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1

The geochemistry of rare earth elements in the seasonally anoxic water column and porewaters of Chesapeake Bay  

Microsoft Academic Search

A twelve cruise time-series study of a seasonally anoxic basin in Chesapeake Bay was carried out between February 1988 and February 1989. Data from filtered bottom water and upper (0-1 cm) porewater samples are presented. This is the first study in which time-series measurements have been employed to understand the low temperature geochemistry of rare earth elements (REEs). The focus

E. R. Sholkovitz; T. J. Shaw; D. L. Schneider

1992-01-01

2

The geochemistry of rare earth elements in the Amazon River estuary  

SciTech Connect

The estuarine geochemistry of rare earth elements (REEs) was studied using samples collected in the Amazon River estuary from the AmasSeds (Amazon Shelf SEDiment Study) cruise of August 1989. Extensive removal of dissolved (0.22 [mu]m filtered) trivalent REEs from river water occurs in the low (0--6) salinity region. Removal by the salt-induced coagulation of river colloids leads to fractionation among the REE(III) series; the order of removal is light REEs > middle REEs > heavy REEs. There also is the enhanced removal of Ce (relative to trivalent La and Nd) in the low salinity (0--6) zone and in the zone of high biological activity. This is the first field observation of strong Ce removal associated with coagulation of river colloids and biological productivity. The argument is made that the decrease in the Ce anomaly across a biological front is caused by biologically mediated oxidation of Ce(III) to Ce(IV). Coagulation of river colloids and biologically mediated oxidation of Ce(III) lead to fractionation of REE(III) and redox modification of Ce. These processes result in the REE composition becoming fractionated relative to the Amazon River water and crust and more evolved toward the REE composition of the oceans. This study implies that reactions in estuaries play significant, yet poorly understood roles in controlling the REE composition and Ce anomaly of the oceans. 46 refs., 9 figs., 2 tabs.

Shokovitz, E.R. (Woods Hole Oceanographic Institution, MA (United States))

1993-05-01

3

Rethinking early Earth phosphorus geochemistry  

PubMed Central

Phosphorus is a key biologic element, and a prebiotic pathway leading to its incorporation into biomolecules has been difficult to ascertain. Most potentially prebiotic phosphorylation reactions have relied on orthophosphate as the source of phosphorus. It is suggested here that the geochemistry of phosphorus on the early Earth was instead controlled by reduced oxidation state phosphorus compounds such as phosphite (HPO32?), which are more soluble and reactive than orthophosphates. This reduced oxidation state phosphorus originated from extraterrestrial material that fell during the heavy bombardment period or was produced during impacts, and persisted in the mildly reducing atmosphere. This alternate view of early Earth phosphorus geochemistry provides an unexplored route to the formation of pertinent prebiotic phosphorus compounds, suggests a facile reaction pathway to condensed phosphates, and is consistent with the biochemical usage of reduced oxidation state phosphorus compounds in life today. Possible studies are suggested that may detect reduced oxidation state phosphorus compounds in ancient Archean rocks.

Pasek, Matthew A.

2008-01-01

4

Aquatic geochemistry of the rare earth elements and yttrium in the Pioneer River catchment, Australia  

Microsoft Academic Search

The rare earth elements are strong provenance indicators in geological materials, yet the potential for tracing provinciality in surface freshwater samples has not been adequately tested. Rare earth element and yttrium concentrations were measured at 33 locations in the Pioneer River catchment, Mackay, central Queensland,Australia. The rare earth element patterns were compared on the basis of geological, topographical and land-use

Michael G. LawrenceA; Stacy D. JupiterB; Balz S. KamberC

2006-01-01

5

Rare earth element geochemistry of South Atlantic deep sea sediments: Ce anomaly change at ~54 My  

NASA Astrophysics Data System (ADS)

The geochemistry of the REE (rare earth elements) in oceanic sediments is discussed, based mainly on samples from DSDP Holes 530A and 530B, Leg 75, and Hole 525A, Leg 74. The proposed mechanisms for incorporation of the REE into the marine carbonate phases are adsorption, chiefly onto the carbonate minerals and on Sc, Hf, and Ta-rich Fe-Mn hydroxide flocs as carbonate coatings. The Ce anomaly of marine carbonate was used as an indicator of paleo-ocean water redox conditions: the bottom water of the Angola Basin was in a reducing condition in the Cretaceous. At ca. 54 My, the South Atlantic water condition became oxidizing, similar to the present seawater redox condition. This change was related to the improvement of circulation due to the widening of South Atlantic and the subsidence of water circulation barriers such as the Walvis Ridge and perhaps the Romanche Fracture Zone. The younger (Eocene-Recent) and older (Albian-Santonian) argillaceous sedimentary rocks from 530A (denoted as YSAB and OSAB respectively) show different degrees of Eu depletion with a transition period in between. The REE patterns of OSAB suggest a basaltic origin. The possible sources are Kaoko basalt in Southwest Africa or Namibia and the basaltic Walvis Ridge itself. The decrease in the area covered by Kaoko basalt due to erosion, the subsidence of the Walvis Ridge, and the improvement of water circulation led to changes in the Eu anomaly from Campanian to Paleocene, and resulted in the YSAB REE pattern. Changes in the Sm/Eu, La/Th, Th/Yb, Ti/Al 2O 3, FeO/Al 2O 3, and Hf/Al 2O 3 ratios suggest changes of average source rock composition from and esite to granodiorite. The REE abundances and patterns of younger sediments in the Angola Basin (YSAB) are very similar to those observed in NASC, PAAS, and ES sediments. The YSAB REE abundances and patterns may represent the average REE distribution of the exposed African continental crust. The strong resemblance of REE distributions of YSAB, NASC, PAAS and ES suggests thorough REE mixing from different sources and the uniformity of the average crustal compositions of different continents: Africa, North America, Australia, and Europe

Wang, Y. L.; Liu, Y.-G.; Schmitt, R. A.

1986-07-01

6

Problems of Geochemistry.  

National Technical Information Service (NTIS)

Contents: Cosmochemistry and creation of the earth; Geochemistry of individual elements and isotopes; Genesis of rocks and geochemistry; Mineralogy and geochemistry; Geochemistry of the radioactive elements; Biogeochemistry; Geochemistry of the ocean; and...

N. I. Khitarov

1969-01-01

7

The rare earth element geochemistry of Mono Lake water and the importance of carbonate complexing  

Microsoft Academic Search

Rare earth element (REE) concentrations for the alkaline, saline waters of Mono Lake in eastern California are reported. The total REE concentrations of the lake water ranged from 4,68 1 to 7,979 pmol kg- I. Shale-normalized REE profiles for the lake water indicate that the heavy REEs (HREE) are enriched 20-200 times over the light REEs (LREE) compared to shale.

KEVIN H. JOHANNESSON; W. BERRY LYONS

1994-01-01

8

Rare earth element geochemistry of massive sulfides-sulfates and gossans on the Southern Explorer Ridge  

Microsoft Academic Search

Massive sulfide-sulfate deposits on the Southern Explorer Ridge were analyzed for 14 rare earth elements (REE) by a modified inductively coupled plasma-mass spectrometric technique that included a correction for high Ba content. Bulk samples of finely intermixed sulfides, sulfate, and amorphous silica contain ΣREE concentrations of ⤠6 ppm. REE patterns range from (1) strongly enriched in light REE with

Timothy J. Barrett; Ian Jarvis; Kym E. Jarvis

1990-01-01

9

The Aqueous Geochemistry of Trivalent Rare Earth Elements, Gallium and Indium Up to 250C  

NASA Astrophysics Data System (ADS)

The aqueous solution chemistry of trivalent REE, Ga and In at elevated temperatures is relevant to radioactive waste disposal,economic geology, environmental geochemistry and a variety of other applications. In each of these areas, the ability to model aqueous mass transfer of these elements is essential and dependent on the availability of high-quality thermodynamic data. There has been fairly intense study of aqueous REE complexation and REE solid-phase solubility recently. There are fewer studies of these properties for In and Ga. The available data are reviewed and discussed in this paper. Experimentally measured stability constants at elevated temperatures are available for REE complexes with acetate, chloride, fluoride, hydroxide, and sulfate. Solubility products at elevated temperatures have been determined for selected solid REE fluoride, hydroxide and phosphate phases. The experimental data show that acetate complexes are more stable and fluoride and hydroxide complexes are less stable than predicted based on extrapolation of stability constants determined at standard conditions. The measured stability constants for chloride and sulfate complexes are in reasonable agreement with predicted values. At elevated temperatures, the stabilities of both chloride and fluoride complexes decrease with increasing atomic number across the REE series. The experimental data suggest that chloride complexation is likely to be more important relative to hydroxide and fluoride complexation than predicted from extrapolations. Lack of data prevent definitive conclusions for Ga and In. However, there are some similarities of Ga and In with the REE. In particular, chloride complexes are likely to be less important for Ga than the REE and more important for In. Bisulfide complexation could conceivably play a role for In transport.

Wood, S. A.

2011-12-01

10

The rare earth element geochemistry of granite, gneiss, and migmatite from the Western Metamorphic Belt of South-eastern Australia  

Microsoft Academic Search

Four muscovite-biotite granites from the Western Metamorphic Belt of South-eastern Australia have rare earth element patterns characterized by: (i) light rare earth element enrichment; (ii) slight Eu depletion; (iii) varying degrees of heavy rare earth element depletion. The rare earth element and major element chemistry of three of these muscovite-biotite granites (the Koetong, Lockharts and Yabba Granites) can be approximated

R. C. Price; S. R. Taylor

1977-01-01

11

The Use of Lead Isotope and Rare Earth Element Geochemistry for Forensic Geographic Provenancing  

NASA Astrophysics Data System (ADS)

Lead isotope and rare earth element composition of modern human bones are analyzed to explore their utility for geographical provenancing. DNA analysis is the standard for identification of individuals. DNA analysis requires a DNA match for comparison. Thus, DNA analysis is of limited use in cases involving unknown remains. Trace elements are incorporated into bones and teeth during biomineralization, recording the characteristics of an individual's geochemical environment. Teeth form during adolescence, recording the geochemical environment of an individual's youth. Bones remodel throughout an individual's lifetime. Bones consist of two types of bone tissue (cortical and trabecular) that remodel at different rates, recording the geochemical environment at the time of biomineralization. Cortical bone tissue, forming the outer surface of bones, is dense, hard tissue that remodels in 25-30 yrs. Conversely, trabecular bone tissue, the inner cavity of bones, is low density, porous and remodels in 2-5 years. Thus, analyzing teeth and both bone tissues allows for the development of a geographical time line capable of tracking immigration patterns through time instead of only an individual's youth. Geochemical isotopic techniques (Sr, O, C, N) have been used for geographical provenancing in physical anthropology. The isotopic values of Sr, C, O, N are predominantly a function of soil compositions in areas where food is grown or water is consumed. Application of these provenancing techniques has become difficult as an individual's diet may reflect the isotopic composition of foods obtained at the local grocer as opposed to local soil compositions. Thus, we explore the use of REEs and Pb isotopes for geographical provenancing. Pb and REEs are likely more reliable indicators of modern geographical location as their composition are high in bio-available sources such as local soils, atmospheric aerosols, and dust as opposed to Sr, C, O, N that are controlled by food and drinking water. Lead isotope and REE analysis of trabecular and cortical bone tissue of 60 femoral heads resected during hip replacement surgery at the Univ. of Roch. Medical Center were analyzed by a combination of TIMS and ICP-MS. Results show that Pb compositions are consistent with local soil with variable inputs from known environmental sources. Several samples demonstrate inputs from known environmental sources (e.g. Mississippi Valley ore) that was used in paint, solder, and US gasoline. Additionally, results suggest bioincorporation of Pb with isotopic composition consistent with that observed for Canadian gasoline aerosols. Immigrants included in the study show Pb compositions distinctly different than local residents.

Carey, A.; Darrah, T.; Harrold, Z.; Prutsman-Pfeiffer, J.; Poreda, R.

2008-12-01

12

Rare earth element geochemistry in cold-seep pore waters of Hydrate Ridge, northeast Pacific Ocean  

NASA Astrophysics Data System (ADS)

The concentrations of rare earth elements (REEs), sulphate, hydrogen sulphide, total alkalinity, calcium, magnesium and phosphate were measured in shallow (<12 cm below seafloor) pore waters from cold-seep sediments on the northern and southern summits of Hydrate Ridge, offshore Oregon. Downward-decreasing sulphate and coevally increasing sulphide concentrations reveal sulphate reduction as dominant early diagenetic process from ~2 cm depth downwards. A strong increase of total dissolved REE (?REE) concentrations is evident immediately below the sediment-water interface, which can be related to early diagenetic release of REEs into pore water resulting from the re-mineralization of particulate organic matter. The highest pore water ?REE concentrations were measured close to the sediment-water interface at ~2 cm depth. Distinct shale-normalized REE patterns point to particulate organic matter and iron oxides as main REE sources in the upper ~2-cm depth interval. In general, the pore waters have shale-normalized patterns reflecting heavy REE (HREE) enrichment, which suggests preferential complexation of HREEs with carbonate ions. Below ~2 cm depth, a downward decrease in ?REE correlates with a decrease in pore water calcium concentrations. At this depth, the anaerobic oxidation of methane (AOM) coupled to sulphate reduction increases carbonate alkalinity through the production of bicarbonate, which results in the precipitation of carbonate minerals. It seems therefore likely that the REEs and calcium are consumed during vast AOM-induced precipitation of carbonate in shallow Hydrate Ridge sediments. The analysis of pore waters from Hydrate Ridge shed new light on early diagenetic processes at cold seeps, corroborating the great potential of REEs to identify geochemical processes and to constrain environmental conditions.

Himmler, Tobias; Haley, Brian A.; Torres, Marta E.; Klinkhammer, Gary P.; Bohrmann, Gerhard; Peckmann, Jörn

2013-07-01

13

Mineralogy and geochemistry of trace and Rare Earth Element from the Manaila massive sulphide deposit (Eastern Carpathians, Romania)  

NASA Astrophysics Data System (ADS)

Keywords: Eastern Carpathians, M?n?ila deposit, REE, trace elements, pyrite The present paper deal with the mineralogy and trace elements geochemistry of sulphide deposits from M?n?ila mine field located in NE area of Eastern Carpathians Mountains (Romania). The mineralization occurs within metamorphic rocks of Tulghe? terrane, part of Crystalline-Mezozoic zone of the Eastern Carpathians. The metamorphic rocks in M?n?ila area consist of felsic metavolcanics rocks with quartzites and quartz-feldspathic rocks as prevailing types. The P-T metamorphic conditions are typical of greenschis facies with biotite and garnet (Mn-Grt) in mineral assemblage. The mineralogical study was performed using reflected light microscope and Scanning Electron Microscopy (SEM) methods. Thus, the both methods show that the main sulphides minerals are represented by pyrite and chalcopyrite, being followed by sphalerite, galena and little amount of Cu sulphosalts (tetrahedrite and bournonite) and also by gangue minerals (quartz and carbonates). Pyrite occurs as large euhedral to subhedral grains in quartz and small rounded inclusion in chalcopyrite. The trace elements analysis was achieved on whole-rock samples and involved the determination of REE, LIL (Rb, Ba, Sr) and HFS (Y, Zr, Hf, U, Th, Nb, Ta) by ICP-MS method. The concentration of LIL and HFS trace elements in mineralized rocks decrease as follows: Ba > Bi > As > Sb > Co > Ga > Ni > Cd. Even if the barium contents in M?n?ila ore is high, baritina (BaSO4) was not identified throught the mineralogical analyses carried out so far. The total rare earth element content (REE) of the samples from M?n?ila range from 26.84 to 246.46 ppm. Chondrite - normalized REE patterns of the mineralized rocks show that the LREE are enriched in relation to the HREE. Also a positive Ce anomalies and negative Eu anomalies are present. Y/Ho and Zr/Hf ratios are close to the chondritic ratios indicating Charge-and-Radius-Controlled (CHARAC) behavior of these elements in pure silicate melts. The REE patterns of the ores are highly variable and do not appear to be related to the mineral compositions. This feature may reflect contributions from several factors involved in fluid formation, ore mineral deposition and post-depositional processes. The lack of a relation between major mineral composition and REE patterns suggests complex REE fractionation processes during the ore formation. This work was supported by the European Social Fund in Romania, under the responsibility of the Managing Authority for the Sectoral Operational Programme for Human Resources Development 2007-2013 (grant POSDRU/88/1.5/S/47646).

Moldoveanu, S.; Iancu, O. G.; Kasper, H. U.

2012-04-01

14

Strontium isotopes and rare-earth element geochemistry of hydrothermal carbonate deposits from Lake Tanganyika, East Africa  

NASA Astrophysics Data System (ADS)

At Cape Banza (North Tanganyika Lake), fluids and aragonite chimneys have been collected many times since the discovery of this sublacustrine field in 1987. This sampling has been investigated here for the Sr isotopic compositions and the rare-earth element features of the carbonates and a few fluid samples. The 87Sr/ 86Sr ratios of the chimneys indicate that they have precipitated from a mixture of lake water (more than 95%) and hydrothermal fluids. No zoning in the chimneys was detected with our Sr data. For the rare-earth elements, the situation is more complex. The external walls of the chimneys are rare-earth-element-poor (La ? 500 ppb, Yb ? 200 ppb, La/Yb = 2 to 3.4). Their shale normalised rare-earth element patterns suggest that they are in equilibrium with the inferred carbonate-depositing fluids. The rare-earth element concentrations of the internal walls of the chimneys are significantly light rare earth elements (LREE)-enriched with La contents sometimes up to 5 ppm. We suggest that they contain more vent-fluid rare-earth elements than the external wall samples, possibly adsorbed on the surface of growing crystals or simply hosted by impurities. It was not possible to constrain the nature of these phases, but the variations of the compositions of the internal wall materials of the active chimneys with time, as well as data obtained on an inactive chimney indicate that this rare-earth element excess is mobile. Partition coefficients were calculated between the external wall aragonite and carbonate-depositing fluid. The results are strikingly similar to the values obtained by Sholkovitz and Shen (1995) on coral aragonite, and suggest that there is no significant biologic effect on the incorporation of rare-earth elements into coral aragonite and that the various carbonate complexes involved Me(CO 3+) complexes are the main LREE carriers in seawater (Cantrell and Byrne, 1987) instead of Me(CO 3) 2- in Banza fluids) have the same behaviour during aragonite precipitation.

Barrat, J. A.; Boulègue, J.; Tiercelin, J. J.; Lesourd, M.

2000-01-01

15

Strontium isotopes and rare-earth element geochemistry of hydrothermal carbonate deposits from Lake Tanganyika, East Africa  

SciTech Connect

At Cape Banza (North Tanganyika Lake), fluids and aragonite chimneys have been collected many times since the discovery of this sublacustrine field in 1987. This sampling has been investigated here for the Sr isotopic compositions and the rare-earth element features of the carbonates and a few fluid samples. The {sup 87}Sr/{sup 86}Sr ratios of the chimneys indicate that they have precipitated from a mixture of lake water (more than 95%) and hydrothermal fluids. No zoning in the chimneys was detected with the Sr data. For the rare-earth elements, the situation is more complex. The external walls of the chimneys are rare-earth-element-poor (La {approx} 500 ppb, Yb {approx} 200 ppb, La/Yb = 2 to 3.4). Their shale normalized rare-earth element patterns suggest that they are in equilibrium with the inferred carbonate-depositing fluids. The rare-earth element concentrations of the internal walls of the chimneys are significantly light rare earth elements (LREE)-enriched with La contents sometimes up to 5 ppm. The authors suggest that they contain more vent-fluid rare-earth elements than the external wall samples, possibly adsorbed on the surface of growing crystals or simply hosted by impurities. It was not possible to constrain the nature of these phases, but the variations of the compositions of the internal wall materials of the active chimneys with time, as well as data obtained on an inactive chimney indicate that this rare-earth element excess is mobile. Partition coefficients were calculated between the external wall aragonite and carbonate-depositing fluid. The results are strikingly similar to the values obtained by Sholkovitz and Shen (1995) on coral aragonite, and suggest that there is no significant biologic effect on the incorporation of rare-earth elements into coral aragonite and that the various carbonate complexes involved Me(CO{sub 3}{sup +}) complexes are the main LREE carriers in seawater instead of Me(CO{sub 3}){sub 2}{sup {minus}} in Banza fluids have the same behavior during aragonite precipitation.

Barrat, J.A.; Boulegue, J.; Tiercelin, J.J.; Lesourd, M.

2000-01-01

16

Geochemistry of the rare-earth elements and uranium in the acidic Berkeley Pit lake, Butte, Montana  

Microsoft Academic Search

Filtered (0.45 ?m) and nonfiltered concentrations of rare-earth elements (REE), U, Zr, Th, Ba, Sc, and Y were measured as a function of depth in the Berkeley Pit lake, a large acidic mining lake in Butte, MT. The REE show very little variation with depth, apart from a slight concentration near the surface, presumably due to evaporation. The REE profiles

Christopher H. Gammons; Scott A. Wood; James P. Jonas; James P. Madison

2003-01-01

17

Geochemistry of alkaline earth elements (Mg, Ca, Sr, Ba) in the surface sediments of the Yellow Sea  

Microsoft Academic Search

The concentrations of alkaline earth elements were measured in the surface sediments of the Yellow Sea in an attempt to establish their sources from horizontal distributions. The maximum concentrations of Mg are found in the central Yellow Sea, and its horizontal distribution is mainly controlled by quartz dilution. The concentrations of Ca and Sr increase toward the southeastern Yellow Sea

Guebuem Kim; Han-Soeb Yang; Thomas M. Church

1999-01-01

18

Rare earth element mineralogy, geochemistry, and preliminary resource assessment of the Khanneshin carbonatite complex, Helmand Province, Afghanistan  

USGS Publications Warehouse

There is increased concern about the future availability of rare earth elements (REE) because of China's dominance as the supplier of more than 95 percent of world REE output, their decision to restrict exports of rare earth products, and the rapid increase in world-wide consumption of rare earth product. As a result, countries such as the United States, Japan, and member nations of the European Union face a future of tight supplies and high prices for rare earth products unless other sources of REE are found and developed (Long and others, 2010; U.S. Geological Survey, 2011, p. 128-129, 184-185). We report and describe a significant new deposit of light rare earth elements (LREE), estimated at 1 Mt, within the Khanneshin carbonatite complex of south Afghanistan. The potential resource is located in a remote and rugged part of the igneous complex in a region previously identified by Soviet geologists in the 1970s. This report reviews the geologic setting of LREE deposit, presents new geochemical data documenting the grade of LREE mineralization, briefly describes the mineralogy and mineralogical associations of the deposit, and presents a preliminary estimate of LREE resources based on our current understanding of the geology.

Tucker, Robert D.; Belkin, Harvey E.; Schulz, Klaus J.; Peters, Stephen G.; Buttleman, Kim P.

2011-01-01

19

Rare-earth element geochemistry of Colour Lake, an acidic freshwater lake on Axel Heiberg Island, Northwest Territories, Canada  

Microsoft Academic Search

A lake column profile was collected in 24 m of water from Colour Lake, Axel Heiberg Island, Northwest Territories, Canada, in early June of 1991 beneath 1.8 m of lake-ice. The rare-earth element (REE) concentrations of the acidic, fresh waters of Colour Lake were analyzed, along with the major solute chemistry, in order to investigate REE distribution and speciation in

Kevin H. Johannesson; W. Berry Lyons

1995-01-01

20

Strontium isotopes and rare-earth element geochemistry of hydrothermal carbonate deposits from Lake Tanganyika, East Africa  

Microsoft Academic Search

At Cape Banza (North Tanganyika Lake), fluids and aragonite chimneys have been collected many times since the discovery of this sublacustrine field in 1987. This sampling has been investigated here for the Sr isotopic compositions and the rare-earth element features of the carbonates and a few fluid samples. The 87Sr\\/86Sr ratios of the chimneys indicate that they have precipitated from

J. A. Barrat; J. Boulègue; J. J. Tiercelin; M. Lesourd

2000-01-01

21

Rare-earth element geochemistry of banded iron formations and associated amphibolite from the Sargur belts, south India  

Microsoft Academic Search

Major and rare-earth elements (REE) of banded iron formations (BIFs) and associated amphibolite from the Sargur belts, the oldest schist belts in the Dharwar craton, were determined by X-ray fluorescence and inductively coupled plasma mass spectrometry (ICP-MS). The chondrite-normalized REE patterns of BIFs are light REE-enriched with a striking positive Eu anomaly, resembling those of modern hydrothermal solutions from the

Yasuhiro Kato; Takanori Kawakami; Takashi Kano; Keitaro Kunugiza; N. S. Swamy

1996-01-01

22

The major, trace and rare earth element geochemistry of glauconites from the early Cretaceous Kurnub Group of Jordan  

Microsoft Academic Search

The major, trace and REE geochemistry of glauconites (as members of the trioctahedral micas) from the early Cretaceous Kurnub Group of Jordan are discussed. The investigated glauconites, with 7.1 to 9.2% K2O, are ranked as evolved to highly evolved as defined by Odin and Matter (1981). Al 2O3 contents show a significant inverse relationship with K 2O and Fe2O3. The

GHALEB JARRAR; BELAL AMIREH; DIETER ZACHMANN

23

The Medical Geochemistry of Dusts, Soils, and Other Earth Materials  

NASA Astrophysics Data System (ADS)

"Town clenched in suffocating grip of asbestos"USA Today, article on Libby,Montana, February, 2000"Researchers find volcanoes are bad for your health… long after they finish erupting"University of WarwickPress Release, 1999"Toxic soils plague city - arsenic, lead in 5 neighborhoods could imperil 17,000 residents"Denver Post, 2002"Ill winds - dust storms ferry toxic agents between countries and even continents"Science News, 2002A quick scan of newspapers, television, science magazines, or the internet on any given day has a fairly high likelihood of encountering a story (usually accompanied by a creative headline such as those above) regarding human health concerns linked to dusts, soils, or other earth materials. Many such concerns have been recognized and studied for decades, but new concerns arise regularly.Earth scientists have played significant roles in helping the medical community understand some important links between earth materials and human health, such as the role of asbestos mineralogy in disease (Skinner et al., 1988; Ross, 1999; Holland and Smith, 2001), and the role of dusts generated by the 1994 Northridge, California, earthquake in an outbreak of Valley Fever ( Jibson et al., 1998; Schneider et al., 1997).Earth science activities tied to health issues are growing (Skinner and Berger, 2003), and are commonly classified under the emerging discipline of medical geology (Finkelman et al., 2001; Selinus and Frank, 2000; Selinus, in press).Medical geochemistry (also referred to as environmental geochemistry and health: Smith and Huyck (1999), Appleton et al. (1996)) can be considered as a diverse subdiscipline of medical geology that deals with human and animal health in the context of the Earth's geochemical cycle ( Figure 1). Many medical geochemistry studies have focused on how chemical elements in rocks, soils, and sediments are transmitted via water or vegetation into the food chain, and how regional geochemical variations can result in disease clusters either through dietary deficiency of essential elements or dietary excess of toxic elements. (28K)Figure 1. Potential human exposure routes within the earth's geochemical cycle can come from a wide variety of both natural and anthropogenic sources. This chapter focuses on a somewhat narrower area of medical geochemistry: the study of mechanisms of uptake of earth materials by humans and animals and their reactions to these materials. In order for earth materials to affect health, they must first interact with the body across key interfaces such as the respiratory tract, gastrointestinal tract, skin, and eyes. In some way, all of these interfaces require the earth materials to interact chemically with water-based body fluids such as lung fluids, gastrointestinal fluids, saliva, or blood plasma.The primary goal of this chapter, co-authored by a geochemist and a toxicologist, is to provide both geochemists and scientists from health disciplines with an overview of the potential geochemical mechanisms by which earth materials can influence human health. It is clear that significant opportunities for advancement in this arena will require continued and increased research collaborations between geochemists and their counterparts in the health disciplines.

Plumlee, G. S.; Ziegler, T. L.

2003-12-01

24

Global Oceanic Basalt Geochemistry From EarthChem Databases  

NASA Astrophysics Data System (ADS)

For the past 21 years, global trace element systematics in oceanic basalts have been systematically developed, using mass spectrometry, by the MPI geochemistry department in Mainz, starting with Ba-Rb-Cs, and continuing with K-U-Th, Nb-U-Th, Pb-Ce, Pr-Mo, Nb-Ta, Sn-REE, Sb-REE, and Y-Ho relations. These were complemented by other groups, contributing e.g. Sr-REE relationships and more refined Nb-Ta systematics. Goal of these investigations was to establish relative trace element compatibilities during mantle melting, the corresponding enrichment and depletion patterns in MORB, OIB, subduction-related volcanics and the continental crust, and the relationships to Bulk Silicate Earth abundances through comparisons with element abundances in meteorites and in the continental crust (see e.g. [1]). Most of these studies were initially based on extremely limited data sets, often fewer than 100 analyses, because routine analytical techniques such as XRF and INAA were inadequate, either in sensitivity or accuracy or both, for many of the elements of interest. The advent of ICPMS technology has increased the volume of available, useable data enormously. The most recent development of laser source ICPMS is accelerating the acquisition of comprehensive trace element data even more dramatically. Although the general quality of recent trace element analyses has improved significantly, there remain large differences in reliability between published data because of varying analytical uncertainties and sample alteration. Thus, quality assurance remains an enormous task. In any case, now and in the foreseeable future, it will be impossible to assess global geochemical data without the use of comprehensive databases. Such databases are now available under http://www.earthchem.org/, comprising http://beta.petdb.ciesin.columbia.edu/; http://georoc.mpch-mainz.gwdg.de/, and http://navdat.geo.ku.edu/ . Unfortunately, the use of such databases is not without pitfalls. Often, appropriate metadata are inadequate or absent, and a significant fraction of the primary data and metadata contain errors, either in the original publication or in the transfer to the database. Therefore, analysis of these databases must be performed by experienced geochemists, who are best qualified to recognize erroneous or low-quality data. Even so, elimination of such erroneous or poor data frequently requires subjective judgment. Such evaluations should then produce "expert data sets", which can subsequently be used by non-experts, including non-specialist geochemists, geophysicists, and geologists. A partial expert evaluation of global MORB geochemistry has been prepared by Su [2], who gives segment-by-segment MORB averages. We are preparing an expert data set for global trace element and isotope geochemistry of ocean island basalts. On the basis of these data, we reevaluate global compatibility relationships. At this stage, these relationships are remarkably similar to those summarized by Hofmann [3], and by Sun and McDonough [4], using extremely limited data. This validates the original methodology used by these authors. At the same time, basalt suites containing geochemical anomalies can now be more clearly delineated. Thus, EarthChem databases allow us to develop a comprehensive view of global chemical differentiation of the Earth. [1] Hofmann, A.W. (2003) in Treatise on Geochemistry, ed. R.W. Carlson, Vol.2, 61-101. [2] Su,, Y.J. (2002) PhD Thesis, Columbia University, 472p. [3] Hofmann, A.W. (1988) Earth Planet. Sci. Lett. 90, 297-314. [4] Sun, S.-S. & McDonough, W.F. (1989) Geol. Soc. Spec. Publ. 42 (eds. A.D. Saunders & M.J. Norry), 313-345.

Hofmann, A. W.; Sarbas, B.; Jochum, K. P.; Stracke, A.

2004-12-01

25

Geochemistry.  

ERIC Educational Resources Information Center

Techniques in geochemistry continue to improve in sensitivity and scope. The exciting areas of geochemistry still include the classical fields of the origin of the elements and objects in space, but environmental crisis problems are important as well. (Author/BB)

Fyfe, William S.

1979-01-01

26

The aqueous geochemistry of the rare earth elements and yttrium. Part 7. REE, Th and U contents in thermal springs associated with the Idaho batholith  

Microsoft Academic Search

Concentrations of the rare earth elements (REE), Th and U have been determined in thermal waters emerging from a number of locations in and around the Idaho Batholith. Previous investigators have suggested that the source of heat for the geothermal systems studied is the radioactive decay of K, Th and U which are enriched in the rocks through which the

Paul E. van Middlesworth; Scott A. Wood

1998-01-01

27

Trace element geochemistry of Archean volcanic rocks  

NASA Technical Reports Server (NTRS)

The K, Rb, Sr, Ba and rare-earth-element contents of some Archean volcanic rocks from the Vermilion greenstone belt, northeast Minnesota, were determined by the isotopic dilution method. The characteristics of trace element abundances, supported by the field occurrences and major element chemistry, suggest that these volcanic rocks were formed in an ancient island arc system.

Jahn, B.-M.; Shih, C.-Y.; Murthy, V. R.

1974-01-01

28

Geochemistry of the Solid Earth I: The Mantle and Core  

NSDL National Science Digital Library

This site is a chapter from a book on geochemistry by Dr. W. M. White that is used in a geochemistry course at Cornell University. The 39-page PDF document discusses the composition and evolution of the mantle and core of the earth, and the geochemical methods used to make these determinations. Additional topics include phase transitions, the primitive mantle, differentiation of the mantle, mantle geochemical reservoirs, and evolution of the depleted upper mantle and mantle plume reservoirs. Problems and figures accompany the text.

