Rare Earth Elements And Yttrium Research Articles

Geochemical studies on rock varnish and petroglyphs in the Owens and Rose Valleys, California.

We investigated rock varnish, a thin, manganese- and iron-rich, dark surface crust, on basaltic lava flows and petroglyphs in the Owens and Rose Valleys (California) by portable X-ray fluorescence (pXRF) and femtosecond laser-ablation inductively-coupled-plasma mass spectrometry (fs-LA-ICPMS). The major element composition of the varnish was consistent with a mixture of Mn-Fe oxyhydroxides and clay minerals. As expected, it contained elevated concentrations of elements that are typically enriched in rock varnish, e.g., Mn, Pb, Ba, Ce, and Co, but also showed unusually high enrichments in U, Cu, and Th. The rare earth and yttrium (REY) enrichment pattern revealed a very strong positive cerium (Ce) anomaly and distinct negative europium (Eu) and Y anomalies. The light rare earth elements (REE) were much more strongly enriched than the heavy REY. These enrichment patterns are consistent with a formation mechanism by leaching of Mn and trace elements from aeolian dust, reprecipitation of Mn and Fe as oxyhydroxides, and scavenging of trace elements by these oxyhydroxides. We inferred accumulation rates of Mn and Fe in the varnish from their areal densities measured by pXRF and the known ages of some of the lava flow surfaces. The areal densities of Mn and Fe, as well as their accumulation rates, were comparable to our previous results from the desert of Saudi Arabia. There was a moderate dependence of the Mn areal density on the inclination of the rock surfaces, but no relationship to its cardinal orientation. We attempted to use the degree of varnish regrowth on the rock art surfaces as an estimate of their age. While an absolute dating of the petroglyphs was not possible because of the lack of suitable calibration surfaces and a considerable amount of variability, the measured degree of varnish regrowth on the various petroglyphs was consistent with chronologies based on archeological and other archaeometric techniques. In particular, our results suggest that rock art creation in the study area continued over an extended period of time, possibly starting around the Pleistocene/Holocene transition and extending into the last few centuries.

Evidence for an Early-Middle Jurassic fluid event constrained by Sm–Nd, Sr isotopes, rare earth elements and yttrium in the Bowen Basin, Australia

The Late Permian coal measures in the Bowen Basin, Australia, are extensively mineralized with calcite as cleat infilling and veins. This study utilised strontium and samarium‑neodymium isotope analyses as well as rare earth element and yttrium (REY) composition of vein calcites, from two boreholes in a faulted and intruded area within the Jellinbah Thrust Zone, to investigate the origin and timing of calcite precipitation. All samples showed low Sr isotopic ratios that overlapped the range typical of mantle materials, suggesting that fluids were derived from the mantle. The calcite veins in core from Dingonose 14, with two exceptions, exhibit very similar Sr isotopic ratios yet have large variations in REY patterns and a wide range in Sm–Nd ratios. These samples defined an isochron corresponding to an age of 174 ± 11 Ma, which may record the timing of fluid mobilization from the deeply buried part of the foreland basin during the Early and Middle Jurassic, prior to subsequent extension and uplift in the Late Cretaceous. This fluid event may be a response to the Gondwana supercontinent break-up during the Early-Middle Jurassic. Various thermal and chemical conditions resulted in the different REY patterns of calcite in Dingonose 14 core. Calcite veins in Summit 3 core showed extremely similar REY patterns and Sr isotopic ratios but different Sm–Nd isotopic compositions relative to Dingonose 14 core, with no Sm–Nd isochron able to be resolved. The structural geology of the Summit 3 locality is complex, having overturned beds and large veins of prismatic quartz present in addition to calcite, and potential for multiple periods of veining to have occurred. Hence the lack of Sm–Nd isotopic equilibrium for the Summit 3 samples is most likely due to multiple fluid events.

