Enrichment Of Na Research Articles

Major and trace element variations in oxide and titanate minerals in the West Kimberley lamproites, Western Australia

New data are presented for groundmass chromian spinel, perovskite, ilmenite, and K-Ti-Ba-rich phases from the Miocene olivine and leucite lamproites of the West Kimberley region. The spinels range from early Ti-Al-Mg chromite through Ti-Mg chromite to Ti-chromite and, in Ellendale 4 and 9, Ti-Cr magnetite and Ti-magnetite. Most crystallized at 850–1220 °C and fO2 ~ MW + 1–2 log units except for Ellendale 4 and 9 spinels which underwent marked late oxidation at ~650–750 °C with fO2 increasing sharply to ~FMQ + 2–3 log units. Perovskite is ubiquitous in the olivine lamproites and the Walgidee Hills (WH) lamproite. Compositional features of the perovskite are a wide range in Cr, and high Sr, Nb, Th, and LREE contents with highly fractionated REE patterns (La/YbCN ~ 750–3000). Perovskite from WH defines an evolutionary trend of enrichment in Na, Sr, Y, Nb, U and REE, and depletion in Cr, Fe, and Th with magma fractionation. Late crystallizing WH perovskite shows a decrease in LREE due to relative depletion of LREE in residual magma by extended crystallization of perovskite (and apatite). Priderite ((K,Ba)(Ti,Fe3+)8O16) has low Mg and V, and a range in Cr contents which decrease with magma evolution. Jeppeite ((K,Ba)2(Ti,Fe)6O13), has higher Sr and Nb content than priderite. Both contain low Y and REEs. Wadeite (K2ZrSi3O9), a ubiquitous groundmass phase, has high Sc, Rb and Hf contents, and strongly LREE-depleted REE patterns with positive Ce anomalies. Noonkanbahite, a late crystallizing phase in WH, has low Cr and Ni, and high Sr, Nb and Y contents. REE patterns for noonkanbahite display high HREE, depleted MREE, enriched La-Ce-Pr, and a positive Eu anomaly.

Rare-earth, yttrium and zirconium mobility associated with the uranium mineralisation at Okrouhlá Radouň, Bohemian Massif, Czech Republic

The mobility of rare-earth elements (REE), Y and Zr during the Late-Variscan and post-Variscan mineralisation event in the Okrouhla Radouň uranium deposit has been investigated to elucidate their behaviour during the hydrothermal alteration of leucogranites and high-grade metamorphic rocks in the Moldanubian Zone (Bohemian Massif). The alteration of leucogranites has caused enrichment in Na, Ca, Fe 3+ , Zr and the bulk of REE while depleting K, Fe 2+ , Si, Th, Rb and Ba. The alteration of high-grade metasediments has also led to an enrichment in Na and Ca while depleting K, Si, Rb and Ba. However, this change is connected to the depletion of REE, as well as the enrichment of P and Th in the bulk. The high mobility of Y and Zr during formation of the uranium mineralisation is supported by the occurrence of Y- and Zr-rich coffinite (up to 3.4 wt.% Y 2 O 3 and 13.8 wt.% ZrO 2 ). The massive hydrothermal alteration of host rocks, as well as the high mobility of REE, Y and Zr indicate an influx of oxidised basinal fluids in the Permian to the crystalline rocks of the Moldanubian Zone.

Evaluating Groundwater Pollution Using Hydrochemical Data: Case Study (Al Wahat Area East of Libya)