White, William M.; Department Of Earth And Atmospheric Science, Cornell U.

29

Shallow water redox conditions from Permian-Triassic boundary microbialites: The rare earth element and iodine geochemistry of carbonates from Turkey and South China  

NASA Astrophysics Data System (ADS)

Rare earths and yittrium (REY), iodine, and major elements are determined in two carbonate sections spanning the Permian-Triassic transition in Demirtas, Turkey and Cili, South China. We use major oxides to measure contamination associated with siliciclastics, Fe-oxides, and phosphates. Additionally, we employ Y/Ho ratio, La anomaly, and light rare earth element depletion to identify which samples preserve a seawater-like REY distribution. Despite siliciclastic input, we find the Permian-Triassic boundary microbialites in both sections contain a negative Ce anomaly (average Pr/Pr*=1.07) indicative of deposition in an oxic environment. These boundary microbialites have their base at the extinction horizon and are widespread within the Tethyan region. In the Cili section, the underlying Permian limestone also preserves a seawater-like REY signature with a negative Ce anomaly indicating that the water column was oxygenated both before and after the extinction event. The Permian limestone in the Demirtas section does not preserve a seawater-like REY distribution, so the absence of a Ce anomaly cannot be used to distinguish prevailing redox conditions during deposition. However, in these samples, we find the presence of a diverse Permian benthic community sufficient to identify deposition in an oxic environment. The geochemical evidence for a continuously oxic environment during the deposition of the boundary microbialite presented in this study strongly supports work done using ostracods as redox indicators within the boundary microbialite in South China. These microbialites have been proposed as a disaster facies caused by the exclusion of grazers. Although anoxia is one of the suggested mechanisms for the exclusion of grazers, we find that it is not supported by geochemical evidence.

Loope, G.; Kump, L.

2012-12-01

30

Fluid inclusion, rare earth element geochemistry, and isotopic characteristics of the eastern ore zone of the Baiyangping polymetallic Ore district, northwestern Yunnan Province, China  

NASA Astrophysics Data System (ADS)

The Baiyangping Cu-Ag polymetallic ore district is located in the northern part of the Lanping-Simao foreland fold belt, which lies between the Jinshajiang-Ailaoshan and Lancangjiang faults in western Yunnan Province, China. The source of ore-forming fluids and materials within the eastern ore zone were investigated using fluid inclusion, rare earth element (REE), and isotopic (C, O, and S) analyses undertaken on sulfides, gangue minerals, wall rocks, and ores formed during the hydrothermal stage of mineralization. These analyses indicate: (1) The presence of five types of fluid inclusion, which contain various combinations of liquid (l) and vapor (v) phases at room temperature: (a) H2O (l), (b) H2O (l) + H2O (v), (c) H2O (v), (d) CmHn (v), and (e) H2O (l) + CO2 (l), sometimes with CO2 (v). These inclusions have salinities of 1.4-19.9 wt.% NaCl equivalents, with two modes at approximately 5-10 and 16-21 wt.% NaCl equivalent, and homogenization temperatures between 101 °C and 295 °C. Five components were identified in fluid inclusions using Raman microspectrometry: H2O, dolomite, calcite, CH4, and N2. (2) Calcite, dolomitized limestone, and dolomite contain total REE concentrations of 3.10-38.93 ppm, whereas wall rocks and ores contain REE concentrations of 1.21-196 ppm. Dolomitized limestone, dolomite, wall rock, and ore samples have similar chondrite-normalized REE patterns, with ores in the Huachangshan, Xiaquwu, and Dongzhiyan ore blocks having large negative ?Ce and ?Eu anomalies, which may be indicative of a change in redox conditions during fluid ascent, migration, and/or cooling. (3) ?34S values for sphalerite, galena, pyrite, and tetrahedrite sulfide samples range from -7.3‰ to 2.1‰, a wide range that indicates multiple sulfur sources. The basin contains numerous sources of S, and deriving S from a mixture of these sources could have yielded these near-zero values, either by mixing of S from different sources, or by changes in the geological conditions of seawater sulfate reduction to sulfur. (4) The C-O isotopic analyses yield ?13C values from ca. zero to -10‰, and a wider range of ?18O values from ca. +6 to +24‰, suggestive of mixing between mantle-derived magma and marine carbonate sources during the evolution of ore-forming fluids, although potential contributions from organic carbon and basinal brine sources should also be considered. These data indicate that ore-forming fluids were derived from a mixture of organism, basinal brine, and mantle-derived magma sources, and as such, the eastern ore zone of the Baiyangping polymetallic ore deposit should be classified as a “Lanping-type” ore deposit.

Feng, Caixia; Bi, Xianwu; Liu, Shen; Hu, Ruizhong

2014-05-01

31

Geochemistry  

ERIC Educational Resources Information Center

Enumerates some of the research findings in geochemistry during the last year, including X-ray analysis of the Mars surface, trace analysis of fresh and esterarine waters, and analysis of marine sedements. (MLH)

Ailin-Pyzik, Iris B.; Sommer, Sheldon E.

1977-01-01

32

EarthChem: International Collaboration for Solid Earth Geochemistry in Geoinformatics  

NASA Astrophysics Data System (ADS)

The current on-line information systems for igneous rock geochemistry - PetDB, GEOROC, and NAVDAT - convincingly demonstrate the value of rigorous scientific data management of geochemical data for research and education. The next generation of hypothesis formulation and testing can be vastly facilitated by enhancing these electronic resources through integration of available datasets, expansion of data coverage in location, time, and tectonic setting, timely updates with new data, and through intuitive and efficient access and data analysis tools for the broader geosciences community. PetDB, GEOROC, and NAVDAT have therefore formed the EarthChem consortium (www.earthchem.org) as a international collaborative effort to address these needs and serve the larger earth science community by facilitating the compilation, communication, serving, and visualization of geochemical data, and their integration with other geological, geochronological, geophysical, and geodetic information to maximize their scientific application. We report on the status of and future plans for EarthChem activities. EarthChem's development plan includes: (1) expanding the functionality of the web portal to become a `one-stop shop for geochemical data' with search capability across databases, standardized and integrated data output, generally applicable tools for data quality assessment, and data analysis/visualization including plotting methods and an information-rich map interface; and (2) expanding data holdings by generating new datasets as identified and prioritized through community outreach, and facilitating data contributions from the community by offering web-based data submission capability and technical assistance for design, implementation, and population of new databases and their integration with all EarthChem data holdings. Such federated databases and datasets will retain their identity within the EarthChem system. We also plan on working with publishers to ease the assimilation of geochemical data into the EarthChem database. As a community resource, EarthChem will address user concerns and respond to broad scientific and educational needs. EarthChem will hold yearly workshops, town hall meetings, and/or exhibits at major meetings. The group has established a two-tier committee structure to help ease the communication and coordination of database and IT issues between existing data management projects, and to receive feedback and support from individuals and groups from the larger geosciences community.

Walker, J. D.; Lehnert, K. A.; Hofmann, A. W.; Sarbas, B.; Carlson, R. W.

2005-12-01

33

Tracking Iceland Plume Motion Using Trace Element Geochemistry  

NASA Astrophysics Data System (ADS)

The Greenland-Scotland Ridge (GSR) is a hotspot track built by interaction between the Mid Atlantic Ridge (MAR) and the Iceland mantle plume. Unlike most other hotspot tracks built by ridge-plume interaction, the GSR is 2 to 3 times wider than the plume conduit in the upper mantle. (This unusual wide morphology arises because Icelandic crust changes significantly in thickness within a few million years of accretion, probably mainly by viscous flow in the hot lower crust). The upshot is that the GSR cannot be compared directly with theoretical plume tracks from hotspot reference frame models. However, it is possible to track the position of the Iceland plume conduit using the trace element geochemistry of basaltic lavas. Away from the plume conduit, plate spreading drives upwelling of mantle through the melting region. Above the plume conduit, plume-driven flow forces mantle through the lower part of the melting region faster than the plate-driven upwelling rate. The average depth of melting is therefore greater directly above the plume conduit than away from the plume conduit, and this difference in average melting depth means that melts generated directly above the plume conduit are relatively enriched in incompatible trace elements. Joint modelling of trace element compositions and crustal thickness can also be used to establish location of melting relative to the plume conduit. To date, these concepts have been used only to explain compositional variations in modern (post-glacial) Icelandic lavas; in this study we show that the same concepts can be applied to map the location of the plume conduit throughout the onshore Icelandic geological record (since the middle Miocene, c. 16 Ma). The plume track thus determined is in reasonable agreement with theoretical tracks calculated under the assumption that the Iceland Plume has remained fixed relative to other Indo-Atlantic hotspots. This result also supports the idea that episodic relocations of the onshore part of the MAR act to maintain the spreading axis above the plume conduit.

Fitton, J. G.; Walters, R. L.; Jones, S. M.

2011-12-01

34

Core-Mantle Partitioning of Volatile Elements and the Origin of Volatile Elements in Earth and Moon  

NASA Technical Reports Server (NTRS)

Depletions of siderophile elements in mantles have placed constraints on the conditions on core segregation and differentiation in bodies such as Earth, Earth's Moon, Mars, and asteroid 4 Vesta. Among the siderophile elements there are a sub-set that are also volatile (volatile siderophile elements or VSE; Ga, Ge, In, As, Sb, Sn, Bi, Zn, Cu, Cd), and thus can help to constrain the origin of volatile elements in these bodies, and in particular the Earth and Moon. One of the fundamental observations of the geochemistry of the Moon is the overall depletion of volatile elements relative to the Earth, but a satisfactory explanation has remained elusive. Hypotheses for Earth include addition during accretion and core formation and mobilized into the metallic core, multiple stage origin, or addition after the core formed. Any explanation for volatile elements in the Earth's mantle must also be linked to an explanation of these elements in the lunar mantle. New metal-silicate partitioning data will be applied to the origin of volatile elements in both the Earth and Moon, and will evaluate theories for exogenous versus endogenous origin of volatile elements.

Righter, K.; Pando, K.; Danielson, L.; Nickodem, K.

2014-01-01

35

Rare Earth Elements: End Use and Recycability.  

National Technical Information Service (NTIS)

Rare earth elements are used in mature markets (such as catalysts, glassmaking, lighting, and metallurgy), which account for 59 percent of the total worldwide consumption of rare earth elements, and in newer, high-growth markets (such as battery alloys, c...

T. G. Goonan

2011-01-01

36

Rare earth, major and trace elements in Jurassic manganese shales of the Northern Calcareous Alps: hydrothermal versus hydrogenous origin of stratiform manganese deposits  

Microsoft Academic Search

Summary  ¶The rare earth, major and trace element geochemistry of Jurassic deep marine manganese shales allow insight into their environment\\u000a of deposition. We present data of 24 samples from the Northern Calcareous Alps (Eastern Alps), collected from Late Jurassic\\u000a strata of the Tennengebirge and from Early Jurassic strata of the Karwendel Mts. Whereas major and trace element geochemistry\\u000a is controlled by

G. Rantitsch; F. Melcher; Th. Meisel; Th. Rainer

2003-01-01

37

Rare Earth Element Mines, Deposits, and Occurrences  

USGS Publications Warehouse

Data on rare earth (including yttrium) mines, deposits, and occurrences were compiled as part of an effort by the USGS and the University of Arizona Center for Mineral Resources to summarize current knowledge on the supply and demand outlook and related topics for this group of elements. Economic competition and environmental concerns are increasingly constraining the mining and processing of rare earths from the Mountain Pass mine in California. For many years, the deposit at Mountain Pass was the world's dominant source of rare earth elements and the United States was essentially self-sufficient. Starting approximately 10 years ago, the U.S. has become increasingly dependent (> 90 percent of separated rare earths) upon imports from China, now the dominant source of rare earths. A knowledge of the known economic and noneconomic sources of rare earths is basic to evaluating the outlook for rare earth supply and associated issues.

Orris, Greta J.; Grauch, Richard I.

2002-01-01

38

Overview of Rare Earth Element Investigations in Acid Waters of U. S. Geological Survey Abandoned Mine Lands Watersheds  

Microsoft Academic Search

The geochemistry of rare earth element (REE) variations in acid waters is being studied as part of the U. S. Geological Survey Abandoned Mine Lands Initiative in two pilot watersheds, upper Animas, Colorado and Boulder, Montana. The following objectives are under investigation: (1) comparison of acid mine waters and naturally acidic springs, (2) determination of whether the dominant control on

Philip L. Verplanck; D. Kirk Nordstrom; Howard E. Taylor

39

Volatile Element Geochemistry in the Lower Atmosphere of Venus  

NASA Technical Reports Server (NTRS)

We computed equilibrium abundances of volatile element compounds as a function of altitude in Venus lower atmosphere. The elements included are generally found in volcanic gases and sublimates on Earth and may be emitted in volcanic gases on Venus or volatilized from its hot surface. We predict: 1) PbS, Bi2S3, or possibly a Pb-Bi sulfosalt are the radar bright heavy metal frost in the Venusian highlands; 2) It should be possible to determine Venus' age by Pb-Pb dating of PbS condensed in the Venusian highlands, which should be a representative sample of Venusian lead; 3) The gases HBr, PbCl2, PbBr2, As4O6, As4S4, Sb4O6, BiSe, InBr, InCl, Hg, TlCl, TlBr, SeS, Se2-7, HI, I, I2, ZnCl2, and S2O have abundances greater than 0.1 ppbv in our nominal model and may be spectroscopically observable; 4) Cu, Ag, Au, Zn, Cd, Ge, and Sn are approx. 100 % condensed at the 740 K (0 km) level on Venus.

Schaefer, L.; Fegley, B., Jr.

2004-01-01

40

Principles of Geochemistry.  

National Technical Information Service (NTIS)

Contents: Geochemistry, its limitations and functions methods and history of development; Structure and composition of the earth and the earth's crust, including the hydrosphere and atmosphere; Geochemistry of isotopes; The structure and size of atoms and...

V. V. Shcherbina

1977-01-01

41

Rare earth element diffusion in apatite  

Microsoft Academic Search

Diffusion of rare earth elements (REEs) in natural and synthetic fluorapatite has been characterized under anhydrous conditions. Three types of experiments were run. In the first set of experiments, Sm was introduced into the apatite by means of ion implantation, with diffusivities extracted through measurement of the “relaxation” of the implanted profile after diffusion anneals. The second group consisted of

D. J. Cherniak

2000-01-01

42

Trace element geochemistry: New technology for stratigraphic correlations and formation evaluation  

SciTech Connect

New technology based on the trace element chemistry of rocks is being developed as a tool for mapping subsurface formations in oilfields. This technology can be used to map rock formations in areas where traditional techniques are inconclusive. Trace element geochemistry complements and enhances conventional tools such as biostratigraphy, petrology, and log analysis. Applications cover a broad array of topics including stratigraphic correlations, interpretation of well log responses, age dating, and investigations of reservoir rock properties. Current work is focusing on identifying trace element fingerprints that uniquely mark specific subsurface horizons. There is convincing evidence that trace element fingerprints retain their relative stratigraphic position even though the original mineralogy of the rock has been extensively altered. This means that many of the trace elements associated with specific subsurface rock strata remain in place and are simply transferred from the original mineral to a new (alteration product) mineral. The immobility of these elements is an important geochemical feature because virtually all of the rocks encountered in the petroleum industry are altered to some extent. The ability to {open_quotes}see through{close_quotes} alteration events and obtain information about the original rock is a key advantage of trace element geochemistry techniques.

Lord, C.J. [Phillips Petroleum Company, Bartlesville, OK (United States)

1995-09-01

43

Orientations in Geochemistry.  

National Technical Information Service (NTIS)

An effort is made to provide a useful description of the growing field of geochemistry, its scope and potential. The report presents an assessment of current work in geochemistry, analyzes its interrelationships with the other earth and planetary sciences...

1974-01-01

44

Geochemistry of re and trace elements in ferromanganese nodules and their genesis  

Microsoft Academic Search

Trace and RE element geochemistry and genesis have been studied with respect to ferromanganese nodules from the sediments\\u000a of the Pacific, Atlantic and Indian oceans.\\u000a \\u000a \\u000a 1. \\u000a \\u000a \\u000a Geochemical characteristics of major and trace elements The essential composition is Mn and Fe in nodules with 17.88–28.64% of H2O. Besides ?-MnO2 and Fe2O3, there are hydrous Mn and Fe oxides such as Mn(OH)4,

Wang Xianjue; Chen Yuwei; Wu Mingqing

1986-01-01

45

Trace Element Geochemistry of Martian Iddingsite in the Lafayette Meteorite  

NASA Technical Reports Server (NTRS)

The Lafayette meteorite contains abundant iddingsite, a fine-grained intergrowth of smectite clay, ferrihydrite, and ionic salt minerals. Both the meteorite and iddingsite formed on Mars. Samples of iddingsite, olivine, and augite pyroxene were extracted from Lafayette and analyzed for trace elements by instrumental neutron activation. Our results are comparable to independent analyses by electron and ion microbeam methods. Abundances of most elements in the iddingsite do not covary significantly. The iddingsite is extremely rich in Hg, which is probably terrestrial contamination. For the elements Si, Al, Fe, Mn, Ni, Co, and Zn, the composition of the iddingsite is close to a mixture of approximately 50% Lafayette olivine + approximately 40% Lafayette siliceous glass + approximately 1O% water. Concordant behavior among these elements is not compatible with element fractionations between smectite and water, but the hydrous nature and petrographic setting of the iddingsite clearly suggest an aqueous origin. These inferences are both consistent, however, with deposition of the iddingsite originally as a silicate gel, which then crystallized (neoformed) nearly isochemically. The iddingsite contains significantly more magnesium than implied by the model, which may suggest that the altering solutions were rich in Mg(2+).

Treiman, Allan H.; Lindstrom, David J.

1997-01-01

46

The major and minor element geochemistry of Lake Baikal  

Microsoft Academic Search

A comprehensive, joint Soviet-American study of the chemistry of Lake Baikal, the world's deepest (1,632 m) lake, was carried out in July 1988. In this paper, we report the major, minor, and preliminary trace element concentrations for three profiles obtained at or near the deepest and central part of the three major basins of the lake. With the exception of

KELLY KENISON FALKNER; CHRIS I. MEASURES; SARAH E. HERBELIN; JOHN M. EDMOND; RAY F. WEISS

1991-01-01

47

Study on the absorption of rare earth elements by crops.  

National Technical Information Service (NTIS)

In the rare earth products used in agriculture, there are several main kinds of rare earth elements, such as La, Ce, Pr and Nd. Nearly 99% of rare earth oxides has the composition of La, Ce, Pr and Nd. The process of rare earth elements entering into plan...

Y. Zhu J. Chen

1990-01-01

48

Note: Portable rare-earth element analyzer using pyroelectric crystal  

SciTech Connect

We report a portable rare-earth element analyzer with a palm-top size chamber including the electron source of a pyroelectric crystal and the sample stage utilizing cathodoluminescence (CL) phenomenon. The portable rare-earth element analyzer utilizing CL phenomenon is the smallest reported so far. The portable rare-earth element analyzer detected the rare-earth elements Dy, Tb, Er, and Sm of ppm order in zircon, which were not detected by scanning electron microscopy-energy dispersive X-ray spectroscopy analysis. We also performed an elemental mapping of rare-earth elements by capturing a CL image using CCD camera.

Imashuku, Susumu, E-mail: imashuku.susumu.2m@kyoto-u.ac.jp; Fuyuno, Naoto; Hanasaki, Kohei; Kawai, Jun [Department of Materials Science and Engineering, Kyoto University, Sakyo, Kyoto 606-8501 (Japan)] [Department of Materials Science and Engineering, Kyoto University, Sakyo, Kyoto 606-8501 (Japan)

2013-12-15

49

Trace Element Geochemistry of Micaceous Xenoliths From Kimberley  

NASA Astrophysics Data System (ADS)

Whole rock and mineral major and trace element compositions were determined by XRF, electron microprobe and solution- and laser ablation ICP-MS on a modally diverse suite of 15 micaceous xenoliths from the Kimberley kimberlites. The aim was to better define the chemical characteristics of the MARID and "glimmerite" suites of micaceous xenoliths and their relationships to metasomatized peridotites, megacrysts, kimberlites and orangeites. Among the micaceous xenoliths, mineral and WR compositions of the MARIDs (here defined as containing essential K-richterite) are more Fe-rich and Cr-poor than the glimmerites and cpx-glimmerites, with the exception of an evolved cc-ap-glimmerite. WR Mg#s of all but the latter (Mg# = 75) are in the range 86-91, making it very unlikely that these rocks represent liquid compositions. However, mineral trace element concentrations and "anomalies" on normalized diagrams vary depending upon coexisting phases, suggesting that mass balance considerations may be important. We focused on the REE in cpx, which in these samples is the dominant REE reservoir. This reveals higher concentrations and La/Yb in MARID than cpx-glimmerites, which together with isotopic differences between the groups supports previously proposed links between MARIDs and orangeites and between glimmerites and kimberlites, i.e., two distinct metasomatic episodes related to two types of kimberlite magmatism. However, failing a magmatic origin in eclogite source rocks, this scenario fails to account for the more evolved (e.g. Fe-rich) nature of MARID rocks. In contrast, a continuum in REE behavior in a wider suite of mantle materials allows construction of an alternate endmember model for the metasomatic suite beneath Kimberley. In this scenario, chemical and isotopic evolution of a single type of alkaline melt and associated wallrocks is envisaged, as protokimberlitic melts infiltrate the continental thermal boundary layer. The magmatic vein assemblages evolve from Cr-poor megacrysts, through the Granny Smith-glimmerite association to the MARID suite. Wallrocks evolve from the dunite-wehrlite association through diopside- and phlogopite-rich lherzolites (PP) to richterite- bearing assemblages (PKP). Calculated liquid REE patterns of primitive and more evolved liquids are reproduced in erupted kimberlites and evolved carbonate-rich sill kimberlites (e.g., Benfontein) respectively. This model however requires extensive isotopic exchange of the parental magma with old enriched mantle in order to generate the observed Sr, Nd and Pb isotopic compositions of some MARID rocks. Understanding Cretaceous metasomatism in the Kaapvaal craton appears to call for complex hybrid models and detailed study of diverse xenolith types. Initial trace element measurements of primary textured micas in depleted garnet harzburgites suggest no connection of this material to Cretaceous kimberlite or orangeite magmatism, supporting previous arguments for ancient mantle enrichment.

Bell, D. R.; Gregoire, M.; le Roex, A.; Davis, P.

2001-05-01

50

[Geochemical characteristics of rare earth elements on sunflower growing area in the west of Jilin Province].  

PubMed

Soil and plant samples were collected from the sunflower growing area in the west of Jilin province. A variety of ancillary methods were used to determine the soil element content. Then the rare earth elements geochemistry in soil was studied, and the correlation of REEs in this region with other elements and the quality of plant was investigated. The results show that, (1) REE content of the soil in Nong'an is relatively higher to those in Daan and Tongyu. Distribution pattern of rare earth elements in soil for the right tilt of the light rare earth enrichment patterns which is consistent with the national distribution pattern of rare earth elements; (2) REE contents in the three studying areas in the soil are different, and this primarily relates to the soil parent materials; (3) The REEs which positively correlate with soil available potassium are Se, Fe2O3, Ti, P, Mn, Cu, Zn, Cr, Mo, B, F. The protein content of sunflower seeds has a negative correlation with REE. With the exception of Lu, all REEs show a similar correlation. PMID:21922834

Li, Shu-Jie; Dou, Sen; Wang, Li-Min; Liu, Zhao-Shun

2011-07-01

51

Light element geochemistry and spallogenesis in lunar rocks  

NASA Technical Reports Server (NTRS)

Abundance and isotopic compositions are measured for the very volatile elements carbon, nitrogen and sulfur in 11 lunar rocks representing a wide spectrum of textures and compositions. Samples were combusted sequentially at three temperatures in order to remove terrestrial contaminants before melting the lunar rock and liberating lunar volatiles. The combustion results indicate very little terrestrial sulfur contamination, with sulfur contents correlated with the TiO2 contents of the basalts analyzed. Sulfur isotopic compositions are remarkably uniform and similar to the Canon Diablo meteorite standard. Nitrogen levels are found to be no greater than those obtained with procedural blanks, corresponding to abundances less than 0.1 microg/g. Stable nitrogen isotope measurements indicate a spallogenic N-15 production rate of 4.1 x 10 to the -6th microg N-15/g sample/million years, in agreement with previous estimates. No indigenous carbon in excess of procedural blank levels of about 0.7 microg/g is found in lunar basalts. Levels of 1 to 5 microg/g found in highland rocks may derive from meteoritic or terrestrial sources. The average measured spallogenic C-13 production rate is 4.1 x 10 to the -6th microg C-13/g sample/million years.

Des Marais, D. J.

1983-01-01

52

Anthropogenic Cycles of Rare Earth Elements  

NASA Astrophysics Data System (ADS)

This research will develop quantitatively resolved anthropogenic cycles and in-use stocks for the rare earth metals specifically cerium, lanthanum and dysprosium in Japan, China, and the U.S. for the year of 2007. Rare earth elements (REE) is a group of 17 scare metals widely used in a growing number of emerging technologies and have been in high demand for emerging technologies as raw materials during past the three decades. New market participants from newly industrializing countries, primarily China, have had strong impacts on the demand of share. Consequently, the importance to sustain a reliable, steady, uninterrupted supply on global market triggered comprehensive research to recognize and understand the life cycles of rare earths. Moreover, because China plays a dominant role in mining production since 1990, it requires the assessment for the countries, which are almost completely dependent on imports from China with respect to rare earth resources. The study aims to analyze the flows and stocks of rare earth elements individually as elemental form in spite of their natural geological co-occurrence and mixed composition in applications. By applying the method of Material Flow Analysis (MFA) work has been done on evaluating current and historical flows of specific technologically significant materials, for example, copper, zinc, nickel, etc., determining the stocks available in different types of reservoirs (e.g., lithosphere, in-use) and the flows among the reservoirs, developing scenarios of possible futures of metal use, and assessing the environmental and policy implications of the results. Therefore, REE as a new target deserves inclusion because of its potential demand-supply conflict and importance to secure the competitive advantage of technical innovation in future. This work will generate a quantitatively resolved anthropogenic life cycle and in-use stocks for REE for the main target countries for a chosen year, 2007, providing flows and stocks from mining to use to recycling quantifying the cycles for Japan, China and the U.S. as three representative types of consumers and paying attention to aspects of resource sustainability. Being well aware of the stages in the metal life cycle helps the sustainable development and policy making in long term. The goal is to consider REE resource availability, sustainability, and development strategies in the future that can sustain a reliable, steady, uninterrupted REE supply on the global market.

Du, X.; Graedel, T. E.

2009-12-01

53

Tipping elements in the Earth's climate system  

PubMed Central

The term “tipping point” commonly refers to a critical threshold at which a tiny perturbation can qualitatively alter the state or development of a system. Here we introduce the term “tipping element” to describe large-scale components of the Earth system that may pass a tipping point. We critically evaluate potential policy-relevant tipping elements in the climate system under anthropogenic forcing, drawing on the pertinent literature and a recent international workshop to compile a short list, and we assess where their tipping points lie. An expert elicitation is used to help rank their sensitivity to global warming and the uncertainty about the underlying physical mechanisms. Then we explain how, in principle, early warning systems could be established to detect the proximity of some tipping points.

Lenton, Timothy M.; Held, Hermann; Kriegler, Elmar; Hall, Jim W.; Lucht, Wolfgang; Rahmstorf, Stefan; Schellnhuber, Hans Joachim

2008-01-01

54

Normalized rare earth elements in water, sediments, and wine: identifying sources and environmental redox conditions  

USGS Publications Warehouse

The concentrations of the rare earth elements (REE) in surface waters and sediments, when normalized on an element-by-element basis to one of several rock standards and plotted versus atomic number, yield curves that reveal their partitioning between different sediment fractions and the sources of those fractions, for example, between terrestrial-derived lithogenous debris and seawater-derived biogenous detritus and hydrogenous metal oxides. The REE of ancient sediments support their partitioning into these same fractions and further contribute to the identification of the redox geochemistry of the sea water in which the sediments accumulated. The normalized curves of the REE that have been examined in several South American wine varietals can be interpreted to reflect the lithology of the bedrock on which the vines may have been grown, suggesting limited fractionation during soil development.

Piper, David Z.; Bau, Michael

2013-01-01

55

On the occurrence, trace element geochemistry, and crystallization history of zircon from in situ ocean lithosphere  

NASA Astrophysics Data System (ADS)

We characterize the textural and geochemical features of ocean crustal zircon recovered from plagiogranite, evolved gabbro, and metamorphosed ultramafic host-rocks collected along present-day slow and ultraslow spreading mid-ocean ridges (MORs). The geochemistry of 267 zircon grains was measured by sensitive high-resolution ion microprobe-reverse geometry at the USGS-Stanford Ion Microprobe facility. Three types of zircon are recognized based on texture and geochemistry. Most ocean crustal zircons resemble young magmatic zircon from other crustal settings, occurring as pristine, colorless euhedral (Type 1) or subhedral to anhedral (Type 2) grains. In these grains, Hf and most trace elements vary systematically with Ti, typically becoming enriched with falling Ti-in-zircon temperature. Ti-in-zircon temperatures range from 1,040 to 660°C (corrected for a TiO2 ? 0.7, a SiO2 ? 1.0, pressure ? 2 kbar); intra-sample variation is typically ~60-150°C. Decreasing Ti correlates with enrichment in Hf to ~2 wt%, while additional Hf-enrichment occurs at relatively constant temperature. Trends between Ti and U, Y, REE, and Eu/Eu* exhibit a similar inflection, which may denote the onset of eutectic crystallization; the inflection is well-defined by zircons from plagiogranite and implies solidus temperatures of ~680-740°C. A third type of zircon is defined as being porous and colored with chaotic CL zoning, and occurs in ~25% of rock samples studied. These features, along with high measured La, Cl, S, Ca, and Fe, and low (Sm/La)N ratios are suggestive of interaction with aqueous fluids. Non-porous, luminescent CL overgrowth rims on porous grains record uniform temperatures averaging 615 ± 26°C (2SD, n = 7), implying zircon formation below the wet-granite solidus and under water-saturated conditions. Zircon geochemistry reflects, in part, source region; elevated HREE coupled with low U concentrations allow effective discrimination of ~80% of zircon formed at modern MORs from zircon in continental crust. The geochemistry and textural observations reported here serve as an important database for comparison with detrital, xenocrystic, and metamorphosed mafic rock-hosted zircon populations to evaluate provenance.

Grimes, Craig B.; John, Barbara E.; Cheadle, Michael J.; Mazdab, Frank K.; Wooden, Joseph L.; Swapp, Susan; Schwartz, Joshua J.

2009-12-01

56

Rare earth elements in river waters  

NASA Technical Reports Server (NTRS)

To characterize the input to the oceans of rare earth elements (REE) in the dissolved and the suspended loads of rivers, the REE concentrations were measured in samples of Amazon, Indus, Mississippi, Murray-Darling, and Ohio rivers and in samples of smaller rivers that had more distinct drainage basin lithology and water chemistry. It was found that, in the suspended loads of small rivers, the REE pattern was dependent on drainage basin geology, whereas the suspended loads in major rivers had relatively uniform REE patterns and were heavy-REE depleted relative to the North American Shale composite (NASC). The dissolved loads in the five major rivers had marked relative heavy-REE enrichments, relative to the NASC and the suspended material, with the (La/Yb)N ratio of about 0.4 (as compared with the ratio of about 1.9 in suspended loads).

Goldstein, Steven J.; Jacobsen, Stein B.