Mineralogical and Chemical Characteristics of Coal Ashes from Two High-Sulfur Coal-Fired Power Plants in Wuhai, Inner Mongolia, China

The mineralogical and chemical characteristics of the feed coals and coal combustion products (CCPs) from two power plants (Xilaifeng and Damo) that consume coals from the Wuda Coalfield, Inner Mongolia, were investigated, using XRD, SEM–EDS, XRF, and ICP-MS. The feed coals from Xilaifeng and Damo are both of high ash yield (52.93% and 48.36%, respectively), and medium and high total sulfur content (2.22% and 3.32%, respectively). The minerals in the feed coals are primarily composed of kaolinite, quartz, illite, pyrite, and, to a lesser extent, gypsum and anatase. In addition to the elevated incompatible elements (Nb, Ta, Zr, Hf and Th), Li and Hg are enriched in the feed coals from the Xilaifeng and Damo power plants, respectively. Rare earth elements and yttrium (REY) are more enriched in the feed coals from Xilaifeng (194 μg/g) than those of Damo (93.9 μg/g). The inorganic phases of CCPs from both power plants are mainly composed of amorphous phase, quartz, hematite, illite, and anhydrite. Compared with the feed coals, concentrations of most trace elements in the CCPs are elevated, and they are preferentially enriched in the fly ashes relative to the bottom ashes (*f/b > 1), especially F, As, Sr, Mo, Se, and Hg (*f/b > 2.5). Furthermore, most trace elements (Xilaifeng: excluding Li, Cr, Co, Ni, Rb, Nb and Cs; Damo: excluding Li, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Cs and Ba) are more enriched in the (fine) fly ashes relative to the laboratory high-temperature coal ashes (HTAs). The REY barely differentiate in either the fly ash or bottom ash from Xilaifeng. In contrast, the REY in the fine and coarse fly ashes from Damo have very similar H-type distribution patterns with negative Ce and slightly positive Y anomalies. Attention should be paid to the enriched toxic elements (including F, As and Hg) in the fly ashes from both power plants due to possible adverse environmental effect.

Chemostratigraphy of deep-sea sediments in the western North Pacific Ocean: Implications for genesis of mud highly enriched in rare-earth elements and yttrium

Deep-sea sediments containing high concentrations of rare-earth elements and yttrium (REY), termed REY-rich mud, are widely distributed in the Pacific and Indian oceans. Mud layers with very high total REY (ΣREY) concentrations (>5000 ppm of ΣREY with ~1000 ppm of heavy rare-earth elements) have been discovered within the Japanese exclusive economic zone surrounding Minamitorishima Island, western North Pacific. The number of highly REY-enriched layers in the sediment column, the depths at which the layers occur, and the maximum ΣREY values of the layers are, however, quite variable on a scale of several tens of kilometers. The factors controlling the formation and distribution of the REY-enriched layers are still poorly understood. Here, we produce a chemostratigraphic scheme for 1240 sediment samples from 49 piston cores collected within the Minamitorishima exclusive economic zone. Detailed investigation of the bulk sediment geochemistry, which exhibits distinctive compositional data structures in multi-elemental subspaces, revealed that the samples can be categorized into five units (Units I to V) in addition to REY peaks (>2000 ppm). These units appear in a consistent stratigraphic sequence in the studied cores. This chemostratigraphy reveals that highly REY-enriched layers formed at least three times, and that almost all of these layers were accompanied by erosion during deposition. Our results suggest that erosion events of deep-sea sediment play an important role in the formation of highly REY-rich mud layers.

Recovery of rare earth elements from coal fly ash by integrated physical separation and acid leaching

Coal fly ash (CFA) is one of the most promising secondary sources of rare earth elements and yttrium (REY). This research first studied the modes of occurrence of REY in CFA collected from a China’s power generation plant which utilizes a coal feedstock with an elevated REY content. The fact that rare earth minerals remain in CFA and REY associate with metal oxides was proved by emission-scanning electron microscope with an energy-dispersive X-ray spectrometer. The technical feasibility of recovery of REY from CFA was then studied through conducting various physical separation methods followed by acid leaching. It was found that REY are concentrated in fine particle size, non-magnetic and middle density fractions. Using combined physical separation processes, the REY of CFA was enriched from 782 μg·g−1to 1025 μg g−1. The acid leaching process was optimized for various parameters via the Taguchi three-level experimental design. Upon optimization, the physical separation product was leached at the optimum condition and 79.85% leaching efficiency was obtained. Based on the obtained results, a conceptual process flowsheet was developed for recovery of REY from CFA. Such recovery maximizes REY resources utilization and enhances sustainability of CFA disposal.