Water is one of the most challenging current and future natural resources, which will directly affect the environment and development by the changes in its quantity, quality and regional distribution. However, Water quality is the critical factor that influences human health and irrigation proposer. This work aims to investigate hydrochemical analysis and geochemical processes influencing the groundwater of Al Wahat area (Jalou, Awjla and Jukherra), which is located in central east Libya. Thirty four water samples collected from domestic and agricultural water wells were analyzed and used for conventional classification techniques which were Piper, Durov and Stiff diagrams to evaluate geochemical processes. Cluster analysis was used to identify the water type and ions concentration and distribution. Results show significant increase of dissolved salts, especially Nitrates. Elevated nitrates concentration can be attributed to either the disposal of untreated sewage water from disposal ponds and septic tanks or the infiltration of irrigation water saturated with fertilizing chemicals. Therefore, irrigation wells revealed that suffering from nitrate contamination caused an increase of the chance of nitrate pollution. In addition, contour maps present a sudden increase in the total dissolved salts (TDS) in the northeastern part coincident with the highest of secondary ions of NO3 content, indicating the infiltration of irrigation water which is responsible partially for the groundwater degradation. Hydrogeochemical facie is NaCl type and enrichment of Na+ and Cl- can be attributed to urban untreated wastewaters and high rate of evapotranspiration. The concentrations of heavy elements such as Zn, Pb, Cu, Cd, Ni and Cr were low and within the WHO ranges.

Benefits of a ball and chain: simple environmental enrichments improve welfare and reproductive success in farmed American mink (Neovison vison).

Can simple enrichments enhance caged mink welfare? Pilot data from 756 sub-adults spanning three colour-types (strains) identified potentially practical enrichments, and suggested beneficial effects on temperament and fur-chewing. Our main experiment started with 2032 Black mink on three farms: from each of 508 families, one juvenile male-female pair was enriched (E) with two balls and a hanging plastic chain or length of hose, while a second pair was left as a non-enriched (NE) control. At 8 months, more than half the subjects were killed for pelts, and 302 new females were recruited (half enriched: ‘late E’). Several signs of improved welfare or productivity emerged. Access to enrichment increased play in juveniles. E mink were calmer (less aggressive in temperament tests; quieter when handled; less fearful, if male), and less likely to fur-chew, although other stereotypic behaviours were not reduced. On one farm, E females had lower cortisol (inferred from faecal metabolites). E males tended to copulate for longer. E females also weaned more offspring: about 10% more juveniles per E female, primarily caused by reduced rates of barrenness (‘late E’ females also giving birth to bigger litters on one farm), effects that our data cautiously suggest were partly mediated by reduced inactivity and changes in temperament. Pelt quality seemed unaffected, but E animals had cleaner cages. In a subsidiary side-study using 368 mink of a second colour-type (‘Demis’), similar temperament effects emerged, and while E did not reduce fur-chewing or improve reproductive success in this colour-type, E animals were judged to have better pelts. Overall, simple enrichments were thus beneficial. These findings should encourage welfare improvements on fur farms (which house 60-70 million mink p.a.) and in breeding centres where endangered mustelids (e.g. black-footed ferrets) often reproduce poorly. They should also stimulate future research into more effective practical enrichments.

The impact of hydrogeochemical processes on karst groundwater quality in arid and semiarid area: a case study in the Liulin spring area, north China

Karst groundwater is the major source of water supply for economic development and drinking water in Liulin spring area, north China. Thus, karst groundwater quality and its variation have aroused wide public concern. The primary hydrogeochemical processes that dominate karst groundwater quality, including dissolution of carbonate rocks and evaporite, mixing, and dedolomitization, are analyzed by hydrogeochemical method in combination with multivariate statistical theory and computer simulation technology. The results show that the redox state of groundwater environment transforms gradually from oxidation state to reducing state with increasing temperature and total dissolved solids (TDS) and decreasing pH value along flow path. The hydrogeochemical types of groundwater range from HCO3-Ca·Mg to Cl·SO4-Na. The Ca2+, Mg2+, and HCO3 − in karst groundwater mainly originate from dissolution of calcite and dolomite. Dissolution of calcite occurs in infiltration of rainfall into soils and unsaturated zones and then reaches to saturation before arriving groundwater level. Though saturation index of dolomite (SID) is greater than 0 in most of the samples, dolomite still dissolves along flow path due to the dedolomitization. The SO4 2− derives basically from the dissolution of gypsum rather than oxidation of pyrite. The dissolution of gypsum causes dedolomitization that increases the concentrations of Ca2+, Mg2+, and SO4 2− while the concentration of HCO3 − has smaller changes. The concentrations of Na+ and Cl− are mainly controlled by dissolution of halite. The enrichment of Na+ relative to Cl− in most samples may result from leakage of surface water enriched Na+ and dissolution of mirabilte fragments.