1988-01-01

57

Elemental Geochemistry of Samples From Fault Segments of the San Andreas Fault Observatory at Depth (SAFOD) Drill Hole  

Microsoft Academic Search

Elemental geochemistry of mudrock samples from phase 2 drilling of the San Andreas Fault Observatory at Depth (SAFOD) is presented from bore hole depths of 3066 m to 3169 m and from 3292 m to 3368 m, which contain a creeping section and main trace of the fault, respectively. In addition to preparation and analysis of whole rock sample, fault

S. N. Tourscher; A. M. Schleicher; B. A. van der Pluijm; L. N. Warr

2006-01-01

58

Rare Earth Elements in Global Aqueous Media  

NASA Astrophysics Data System (ADS)

We are examining the occurrence and abundance of rare earth elements (REE) associated with produced waters from shale gas development, and factors controlling aqueous REE concentrations in geochemical environments, to provide information for: (1) potential recovery of REE as a valuable byproduct, and (2) utilization of unique REE signatures as a risk assessment tool. REE include the lanthanide series of elements - excluding short-lived, radioactive promethium - and yttrium. These elements are critical to a wide variety of high-tech, energy efficient applications such as phosphors, magnets, and batteries. Escalating costs of REE resulting from divergent supply and demand patterns motivates the first goal. The second goal relates to the search for a reliable, naturally occurring tracer to improve understanding of fluid migration and water-rock interactions during hydraulic fracturing and natural gas recovery. We compiled data from 100 studies of REE occurrence and concentrations in groundwaters, ocean waters, river waters, and lake waters. In the groundwater systems documented, total dissolved REE concentrations ranged over eight orders of magnitude; however the average concentrations across the lanthanides varied by less than two orders of magnitude. This leads to exceptional inter-element correlations, with a median correlation coefficient greater than 0.98, implying potential usefulness of REE ratios for groundwater signatures. Reports describing reactions governing REE solubilization were also investigated. We assembled information about important solution chemistries and performed equilibrium modeling using PHREEQC to examine common hypotheses regarding the factors controlling REE compositions. In particular, effects of pH, Eh, and common complexing ligands were evaluated. Produced and connate waters of the Marcellus shale are well characterized for their major chemical elements. There is a dearth of knowledge, however, regarding the occurrence of REE in Marcellus shale brines and in high TDS brines in general. From synthesis of available brine and geological data, we have developed hypotheses about REE occurrence and content of these hypersaline solutions. It is well documented that the REE concentrations of a solution can serve as a signature of the water and changes in this signature represent interactions with fluids of different compositions or changing mineral strata. We will discuss how the unique signatures and reactivity of REE potentially makes these elements uniquely capable tracers of hydrogeologic activity.

Noack, C.; Karamalidis, A.; Dzombak, D. A.

2012-12-01

59

Trace-element geochemistry of coal resource development related to environmental quality and health  

SciTech Connect

This report assesses for decision makers and those involved in coal resource development the environmental and health impacts of trace-element effects arising from significant increases in the use of coal, unless unusual precautions are invoked. Increasing demands for energy and the pressing need for decreased dependence of the United States on imported oil require greater use of coal to meet the nation's energy needs during the next decade. If coal production and consumption are increased at a greatly accelerated rate, concern arises over the release, mobilization, transportation, distribution, and assimilation of certain trace elements, with possible adverse effects on the environment and human health. It is, therefore, important to understand their geochemical pathways from coal and rocks via air, water, and soil to plants, animals, and ultimately humans, and their relation to health and disease. To address this problem, the Panel on Trace Element Geochemistry of Coal Resource Development Related to Health (PECH) was established. Certain assumptions were made by the Panel to highlight the central issues of trace elements and health and to avoid unwarranted duplication of other studies. Based on the charge to the Panel and these assumptions, this report describes the amounts and distribution of trace elements related to the coal source; the various methods of coal extraction, preparation, transportation, and use; and the disposal or recycling of the remaining residues or wastes. The known or projected health effects are discussed at the end of each section.

Not Available

1980-01-01

60

Rare earth elements in synthetic zircon. 1. synthesis, and rare earth element and phosphorus doping  

Microsoft Academic Search

Sedimentary mineral assemblages commonly contain detrital zircon crystals as part of the heavy-mineral fraction. Age spectra determined by U-Pb isotopic analysis of single zircon crystals within a sample may directly image the age composition--but not the chemical composition--of the source region. Rare earth element (REE) abundances have been measured for zircons from a range of common crustal igneous rock types

J. M. Hanchar; R. J. Finch; W. O. Hoskin; E. B. Watson; D. J. Cherniak; A. N. Mariano

2001-01-01

61

Catalog of Mount St. Helens 2004 - 2005 Tephra Samples with Major- and Trace-Element Geochemistry  

USGS Publications Warehouse

This open-file report presents a catalog of information about 135 ash samples along with geochemical analyses of bulk ash, glass and individual mineral grains from tephra deposited as a result of volcanic activity at Mount St. Helens, Washington, from October 1, 2004 until August 15, 2005. This data, in conjunction with that in a companion report on 2004?2007 Mount St. Helens dome samples by Thornber and others (2008a) are presented in support of the contents of the U.S. Geological Survey Professional Paper 1750 (Sherrod and others, ed., 2008). Readers are referred to appropriate chapters in USGS Professional Paper 1750 for detailed narratives of eruptive activity during this time period and for interpretations of sample characteristics and geochemical data presented here. All ash samples reported herein are currently archived at the David A. Johnston Cascades Volcano Observatory in Vancouver, Washington. The Mount St. Helens 2004?2005 Tephra Sample Catalogue along with bulk, glass and mineral geochemistry are tabulated in 6 worksheets of the accompanying Microsoft Excel file, of2008-1131.xls. Samples in all tables are organized by collection date. Table 1 is a detailed catalog of sample information for tephra deposited downwind of Mount St. Helens between October 1, 2004 and August 18, 2005. Table 2 provides major- and trace-element analyses of 8 bulk tephra samples collected throughout that interval. Major-element compositions of 82 groundmass glass fragments, 420 feldspar grains, and 213 mafic (clinopyroxene, amphibole, hypersthene, and olivine) mineral grains from 12 ash samples collected between October 1, 2004 and March 8, 2005 are presented in tables 3 through 5. In addition, trace-element abundances of 198 feldspars from 11 ash samples (same samples as major-element analyses) are provided in table 6. Additional mineral and bulk ash analyses from 2004 and 2005 ash samples are published in chapters 30 (oxide thermometry; Pallister and others, 2008), 32 (amphibole major elements; Thornber and others, 2008b) and 37 (210Pb; 210Pb/226Pa; Reagan and others, 2008) of U.S. Geological Survey Professional Paper 1750 (Sherrod and others, 2008). A brief overview of sample collection methods is given below as an aid to deciphering the tephra sample catalog. This is followed by an explanation of the categories of sample information (column headers) in table 1. A summary of the analytical methods used to obtain the geochemical data in this report introduces the presentation of major- and trace-element geochemistry of Mount St. Helens 2004?2005 tephra samples in tables 2?6. Rhyolite glass standard analyses are reported (Appendix 1) to demonstrate the accuracy and precision of similar glass analyses presented herein.

Rowe, Michael C.; Thornber, Carl R.; Gooding, Daniel J.; Pallister, John S.

2008-01-01

62

Geostationary earth observatories - Key elements of NASA's 'Mission to Planet Earth'  

NASA Technical Reports Server (NTRS)

The scientific rationale, required instrumentation, observatory configuration, and data system of the Geostationary Earth Observatory (GEO) element of NASA's Mission to Planet Earth program are discussed. Physical characteristics of GEO candidate instruments are listed.

Snoddy, William C.; Keller, Vernon W.

1991-01-01

63

Rare earths and other trace elements in Luna 16 soil.  

NASA Technical Reports Server (NTRS)

An analysis has been made of four small samples of material brought to earth by the Luna 16 mission, with the aim to determine rare earths and other trace elements in these samples. The analytical results are tabulated, and the rare earth abundances are compared with the average for chondrites. A comparison is also made with the results of similar analyses of Apollo samples.

Helmke, P. A.; Haskin, L. A.

1972-01-01

64

Rare earth element partition coefficients in zircon\\/melt systems  

Microsoft Academic Search

In principle, rare earth element (REE) concentrations in magmatic zircon crystals can be used to reconstruct growth conditions, provided accurate information is available about the partitioning of REEs between zircon and magma. Over the past twenty-five years, there have been several studies published that used natural and synthetic samples to determine zircon-melt rare earth element (REE) partition coefficients (D's) in

J. M. Hanchar; W. van Westrenen

2006-01-01

65

Geochemistry of trace elements in coals from the Zhuji Mine, Huainan Coalfield, Anhui, China  

USGS Publications Warehouse

The abundances of nine major elements and thirty-eight trace elements in 520 samples of low sulfur coals from the Zhuji Mine, Huainan Coalfield, Anhui, China, were determined. Samples were mainly collected from 10 minable coal seams of 29 boreholes during exploration. The B content in coals shows that the influence of brackish water decreased toward the top of coal seams; marine transgression and regression occurred frequently in the Lower Shihezi Formation. A wide range of elemental abundances is found. Weighted means of Na, K, Fe, P, Be, B, Co, Ni, Cr, Se, Sb, Ba, and Bi abundances in Zhuji coals are higher, and the remainder elements are either lower or equal to the average values of elements in coals of northern China. Compared to the Chinese coals, the Zhuji coals are higher in Na, K, Be, B, Cr, Co, Se, Sn, Sb, and Bi, but lower in Ti, P, Li, V and Zn. The Zhuji coals are lower only in S, P, V and Zn than average U.S. and world coals. Potassium, Mg, Ca, Mn, Sr, As, Se, Sb and light rare earth elements (LREE) had a tendency to be enriched in thicker coal seams, whereas Fe, Ti, P, V, Co, Ni, Y, Mo, Pb and heavy rare earth elements (HREE) were inclined to concentrate in thinner coal seams. The enrichment of some elements in the Shanxi or Upper Shihezi Formations is related to their depositional environments. The elements are classified into three groups based on their stratigraphic distributions from coal seams 3 to 11-2, and the characteristics of each group are discussed. Lateral distributions of selected elements are also investigated. The correlation coefficients of elemental abundances with ash content show that the elements may be classified into four groups related to modes of occurrence of these elements. ?? 2009 Elsevier B.V. All rights reserved.

Sun, R.; Liu, G.; Zheng, L.; Chou, C. -L.

2010-01-01

66

Geochemistry of re and trace elements in ferromanganese nodules and their genesis  

NASA Astrophysics Data System (ADS)

Trace and RE element geochemistry and genesis have been studied with respect to ferromanganese nodules from the sediments of the Pacific, Atlantic and Indian oceans. 1. Geochemical characteristics of major and trace elements The essential composition is Mn and Fe in nodules with 17.88-28.64% of H2O. Besides ?-MnO2 and Fe2O3, there are hydrous Mn and Fe oxides such as Mn(OH)4, Fe(OH)3, MnO2·nH2O and Fe2O3·nH2O in the nodules. Fe and Mn are presented in higher valences such as Fe3+ and Mn4+. The Fe2+ was not found by chemical analysis and EPR in ferromanganese nodules, but Mn2+ was. These nodules contain by weight 1-2 percent of the oxides of nickel (Ni), copper (Cu), and cobalt (Co). The Ba/Sr ratio of the nodules, is usually over 2. It is considered that foraminifera cannot be the material source of the nodule, because foraminifera with calcite structure usually contain a great deat of Sr but almost no Ba.

Xianjue, Wang; Yuwei, Chen; Mingqing, Wu

1986-09-01

67

Trapping of transuranium elements by the earth's magnetic field  

NASA Technical Reports Server (NTRS)

The search for a transuranium element component of cosmic radiation has been carried out in high altitude balloon experiments. The trapping of high Z elements on orbits in the Earth's magnetic field may lead to a sufficient enhancement of the intensity of particle flux to make it possible to detect these elements by satellite experiments. Calculations are presented that predict the behavior of trapped particles as a function of the predicted flux and energy distribution of high Z elements incident on the Earth's magnetic field. Techniques are suggested for the detection of such particles. In addition, the possibility of production of transuranium elements in the recently discovered pulsars are discussed.

Bloom, J. L.; Eastlund, B. J.

1972-01-01

68

Earth, Air, Fire and Water in Our Elements  

ERIC Educational Resources Information Center

The idea that everything is made of the four "elements", earth, air, fire and water, goes back to the ancient Greeks. In this article, the author talks about the origins of ideas about the elements. The author provides an account that attempts to summarise thousands of years of theoretical development of the elements in a thousand words or so.

Lievesley, Tara

2007-01-01

69

Microbial engineering of floc fe and trace element geochemistry in a circumneutral, remote lake.  

PubMed

Evaluation of lacustrine floc Fe, Pb, and Cd biogeochemistry over seasonal (summer, winter) and water column depth (metalimnetic, hypolimnetic) scales reveals depth-independent seasonally significant differences in floc Fe biominerals and trace element (TE: Pb, Cd) sequestration, driven by floc microbial community shifts. Winter floc [TE] were significantly lower than summer [TE], driven by declining abundance and reactivity of floc amorphous Fe((III))-(oxy)hydroxide (FeOOH) phases under ice ([FeOOH](summer) = 37-77 mgg(-1) vs [FeOOH](winter) = 0.3-7 mgg(-1)). Further, while high summer floc [FeOOH] was observed at both water column depths, winter floc was dominated by Fe((II)) phases. However, the observed seasonal change in the nature and concentrations of floc Fe-phases was independent of water column [Fe], O2, and pH and, instead, significantly correlated to floc bacterial community membership. Bioinformatic modeling (Unifrac, PCA analyses) of in situ and experimental microcosm results identified a temperature-driven seasonal turnover of floc microbial communities, shifting from dominantly putative Fe metabolisms within summer floc to wintertime ancillary Fe reducing and S metabolizing bacteria. This seasonal shift of floc microbial community functioning, significantly the wintertime loss of microbial Fe((II))-oxidizing capability and concomitant increases of sulfur-reducing bacteria, alters dominant floc Fe minerals from Fe((III)) to Fe((II)) phases. This resulted in decreased winter floc [TE], not predicted by water column geochemistry. PMID:24810706

Elliott, Amy V C; Warren, Lesley A

2014-06-17

70

Coupled finite element method for the Earth's orientation parameter problems  

NASA Astrophysics Data System (ADS)

We describe the combined approach to the Earth's orientation parameter problems. The approach allows one to couple the finite element method with the solution of the Laplace equation on the basis of iteration procedure. This makes possible to calculate heterogeneties of both geometrical and rheological characters into the Earth's structure. In the framework of this approach, forced nutation of the simplified dynamical Earth's model is determined and a comparison with the corresponding results of Molodensky and Wahr is carried out.

Lubkov, M. V.

2005-10-01

71

Rare earth element diffusion in apatite  

NASA Astrophysics Data System (ADS)

Diffusion of rare earth elements (REEs) in natural and synthetic fluorapatite has been characterized under anhydrous conditions. Three types of experiments were run. In the first set of experiments, Sm was introduced into the apatite by means of ion implantation, with diffusivities extracted through measurement of the "relaxation" of the implanted profile after diffusion anneals. The second group consisted of "in diffusion" experiments, in which apatite was immersed in reservoirs of synthetic REE apatite analogs of various compositions. The final set of experiments was "out-diffusion" experiments run on synthetic Nd-doped apatite immersed in a reservoir of synthetic (undoped) fluorapatite. REE depth profiles in all cases were measured with Rutherford Backscattering Spectrometry. Diffusion rates for the REE vary significantly among these sets of experiments. For the ion-implantation experiments, the following Arrhenius relation was obtained for Sm, over the temperature range 750°C to 1100°C: D imp=6.3×10-7exp(-298±17 kJ/mol/RT) m2/s Diffusion of a series of REE, from light to heavy, was investigated in the "in-diffusion" experiments. Over the temperature range 800°C to 1250°C, the following Arrhenius relations are obtained for La, Nd, Dy, and Yb, for in-diffusion experiments using REE silicate oxyapatite sources: D La=2.6×10-7exp(-324±9 kJ/mol/RT) m2/sD Nd=2.4×10-6exp(-348±13 kJ/mol/RT) m2/sD Dy=9.7×10-7exp(-340±11 kJ/mol/RT) m2/sD Yb=1.3×10-8exp(-292±23 kJ/mol/RT) m2/s Diffusivities of the REE in these "in-diffusion" experiments are all quite similar, suggesting little difference in diffusion rates in apatite with increasing ionic radii of the REEs. The "out-diffusion" experiments on the Nd-doped synthetic apatite, over the temperature range 950°C to 1400°C, yield the Arrhenius law: D out=9.3×10-6exp(-392±31 kJ/mol/RT) m2/s The differences in REE diffusion among these three sets of experiments (i.e., ion implantation, in-diffusion, and out-diffusion) may be attributable to the differences in substitutional processes facilitating REE exchange. The fastest diffusion, found in the ion-implantation experiments, is likely largely governed by simple light REE +3 ? REE +3 exchange, with no charge compensating species necessary. REE transport in the in-diffusion experiments requires movement of an additional charge-compensating species, either through the substitutions REE +3 + Si +4 ? Ca +2 + P +5 or REE +3 + Na +1 ? 2 Ca +2, and thus proceeds more slowly than simple REE exchange. Slowest of all is Nd out-diffusion from the synthetic Nd-doped apatite, for which neither charge compensating species are present nor REEs available in the surrounding reservoir to facilitate Nd exchange. This observed dependence of REE diffusion rates on the exchange process involved has important geochemical implications. These findings indicate that REE isotope and chemical signatures can become decoupled in apatite, with light REE isotope exchange proceeding much more rapidly than REE chemical diffusion altering total REE concentrations. Under temperatures typical of thermal events, REE zoning (involving differences in REE concentration across zones) of a given dimension might persist over time periods two orders of magnitude greater than those under which zoning of REE isotopes (without significant changes in total REE) on similar scale is preserved.

Cherniak, D. J.

2000-11-01

72

Experimental geochemistry of Pu and Sm and the thermodynamics of trace element partitioning  

NASA Technical Reports Server (NTRS)

An experimental study of the partitioning of Pu and Sm between diopside/liquid and whitlockite/liquid supports the hypothesis that Pu behaves as a light rare earth element during igneous processes in reducing environments. D-Pu/D-Sm is found to be about 2 for both diopsidic pyroxene and whitlockite, and the amount of fractionation would be decreased further if Pu were compared to Ce or Nd. Data indicate that temperature, rather than melt composition, is the most important control on elemental partitioning, and that P2O5 in aluminosilicate melts serves as a complexing agent for the actinides and lanthanides.

Jones, John H.; Burnett, Donald S.

1987-01-01

73

Trace Element and As Geochemistry of Surface Waters around Mammoth Mountain, CA  

NASA Astrophysics Data System (ADS)

Mammoth Mountain has been studied because of high CO2 emissions since a 1989 earthquake swarm. The current study is part of ongoing research that is investigating the relationship between the elevated CO2 and the mountain's hydrosphere and mineral weathering. This project builds upon previous analyses of major ion chemistry of Mammoth Mountain springs by analyzing the trace element and contaminant geochemistry. Analyses show variations in both trace/minor elements and contaminants. Sr values vary from less than 0.04 to more than 200(?g/L), and are positively correlated to Ca. Sr and Ca have similar chemical behavior and Sr can replace Ca in silicate minerals. Globally, waters draining silicates have low Ca/Na and Sr/Na ratios (Gaillardet et. Al 1999). Molar ratios for the springs in this study plot on a mixing line between the largely felsic silicates known to compose the area around Mammoth Mountain and the more mafic silicates in the Devils Post Pile area. However, the Sr/Na ratio was high, causing the values to shift to the right of Gaillardet's line for global silicate weathering. This may indicate differential mineral weathering but more research is necessary. Arsenic is present in values ranging from less than 0.03 to more than 200(?g/L). The U.S EPA maximum contaminant level for As is 10ppb and six sample locations were above the MCL. A study of Eastern Sierra Nevada rivers shows that possible sources of As are weathering of As-rich rocks, volcanic deposits, and input of high-As geothermal spring waters (Johannesson et al. 1997). In Hot Creek, located in the Owens Valley near Mammoth Mountain, elevated As concentrations have been shown to be the result of geothermal inputs (Hering 1997).

Hunt, K. M.; Ellis, A. S.; Raskin, S.; Khachikian, C.

2012-12-01

74

Volcanism in the Sumisu Rift, I. Major element, volatile, and stable isotope geochemistry  

USGS Publications Warehouse

A bimodal volcanic suite with KAr ages of 0.05-1.40 Ma was collected from the Sumisu Rift using alvin. These rocks are contemporaneous with island arc tholeiite lavas of the Izu-Ogasawara arc 20 km to the east, and provide a present day example of volcanism associated with arc rifting and back-arc basin initiation. Major element geochemistry of the basalts is most similar to that of basalts found in other, more mature back-arc basins, which indicates that back-arc basins need not begin their magmatic evolution with lavas bearing strong arc signatures. Volatile concentrations distinguish Sumisu Rift basalts from island arc basalts and MORB. H2O contents, which are at least four times greater than in MORB, suppress plagioclase crystallization. This suppression results in a more mafic fractionating assemblage, which prevents Al2O3 depletion and delays the initiation of Fe2O3(tot) and TiO2 enrichment. However, unlike arc basalts, Fe3+ ??Fe ratios are only slightly higher than in MORB and are insufficient to cause magnetite saturation early enough to suppress Fe2O3(tot) and TiO2 enrichment. Thus, major element trends are more similar to those of MORB than arcs. H2O, CO2 and S are undersaturated relative to pure phase solubility curves, indicating exsolution of an H2O-rich mixed gas phase. High H2O S, high ??D, and low (MORB-like) ??34S ratios are considered primary and distinctive of the back-arc basin setting. ?? 1990.

Hochstaedter, A. G.; Gill, J. B.; Kusakabe, M.; Newman, S.; Pringle, M.; Taylor, B.; Fryer, P.

1990-01-01

75

Geochemistry of metallic trace elements in fumarolic condensates from Nicaraguan and Costa Rican volcanoes  

NASA Astrophysics Data System (ADS)

Metallic trace-element composition of volcanic gas from Cerro Negro, Momotombo, San Cristóbal, Telica and Masaya volcanoes in Nicaragua and Poás volcano in Costa Rica is indicated by analyses of fumarolic condensates for alkalis, alkaline earths, transition elements, precious metals, halogens and sulphate. The temperatures of the fumaroles varied from 85 to 852°C. Element concentrations range from 10 4 to 10 -3 ppm. Statistical tests indicate that the trace-element constituents of the condensates are log-normally distributed. Although there are variations in element concentrations in individual condensates, the general order of decreasing elemental abundances in Nicaraguan and Costa Rican fumarolic gas is: Cl > SO 4 > certain igneous rock-forming elements (Si, Al, Fe, Ti) > F and alkalis (Li, Na, K) > alkaline earths (Mg, Ca, Ba) > Br and transition elements (Cr, Mn, Co, Ni, Cu, Zn) > other ore-forming elements (Mo, Cd, Sn, Pb) > semi-metals (As, Sb) > Sc, Hg, and precious metals (Au, Ag). Li, Mn, Cr, and Pb were found to be near or below detection limits in many of the condensates analyzed. SO 4, Ti, Al, K, Na, Zn, Sn, Cr, and Br all tend to decrease in abundance as mean fumarolic temperature between volcanoes decreases. The remaining elements remain constant in abundance or behave erratically. The metallic trace-element composition of the Nicaraguan and Costa Rican fumarolic condensates is very similar to condensates from subduction zone volcanoes around the Pacific margin and the Mediterranean. Metals in volcanic gas are postulated to have been transported as halogen, sulphate, and oxide compounds. Chloride and fluoride compounds are considered to be the primary transporters of metals in volcanic gas. Correlations between metal and halogen content vary considerably between volcanoes. Statistically significant correlations between metal content and both chlorine and bromine are found in the Cerro Negro and between metal content and bromine and fluorine in the Momotombo condensates. Metal-bearing compounds in volcanic gas are postulated from correlation matrices. Bromine, though seldom reported in condensates, is a minor but important constituent of volcanic gas with concentrations similar to those of fluorine. Metal-bromide compounds have higher volatilities than fluoride compounds and volatilities similar to chloride compounds. Significant correlations between bromine content and metal concentration suggests that bromide compounds play a role in the transportation of metals in volcanic gas.

Gemmell, J. Bruce

1987-08-01

76

China's Rare Earth Elements Industry: What Can the West Learn.  

National Technical Information Service (NTIS)

China controls approximately 97 percent of the world's rare earth element market. These elements, which are not widely known because they are so low on the production chain, are critical to hundreds of high tech applications, many of which define our mode...

C. Hurst

2010-01-01

77

Inaugural Article: Tipping elements in the Earth's climate system  

Microsoft Academic Search

The term ``tipping point'' commonly refers to a critical threshold at which a tiny perturbation can qualitatively alter the state or development of a system. Here we introduce the term ``tipping element'' to describe large-scale components of the Earth system that may pass a tipping point. We critically evaluate potential policy-relevant tipping elements in the climate system under anthropogenic forcing,

Timothy M. Lenton; Hermann Held; Elmar Kriegler; Jim W. Hall; Wolfgang Lucht; Stefan Rahmstorf; Hans Joachim Schellnhuber

2008-01-01

78

Perturbations in orbital elements of a low earth orbiting satellite  

Microsoft Academic Search

The main point of this paper is to evaluate the perturbations in orbital elements of a low Earth orbiting satellite. The outcome of a numerical orbit integration process is the position and velocity vectors of satellite in an inertial coordinate system. The velocity and position vectors are converted into the corresponding orbital elements. Perturbations in a satellite motion affect the

Najafi Alamdari; Nasir Toosi

79

Countering China's Dominance in the Rare Earth Element Market System.  

National Technical Information Service (NTIS)

This paper will discuss how the United States can exercise the economic element of national power to ensure access to rare earth elements (REE) in a China-dominated market system. Since the 1980 s, China has gained a virtual monopoly in the mining and pro...

E. O. Estep

2012-01-01

80

Systematic variation of rare-earth elements in cerium-earth minerals  

USGS Publications Warehouse

In a continuation of a study reported previously, rare-earth elements and thorium have been determined in monazite, allanite, cerite, bastnaesite, and a number of miscellaneous cerium-earth minerals. A quantity called sigma (???), which is the sum of the atomic percentages of La, Ce, and Pr, is proposed as an index of composition of all cerium-earth minerals with respect to the rare-earth elements. The value of ??? for all of the minerals analysed falls between 58 and 92 atomic per cent. Monazites, allanites, and cerites cover the entire observed range, whereas bastnaesites are sharply restricted to the range between 80 and 92 atomic per cent. The minimum value of ??? for a cerium-earth mineral corresponds to the smallest possible unit-cell size of the mineral. In monazite, this structurally controlled minimum value of ??? is estimated to be around 30 atomic per cent. Neodymium, because of its abundance, and yttrium, because of its small size, have dominant roles in contraction of the structure. In the other direction, the limit of variation in composition will be reached when lanthanum becomes the sole rare-earth element in a cerium-earth mineral. Cerium-earth minerals from alkalic rocks are all characterized by values of ??? greater than 80 atomic per cent, indicating that the processes that formed these rocks were unusually efficient in fractionating the rare-earth elements-efficient in the sense that a highly selected assemblage is produced without eliminating the bulk of these elements. Analyses of inner and outer parts of two large crystals of monazite from different deposits show no difference in ??? in one crystal and a slightly smaller value of ??? in the outer part of the other crystal compared to the inner part. The ??? of monazites from pegmatites that intrude genetically related granitic rocks in North Carolina is found to be either higher or lower than the ??? of monazites in the intruded host rock. These results indicate that the fractionation of the rare-earth elements is not a simple unidirectional process. When a cerium-earth mineral undergoes replacement, its rare-earth elements may be fractionated into two parts, one forming a new mineral with ??? that is smaller, and the other a second new mineral with ??? that is larger than that of the original mineral. The complete analysis of a cerium-earth mineral to determine its ??? is time consuming. The discovery of a direct relationship between ??? and the Ce/(Nd + Y) atomic ratio in cerium earth minerals allows a rapid determination of ??? from spectrograms obtained in a previously described method for determining thorium in these minerals. ?? 1957.

Murata, K. J.; Rose, Jr. , H. J.; Carron, M. K.; Glass, J. J.

1957-01-01

81

Minor-element and Sr-isotope geochemistry of tertiary stocks, Colorado mineral belt  

USGS Publications Warehouse

Rocks of the northeast portion of the Colorado mineral belt form two petrographically, chemically and geographically distinct rock suites: (1) a silica oversaturated granodiorite suite; and (2) a silica saturated, high alkali monzonite suite. Rocks of the granodiorite suite generally have Sr contents less than 1000 ppm, subparallel REE patterns and initial 87Sr/ 86Sr ratios greater than 0.707. Rocks of the monzonite suite are restricted to the northeast part of the mineral belt, where few rocks of the granodiorite suite occur, and generally have Sr contents greater than 1000 ppm, highly variable REE patterns and 87Sr/86Sr initial ratios less than 0.706. Despite forming simple, smooth trends on major element variation diagrams, trace element data for rocks of the granodiorite suite indicate that they were not derived from a single magma. These rocks were derived from magmas having similar REE patterns, but variable Rb and Sr contents, and Rb/Sr ratios. The preferred explanation for these rocks is that they were derived by partial melting of a mixed source, which yielded pyroxene granulite or pyroxenite residues. The monzonite suite is chemically and petrographically more complex than the granodiorite suite. It is subdivided here into alkalic and mafic monzonites, and quartz syenites, based on the textural relations of their ferromagnesian phases and quartz. The geochemistry of these three rock types require derivation from separate and chemically distinct magma types. The preferred explanation for the alkalic monzonites is derivation from a heterogeneous mafic source, leaving a residue dominated by garnet and clinopyroxene. Early crystallization of sphene from these magmas was responsible for the severe depletion of the REE observed in the residual magmas. The lower Sr content and higher Rb/Sr ratios of the mafic monzonites requires a plagioclase-bearing source. The Sr-isotope systematics of the majority of these rocks are interpreted to be largely primary, and not the result of crustal contamination. The positive correlation of Rb/Sr and 87Sr/86Sr ratios for the least fractionated samples indicate that the sources from which parent magmas of both the granodiorite and monzonite suites were derived are Precambrian in age. ?? 1978 Springer-Verlag.

Simmons, E. C.; Hedge, C. E.

1978-01-01

82

Elemental mixing systematics and Sr Nd isotope geochemistry of mélange formation: Obstacles to identification of fluid sources to arc volcanics  

NASA Astrophysics Data System (ADS)

We present major and trace element concentrations in conjunction with Sr-Nd isotope ratios to investigate the geochemical characteristics of mélange formation along the subduction zone slab-mantle interface. Mélange matrix of the Catalina Schist formed within an active subduction zone of the southern California borderland in Cretaceous time. Mélange formed through the synergistic effects of deformation and metasomatic fluid flow affecting peridotite, basaltic, and sedimentary protoliths to form hybridized bulk compositions not typical of seafloor "input" lithologies. In general, all elemental concentrations primarily reflect mechanical mixing processes, while fluid flow mediates all elemental systematics to a varying extent that is largely a function of inferred "mobility" for a particular element or the stability of suitable mineral hosts. Elemental data reveal that mineral stabilities defined by the evolution of bulk composition within mélange zones are probably the most important control of solid, liquid, or fluid geochemistry within the subduction system. Sr-Nd isotope ratios are highly variable and reflect contributions of mélange protoliths to varying extents. A weak mechanical mixing array present in Sr isotope data is strongly overprinted by a fluid signal that dominates mélange Sr systematics. Nd isotope data suggest that Nd is more conservative during metamorphism and is largely controlled by mechanical mixing. We argue that mélange formation is an intrinsic process to all subduction zones and that the geochemistry of mélange will impart the strongest control on the geochemistry of metasomatic agents (hydrous fluids, silicate melts, or miscible supercritical liquids) progressing to arc magmatic source regions in the mantle wedge. Mélange formation processes suggest that comparisons of subduction "inputs" to arc volcanic "outputs" as a means to infer recycling at subduction zones dangerously over-simplify the physics of the mass transfer in subduction zones, as subducted mass is consistently redistributed into novel bulk compositions. Such mélange zones along the slab-mantle interface simultaneously bear characteristic elemental or isotopic signals of several distinct input lithologies, while experiencing phase equilibria not typical of any input. We recommend that future studies explore the phase equilibria of hybridized systems and mineral trace element residency, as these processes provide for a physical baseline from which it will be possible to follow the path of subducted mass through the system.

King, Robert L.; Bebout, Gray E.; Moriguti, Takuya; Nakamura, Eizo

2006-06-01

83

Anthropogenic disturbance of element cycles at the Earth's surface.  

PubMed

The extent to which humans are modifying Earth's surface chemistry can be quantified by comparing total anthropogenic element fluxes with their natural counterparts (Klee and Graedel, 2004). We quantify anthropogenic mass transfer of 77 elements from mining, fossil fuel burning, biomass burning, construction activities, and human apportionment of terrestrial net primary productivity, and compare it to natural mass transfer from terrestrial and marine net primary productivity, riverine dissolved and suspended matter fluxes to the ocean, soil erosion, eolian dust, sea-salt spray, cosmic dust, volcanic emissions, and for helium, hydrodynamic escape from the Earth's atmosphere. We introduce an approach to correct for losses during industrial processing of elements belonging to geochemically coherent groups, and explicitly incorporate uncertainties of element mass fluxes through Monte Carlo simulations. We find that at the Earth's surface anthropogenic fluxes of iridium, osmium, helium, gold, ruthenium, antimony, platinum, palladium, rhenium, rhodium and chromium currently exceed natural fluxes. For these elements mining is the major factor of anthropogenic influence, whereas petroleum burning strongly influences the surficial cycle of rhenium. Our assessment indicates that if anthropogenic contributions to soil erosion and eolian dust are considered, anthropogenic fluxes of up to 62 elements surpass their corresponding natural fluxes. PMID:22803636

Sen, Indra S; Peucker-Ehrenbrink, Bernhard

2012-08-21

84

Rare Earth Element Patterns in Biotite, Muscovite and Tourmaline Minerals.  