Rare Earth Elements and carbon nanotubes in coal mine around spontaneous combustions

Increasing population growth and rise global energy petition have made congregation the requests of energy generation and safety a major challenge global. In another hand nanogeoscience is commencing to develop a viable remediation approach of attention in coal mine drainage (CMD) around spontaneous coal combustion (SCC). On the ecological context, nanophases (minerals and/or amorphous phases) are more reactive than bulk compounds, a property that powerfully influences the fate of pollutants in topsoils and drainages. In this work petrographic and geochemical investigations of selected CMD sediments were conducted. The substitution of As, Cd, Hg, and Se in pyrite was most apparent in the CMD sediments. The sampled CMD contained carbon nanotube (CNTs) structures and many others C-nanophases. The CNTs contained several elements, including Hg, Pb, F, Cl, and halogens. While CNTs are known to be produced from coal fires of varying ranks, this seems to be the first report of naturally occurring CNTs. This work also denotes the occurrence of historical NPs-locations in near vicinity to all other, as for illustration deposits of C-NPs and non-crystalline compounds appear only nano-meters separately from each other on the contradictory sides of non-altered amorphous phases. In addition, non-conventional sources, including CMD hosting elevated concentrations of Rare Earth Elements and Yttrium (REY), have been explored as attractive secondary sources for elements recovery. Consequently, in this study we investigate CMD from abandoned coal mines in the South America as a potential REY resource. It is suggested that more work is required on CMD and a few research areas are proposed for future research.

Occurrence of rare earth element and yttrium (REY) in Tanjung formation coking coal from Sekako area, Central Kalimantan

Inorganic geochemistry of coal become a point of interest on coal study, especially relating with the occurrence of rare earth element. Tanjung Formation is one of coking coal bearing deposits in Barito Basin, Central Kalimantan. The aims of this study to determine the occurrence of Rare Earth Element and Yttrium (REY) especially in term of concentration and enrichment type in coal seam A and B of Tanjung Formation in Sekako Area, Central Kalimantan. A number of 10 coal samples were collected from both seams. Inductively Coupled Plasma-Atomic Spectroscopy (ICP-AES) analysis was conducted to determine the REY in coal. Based on this study, coal seam A and B generally have very low concentration of REY elements deposits. The REY elements of coal seam A and B in the study area are typically characterized with M and H-type enrichment, which might be caused by the mafic basalt rocks in the surroundings.

Partitioning of rare earth elements and yttrium (REY) in five coal-fired power plants in Guizhou, Southwest China

As indispensable strategic materials for high-tech industries, rare earth elements and yttrium (REY) have become particularly important in recent years, raising the demand of developing new approaches for reclamation of REY from REY-rich materials such as coal combustion products (CCPs). In this study, five coal-fired power plants (CFPPs) in Guizhou of southwest China were selected for investigating REY concentrations of solid samples, atmospheric emissions, and recovery potentials. REY concentrations of feed fuels are higher in this study (147.2–468.6 mg/kg) than what have been reported previously for coals in China and the world. REY atmospheric emissions are extremely low (38.70–180.11 mg REY/t coal). REY are enriched in bottom ash and fly ash, with average of 658 ± 296 mg/kg and maximum of 1257 mg/kg from the five CFPPs. Relative enrichment factors (REF) of REY in bottom ash and fly ash compared with the feed fuel are 0.86–1.02 and 0.91–1.04, respectively. REY concentrations in desulfurized gypsum are very low (6–17 mg/kg), and that is mostly inherited from limestone. Critical REY (Nd, Eu, Tb, Dy, Y, and Er) in bottom/fly ash account for 34%–39% of the total REY and the outlook coefficients (Coutl) are in the range of 0.89–1.11. This study indicates a promising prospect to reclaim REY from REY-rich CCPs (bottom and fly ash) in CFPPs in Guizhou, especially in the central-north Guizhou, although such practices require further technology advancement.

