Elevated Concentrations Of Sr Research Articles

Salt and Metal Tolerance Involves Formation of Guttation Droplets in Species of the Aspergillus versicolor Complex.

Three strains of the Aspergillus versicolor complex were isolated from a salty marsh at a former uranium mining site in Thuringia, Germany. The strains from a metal-rich environment were not only highly salt tolerant (up to 20% NaCl), but at the same time could sustain elevated Cs and Sr (both up to 100 mM) concentrations as well as other (heavy) metals present in the environment. During growth experiments when screening for differential cell morphology, the occurrence of guttation droplets was observed, specifically when elevated Sr concentrations of 25 mM were present in the media. To analyze the potential of metal tolerance being promoted by these excretions, proteomics and metabolomics of guttation droplets were performed. Indeed, proteins involved in up-regulated metabolic activities as well as in stress responses were identified. The metabolome verified the presence of amino sugars, glucose homeostasis-regulating substances, abscisic acid and bioactive alkaloids, flavones and quinones.

The occurrence and distribution of strontium in U.S. groundwater

Groundwater samples from 32 principal aquifers across the United States (U.S.) provide a broad spatial scope of the occurrence and distribution of strontium (Sr) and are used to assess environments and factors that influence Sr concentration. Strontium is a common trace element in soils, rocks, and water and is ubiquitous in groundwater with detectable concentrations in 99.8% of samples (n = 4,824; median = 225 μg/L). Concentrations in 2.3% of samples exceeded the 4,000 μg/L health-based screening level. The relative importance of controlling factors on Sr concentration are spatially variable and partly dependent on the type of groundwater well. Three case settings illustrate controls on Sr concentration. For drinking-water supply wells, most high concentrations (>4,000 μg/L) were measured in samples from carbonate aquifers that resulted from water-rock interaction with Sr-bearing rocks and minerals. High Sr concentrations from monitoring wells were more common in unconsolidated sand and gravel aquifers in arid or semi-arid setting where shallow groundwater is affected by irrigation and evaporative concentration of dissolved constituents in combination with lithologic or applied Sr sources. Upwelling saline groundwater is also a source of Sr in some locations. Total dissolved solids concentration is an indicator of high Sr in all settings. An estimated 2.2 million people in the conterminous U.S. are potentially supplied water from public-supply wells with high Sr concentration, ~86% of whom use carbonate aquifers (with more than half supplied by the Floridan aquifer system). An additional 120,000 people are potentially supplied high-Sr-concentration water from domestic wells, more than half of whom (~58%) are in Texas. This study markedly expands the coverage of previous surveys of Sr in groundwater and is of interest given potential adverse human-health effects related to elevated concentrations of Sr and consideration of Sr for drinking-water regulation. Case settings with elevated Sr described for U.S. groundwater are likely indicative of settings and processes affecting Sr concentration in groundwater globally.

Origins and mixing contributions of deep warm groundwater in a carbonate-hosted ore deposit, Sichuan-Yunnan-Guizhou Pb-Zn triangle, southwestern China