National Technical Information Service (NTIS)

Rare earth element concentrations in the minerals biotite and muscovite from the mica schist country rocks of the Etta pegmatite and tourmalines from the Bob Ingersoll pegmatite have been measured by INAA and CNAA. The concentrations range from 10 sup -4 ...

J. C. Laul E. A. Lepel

1986-01-01

85

Geochemistry of rare and minor elements in sediments from Brazil Basin of Atlantic Ocean  

NASA Astrophysics Data System (ADS)

This paper reviews the features of the rare and minor elements in the sediment samples recovered from the Brazil Basin at the location of the Station No. 1537 in the Atlantic Ocean during the 18th cruise of the Research Vessel "Akademik Sergey Vavilov". The depth of the sediment column is 470 cm. The sediments are represented by the oxidized miopelagic clay (0-305 cm) which are underlain by the thin bedded Ethmodiscus diatom oozes (305-470 cm). The brown miopelagic clay (0.09-1.25% ????3, 0.05-0.28% ?organic) predominately consist of the clay minerals (91-97%). The top section sediments also include some terrigenous clastic sandy-silt minerals (1-5%), diatoms (up to 2%), manganese micronodules (approx. 1%), occasional spicules, radiolarian, coccoliths and marine fossil fragments. The transition to the lower diatom oozes is associated with the lens-shape structures and increase in the content of diatoms in clay. The age of sediments at the station No. 1537 is Late Pleistocene. Presence of thin bedded Ethmodiscus oozes is an indirect evidence of re-deposition of the sediments in the central part of the Brazil Basin The chemical composition has been analyzed on 37 core samples recovered from the column. These core samples have been used to define the content of the chemical composition as well as the rare and minor elements. The manganese content in the top section of the miopelagic clay varies insignificantly and value is close 0.46%. The rare and minor elements content in the miopelagic clay is quite stable. The sharp increase in manganese content (to 1.16%) as well as in that of the minor elements such as Co, Cu, Ni, Mo and Tl are observed at the 305-308 cm horizon which corresponds to the bottom of the miopelagic clay. Than, the manganese content decreases to reach its minimum value (0.20%) immediately below this horizon. With further depth increase, the content of manganese starts rising again reaces its maximum value of 2.31% at the 405-407 cm horizon. The diatom oozes, compared with the clayey silts, contain higher concentrations of Co, Cu, Ni, Mo, Tl. The content of other minor elements is considerably lower than that of the clayey silts. Comparison of the average chemical element contents in miopelagic clay and diatom oozes gives a series sequence of abundance of minor elements: Ag Mo Tl Mn Cd Ba Co Ni Cu Sr Pb Li Ce Zn V 0.2 0.4 0.5 0.5 0.6 1.2 1.3 1.5 1.7 1.8 2.1 2.1 2.1 2.1 2.3 REE Y U W Th Be Rb Cs As 2.3-2.1 2.3 2.4 2.4 2.4 2.4 2.4 2.5 3.5 The miopelagic muds contains high concentrations are reached in three groups of elements: easily hydrolyze elements (REE, Y, Th, Be), elements represented by oxyanions in the ocean water (U, W, V, As) and elements linked with the clays (Li, Rb, Cs). The concentrations of rare earth elements (REE) in miopelagic muds show almost no change with depth. The compositions of REE include cerium anomaly and light lanthanides. The composition of REE in diatom oozes is more variable. The oozes also include cerium anomaly, but sometimes concentrations of lighter elements are low.

Vvedenskaya, Irina; Dubinin, Alexander

2010-05-01

86

Trace element and isotope geochemistry of geothermal fluids, East Rift Zone, Kilauea, Hawaii  

NASA Astrophysics Data System (ADS)

A research program has been undertaken in an effort to better characterize the composition and the precipitation characteristic of the geothermal fluids produced by the HGP-A geothermal well located on the Kilauea East Rift Zone on the island of Hawaii. The results of these studies have shown that the chemical composition of the fluids changed over the production life of the well and that the fluids produced were the result of the mixing of at least two, and possibly three, source fluids. These source fluids were recognized as a sea water composition modified by high temperature water-rock reactions; meteoric recharge; and a hydrothermal fluid that had been equilibriated with high temperature reservoir rocks and magmatic volatiles. Although the major alkali and halide elements show clearly increasing trends with time, only a few of the trace transition metals show a similar trend. The rare earth elements were typically found at low concentrations and appeared to be highly variable with time. Studies of the precipitation characteristics of silica showed that amorphous silica deposition rates were highly sensitive to fluid pH and that increases in fluid pH above about 8.5 could flocculate more than 80 percent of the suspended colloidal silica in excess of its solubility. Addition of transition metal salts were also found to enhance the recovery fractions of silica from solution. The amorphous silica precipitate was also found to strongly scavenge the alkaline earth and transition metal ions naturally present in the brines; mild acid treatments were shown to be capable of removing substantial fractions of the scavenged metals from the silica flocs, yielding a moderately pure gelatinous by-product. Further work on the silica precipitation process is recommended to improve our ability to control silica scaling from high temperature geothermal fluids or to recover a marketable silica by-product from these fluids prior to reinjection.

West, H. B.; Delanoy, G. A.; Thomas, D. M.; Gerlach, D. C.; Chen, B.; Takahashi, P.; Thomas, D. M.

1992-03-01

87

Trace element geochemistry of groundwater in a karst subterranean estuary (Yucatan Peninsula, Mexico)  

NASA Astrophysics Data System (ADS)

Trace element cycling within subterranean estuaries frequently alters the chemical signature of groundwater and may ultimately control the total chemical load to the coastal ocean associated with submarine groundwater discharge. Globally, karst landscapes occur over 12% of all coastlines. Subterranean estuaries in these regions are highly permeable, resulting in rapid infiltration of precipitation and transport of groundwater to the coast, and the predominant carbonate minerals are readily soluble. We studied the chemical cycling of barium (Ba), strontium (Sr), manganese (Mn), uranium (U), calcium (Ca) and radium (Ra) within the carbonate karst subterranean estuary of the Yucatan Peninsula, which is characterized by a terrestrial groundwater lens overlying marine groundwater intrusion with active submarine discharge through coastal springs. Terrestrial groundwater calcium (1-5 mmol kg-1) and alkalinity (3-8 mmol kg-1) are enriched over that predicted by equilibrium between recharging precipitation and calcite, which can be accounted for by groundwater organic matter respiration and subsequent dissolution of calcite, dolomite and gypsum. There is a close agreement between the observed terrestrial groundwater Sr/Ca, Mn/Ca, Ba/Ca and Ra/Ca and that predicted by equilibrium dissolution of calcite, thus the trace element content of terrestrial groundwater is largely determined by mineral dissolution. Subsequent mixing between terrestrial groundwater and the ocean within the actively discharging springs is characterized by conservative mixing of Sr, Mn, Ba and Ca, while U is variable and Ra displays a large enrichment (salinity: 1.9-34.9, Ba: 60-300 nmol kg-1, Sr: 15-110 ?mol kg-1, U: 0.3-35 nmol kg-1, Mn: 0.3-200 nmol kg-1, Ca: 4.3-12.9 mmol kg-1, 226Ra: 18-2140 dpm 100 L-1). The deep groundwater sampled through cenotes, local dissolution features, is typified by elevated Ba, Sr, Ca, Mn and Ra and the absence of U within marine groundwater, due to enhanced dissolution of the aquifer matrix following organic matter degradation and redox processes including sulfate reduction (salinity: 0.2-36.6, Ba: 7-1630 nmol kg-1, Sr: 1.3-210 ?mol kg-1, U: 0.3-18 nmol kg-1, Mn: 0.6-2600 nmol kg-1, Ca: 2.1-15.2 mmol kg-1, 226Ra 20-5120 dpm 100 L-1). However, there is no evidence in the spring geochemistry that deep marine groundwater within this reaction zone exchanges with the coastal ocean via spring discharge. Total submarine groundwater discharge rates calculated from radium tracers are 40-95 m3 m-1 d-1, with terrestrial discharge contributing 75 ± 25% of the total. Global estimates of chemical loading from karst subterranean estuaries suggest Sr and U fluxes are potentially 15-28% and 7-33% of total ocean inputs (8.2-15.3 mol y-1 and 4.0-7.7 mol y-1), respectively. Radium-226 inputs from karst subterranean estuaries are 34-50 times river inputs (6.7-9.9 × 1016 dpm y-1).

Gonneea, Meagan Eagle; Charette, Matthew A.; Liu, Qian; Herrera-Silveira, Jorge A.; Morales-Ojeda, Sara M.

2014-05-01

88

The aqueous geochemistry of rare earth elements: V. Application of photoacoustic spectroscopy to speciation at low rare earth element concentrations  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy (PAS) yields information on complexation identical to that obtainable with conventional UV-visible absorption spectroscopy, but is up to three orders of magnitude more sensitive. The applicability of PAS to the study of Er 3+ oxalate and hydroxide complexes, at 25°C and 1 bar, has been demonstrated. Spectra can be obtained at concentrations as low as 10-20 ?M, and observed spectral changes as a function of pH and oxalate concentration are consistent with the most reliable thermodynamic data available for these systems.

Wood, Scott A.; Drew Tait, C.; Janecky, David R.; Constantopoulos, Term L.

1995-12-01

89

Spherical disharmonics in the Earth sciences and the spatial solution: Ridges, hotspots, slabs, geochemistry and tomography correlations  

NASA Technical Reports Server (NTRS)

There is increasing use of statistical correlations between geophysical fields and between geochemical and geophysical fields in attempts to understand how the Earth works. Typically, such correlations have been based on spherical harmonic expansions. The expression of functions on the sphere as spherical harmonic series has many pitfalls, especially if the data are nonuniformly and/or sparsely sampled. Many of the difficulties involved in the use of spherical harmonic expansion techniques can be avoided through the use of spatial domain correlations, but this introduces other complications, such as the choice of a sampling lattice. Additionally, many geophysical and geochemical fields fail to satisfy the assumptions of standard statistical significance tests. This is especially problematic when the data values to be correlated with a geophysical field were collected at sample locations which themselves correlate with that field. This paper examines many correlations which have been claimed in the past between geochemistry and mantle tomography and between hotspot, ridge, and slab locations and tomography using both spherical harmonic coefficient correlations and spatial domain correlations. No conclusively significant correlations are found between isotopic geochemistry and mantle tomography. The Crough and Jurdy (short) hotspot location list shows statistically significant correlation with lowermost mantle tomography for degree 2 of the spherical harmonic expansion, but there are no statistically significant correlations in the spatial case. The Vogt (long) hotspot location list does not correlate with tomography anywhere in the mantle using either technique. Both hotspot lists show a strong correlation between hotspot locations and geoid highs when spatially correlated, but no correlations are revealed by spherical harmonic techniques. Ridge locations do not show any statistically significant correlations with tomography, slab locations, or the geoid; the strongest correlation is with lowermost mantle tomography, which is probably spurious. The most striking correlations are between mantle tomography and post-Pangean subducted slabs. The integrated locations of slabs correlate strongly with fast areas near the transition zone and the core-mantle boundary and with slow regions from 1022-1248 km depth. This seems to be consistent with the 'avalanching' downwellings which have been indicated by models of the mantle which include an endothermic phase transition at the 670-km discontinuity, although this is not a unique interpretation. Taken as a whole, these results suggest that slabs and associated cold downwellings are the dominant feature of mantle convection. Hotspot locations are no better correlated with lower mantle tomography than are ridge locations.

Ray, Terrill W.; Anderson, Don L.

1994-01-01

90

Rare earth elements in Holocene reefal microbialites: a new shallow seawater proxy  

NASA Astrophysics Data System (ADS)

The concentration of rare earth elements and yttrium (REE + Y) was determined in Holocene Mg-calcite microbialites from shallow reef framework cavities at Heron Reef, Great Barrier Reef. Shale-normalized REE + Y patterns of 52 microbialite samples show: (1) uniform heavy REE enrichment (Nd SN/Yb SN = 0.236, SD = 0.026); (2) consistent negative Ce and positive La anomalies; (3) marine Y/Ho ratios (56.17, SD = 2.66); and (4) slightly positive Gd anomalies. All of these features are consistent with the geochemistry of well-oxygenated, shallow ambient seawater. REE partition coefficients were calculated relative to shallow Coral Sea seawater. They are uniform (relative SD = 10.2%) across the entire mass range and almost two orders of magnitude higher than those between coral and seawater. Hence, terrigenous detritus-free, modern microbialites are a more reliable proxy for seawater REE chemistry than are skeletal carbonates. Ancient limestones have been considered largely problematic as sources for REE proxies owing to perceived problems with diagenesis, partly on the basis of relatively high REE concentrations in some limestones compared to modern skeletal carbonates. However, high REE concentrations in modern microbialites suggest that ancient limestones with relatively high REE concentrations, if not contaminated by terrigenous detritus, may reflect original seawater chemistry. Terrigenous contamination, if present, is readily detectable on the basis of co-occurring trace element concentrations (Sc, Hf, Th) and Y/Ho ratio. Hence, ancient, particularly reefal, limestones may provide reliable seawater REE proxies. The occurrence of microbialites in clean limestones as old as 3.5 Ga suggests the possibility of reconstructing shallow marine REE chemistry over most of Earth history with important implications for paleogeography and paleoredox studies.

Webb, Gregory E.; Kamber, Balz S.

2000-05-01

91

Uncovering the end uses of the rare earth elements.  

PubMed

The rare earth elements (REE) are a group of fifteen elements with unique properties that make them indispensable for a wide variety of emerging and conventional established technologies. However, quantitative knowledge of REE remains sparse, despite the current heightened interest in future availability of the resources. Mining is heavily concentrated in China, whose monopoly position and potential restriction of exports render primary supply vulnerable to short term disruption. We have drawn upon the published literature and unpublished materials in different languages to derive the first quantitative annual domestic production by end use of individual rare earth elements from 1995 to 2007. The information is illustrated in Sankey diagrams for the years 1995 and 2007. Other years are available in the supporting information. Comparing 1995 and 2007, the production of the rare earth elements in China, Japan, and the US changed dramatically in quantities and structure. The information can provide a solid foundation for industries, academic institutions and governments to make decisions and develop strategies. PMID:23602698

Du, Xiaoyue; Graedel, T E

2013-09-01

92

Rare earth element partition coefficients in zircon/melt systems  

NASA Astrophysics Data System (ADS)

In principle, rare earth element (REE) concentrations in magmatic zircon crystals can be used to reconstruct growth conditions, provided accurate information is available about the partitioning of REEs between zircon and magma. Over the past twenty-five years, there have been several studies published that used natural and synthetic samples to determine zircon-melt rare earth element (REE) partition coefficients (D's) in geological systems. These data show a remarkable range in values covering several orders of magnitude for some REEs, pointing to as yet unquantified effects of pressure, temperature and/or composition on zircon-melt D's. This calls into question the validity of using these data to calculate the REE composition of co-existing melts. To be able to quantify the effects of P, T and X on zircon-melt partitioning, a theoretical framework to interpret zircon-melt D's is required. As a first step towards this framework, we assessed literature zircon-melt REE D's using the lattice strain model proposed by Blundy and Wood (1994). This model assumes that the primary factor influencing elemental partitioning into a mineral is the strain caused by substituting a trace element into a crystal lattice site. Unconstrained fits to available data give physically unrealistic values for Ro [optimum radius of the zircon Zr site]; Do [(theoretical) strain-free partition coefficient]; and E [apparent Young's Modulus]. Using the well- constrained partitioning data from Hanchar et al. (2001), we derive improved constraints on the relation between E and r0, allowing far more realistic fits to literature data. From the resulting fits it is clear that many LREE D's show significant positive deviations from trends predicted by the lattice strain model. This may reflect analytical problems or mineral inclusions (e.g., monazite), and makes them unsuitable for use in geochemical modelling. The data reported by Sano et al. (2001) for an ion-probe study of REE partitioning between silicate glass, zircon and apatite appear most consistent with lattice-strain based expectations. References Blundy, J., and Wood, B. (1994) Prediction of crystal-melt partition coefficients from elastic moduli. Nature, 372, 452-454. Hanchar, J.M., Finch, R.J., Hoskin, P.W.O., Watson, E.B., Cherniak, D.J., and Mariano, A.N. (2001) Rare earth elements in synthetic zircon. 1. Synthesis and rare earth element and phosphorus doping. American Mineralogist 86: 667-680. Sano, Y., Terada, K., Fukuoka, T. (2001) Ion microprobe analysis of rare earth elements in silicate glass, apatite, and zircon. Eleventh Annual V.M. Goldschmidt Conference, Abstract # 3310, LPI Contribution No. 1088, Lunar and Planetary Institute, Houston (CD-ROM).

Hanchar, J. M.; van Westrenen, W.

2006-12-01

93

Geochemistry of mantle-core differentiation at high pressure  

Microsoft Academic Search

THE apparent excess of siderophile (iron-Ioving) elements in the Earth's mantle has been a long-standing enigma in the geochemistry of mantle-core differentiation1,2. Although current models have proved successful in explaining some aspects of this problem3-7, important questions remain. In particular, the mantle's near-chondritic ratio of nickel to cobalt (close to that expected for the material from which the Earth formed)

Jie Li; Carl B. Agee

1996-01-01

94

Rare earth element distributions and trends in natural waters with a focus on groundwater.  

PubMed

Systematically varying properties and reactivities have led to focused research of the environmental forensic capabilities of rare earth elements (REE). Increasing anthropogenic inputs to natural systems may permanently alter the natural signatures of REE, motivating characterization of natural REE variability. We compiled and analyzed reported dissolved REE concentration data over a wide range of natural water types (ground-, ocean, river, and lake water) and groundwater chemistries (e.g., fresh, brine, and acidic) with the goal of quantifying the extent of natural REE variability, especially for groundwater systems. Quantitative challenges presented by censored data were addressed with nonparametric distributions and regressions. Reported measurements of REE in natural waters range over nearly 10 orders of magnitude, though the majority of measurements are within 2-4 orders of magnitude, and are highly correlated with one another. Few global correlations exist among dissolved abundance and bulk solution properties in groundwater, indicating the complex nature of source-sink terms and the need for care when comparing results between studies. This collection, homogenization, and analysis of a disparate literature facilitates interstudy comparison and provides insight into the wide range of variables that influence REE geochemistry. PMID:24628583

Noack, Clinton W; Dzombak, David A; Karamalidis, Athanasios K

2014-04-15

95

Deep water rare earth element composition in the Cenozoic  

Microsoft Academic Search

The utility of hydrothermal metalliferous sediments in examining past deep water composition has recently been explored through the generation of high-resolution records for both Nd isotopes and rare earth elements (RRE) from the East Pacific Rise (SEPR, 11oS, 3100m). REEs are dominated (96%) by seawater REEs adsorbed to Fe particles in these metalliferous carbonates; the hydrothermal source itself is negligible.

D. Delanghe-Sabatier; R. Sherrell; J. Wright; B. Hamelin

2003-01-01

96

Ion probe measurement of rare earth elements in biogenic phosphates  

NASA Astrophysics Data System (ADS)

The rare earth element (REE) distributions in individual fish teeth and conodonts have been measured by ion probe. Concentrations and La/Yb ratios show little variations, except in the enamel, which suggests that REE uptake from the sedimented biogenic debris takes place at the water-sediment interface as an essentially quantitative process without fractionation. Late diagenetic disturbances remained of marginal importance. Hence, REE in phosphatic debris might reflect the input from the overlying water column.

Grandjean, Patricia; Albarède, Francis

1989-12-01

97

Rare earth elements as geochemical tracers of regional groundwater mixing  

Microsoft Academic Search

The rare earth elements (REE) were analyzed in a groundwater system from south-central Nevada (i.e., Ash Meadows National Wildlife Refuge, the Spring Mountains, Pahranagat National Wildlife Refuge, and the Nevada Test Site) in order to investigate their potential use as tracers of regional groundwater flow. Previous investigations using conservative tracers (e.g., deuterium and uranium isotopes) identified recharge in local mountains

Kevin H. Johannesson; Klaus J. Stetzenbach; Vernon F. Hodge

1997-01-01

98

Insights Into the Early Volatile History of the Earth From the Geochemistry of Iodine and Xenon  

NASA Astrophysics Data System (ADS)

Evidence that liquid water was stable on the Earth before 4.4 by ago comes from studies of very old zircons. This evidence seems at odds with the giant impact model of the Moon's formation, which should have resulted in melting of a large portion of the Earth's interior and the formation of a deep magma ocean. The stabilization of a primitive crust, and the attainment of surface temperatures allowing liquid water stability would have to have occurred within about 100 my of the onset of solar nebula condensation. Xe129, produced by the decay of now extinct I129 (t1/2 = 17 my), provides a tracer for volatile processes in the earliest history of the Earth. Catastrophic outgassing of the mantle as proposed to explain the Xe129/Xe132 ratios of MORBs (1.014) and the atmosphere (0.985) could have happened in the context of a post-giant-impact magma ocean only if it occurred on a timescale of 100 my or less. To assess the effects of outgassing of an early magma ocean on the I/Xe systematics of the Earth's mantle, we consider a simple two-reservoir (MORB-source mantle and atmosphere) model with partial melting of the mantle occurring in equilibrium with residual minerals followed by eruption and degassing. Experimentally determined I and Xe mineral/melt partition coefficients and silicate-melt solubility values for I and Xe are employed in mass balance calculations based on this two-reservoir model. The amount of I/Xe enrichment in the MORB-source mantle and the extent of melting and outgassing needed depend on the timing of outgassing. If it was completed by 50 my following solar nebula condensation, then the MORB-source mantle needs to have been at least 50% molten and 90% outgassed. If it was completed by 100 my, then the mantle must have been at least 95% molten and 99% outgassed. So, the longer the timescale of magma ocean outgassing, the more extensively melted it has to be. This result accentuates the necessity for a quick cooling of the magma ocean and the early stability of liquid water and illustrates the difficulty of fractionating I from Xe by purely magmatic processes. However, water is extremely effective at fractionating I from Xe. Once liquid water became stable at the Earth's surface, outgassed I could be recycled hydrothermally into the oceanic crust and subducted back into the mantle, which was, by now, partially degassed of Xe. Subsequent decay of I129 would give a MORB-source mantle with an elevated Xe129/Xe132 ratio relative to the earlier outgassed atmosphere.

Musselwhite, D.; Drake, M.

2006-05-01

99

Uncovering the Global Life Cycles of the Rare Earth Elements  

PubMed Central

The rare earth elements (REE) are a group of fifteen elements with unique properties that make them indispensable for a wide variety of emerging, critical technologies. Knowledge of the life cycles of REE remains sparse, despite the current heightened interest in their future availability. Mining is heavily concentrated in China, whose monopoly position and potential restriction of exports render primary supplies vulnerable to short and long-term disruption. To provide an improved perspective we derived the first quantitative life cycles (for the year 2007) for ten REE: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), and yttrium (Y). Of these REE, Ce and Nd in-use stocks are highest; the in-use stocks of most REE show significant accumulation in modern society. Industrial scrap recycling occurs only from magnet manufacture. We believe there is no post-customer recycling of any of these elements.

Du, Xiaoyue; Graedel, T. E.

2011-01-01

100

Anthropogenic Disturbance of Element Cycles at the Earth's Surface  

NASA Astrophysics Data System (ADS)

The extent to which humans are modifying Earth's surface chemistry can be quantified by comparing total anthropogenic element fluxes with their natural counterparts [1]. We determine anthropogenic mass transfer of 77 elements from mining, fossil fuel burning, biomass burning, construction activities, and human apportionment of terrestrial net primary productivity, and compared it to natural mass transfer from terrestrial and marine net primary productivity, riverine dissolved and suspended matter fluxes to the ocean, soil erosion, eolian dust, sea-salt spray, cosmic dust, volcanic emissions and - for helium - hydrodynamic escape from the Earth's atmosphere. In addition, we introduce an approach to correct for losses during industrial processing of elements belonging to geochemically coherent groups, and explicitly incorporated uncertainties of element mass fluxes through Monte Carlo simulations [2]. Our assessment indicates that anthropogenic fluxes of iridium, osmium, helium, gold, ruthenium, antimony, platinum, palladium, rhenium, rhodium and chromium are greater than the respective natural fluxes. For these elements mining is the major factor of human dominance, whereas petroleum burning strongly influence the surficial cycle of rhenium. Apart from these 11 elements there are 15 additional elements whose anthropogenic fluxes may surpass their corresponding natural fluxes. Anthropogenic fluxes of the remaining elements are smaller than their corresponding natural fluxes although a significant human influence is observed for all of them. For example, ~20% of the annual fluxes of C, N, and P can be attributed to human activities. Such disturbances, though small compared with natural fluxes, can significantly alter concentrations in near-surface reservoirs and affect ecosystems if they are sustained over time scales similar to or longer than the residence time of elements in the respective reservoir. Examples are the continuing input of CO2 to the atmosphere that has led to a 40% increase in atmospheric CO2 concentrations, and the atmospheric redistribution of reactive nitrogen and accumulation in remote ecosystems. We note that if anthropogenic contributions to soil erosion and eolian dust are considered, anthropogenic fluxes of up to 62 elements may surpass their corresponding natural fluxes. [1] Klee and Graedel (2004), Annu. Rev. Environ. Resour., 29, p. 69-107 [2] Sen and Peucker-Ehrenbrink (2012), Environ. Sci. Technol., dx.doi.org/10.1021/es301261x

Sen, I. S.; Peucker-Ehrenbrink, B.

2012-12-01

101

Elemental Geochemistry of Samples From Fault Segments of the San Andreas Fault Observatory at Depth (SAFOD) Drill Hole  

NASA Astrophysics Data System (ADS)

Elemental geochemistry of mudrock samples from phase 2 drilling of the San Andreas Fault Observatory at Depth (SAFOD) is presented from bore hole depths of 3066 m to 3169 m and from 3292 m to 3368 m, which contain a creeping section and main trace of the fault, respectively. In addition to preparation and analysis of whole rock sample, fault grains with neomineralized, polished surfaces were hand picked from well-washed whole rock samples, minimizing the potential contamination from drilling mud and steel shavings. The separated fractions were washed in deionized water, powdered using a mortar and pestle, and analyzed using an Inductively Coupled Plasma- Optical Emission Spectrometer for major and minor elements. Based on oxide data results, systematic differences in element concentrations are observed between the whole rock and fault rock. Two groupings of data points are distinguishable in the regions containing the main trace of the fault, a shallow part (3292- 3316 m) and a deeper section (3320-3368 m). Applying the isocon method, assuming Zr and Ti to be immobile elements in these samples, indicates a volume loss of more than 30 percent in the shallow part and about 23 percent in the deep part of the main trace. These changes are minimum estimates of fault-related volume loss, because the whole rock from drilling samples contains variable amount of fault rock as well. Minimum estimates for volume loss in the creeping section of the fault are more than 50 percent when using the isocon method, comparing whole rock to plucked fault rock. The majority of the volume loss in the fault rocks is due to the dissolution and loss of silica, potassium, aluminum, sodium and calcium, whereas (based on oxide data) the mineralized surfaces of fractures appear to be enriched in Fe and Mg. The large amount of element mobility within these fault traces suggests extensive circulation of hydrous fluids along fractures that was responsible for progressive dissolution and leaching of the wall rock during faulting.

Tourscher, S. N.; Schleicher, A. M.; van der Pluijm, B. A.; Warr, L. N.

2006-12-01

102

Standard reference water samples for rare earth element determinations  

USGS Publications Warehouse

Standard reference water samples (SRWS) were collected from two mine sites, one near Ophir, CO, USA and the other near Redding, CA, USA. The samples were filtered, preserved, and analyzed for rare earth element (REE) concentrations (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) by inductively coupled plasma-mass spectrometry (ICP-MS). These two samples were acid mine waters with elevated concentrations of REEs (0.45-161 ??g/1). Seventeen international laboratories participated in a 'round-robin' chemical analysis program, which made it possible to evaluate the data by robust statistical procedures that are insensitive to outliers. The resulting most probable values are reported. Ten to 15 of the participants also reported values for Ba, Y, and Sc. Field parameters, major ion, and other trace element concentrations, not subject to statistical evaluation, are provided.

Verplanck, P. L.; Antweiler, R. C.; Nordstrom, D. K.; Taylor, H. E.

2001-01-01

103

Magnetic property improvement of niobium doped with rare earth elements  

NASA Astrophysics Data System (ADS)

A new idea is proposed by the PKU group to improve the magnetic properties of the Type-II superconductor niobium. Rare earth elements like scandium and yttrium are doped into ingot niobium during the smelting processes. A series of experiments have been done since 2010. The preliminary testing results show that the magnetic properties of niobium materials have changed with different doping elements and proportions while the superconductive transition temperature does not change very much. This method may increase the superheating magnetic field of niobium so as to improve the performance of the niobium cavity, which is a key component of SRF accelerators. A Tesla-type single-cell cavity made of scandium-doped niobium is being fabricated.

Jiang, Tao; He, Fei-Si; Jiao, Fei; He, Fa; Lu, Xiang-Yang; Zhao, Kui; Zhao, Hong-Yun; You, Yu-Song; Chen, Lin

2014-05-01

104

Preparation of microcapsules containing rare-earth metal elements.  

PubMed

Microcapsules for internal radiation therapies containing the rare-earth metal elements Dy, Ho and Cu with a diameter of 5-10 microm were successfully obtained by an interfacial polymerization method and a successive sedimentation technique was employed to fractionate the microcapsules. A triisocyanate monomer and tricresylphosphate were used for a wall forming material and a core solvent for the metals, respectively. The amount of the metal elements loaded was measured using a high frequency plasma photoemission apparatus. The beta-ray radioactivity of 1 mg of microcapsules irradiated with a common neutron source is estimated as 370 microCi, which is satisfactorily strong for usual radiotherapy, when microcapsules containing Dy are used. Differential interference microscopy indicated narrow size distribution of the fractionated microcapulses. PMID:11201336

Shimofure, S; Koizumi, S; Ichikawa, K; Ichikawa, H; Dobashi, T

2001-01-01

105

Source and mobility of Rare Earth Elements in a sedimentary aquifer system: Aquitaine basin (Southern France)  

NASA Astrophysics Data System (ADS)

The study of rare earth elements (REEs) in natural waters initially involved an examination of their occurrence and behavior in seawater and coastal waters such as estuaries. Since the 1990s, REE geochemistry has been applied to continental waters such as rivers and lakes and groundwaters. Rare earth elements) are of great interest because of their unique characteristics and have been used in the study of many geological processes like weathering and water-rock interaction processes, provenance of sediments, etc... With the evolution of analytical techniques like new generation ICP-MS, much attention had been paid towards the water geochemistry of REEs. However, there is a need of more investigations devoted to REEs in large groundwater systems, especially on the understanding of the distribution of REEs and their evolution in such systems. In this frame, large sedimentary aquifer systems often constitute strategic water resources for drinking water supply, agriculture irrigation and industry, but can also represent an energetic resource for geothermal power. Large water abstractions can induce complete modification of the natural functioning of such aquifer systems. These large aquifer systems thus require water management at the basin scale in order to preserve both water quantity and quality. The large Eocene Sand aquifer system of the Aquitaine sedimentary basin was studied through various hydrological, chemical and isotopic tools. This system extends over 116,000 km2 in the South west part of the French territory. The aquifer being artesian in the west of the district and confined with piezometric levels around 250-m depth in the east. The 'Eocene Sands', composed of sandy Tertiary sediments alternating with carbonate deposits, is a multi-layer system with high permeability and a thickness of several tens of metres to a hundred metres. The Eocene Sand aquifer system comprises at least five aquifers: Paleocene, Eocene infra-molassic sands (IMS), early Eocene, middle Eocene, and late Eocene. One important feature, in these confined systems isolated from anthropogenic influence, is the range in salinities by a factor of 10, from 250 mg/L up to 2.5 g/L. The ?REE, in the range 2-54 ng/L, with a dependence on salinity when expressed in % HCO3 or SO4, reflect the carbonate or evaporite source of REEs. The UCC normalized-REE patterns show a large variability as exemplified by the REE flat patterns-low SREE associated with salinity controlled by HCO3. In the present work, the REEs are investigated in terms of saturation indices, speciation modelling, REE patterns in order to recognize the aquifer type hosting groundwater and decipher the origin of the salinity of the groundwater as some part of the aquifer display in the groundwater concentration of chemical element exceeding the drinking water standard (SO4, F...). Such high concentrations of naturally-occurring substances (e.g. unaffected by human activities) can have negative impacts on groundwater thresholds and deciphering their origin by means of geochemical tools like REE is a remaining challenge.

