparison of SSMS with ICP-MS data and a critical discussion of compiled values

The concentrations of 29 trace elements have precisely been determined in 15 international silicate reference materials of the Geological Survey of Japan by spark source mass spectrometry (SSMS) and inductively coupled plasma-mass spectrometry (ICP-MS). The samples span a wide range of concentration levels. Most of the SSMS and ICP-MS values agree within analytical error down to the ppb concentration range. Of particular interest are the data for Nb, Y, Zr, Th, U in samples with low trace element concentrations (<1–10 ppm), for which published data are quite variable. The results obtained generally agree with those of modern sensitive analytical techniques (such as ICP-MS, HPLC), but are often much lower than standard XRF and compiled reference values. It is suggested that these discrepancies arise from calibration and analytical problems for standard XRF and ICP-MS and incorporation of these data into compiled values. More judicious selection of data based on analytical methodology and geochemical behaviour is required for samples which challenge the detection limits of standard analysis.

Mineral elements in the important cultivated mushrooms Agaricus bisporus and Pleurotus ostreatus

The mineral elements of Agaricus bisporus and Pleurotus ostreatus (separately in the caps and stipes of the fruit body) were analysed. The main conclusions are: 1. 1. The classical (conventional) and the new cultivation methods produce different mineral compositions in champignon. The new method (on pure wheat straw) produced lower B, Ca, Cu, Na, Zn and higher K, Fe, Mg, Ni, P and Ti concentrations. 2. 2. The caps of fruit bodies have, in general, greater concentrations of mineral elements than the stipes in both A. bisporus and P. ostreatus. The exceptions are Ba, Cd, Cr, Li and Sr, whose concentrations are approximately identical in caps and stipes). 3. 3. A. bisporus has higher P, K, Ca but lower trace element concentrations than P. ostreatus, which has higher Mg, B, Cd, Fe and Mn concentrations. 4. 4. Accumulation of heavy metals was not found in the samples examined.

Alteration of early-formed dolomite during shallow to deep burial: Mississippian Mission Canyon Formation, central to southwestern Montana

Dolomite in the Mississippian Mission Canyon Formation (Osagean to middle Meramecian) of central and southwestern Montana precipitated during multiple episodes of dolomitization and/or recrystallization. The earliest generation of dolomite most likely precipitated from evaporated sea water in near-surface diagenetic environments when the Mission Canyon platform intermittently aggraded to sea level. This dolomite has relatively positive [delta][sup 18]O values ([minus]1.5% to +7.5%) and typically is nonstoichiometric and trace-element enriched. A second generation of dolomite has very negative [delta][sup 18]O values ([minus]11.2% to [minus]1.5%) and always is stoichiometric and trace-element depleted. Dolomite with [delta][sup 18]O values < [minus]6.8% is in the upper 100-180 m of the Mission Canyon Formation, beneath a regional post-Mission Canyon unconformity and karst surface that extends across the entire study area. Dolomite depleted in [sup 18]O may have (1) precipitated initially in a regional mixing zone during post-Mission Canyon subaerial exposure and karstification, (2) precipitated at elevated temperatures during later diagenesis, or (3) recrystallized from an earlier generation of dolomite during later shallow to deep burial diagenesis. Very negative [delta][sup 18]O values and low trace-element contents for the second generation of dolomite suggest that diagenetic solutions were dominated by meteoric water, whereas [delta][sup 13]C values indicate that diageneticmore » fluids were buffered by Osagean carbonate rocks. 54 refs., 10 figs.« less

Trace-Element Patterns in Fuel Oils and Gasolines for Use in Source Apportionment

Over 30 fuel oils used for power generation in 1980 and 1988 were analyzed for 30 elements by instrumental neutron activation analysis to determine concentration patterns useful in source apportionment. The generally more viscous No. 6 oils contained higher concentrations of most elements than the more refined No. 4 and No. 2 fuel oils for both years. Results indicate that, while many elements in the fuel oils have decreased in concentration during this time, the rare-earth elements (REEs) have remained steady, apparently owing to the continued use of REE-containing catalysts for petroleum refining. Because the fuel oils contained similar REE enrichments and ratios as observed in cracking catalysts and emissions from refineries and oil combustion, their REE signatures are applicable to receptor modeling. Much lower trace-element concentrations were observed in current unleaded gasolines and the REEs appear depleted. 31 refs., 1 fig., 6 tabs.