Sichuan-Yunnan-Guizhou (SYG) carbonate-hosted Pb-Zn triangle is a world-class metallogenic belt and classified as Mississippi Valley-Type (MVT), which provides the greatest ore production in China. However, little is known about the effects of water-rock interactions involving the ore deposits and the modern hydrologic system. Measured chemical and isotopic compositions of the deep groundwater are used to evaluate water origins, potential circulation depth, reaction temperatures, and mixing process with shallow groundwater to assess possible linkages between regional hydrogeology and ore deposits. Within the Maoping sub-deposit, deep groundwater is warmer (21.2–32.0 °C), has lower pH, higher HCO3− and SO42− concentrations, higher average 87Sr/86Sr ratio (0.7148) and Sr concentration (4.1 mg/L), more positive δ13CDIC values (−4.5 to −4.2‰), and lighter average isotopic value (δD = −98 and δ18O = −13.7‰) relative to shallow groundwater, suggesting an origin distinct from modern surface recharge. The light isotopic composition of the deep warm water indicates recharge at a cooler temperature in the past, perhaps during the Last Glacial Maximum. The δ13CDIC values reflect isotopic equilibrium between deep groundwater and surrounding rocks along with a possible deep source of CO2. The oxidation process of sulfides, including H2S and pyrite linked to the ore-forming processes, could produce sulfuric acid that enhances carbonates dissolution and generates elevated HCO3− and SO42− concentrations. Reaction temperatures for the deep groundwater appear to have been around 50–65 °C based on quartz geothermometers and given a regional geothermal gradient of 24.1 °C/km suggest reactions occurred at depths ~1900 m below the land surface. Elevated Sr concentrations with radiogenic Sr isotope ratios reflect reaction with basement rocks and carbonates during the deep circulation. Sr concentration and isotope mixing models demonstrate different recharge sources and suggest the contribution of deep warm groundwater captured in mine drainage. These results reflect the importance of deep groundwater circulation and reactions in a large ore deposit that may improve understanding of potential effects of these important ore bodies on regional water compositions in the SYG triangle and other MVT ore deposits.

Picrites of the Jungfrau and Sargdeckel, central Namibia: Relative roles of mantle and crust in the Southern Etendeka large igneous province

A suite of doleritic rocks from the Jungfrau and Sargdeckel hills of Karibib form part of the southern Etendeka Province of Central Namibia. The dolerites occur as sills or thick lava flows and are classified as picrites based on high MgO contents (15–26 wt.%) and the presence of skeletal olivine. Both Jungfrau and Sargdeckel picrites are characterized by low TiO2 contents (0.32–0.61 wt.%) and plot in the field of low-Ti magmas of the Etendeka flood basalts. The high MgO, Ni, and Cr whole-rock contents suggest that olivine and chromite accumulation occurred. Elevated Sr concentrations and positive Eu-anomalies in the Sargdeckel picrites indicate additional plagioclase accumulation.REE patterns of the picrites range from 5 to 30 times chondritic values, are slightly REE-enriched ([La/Yb]N ranges from 2.3 to 3.2), and have small Eu-anomalies (0.93–1.12). Multielement patterns (normalized to primitive mantle) show marked positive Sr and Ba anomalies relative to Th, U and Rb and negative Nb and Ti anomalies resulting in high LILE/HFSE ratios. 87Sr/86Sr and 143Nd/144Nd ratios in Jungfrau and Sargdeckel picrites exhibit an inverse covariation, with 87Sr/86Sr ranging from 0.70937 to 0.71322 and εNd from −7.2 to −8.7.All picrites exhibit a crustal signature characterized by the enrichment of LILE relative to HFSE, negative Nb-anomalies, radiogenic Sr and unradiogenic Nd isotopes. However, it is predominantly the picrites with the highest Mg#’s and compatible elements that show the more pronounced crustal signature and the lowest Nd- and the highest Sr-isotope ratios. Hence, it seems unlikely that the crustal signature seen in the picrites is the result of combined assimilation and fractional crystallization or direct interaction with continental crust. Altogether, the combined major and trace element, and isotope data suggest that the picrites are derived by plume-induced melting of the local metasomatized subcontinental lithospheric mantle, similar to the source of Horingbaai dolerites, that has been variable enriched with a crustal component that was likely introduced into the mantle during Neoproterozoic subduction.

Effects of 90Sr on Tree Swallow Nestlings Near Groundwater Contaminant Plumes.