Straddling the tholeiitic/calc-alkaline transition: the effects of modest amounts of water on magmatic differentiation at Newberry Volcano, Oregon

Melting experiments have been performed at 1 bar (anhydrous) and 1- and 2-kbar H2O-saturated conditions to study the effect of water on the differentiation of a basaltic andesite. The starting material was a mafic pumice from the compositionally zoned tuff deposited during the ~75 ka caldera-forming eruption of Newberry Volcano, a rear-arc volcanic center in the central Oregon Cascades. Pumices in the tuff of Newberry caldera (TNC) span a continuous silica range from 53 to 74 wt% and feature an unusually high-Na2O content of 6.5 wt% at 67 wt% SiO2. This wide range of magmatic compositions erupted in a single event makes the TNC an excellent natural laboratory in which to study the conditions of magmatic differentiation. Our experimental results and mineral–melt hygrometers/thermometers yield similar estimates of pre-eruptive H2O contents and temperatures of the TNC liquids. The most primitive (mafic) basaltic andesites record a pre-eruptive H2O content of 1.5 wt% and a liquidus temperature of 1,060–1,070 °C at upper crustal pressure. This modest H2O content produces a distinctive fractionation trend that is much more enriched in Na, Fe, and Ti than the calc-alkaline trend typical of wetter arc magmas, but slightly less enriched in Fe and Ti than the tholeiitic trend of dry magmas. Modest H2O contents might be expected at Newberry Volcano given its location in the Cascade rear arc, and the same fractionation trend is also observed in the rim andesites of the rear-arc Medicine Lake volcano in the southern Cascades. However, the Na–Fe–Ti enrichment characteristic of modest H2O (1–2 wt%) is also observed to the west of Newberry in magmas erupted from the arc axis, such as the Shevlin Park Tuff and several lava flows from the Three Sisters. This shows that modest-H2O magmas are being generated directly beneath the arc axis as well as in the rear arc. Because liquid lines of descent are particularly sensitive to water content in the range of 0–3 wt% H2O, they provide a quantitative and reliable tool for precisely determining pre-eruptive H2O content using major-element data from pumices or lava flows. Coupled enrichment in Na, Fe, and Ti relative to the calc-alkaline trend is a general feature of fractional crystallization in the presence of modest amounts of H2O, which may be used to look for “damp” fractionation sequences elsewhere.

Zircon U–Pb geochronology, geochemistry, and Sr–Nd–Hf isotopes of granitoids in the Yulekenhalasu copper ore district, northern Junggar, China: Petrogenesis and tectonic implications

The Yulekenhalasu porphyry copper deposit is located in the Kalaxiange'er metallogenic belt in northern Junggar, China. We present the results from zircon U–Pb geochronology, and geochemical and Sr–Nd–Hf isotope analyses of the granitoids associated with the ore deposits with a view to constrain their petrogenesis and tectonic setting. The granitoids consist of quartz diorite, diorite porphyry, porphyritic monzonite, and quartz porphyry, emplaced at 382, 379, 375–374, and 348Ma, respectively, which span Late Devonian to early Carboniferous ages. The ore-bearing intrusion is mainly diorite porphyry, with subordinate porphyritic monzonite. The Late Devonian intrusions are characterized by SiO2 contents of 54.5–64.79wt.%, Na2O contents of 3.82–8.24wt.%, enrichment in Na, light rare-earth elements (LREEs), and large ion lithophile elements. They also display relative depletion in Y, Ba, P, Nb, Ta, and Ti, and weak negative Eu anomalies (δEu=0.6–0.87). The early Carboniferous quartz porphyry is characterized by high SiO2 content (72.26–73.35wt.%), enrichment in LREEs, K, and Sr, and relative depletion in Y (10.82–12.52ppm) and Yb (1.06–1.15ppm). The Late Devonian and early Carboniferous granitoids are characterized by positive εNd(t) values (5.2–10.1, one sample at −1.9), positive εHf(t) values (7.46–18.45), low (87Sr/86Sr)i values (0.70363–0.70476), and young crustal residence ages. These data indicate that the sources of the granitoids were mainly mantle-derived juvenile rocks. Geochemical and Nd–Sr–Hf isotopic data demonstrate that the Late Devonian granitoids formed in an oceanic island arc, and they were formed from different sources, among which the mineralized diorite porphyry might have originated from a mixed slab-derived and mantle wedge melt source. The early Carboniferous quartz porphyry was likely emplaced in a mature island arc environment, and was probably derived from juvenile crust.