Negrel, P. J.; Petelet-Giraud, E.; Millot, R.; Malcuit, E.

2011-12-01

106

Trace element geochemistry of soils and plants in Kenyan conservation areas and implications for wildlife nutrition  

Microsoft Academic Search

Trace element concentrations in soils, plants and animals in National Parks and Wildlife Reserves in Kenya are assessed using geochemical mapping techniques. Soil trace element concentrations are shown to be related to soil parent material and possibly to pedological and hydrological factors. At Lake Nakuru National Park, plant trace element concentrations vary with plant species and the geochemical conditions that

John Maskall; Iain Thornton

1991-01-01

107

Urban soil geochemistry in Athens, Greece: The importance of local geology in controlling the distribution of potentially harmful trace elements.  

PubMed

Understanding urban soil geochemistry is a challenging task because of the complicated layering of the urban landscape and the profound impact of large cities on the chemical dispersion of harmful trace elements. A systematic geochemical soil survey was performed across Greater Athens and Piraeus, Greece. Surface soil samples (0-10cm) were collected from 238 sampling sites on a regular 1×1km grid and were digested by a HNO3-HCl-HClO4-HF mixture. A combination of multivariate statistics and Geographical Information System approaches was applied for discriminating natural from anthropogenic sources using 4 major elements, 9 trace metals, and 2 metalloids. Based on these analyses the lack of heavy industry in Athens was demonstrated by the influence of geology on the local soil chemistry with this accounting for 49% of the variability in the major elements, as well as Cr, Ni, Co, and possibly As (median values of 102, 141, 16 and 24mgkg(-1) respectively). The contribution to soil chemistry of classical urban contaminants including Pb, Cu, Zn, Sn, Sb, and Cd (medians of 45, 39, 98, 3.6, 1.7 and 0.3mgkg(-1) respectively) was also observed; significant correlations were identified between concentrations and urbanization indicators, including vehicular traffic, urban land use, population density, and timing of urbanization. Analysis of soil heterogeneity and spatial variability of soil composition in the Greater Athens and Piraeus area provided a representation of the extent of anthropogenic modifications on natural element loadings. The concentrations of Ni, Cr, and As were relatively high compared to those in other cities around the world, and further investigation should characterize and evaluate their geochemical reactivity. PMID:24662205

Argyraki, Ariadne; Kelepertzis, Efstratios

2014-06-01

108

The Significance of Rare Earth Element Partition Coefficients in Zircon  

NASA Astrophysics Data System (ADS)

Over the past twenty years, there have been several studies published that used natural and synthetic samples to determine rare earth element (REE) partition coefficients for zircon in geological systems. As expected from crystal-chemical considerations, results obtained from these studies revealed that heavy REE (HREE) are more compatible than light REE (LREE) in zircon. This trend is caused primarily by decreasing ionic radii of trivalent REE from La to Lu as they approach ionic radius of Zr in zircon. When plotted against ionic radius, empirical curves through published partition coefficients of trivalent REE in zircon are convex upward, showing degrees of flatness for LREE. The strain-elasticity model for mineral-melt partition coefficients proposed by Blundy and Wood (1994) assumes that the primary factor influencing elemental partitioning into a mineral is the strain caused by substituting a trace element into a structural site. In order to estimate the three parameters Ro [optimum radius of the lattice site], Do [(theoretical) strain-free partition coefficient], and E [YoungIs Modulus], we applied a least-squares fit of empirical REE partitioning data for synthetic zircon (Hanchar et al., 2001) to the Blundy and Wood theoretical model. We then used Ro, Do and E, as determined above using the synthetic zircon data, to constrain the fit of the Blundy and Wood model to other published partition coefficients for natural and synthetic zircon. We also used a least-squares fit to published REE partitioning data for zircon without constraining the values of Ro, Do and E, in order to evaluate the extent to which published partitioning coefficients agree with the Blundy and Wood model. Most data that we fit without constraint to the Blundy and Wood model deviate significantly from partition coefficients predicted by the Blundy and Wood model, which may reflect analytical problems or mineral inclusions (e.g., monazite). Data with which the Blundy and Wood model agrees best are those reported by Sano et al. (2001) for an ion-probe study of REE partitioning between silicate glass, zircon and apatite. Furthermore, the Blundy and Wood model fits the data of Sano et al., best if Ro, Do, and E are first determined by using data reported by Hanchar et al. (2001). References Blundy, J., and Wood, B. (1994) Prediction of crystal-melt partition coefficients from elastic moduli. Nature, 372, 452-454. Hanchar, J.M., Finch, R.J., Hoskin, P.W.O., Watson, E.B., Cherniak, D.J., and Mariano, A.N. (2001) Rare earth elements in synthetic zircon. 1. Synthesis and rare earth element and phosphorus doping. American Mineralogist 86: 667-680. Sano, Y., Terada, K., Fukuoka, T. (2001) Ion microprobe analysis of rare earth elements in silicate glass, apatite, and zircon. Eleventh Annual V.M. Goldschmidt Conference, Abstract # 3310, LPI Contribution No. 1088, Lunar and Planetary Institute, Houston (CD-ROM).

Hanchar, J. M.; van Westrenen, W.; Finch, R. J.

2002-05-01

109

Trace Element Distributions In San Diego Bay: Copper, zinc, manganese, and the rare earth elements  

NASA Astrophysics Data System (ADS)

San Diego Bay is characterized by the occurrence of large concentration increases in copper and zinc, often related to the inputs of ships in this important harbor (Katz, 1998; Zirino et al, 1978, 1998; Esser and Volpe, 2002). In this paper we report the first data on the distribution of rare earth elements (REE) in the waters of San Diego Bay. The combination of the rare earths data set as well as the other trace element distributions allow us to determine the importance of sediment recycling on trace metals in the Bay. The data suggest that remobilization of trace metals at or near the sediment water interface is of importance (Leather et al., 1995; Chadwick, personal communication). Relevant data from both sedimentary pore fluids and benthic flux measurements that support these interpretations will also be shown.

Gieskes, J. M.; Mahn, C. L.; Rivera-Duarte, I.; Chadwick, B.

2002-12-01

110

Geochemistry of environmentally sensitive trace elements in Permian coals from the Huainan coalfield, Anhui, China  

USGS Publications Warehouse

To study the geochemical characteristics of 11 environmentally sensitive trace elements in the coals of the Permian Period from the Huainan coalfield, Anhui province, China, borehole samples of 336 coals, two partings, and four roof and floor mudstones were collected from mineable coal seams. Major elements and selected trace elements were determined by inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and hydride generation atomic absorption spectrometry (HAAS). The depositional environment, abundances, distribution, and modes of occurrence of trace elements were investigated. Results show that clay and carbonate minerals are the principal inorganic constituents in the coals. A lower deltaic plain, where fluvial channel systems developed successively, was the likely depositional environment of the Permian coals in the Huainan coalfield. All major elements have wider variation ranges than those of Chinese coals except for Mg and Fe. The contents of Cr, Co, Ni, and Se are higher than their averages for Chinese coals and world coals. Vertical variations of trace elements in different formations are not significant except for B and Ba. Certain roof and partings are distinctly higher in trace elements than underlying coal bench samples. The modes of occurrence of trace elements vary in different coal seams as a result of different coal-forming environments. Vanadium, Cr, and Th are associated with aluminosilicate minerals, Ba with carbonate minerals, and Cu, Zn, As, Se, and Pb mainly with sulfide minerals. ?? 2011 Elsevier B.V.

Chen, J.; Liu, G.; Jiang, M.; Chou, C. -L.; Li, H.; Wu, B.; Zheng, L.; Jiang, D.

2011-01-01

111

Trace Element Geochemistry of the Dolomite Member of the Neoproterozoic Ibex Formation, Death Valley National Park, CA  

NASA Astrophysics Data System (ADS)

This work examines the major and trace element geochemistry of the pink, laminated Dolomite Member of the Neoprotoerozic Ibex Formation, sampled at high resolution in the Ibex Hills of Death Valley, California. The Dolomite Member of the Ibex Formation directly overlies a basal conglomerate which has lead Corsetti and Kaufman (2005) to speculate that the juxtaposition of these units represents a diamictite - cap carbonate pair. Cap carbonates are inferred to represent deposition under high alkalinity conditions in the shallow ocean at the termination of low latitude glaciation. Increased alkalinity may be driven by the post glacial overturn of anoxic water masses. Here we infer paleoredox conditions during the deposition of the Dolomite Member of the Ibex Formation using trace metal enrichments. The Dolomite Member shows enrichments of Ni, Mo, Fe, Cu, V, Co, and Ba near the base of the unit, and also has a weak overall enrichment in Mn. The enrichment of these metals suggests a period of anoxia during the initial deposition of the Dolomite, and may signal the introduction of basin brines to the shallow ocean during marine transgression. These data are consistent with patterns observed in other cap carbonates worldwide, and support the speculation that the Dolomite Member is a cap carbonate. Alternatively, trace metal enrichments may reflect diagenetic alteration.

Meyer, E. E.; Lanids, J. D.; Quicksall, A. N.; Ddamba, I.

2012-12-01

112

Ternary phosphates of rubidium-cesium-rare earth element  

SciTech Connect

This article examines the possibility of the existence of ternary phosphates of the rare earth elements (REE) containing two large alkali cations in order to establish the morphological and physicochemical characteristics in the entire group of ternary REE phosphates. The synthesis of the ternary rubidium-cesium-REE phosphates was carried out with molten charges that did not contain an excess of components. Analysis for the uncommon alkali cations was done by the atomic absorption technique; for holmium, by complexometric titration; and for phosphorus, by gravimetry as NH/sub 4/CdPO/sub 4/. The data obtained fully confirm the composition of Rb/sub 2/CsLn(PO/sub 4/)/sub 2/.

Mel'nikov, P.P.; Carrillo-Eredero, H.D.; Efremov, V.A.; Komissarova, L.N.; Quiroga, E.

1986-06-01

113

Use of Rare Earth Elements in Investigations of Aeolian Processes  

NASA Astrophysics Data System (ADS)

Aeolian movement of surface sediments is a natural geomorphic process that has shaped landscapes and contributes to atmospheric dust loading. Even on seemingly uniform surfaces, aeolian activity is highly variable in space and time. Tagging individual particles with Rare Earth Elements (REE) that are present in only trace amounts in the native surface soils allows the study of aeolian transport from source to sink. Rare Earth Oxides are dissolved in nitric acid and diluted to provide a several order of magnitude increase in soil REE concentration when sprayed on the source soil and allowed to infiltrate to a shallow depth. A single REE may be applied to a small area of the surface or multiple REEs may be applied to discrete micro-sites on the surface. The sediments trapped by standard aeolian samplers record the relative contributions of the tagged areas and the dispersal from a point source. We have successfully used REEs to investigate preferential micro-sites for post-fire aeolian activity in a heterogeneous environment and to investigate single season aeolian dispersal from a point source. We are also collaborating with others on the use of REEs to quantify the development of nutrient islands in desert shrublands.

Van Pelt, R. S.; Barnes, M. A.; Zobeck, T. M.

2012-12-01

114

Rare Earth elements in individual minerals in Shergottites  

NASA Technical Reports Server (NTRS)

Shergottites (i.e., Shergotty, Zagami, EETA79001, ALHA77005, and LEW88516) are an important set of achondrites because they comprise the majority of the SNC group of meteorites (nine, in total, known to us), which are likely to be samples of the planet Mars. Study of these meteorites may therefore provide valuable information about petrogenetic processes on a large planetary body other than Earth. Rare earth element (REE) distributions between various mineral phases were found to be useful in geochemically modeling the petrogenesis of various rock types (terrestrial and meteoritic). However, with the exception of a few ion microprobe studies and analyses of mineral separates, there has previously not been any comprehensive effort to characterize and directly compare REE in individual minerals in each of the five known shergottites. Ion microprobe analyses were made on thin sections of each of the shergottites. Minerals analyzed were pyroxenes (pigeonite and augite), maskelynite, and whitlockite. The REE concentrations in each mineral type in each shergottite is given.

Wadhwa, Meenakshi; Crozaz, Ghislaine

1993-01-01

115

Geochemistry of minor elements in the Monterey Formation, California; seawater chemistry of deposition  

USGS Publications Warehouse

Approximately 24 samples of the Monterey Formation, Southern California, have been analyzed for their major-element oxide and minor-element content. These analyses allow identification of a detrital fraction, composed of terrigenous quartz, clay minerals, and other Al silicate minerals, and a marine fraction, composed of biogenic silica, calcite, dolomite, organic matter, apatite, and minor amounts of pyrite. The minor-element contents in the marine fraction alone are interpreted to have required, at the time of deposition, a high level of primary productivity in the photic zone and denitrifying bacterial respiration in the bottom water.

Piper, D. Z.; Isaacs, C. M.

1995-01-01

116

RECONSTRUCTING LAURENTIDE ICE SHEET MELTWATER GEOCHEMISTRY USING COMBINED STABLE ISOTOPE AND LASER ABLATION TRACE ELEMENT ANALYSES  

NASA Astrophysics Data System (ADS)

Little is known about the oxygen isotope evolution of Northern hemisphere ice sheets during past glacial cycles, with the exception of results from models and calculations based on whole ocean ?18O change. Reconstructing changes in the ?18Owater of the global ocean assumes a homogeneous ?18O value for contributions from Northern hemisphere ice sheets with a mass balance contribution from the Southern hemisphere. Because oceanic ?18Ow forms a crucial baseline for deconvolving the combined signal of temperature and hydrologic changes recorded in foraminiferal calcite, constraints on the contributions of melting ice sheets form a fundamental component of reconstructions of global ocean ?18Ow changes on glacial timescales. Here we present a novel geochemical technique to compute the oxygen isotopic composition of Laurentide Ice Sheet (LIS) meltwater flowing into the Gulf of Mexico during periods of rapid ice sheet melting. The technique combines data from different types of geochemical analyses on individual shells of the planktonic foraminifera Orbulina universa to compute meltwater geochemistry, using laser ablation ICP-MS to measure Mg/Ca (a temperature proxy) and Ba/Ca (a salinity proxy) and isotope ratio mass spectrometry to measure ?18O (a temperature and ?18Owater proxy) on remaining shell material. O. universa has a very large temperature and salinity tolerance (9-30°C; 23-45 psu) and broad depth habitat (0-80 m), so an assemblage of individual shells from a single core interval records a range of water conditions. We have selected deglacial meltwater intervals from core MD02-2550 (26.95°N, 91.35°W, 2245 m water depth), collected from the anoxic Orca Basin in the Gulf of Mexico, for a proof of concept demonstration. From each interval, we combine measurements of Mg/Ca, Ba/Ca, and ?18O on 30-100 individual O. universa. The ?18O from each shell reflects the combined influence of temperature and ?18Owater, where this latter value is a function of mixing between seawater and ice sheet meltwater runoff. Mg/Ca data provide an independent reconstruction of temperature, and Ba/Ca is used as a proxy for salinity in the vicinity of riverine outflow. Combining these data permits us to compute both salinity and ?18Owater for each discrete foraminifera shell. We demonstrate that when an assemblage of salinity and ?18Owater paired data are combined, we are able to compute the ?18Owater of the freshwater (glacial) endmember.

Vetter, L.; Spero, H. J.; Eggins, S. M.; Flower, B. P.; Williams, C. C.

2009-12-01

117

Aqueous geochemistry of the rare earth elements in marine anoxic basins  

Microsoft Academic Search

Life in the oceans mainly occurs in the upper tens of meters of the watercolumn,\\u000awhere sunlight penetrates. This sunlight is used by phytoplankton to combine carbon and\\u000anutrients to organic matter, which subsequently serves zooplankton and higher life forms as\\u000afood. When the plankton dies it slowly settles to the seafloor, meanwhile being decomposed\\u000aby bacteria. This decomposition requires

J. Schijf

1992-01-01

118

Rare earth and trace element geochemistry of metabasalts from the Point Sal ophiolite, California  

Microsoft Academic Search

The Point Sal ophiolite, California, contains a volcanic pile of pillowed and massive basalts and keratophyres that exhibit a downward change in metamorphic facies, i.e., zeolite to greenschist. Analyses of 14 stratigraphically sequential lavas reveals the existence of three lava types: (1) highly fractionated plagioclase phyric lavas at the base of the lava pile; (2) clinopyroxene-plagioclase phyric lavas at different

Martin Menzies; Douglas Blanchard; Jeff Jacobs

1977-01-01

119

Petrology and trace element geochemistry of the Honolulu volcanics, Oahu: implications for the oceanic mantle below Hawaii.  

USGS Publications Warehouse

These volcanic rocks are the products of small-volume, late-stage vents along rifts cutting the older massive Koolan tholeiitic shield on Oahu. Most of the lavas and tuffs have the geochemical features expected of near-primary magmas derived from a peridotite source with olivine Fo87-89, e.g. 100 Mg/(Mg + Fe2+) > 65, Ni > 250 p.p.m. and the presence of ultramafic mantle xenoliths at 18 of the 37 vents. Thus the geochemistry of the alkali olivine basalt, basanite, nephelinite and nepheline melilitite lavas and tuffs of these Honolulu volcanic rocks has been used to deduce the composition of their mantle source and the conditions under which they were generated by partial melting in the mantle. New major- and trace-element analyses for 31 samples are tabulated and indicate derivation by partial melting of a garnet (<10%) lherzolite source which was isotopically homogeneous and compositionally uniform for most major and trace elements, though apparently heterogeneous in TiO2, Zr, Hf, Nb and Ta (due perhaps to the low inferred degrees of melting which failed to exhaust the source in minor residual phases). In comparison with estimates of a primordial mantle composition and the mantle source of MORB, the garnet peridotite source of these Honolulu volcanics was increasingly enriched in the sequence heavy REE, Y, Tb, Ti, Sm, Zr and Hf, for which a multi-stage history is required. This composition differs from the source of the previously erupted tholeiitic shield, nor is it represented in the upper-mantle xenoliths in the lavas and tuff of the unit.-R.A.H.

Clague, D. A.; Frey, F. A.

1982-01-01

120

Pb and rare earth element diffusion in xenotime  

NASA Astrophysics Data System (ADS)

Diffusion of Pb and the rare earth elements Sm, Dy and Yb have been characterized in synthetic xenotime under dry conditions. The synthetic xenotime was grown via a Na 2CO 3-MoO 3 flux method. The sources of diffusant for the rare earth diffusion experiments were REE phosphate powders, with experiments run using sources containing a single REE. For Pb, the source consisted a mixture of YPO 4 and PbTiO 3. Experiments were performed by placing source and xenotime in Pt capsules, and annealing capsules in 1 atm furnaces for times ranging from 30 min to several weeks, at temperatures from 1000 to 1500 °C. The REE and Pb distributions in the xenotime were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relations are obtained for diffusion in xenotime, normal to (101): D=1.5×10exp?(-441±12 kJmol/R?T)ms.D=9.0×10exp?(-349±16 kJmol/R?T)ms.D=3.9×10exp?(-362±13 kJmol/R?T)ms. Diffusivities among the REE do not differ greatly in xenotime over the investigated temperature range, in contrast to findings for the REE in zircon [Cherniak, D.J., Hanchar, J.M., Watson, E.B., 1997. Rare earth diffusion in zircon. Chem. Geol. 134, 289-301.], where the LREE diffuse more slowly, and with higher activation energies for diffusion, than the heavier rare earths. In zircon, these differences among diffusion of the rare earths are attributed to the relatively large size of the REE with respect to Zr, for which they likely substitute in the zircon lattice. With the systematic increase in ionic radius from the heavy to lighter REE, this size mismatch becomes more pronounced and diffusivities of the LREE are as consequence slower. Although xenotime is isostructural with zircon, the REE are more closely matched in size to Y, so in xenotime this effect appears much smaller and the REE diffuse at similar rates. In addition, the process of diffusion in xenotime likely involves simple REE + 3 ? Y + 3 exchange, without charge compensation as needed for REE + 3 ? Zr + 4 exchange in zircon. This latter factor may also contribute to the large activation energies for diffusion of the REE in zircon (i.e., 691-841 kJ mol - 1 , [Cherniak, D.J., Hanchar, J.M., Watson, E.B., 1997. Rare earth diffusion in zircon. Chem. Geol. 134, 289-301.]), in comparison with those for xenotime. For Pb, the following Arrhenius relation is obtained (also normal to (101)): D=3.0×10exp?(-382±64 kJmol/R?T)ms. These measurements suggest that Pb diffusion in xenotime is quite slow, even slower than Pb diffusion in monazite and zircon, and considerably slower than diffusion of the REE in xenotime. Xenotime may therefore be even more retentive of Pb isotope signatures than either monazite or zircon in cases where Pb isotopes are altered solely by volume diffusion. However, because the activation energy for Pb diffusion in xenotime is lower than those for monazite and zircon, Pb diffusion may be somewhat faster at many temperatures of geologic interest in xenotime than in monazite or zircon.

Cherniak, D. J.

2006-05-01

121

Platinum-group elemental geochemistry of mafic and ultramafic rocks from the Xigaze ophiolite, southern Tibet  

NASA Astrophysics Data System (ADS)

The Xigaze ophiolite in the central part of the Yarlung-Zangbo suture zone, southern Tibet, has a well-preserved sequence of sheeted dykes, basalts, cumulates and mantle peridotites at Jiding and Luqu. Both the basalts and diabases at Jiding have similar compositions with SiO 2 ranging from 45.9 to 53.5 wt%, MgO from 3.1 to 6.8 wt% and TiO 2 from 0.87 to 1.21 wt%. Their Mg #s [100Mg/(Mg + Fe)] range from 40 to 60, indicating crystallization from relatively evolved magmas. They have LREE-depleted, chondrite-normalized REE diagrams, suggesting a depleted mantle source. These basaltic rocks have slightly negative Nb- and Ti-anomalies, suggesting that the Xigaze ophiolite represents a fragment of mature MORB lithosphere modified in a suprasubduction zone environment. The mantle peridotites at Luqu are high depleted with low CaO (0.3-1.2 wt%) and Al 2O 3 (0.04-0.42 wt%). They display V-shaped, chondrite-normalized REE patterns with (La/Gd) N ratios ranging from 3.17 to 64.6 and (Gd/Yb) N from 0.02 to 0.20, features reflecting secondary metasomatism by melts derived from the underlying subducted slab. Thus, the geochemistry of both the basaltic rocks and mantle peridotites suggests that the Xigaze ophiolite formed in a suprasubduction zone. Both the diabases and basalts have Pd/Ir ratios ranging from 7 to 77, similar to MORB. However, they have very low PGE abundances, closely approximating the predicted concentration in a silicate melt that has fully equilibrated with a fractionated immiscible sulfide melt, indicating that the rocks originated from magmas that were S-saturated before eruption. Moderate degrees of partial melting and early precipitation of PGE alloys explain their high Pd/Ir ratios and negative Pt-anomalies. The mantle peridotites contain variable amounts of Pd (5.99-13.5 ppb) and Pt (7.92-20.5 ppb), and have a relatively narrow range of Ir (3.47-5.01 ppb). In the mantle-normalized Ni, PGE, Au and Cu diagram, they are relatively rich in Pd and depleted in Cu. There is a positive correlation between CaO and Pd. The Pd enrichment is possibly due to secondary enrichment by metasomatism. Al 2O 3 and Hf do not correlate with Ir, but show positive variations with Pt, Pd and Au, indicating that some noble metals can be enriched by metasomatic fluids or melts carrying a little Al and Hf. We propose a model in which the low PGE contents and high Pd/Ir ratios of the basaltic rocks reflect precipitation of sulfides and moderate degrees of partial melting. The high Pd mantle peridotites of Xigaze ophiolites were formed by secondary metasomatism by a boninitic melt above a subduction zone.

Chen, Genwen; Xia, Bin

2008-04-01

122

Microbial Paleontology, Mineralogy and Geochemistry of Modern and Ancient Thermal Spring Deposits and Their Recognition on the Early Earth and Mars"  

NASA Technical Reports Server (NTRS)

The vision of this project was to improve our understanding of the processes by which microbiological information is captured and preserved in rapidly mineralizing sedimentary environments. Specifically, the research focused on the ways in which microbial mats and biofilms influence the sedimentology, geochemistry and paleontology of modem hydrothermal spring deposits in Yellowstone national Park and their ancient analogs. Toward that goal, we sought to understand how the preservation of fossil biosignatures is affected by 1) taphonomy- the natural degradation processes that affect an organism from the time of its death, until its discovery as a fossil and 2) diagenesis- longer-term, post-depositional processes, including cementation and matrix recrystallization, which collectively affect the mineral matrix that contains fossil biosignature information. Early objectives of this project included the development of observational frameworks (facies models) and methods (highly-integrated, interdisciplinary approaches) that could be used to explore for hydrothermal deposits in ancient terranes on Earth, and eventually on Mars.

Farmer, Jack D.

2004-01-01

123

Processes controlling trace element geochemistry of Arabian Sea sediments during the last 25,000 years  

Microsoft Academic Search

Thirty seven deep-sea sediment cores from the Arabian Sea were studied geochemically (49 major and trace elements) for four time slices during the Holocene and the last glacial, and in one high sedimentation rate core (century scale resolution) to detect tracers of past variations in the intensity of the atmospheric monsoon circulation and its hydrographic expression in the ocean surface.This

Frank Sirocko; Dieter Garbe-Schönberg; Colin Devey

2000-01-01

124

Trace element geochemistry of the Keana brines field, middle Benue trough, Nigeria.  

PubMed

A trace elements study of various samples from the Keana brines field, middle Benue Trough was carried-out to determine the extent to which Pb-Zn-S and BaSO(4) mineralisations have affected the quality of the brines and the waters in the area. Different sample media such as well-water, pond water, brine spring pool water, stream water, stream sediments etc. were analysed. Geochemical results show that Cu, Zn, Pb, As and S are concentrated in the waters (0.3, 0.36, 0.05, 0.07 and 1 1.5 ppm respectively). These elements are more concentrated in both the spring and pond waters, suggesting that the spring water could have acted as the transport medium for these elements released from deep-seated sources. Transitions elements (Ti, V, Cr, Fe, Co, Ni and Sr) are concentrated in the waters. Compared to the World Health Organization (WHO) admissible limits, the well waters present very high concentrations in Cd (0.56 ppm) and Sb (0.40 ppm) (200x and 70x WHO admissible values respectively). There is a preferential concentration of transition elements (Ti, V, Fe, Co and Ni) in the sediments (41.38, 362, 52.21, 269 and 54 ppm respectively) than in the waters (0.70, 0.05, 5.6, 0.04 and 0.02 ppm respectively). Similarly, Cu, Zn, Pb and As are concentrated in the sediments (44, 72, 41 and 14 ppm respectively). The concentrations of transition elements (Ti, V, Cr, Fe, Co and Ni) in the refined salt were highly elevated (784, 363, 283, 105, 59.2 and 42.6 ppm respectively) (7000-10,000x well water). Similarly, the concentrations of As, Pb, Br and Sr in the refined salt were also alarming (11.6, 16.4, 16.4 and 122 ppm respectively), (1000, 700, 3000 and 20,000x well water values respectively). S on the other hand is absent. One of the striking features is the absence of I, Cd, Sb and Se in the refined salt crystals which were detected in the waters and the brines. Compared to WHO admissible values, the refined salt crystal concentrations for Ni (426 ppm) and Cr (283 ppm) were also very high (2000x WHO values respectively) and to a lesser extent Cu (26.9 ppm) and Zn (21.7 ppm) (12 and 7x WHO values respectively). PMID:16027968

Lar, U A; Sallau, A K

2005-12-01

125

Rare earth elements in scleractinian cold-water corals  

NASA Astrophysics Data System (ADS)

The Rare Earth Elements (REE) have a great potential to trace continental input, particle scavenging and the oxidation state of seawater. These REE are recorded in the skeleton of the cosmopolitan cold-water corals Lophelia pertusa. Here we use an online preconcentration ICP-MS method (Hathorne et al. 2012) to measure REE concentrations in seawater and associated cold-water coral carbonates in order to investigate their seawater origin. Scleractinian cold-water corals were collected in-situ and alive and with corresponding seawater samples covering from the European Continental Margin. The seawater REE patterns are characterized by the typical negative cerium anomaly of seawater, but are distinct for the northern Norwegian Margin and the Oslo Fjord, probably related to continental input. Initial results for the corresponding coral samples suggest that these distinct REE patterns of ambient seawater are recorded by the coral skeletons although some fractionation during incorporation into the aragonite occurs. This indicates that scleractinian cold-water corals can serve as a valuable archive for seawater derived REE signatures, as well radiogenic Nd isotope compositions. In a second step we analysed fossil coral samples from various locations, which were oxidatively and reductively cleaned prior to analysis. Initial results reveal that sediment-buried fossil (early Pleistocene to Holocene) coral samples from the Norwegian Margin and the Porcupine Seabight (Challenger Mound, IODP Site 1317) do not show the expected seawater REE patterns. In particular, the fossil coral-derived REE patterns lack a negative cerium anomaly suggesting that fossil coral-REE patterns do not represent ambient seawater. Thus, we suggest that the oxidative-reductive cleaning method widely used for cleaning of marine carbonates such as foraminifera prior to measurements of seawater-derived trace metal and isotope compositions are not sufficient for REE and Nd isotopes in sediment-buried coral-water corals and require alternative or additional approaches. Hathorne, E.C., B. Haley, T. Stichel, P. Grasse, M. Zieringer, and M. Frank (2012). Online preconcentration ICP-MS analysis of rare earth elements in seawater, Geochem. Geophys. Geosyst.,13, Q01020, doi:10.1029/2011GC003907. .

Raddatz, J.; Liebetrau, V.; Hathorne, E. C.; Rüggeberg, A.; Dullo, W.; Frank, M.

2012-12-01

126

Geochemical behavior of rare earth elements and other trace elements in the Amazon River  

NASA Astrophysics Data System (ADS)

Rivers transport large amounts of dissolved and suspended particulate material from the catchment area to the oceans and are a major source of trace metals to seawater. The Amazon River is the world's largest river and supplies approximately 20% of the oceans' freshwater (Molinier et al., 1997). However, the behavior of trace elements, especially particle-reactive elements such as the rare earth elements (REE), within the river as well as in the estuary is not well constrained and rather little is known about their transport mechanisms. This study aims at understanding the transport properties of particle-reactive elements in the Amazon River and some of its major tributaries, including the Rio Solimões, Rio Negro, Tapajos, Xingu and Jari Rivers. Samples were taken at 12 stations, seven of which were located in the Amazon mainstream, while the other five stations sampled its tributaries. To account for the effects of variable discharge, the samples were collected during periods of high and low discharge. We present data for major and trace elements, including REE, of the dissolved and suspended load of these samples. First results indicate that the shale-normalized REE pattern of the dissolved load (filtered through 0.2 µm membranes) of the Amazon mainstream and the Rio Solimões confirm earlier studies (Elderfield et al., 1990; Gerard et al., 2003) and show an enrichment of the middle REE relative to the light and heavy REE (LaSN/GdSN: 0.25 - 0.32; GdSN/YbSN: 1.54 - 1.78). In contrast to the Amazon mainstream and the Rio Solimões, which are considered to be whitewater rivers, blackwater rivers, such as the Rio Negro, have a flat REE pattern with higher REE concentrations than whitewater rivers. The third water-type found in the Amazon Basin is clearwater, e.g. Rio Tapajos, with REE patterns in between those of the other two types, i.e. LaSN/GdSN: 0.55 - 0.70; GdSN/YbSN: 1.26 - 1.55. A similar behavior can be identified for other major and trace elements. While elements such as Ca, Mg, Sr or U are relatively high in whitewater rivers, their concentrations are generally lower in clearwater rivers and lowest in blackwater rivers. In contrast, elements including Si, Rb and Cs have their highest concentrations in blackwater rivers, intermediate concentrations in clearwater rivers and their lowest concentrations in whitewater river. [1] Elderfield H., Upstill-Goddard R. and Sholkovitz E.R. (1990): The rare earth elements in rivers, estuaries and coastal seas and their significance to the composition of ocean waters. Geochim.Cosmochim.Acta, 54, 971-991 [2] Gerard M., Seyler P., Benedetti M.F., Alves V.P., Boaventura G.R. and Sondag, F. (2003): Rare earth elements in the Amazon basin. Hydrological Processes, 17, 1379-1392 [3] Molinier M., Guyot J.L., Callede J., Guimaraes V., Oliveira E. and Filizola N. (1997): Hydrologie du bassinamazonien. Evironment et développement en Amazonie brésiliènne, Thery H. (ed.), Berlin Publ., Paris; 24-41

Merschel, Gila; Bau, Michael; Dantas, Elton Luiz

2014-05-01

127

Processes controlling trace element geochemistry of Arabian Sea sediments during the last 25,000 years  

NASA Astrophysics Data System (ADS)

Thirty seven deep-sea sediment cores from the Arabian Sea were studied geochemically (49 major and trace elements) for four time slices during the Holocene and the last glacial, and in one high sedimentation rate core (century scale resolution) to detect tracers of past variations in the intensity of the atmospheric monsoon circulation and its hydrographic expression in the ocean surface. This geochemical multi-tracer approach, coupled with additional information on the grain size composition of the clastic fraction, the bulk carbonate and biogenic opal contents makes it possible to characterize the sedimentological regime in detail. Sediments characterized by a specific elemental composition (enrichment) originated from the following sources: river suspensions from the Tapti and Narbada, draining the Indian Deccan traps (Ti, Sr); Indus sediments and dust from Rajasthan and Pakistan (Rb, Cs); dust from Iran and the Persian Gulf (Al, Cr); dust from central Arabia (Mg); dust from East Africa and the Red Sea (Zr/Hf, Ti/Al). C org, Cd, Zn, Ba, Pb, U, and the HREE are associated with the intensity of upwelling in the western Arabian Sea, but only those patterns that are consistently reproduced by all of these elements can be directly linked with the intensity of the southwest monsoon. Relying on information from a single element can be misleading, as each element is affected by various other processes than upwelling intensity and nutrient content of surface water alone. The application of the geochemical multi-tracer approach indicates that the intensity of the southwest monsoon was low during the LGM, declined to a minimum from 15,000-13,000 14C year BP, intensified slightly at the end of this interval, was almost stable during the Bölling, Alleröd and the Younger Dryas, but then intensified in two abrupt successions at the end of the Younger Dryas (9900 14C year BP) and especially in a second event during the early Holocene (8800 14C year BP). Dust discharge by northwesterly winds from Arabia exhibited a similar evolution, but followed an opposite course: high during the LGM with two primary sources—the central Arabian desert and the dry Persian Gulf region. Dust discharge from both regions reached a pronounced maximum at 15,000-13,000 14C year. At the end of this interval, however, the dust plumes from the Persian Gulf area ceased dramatically, whereas dust discharge from central Arabia decreased only slightly. Dust discharge from East Africa and the Red Sea increased synchronously with the two major events of southwest monsoon intensification as recorded in the nutrient content of surface waters. In addition to the tracers of past dust flux and surface water nutrient content, the geochemical multi-tracer approach provides information on the history of deep sea ventilation (Mo, S), which was much lower during the last glacial maximum than during the Holocene. The multi-tracer approach—i.e. a few sedimentological parameters plus a set of geochemical tracers widely available from various multi-element analysis techniques—is a highly applicable technique for studying the complex sedimentation patterns of an ocean basin, and, specifically in the case of the Arabian Sea, can even reveal the seasonal structure of climate change.