Discharge of groundwater contaminant plumes has created elevated concentrations of Sr in some aquatic sediments at Chalk River Laboratories. Tree swallows (Tachycenita bicolor) feed and supply their nestlings almost exclusively with airborne insects that developed as larvae in aquatic sediments. To monitor the uptake and test for potential detriment due to Sr in a terrestrial animal, we measured the gross beta concentrations in the bone of 12-d-old tree swallow nestlings in areas having sediments with elevated levels of gross beta (Sr and Y) and in several control areas where sediment gross beta was primarily due to naturally occurring K. Nesting behavior and reproductive success of the tree swallows were similar regardless of the gross beta concentrations in sediments near their nest boxes. Radiation can damage DNA and cause micronuclei to form in cells, so we examined the frequency of micronuclei in erythrocytes of nestlings. The formation of micronuclei in the erythrocytes of the nestlings was also similar wherever nestlings were analyzed. The results revealed no significant increases even near sediments with the highest gross beta levels. At Perch Lake, where Chalk River Laboratories has a large area of Sr-contaminated sediments, the bones of 12-d-old nestlings contained gross beta concentrations as high as 29 Bq g. This would produce a skeletal dose rate of 9 μGy h, which is one-fourth of the threshold dose rate of 40 μGy h, above which detriment could occur. Failing to find any indication of detriment in the field study, we irradiated wild eggs in the lab and returned them to their nest for natural incubation, hatching, and feeding by the parents. There was an increase in formation of micronuclei following a dose of 3.2 Gy, and the other results were consistent with existing literature.

Seaweed fertilisation impacts the chemical and isotopic composition of barley: Implications for analyses of archaeological skeletal remains

Fertilisation with animal manure has been shown to affect crop chemical and isotopic composition, indicating that if manuring effects are not taken into account, there is a risk of overestimating consumer trophic levels in palaeodietary studies. The effect of fertilisation with seaweed, a common fertiliser in the past in coastal areas, has been the subject of several hypotheses, but until now has not been studied in this particular context.In this study the impact of fertilising bere, an ancient type of Scottish barley (Hordeum vulgare L.), with 25 t/ha and 50 t/ha seaweed, in comparison to a modern commercial mineral fertiliser and to no fertilisation, was investigated in a field trial on the Orkney Islands, Scotland. Stable isotope ratios (δ13C and δ15N) and elemental concentrations (B, Mg, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Mo, Cd and Pb) of grain, husk and straw samples were determined. Significant differences were found between treatment groups, including increases in δ15N values of 0.6 ± 0.5‰ (average ± 1σ for five replicate plots) in grain, and 1.1 ± 0.4‰ in straw due to seaweed fertilisation. Elevated concentrations of Sr in grain and husk samples (factors of 1.2–1.4) indicate the geographic tracer 87Sr/86Sr may also be affected.Fertilisation with seaweed thus needs to be considered for archaeological interpretations of chemical and isotopic compositions of crop and skeletal material for accurate palaeodietary and provenance reconstructions, particularly in coastal areas. Further implications of these results for studies concerning the effects of sea spray, radiocarbon-dating, and for dietary reconstructions using trace elements are also identified.

Examining the interplay of climate and low amplitude sea‐level change on the distribution and volume of massive dolomitization: Zebbag Formation, Cretaceous, Southern Tunisia

AbstractDuring the Cretaceous, a humid global climate, calcitic seas, high relative sea‐level and low amplitude changes in relative sea‐level largely prevented large‐scale dolomitization in many carbonate successions. However, the well‐exposed shallow‐water carbonate sediments of the Upper Albian–Lower Turonian Zebbag Formation on the Jeffara Escarpment, southern Tunisia, are pervasively dolomitized. This study considers why dolomitization was so widespread in this region during a period of Earth history when platform‐scale dolomitization is rare. Marine conditions were established in the Upper Albian, evidenced by stacked upward‐shallowing packages of shallow subtidal to peritidal carbonate sediments in the basal Rhadouane Member. A gradual increase in the volume of subtidal sediments in the Cenomanian Kerker Member, culminated in deposition of laterally extensive marls, during maximum flooding of the platform in the Lower Turonian. The overlying Gattar Member was then deposited in shallower water as relative sea‐level fell. The entire Zebbag Formation is pervasively replaced by stratabound, fabric‐retentive, dolomite, except within the marl at the top of the Kerker Member, which is only partially dolomitized. Petrographic textures indicate dolomitization largely post‐dated marine cementation and platform emergence but pre‐dated chemical compaction. Slightly more positive oxygen isotope signatures, slightly elevated concentrations of Sr and a near‐absence of evaporites are consistent with dolomitization by reflux of mesohaline sea water. An upward‐decrease in major element concentrations and higher 87Sr/86Sr compared to Upper Cretaceous sea water suggest that basal, Albian siliciclastic beds acted as aquifers facilitating dolomitization by fluxing fluids offshore. Dolomitization is interpreted to have resulted from multiple fluxes of sea water over periods of 0·5 to 2·5 Ma. The unusually high volume of dolostone for a platform of this age most probably reflects deposition within an arid climate belt, where an efficient reflux system was facilitated by basal, permeable siliciclastic strata.