Environmental Enrichment Reduces Signs of Boredom in Caged Mink

Animals housed in impoverished cages are often labelled ‘bored’. They have also been called ‘apathetic’ or ‘depressed’, particularly when profoundly inactive. However, these terms are rarely operationally defined and validated. As a negative state caused by under-stimulation, boredom should increase interest in stimuli of all kinds. Apathy (lack of interest), by contrast, should manifest as decreased interest in all stimuli, while anhedonia (loss of pleasure, a depressive symptom) should specifically decrease interest in normally rewarding stimuli. We tested the hypotheses that mink, a model carnivore, experience more boredom, depression-like apathy, or anhedonia in non-enriched (NE) cages than in complex, enriched (E) cages. We exposed 29 subjects (13 E, 16 NE) to ten stimuli categorized a priori as aversive (e.g. air puffs), rewarding (e.g. evoking chasing) or ambiguous/neutral (e.g. candles). Interest in stimuli was assessed via latencies to contact, contact durations, and durations oriented to stimuli. NE mink contacted all stimuli faster (P = 0.003) than E mink, and spent longer oriented to/in contact with them, albeit only significantly so for ambiguous ones (treatment*type P<0.013). With stimulus category removed from statistical models, interest in all stimuli was consistently higher among NE mink (P<0.0001 for all measures). NE mink also consumed more food rewards (P = 0.037). Finally, we investigated whether lying down while awake and stereotypic behaviour (both increased by NE housing) predicted these responses. Lying awake positively co-varied with certain measures of increased exploration. In contrast, stereotypic ‘scrabbling’ or locomotion (e.g. pacing) did not. Overall, NE mink showed no evidence of apathy or depression, but instead a heightened investigation of diverse stimuli consistent with boredom. This state was potentially indicated by spending much time lying still but awake (although this result requires replication). Boredom can thus be operationalized and assessed empirically in non-human animals. It can also be reduced by environmental enrichment.

National scale evaluation of groundwater chemistry in Korea coastal aquifers: evidences of seawater intrusion

Pollution of groundwater by seawater intrusion poses a threat to sustainable agriculture in the coastal areas of Korea. Therefore, seawater intrusion monitoring stations were installed in eastern, western, and southern coastal areas and have been operated since 1998. In this study, groundwater chemistry data obtained from the seawater intrusion monitoring stations during the period from 2007 to 2009 were analyzed and evaluated. Groundwater was classified into fresh ( 3,000 μS/cm) according to EC levels. Among groundwater samples (n = 233), 56, 7, and 37% were classified as the fresh, brackish, and saline, respectively. The major dissolved components of the brackish and saline groundwaters were enriched compared with those of the fresh groundwater. The enrichment of Na+ and Cl− was especially noticeable due to seawater intrusion. Thus, the brackish and saline groundwaters were classified as Ca–Cl and Na–Cl types, while the fresh groundwater was classified as Na–HCO3 and Ca–HCO3 types. The groundwater included in the Na–Cl types indicated the effects of seawater mixing. Ca2+, Mg2+, Na+, K+, SO42−, and Br− showed good correlations with Cl− of over r = 0.624. Of these components, the strong correlations of Mg2+, SO42−, and Br− with Cl− (r ≥ 0.823) indicated a distinct mixing between fresh groundwater and seawater. The Ca/Cl and HCO3/Cl ratios of the groundwaters gradually decreased and approached those of seawater. The Mg/Cl, Na/Cl, K/Cl, SO4/Cl, and Br/Cl ratios of the groundwaters gradually decreased, and were similar to or lower than those of seawater, indicating that Mg2+, Na+, K+, SO42−, and Br−, as well as Cl− in the saline groundwater can be enriched by seawater mixing, while Ca2+ and HCO3− are mainly released by weathering processes. The influence of seawater intrusion was evaluated using threshold values of Cl− and Br−, which were estimated as 80.5 and 0.54 mg/L, respectively. According to these criteria, 41–50% of the groundwaters were affected by seawater mixing.