Small-scale heterogeneity of trace metals including rare earth elements and yttrium in deep-sea sediments and porewaters of the Peru Basin, southeastern equatorial Pacific

Abstract. Due to its remoteness, the deep-sea floor remains an understudied ecosystem of our planet. The patchiness of existing data sets makes it difficult to draw conclusions about processes that apply to a wider area. In our study we show how different settings and processes determine sediment heterogeneity on small spatial scales. We sampled solid phase and porewater from the upper 10 m of an approximately 7.4×13 km2 area in the Peru Basin, in the southeastern equatorial Pacific Ocean, at 4100 m water depth. Samples were analyzed for trace metals, including rare earth elements and yttrium (REY), as well as for particulate organic carbon (POC), CaCO3, and nitrate. The analyses revealed the surprisingly high spatial small-scale heterogeneity of the deep-sea sediment composition. While some cores have the typical green layer from Fe(II) in the clay minerals, this layer is missing in other cores, i.e., showing a tan color associated with more Fe(III) in the clay minerals. This is due to varying organic carbon contents: nitrate is depleted at 2–3 m depth in cores with higher total organic carbon contents but is present throughout cores with lower POC contents, thus inhibiting the Fe(III)-to-Fe(II) reduction pathway in organic matter degradation. REY show shale-normalized (SN) patterns similar to seawater, with a relative enrichment of heavy REY over light REY, positive LaSN anomaly, negative CeSN anomaly, and positive YSN anomaly and correlate with the Fe-rich clay layer and, in some cores, also correlate with P. We therefore propose that Fe-rich clay minerals, such as nontronite, as well as phosphates, are the REY-controlling phases in these sediments. Variability is also seen in dissolved Mn and Co concentrations between sites and within cores, which might be due to dissolving nodules in the suboxic sediment, as well as in concentration peaks of U, Mo, As, V, and Cu in two cores, which might be related to deposition of different material at lower-lying areas or precipitation due to shifting redox boundaries.

Sequential particle-size and magnetic separation for enrichment of rare-earth elements and yttrium in Indonesia coal fly ash

Coal fly ash is known to contain rare-earth elements and yttrium (REY). In this research, three Indonesian coal fly ashes were characterized and subjected to sequential physical separation processes. The characterization results showed that the ashes had a critical REY content exceeding 38 % and outlook coefficient (Coutlook) of 1.1 - 1.2; however, enrichment is required prior to REY recovery. Coal fly ash from the Indramayu power plant also contained high concentrations of Fe2O3 and CaO, which occurred as magnetite, hematite, spinel, and srebrodolskite. Sequential physical separation consisting of sieving and magnetic separation was conducted to enrich the REY content of this ash. The sieving results showed that the REY content increased with a decrease of particle size. The highest REY recovery (58.69 %) and enrichment factor (1.1) were obtained in ashes with a size fraction of < 38 μm. Magnetic separation results showed that the nonmagnetic fraction contained more REY than the magnetic fraction. The enrichment factor and REY recovery in the magnetic separation step were 1.12 and 91.64 %, respectively. Overall REY recovery for the sequential separation process was 71.21 %, with an overall enrichment factor of 1.23. Sieving followed by magnetic separation effectively decreased the Fe2O3 and CaO contents of this fly ash.

Rare earth elements and carbon-oxygen isotopes of calcite from the Tongjiachong Cu deposit, South China: Implications for fluid source and mineral precipitation

Calcite is a major gangue mineral in many types of hydrothermal deposits, and its chemical and carbon-oxygen isotopic signatures can shed light on the metallogenic evolution. The Tongjiachong Cu deposit, located in the northern margin of the Yangtze Block in South China, is hosted by dolostone of the Ediacaran Doushantuo Formation. Empirical geothermometric calculation indicates that the pre-ore chlorite was formed at 265–305 °C. Copper mineralization occurs mainly as veinlets in a calcite-chalcopyrite-bornite ± ankerite assemblage. Exsolution lamellae of chalcopyrite from bornite indicate that both minerals were formed coevally at 200–250 °C. Mineral chemical analysis on the syn-ore hydrothermal calcite from Tongjiachong suggests that all the calcite samples are enriched in rare earth elements and yttrium (REYs) (ΣREY = 53.7–119.9 ppm). They have similar Y/Ho (38.3–42.3) and varying La/Ho (21.8–86.7), and display consistent convex PAAS-normalized REY patterns. The distinct positive Eu anomalies (2.38–3.45) and lack of Yb anomalies (0.92–1.05) suggest initial fluid temperatures of 250 to 420 °C and calcites deposition temperatures of <250 °C. The lack of negative Ce anomalies reflects suboxic to anoxic conditions of the ore-forming fluids.Dolomite samples from the dolostone ore host show a marine carbonate C-O isotopic affinity (13CPDB = −4.0 to −2.7‰; δ18OSMOW = +19.8 to +20.2‰). Comparatively, the hydrothermal calcite contains lower 13CPDB (−7.4 to −6.1‰) and δ18OSMOW (+14.1 to +14.8‰), and display a positive 13CPDB vs. δ18OSMOW correlation. Simulated calculations of water-rock (W/R) interactions and ore geological constraints suggest that the initial fluids were likely originated from organic-rich formation water. We proposed that W/R reactions may have been the main drive for calcite precipitation at Tongjiachong, whilst decreasing temperature and W/R reactions may have led to the chalcopyrite precipitation.