Can dietary reliance on Pacific salmon eggs create otolith Sr/Ca signatures that mimic anadromy in resident salmonids?

Many aspects of the ecology, growth, life history, and population dynamics of fishes differ between anadromous populations and those residing exclusively in freshwater habitats. Analysis of the elemental composition of otoliths (ear stones) is commonly used to indicate the migration history of individuals, relying on the differences in ambient concentrations of calcium, strontium, and barium and their subsequent incorporation into calcified structures. Dietary contribution to otolith chemistry is often overlooked, but in this study we report results consistent with the possibility that reliance on food resources derived from the ocean via Pacific salmon can produce otolith Sr/Ca ratios suggesting anadromy in freshwater resident fish. Dolly Varden, Salvelinus malma, from the Iliamna River, Alaska feed very heavily on eggs and other tissues from sockeye salmon, Oncorhynchus nerka, and their otoliths had Sr/Ca ratios typical of fish making seasonal migrations to marine waters but the Ba/Ca ratios were consistent with residence in fresh water. Water samples from the river provided no indication that the elevated Sr concentrations came from the river. A simulation of otolith chemistry resulting from Sr incorporation from both water and diet across a range of published values in salmonids indicates that a diet of salmon eggs and tissues can produce marine Sr/Ca ratios while fish remain in fresh water. Without experimental evidence such as a controlled diet study these results are suggestive but not conclusive. Nevertheless, they send a cautionary note that in some cases heavy reliance on marine-derived food sources might affect otolith microchemistry, creating an appearance of anadromy in fish that did not leave fresh water.

Identifying ancient manuring: traditional phosphate vs. multi-element analysis of archaeological soil

Elevated soil phosphorus levels are often used as indicators for prehistoric manuring. However, in this article it is argued that though P is indeed a good anthropogenic marker, multi-element analyses can provide more insight into former fertilisation practices and land use.Here, we compare the ability of both traditional total P analysis and multi-element analysis by ICP-MS to identify prehistoric manuring on soil samples from a well-preserved prehistoric Celtic field system in Denmark. The ICP-MS data set of 58 soil samples was furthermore analysed by multivariate analysis (PCA). Results show that the stronger extraction for the multi-element analysis releases significantly more P than the traditional analysis but similar archaeological interpretations based on relative P enrichments can be made. Among the 42 analysed elements, 11 were significantly (P < 0.01) enhanced in the fields relative to a reference soil, namely Na, P, K, Ca, Mn and Sr and the rare earth elements (REE's), Nd, Sm, Eu, Gd and Dy. Cobalt was the only element which was depleted within the field system. Enhanced P levels show that manuring was practiced, while elevated concentrations of Sr indicate that not only animal manure but also bones/domestic waste was added. Furthermore, the enhancement pattern of some major and minor elements indicate that unweathered subsoil was incorporated into the topsoil – probably through tillage erosion until approximately 2000 years ago. The study also indicates that the banks demarcating the individual fields were made of the same material as the field plough-layers, which makes within-field soil relocation the most likely cause of the banks.

