Heavy rare earth elements (HREE) are dominantly mined from the weathering crusts of granites in South China. Although weathering processes occur globally, no economic HREE resources of this type have ...yet been found outside China. Here, we report the occurrence of unidentified REE minerals in the granites from South Chinese deposits. They contain high levels of both HREE and light REE, but are strongly depleted in Ce, implying high oxidation state. These REE minerals show higher initial Nd isotope than primary REE-rich minerals (ɛNd(t)=0.9±0.8 versus -11.5±0.5). The mineralized weathering crusts inherited REE signature of the granites, but show more Ce depletion and more overall concentration of the REE. We propose, therefore, that highly oxidized, REE-rich fluids, derived from external, isotopically depleted sources, metasomatized the granites, which resulted in Ce depletion as Ce
and enrichment of the remaining REE, especially the HREE, contributing to formation of a globally important REE resource.
Rare-earth deposits associated with intrusive carbonatite complexes are the world’s most important source of these elements (REE). One of the largest deposits of this type is Maoniuping in the ...Mianning-Dechang metallogenic belt of eastern Tibet (Sichuan, China). In the currently mined central part of the deposit (Dagudao section), REE mineralization is hosted by a structurally and mineralogically complex Late Oligocene (26.4 ± 1.2 Ma,
40
Ar/
39
Ar age of fluorphlogopite associated with bastnäsite) hydrothermal vein system developed in a coeval syenite intrusion. Low-grade stockworks of multiple veinlets and breccias in the lower part of the orebody grade upwards into progressively thicker veins (up to 12 m in width) that are typically zoned and comprise ferromagnesian micas (biotite to fluorphlogopite), sodium clinopyroxenes (aegirine to aegirine-augite), sodium amphiboles (magnesio-arfvedsonite to fluororichterite), K-feldspar, fluorite, barite, calcite, and bastnäsite. The latter four minerals are most common in the uppermost 80 m of the Dagudao section and represent the climax of hydrothermal activity. Systematic variations in the fluid inclusion data indicate a continuous hydrothermal evolution from about 230–400 °C (fluid inclusions in feldspar, clinopyroxene, and amphibole) to 140–240 °C (fluid inclusions in bastnäsite, fluorite, calcite). Hydrothermal REE transport was probably controlled by F
−
, (SO
4
)
2−
, Cl
−
, and (CO
3
)
2−
as complexing ligands. We propose that at Dagudao, silicate magmas produced orthomagmatic fluids that explored and expanded a fissure system generated by strike-slip faulting. Initially, the fluids had appreciable capacity to transport REE and, consequently, no major mineralization developed. The earliest minerals to precipitate were alkali- and Fe-rich silicates containing low levels of F, which caused progressive enrichment of the fluid in Ca, Mg, F, Cl, REE, (SO
4
)
2−
, and (CO
3
)
2−
, leading to the crystallization of aegirine-augite, fluororichterite, fluorphlogopite, fluorite, barite, calcite, and bastnäsite gradually. Barite, fluorite, calcite, and bastnäsite are the most common minerals in typical ores, and bastnäsite generally postdates these gangue minerals. Thus, it is very probable that fluid cooling and formation of large amount of fluorite, barite, and calcite triggered bastnäsite precipitation in the waning stage of hydrothermal activity.