Rare Earth Elements and Yttrium (REY) in coal mine drainage from the Illinois Basin, USA

The ever-growing demand in the USA and in the modern economy for rare earth elements, defined here as the lanthanide elements plus yttrium (REY), motivates the development of economically feasible and environmentally friendly approaches for domestic REY resources. Non-conventional sources, including coal mine drainage (CMD) hosting elevated concentrations of REY, have been explored as attractive secondary sources for metals recovery. Consequently, in this study we investigate CMD from abandoned coal mines in the Illinois Basin as a potential REY resource.We collected CMD from 35 abandoned coal mine sites in the Illinois Basin and investigated trends in REY enrichment and their association with CMD geochemical characteristics, including pH, the presence of other chemical elements of economic significance (i.e., Zn, Ni, Cr, Cu, V) as well as spatial patterns in relation to Permian magmatic intrusions of the Hicks Dome, a potential source of REY in the Illinois Basin. Additionally, the REY contents in possible source rocks for Illinois CMD were measured including coal from an underground mine and coal preparation plant in southern Illinois, mafic igneous rocks associated with Hicks Dome, and hydrothermal fluorite from Illinois fluorspar district.The REY concentrations in samples of CMD (filtered fraction) and associated coal and non-coal solids were determined by ICP-MS. The total concentration of REY in CMD, ΣREYCMD varied between 1 and 9879 μg/L with an average of 1059 μg/L and critical-ΣREYCMD (Nd, Eu, Tb, Dy, and Y) varied between 0.3 and 7212.5 μg/L with an average of 611 μg/L. Basin-wide, we found no statistical correlation between ΣREYCMD and (1) pH of the CMD, or (2) proximity to the Permian magmatic intrusion at Hicks Dome in southern Illinois. The REYCMD values normalized to North American Shale Composite (NASC) REYCMD/REYNASC exhibit enrichments in middle-REY for all CMD, but also enrichments in light-REY in some CMD. Statistically, we observed that ΣREYCMD displays significant direct correlations with Al, Si, SO4, Zn, Ni, Co, and Cu and no-correlation with Fe, Ca, PO4, Ba, and V.Synthesis of the geochemical data suggests that coal mining sites with the highest ΣREYCMD and critical-ΣREY contents include non-coal bedrock dominated by silicates (high clay content) and coal mine wastes that were impacted by metal-rich hydrothermal solutions, which are predominantly located along the western and northern margins of the Illinois Basin. Particularly, sites with the highest hydrothermal input as approximated by Mississippi Valley-type mineralization (i.e., Zn contents) are prime candidates for REY, as well as other elements of potential economic value such as Al, Ni, Cr, V, and Co. Thus, CMD in the Illinois Basin could become a potential alternative domestic source of extractable REY, especially critical-ΣREY, as well economically valuable metals.

Biological treatment removal of rare earth elements and yttrium (REY) and metals from actual acid mine drainage.

Actual acid mine drainage (AMD) containing a high concentration of sulfate (∼1,000 mg·L-1), dissolved metals, uranium, rare earth elements and yttrium (REY) was treated using a down-flow fixed-structured bed biological reactor (DFSBR). The reactor was operated in a continuous flow mode for 175 days and the temperature was maintained at 30 °C. The synthetic AMD was gradually replaced by the actual AMD in 20, 50 and 75% of the total medium volume. Sugarcane vinasse was used as the electron donor and the influent pH of the reactor was decreased from 6.9 to 4.6 until the system collapsed. REY elements and transition metals were removed from the actual AMD and precipitated in the down-flow fixed-structured bed reactor. Sulfate reduction achieved 67 ± 22% in Phase II and chemical oxygen demand (COD) removal was above 56% in Phases I and II. Removal of La, Ce, Pr, Nd, Sm and Y was higher than 70% in both Phases II and III while Fe, Al, Si and Mn were removed with efficiencies of 79, 67, 48 and 25%, respectively. The results highlighted the potential use of DFSBR in the treatment of AMD, providing possibilities for simultaneous sulfate reduction and metal and REY recovery in a single unit.