Sirocko, Frank; Garbe-Schönberg, Dieter; Devey, Colin

2000-11-01

128

Geochemistry of organic carbon and trace elements in boreal stratified lakes during different seasons  

NASA Astrophysics Data System (ADS)

Our knowledge of chemical fluxes in the system rock-soils-rivers-ocean of boreal and glacial landscapes is limited by the least studied part, i.e., the river water transformation between the lake and the river systems. Dissolved organic carbon (DOC), nutrients, major and trace elements are being leached from soil profile to the river but subjected to chemical transformation in the lakes due to phytoplankton and bacterial activity. As a result, many lakes in boreal regions are quite different in chemical composition compared to surrounding rivers and demonstrate important chemical stratification. The main processes responsible for chemical stratification in lakes are considered to be i) diffusion fluxes from the sediment to the bottom water accompanied by sulfate reduction and methanogenesis in the sediments and ii) dissolution/mineralization of precipitating organic matter (mineral fraction, detritus, plankton pellets) in the bottom layer horizons under anoxic conditions. Up to present time, distinguishing between two processes remains difficult. This paper is aimed at filling this gap via detailed geochemical analysis of DOC and trace elements in the water column profiles of three typical stratified lakes of Arkhangelsk region in Kenozersky National Parc (64° N) in winter (glacial) and in summer period. Concentration of most trace elements (Li, B, Al, Ti, V, Cr, Ni, Co, Zn, As, Rb, Sr, Y, Zr, Mo, Sb, Ba, REEs, Th, U) are not subjected to strong variations along the water column, despite the presence of strong or partial redox stratification. Apparently, these elements are not significantly controlled by production/mineralization processes and redox phenomena in the water column, or the influence of these processes is not pronounced under the control by the allochtonous river water input. In particularly, the stability of titanium and aluminum concentration along the depth profile and their independence of iron behavior suggest the important control by dissolved organic matter. Therefore, organo-ferric colloids controlling petrogenic elements speciation in soil and river waters are being replaced by autochthonous organic colloids in the lake system. The same observation is true for some heavy metals such as nickel, copper and zinc, whereas cobalt, as limiting component, is being strongly removed from the photic zone or it is coprecipitating with manganese hydroxide. Results of the present work allow quantitative evaluation of the role of redox processes in the bottom horizons and organic detritus degradation in the creation of chemical stratification of small lakes with high DOC concentration. Further insights on geochemical migration of trace elements in lakes require : i) study of colloidal speciation using in-situ dialysis; ii) monitoring the annual and seasonal dynamics of redox processes and TE concentration variation along the profile; iii) quantitative assessment of bacterial degradation of suspended OM and Mn and Fe redox reactions along the depth profile; iv) setting the sedimentary traps for evaluation of suspended material fluxes, and, v) thorough study of chemical composition of interstitial pore waters.

Moreva, O. Y.; Pokrovsky, O. S.; Shirokova, L. S.; Viers, J.

2008-12-01

129

Potassium and other minor elements in Porites corals: implications for skeletal geochemistry and paleoenvironmental reconstruction  

NASA Astrophysics Data System (ADS)

We investigated how the K/Ca, Na/Ca, Mg/Ca, and Sr/Ca ratios of powders ground from Porites coral skeletons are changed by cumulative chemical treatments to the powders: first with distilled/deionized water (DDW), next with 30 % H2O2 and then with 0.004 mol l-1 HNO3. The K/Ca, Na/Ca, and Mg/Ca ratios were decreased with the DDW treatment and then increased with the H2O2 and HNO3 treatments; the Sr/Ca ratio was slightly decreased through the cumulative treatments, suggesting fine-scale (tens of ?m or less) elemental heterogeneities in the skeleton—K, Na, and Mg are significantly enriched at the skeletal surface and also at the center of calcification (COC); in contrast, the heterogeneity of Sr is very small. We suggest that the principal mechanisms of K incorporation into coral skeleton are (1) ion incorporation into lattice defects/distortions and (2) ion adsorption onto crystal discontinuities (including crystal-organic matter interfaces) as forms of K+ and KSO4 -. Furthermore, we measured the element/Ca ratios of a modern Porites coral skeleton along its growth direction at 2-mm intervals. Results showed that all the element/Ca ratios displayed annual cycles, that the K/Ca and Na/Ca ratios covaried with each other, and that the annual-minimum K/Ca and Na/Ca ratios coincided with the annual high-density band in the skeleton. It is unclear what environmental factors may cause the covarying annual cycles of the K/Ca and Na/Ca ratios; however, as a possible explanation, the cycles may be due not to environmental factors, but to a combined effect of (1) the K and Na enrichment at the COC, (2) annual bands of high- and low-density skeleton, and (3) mm-scale element/Ca measurements along the skeletal growth direction. This kind of effect on geochemical proxies of which the concentrations significantly differ between the COC and surrounding skeleton may generate false or distorted paleoenvironmental signals.

Mitsuguchi, T.; Kawakami, T.

2012-09-01

130

Element partitioning between magnesium silicate perovskite and ferropericlase: New insights into bulk lower-mantle geochemistry  

Microsoft Academic Search

In this study, we investigated iron–magnesium exchange and transition-metal trace-element partitioning between magnesium silicate perovskite (Mg,Fe)SiO3 and ferropericlase (Mg,Fe)O synthetised under lower-mantle conditions (up to 115 GPa and 2200 K) in a laser-heated diamond anvil cell. Recovered samples were thinned to electron transparency by focused ion beam and characterized by analytical transmission electron microscopy (ATEM) and nanometer-scale secondary ion mass spectroscopy (nanoSIMS).

Anne-Line Auzende; James Badro; Frederick J. Ryerson; Peter K. Weber; Stewart J. Fallon; Ahmed Addad; Julien Siebert; Guillaume Fiquet

2008-01-01

131

Summary of the research work of the Trace Elements Section, Geochemistry and Petrology Branch, for the period January 1-March 31, 1951  

USGS Publications Warehouse

This report summarized the research work of the Trace Elements Section, Geochemistry and Petrology Branch for the period January 1 - March 31, 1951. Work before that is summarized in an earlier report, "Summary of the research work of the Trace Elements Section, Geochemistry and Petrology Branch, for the period April 1, 1948 - December 31, 1950," by John C. Rabbitt (U.S. Geol. Survey Trace Elements Investigations Rept. 148, January 1951). This report will be referred to as TEIR 148. In TEIR 148 the purpose of each project was described and it is not thought necessary to repeat that material. The research work of the section consists of laboratory and related field studies in the following fields: 1. Mineralogic and petrologic investigations of radioactive rocks, minerals, and ores. 2. Investigations of chemical methods of analysis for uranium, thorium, and other elements and compounds in radioactive materials, and related chemical problems. 3. Investigations of spectographic method of analysis for a wide variety of elements in radioactive materials. 4. Investigation of radiometric methods of analysis is applied to radioactive materials. It should be emphasized that the work undertaken so far is almost entirely in the nature of investigations supporting the field appraisal of known uraniferous deposits. A program of more fundamental research, particularly in the mineralogy and geochemistry of uranium, is now being drawn up and will be submitted for approval soon. This report does not deal with the routine analytical work of the Section nor the public-sample program. The analytical work will be summarized in a report to be issued after the end of fiscal year 1951, and a report on the public-sample program is in process. Special thanks are due members of the Section who are engaged in the research work and who have supplied material for this report, the Early Ingerson, Chief of the Geochemistry and Petrology Branch for his critical review, to Jane Titcomb of the editorial staff of the Section for editing the report, and to Virginia Layne of the same staff, for typing the manuscript and the multilith mats.

Rabbitt, John C.

1951-01-01

132

Summary of the research work of the Trace Elements Section, Geochemistry and Petrology Branch, for the period April 1, 1948-December 31, 1950  

USGS Publications Warehouse

This report summarizes the research work of the Trace Elements Section, Geochemistry and Petrology Branch, from the organization of the Section in April 1948 to December 31, 1950. The research undertaken thus far consists of laboratory and related field studies in the following fields: 1. Mineralogic and petrologic investigations of radioactive rocks, minerals, and ores. 2. Investigations of chemical methods of analysis for uranium, thorium, and other elements and compounds in radioactive materials, and related chemical problems. 3. Investigations of spectrographic methods of analysis for a wide variety of elements in radioactive materials. 4. Investigations of radiometric methods of analysis as applied to radioactive materials. It should be emphasized that the work undertaken thus far, described under the headings "Future work", is almost entirely in the nature of investigations supporting the field appraisal of known important uraniferous deposits. A comprehensive program of more fundamental research was submitted in April 1949 in a report entitled "Proposed program of desirable research in the geochemistry of uranium," but funds for this work have not been authorized. It is hoped, however, that funds to support basic research of the type indicated in that report may be available in the future. This report does not cover the analytical work of the Section nor the public-sample program. The analytical work has been summarized for the fiscal year 1950 in the report, "Numerical summary of the analytical work of the Trace Elements Section, Geochemistry and Petrology Branch, for the fiscal year 1950," by John C. Rabbit, U.S. Geol. Survey Trace Elements Memorandum Rept. 174, October 1950. A report on the public-sample program is in preparation. Much of the material in this report has been paraphrased from reports prepared by members of the Section. My special thanks are due them; to Earl Ingerson, chief of the Geochemistry and Petrology Branch of the Survey, for his critical review; to my secretary, Marie Woolihan, for her aid in collecting material; and to Virginia Layne of the editorial staff of the Section for typing the manuscript and the multilith mats.

Rabbitt, John C.

1951-01-01

133

Spectroscopy of Luminescent Crystals Containing Rare Earth Elements  

NASA Astrophysics Data System (ADS)

We have studied the spectroscopy of luminescent crystals containing rare earth elements such as KEuGe_2O_6, Cs_3EuSi_6O_{15}, K_4[(UO_2)Eu_2(Ge_2O_7)_2], and R_2(C_8H_{10}O_4)_3 (R= Y, Tb, or Eu). The emission and excitation spectra of these compounds were recorded at ambient temperature. These spectra are consistent with the structures which were determined by single crystal X-ray diffraction. Crystals containing hybrid luminescent centers were also synthesized and interesting energy transfer mechanisms were observed. For example, dramatic luminescence quenching was found in KEu_xNd_{1-x}Ge_2O_6 (x= 0.98, 0.96, 0.94, and 0.84) as well as in Cs_3Eu_{0.98}Nd_{0.02}Si_6O_{15}, while different compositions of Y_xEu_yTb_{2-x-y}(C_8H_{10}O_4)_3 exhibit different emission colors. Emission lifetimes were also measured for these compounds, and the results shed light on the energy transfer mechanisms. Detailed results of our research will be presented. P.-L. Chen, P.-Y. Chiang, H.-C. Yeh, B.-C. Chang, and K.-H. Lii, Dalton Trans., 1721 (2008). M.-Y. Hung, Y.-H. Chen, B.-C. Chang, and K.-H. Lii, Chem. Mater. 17, 5743 (2005).

Chen, Meng-Ling; Lii, Kwang-Hwa; Chang, Bor-Chen

2013-06-01

134

Trace element geochemistry of Jurassic coals from Eastern Black Sea Region, NE-Turkey  

SciTech Connect

The majority of coal deposits in the world are of Carboniferous and Tertiary age but Jurassic coals are seldom present. They are also exposed in northern Turkey and occur both at the lower and upper sections of the Liassic-Dogger volcanic- and volcani-clastic series. The coals at the base of the Jurassic units are characterized by higher Ba, Th, Zr, and Cr-Ni and lower S values than those at the top of the units, indicating, in general, laterally consistent trace element contents. The vertical distribution of trace elements in individual coal seams is also rather consistent. The B contents of coals from the Godul and Norsun areas vary from 1.5 to 4.3 ppm whereas those from the Alansa area are in the range of 95 to 138 ppm. This suggests that the coals in the Godul and Norsun areas were deposited in a swamp environment inundated by the sea from time to time, whereas coals of the Alansa were deposited in a saline environment.

Cebi, F.H.; Korkmaz, S.; Akcay, M. [Karadeniz Technical University, Trabzon (Turkey). Dept. of Geological Engineering

2009-07-01

135

Effect of Rare Earth Elements on Isothermal Transformation and Microstructures in 20Mn Steel.  

National Technical Information Service (NTIS)

The effect of rare earth elements on the isothermal transformation and microstructures in 20Mn steel is investigated by means of metallography and dilatometry. Rare earth elements decrease both the incubation period of pro-eutectoid ferrite and the rate o...

H. Liu D. H. Zheng Z. Y. Xu T. Y. Hsu

1995-01-01

136

Preliminary Assessment of Rare Earth Element Contents of Niger Delta Oils  

Microsoft Academic Search

A preliminary study of the rare earth element contents of some Niger Delta oils was carried out to evaluate their influence on petroleum system of the Niger Delta Basin. The oil samples were obtained from an onshore field in the Niger Delta and analyzed using Inductively Coupled Plasma Mass Spectrometric (ICP-MS) analytical technique. Four Light Rare Earth Elements (LREE), La,

A. Akinlua; T. R. Ajayi; B. B. Adeleke

2006-01-01

137

Presolar SiC Grains and Rare Earth Element Production in AGB Stars  

Microsoft Academic Search

The relative abundances of many isotopes of the rare earth elements are strongly affected by s-process nucleosynthesis in low-mass asymptotic giant branch (AGB) stars. We briefly explore the nucleosynthesis of the rare earth elements in AGB stars and their implications for measurements of presolar SiC grains from those stars.

Andrew M. Davis; Roberto Gallino

2008-01-01

138

Special glassy materials doped with rare-earth elements for fiber optics  

Microsoft Academic Search

Lead-bismuth-gallium-cadmium glasses doped with rare earths elements have been investigated. Certain optical properties of the glasses have been determined. The results of luminescence investiations in the form of absorption and luminescence spectra are presented, and the quantum yields as well as the calculated and measured luminescence lifetimes of the particular rare earths elements in the matrix of the examined glasses

Jan Wasylak; Dominik Dorosz; Jan Kucharski; Jan Kityk

2003-01-01

139

Light elements in the Earth's core: Fe3X compounds  

NASA Astrophysics Data System (ADS)

The nature of the light element (or elements) of the core has been the subject of considerable speculation, because of its bearing on the overall bulk composition of the earth, the conditions under which the core formed, the temperature regime in the core and the continuing process of core-mantle reaction. The correct thermodynamical and thermochemical properties of iron alloyed with any of the potential major candidate light elements - sulfur, carbon and silicon - are described along solid solutions. At least at low pressures, one of their major eutectic points is found at Fe3X compositions. Here we study in detail the compressibility and elasticity of these phases, Fe3S, Fe3C and Fe3Si, up to inner core pressures. For this specific stoichiometry Fe - Me = 3 - 1, both the sulfide and the carbide present the cementite orthorhombic structure up to inner core pressures. They exhibit a gradual decrease of the residual magnetic moment, in ferromagnetic configuration. The spin transition occurs largely below the core conditions. The silicide behaves differently. Fe3Si is not stable as cementite and during the relaxation the structure naturally evolves into a standard face-centered cubic structure, where Si occupies every fourth site. The structure is ferromagnetic with non-vanishing spin even at inner core pressures. The density of all Fe3X compounds analyzed here is smaller than that of hexagonally-close packed (hcp) iron by about 10-15%. Fe3S and Fe3C have similar values of bulk modulus as hcp iron and show smaller values for the shear modulus. Fe3Si shows considerably smaller values for both elastic moduli. In terms of velocities, Fe3S presents the closest velocities to hcp iron from all the three Fe3X candidates in terms of both Vp and Vs. Fe3Si shows larger Vp than hcp iron by about 4%. The difference in Vs is on the order of 11%. Fe3C shows the largest difference. Both Vp and Vs of Fe3C are considerably smaller than of pure iron. However adding carbon to iron is not enough to decrease its velocities enough to match PREM, even if we consider a thermal correction of 5%.

Calderon, A. V.; Caracas, R.; Romero, A. H.

2010-12-01

140

Characterization of the Sukinda and Nausahi ultramafic complexes, Orissa, India by platinum-group element geochemistry  

USGS Publications Warehouse

Samples of 20 chromitite, 14 ultramafic and mafic rock, and 9 laterite and soil samples from the Precambrian Sukinda and Nausahi ultramafic complexes, Orissa, India were analyzed for platinum-group elements (PGE). The maximum concentrations are: palladium, 13 parts per billion (ppb); platinum, 120 ppb; rhodium, 21 ppb; iridium, 210 ppb; and ruthenium, 630 ppb. Comparison of chondrite-normalized ratios of PGE for the chromitite samples of lower Proterozoic to Archean age with similar data from Paleozoic and Mesozoic ophiolite complexes strongly implies that these complexes represent Precambrian analogs of ophiolite complexes. This finding is consistent with the geology and petrology of the Indian complexes and suggests that plate-tectonic and ocean basin developement models probably apply to some parts of Precambrian shield areas. ?? 1985.

Page, N. J.; Banerji, P. K.; Haffty, J.

1985-01-01

141

Platinum-group element geochemistry of zoned ultramafic intrusive suites, Klamath Mountains, California and Oregon.  

USGS Publications Warehouse

Analyses for platinum-group elements of the varied rock suites of three Alaskan-type ultramafic to mafic multi-intrusive bodies are reported. Ir and Ru are less than analytical sensitivities of 100 and 20 ppb; Rh is less than or near 1 ppb. Average Pd assays vary among the rocks within intrusive complexes and between the three complexes (6.3, 13.7, 36.4 ppb); average Pt assays vary little among the same samples (27.9, 60.9, 34.0 ppb). Statistically adjusted Pt/(Pt + Pd) ratios increase in each suite from gabbro through clinopyroxenite to olivine-rich rocks, possibly owing to Pd fractionation.-G.J.N.

Gray, F.; Page, N. J.; Carlson, C. A.; Wilson, S. A.; Carlson, R. R.

1986-01-01

142

Major, trace element and stable isotope geochemistry of synorogenic breccia bodies, Ellsworth Mountains, Antarctica  

USGS Publications Warehouse

Cambrian carbonates in the Heritage Range of the Ellsworth Mountains, West Antarctica host a series of carbonate-rich breccia bodies that formed contemporaneously with the Permian Gondwanide orogen. The breccia bodies had a three-stage genesis, with the older breccias containing Cambrian limestone (and marble) clasts supported by calcite, whereas the younger breccias are nearly clast-free and composed entirely of matrix calcite. Breccia clasts, calcite matrix and detrital matrix samples were analyzed using x-ray fluorescence (major and trace elements), x-ray diffraction, and stable isotopes (C, O) and suggest that the breccias formed as part of a closed geochemical system, at considerable depth, within the Cambrian limestone host as the Ellsworth Mountains deformed into a fold-and-thrust belt along the margin of Gondwana

Craddock, J.P.; McGillion, M.S.; Webers, G.F.

2007-01-01

143

Trace element geochemistry of coals from the Southern Cantabrian Zone (NW Spain): preliminary results  

NASA Astrophysics Data System (ADS)

Bituminous to anthracite coals from three small Stephanian intramontane coal-bearing basins (La Magdalena, Cinera-Matallana and Sabero) located along the Sabero-Gordón fault line strike-slip systems of the Southern Cantabrian Zone (SCZ) were examined. Coal rank expressed as mean vitrinite reflectance values of these Stephanian coals is in the range 0.72-3.96%. The vitrinite maceral group exceeds 72 vol. % in all of the coals. The coals are characterized by relatively variable contents of mineral matter and coal-ash. The mineral matter comprises, in the main, clay minerals, carbonates, sulphides and quartz. The coals exhibit medium-high concentrations (see for comparison Ronov et al. 1990; Kabata-Pendias, Pendias 1999; Ketris, Yudovich 2009) of the following elements (in ppm): ?REE (53-205), Ba (300-900), As (11-57), Zn (<50-150), Cr (10-160), Rb (50-145), Co (5-26), Sc (2-24.6), Ce (17-99), Yb (1.3-4.5), Th (2.4-11.9) and U (1.1-8.1), Br (<1-14), Cs (<2-9), Eu (<0,3-1.5), Lu (0.11-0.85) and Sb (0.8-4.8), and relatively low concentrations of Sm (0.6-6.6) and Ta (<1-2). They are also characterised by relatively high Th/U values (1.31-2.29). LREE/HREE values fall in the range 24-44 (average - 30). In contrast, concentrations of Au, Ag, Hg, Ir, Ni, Se, Sn, Sr, and W are below detection limits for the applied INAA method. As the concentrations of elements are significantly higher in coal-ash, most are likely related to mineral matter in the coals.

Botor, Dariusz

2011-01-01

144

Carbonatite and alkaline intrusion-related rare earth element deposits–A deposit model  

USGS Publications Warehouse

The rare earth elements are not as rare in nature as their name implies, but economic deposits with these elements are not common and few deposits have been large producers. In the past 25 years, demand for rare earth elements has increased dramatically because of their wide and diverse use in high-technology applications. Yet, presently the global production and supply of rare earth elements come from only a few sources. China produces more than 95 percent of the world's supply of rare earth elements. Because of China's decision to restrict exports of these elements, the price of rare earth elements has increased and industrial countries are concerned about supply shortages. As a result, understanding the distribution and origin of rare earth elements deposits, and identifying and quantifying our nation's rare earth elements resources have become priorities. Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of rare earth elements. The general mineral deposit model summarized here is part of an effort by the U.S. Geological Survey's Mineral Resources Program to update existing models and develop new descriptive mineral deposit models to supplement previously published models for use in mineral-resource and mineral-environmental assessments. Carbonatite and alkaline intrusion-related REE deposits are discussed together because of their spatial association, common enrichment in incompatible elements, and similarities in genesis. A wide variety of commodities have been exploited from carbonatites and alkaline igneous rocks, such as rare earth elements, niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium. Other enrichments include manganese, strontium, tantalum, thorium, vanadium, and uranium.

Verplanck, Philip L.; Van Gosen, Bradley S.

2011-01-01

145

Mineralogy, petrology, and trace element geochemistry of the Johnstown meteorite - A brecciated orthopyroxenite with siderophile and REE-rich components  

NASA Technical Reports Server (NTRS)

The compositional and petrologic characteristics of the Johnstown meteorite show it to contain uncontaminated and unbrecciated orthopyroxenite clasts of cumulative origin that (1) must have undergone subsolidus recrystalization, (2) are parental to the brecciated matrix, and (3) show no evidence of a xenolithic, meteoritic contribution to the matrix except for contamination by the projectile which crushed it on impact. The trapped liquid was not introduced in the impact process. The variability of such trace elements as the light rare earth elements, and the presence of plagioclase and olivine in only one of the thin sections studied, demonstrates the heterogeneity of coarse-grained diogenites on a millimeter scale and the difficulty of obtaining representative samples of such meteorites. The data presented indicate that this meteorite is a monominct breccia.

Floran, R. J.; Prinz, M.; Hlava, P. F.; Keil, K.; Spettel, B.; Waenke, H.

1981-01-01

146

Effect of melt–rock interaction on geochemistry in the Kudi ophiolite (western Kunlun Mountains, northwestern China): implication for ophiolite origin  

Microsoft Academic Search

Major, trace and rare earth elements (REE), and platinum group elements (PGE) geochemistry have been studied for the Kudi ophiolite in the northwestern part of the western Kunlun Mountains, northwestern China, in order to determine the relationship between the mantle peridotites and mafic lavas and the origin of the ophiolite. The ophiolite consists of harzburgites, dunites, cumulate dunites, pyroxenites and

Zhihong Wang; Shu Sun; Quanlin Hou; Jiliang Li

2001-01-01

147

Identification And Interpretation Of Eclogite Protoliths Using Immobile Element Geochemistry: Some New Methodologies  

NASA Astrophysics Data System (ADS)

Methodologies for fingerprinting metabasalts have been applied to eclogites with mixed success. Some, including Alpine examples famously studied by Gary Ernst >30 years ago, have been successfully assigned to tectonic settings and the results used to understand the now-disappeared ocean and its margins. Others, however, present two particular, well-documented problems: 1) many are cumulates rather than lavas and so have very low abundances of some elements as well as non-liquid compositions; 2) the subduction and exhumation processes can lead to infiltration of the protolith by subduction- and crustally-derived fluids/melts before and after eclogite-facies metamorphism and so impart apparent subduction or continental character even when none existed. Here we demonstrate new methodologies for dealing with these issues, taking as an example the eclogites from the Chinese Continental Scientific Drilling (CCSD) Deep Borehole. We adopt a set of immobile element proxies that highlight the presence and behaviour of particular cumulate phases (e.g. Cr for chromite, Ni for olivine, Sc,V for clinopyroxene, Ti,V for oxide, Ga for plagioclase, P and Zr for apatite and zircon, Nb for interstitial melt). Using a training data set from well-studied cumulate sequences such as Bushveld and Skaergaard, we can assign protolith rock names on the basis of these proxy elements. Variation diagrams enable us identify the crystallization sequence of the plutonic protolith, itself a function of the original tectonic setting. For example, the Borehole contains a thick, eclogite-facies cumulate sequence which we can reconstruct in detail as a layered complex containing cumulate dunite and peridotite, mela-troctolite, troctolite, gabbro, ferrogabbro, ferrodiorite, quartz-diorite and tonalite. The iron enrichment and inferred saturation sequence of chr+ol-plag-cpx-mt-ap-zr are characteristic of low-oxygen fugacity, tholeiitic MORB and continental margin intrusions. In this, and more easily in other, smaller sill- and dyke-like bodies, we can use these proxy diagrams to identify rocks representative of liquid (non-cumulate) compositions, equivalent to the chilled facies of classic intrusions. Although these also follow fluid- and melt-infiltration vectors, especially around silica-rich rocks which reached melting temperatures, a small number of unmodified liquid compositions can be identified. These allow the setting to be determined using Th-Nb-Ti-Yb systematics. In this case, the data mostly plot in the centre of the MORB-OIB array on a Th/Yb-Nb-Yb plot indicating undepleted mantle. Some samples plot to higher Th/Yb indicating limited crustal assimilation. The samples plot in the MORB, rather than OIB, field on a Ti/Yb-Nb/Yb plot indicating shallow-melting indicative of thin lithosphere. Thus, an origin at a volcanic-rifted continental margin may be inferred. This procedure can also be applied to the debate over the origin and settings of eclogite inclusions in kimberlites.

Pearce, J. A.; Robinson, P.; Yang, J.

2011-12-01

148

Deciphering The Sources Of Cenozoic Volcanism In Central Mongolia Using Trace Element And Isotope Geochemistry  

NASA Astrophysics Data System (ADS)

One of the largest regions of Cenozoic intra-plate volcanism stretches across central Asia from the Baikal Rift in Siberia, through central Mongolia to China. In Mongolia this is expressed as numerous small-volume alkali-basaltic cones and lavas, erupted since ca. 30 Ma. Currently, accepted models of melt generation for intraplate magmatism, such as mantle plumes, lithospheric extension and convective removal of the lithosphere, are difficult to reconcile with some aspects of volcanism and tectonics in this region. A suite of basalts erupted across an area of Cenozoic uplift in central Mongolia, known as the Hangai Dome, has been analysed for trace elements and Sr-Nd-Pb isotopes. New Pb isotope data were collected by double spike MC-ICP-MS at the Open University and have a long-term 2? reproducibility better than 175 ppm for NBS 981. These data suggest progressive mixing between two distinct source regions in the genesis of the Hangai basalts. Older basalts, previously dated at 5.91 ± 0.02 Ma (Barry et al., 2003), are derived from a component with an asthenospheric signature similar to depleted Indian MORB. Younger basalts are increasingly mixed with a component with lower Pb and Sr ratios and an enriched trace element signature, which is similar in composition to some lamproites erupted in the western USA (Mirnejad and Bell, 2006). This represents a transition from asthenospheric to lithospheric melting through time. Furthermore, studies on mantle xenoliths from across the Hangai Dome indicate an elevated geotherm under the centre of the dome and significantly cooler conditions at its margins, interpreted to be the result of mantle upwellling (Harris et al., in review). Further numerical modelling will assess the relative contributions from lithospheric and asthenospheric sources in the genesis of these basalts, and contribute to understanding this enigmatic volcanic region. Barry, T. L., Saunders, A. D., Kempton, P. D., Windley, B.F., Pringle, M.S., Dorjnamjaa, D. and Saander, S. (2003)., J. Petrol. 44 55-91 Harris, N., Hunt, A., Parkinson, I., Tindle, A., Yondon, M. and Hammond, S. (2009) in review Mirnejad, H. And Bell, K (2006)., J. Petrol. 47 2463-2489

Hunt, A. C.; Parkinson, I. J.; Harris, N.; Rogers, N. W.; Barry, T.; Yondon, M.

2009-12-01

149

Rare earth geochemistry of Lewisian granulite-facies gneisses, northwest Scotland: Implications for the petrogenesis of the Archaean lower continental crust  

Microsoft Academic Search

Rare earth element (REE) data, together with data for major elements and 14 other trace elements, are presented for ultramafic, mafic, intermediate, tonalitic, trondhjemitic, anorthositic and microline gneisses, representative of the range of rock types making up the 2.9-b.y. Lewisian granulite complex of northwest Scotland. The data are used to constrain petrogenetic models for the Archaean lower crust. Ultramafic gneisses

Barry L. Weaver; John Tarney

1980-01-01

150

Trace element cycling in a subterranean estuary: Part 1. Geochemistry of the permeable sediments  

NASA Astrophysics Data System (ADS)

Subterranean estuaries are characterized by the mixing of terrestrially derived groundwater and seawater in a coastal aquifer. Subterranean estuaries, like their river water-seawater counterparts on the surface of the earth, represent a major, but less visible, hydrological and geochemical interface between the continents and the ocean. This article is the first in a two-part series on the biogeochemistry of the subterranean estuary at the head of Waquoit Bay (Cape Cod, MA, USA). The pore-water distributions of salinity, Fe and Mn establish the salt and redox framework of this subterranean estuary. The biogeochemistry of Fe, Mn, P, Ba, U and Th will be addressed from the perspective of the sediment composition. A second article will focus on the groundwater and pore-water chemistries of Fe, Mn, U and Ba. Three sediment cores were collected from the head of Waquoit Bay where the coastal aquifer consists of permeable sandy sediment. A selective dissolution method was used to measure the concentrations of P, Ba, U and Th that are associated with "amorphous (hydr)oxides of iron and manganese" and "crystalline Fe and Mn (hydr)oxides." The deeper sections of the cores are characterized by large amounts of iron (hydr)oxides that are precipitated onto organic C-poor quartz sand from high-salinity pore waters rich in dissolved ferrous iron. Unlike Fe (hydr)oxides, which increase with depth, the Mn (hydr)oxides display midcore maxima. This type of vertical stratification is consistent with redox-controlled diagenesis in which Mn (hydr)oxides are formed at shallower depths than iron (hydr)oxides. P and Th are enriched in the deep sections of the cores, consistent with their well-documented affinity for Fe (hydr)oxides. In contrast, the downcore distribution of Ba, especially in core 3, more closely tracks the concentration of Mn (hydr)oxides. Even though Mn (hydr)oxides are 200-300 times less abundant than Fe (hydr)oxides in the cores, Mn (hydr)oxides are known to have an affinity for Ba which is many orders of magnitude greater than iron (hydr)oxides. Hence, the downcore distribution of Ba in Fe (hydr)oxide rich sediments is most probably controlled by the presence of Mn (hydr)oxides. U is enriched in the upper zones of the cores, consistent with the formation of highly reducing near-surface sediments in the intertidal zone at the head of the Bay. Hence, the recirculation of seawater through this type of subterranean estuary, coupled with the abiotic and/or biotic reduction of soluble U(VI) to insoluble U(IV), leads to the sediments acting as a oceanic net sink of U. These results highlight the importance of permeable sediments as hosts to a wide range of biogeochemical reactions, which may be impacting geochemical budgets on scales ranging from coastal aquifers to the continental shelf.