The heterogeneous Iceland plume: Nd‐Sr‐O isotopes and trace element constraints

We present a comprehensive set of Sr, Nd, and O isotope data and trace element concentrations from tholeiitic and alkaline lavas of the neovolcanic zones of Iceland (picrites, olivine and quartz tholeiites, transitional and alkali basalts, differentiated rocks). Variations in the oxygen isotope results allow us to distinguish two groups. The first, which comprises quartz tholeiites and more differentiated rocks usually associated with central volcanoes, has low δ18O values (+5 to +1‰) resulting from interaction with the hydrothermally altered Icelandic crust. The second group, which contains picrites, olivine tholeiites, and alkali basalts, has normal mantle oxygen isotopic compositions (δ18O = +5 to +6‰) which are thought to represent those of the mantle source. Nd isotopic compositions vary greatly, from 143Nd/144Nd = 0.51314 in picrites to 0.51295 in alkali basalts. To produce such a variation for rocks with the chemical compositions of Icelandic volcanics (147Sm/144Nd = 0.12=0.28) requires &gt;200 m.y., a period that greatly exceeds the maximum age of Icelandic crust. Previous models, in which the Sr isotopic variations were explained in terms of evolution of crustal reservoirs, are invalidated, and mantle reservoirs with different Nd and Sr isotopic compositions are indicated. The Iceland data define a linear array in the Sr‐Nd isotope diagram which overlaps both mid‐ocean ridge basalt and oceanic island basalt fields and indicates mixing between depleted and enriched end‐members. Alkali basalts come preferentially from an isotopically and chemically enriched component of the Iceland plume, and picrites come from a more refractory, more depleted portion. Positive Sr, Rb, and Ba anomalies are present in picrites and other lavas with low trace element contents. These anomalies are not correlated with isotopic differences but are nevertheless believed to result from interaction between the parent magmas of these rocks and altered Icelandic crust. This indicates that even the most primitive Icelandic lavas have been contaminated with some crustal material.

Mantle and crustal contributions to continental flood volcanism

Arndt, N.T., Czamanske, G.K., Wooden, J.L. and Fedorenko, V.A., 1993. Mantle and crustal contributions to continental flood volcanism. In: M.J.R. Wortel, U. Hansen and R. Sabadini (Editors), Relationships between Mantle Processes and Geological Processes at or near the Earth's Surface. Tectonophysics, 223: 39–52. Most continental flood basalts are enriched in incompatible elements and have high initial 87Sr/ 86Sr ratios and low ϵ Nd values. Many are depleted in Nb and Ta. The commonly-held view that these characteristics are inherited directly from a source in metasomatized lithospheric mantle is inconsistent with the following arguments: (1) thermomechanical modelling demonstrates that flood basalt magmas come mainly from an asthenospheric or plume source, with minimal direct melting of the continental lithospheric mantle. The low water contents of most flood basalts argue against proposals that hydrous lithosphere was the source. (2) Lithospheric mantle normally has low concentrations of incompatible elements, and chondrite-normalized Nb and Ta contents similar to those of other incompatible elements. Such material cannot be the unmodified source of Nb-Ta-depleted basalts such as those from the Karoo, Ferrar, or Columbia River provinces. We suggest there are two main controls on the compositions of continental flood basalts. The first is lithospheric thickness, which strongly influences the depth and degree of mantle melting of a plume or asthenospheric source, and thus has an important influence on the composition of primary magmas. All liquids formed by partial melting of peridotite at sub-lithosphere depths are highly magnesian (20–25 wt.% MgO) but have variable trace-element contents. Where the lithosphere is thick, the source melts at high pressure, garnet is present, the degree of melting is low, and trace-element concentrations are high. This type of magma evolves to produce the high-Ti type of continental flood basalt. Where the lithosphere is thinner, the source ascends to shallower levels, the degree of melting is greater, garnet may be exhausted, and the magmas have lower trace-element contents; these magmas yield low-Ti basalts. The second control is processing of magmas in chambers that were periodically replenished and tapped, while continuously fractionating and assimilating their wall rocks. The uniform compositions of basalts that evolve in such chambers are far removed from those of their picritic parental magmas. Major elements in continental flood basalts reflect control by olivine, pyroxene, and plagioclase crystallization, and this assemblage places the magma chambers at crustal depth. We believe that trace-element and isotopic compositions are also buffered, and that the erupted basalts represent steady-state liquids tapped from these magma chambers. These processes impose a crustal signature on the magmas, as expressed most strongly in the concentrations of incompatible elements (e.g., Nb-Ta anomalies) and their isotopic characteristics.