Accumulation patterns and species-specific characteristics of yttrium and rare earth elements (YREEs) in biological matrices from Maluan Bay, China: Implications for biomonitoring

The critical usage of rare earth elements (REEs) in a variety of industrial applications has increased their release to the environment as emerging contaminants, while little is known about the fate and transport of REEs in coastal aquatic biota. In the present study, seven common species were collected and the concentrations of 15 naturally occurring REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) were determined. Significant differences in total REEs concentrations were found among species even in the same taxa or phylum, suggesting that REEs bioaccumulation patterns appeared to be species- and element-dependent even in the same taxa or phylum, but with limited potential for bio-magnification based on the nitrogen isotope signatures (δ15N). Except for occasional anomalies for redox-sensitive elements of Ce and Eu, the abundance patterns of REEs normalized to chondrite revealed similar REE distribution trends, indicating a common source of REEs in all samples. Additionally, the abundances of light REEs (from La to Eu) were much higher than those of heavy REEs (from Gd to Lu and Y), demonstrating the fractionation between the light and heavy REEs. Furthermore, REEs concentrations in molluscs were notably higher than other species, implying their potential as bio-indicators of REEs due to the habitat and specific feeding behavior. Overall, this is not only the first study to focus on distribution levels, accumulation characteristics, geochemical and fractionation patterns of REEs in coastal species from identical area, but quantifying and tracing REE behavior will contribute to better evaluating the possible environmental impacts of REEs enrichment for future biomonitoring research.

Significant impacts of pelagic clay on average chemical composition of subducting sediments: New insights from discovery of extremely rare-earth elements and yttrium-rich mud at Ocean Drilling Program Site 1149 in the western North Pacific Ocean

Subduction of oceanic sediments is known to have a large impact on the chemical evolution of the continental crust and mantle. Therefore, bulk chemical composition of subducting sediments has long been studied to elucidate geochemical cycles through subduction zones. Recent researches on oceanic sediments have discovered thin layers (<1 m in thickness) with extraordinarily high concentrations of rare-earth elements and yttrium (REY) in pelagic clay, demonstrating that the bulk chemical compositions of the pelagic clay are more heterogeneous than previously thought. However, in previous studies on subduction recycling, sampling densities (>5 m interval) were not high enough to detect such compositional peaks and thus, the heterogeneities in pelagic clay were not fully considered. Here we present new, high-resolution (0.25–1.5 m interval) bulk chemical compositions of unlithified sediments obtained from Ocean Drilling Program Site 1149. We identified distinct pelagic clay layers highly enriched in several characteristic elements, including a layer reaching a total REY concentration of 7500 ppm. Then, the average composition of the sediment column at Site 1149 was evaluated. Compared to the previous estimation, our high-resolution data significantly revise the average composition of the pelagic clay unit (e.g. +27% for Co, +32% for P2O5, +20–48% for REY). This in turn affects the average composition of whole sediment column (e.g. +19% for Co, +9% for P2O5, +11–15% for REY). Our results indicate that the high-resolution analyses of pelagic clay are very important for understanding global geochemical cycles.

Rare Earth Elements and Yttrium (REY) Geochemistry of Reefal Limestones in the Ordovician, Tarim Basin, NW China and their Paleoenvironment Implications