Seasonal and ontogenic migrations of meagre (Argyrosomus regius) determined by otolith geochemical signatures

Argyrosomus regius uses different water masses during its life history, being associated with estuaries for reproduction. In order to study the life history and migration patterns, variations in otolith Na, Sr and Ba were measured by laser ablation-ICPMS along transects running from the first year of life to the otolith edge, comprising up to 12 years of age. Visual and statistical modelling approaches were used to analyse both individual- and population-level patterns. Ontogenetic trends in Sr:Ca and Ba:Ca followed a sigmoidal increase over the life span, with an inflection point in Sr:Ca occurring at 5 years of age in males and 6.6 in females, suggesting respective age at maturity. Using reared young-of-year (YOY) meagre for validation, the habitat use of wild fish was characterized and our data suggest that most fish spend the first 2–4 years in offshore waters, and begin moving between water masses after age 6. Population-level analyses indicated significant seasonal variations, with a larger proportion of fish with high otolith Sr:Ca in the spring and summer. Although Sr:Ca would normally be expected to be lower after movement into estuaries, in this case the increase could mark gonad maturation and spawning activity. Alternatively, since the Sr:Ca maxima correspond to higher otolith Ba:Ca in the summer, fish would have moved into the estuarine area, especially since the Guadalquivir river drains metal-rich areas with heavy mining activities leading to elevated Sr concentrations compared to adjacent coastal waters.

Exploring typhoon variability over the mid-to-late Holocene: evidence of extreme coastal flooding from Kamikoshiki, Japan

Sediment cores from two coastal lakes located on the island of Kamikoshiki in southwestern Japan (Lake Namakoike and Lake Kaiike) provide evidence for the response of a backbarrier beach system to episodic coastal inundation over the last 6400 years. Sub-bottom seismic surveys exhibit acoustically laminated, parallel to subparallel seismic reflectors, intermittently truncated by erosional unconformities. Sediment cores collected from targeted depocenters in both lakes contain finely laminated organic mud interbedded with coarse-grained units, with depths of coarse deposits concurrent with prominent seismic reflectors. The timing of the youngest deposit at Kamikoshiki correlates to the most recently documented breach in the barrier during a typhoon in 1951 AD. Assuming that this modern deposit provides an analog for identifying past events, paleo-typhoons may be reconstructed from layers exhibiting an increase in grain-size, a break in fine-scale stratigraphy, and elevated Sr concentrations. Periods of barrier breaching are concurrent with an increase in El Niño frequency, indicating that the El Niño/Southern Oscillation has potentially played a key role in governing typhoon variability during the mid-to-late Holocene. An inverse correlation is observed between tropical cyclone reconstructions from the western North Atlantic and the Kamikoshiki site, which may indicate an oscillating pattern in tropical cyclone activity between the western Northern Atlantic and the western North Pacific, or at least between the western Northern Atlantic and regions encompassing southern Japan. The two kamikaze typhoons which contributed to the failed Mongol invasions of Japan in 1274 AD and 1281 AD occur during a period with more frequent marine-sourced deposition at the site, suggesting that the events took place during a period of greater regional typhoon activity.

Amino acid composition, petrology, geochemistry, 14C terrestrial age and oxygen isotopes of the Shişr 033 CR chondrite

Abstract— We have analyzed Shişr 033, a CR chondrite from the Omani desert, using several different analytical techniques designed to study the degree of terrestrial alteration of this meteorite and also its petrologic classification. Bulk chemical analyses (including organic carbon and mean total H2O content) are consistent with a CR classification. Additionally, oxygen isotope analysis on a bulk sample indicates that Shişr 033 is of type CR2. Amino acid analysis using liquid chromatography with UV fluorescence detection (HPLC‐FD) and liquid chromatography‐time of flight‐mass spectrometry (LC‐ToF‐MS) show that the absolute and the relative amino acid content of Shişr 033 is distinct from other carbonaceous chondrites. Oxygen isotope analysis of a phyllosilicate‐rich dark inclusion shows that this inclusion is closer to CV3 or CO3 chondrites. The effects of terrestrial weathering in Shişr 033 are evident from the dark inclusion carbon isotopic data, bulk chemistry (through the elevated concentrations of Sr and Ba), and amino acid data, which suggests extensive amino acid contamination of the meteorite from the fall site soil. Nevertheless, Shişr 033 contains a small fraction of indigenous components, as indicated by the presence of the extraterrestrial amino acid α‐aminoisobutyric acid (AIB) that was not detected in the Shişr soils. Finally, the terrestrial age of Shişr 033 was determined and is discussed in the context of high levels of contamination.