Charette, Matthew A.; Sholkovitz, Edward R.; Hansel, Colleen M.

2005-04-01

151

Rare earth element budgets in subduction-zone fluids  

NASA Astrophysics Data System (ADS)

Subduction zone fluids play a fundamental role in the geochemical cycle of the Earth. The nature and composition of these fluids are determined by complex processes and still poorly understood. As a result of a variety of metasomatic and partial melting events, arc-related magmas display a typical trace element abundance spectrum, in which the rare earth elements' (REE) signature is an important record of petrogenetic processes. Therefore, investigating the behavior of REE in fluids at high pressure (P) and temperature (T) conditions is crucial for constraining fluid composition, as well as understanding subduction-zone processes in general. However, up to date, the experimental studies on REE solubility and speciation are limited to quite low P-T conditions (300 °C, saturated water vapor pressure) [1]. The theoretical predictions of the stability of REE complexes have been performed up to 350 °C [2] and 1000 °C, 0.5 GPa [3] by the extrapolation of thermodynamic data obtained at ambient conditions. In this study we present new experimental data on REE silicate (REE2Si2O7) solubility in aqueous quartz saturated fluids, containing various ligands, at conditions relevant for subducting slabs (600, 700, 800 °C, 2.6 GPa). The aim of the experiments was to investigate the relative effect of temperature and ligands on the solubility of REE. The experiments were conducted in an end-loaded piston-cylinder apparatus and the fluids were in situ sampled at P-T in the form of primary fluid inclusions in quartz [4]. The gold capsule was typically loaded with a chip of synthetic REE silicate (La,Nd,Gd,Dy,Er,Yb)2Si2O7, an aqueous fluid (~20 wt.%) and a piece of natural quartz. During the experiment (24-48 h) a thermal gradient along the capsule promoted intensive dissolution of quartz at the hottest part and precipitation of new quartz at the cooler part of the capsule, allowing the primary fluid inclusions to be trapped (~30-50 ?m). Rubidium and cesium were added to the fluid as the internal standards for LA-ICPMS analyses. The solubility of REE in quartz saturated water, free of additional ligands, increases more than an order of magnitude as temperature is increased from 600 °C to 800 °C. The effect of halogen ligands (Cl-, F-) on the solubility of REE was tested on experiments conducted at 800 °C. Addition of 1.5 m NaCl enhances the solubilities of all REE by a factor of 2 to 4 and induces moderate LREE/HREE fractionation; the La/Yb ratio increases by factor of 2. Unlike chlorine, the presence of fluorine ligands in the fluid (0.3 m NaF) promotes increase in HREE solubilities with almost no change in LREE solubilities compared to water, hence decreasing the La/Yb ratio by a factor of 2. The results of our experiments suggest that temperature plays an important role in mobilization of all REE by fluids. The presence of Cl- and F- ligands in the fluid shows opposing effects on the REE pattern: Cl- seems to be a more efficient ligand for LREE, while F- tends to form more stable complexes with HREE. [1] Migdisov A. A. et al., 2009, Geochim Cosmochim Acta, 73, 7087-7109 [2] Wood S. A. 1990b, Chem Geo., 82, 159-186 [3] Haas J. R. 1995, Geochim Cosmochim Acta, 59, 4329-4350 [4] Bali E. et al., 2011, Contrib Mineral Petrol, 161, 597-613

Tsay, A.; Zajacz, Z.; Sanchez-Valle, C.

2012-12-01

152

Major and trace element geochemistry of ilmenite suites from the Kimberley diamond mines, South Africa  

NASA Astrophysics Data System (ADS)

We have undertaken an electron microprobe and LA-ICP-MS study of ilmenites from Kimberley, South Africa, to understand better the mantle sources of ilmenite xenocrysts, key indicator minerals in kimberlite exploration. Among mantle xenoliths from Kimberley mines, ilmenite occurs in the following rock types: MARID (Mica-Amphibole-Rutile-Ilmenite-Diopside), Granny Smith glimmerites (cpx-phlogopite-ilmenite), rutile -ilmenite rocks, dunites (olivine-ilmenite) and phlogopite orthopyroxenites. Using major, minor and trace elements we have created a preliminary classification scheme for Kimberley ilmenites. Our data allow distinction between four broad suites: MARID, Granny Smith/rutile, orthopyroxenites and dunites. MARID ilmenites are generally the lowest in MgO (5.3-15.21 wt %) and Al2O3 (<0.05 wt %) and highest in Fe2O3 (6.6-23.4 wt %) and those from the Granny Smith/rutile suite have high MgO contents in the narrow range (13.0-14.9 wt %), with Al2O3 in the range 0.2-0.6 wt% and low Fe2O3 (4.9-6.7 wt %) values. Ilmenites from orthopyroxenites mostly have intermediate MgO, Al2O3 and Fe2O3 contents (10.8 -13.5 wt%, 0.1-0.4 wt % and 9.8-10.4 wt%, respectively). Ilmenites from dunites range to high MgO and Cr2O3 values (5.01-15.49wt % and 0.07-6.5 wt % respectively). The range of Nb2O5 contents of the Granny Smith/rutile ilmenites is very restricted (0.07-0.14 wt %) whereas those of MARID, orthopyroxenites and dunites are in a much wider range (0.03-1.74 wt% Nb2O5). Ilmenites belonging to the dunite suite cluster in three different groups, based on their Mg, Cr and Nb contents. One of these groups has MgO and Cr2O3 values similar to those of the rutile and Granny Smith suites, while the other have lower MgO contents. The three suites can be somewhat distinguished on the basis of comparison of MgO vs. Cr2O3, Al2O3 vs. Nb2O5, FeO vs. Fe2O3 (calculated from stoichiometry) and Cu/W vs Co/Cu. Distinguishing between the rutile, Granny Smith and part of the dunite suite is extremely difficult due to extensive compositional overlap, suggesting that they have a common genesis perhaps forming in related metasomatic events. Trace element data are consistent with such a hypothesis. All three suites have V values in the 900 - 1200 ppm range, Zr contents that range from 300 to 550 ppm and similar Sn values (6.69 - 9.07 ppm). We have applied these preliminary distinctions to ilmenite xenocrysts fom the Wesselton, Bultfontein, Kampfersdam and Otto's Kopje Mines in Kimberley. For example, we infer that >75% of the ilmenites from Wesselton and Kampfersdam belong to the rutile/dunite/Granny Smith suite compared to Otto's Kopje where the majority belongs to the MARID, orthopyroxenite and dunite suites. Ilmenites from all suites are present in approximately equal proportions at Bultfontein.

Ene, V. V.; Schulze, D. J.

2013-12-01

153

Pb-Sr-He isotope and trace element geochemistry of the Cape Verde Archipelago  

NASA Astrophysics Data System (ADS)

New lead, strontium and helium isotopic data, together with trace element concentrations, have been determined for basalts from the Cape Verde archipelago (Central Atlantic). Isotopic and chemical variations are observed at the scale of the archipelago and lead to the definition of two distinct groupings, in keeping with earlier studies. The Northern Islands (Santo Antão, São Vicente, São Nicolau and Sal) present Pb isotopic compositions below the Northern Hemisphere Reference Line (NHRL) (cf. Hart, 1984), unradiogenic Sr and relatively primitive 4He/ 3He ratios. In contrast, the Southern Islands (Fogo and Santiago) display Pb isotopes above the NHRL, moderately radiogenic Sr and MORB-like helium signatures. We propose that the dichotomy between the Northern and Southern Islands results from the presence of three isotopically distinct components in the source of the Cape Verde basalts: (1) recycled ˜1.6-Ga oceanic crust (high 206Pb/ 204Pb, low 87Sr/ 86Sr and high 4He/ 3He); (2) lower mantle material (high 3He); and (3) subcontinental lithosphere (low 206Pb/ 204Pb, high 87Sr/ 86Sr and moderately radiogenic 4He/ 3He ratios). The signature of the Northern Islands reflects mixing between recycled oceanic crust and lower mantle, to which small proportions of entrained depleted material from the local upper mantle are added. Basalts from the Southern Islands, however, require the addition of an enriched component thought to be subcontinental lithospheric material instead of depleted mantle. The subcontinental lithosphere may stem from delamination and subsequent incorporation into the Cape Verde plume, or may be remnant from delamination just before the opening of the Central Atlantic. Basalts from São Nicolau reflect the interaction with an additional component, which is identified as oceanic crustal material.

Doucelance, Régis; Escrig, Stéphane; Moreira, Manuel; Gariépy, Clément; Kurz, Mark D.

2003-10-01

154

Attenuation of rare earth elements in a boreal estuary  

NASA Astrophysics Data System (ADS)

This study focuses on attenuation of rare earth elements (REE) when a boreal creek, acidified and loaded with REE and other metals as a result of wetland drainage, empties into a brackish-water estuary (salinity < 6‰). Surface water was collected in a transect from the creek mouth to the outer estuary, and settling (particulate) material in sediment traps moored at selected locations in the estuary. Ultrafiltration, high-resolution ICP-MS and modeling were applied on the waters, and a variety of chemical reagents were used to extract metals from the settling material. Aluminium, Fe and REE transported by the acidic creek were extensively removed in the inner/central estuary where the acidic water was neutralised, whereas Mn was relatively persistent in solution and thus redistributed to particles and deposited further down the estuary. The REE removal was caused by several contemporary mechanisms: co-precipitation with oxyhydroxides (mainly Al but also Fe), complexation with flocculating humic substances and sorption to suspended particles. Down estuary the dissolved REE pool, remaining after removal, was fractionated: the <1 kDa pool became depleted in the middle REE and the colloidal (0.45 ?m-1 kDa) pool depleted in the middle and heavy REE. This fractionation was controlled by the removal process, such that those REE with highest affinity for the settling particles became most depleted in the remaining dissolved pool. Modeling, based on Visual MINTEQ version 3.0 and the Stockholm Humic Model after revision and updating, predicted that the dissolved (<0.45 ?m) REE pool in the estuary is bound almost entirely to humic substances. Acid sulphate soils, the source of the REE and other metals in the creek water, are widespread on coastal plains worldwide and therefore the REE attenuation patterns and mechanisms identified in the studied estuary are relevant for recognition of similar geochemical processes and conditions in a variety of coastal locations.

Åström, Mats E.; Österholm, Peter; Gustafsson, Jon Petter; Nystrand, Miriam; Peltola, Pasi; Nordmyr, Linda; Boman, Anton

2012-11-01

155

Platinum group element geochemistry of komatiites from the Alexo and Pyke Hill areas, Ontario, Canada  

NASA Astrophysics Data System (ADS)

Thirty-three whole-rock drill core samples and thirteen olivine, chromite, and sulfide separates from three differentiated komatiite lava flows at Alexo and Pyke Hill, Canada, were analyzed for PGEs using the Carius tube digestion ID-ICP-MS technique. The emplaced lavas are Al-undepleted komatiites with ˜27% MgO derived by ˜50% partial melting of LILE-depleted Archean mantle. Major and minor element variations during and after emplacement were controlled by 30 to 50% fractionation of olivine Fo 93-94. The emplaced lavas are characterized by (Pd/Ir) N = 4.0 to 4.6, (Os/Ir) N = 1.07, and Os abundances of ˜2.3 ppb. Variations in PGE abundances within individual flows indicate that Os and Ir were compatible (bulk DOs,Ir = 2.4-7.1) and that Pt and Pd were incompatible (bulk DPt,Pd < 0.2) during lava differentiation, whereas bulk DRu was close to unity. Analyses of cumulus olivine separates indicate that PGEs were incompatible in olivine ( DPGEsOl-Liq = 0.04-0.7). The bulk fractionation trends cannot be accounted for by fractionation of olivine alone, and require an unidentified Os-Ir-rich phase. The composition of the mantle source (Os = 3.9 ppb, Ir = 3.6 ppb, Ru = 5.4 ppb, Pt and Pd = 5.7 ppb) was constrained empirically for Ru, Pt, and Pd; the Os/Ir ratio was taken to be identical to that in the emplaced melt, and the Ru/Ir ratio was taken to be chondritic, so that the absolute IPGE abundances of the source were determined by Ru. This is the first estimate of the PGE composition of a mantle source derived from analyses of erupted lavas. The suprachondritic Pd/Ir and Os/Ir of the inferred Abitibi komatiite mantle source are similar to those in off-craton spinel lherzolites, orogenic massif lherzolites, and enstatite chondrites, and are considered to be an intrinsic mantle feature. Bulk partition coefficients for use in komatiite melting models derived from the source and emplaced melt compositions are: DOs,Ir = 2.3, DRu = 1.0, DPt,Pd = 0.07. Ruthenium abundances are good indicators of absolute IPGE abundances in the mantle sources of komatiite melts with 26 to 29% MgO, as Ru fractionates very little during both high degrees of partial melting and lava differentiation.

Puchtel, Igor S.; Humayun, Munir; Campbell, Andrew J.; Sproule, Rebecca A.; Lesher, C. Michael

2004-03-01

156

Advancing Access, Attribution, and Integration of Earth & Ocean Science Data: Integrated Services of the Marine Geoscience Data System and the Geoinformatics for Geochemistry Program  

NASA Astrophysics Data System (ADS)

Development and operation of digital data collections are needed across all areas of the earth and ocean sciences to ensure access and preservation of data sets collected in support of earth and ocean sciences in order to maximize the return on research investments, while enabling verification of research results and contributing to new science initiatives. This is particularly true for data sets that are acquired at high cost, particularly in the marine environment, and that contain irreplaceable observations made of earth’s dynamic properties. The Marine Geoscience Data System (MGDS, www.marine-geo.org) and the Geoinformatics for Geochemistry Program (GfG, www.geoinfogeochem.org) have over the past decade developed, maintained, and operated community-driven data collections that support the preservation, discovery, retrieval, and analysis of a wide range of observational field and analytical data types from the marine and terrestrial environments, among them the PetDB database, the EarthChem data network, the Ridge2000 and MARGINS databases, the Antarctic and Southern Ocean Data System (ASODS), the Global Multi Resolution Topography Synthesis, and the System for Earth Sample Registration (SESAR). MGDS and GfG systems have been developed based on an active understanding of the practices, needs, and concerns of their user communities. They have engaged investigators in the design of the systems, seeking their feedback, and educating the community about responsibilities and benefits of scientific data management and sharing, and worked with funding agencies, editors, publishers, professional societies, and researchers to achieve broad community support, to proactively drive the development of community standards and best practices for data submission, data publication, data documentation, and data archiving, and to advance implementation. In a new formal partnership named IEDA (Integrated Earth Data Applications), the MGDS and GfG will be funded by the US National Science Foundation under a Cooperative Agreement to continue the operation of all MGDS and GfG data systems, while providing new integrated data services that will substantially enhance the utility of all data collection components, and improve data curation, interoperability and efficiency of operations. These will include an on-line service to improve ease of data submission across our user communities, a data publication service for scientists to publish their datasets with citable universal identifiers (DOIs), partnerships with institutions to ensure long-term archiving of data holdings, an authentication service for single sign-on to all systems, and operational services for shared vocabularies and to ease registration of common expeditions and geochemical datasets across our two systems.

Lehnert, K. A.; Carbotte, S. M.; Ferrini, V.; Arko, R. A.; Chan, S.; Ryan, W. B.

2010-12-01

157

Review of rare earth element concentrations in oil shales of the Eocene Green River Formation  

USGS Publications Warehouse

Concentrations of the lanthanide series or rare earth elements and yttrium were determined for lacustrine oil shale samples from the Eocene Green River Formation in the Piceance Basin of Colorado and the Uinta Basin of Utah. Unprocessed oil shale, post-pyrolysis (spent) shale, and leached shale samples were examined to determine if oil-shale processing to generate oil or the remediation of retorted shale affects rare earth element concentrations. Results for unprocessed Green River oil shale samples were compared to data published in the literature on reference materials, such as chondritic meteorites, the North American shale composite, marine oil shale samples from two sites in northern Tibet, and mined rare earth element ores from the United States and China. The Green River oil shales had lower rare earth element concentrations (66.3 to 141.3 micrograms per gram, ?g g-1) than are typical of material in the upper crust (approximately 170 ?g g-1) and were also lower in rare earth elements relative to the North American shale composite (approximately 165 ?g g-1). Adjusting for dilution of rare earth elements by organic matter does not account for the total difference between the oil shales and other crustal rocks. Europium anomalies for Green River oil shales from the Piceance Basin were slightly lower than those reported for the North American shale composite and upper crust. When compared to ores currently mined for rare earth elements, the concentrations in Green River oil shales are several orders of magnitude lower. Retorting Green River oil shales led to a slight enrichment of rare earth elements due to removal of organic matter. When concentrations in spent and leached samples were normalized to an original rock basis, concentrations were comparable to those of the raw shale, indicating that rare earth elements are conserved in processed oil shales.

Birdwell, Justin E.

2012-01-01

158

RARE EARTH ELEMENTS: A REVIEW OF PRODUCTION, PROCESSING, RECYCLING, AND ASSOCIATED ENVIRONMENTAL ISSUES  

EPA Science Inventory

Rare earth elements (REEs) are a group of 15 chemical elements in the periodic table, specifically the lanthanides. Two other elements, scandium and yttrium, have a similar physiochemistry to the lanthanides, are commonly found in the same mineral assemblages, and are often refe...

159

Rare Earth Elements: A Tool for Understanding the Behaviour of Trivalent Actinides in the Geosphere  

SciTech Connect

Rare earth element (REE) concentrations have been determined in groundwaters, granite and fracture fillings in a restored uranium mine. The granitoids normalized REE patterns of groundwaters show heavy rare earth elements (HREE)-enrichment and positive Eu anomalies. This suggests that the REE are fractionated during leaching from the source rocks by groundwaters. Preferential leaching of HREE would be consistent with the greater stability of their aqueous complexes compared to those of the light rare earth elements (LREE), together with the dissolution of certain fracture filling minerals, dissolution/alteration of phyllosilicates and colloidal transport. (authors)

Buil, Belen; Gomez, Paloma; Garralon, Antonio; Turrero, M. Jesus [Medioambiente, CIEMAT, Avda. Complutense 22, Madrid, 28040 (Spain)

2007-07-01

160

Rare Earth elements as sediment tracers in Mangrove ecosystems  

NASA Astrophysics Data System (ADS)

Rare earth elements have been widely used as geochemical source fingerprints of rocks and sediments to study processes involving cosmo-chemistry, igneous petrology, tectonic setting and for investigations of water-rock interactions and weathering processes including transport of weathering products to the oceans.Many studies have addressed the use of REEs in investigating the environmental impact of human activity and demonstrated that the REE natural distribution in sediment from densely industrialised and populated regions can be altered by anthropogenic influences.The coastal wetlands like Mangroves are ultimate sinks for all the material derived from the terrestrial and marine environment.The high productivity and low ratio of sediment respiration to net primary production gives mangrove sediments the potential for long-term sequestration of these pollutants/metals before reaching the coastal ocean. Geochemical study of REE in these sedimentary systems is useful for determining the nature of the biogeochemical processes. In particular, REE show a great sensitivity to pH changes, redox conditions and adsorption/ desorption reactions. So, they may be used as markers of discharge provenance, weathering processes, changes in environmental conditions in the water and sediments of Mangrove/wetland systems. Our study aims to establish the abundance, distribution and enrichment of REEs to track the sediment sources and biogeochemical processes occurring in the mangrove environment.Core sediments were collected from the different environmental settings within the Pichavaram mangrove area.Higher REE concentration in Pichavaram sediments indicated greater input from sources like terrestrial weathering and anthropogenic activities which in turn are affected by saline mixing and dynamic physico-chemical processes occurring in the mangrove environment. REE enrichment order was attributed to the alkaline pH (7-8.5) and reducing conditions prevailing in the mangrove environments leading to preferential removal of MREE and LREE by adsorption and precipitation as Fe-Mn oxy-hydroxides in sediments. PAAS normalised plots also depicted slightly convex sub-parallel shale like patterns with alike enrichment.The same characteristics have been observed for sediments for Kaveri River validating that the sediments brought down during fluvial transport, is the source of REE in Pichavaram. Strong positive Eu anomalies suggested prevalence of reducing conditions as well as it indicated source from the natural weathering of the post Archean charnockitic and gneissic terrain in the course of river Kaveri. Role of different mangroves species in controlling the REE distribution in sediments was also observed . Tidally influenced cores showed complexity of environment these sites were exposed to. Factor analysis delineated three main processes controlling REE distribution in Pichavaram, namely natural weathering, inherent physico-chemical processes and in-situ biogeochemical processes occurring in this hypersaline mangrove environment.

Ramanathan, A. L.; Swathi, S.

2013-05-01

161

Geochemistry of ultrahigh-pressure anatexis: fractionation of elements in the Kokchetav gneisses during melting at diamond-facies conditions  

NASA Astrophysics Data System (ADS)

The Kokchetav complex in Kazakhstan contains garnet-bearing gneisses that formed by partial melting of metasedimentary rocks at ultrahigh-pressure (UHP) conditions. Partial melting and melt extraction from these rocks is documented by a decrease in K2O and an increase in FeO + MgO in the restites. The most characteristic trace element feature of the Kokchetav UHP restites is a strong depletion in light rare earth elements (LREE), Th and U. This is attributed to complete dissolution of monazite/allanite in the melt and variable degree of melt extraction. In contrast, Zr concentrations remain approximately constant in all gneisses. Using experimentally determined solubilities of LREE and Zr in high-pressure melts, these data constrain the temperature of melting to ~1,000 °C. Large ion lithophile elements (LILE) are only moderately depleted in the samples that have the lowest U, Th and LREE contents, indicating that phengite retains some LILE in the residue. Some restites display an increase in Nb/Ta with respect to the protolith. This further suggests the presence of phengite, which, in contrast to rutile, preferentially incorporates Nb over Ta. The trace element fractionation observed during UHP anatexis in the Kokchetav gneisses is significantly different from depletions reported in low-pressure restites, where generally no LREE and Th depletion occurs. Melting at UHP conditions resulted in an increase in the Sm/Nd ratio and a decoupling of the Sm-Nd and Lu-Hf systems in the restite. Further subduction of such restites and mixing with mantle rocks might thus lead to a distinct isotopic reservoir different from the bulk continental crust.

Stepanov, Aleksandr S.; Hermann, Joerg; Korsakov, Andrey V.; Rubatto, Daniela

2014-05-01

162

FLUORESCENCE PROPERTIES OF As2S3 GLASS DOPED WITH RARE-EARTH ELEMENTS  

Microsoft Academic Search

Chalcogenide glasses doped with various rare-earth ions are extensively studied as potential materials for fiber optic amplifiers operating at 1.3 and 1.5 ?m telecommunication windows. The experimental results on optical absorption and photoluminescence of arsenic sulfide glasses and optical fibers doped with rare-earth elements (Pr3+, Sm3+, Er3+ and Dy3+) are presented. Near the absorption edge the rare-earth impurities affect strongly

M. Iovu; A. Andriesh; I. Culeac

163

Technical Information Resource on Rare Earth Elements Now Available to Public and Private Sector Stakeholders  

EPA Science Inventory

A new EPA technical information resource, ?Rare Earth Elements: A Review of Production, Processing, Recycling, and Associated Environmental Issues? has been produced as an introductory resource for those interested in learning more about REE mining and alternatives to meet demand...

164

Rare Earth Element Systematics in 48 R Chondrite Ca,Al-Rich Inclusions  

NASA Astrophysics Data System (ADS)

The compiled rare earth element systematics of 48 (including 32 new) Ca,Al-rich inclusions from seven R chondrites will be presented and implications for their formation and evolution will be discussed.

Horstmann, M.; Krause, J.; Berndt, J.; Bischoff, A.

2012-09-01

165

[Comparative study of the anticoagulant activity of dimethoxyphosphates of rare-earth elements].  

PubMed

It was shown in experiments on rabbits that dimethoxyphosphates of rare-earth elements injected intravenously displayed a marked anticoagulant activity. The highest effect was produced by compounds of neodymium, holmium, terbium, europium, thulium, dysprosium, and erbium. PMID:3758324

Novikova, N V; Lobanova, E G; Lebedeva, E N; Men'kov, A A; Galaktionova, O V

1986-01-01

166

Thermophysical Properties of Liquid and Supercooled Rare Earth Elements Measured by an Electrostatic Levitator  

Microsoft Academic Search

Thermophysical properties of several rare earth elements have been measured using electrostatic levitation techniques. The understanding of the nature and behavior of rare earth metals in their liquid phases requires accurate val- ues of their physical properties. However, keeping the samples in their liquid phases free from contamination long enough to carry out measurements represents a formidable challenge. This is

Takehiko ISHIKAWA; Junpei T. OKADA; Jianqiang LI; Paul-François PARADIS; Yuki WATANABE

167

Environmental Geochemistry  

NSDL National Science Digital Library

This resource is the homepage of an environmental geochemistry course that is taught by Dr. David Sherman at the University of Bristol. The course begins with geochemistry basics such as oxidation-reduction and acid-base reactions, and progresses to environmental topics such as heavy metals, landfill chemistry, organic pollutants, remediation methods, and acid mine drainage. Also included in the PDF chapters are informative diagrams, problem sets and solutions

Sherman, David M.; Bristol, University O.

168

Refinement of Near Earth Asteroids' orbital elements via simultaneous measurements by two observers  

NASA Astrophysics Data System (ADS)

The aspects of triangulation of Near Earth Asteroids by two arbitrarily positioned observers (one spaceborne and the other Earth-bound, as well as both spaceborne) are being investigated, and the resulting orbital elements are compared to those gained through common orbital determination and refinement techniques. The main advantages of the method proposed in this work are, that given the approximate position of an asteroid, high quality orbital elements can be acquired very rapidly using two observations only.

Eggl, Siegfried

2011-03-01

169

Investigation of Chemical and Physical Changes to Bioapatite During Fossilization Using Trace Element Geochemistry, Infrared Spectroscopy and Stable Isotopes  

NASA Astrophysics Data System (ADS)

Bioapatite in the form of vertebrate bone can be used for a wide variety of paleo-proxies, from determination of ancient diet to the isotopic composition of meteoric water. Bioapatite alteration during diagenesis is a constant barrier to the use of fossil bone as a paleo-proxy. To elucidate the physical and chemical alteration of bone apatite during fossilization, we analyzed an assortment of fossil bones of different ages for trace elements, using LA-ICP-MS, stable isotopes, and reflected IR spectroscopy. One set of fossil bones from the Pleistocene of Idaho show a diffusion recrystallization profile, however, rare earth element (REE) profiles indicate diffusion adsorption. This suggests that REE diffusion is controlled by changing (namely decreasing) boundary conditions (i.e. decreasing concentration of REE in surrounding pore fluids). Reflected IR analysis along this concentration profile reveal that areas high in U have lost type A carbonate from the crystal structure in addition to water and organics. Stable isotopic analysis of carbon and oxygen will determine what, if any, change in the isotopic composition of the carbonate component of apatite has occurred do to the diffusion and recrystallization process. Analysis of much older bone from the Cretaceous of China reveal shallow REE and U concentration profiles and very uniform reflected IR spectra with a significant loss of type A carbonate throughout the entire bone cortex. Analysis of stable isotopes through the bone cortex will be compared to the stable isotopes collected from the Pleistocene of Idaho.

Suarez, C. A.; Kohn, M. J.

2013-12-01

170

Core-Mantle Partitioning of Volatile Elements and the Origin of Volatile Elements in Earth and Moon  

NASA Technical Reports Server (NTRS)

Depletions of volatile siderophile elements (VSE; Ga, Ge, In, As, Sb, Sn, Bi, Zn, Cu, Cd) in mantles of Earth and Moon, constrain the origin of volatile elements in these bodies, and the overall depletion of volatile elements in Moon relative to Earth. A satisfactory explanation has remained elusive [1,2]. We examine the depletions of VSE in Earth and Moon and quantify the amount of depletion due to core formation and volatility of potential building blocks. We calculate the composition of the Earth's PUM during continuous accretion scenarios with constant and variable fO2. Results suggest that the VSE can be explained by a rather simple scenario of continuous accretion leading to a high PT metal-silicate equilibrium scenario that establishes the siderophile element content of Earth's PUM near the end of accretion [3]. Core formation models for the Moon explain most VSE, but calculated contents of In, Sn, and Zn (all with Tc < 750 K) are all still too high after core formation, and must therefore require an additional process to explain the depletions in the lunar mantle. We discuss possible processes including magmatic degassing, evaporation, condensation, and vapor-liquid fractionation in the lunar disk.

Righter, Kevin; Pando, K.; Danielson, L.; Nickodem, K.

2014-01-01

171

Rare earth element complexation by carbonate and oxalate ions  

NASA Astrophysics Data System (ADS)

Rare earth carbonate and oxalate complexation constants have been determined through ex-amination of distribution equilibria between tributyl phosphate and an aqueous perchlorate phase. Carbonate complexation constants appropriate to the REE in seawater (25°C, 35%., 1 atm) can be described in terms of atomic number, Z. nlog sw?1 = 4.853 + 0.1135( Z - 57) - 0.003643( Z - 57) 2log sw?2 = 80.197 + 0.1730( Z - 57) - 0.002714( Z -57) 2 where sw? 1 = [MCO +3] /[M 3+][CO 2-3] T, sw? 2 = [M(CO 3) -3] /[M 3+][CO 2-3] 2' T [ M3+] is an uncomplexed rare earth concentration in seawater, [ MCO+3] and [ M( CO-3) 2] are carbonate complex concentrations, and [CO 2-3] T is the total (free plus ion paired) carbonate ion concentration in seawater (molal scale). Our analyses indicate that in seawater with a total carbonate ion concentration of 1.39 × 10 -4 moles/Kg H 2O, carbonate complexes for the lightest rare earth, La, constitute 86% of the total metal, 7% is free La 3+ and the remaining 7% exists as hydroxide, sulfate, chloride and fluoride complexes. For Lu, the heaviest rare earth, carbonate complexes are 98% of the total metal, 0.3% is uncomplexed and 1.5% is complexed with hydroxide, sulfate, chloride and fluoride. Oxalate and carbonate constants are linearly correlated. This correlation appears to be quite useful for estimating trivalent metal-arbonate stability constants from their respective oxalate stability constants.

Cantrell, Kirk J.; Byrne, Robert H.

1987-03-01

172

Volatile element abundance patterns and an early liquid water ocean on Earth  

Microsoft Academic Search

The abundances of the elements H, C, N, Ne, primordial Ar, Cl, Br, Kr, I and Xe, in the atmo-hydrosphere, continental crust and MORB-source mantle (termed the outer Earth reservoirs (OER)) are examined and compared with solar matter and an average of carbonaceous chondrites (CC). The aim is to assess the likelihood of various possible sources for these volatile elements

Jan D Kramers

2003-01-01

173

Separation method and yields of small quantities of rare earth elements  

Microsoft Academic Search

The EMIS PARSIFAL was designed to purify very small quantities of radioactive isotopes. Yields are therefore an important component of the separations. The ionization is done in a thermoionization source or a plasma source, according to the physical properties of the concerned elements. For rare earth elements (REE), hydroxides are electrodeposited on a tantalum wire; for thermoionization, the wire is

Y. Boulin; A. Juery

1992-01-01

174

Allanite: thorium and light rare earth element carrier in subducted crust  

Microsoft Academic Search

The investigation of deeply subducted eclogites from the Dora-Maira massif, Western Alps reveals that accessory minerals are important hosts for trace elements. Rutile contains most of the bulk rock Ti, Nb and Ta while zircon hosts nearly all Zr and Hf. More than 90% of the bulk rock light rare earth elements (LREE) and Th and about 75% of U

Jörg Hermann

2002-01-01

175

Experimental productivity rate optimization of rare earth element separation through preparative solid phase extraction chromatography.  