Improved Lateral Discrimination in Screening the Elemental Composition of Buckwheat Grain by Micro-PIXE

The elemental composition of specific fractions of cereal and pseudocereal grains can be roughly estimated after milling. Alternatively, the elemental localization of cross-sectioned grains can be quantitatively analyzed by microproton induced X-ray emission (micro-PIXE), taking advantage of high elemental sensitivity and low lateral resolution. We present a micro-PIXE study on buckwheat (Fagopyrum esculentum) grain, with a detailed description of the elemental distributions. Elements such as Mg, P, S, K, Fe, Ni, Cu, and Zn were preferentially localized in the cotyledons and embryonic axis; however, significant amounts of K and Fe were also found in the pericarp. The aleurone layer covering the cotyledons was especially enriched in S and P, while testa, a thin layer above the aleurone did not show any significant element enrichments. The highest concentrations of Al, Si, Cl, Ca, and Ti were found in the pericarp. A detailed element localization study of pericarp layers revealed that the inner layer was enriched in K, Mn, Ca, and Fe, while the outer layer showed enrichments in Na, Mg, P, S, and Al. On the basis of the data obtained, milling techniques can be adapted to obtain milling fractions with targeted nutritional values.

Trace-element study and uranium-lead dating of perovskite from the Afrikanda plutonic complex, Kola Peninsula (Russia) using LA-ICP-MS

The U-Pb geochronology of perovskite is a powerful tool in constraining the emplacement age of silica-undersaturated rocks. The trace-element and U-Pb isotopic compositions of perovskite from clinopyroxenite and silicocarbonatite from the Afrikanda plutonic complex (Kola, Russia) were determined by laser-ablation inductively-coupled mass-spectrometry (LA-ICP-MS). In addition, the Sr isotopic composition of perovskite was measured by isotope-dilution mass-spectrometry to better constrain the relations between its host rocks. Perovskite from the two rock types shows a different degree of enrichment in Na, Mg, Mn, Pb, Fe, Al, V, rare-earth elements, Zr, Hf, Th, U and Ta. The perovskite 87Sr/86Sr values are within analytical uncertainty of one another and fall within the range of mantle values. The 206Pb/238U ages (corrected for common lead using 207Pb-method) of perovskite from silicocarbonatite statistically yield a single population with a weighted mean of 371 ± 8 Ma (2σ; MSWD = 0.071). This age is indistinguishable, within uncertainty, to the clinopyroxenite weighted mean 206Pb/238U age of 374 ± 10 Ma (2σ; MSWD = 0.18). Our data are in good agreement with the previous geochronological study of the Afrikanda complex. The observed variations in trace-element composition of perovskite from silicocarbonatite and clinopyroxenite indicate that these rocks are not related by crystal fractionation. The Sr isotopic ratios and the fact that the two rocks are coeval suggest that they were either produced from a single parental melt by liquid immiscibility, or from two separate magmas derived at different degrees of partial melting from an isotopically equilibrated, but modally complex mantle source.

Regional mapping of pre-metamorphic spilitization and associated chemical mobility in greenschist-facies metabasalts of the SW Scottish Highlands

Abstract: Both spilitic and non-spilitic metabasaltic sills are hosted by greenschist-facies metasediments in the SW Scottish Highlands. Spilitization is mainly characterized by enrichment in Na 2 O, elevated modal plagioclase and epidote segregations. Mapping of the spatial distribution of spilitic metabasalts reveals an ancient sub-sea-floor fluid cell centred on the extrusive Tayvallich Volcanics. Fluid circulation was most extensive at shallow levels where most sills were spilitized. We attribute this to pervasive flow of saline fluid, which was thermally driven by the cooling suite of lava flows and sills. Spilitization below this lithostratigraphic depth was restricted to only a few sills. Their spilitization is largely unrelated to specific properties of these sills (e.g. width, chemistry or host lithology). We conclude that fluid channelling was an intrinsic property of sub-sea-floor fluid flow either at deeper levels or earlier during fluid circulation. By profiling of the size distributions of relic phenocrysts in a partly spilitized sill, we conclude that spilitization proceeds with the symmetric propagation of a spilitization front from the sill margins towards the sill interior. Based on chemical profiling across the margin of an epidote segregation, we conclude that spilitization is associated with chemical transport on scales ranging from 0.1 to 10 m.