228Ra/ 226Ra and 226Ra/Ba ratios to track barite formation and transport in the water column

We measured 228Ra ex/ 226Ra ex and 226Ra ex/Ba ex ratios in suspended and sinking particles collected at the Oceanic Flux Program (OFP) time-series site in the western Sargasso Sea and compared them to seawater ratios to provide information on the origin and transport of barite (BaSO 4) in the water column. The 228Ra ex/ 226Ra ex ratios of the suspended particles down to 2000 m are nearly identical to those of seawater at the same water depth. These ratios are much lower than expected if suspended barite was produced in surface waters and indicate that barite is produced throughout the mesopelagic layer. The 228Ra ex/ 226Ra ex activity ratios of sinking particles collected at 1500 and 3200 m varied mostly between 0.1 and 0.2, which is intermediate between the seawater ratio at these depths (<0.03) and the seawater ratios found in the upper 250 m (0.31–0.42). This suggests that excess Ba (i.e., Ba ex = Ba total − Ba lithogenic), considered to be mainly barite, present in the sinking flux is a mixture of crystals formed recently in the upper water column, formed several years earlier in the upper water column, or formed recently in deeper waters. We observe a sizeable temporal variability in the 228Ra ex/ 226Ra ex ratios of sinking particles, which indicates temporal variability in the relative proportion of barite crystals originating from surface (with a high 228Ra ex/ 226Ra ex ratio) and mesopelagic (with a low 228Ra ex/ 226Ra ex ratio) sources. However, we could not discern a clear pattern that would elucidate the factors that control this variability. The 226Ra/Ba ratios measured in seawater are consistent with the value reported from the GEOSECS expeditions (2.3 dpm μmol −1) below 500 m depth, but are significantly lower in the upper 500 m. High 226Ra ex/Ba ex ratios and elevated Sr concentrations in suspended particles from the upper water column suggest preferential uptake of 226Ra over Ba during formation of SrSO 4 skeletons by acantharians, which must contribute to barite formation in shallow waters. Deeper in the water column the 226Ra ex/Ba ex ratios of suspended particles are lower than those of seawater. Since 228Ra ex/ 226Ra ex ratios demonstrate that suspended barite at these depths has been produced recently and in situ, their low 226Ra ex/Ba ex ratios indicate preferential uptake of Ba over Ra in barite formed in mesopelagic water.

Heavy metals and metalloids in egg contents and eggshells of passerine birds from Arizona

Concentrations of inorganic elements were determined in eggs of passerine birds including the endangered southwestern willow flycatcher ( Empidonax traillii extimus) from four regions in Arizona. The main aim of the study was to determine the distribution of metals in egg contents and eggshells, with emphasis on the deposition of Sr in eggshells. Seventy eggs of 11 passerine species were collected at four nesting locations during 2000. Aluminum, Ba, Cr, Cu, Mn, Se, Sr, and Zn, were detected primarily in egg contents of all bird species. Arsenic, Ni, Pb, and V were detected primarily in eggshells. A proportion of most inorganic elements accumulated in the eggshell. Concentrations of Ba, Cu, Mn, Se, Sr, and Zn in egg contents and As, Ba, Cu, and V in eggshells of yellow-breasted chats ( Icteria virens) were similar among locations. However, concentrations of Mn, Ni, Sr, and Zn in eggshells were significant different among locations. Except for Cu, Mn, Se, and Zn, concentrations of inorganic elements were 2–35 times greater in eggshells than in eggs. Most concentrations of metals and metalloids in eggs and eggshells of all the bird species were below levels known to affect reproduction or that have other deleterious effects. However, I found somewhat elevated concentrations of Sr in eggshells (highest mean=1505 μg/g dw, n=3) of yellow-breasted chats and willow flycatchers, and in egg contents of yellow warblers ( Dendroica petechia) and song sparrows ( Melospiza melodia). Whether current observed concentrations of Sr in eggshells are affecting nesting birds in Arizona remains to be determined. Strontium and other metals could be associated with lower hatching success in some areas. This study shows that a proportion of many inorganic elements accumulates in the eggshell and that the potential effects on the proper structure and functioning of the eggshell should not be ignored.