This study examines the rare earth elements and yttrium (REY) concentrations of twenty‐five samples from the reef outcrop exposed along the Lianglitage Mountain in the Ordovician, Tarim Basin in China. The concentration analysis provides constraints on the paleoenvironment during reef deposition. Based on the detailed sedimentology and petrographic work, we divide the reef facies into four sub‐facies: the base facies, reef‐core facies, reef‐flank facies, and sealing facies. The geochemical data (such as major and trace elements, carbon and oxygen isotopes, and REYs) are further used to study the coeval seawater characteristics as well as potential diagenesis overprints. The result indicated that the diagenesis has little effect on the REY patterns of the reefal limestones. The REY concentrations of the reefal limestones are overall low (ranging from 3.69 to 19.60 ppm, arithmetic mean=10.22 ppm, SD=5.4). The PAAS‐normalized REY patterns are consistently flat compared to the typical well‐oxidized, shallow marine water patterns. However, the light REE (LREE) depletions, positive La anomalies, negative Ce anomalies and positive Y anomalies, suggest that these reefal limestones are likely an indicative of contemporaneous seawater REY signals. The seawater‐like Y/Ho ratios (average at 37.51) further support that REY signals in these limestones are likely a reflection of seawater with little diagenetic modifications. The low Y/Ho ratios presented only in the reef‐flank facies and sealing facies are likely a suggestion of detrital contamination. Hence, this study confirms that REY patterns of the limestones at the base facies and reef‐core facies can record ancient seawater information, and reefs can be used as a potential geochemical proxy for paleoenvironment studies throughout the Earth's history.

Concentrations and modes of occurrence of some potentially valuable and toxic elements in the No. 5 coal from the Yanzishan Mine, Datong Coalfield, Shanxi Province, China

In this study, the mineralogical compositions, concentrations and occurrence modes of the elements in the No.5 coal from the Yanzishan Mine were investigated, using X-ray powder diffraction (XRD), X-ray fluorescence spectrometry (XRF), inductively coupled plasma mass spectrometry (ICP-MS), and scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer (SEM-EDS). The No. 5 coal is characterized by high ash yield content (mean 32.30%) and low sulfur content (mean 0.47%). The minerals are mainly composed of kaolinite, quartz and pyrite, with a small proportion of illite, apatite, siderite, sphalerite and Ti-oxide. Compared with the Chinese coals, the No. 5 coal has much higher percentages of SiO2 (mean 16.22%) and Al2O3 (mean 14.57%) than other major oxides. Compared with the world hard coals and Chinese coals, the No. 5 coal is enriched in some potentially valuable (Al2O3, Li, Ge, Zr, and Hf) and toxic (Be, As, Se, Cd, and Pb) elements. Lithium and Hf are mainly associated with clay minerals; Be, Se, and Zr mainly have both inorganically and organically affinities; As mainly occurs as a sulfide form in pyrite; Cd is incorporated in clay minerals; and Pb has an affinity for both clay minerals and organic sulfur. All the coal samples are characterized by weakly positive or no pronounced Eu anomalies, indicating that the rare earth elements and yttrium (REY) likewise originated from granite of the Yinshan Oldland together with injection of the low temperature hydrothermal fluids.

Statistic and Isotopic Characterization of Deep‐Sea Sediments in the Western North Pacific Ocean: Implications for Genesis of the Sediment Extremely Enriched in Rare Earth Elements

AbstractA certain type of deep‐sea sediment exhibits very high content of rare earth elements and yttrium (REY) and is therefore expected to serve as a novel resource for these industrially essential metals. In this paper, we statistically analyzed the bulk chemical composition of deep‐sea sediments collected from the western North Pacific Ocean. By applying independent component analysis to the multielemental data set, we extracted three independent components (ICs) that can be interpreted as the influence of Mn‐oxides (IC1), REY‐enriched biogenic calcium phosphate (IC2), and possibly a diagenetic effect involving Cu enrichment (IC3) on bulk sediment geochemistry. Subsequently, we selected representative samples based on the independent component analysis result, and implemented Sr–Nd–Pb isotopic analyses of bulk sediments. The results indicate that the extremely REY‐rich mud characterized by IC2 inherits the geochemical signature of deep Pacific seawater, whereas the non‐REY‐rich mud with less diagenetic alterations, characterized by IC3, implies an influence of terrigenous dust probably from the Taklimakan desert–Chinese loess plateau. IC1 may reflect the variation in sedimentation rates. Characteristic downhole variations of IC1 and IC3 scores imply the presence of hiatus and/or erosion of the sediment column across the REY content peak. The putative cause is an enhanced bottom current, which can physically separate coarse biogenic calcium phosphate grains with very high REY content and thus produce an extremely REY‐enriched sediment layer.