Apatite-group phosphates are nearly ubiquitous in carbonatites, but our understanding of these minerals is inadequate, particularly in the areas of element partitioning and petrogenetic ...interpretation of their compositional variation among spatially associated rocks and within individual crystals. In the present work, the mode of occurrence, and major- and trace-element chemistry of apatite (sensu lato) from calcite and dolomite carbonatites, their associated cumulate rocks (including phoscorites) and hydrothermal parageneses were studied using a set of 80 samples from 50 localities worldwide. The majority of this set represents material for which no analytical data are available in the literature. Electron-microprobe and laser-ablation mass-spectrometry data (~600 and 400 analyses, respectively), accompanied by back-scattered-electron and cathodoluminescence images and Raman spectra, were used to identify the key compositional characteristics and zoning patterns of carbonatitic apatite. These data are placed in the context of phosphorus geochemistry in carbonatitic systems and carbonatite evolution, and compared to the models proposed by previous workers. The documented variations in apatite morphology and zoning represent a detailed record of a wide range of evolutionary processes, both magmatic and fluid-driven. The majority of igneous apatite from the examined rocks is Cl-poor fluorapatite or F-rich hydroxylapatite (≥0.3apfu F) with 0.2–2.7wt.% SrO, 0–4.5wt.% LREE2O3, 0–0.8wt.% Na2O, and low levels of other cations accommodated in the Ca site (up to 1000ppm Mn, 2300ppm Fe, 200ppm Ba, 150ppm Pb, 700ppm Th and 150ppm U), none of which show meaningful correlation with the host-rock type. Silicate, (SO4)2− and (VO4)3− anions, substituting for (PO4)3−, tend to occur in greater abundance in crystals from calcite carbonatites (up to 4.2wt.% SiO2, 1.5wt.% SO3 and 660ppm V). Although (CO3)2− groups are very likely present in some samples, Raman micro-spectroscopy proved inconclusive for apatites with small P-site deficiencies and other substituent elements in this site. Indicator REE ratios sensitive to redox conditions (δCe, δEu) and hydrothermal overprint (δY) form a fairly tight cluster of values (0.8–1.3, 0.8–1.1 and 0.6–0.9, respectively) and may be used in combination with trace-element abundances for the development of geochemical exploration tools. Hydrothermal apatite forms in carbonatites as the product of replacement of primary apatite, or is deposited in fractures and interstices as euhedral crystals and aggregates associated with typical late-stage minerals (e.g., quartz and chlorite). Hydrothermal apatite is typically depleted in Sr, REE, Mn and Th, but enriched in F (up to 4.8wt.%) relative to its igneous precursor, and also differs from the latter in at least some of key REE ratios e.g., shows (La/Yb)cn≤25, or a negative Ce anomaly. The only significant exception is Sr(± REE,Na)-rich replacement zones and overgrowths on igneous apatite from some dolomite(-bearing) carbonatites. Their crystallization conditions and source fluid appear to be very different from the more common Sr-REE-depleted variety. Based on the new evidence presented in this work, trace-element partitioning between apatite and carbonatitic magmas, phosphate solubility in these magmas, and compositional variation of apatite-group minerals from spatially associated carbonatitic rocks are critically re-evaluated.
•Hydrothermal and igneous apatites in carbonatites are compositionally distinct.•Trace-element ratios in carbonatitic apatite can be used to develop geochemical exploration tools.•REE is compatible with respect to apatite and follows two-site partitioning.•Compositional variation and zoning of carbonatitic apatite are a sensitive record of its history.
Urban soils pollution by trace elements arouses the growing interest in China. The aim of this study was to assess urban soil pollution by As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in China and the possible ...impacts on urban inhabitants and urban green spaces (UGS). Data from more than 17,000 samples were applied to characterize the status of 101 cities. The pollution assessment proved that 11% of the cities are heavily polluted. According to the Hazard Index, the value of risk for the infant population in 15 cities exceed the standardly accepted tolerable levels. The carcinogenic risk assessment demonstrated the potential threat in the cities with the total population approximately 20,566,900. Cr and As were detected to be the most hazardous elements. UGS may be seriously threatened by trace elements toxicity in 38 cities. Cd was found to be the riskiest element for UGS. Ecosystem services of UGS can be significantly disrupted under the current situation in China and their status is expected to deteriorate in the future. For this reason, it is essential to alter the policy of the urbanization process and develop functional concepts of urban green infrastructures adapted to the high level of contamination which shall improve human well-being in China.
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•Data from more than 17,000 samples representing 101 cities in China were processed.•Eleven cities are heavily polluted and most common contaminants are Cd and Hg.•The main factor affecting pollution is industry, not urban population size.•There are approximately 38,897,500 inhabitants living in heavily polluted cities.•Ecosystem services of urban green spaces can be significantly disrupted in 38 cities.