Genetic significance of the trace element content in metamorphic and hydrothermal quartz: a reconnaissance study

A reconnaissance study on trace elements in metamorphic and hydrothermal quartz was carried out using quartz samples from the tin district Erzgebirge, Germany, the gold mineralization at Kašperské Hory, Czech Republic, and the gold-quartz vein deposits Muruntau and Myutenbai, Uzbekistan. A new method of sample preparation has been developed to prepare pure quartz samples by combining conventional hand-picking with microscopic and spectroscopic studies as well as acid wash/etch procedures. Preparation of monomineralic samples was followed by sample dissolution and measurement by ICP-MS. The metamorphic quartz has very low concentrations of Li (≤0.4 ppm), Al (≤30 ppm), K (≤35 ppm), Rb (≤50 ppb), Sr (≤0.3 ppm), and Y (≤15 ppb). Moreover, it is characterized by light rare earth element enriched lanthanide distribution patterns lacking Eu anomalies. The low element concentrations in metamorphic quartz are interpreted to result from recrystallization. Metamorphic quartz from alteration halos enveloping tin and gold deposits has distinctly different trace element signatures. These differences are related to the hydrothermal overprint of the pre-existing metamorphic quartz by the mineralizing fluids. Hydrothermally altered metamorphic quartz from tin deposits has elevated concentrations of Li (≥0.9 ppm), Al (≥50 ppm), K (≥45 ppm), Rb (≥250 ppb), and Y (≥40 ppb) whereas altered metamorphic quartz from gold deposits is characterized by elevated concentrations of Sr (≥0.5 ppm). The rare earth element distribution patterns of altered metamorphic quartz show variable enrichments of the heavy rare earth elements and frequently display positive Eu anomalies. Hydrothermal vein quartz from the gold deposits usually has elevated Al (≥50 ppm) and Sr (≥0.6 ppm) contents. The lanthanide distribution patterns exhibit variable enrichments of the heavy rare earth elements and commonly show positive Eu anomalies. The elevated Sr concentrations in the quartz from gold deposits are best explained by Sr release during feldspar alteration in the wall rocks. This mechanism may also account for the relative enrichment of Eu in the mineralizing fluids although other processes may not be unambiguously ruled out.

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.

Geochemistry of orbicular diorite from the Grenville Front zone, eastern Labrador

AbstractOrbicules in diorite from the Grenville Front zone of eastern Labrador consist of biotite- and/or hornblende-studded, dioritic cores enclosed by fine-grained shell structures alternately enriched and depleted in biotite. The orbicules occur in a mesocratic, quartz-bearing matrix. Epidote of inferred magmatic origin occurs in all parts of the rock. Plagioclase in the matrix is relatively sodic, and biotite more ferroan than in the orbicules, suggesting that the matrix material has the most evolved composition, and crystallized last.The diorite is unusually aluminous (orbicules: 24.9-27.4 wt.% Al2O3; matrix: 22.4-23.6% Al2O3) and calcic (orbicules: 7.0-8.4 wt.% CaO; matrix: 6.0-6.9% CaO); it shows a positive Eu anomaly, and has elevated Sr concentrations (1800-2500 ppm Sr), demonstrating that, compositionally, it resembles a plagioclase cumulate. Mass-balance calculations suggest that the orbicule cores had a crystal/melt ratio of ≤5. This accounts for the extreme fractionation of the rock (e.g., in orbicules, Zr &lt;5 ppm). Compared with fractional crystallization patterns, variation diagrams show counter-trends (e.g. the siliceous matrix contains elevated TiO2) or scatter for several components, suggesting that the crystal/melt ratio governed some of the geochemical characteristics of the diorite.The presence of coarse mafic clots containing primary epidote, biotite and/or hornblende testify to an elevated water content in the orbieule cores. The shell magma apparently formed as a result of the interaction of supercooled orbicule core fluids with the matrix magma, and tended to serve as a reservoir for alkalis and Fe. Alkalis and Ca diffused in opposite directions, possibly as a result of a temperature gradient at the orbicule/matrix interface. This, however, requires decoupling of the thermodiffusional behaviour of alkalis and femic components in hydrated intermediate magma, which contrasts with documented Soret diffusion in mafic systems.The solidification of the shell magma prior, to the orbicule cores and matrix is attributed to dewatering, consistent with the fine grain size of the shell structures. Except where remobilized core material has disrupted the shells, the cores crystallized in isolation from the matrix, which fractionated toward a more evolved composition.