Pontiac metavolcanic rocks within the Cadillac tectonic zone, McWatters, Abitibi Belt, Quebec

The McWatters metavolcanic rocks are structurally bounded lenses within the Cadillac tectonic zone on the southern boundary of the Abitibi greenstone belt. They comprise komatiite, tholeiitic basalt and gabbro, and calc-alkaline andesitic lavas and volcaniclastic rocks cut by calc-alkaline dioritic and lamprophyric dykes. The McWatters basalts are mid-ocean-ridge basalt type tholeiites exhibiting low incompatible trace element contents and [La/Yb]N &lt; 1. They may have formed via relatively high degree partial melting of a rare-earth element depleted mantle source. The andesites exhibit chondrite-normalized trace-element patterns with light-rare-earth and large-ion lithophile element enrichments and negative Nb and Ti anomalies, comparable to those of subduction-related calc-alkaline andesites. McWatters units are distinct from nearby Blake River Group rocks, despite comparable lithological assemblages and some common geochemical characteristics. The McWatters basalts exhibit lower Ti/Y, Zr/Y, and La/Yb than the Blake River tholeiites, whereas the McWatters andesites display lower Ti/Zr and higher Zr/Y than the Blake River calc-alkaline units. The McWatters tholeiites can be correlated with northern Pontiac Group tholeiitic units based on similar trace-element ratios and parallel rare-earth-element patterns. Thus, the McWatters tholeiites represent Pontiac rocks, underthrust beneath the southern Abitibi belt and appearing as isolated and retrograded lenses in the Cadillac tectonic zone. They may represent the remnants of an ocean basin that once separated the southern Abitibi greenstone belt from the Pontiac Subprovince.

Factors influencing the lignin-peroxidase-producing ability of Phanerochaete chrysosporium

The dependence of lignin peroxidase (LiP) activities on agitation was confirmed in medium A containing low vitamin and low trace element concentrations. Vigorous shaking (100 strokes·min−1) caused a total loss of LiP activity, and detergents, having a protective effect on the enzyme activity, could not prevent a substantial reduction in enzyme activity. More important, LiP activity also depends on the maintenance media (potato dextrose agar or malt extract agar) and enzyme production media (carbon- or nitrogen-limited). High losses of LiP activity were observed by subsequent subculturing. Even storage of the inoculum on the maintenance media at 4° C, although better than subculturing, was not advisable. After long storage periods (50–75 weeks) at 4° C, LiP could not be reactivated in “poor” medium A, containing low amounts of vitamins and trace elements. In “rich” medium B, containing higher amounts of vitamins and trace elements, even after long storage periods, LiP activity was higher than when the activity was measured in “poor” medium A before storage.