The term “Glomalin” was originally used to describe a hypothetical gene product of arbuscular mycorrhizal fungi (AMF) that was assumed to be a nearly ubiquitous, thermostable and highly recalcitrant ...glycoprotein, deposited in soils in large amounts, and deemed to indicate soil health and quality. It was defined operationally as the fraction of soil organic matter (SOM) extractable by a hot citrate buffer and assessed either by Bradford assay or by cross-reactivity with monoclonal antibody MAb32B11. Later, it was recognized that the extracts contained a variety of compounds, including some of non-AMF origin, cross-reactive with both Bradford assay and the monoclonal antibody. This led to re-describing the pertinent (and still only operationally defined) SOM as “glomalin-related soil proteins (GRSP)”, albeit without any substantial change in the underlying concepts. Consequently, a great deal of confusion in this area arose among researchers in soil, plant, and environmental sciences. Glomalin or GRSP (often used interchangeably) has previously been linked to various soil features, including stability of soil aggregates, size of soil C and N pools, sequestration of heavy metals, and alleviation of various plant stresses. GRSP concentrations in soil often, but not always, have been correlated with AMF biomass measured by alternative (mainly microscopic) approaches. GRSP formation, deposition, and/or decomposition in soils seem to be largely dependent on a multitude of interactions among plants, AMF, and other soil microorganisms, including prokaryotes. The chemical structure of GRSP extracted from soil remains unclear and generally complex. That is due to the unspecific mode of its extraction and purification, as well as the great variety of analytical approaches that have been used heretofore to assess it. Future research needs to elucidate the exact composition of this operationally defined SOM fraction, the controls over its production and accumulation in soils, and its exact role in soil ecology generally and soil food webs in particular. Furthermore, novel and independent tools should be established to more specifically (as compared to current glomalin assays) assess AMF biomass and functioning in roots and soil and its involvement in soil processes.
•Glomalin is a hypothetical gene product of arbuscular mycorrhizal fungi (AMF).•It has been heralded as a suitable proxy for AMF abundance, activity and legacy.•In the past, glomalin has been defined operationally as a specific SOM fraction.•As such, glomalin contains materials produced by different processes and organisms.•Proxies with higher specificity than glomalin may thus be required in the future.
Zircon from four plutons of peralkaline granites and quartz-bearing syenites, differing in geotectonic positions, petrological and mineralogical compositions, and contents of volatile and trace ...elements, was studied using SEM, CL, and EPMA with the intention to define typical textural and chemical features of zircon from peralkaline rocks. In strongly peralkaline Na-pyroxene-bearing rocks represented by the Khan Bogd and Khalzan Buregte plutons (Mongolia), the primary zircon is scarce or missing. Most zircon grains are secondary, originating in hydrothermal stage from primary Zr silicates. They often form globular or radial aggregates. Chemical compositions of zircon in these rocks typically show high contents of Y, moderate contents of REE (thus high Y/Yb values) together with low contents of U and Th and low analytical totals. In mildly peralkaline mica-bearing rocks represented by Ivigtut stock (Groenland) and Madeira pluton (Brazil), the exclusive primary Zr mineral is zircon, mostly of orthomagmatic origin. Its analytical totals approach 100 wt%, enrichment in HREE, resulting in low Y/Yb values, is typical. Zircon populations from two types of peralkaline granitoids can be distinguished from each other and from zircon from S-type granites based on combination of the Zr/Hf, Y/Yb, and U/Th values, or on the Y-Hf-P ternary diagram.