GEOLOGY AND CHEMICAL VARIATIONS IN TOURMALINE FROM THE QUARTZ-TOURMALINE BRECCIAS WITHIN THE KERKENEZ GRANITE-MONZONITE MASSIF, CENTRAL ANATOLIAN CRYSTALLINE COMPLEX, TURKEY

A hydrothermal breccia zone 6 km long and 2 km wide, crossed by quartz–tourmaline veins, occurs to the south of the Late Cretaceous Kerkenez granite–monzonite massif in the northern part of the Central Anatolian Crystalline Complex, Yozgat, Turkey. This breccia zone is characterized by numerous veins, a few millimeters to 1 meter in width, and display typical micro-tectonic features of multiple brecciation. Trace amounts of albite, K-feldspar, epidote, muscovite and rutile are associated with quartz and tourmaline. Petrographic features indicate three successive stages of tourmaline generation. The first generation is represented by feruvite, and the second and third generations consist of schorl. These distinct generations of tourmaline show successive enrichment in Al and Na, and depletion in Ti and Ca. The Na/(Na + Ca) values vary in the range 0.41–0.49 in the first generation, and 0.53–0.86 and 0.91–0.99 in the second and third generations. The development of the breccia zone and formation of three successive generations of tourmaline are most probably related to fluid-assisted brecciation and infiltration of low- to medium-pH hydrothermal fluids under subsolidus conditions. Successive enrichment in Na and Al in the younger generations is ascribed to late-stage fractionation in the B-rich granitic source.

Effect of annealing upon the structure and adhesion properties of sputtered bio-glass/titanium coatings

Bio-glass films were deposited by radio-frequency magnetron sputtering technique onto medical grade Ti6Al7Nb alloy substrates from prepared silica based bio-glass target. A low deposition temperature was used (150 °C) and three different working pressures, followed by annealing in air at 550 and 750 °C. A quasi-stoichiometric target to substrate atomic transfer was found for Si, Ca and P, along with strong enrichment in Na and depletion in K and Mg, as evidenced by the energy dispersive microanalysis. The best results, taking into account stoichiometry and surface roughness, were obtained for the BG layers deposited at 0.3 Pa argon working pressure. The infrared spectroscopy of the as-sputtered and of the annealed films evidenced the characteristic molecular vibrations of silicate, phosphate and carbonate functional groups. The as-deposited films are amorphous and became partly crystalline after annealing at 750 °C, as evidenced by X-ray diffraction. The pull-out measurements, performed with a certified pull-test machine, gave very strong film–substrate adhesion strength values. For the non-crystalline layers, the pull-out strength is higher than 85 MPa, and decreases after annealing at 750 °C to 72.9 ± 7.1 MPa. The main objective of this work was to establish the influence of the working pressure upon the composition and morphology of the as-deposited films, and of the annealing temperature upon structure and film–substrate adhesion.

Glasses in coarse-grained micrometeorites

Micrometeorites (MMs, interplanetary dust particles with 25 – 500 μm diameters) carry the main mass of extraterrestrial matter that is captured by Earth. The coarse-grained MMs mainly consist of olivine aggregates, which - as their counterparts in CC chondrites - also contain pyroxenes and glass. We studied clear glasses in four coarse-grained crystalline MMs (10M12, M92-6b, AM9, and Mc7-10), which were collected from the ice at Cap Prudhomme, Antarctica. Previous studies of glasses (e.g., glass inclusions trapped in olivine and clear mesostasis glass) in carbonaceous and ordinary chondrites showed that these phases could keep memory of the physical-chemical conditions to which extraterrestrial matter was exposed. Here we compare the chemical compositions of MM glasses and glasses from CM chondrites with that in experimentally heated objects from the Allende CV chondrite and with glasses from cometary particles. Our results show that MMs were heated to variable degrees (during entry through the terrestrial atmosphere), which caused a range from very little chemical modification of the glass to total melting of the precursor object. Such modifications include dissolution of minerals in the melted glass precursor and some loss of volatile alkali elements. The chemical composition of all precursor glasses in the MMs investigated is not primitive such as glasses in CM and CR chondrite objects. It shows signs of pre-terrestrial chemical modification, e.g., metasomatic enrichments in Na and Fe 2+ presumably in the solar nebula. Glasses of MMs heated to very low degree have a chemical composition indistinguishable from that of glasses in comet Wild 2 particles; giving additional evidence that interplanetary dust (e.g., Antarctic MMs) possibly represents samples from comets.