Regional Variations in 87Sr/86Sr and Sr Concentration of Formation Fluids, San Joaquin Basin, California

Formation fluids from the San Joaquin basin can be divided into three geographic provinces based on {sup 87}Sr/{sup 86}Sr ratios and Sr concentrations. Connate marine fluids from the central basin have {sup 87}Sr/{sup 86}Sr ratios between 0.7070 and 0.7080, and Sr concentrations between 15 and 200 mg/l. These results are interpreted in terms of the mixing of Tertiary seawater Sr with Sr derived from Sierra Nevada plagioclase by dissolution and albitization reactions. Fluids from albitized reservoirs can be further distinguished by both elevated Sr concentrations and strongly modified Ca/Na ratios. Meteoric fluids from the eastern flank of the basin have {sup 87}Sr/{sup 86}Sr rations between 0.7061 and 0.7077, and Sr concentrations less than 2 mg/1. The isotopic ratios suggest that plagioclase dissolution is the dominant source of Sr in these fluids. Fluids from the southern basin have anomalously high {sup 87}Sr/{sup 86}Sr ratios (>0.7080), although Sr concentrations are comparable to fluids from the central basin. Stable isotopic and chemical data show that the southern basin fluids are of marine or mixed marine-meteoric origin. The elevated {sup 87}Sr/{sup 86}Sr ratios suggest that an Sr source more radiogenic than Sierran plagioclase is involved in the evolution of these waters to a muchmore » larger extent than elsewhere in the basin. Possible Sr sources include Tertiary marine carbonate, detrital smectite, and K-feldspar. The fluid provinces outlined here limit the scale of lateral fluid communication to distances less than 10 km. Isotopic variations also occur within individual fields; in these cases, the scale of fluid communication may be much smaller.« less

Activation of contractility and occurrence of aftercontractions in ca 2+ and sr 2+-solutions during the postnatal development of the rat heart

1. 1. Activation of isometric contractile force and induction of aftercontractions by different extracellular Ca- and Sr-concentrations during the early postnatal development of the rat heart were studied. 2. 2. In the neonatal (1–15 days) rat heart activation of contractility by [Ca] 0 and [Sr] 0 were similar when a dose-response curve for Ca was determined before Sr, but if the experiment was performed in the reverse order of the dose-response curve for Sr was shifted to the left. In either case the maximal developed tension was about the same. 3. 3. In the adult (3–5 months) rat heart [Ca] 0 higher than 4 mM was inhibitory, whereas contractile force increased up to 16mM [Sr] 0 without any signs of force depression. 4. 4. The dose-response curve for Sr was shifted to the right compared to that of Ca and the maximal developed tension was clearly higher in Sr-solution than in Ca-solution. 5. 5. Aftercontractions appeared for the first time on the 13th and 24th postnatal days for 16 mM [Ca] 0 and [Sr] 0, respectively. 6. 6. In the adult rat ventricle lower Ca concentrations were needed to induce aftercontractions compared to Sr. 7. 7. Based upon these observations it is suggested that the appearance of aftercontractions during the third postnatal week of rat heart development is due to the maturation of intracellular Ca stores which become available for contractile activation by the development of the T-system. 8. 8. The absence of a negative inotropic effect in elevated Sr concentrations may be due to the slowing down of the transport processes of the sarcoplasmic reticulum (SR) by Sr and to the greater ability of the SR to store Sr over Ca.