Origin of volcanic-hosted Mn-oxide mineralization from San Pietro Island (SW Sardinia, Italy): An integrated geochemical, mineralogical and isotopic study

The Mn-oxide mineralizations from Sardinia (Italy) represent examples of Mn deposits in a continental environment and, as such, their investigation can shed light on the genesis and characteristics of this deposit type, less studied than their more common oceanic counterpart. In this paper, the genetic mechanisms, the physical-chemical conditions and the origin of the mineralizing fluids are discussed for the volcanic-hosted Mn ores of the San Pietro Island (SW Sardinia), through an integrated geochemical, mineralogical and radiogenic isotope approach. New and published data are here examined on the basis of recent trace element discrimination schemes for Mn ores and a model for the genesis is proposed.The mineralogy of the alteration paragenesis (argillic facies) and the type of observed fluid inclusions (very small monophase liquid inclusions) suggest a circulation of mineralizing fluids characterized by weak acidic conditions (pH indicatively around 5) and relatively low temperature (<100–120 °C). Geochemical features such as the contents of transition metals (Mn, Fe, Cu, Co, Ni, Zn), and contents and ratios of rare-earth elements and yttrium (REY), suggest that the San Pietro Island Mn metallogenesis is the result of combined hydrothermal and hydrogenetic mechanisms of formation. The Pb isotope compositions of different Mn veins exhibit a significant spread that suggests the contribution of distinct mineralizing fluids, deriving their isotopic signature from both seawater and water-rock interaction processes.The possible model of formation of the San Pietro Mn mineralization can be viewed as a complex process, in which Mn-bearing fluids originated from remobilization of Mn oxides sequestered in shelf and slope sediments and/or from leaching of the older Cenozoic volcanic rocks that form the basement of the island. Fluid rise was due to hydrothermal convection, possibly related to the general thermal anomaly active in the area from 15 to 12 Ma, during the final stage of the intense Cenozoic volcanic activity of the Sulcis area (San Pietro, Sant'Antioco, Isola del Toro volcanic activity). The fluids were probably dominated by seawater, characterized by relatively low temperatures and acidic conditions, due to the input of H2S of hydrothermal origin. The Mn ore deposition occurred in relatively shallow water and oxidizing environment, following the pH neutralization induced by water-rock interaction processes.

Fe-Mn nodule morphotypes from the NE Clarion-Clipperton Fracture Zone, Pacific Ocean: Comparison of mineralogy, geochemistry and genesis

Ferromanganese nodules are polymetallic ore deposits considered to be archives of paleoceanographic proxies and targets of deep-sea mining. In the present paper, nodules and underlying sediments from a claim area (UK-1) within the eastern Clarion-Clipperton Fracture Zone (CCFZ) and from Area of Particular Environmental Interest (APEI-6) were analyzed. In each area, nodules are characterized by contrasting morphology, mineralogy, geochemistry and abundance. The obtained results reveal three types of Fe-Mn nodules. Type 1: smooth irregular nodules with sizes of 1–1.5 cm containing mainly 10 Å phyllomanganates and phillipsite; Mn/Fe = 2.50, high trace metal abundances Co + Ni + Cu = 2.10%, high rare earth element and yttrium (REY) concentrations (1515 ppm), positive Ce anomaly; hydrogenetic origin. Type 2: smooth discoidal nodules with sizes of 2–4 cm composed of 10 Å phyllomanganates and buserite I; Mn/Fe = 3.65, high trace metal enrichment Co + Ni + Cu = 2.35%, positive Ce anomaly; mainly formed by hydrogenous precipitation. Type 3: nodules (3–15 cm) with botryoidal surfaces and well-defined concentric zonality; Mn/Fe = 5.1, trace metal content Co + Ni + Cu = 2.42%. The textural and chemical characteristics of nodules suggest that they acquire metals as a result of both hydrogenetic and diagenetic processes during nodule growth in alternating oxic/suboxic conditions. Scanning electron microscopy (SEM), in conjunction with energy-dispersive X-ray spectroscopy (EDS), reveals abundant pseudomorphs, which is considered possible evidence for biomineralization within the nodules. The morphology, mineralogy and geochemistry of the studied nodules are strongly affected by post-accretional diagenetic processes, which are closely linked to biomineralization.