Major and trace element composition of chromian diopsides from the Zagadochnaya kimberlite (Yakutia, Russia): Metasomatic processes, thermobarometry and diamond potential

The major and trace element composition of chromian diopsides and associate minerals from concentrates of the diamond-free Zagadochnaya kimberlite have been studied to gain an insight into the lithological variability of the underlying mantle and explore the possible reasons for the different diamond potential of contiguous portions of the Yakutian lithosphere. A few (Al, Cr, Na)-poor chromian diopsides ( group I) have a megacrystic signature and are interpreted as spinel-facies magmatic segregates from melts related to the host kimberlite. Other (Al, Cr, Na)-rich chromian diopsides ( groups II and III) originated from variously metasomatized garnet peridotites and, possibly, pyroxenites from relatively shallow mantle depths (< 130–160 km). Two main metasomatic stages are distinguished, which led to strong enrichments in LILE and LREE. The metasomatic processes recorded by group II diopsides are broadly similar to those shown by garnet peridotite xenoliths from the nearby, highly diamondiferous Udachnaya kimberlite. Group III diopsides document a peculiar, subsequent modification after reaction with ultra-alkaline melts, which led to variable enrichments in Na, Al, Cr and Fe and was probably related to the magmatic stage connected with the eruption of the host kimberlite. It is suggested that the barren nature of the Zagadochnaya kimberlite is primarily a consequence of the relatively shallow depth of mantle sampling. Extensive melt–peridotite interaction at shallow levels may have played a significant role in controlling the high-Mg, low-Ti composition of this kimberlite.

Fluoride, nitrate and water hardness in groundwater supplied to the rural communities of Ensenada County, Baja California, Mexico

The hydrogeochemistry of 26 wells belonging to ten different aquifers in the county of Ensenada, Baja California, is studied. These wells are all used to supply the rural communities in the region, which comprise ~37,000 inhabitants, excluding the city of Ensenada. High total dissolved solids (TDS) concentrations (maximum 7.35 g l−1) indicate that salt is a ubiquitous contaminant in the aquifers due to seawater intrusion. The aquifers that support extensive agriculture activities (Maneadero, San Quintin, San Simon and El Rosario) are characterized by higher N–NO3 concentrations (maximum 20 mg l−1) derived from fertilizers. Fluoride concentrations exceed the 1.5 mg l−1 Mexican official limit in only four wells. The enrichments of F− in the southern aquifers are thought to be associated to water–rock interactions controlled mainly by Na–Ca equilibrium reactions with fluorite, as suggested from high dissolved Na concentrations in these waters. In the northern aquifer of Maneadero, no enrichment of Na is found and a geothermal source for F− is likely. Water is hard to moderately hard, with Ca/Mg ratios >1. Although drinking water directly from the tap is not a common practice in these localities, most sources have concentrations of major ions and TDS that exceed the Mexican official limits.