As Mongolia is considered one of the most resource extraction-dependent countries globally, significant mining-related environmental and human health risks are expected. The aim of this study was to ...(I) assess the impacts of mining on soil pollution with metals in Mongolia's key coal mining towns (Baganuur, Nalaikh and Sharyn Gol) and (II) review the current knowledge on soil pollution with metal(loid)s and related health risks in Mongolia. The results showed predominantly low soil contents of Cd, Cu, Pb and Zn and a related absence of severe pollution and potential health risk in the coal mining towns. Urban design, rather than the presence of mines, controlled the pollution distribution. Despite the methodological shortcomings of several studies on soil pollution in Mongolia, their results suggest a similarly low threat in the three largest cities (Ulaanbaatar, Darkhan, Erdenet) and several mining areas. While the generally highlighted risk of As seems like an artificially escalated issue, the content of Cr in urban soil may be a neglected threat. Further pollution research in Mongolia should focus on street dust and drinking water pollution.
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Orogenic lamproites represent a group of peralkaline, ultrapotassic and perpotassic mantle-derived igneous rocks that hold the potential to sample components with extreme compositions ...from highly heterogeneous orogenic mantle. In our pilot study, we present highly siderophile element (HSE) and Re–Os isotope systematics of Variscan orogenic lamproites sampled in the territories of the Czech Republic, Austria and Poland, i.e., from the termination of the Moldanubian and Saxo-Thuringian zones of the Bohemian Massif. Orogenic lamproites of the Bohemian Massif are distinguished by variably high contents of SiO2, high Mg# and predominant mineral associations of K-rich amphibole and Fe-rich microcline. The HSE show (i) consistently very low contents in all investigated orogenic lamproites compared to the estimated concentrations in majority of mid-ocean ridge basalts, hotspot-related volcanic rocks (e.g., ocean island basalts, continental flood basalts, komatiites, some intraplate alkaline volcanic rocks such as kimberlites and anorogenic lamproites) and arc lavas, and (ii) marked differences in relative and absolute HSE abundances between the samples from the Moldanubian and Saxo-Thuringian Zone. Such a regional dependence in HSE from mantle-derived melts is exceptional. Orogenic lamproites have highly variable and high initial suprachondritic 187Os/188Os values (up to 0.631) compared with rather chondritic to subchondritic Os isotope values of the young lithospheric mantle below the Bohemian Massif. The highly radiogenic Os isotope component in orogenic lamproites may be derived from preferential melting of metasomatised vein assemblages sitting in depleted peridotite mantle. This process appears to be valid generally in the petrogenesis of orogenic lamproites both from the Bohemian Massif and from the Mediterranean area. As a specific feature of the orogenic lamproites from the Bohemian Massif, originally ultra-depleted mantle component correlative with remnants of the Rheic Ocean lithosphere in the Moldanubian Zone was metasomatised by a mixture of evolved and juvenile material, whereas the lithospheric mantle in the Saxo-Thuringian Zone was enriched through the subduction of evolved crustal material with highly radiogenic Sr isotope signature. As a result, this led to observed unique regionally dependent coupled HSE, Rb–Sr and Re–Os isotope systematics.
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•Addition of white-rot fungi to OFMSW influenced compost maturation.•Effectiveness of waste degradation and compost maturation depends on type of fungi.•Inoculation with T. versicolor ...and F. fomentarius led to the lowest phytotoxicity.
An investigation was carried out on the effect of inoculation methods on the compost of an organic fraction of municipal solid waste. Three types of white-rot fungi (Phanerochaete chrysosporium, Trametes versicolor and Fomes fomentarius), and a consortium of these fungi, were used. The study assessed their influence on microbial enzymatic activities and the quality of the finished compost. It was found that the addition of white-rot fungi to municipal solid waste (after 37days of composting) could be a useful strategy for enhancing the properties of the final compost product. In comparison with the control sample (compost without inoculation), it accelerates degradation of solid waste as indicated by changes in C/N, electrical conductivity and pH. However, the effectiveness of waste degradation and compost maturation depends on the type of microorganism used for inoculation. The presence of inoculants, such as Trametes versicolor and Fomes fomentarius, led to a higher degrading ratio and a better degree of maturity. This resulted in an increase of enzymatic activities (especially dehydrogenase and protease) and a germination index in comparison with inoculation using Phanerochaete chrysosporium or a consortium of fungi.
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