Permian volcanisms in eastern and southeastern margins of the Jiamusi Massif, northeastern China: zircon U-Pb chronology, geochemistry and its tectonic implications

LA-ICP-MS zircon U-Pb dating and geochemical data for the Late Paleozoic volcanic rocks from eastern and southeastern margins of the Jiamusi Massif are presented to understand the regional tectonic evolution. Zircons from eight representative volcanic rocks are euhedral-subhedral in shape and display striped absorption and fine-scale oscillatory growth zoning as well as high Th/U ratios (0.33–2.37), implying a magmatic origin. The dating results show that the Late Paleozoic volcanic rocks in the study area can be divided into two stages, i.e., the Early Permian (a weighted mean 206Pb/238U age of 288 Ma) and the Middle Permian volcanisms (a weighted mean 206Pb/238U age of 268 Ma). The former is composed mainly of basalt, basaltic-andesite, andesite and minor dacite. They are characterized by low SiO2 contents, high Mg# (0.40–0.59), enrichment in Na (Na2O/K2O = 1.26–4.25) and light rare earth elements (LREEs), relative depletion in heavy rare earth elements (HREEs) and high field strength elements (HFSEs), indicating that an active continental margin setting could exist in the eastern margin of the Jiamusi Massif in the Early Permian. The latter consists mainly of rhyolite and minor dacite with high SiO2 (77.23%–77.52%), low MgO (0.11%–0.14%), enrichment in K2O (Na2O/K2O ratios < 0.80) and Rb, Th, U and depletion in Eu, Sr, P and Ti, implying a crust-derived origin. Therefore, it is proposed that the Middle Permian volcanic rocks could have formed under the collision of the Jiamusi and the Khanka Massifs.

Petrogenesis of Shangyu gabbro-diorites in western Shandong: Geochronological and geochemical evidence

Chronology and geochemistry of the Shangyu gabbro-diorite in western Shandong were studied to understand their petrogenesis and the nature of the Mesozoic lithospheric mantle. The Shangyu intrusion is mainly composed of a suite of gabbro-diorite. Zircons from the intrusion display euhedral-subhedral in shape and have high Th/U ratios (1.23–2.87), implying their magmatic origin. LA-ICP-MS zircon U-Pb dating results for two samples indicate that they were formed in the Early Cretaceous, yielding weighted mean 206Pb/238U ages of 129±1Ma and 134±2Ma, respectively. Except for early cumulate such as sample QT-19, their SiO2 and MgO contents range from 50.12% to 56.37% and from 3.52% to 6.37%, respectively. Moreover, the gabbro-diorites are characterized by high Mg (0.54–0.63), enrichment in Na (Na2O/K2O ratios more than 1), Cr (73×10−6−217×10−6) and Ni (34×10−6−241×10−6), and intensive enrichments in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depletion in high field strength elements (HFSEs). Their initial 87Sr/86Sr ratios and ɛ Nd(t) values range from 0.70962 to 0.71081 and from −16.60 to −13.04, respectively. Taken together with the Early Cretaceous high-Mg diorites and the mantle xenoliths from the Tietonggou and Jinling as well as basalts from the Fangcheng and Feixian, it is suggested that the primary magma for the Shangyu gabbro-diorites should be derived from the enriched lithospheric mantle intensively modified by continental crust. The Sr-Nd-Pb isotopic compositions for the Early Cretaceous high-Mg diorites in western Shandong display a trend of spatial variations, i.e., initial 87Sr/86Sr, 207Pb/204Pb and 208Pb/204Pb ratios decreasing and ɛ Nd(t) values increasing from southeast to northwest in western Shandong, which is consistent with the tectonic model that the Yangtze Craton subducted beneath the North China Craton oriented in north-west direction in the Early Mesozoic.

Hydrogeochemistry of the Sarada river basin, Visakhapatnam district, Andhra Pradesh, India

Systematic hydrogeochemical survey has been carried out for understanding the sources of dissolved ions in the groundwaters of the area occupied by Sarada river basin, Visakhapatnam district, Andhra Pradesh, India. Khondalites, charnockites and granite gneisses and calc-granulites of Precambrians and alluvial deposits of Quaternaries underlie the study area. Groundwaters are both fresh and brackish; the latter waters being a dominant. Most groundwaters are characterized by Na+:HCO 3 − facies due to chemical weathering of the rocks. Enrichment of Na+, K+, Cl−, SO 4 2− , NO 3 − and F− in some groundwater samples is caused by seawater intrusion, locally accompanied by ion-exchange, and anthropogenic activities, resulting in an increase of brackish in the groundwaters. Based on the results of this hydrogeochemical study, suitable management measures are recommended to solve the water quality problems.