PubMed

Separating individual rare earth elements from a complex mixture with several elements is difficult and this is emphasized for the middle elements: Samarium, Europium and Gadolinium. In this study we have accomplished an overloaded one-step separation of these rare earth elements through preparative ion-exchange high-performance liquid chromatography with an bis (2-ethylhexyl) phosphoric acid impregnated column and nitric acid as eluent. An inductively coupled plasma mass spectrometry unit was used for post column element detection. The main focus was to optimize the productivity rate, subject to a yield requirement of 80% and a purity requirement of 99% for each element, by varying the flow rate and batch load size. The optimal productivity rate in this study was 1.32kgSamarium/(hmcolumn(3)), 0.38kgEuropium/(hmcolumn(3)) and 0.81kgGadolinium/(hmcolumn(3)). PMID:24835593

Knutson, Hans-Kristian; Max-Hansen, Mark; Jönsson, Christian; Borg, Niklas; Nilsson, Bernt

2014-06-27

176

The Toxicological Geochemistry of Dusts, Soils, and Other Earth Materials: Insights From In Vitro Physiologically-based Geochemical Leach Tests  

NASA Astrophysics Data System (ADS)

Exposure to mineral dusts, soils, and other earth materials results in chemical reactions between the materials and different body fluids that include, depending upon the exposure route, lung fluids, gastrointestinal fluids, and perspiration. In vitro physiologically-based geochemical leach tests provide useful insights into these chemical reactions and their potential toxicological implications. We have conducted such leach tests on a variety of earth materials, including asbestos, volcanic ash, dusts from dry lake beds, mine wastes, wastes left from the roasting of mercury ores, mineral processing wastes, coal dusts and coal fly ash, various soils, and complex dusts generated by the World Trade Center collapse. Size-fractionated samples of earth materials that have been well-characterized mineralogically and chemically are reacted at body temperature (37 C) for periods from 2 hours up to multiple days with various proportions of simulated lung, gastric, intestinal, and/or plasma-based fluids. Results indicate that different earth materials may have quite different solubility and dissolution behavior in vivo, depending upon a) the mineralogic makeup of the material, and b) the exposure route. For example, biodurable minerals such as asbestos and volcanic ash particles, whose health effects result because they dissolve very slowly in vivo, bleed off low levels of trace metals into the simulated lung fluids; these include metals such as Fe and Cr that are suspected by health scientists of contributing to the generation of reactive oxygen species and resulting DNA damage in vivo. In contrast, dry lake bed dusts and concrete-rich dusts are highly alkaline and bioreactive, and cause substantial pH increases and other chemical changes in the simulated body fluids. Many of the earth materials tested contain a variety of metals that can be quite soluble (bioaccessible), depending upon the material and the simulated body fluid composition. For example, due to their acidic pH and high chloride concentrations, simulated gastric fluids are most efficient at solubilizing metals such as Hg, Pb, Zn, and others that form strong chloride complexes; although these metals tend to partially reprecipitate in the near-neutral simulated intestinal fluids, complexes with organic ligands (i.e., amino and carboxylic acids) enhance their solubility. These metals are also quite soluble in near-neutral, protein-rich plasma-based fluids because they form strong complexes with the proteins. In contrast, metalloids that form oxyanion species (such as As, Cr, Mo, W) are commonly more soluble in near-neutral pH simulated lung fluids than in simulated gastric fluids.

Plumlee, G. S.; Ziegler, T. L.; Lamothe, P.; Meeker, G. P.; Sutley, S.

2003-12-01

177

U-Pb SHRIMP geochronology and trace-element geochemistry of coesite-bearing zircons, North-East Greenland Caledonides  

USGS Publications Warehouse

Obtaining reliable estimates for the timing of eclogite-facies metamorphism is critical to establishing models for the formation and exhumation of high-pressure and ultrahigh-pressure (UHP) metamorphic terranes in collisional orogens. The presence of pressure-dependent phases, such as coesite, included in metamorphic zircon is generally regarded as evidence that zircon growth occurred at UHP conditions and, ifdated, should provide the necessary timing information. We report U-Pb sensitive high-resolution ion microprobe (SHRIMP) ages and trace-element SHRIMP data from coesite-bearing zircon suites formed during UHP metamorphism in the North- East Greenland Caledonides. Kyanite eclogite and quartzofeldspathic host gneiss samples from an island in J??kelbugt (78??00'N, 18??04'W) contained subspherical zircons with well-defined domains in cathodoluminescence (CL) images. The presence of coesite is confirmed by Raman spectroscopy in six zircons from four samples. Additional components of the eclogite-facies inclusion suite include kyanite, omphacite, garnet, and rutile. The trace-element signatures in core domains reflect modification of igneous protolith zircon. Rim signatures show flat heavy rare earth element (HREE) patterns that are characteristic of eclogite-facies zircon. The kyanite eclogites generally lack a Eu anomaly, whereas a negative Eu anomaly persists in all domains of the host gneiss. The 207Pb- corrected 206Pb/238U ages range from 330 to 390 Ma for the host gneiss and 330-370 Ma for the kyanite eclogite. Weighted mean 206Pb/238U ages for coesite-bearing domains vary from 364 ?? 8 Ma for the host gneiss to 350 ?? 4 Ma for kyanite eclogite. The combined U-Pb and REE data interpreted in conjunction with observed CL domains and inclusion suites suggest that (1) Caledonian metamorphic zircon formed by both new zircon growth and recrystallization, (2) UHP metamorphism occurred near the end of the Caledonian collision, and (3) the 30-50m.y. span of ages records long residence times at eclogite-facies conditions for the UHProcks of North-East Greenland. This spread in observed ages is interpreted to be characteristic of metamorphic rocks that have experienced relatively long (longer than 10 m.y.) residence times at UHP conditions. ?? 2006 Geological Society of America.

McClelland, W. C.; Power, S. E.; Gilotti, J. A.; Mazdab, F. K.; Wopenka, B.

2006-01-01

178

A predictive model for rare earth element partitioning between clinopyroxene and anhydrous silicate melt  

Microsoft Academic Search

We present a quantitative model to describe the partitioning of rare earth elements (REE) and Y between clinopyroxene and\\u000a anhydrous silicate melt as a function of pressure (P), temperature (T) and bulk composition (X). The model is based on the Brice (1975) equation, which relates the partition coefficient of element i (D\\u000a \\u000a i\\u000a ) to that of element o (D

Bernard J. Wood; Jonathan D. Blundy

1997-01-01

179

Neutron Induced Radioactivity in Certain Rare-Earth Elements  

Microsoft Academic Search

By activating specimens of lanthanum, neodymium, samarium, europium, gadolinium, and terbium in the Oak Ridge pile for a particularly long exposure, several hitherto unobserved radioactivities are found. Determinations are made of the half-lives and of the beta- and gamma-energies by absorption and spectrometric methods. Lanthanum and neodymium were the only elements showing no internal conversion lines. Terbium appears as a

J. M. Cork; R. G. Shreffler; C. M. Fowler

1948-01-01

180

Rare Earth Elemental Signatures in Fungal Fruiting Bodies as Probes into Mineral Breakdown Reactions in Post-glacial Landscapes  

NASA Astrophysics Data System (ADS)

The application of rare earth element (REE) abundances in low temperature geochemistry and biogeochemistry has improved our understanding of the cycling of various micro- and macronutrients from the bedrock into terrestrial ecosystems. In many continental rocks, REEs are concentrated in accessory phases such as apatite and monazite. These phosphate mineral phases break down readily and may be especially important nutrient sources, particularly for P and Ca, in recently glaciated terrains. Several studies (e.g., 1-3) have suggested that the presence of ectomycorrhizal (ECM) fungi, due to the organic acids they secrete, may play an especially important role in this weathering process. A field-based experiment implementing mesh bags doped with specific mineral compositions confirmed that ECM fungal tissues do record the REE signatures of the minerals they break down (4). In an effort to understand the relative role different ECM fungi may play in mineral breakdown reactions, we have measured REE abundances in tissues of several ECM fruiting bodies. Our preliminary data include Russula, Suillus Americana, Leccinum and Lactarius ECM fungi from three postglacial landscapes. At a given site, the relative abundance of REEs varies between the different ECM fungi. Interestingly, we found distinctions in tissue La/Ce values at two of the sites. Leccinum, a deep rooter, shows much lower La/Ce than the companion Russula and Lactarius samples from the same site. Similarly Suillus tissues demonstrated lower La/Ce when compared to Russula growing nearby. Lower La/Ce is consistent with enhanced dissolution of the mineral apatite, a common accessory phase. While the influence of symbiotic host (beech vs. oak vs. pine) may play some role in the distinctive REE signatures recorded by the fruiting bodies, we attribute the observed differences to organic acid production and tendency to colonize in different horizons of the soil profile. (1) Wallander, Plant and Soil, 2000; (2) Blum et al., Nature, 2002; (3) Hoffland et al., Front Ecol Environ., 2003; (4) Hagerburg et al., Plant and Soil, 2003.

Bryce, J. G.; Hobbie, E. A.

2008-12-01

181

Rare earth element zonation in Pacific ferromanganese nodules  

NASA Astrophysics Data System (ADS)

The lower surfaces of ferromanganese nodules from the north equatorial Pacific Ocean, which are enriched in Mn, Cu and Ni, and the upper surfaces, which are enriched in Fe, P and Co, have been analyzed for La, Ce, Nd, Sm, Eu, Gd, Dy, Er and Yb. The REE contents are lower and the Ce anomaly is smaller in the lower surfaces than in the upper surfaces. The magnitude of the Ce anomaly increases with decreasing Mn/Fe ratio, indicative of a seawater origin. The zonal distribution of the other REE supports the conclusion derived previously from inter-nodule and nodule/sediment relationships that diagenetic fixation of rare earths in sediments affects their enrichment by nodular iron oxyhydroxides.

Elderfield, H.; Hawkesworth, C. J.; Greaves, M. J.; Calvert, S. E.

1981-07-01

182

Microprobe analyses of rare earth element fractionation in meteoritic minerals  

Microsoft Academic Search

Two meteorites were analyzed by PIXE with the Los Alamos nuclear microprobe. The enstatite achondrite Pen~a Blanca Spring and the ordinary chondrite St Severin were chosen as likely candidates for use in 244Pu (t1\\/2 = 82 my) cosmochronology and geochronology. These applications require the meteoritic minerals to have unfractionated actinides and lanthanides relative to ``cosmic'' elemental abundance ratios. The PIXE

T. M. Benjamin; C. J. Duffy; C. J. Maggiore; P. S. Z. Rogers; D. S. Woolum; D. S. Burnett; M. T. Murrell

1984-01-01

183

Effect of rare earth elements on the microstructure of Mg-Al alloys  

Microsoft Academic Search

Purpose: The automotive use of magnesium is currently restricted to low-temperature structural components. Rare earth additions such as Ce, Nd, La and Pr are known to improve the creep performance. The aim of the research was to determine the effect of rare earths elements on the as-cast microstructure of magnesium alloys containing 4 wt% aluminum. Design\\/methodology\\/approach: The study was conducted

T. Rzycho?; A. Kie?bus

184

U.S. trade dispute with China over rare earth elements  

NASA Astrophysics Data System (ADS)

The U.S. government has brought a new trade case against China over rare earth elements (REE) as well as tungsten and molybdenum, President Barack Obama announced on 13 March. Japan and the European Union also have taken similar actions against China about REEs, which are a group of 17 chemically similar metallic elements that are used in a variety of electronic, optical, magnetic, and catalytic applications. REEs are plentiful in the Earth's crust, although China currently has about 37% of the world's reserves and accounts for more than 95% of the world's production of the elements, according to the British Geological Survey. The United States has requested consultations with China at the World Trade Organization (WTO) concerning “China's unfair export restraints on rare earths, as well as tungsten and molybdenum,” the Office of the United States Trade Representative announced in a 13 March statement.

Showstack, Randy

2012-03-01

185

Geochemistry Index  

NSDL National Science Digital Library

This site is the index of a book used in a geochemistry course taught by W. M. White at Cornell University. There are 15 chapters and a table of contents available. All of the chapters are large PDF files and take some time to download. Figures and exercises accompany the text.

White, William M.; Department Of Earth And Atmospheric Sciences, Cornell U.

186

Platinum-group element geochemistry of the Zhuqing Fe-Ti-V oxide ore-bearing mafic intrusions in western Yangtze Block, SW China: control of platinum-group elements by magnetite  

NASA Astrophysics Data System (ADS)

Platinum-group element (PGE) geochemistry combined with elemental geochemistry and magnetite compositions are reported for the Mesoproterozoic Zhuqing Fe-Ti-V oxide ore-bearing mafic intrusions in the western Yangtze Block, SW China. All the Zhuqing gabbros display extremely low concentrations of chalcophile elements and PGEs. The oxide-rich gabbros contain relatively higher contents of Cr, Ni, Ir, Ru, Rh, and lower contents of Pt and Pd than the oxide-poor gabbros. The abundances of whole-rock concentrations of Ni, Ir, Ru, and Rh correlate well with V contents in the Zhuqing gabbros, implying that the distributions of these elements are controlled by magnetite. The fractionation between Ir-Ru-Rh and Pt-Pd in the Zhuqing gabbros is mainly attributed to fractional crystallization of chromite and magnetite, whereas Ru anomalies are mainly due to variable degrees of compatibility of PGE in magnetite. The order of relative incompatibility of PGEs is calculated to be Pd < Pt < Rh < Ir < Ru. The very low PGE contents and Cu/Zr ratios and high Cu/Pd ratios suggest initially S-saturated magma parents that were highly depleted in PGE, which mainly formed due to low degrees of partial melting leaving sulfides concentrating PGEs behind in the mantle. Moreover, the low MgO, Ni, Ir and Ru contents and high Cu/Ni and Pd/Ir ratios for the gabbros suggest a highly evolved parental magma. Fe-Ti oxides fractionally crystallized from the highly evolved magma and subsequently settled in the lower sections of the magma chamber, where they concentrated and formed Fe-Ti-V oxide ore layers at the base of the lower and upper cycles. Multiple episodes of magma replenishment in the magma chamber may have been involved in the formation of the Zhuqing intrusions.

Fan, Hong-Peng; Zhu, Wei-Guang; Zhong, Hong; Bai, Zhong-Jie; He, De-Feng; Ye, Xian-Tao; Chen, Cai-Jie; Cao, Chong-Yong

2014-06-01

187

Rare earths and other trace elements in Apollo 14 samples.  

NASA Technical Reports Server (NTRS)

REE and other trace elements have been determined in igneous rocks 14053, 14072, and 14310, in breccias 14063 and 14313, and in fines 14163. All materials analyzed have typical depletions of Eu except for feldspar fragments from the breccias and igneous fragments from 14063. Igneous rocks 14072 and 14053 have REE concentrations very similar to Apollo 12 basalts; 14310 has the highest REE concentrations yet observed for a large fragment of lunar basalt. The effects of crystallization of a basaltic liquid as a closed system on the concentrations of Sm and Eu in feldspar are considered. Small anorthositic fragments may have originated by simple crystallization from very highly differentiated basalt (KREEP) or by closed-system crystallization in a less differentiated starting material. Application of independent models of igneous differentiation to Sm and Eu in massive anorthosite 15415 and to Sm and Eu in lunar basalts suggests a common starting material with a ratio of concentrations of Sm and Eu about the same as that in chondrites and with concentrations of those elements about 15 times enriched over chondrites.

Helmke, P. A.; Haskin, L. A.; Korotev, R. L.; Ziege, K. E.

1972-01-01

188

Alkaline-earth metal and rare-earth element incorporation control by ionic radius and growth rate on a stalagmite from the Chauvet Cave, Southeastern France  

Microsoft Academic Search

A multi-element study involving major alkaline-earth cations (Mg, Ca, Sr, Ba) and trace elements like Na, U, Mn, Y and Rare Earth Elements (REE) in calcite of a stalagmite from the Chauvet Cave (SE of France) was carried out using ICP-QMS analysis. This study focused on the Chau-stm6 stalagmite which displays a record of the Last Deglaciation until the end

Clément Bourdin; Eric Douville; Dominique Genty

2011-01-01

189

Determination of rare-earth elements in Luna 16 regolith sample by chemical spectral method  

NASA Technical Reports Server (NTRS)

An analysis was made of regolith from layer A of the Luna 16 sample for rare earth elements, by a chemical spectral method. Chemical and ion exchange concentrations were used to determine the content of 12 elements and Y at the level 0.001 to 0.0001 percent with 10 to 15 percent reproducibility of the emission determination. Results within the limits of reproducibility agree with data obtained by mass spectra, activation, and X-ray fluorescent methods.

Stroganova, N. S.; Ryabukhin, V. A.; Laktinova, N. V.; Ageyeva, L. V.; Galkina, I. P.; Gatinskaya, N. G.; Yermakov, A. N.; Karyakin, A. V.

1974-01-01

190

Partitioning of rare earth elements between clinopyroxene and silicate melt Crystal-chemical controls  

Microsoft Academic Search

This study explores some of the effects of major element compositional variations on the partitioning of trivalent rare earth elements between high-Ca clinopyroxene and silicate melt. Experiments performed in the system CaO?MgO?A12O3?SiO2 at 1 atm pressure, over a small temperature range, differentiate crystal-chemical controls on mineral\\/melt partitioning from the effects of pressure and temperature. The experimental results demonstrate that the

Glenn A. Gaetani; Timothy L. Grove

1995-01-01

191

Partitioning of rare earth elements between clinopyroxene and silicate melt Crystal-chemical controls  

Microsoft Academic Search

This study explores some of the effects of major element compositional variations on the partitioning of trivalent rare earth elements between high-Ca clinopyroxene and silicate melt. Experiments performed in the system CaO---MgO---A1 2 O 3 ---SiO 2 at 1 atm pressure, over a small temperature range, differentiate crystal-chemical controls on mineral\\/melt partitioning from the effects of pressure and temperature. The

Glenn A. Gaetani; Timothy L. Grove

1995-01-01

192

Preservation of NOM-metal complexes in a modern hyperalkaline stalagmite: Implications for speleothem trace element geochemistry  

NASA Astrophysics Data System (ADS)

We report the first quantitative study of the capture of colloidal natural organic matter (NOM) and NOM-complexed trace metals (V, Co, Cu, Ni) in speleothems. This study combines published NOM-metal dripwater speciation measurements with high-resolution laser ablation ICPMS (LA-ICPMS) and sub-annual stable isotope ratio (?18O and ?13C), fluorescence and total organic carbon (TOC) analyses of a fast-growing hyperalkaline stalagmite (pH ˜11) from Poole’s Cavern, Derbyshire UK, which formed between 1997 and 2008 AD. We suggest that the findings reported here elucidate trace element variations arising from colloidal transport and calcite precipitation rate changes observed in multiple, natural speleothems deposited at ca. pH 7-8. We find that NOM-metal(aq) complexes on the boundary between colloidal and dissolved (˜1 nm diameter) show an annual cyclicity which is inversely correlated with the alkaline earth metals and is explained by calcite precipitation rate changes (as recorded by kinetically-fractionated stable isotopes). This relates to the strength of the NOM-metal complexation reaction, resulting in very strongly bound metals (Co in this system) essentially recording NOM co-precipitation (ternary complexation). More specifically, empirical partition coefficient (Kd) values between surface-reactive metals (V, Co, Cu, Ni) [expressed as ratio of trace element to Ca ratios in calcite and in solution] arise from variations in the ‘free’ fraction of total metal in aqueous solution (fm). Hence, differences in the preservation of each metal in calcite can be explained quantitatively by their complexation behaviour with aqueous NOM. Differences between inorganic Kd values and field measurements for metal partitioning into calcite occur where [free metal] ? [total metal] due to complexation reactions between metals and organic ligands (and potentially inorganic colloids). It follows that where fm ? 0, apparent inorganic Kd app values are also ?0, but the true partition coefficient (Kd actual) is significantly higher. Importantly, the Kd of NOM-metal complexes [organic carbon-metal ratio) approaches 1 for the most stable aqueous complexes, as is shown here for Co, but has values of 24-150 for V, Ni and Cu. This implies that ternary surface complexation (metal-ligand co-adsorption) can occur (as for NOM-Co), but is the exception rather than the rule. We also demonstrate the potential for trace metals to record information on NOM composition as expressed through changing NOM-metal complexation patterns in dripwaters. Therefore, a suite of trace metals in stalagmites show variations clearly attributable to changes in organic ligand concentration and composition, and which potentially reflect the state of overlying surface ecosystems. The heterogeneous speciation and size distribution of aqueous NOM and metals (Lead and Wilkinson, 2006; Aiken et al., 2011). The variability in NOM-metal transport in caves that arises from the interaction between infiltration, flow routing, and the hydrodynamic properties of the fine colloids and particulates (Hartland et al., 2012). Variable dissociation kinetics through time as a function of (a) (Hartland et al., 2011). The surface charge of calcite and the availability of CaCO3 lattice sites as well as increased incidence of crystallographic defects with implications for incorporation of a range of trace species (Fairchild and Treble, 2009; Fairchild and Hartland, 2010). Thus, incorporation in speleothem calcite with consistent surface site properties will be determined by: The size and composition (i.e. hydrophilicity/hydrophobicity) of the NOM ligand, affecting adsorption and stability at the calcite surface. The lability (i.e. exchangeability) of the complexed metal and its binding affinity for the calcite surface. The concentration of aqueous complexes. Given the complexities, a partitioning approach to the problem is appropriate as a first approximation rather than a precise description. This study seeks to make the first quantitative connection between the organic and inorgani

Hartland, Adam; Fairchild, Ian J.; Müller, Wolfgang; Dominguez-Villar, David

2014-03-01

193

Mutual influence of elements during coprecipitation. Cocrystallization of rare-earth elements under conditions for the formation of double sulfates of alkali and alkaline-earth metals  

SciTech Connect

This paper studies the coprecipitation of rare-earth metals under conditions for the crystallization of double salts in other sulfate systems, as well as the possibility of the employment of these double salts for the selective preconcentration of rare-earth metals from solutions of complex composition. The influence of electrolytes containing and not containing an element which may act as a charge compensator during isomorphous substitution was studied. Data are presented on the coprecipitation of cerium (III) and lutetium under the conditions for the crystallization of the double salt K/sub 2/SR(SO/sub 4/)/sub 2/ in the presence of LiC1 and LiNO/sub 3/, as well as HC1 and HNO/sub 3/.

Tsizin, G.I.; Kalinchenko, N.B.; Malofeeva, G.I.; Marov, I.N.; Tobelko, K.I.; Urusov, V.S.

1985-04-20

194

Effect of rare earth elements on growth and antioxidant metabo- lism in Lemna minor L  

Microsoft Academic Search

Lemna minor is frequently used in bioremediation processes to remove nutrients and contaminants from waste water. In this work the response of L. minor to treatments with lanthanum nitrate and with a mix of several light rare earth elements (REE) nitrates was investigated. Preliminary results indicate that L. minor shows an overall good tolerance to the presence of REE in

Maria Paola; Costantino Paciolla; Luigi d'Aquino; Massimo Morgan; Franca Tommasi

195

SEDIMENT REWORKING AND TRANSPORT IN EASTERN LAKE SUPERIOR: IN SITU RARE EARTH ELEMENT TRACER STUDIES  

EPA Science Inventory

A rare earth element (REE) tracer pellet was deployed at the floor of the Ile Parisienne basin of eastern Lake Superior to measure representative sediment reworking and transport processes in the benthic boundary layer of the prnfundal Great Lakes. Samarium oxide, a high neutron-...

196

Behavior of Rare Earth Elements in Geothermal Systems: A New Exploration/Exploitation Tool.  

National Technical Information Service (NTIS)

The goal of this four-year project was to provide a database by which to judge the utility of the rare earth elements (REE) in the exploration for and exploitation of geothermal fields in the United States. Geothermal fluids from hot springs and wells hav...

S. A. Wood

2001-01-01

197

Investigating source areas of eroded sediments transported in concentrated overland flow using rare earth element tracers  

Microsoft Academic Search

Rare earth element oxides (REOs) have excellent potential for use as tracers in erosion studies. Using laboratory and field experiments we aimed to develop and test a simple application method for spreading REOs and to use REOs to determine the source of sediment to concentrated overland flow paths. Tracks left by farm machinery (tramlines) in fields act as concentrated flow

C. J. Stevens; J. N. Quinton

198

Paleoredox variations in ancient oceans recorded by rare earth elements in fossil apatite  

Microsoft Academic Search

Rare earth element concentrations in biogenic apatite of conodonts, fish debris and inarticulate brachiopods were determined in over 200 samples from Cambrian to modern sediments. Tests for experimental bias caused by the chemicals used to separate fossils from the rock matrix and for interlaboratory, interexperiment or interspecies related variations clearly show that no resolvable fractionation of REE occurs. Incorporation of

Judith Wright; Hans Schrader; William T. Holser

1987-01-01

199

Rare earth element distributions in anoxic waters of the Cariaco Trench  

Microsoft Academic Search

The concentrations of dissolved and suspended particulate rare earth elements in the Cariaco Trench are reported. In solution all REE, notably Ce, show a sharp increase just at or below the oxic \\/ anoxic interface at 300 meters depth. Particulate concentrations show a complementary decrease at the same depth. The overlying oxic waters exhibit a negative Ce anomaly; the anoxic

Hein J. W. de Baar; Christopher R. German; Henry Elderfield; Pauline van Gaans

1988-01-01

200

Method for the Analysis of Rare Earth Elements in Natural Waters by Isotope Dilution Mass Spectrometry.  

National Technical Information Service (NTIS)

A method is described to measure rare-earth elements (REE) in natural water samples. An iron hydroxide precipitation followed by ion exchange chromatography is used to concentrate and separate the REE from other matrix components. Additionally, the rare-e...

D. L. Schneider J. M. Palmieri

1994-01-01

201

Behavior of Rare Earth Element In Geothermal Systems; A New Exploration\\/Exploitation Tool  

Microsoft Academic Search

The goal of this four-year project was to provide a database by which to judge the utility of the rare earth elements (REE) in the exploration for and exploitation of geothermal fields in the United States. Geothermal fluids from hot springs and wells have been sampled from a number of locations, including: (1) the North Island of New Zealand (1

Scott A. Wood

2002-01-01

202

Rare Earth Element Fluxes in Diverse Soils and Their Absorption by Coconut Palm  

Microsoft Academic Search

The pattern of uptake of six rare earth elements (REEs) [lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), and gadolinium (Gd)] by coconut palm (Cocos nucifera L.) from three types of soils varying widely in their chemical characteristics and monazite content were studied through soil and plant tissue analysis employing ICP?MS method. Absorption of the REEs by the

P. A. Wahid; N. V. Kamalam; R. Krishna Prabhu; J. K. Sekhar; S. Vijayalakshmi; T. R. Mahalingam; C. E. Ajith Kumar

2003-01-01

203

Undecaprenyl Pyrophosphate Involvement in Susceptibility of Bacillus subtilis to Rare Earth Elements  

PubMed Central

The rare earth element scandium has weak antibacterial potency. We identified a mutation responsible for a scandium-resistant phenotype in Bacillus subtilis. This mutation was found within the uppS gene, which encodes undecaprenyl pyrophosphate synthase, and designated uppS86 (for the Thr-to-Ile amino acid substitution at residue 86 of undecaprenyl pyrophosphate synthase). The uppS86 mutation also gave rise to increased resistance to bacitracin, which prevents cell wall synthesis by inhibiting the dephosphorylation of undecaprenyl pyrophosphate, in addition to enhanced amylase production. Conversely, overexpression of the wild-type uppS gene resulted in increased susceptibilities to both scandium and bacitracin. Moreover, the mutant lacking undecaprenyl pyrophosphate phosphatase (BcrC) showed increased susceptibility to all rare earth elements tested. These results suggest that the accumulation of undecaprenyl pyrophosphate renders cells more susceptible to rare earth elements. The availability of undecaprenyl pyrophosphate may be an important determinant for susceptibility to rare earth elements, such as scandium.

Ochi, Kozo

2012-01-01

204

Fractionation in the solar nebula - Condensation of yttrium and the rare earth elements  

Microsoft Academic Search

The condensation of Y and the rare earth elements (REE) from the solar nebula may be controlled by thermodynamic equilibrium between gas and condensed solids. Highly fractionated REE patterns may result if condensates are removed from the gas before condensation is complete. It is found that the fractionation is not a smooth function of REE ionic radius but varies in

W. V. Boynton

1975-01-01

205

Composition of the earth's upper mantle. I - Siderophile trace elements in ultramafic nodules  

NASA Technical Reports Server (NTRS)

The considered investigation is concerned with a reexamination of the question of the distribution of siderophile elements in the earth's upper mantle, taking into account a more unified data base which is now available. A comprehensive suite of ultramafic inclusions was collected as part of the Basaltic Volcanism Study Project and has been analyzed by instrument neutron activation analysis for major, minor, and some lithophile trace elements. In addition, 18 of these rocks and the important sheared garnet lherzolite PHN 1611 have been analyzed by means of radiochemical neutron activation analysis for 7 siderophile elements (Au, Ge, Ir, Ni, Os, Pd, and Re) and 9 volatile elements (Ag, Bi, Cd, In, Sb, Se, Te, Tl, and Zn). The siderophile element data reveal interesting inter-element correlations, which were not apparent from the compiled abundance tables of Ringwood and Kesson (1976) and Chou (1978).

Morgan, J. W.; Wandless, G. A.; Petrie, R. K.; Irving, A. J.

1981-01-01

206

Geochemistry Home  

NSDL National Science Digital Library

This project provides resources for teaching geochemistry. It includes an on-line tutorial of the analytical techniques commonly used to characterize geological materials, the goal of which is to help novices (such as students or scientists working out of their field) to gain an understanding of mineralogical, petrological and geochemical analytical techniques. There is also a collection of teaching activities and a geochemical instrument registry available on this site.

207

Uranium and rare earth elements in CO 2-rich waters from Vals-les-Bains (France)  

NASA Astrophysics Data System (ADS)

Waters from springs at Vals-les-Bains result from the mixing of a CO 2-rich, highly mineralized water with dilute, shallow subsurface water. Total content of dissolved species vary from 5 mmol/1 to 100 mmol/1. For many elements, mixing of these waters is non-linear (non-conservative) and further water-rock reactions take place. The pH is controlled by CO 2 outgassing, redox conditions are controlled by both the iron hydroxide-siderite buffer and the introduction of oxygen with shallow subsurface waters. Among the major elements, concentrations of Ca, Mg, Mn, Fe, are related to mixing, CO 2 outgassing and carbonate precipitation. Uranium shows a complex behaviour controlled by carbonate complexing, redox conditions, mixing of waters and leaching from the rocks. The 234U /238U activity ratio is near secular equilibrium. In the more dilute waters, dissolved rare earth element (REE) patterns are almost flat with a slight negative Eu anomaly. In the concentrated waters, heavy rare earth elements (Gd-Yb, HREE) are strongly enriched relative to light rare earth elements (Ce-Eu, LREE). We relate the enrichment in HREE to water chemistry and to complexing with carbonate species.

Michard, Annie; Beaucaire, Catherine; Michard, Gil

1987-04-01

208

Introduction to exploration geochemistry. [Textbook  

Microsoft Academic Search

Exploration geochemistry is the practical application of theoretical geochemical principles to mineral and hydrocarbon exploration. Its specific aim is to find new deposits of metals and nonmetals, or accumulations of crude oil and natural gas, and to locate extensions of existing deposits by employing chemical methods. The objective is to find some dispersion of elements or compounds sufficiently above normal

1974-01-01

209

[Determination of ten trace rare earth elements in the sample by atomic emission spectrometry].  

PubMed

This paper describes the determination of trace La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Yb and Lu in the sample, using carbon powder, potassium sulfate, barium sulfate, strontium sulfate, and scandium chloride as buffer, by atomic emission spectrometry (AES). Scandium was selected as internal standard line. Sample separation and chemical treatment were not required. The sample was directly loaded into ordinary electrode. The method is simple, rapid and accurate. The determination requirement and influence factors were studied. A new method was developed for the determination of ten rare earth elements, for which the detection limit is smaller than 0.030%, and the range of the recovery is 94%-105%. The results of these elements in standard sample are in agreement with certified values, and the RSD is smaller than 5% (n = 9). The method has been applied to the determination of ten rare earth elements with satisfactory results. PMID:16379301

Li, Hui-zhi; Zhai, Dian-tang; Zhang, Jin; Pei, Mei-shan

2005-09-01

210

?-decay of neutron-rich Zâ¼60 nuclei and the origin of rare earth elements  

NASA Astrophysics Data System (ADS)

A large fraction of the rare-earth elements observed in the solar system is produced in the astrophysical rapid neutron capture process (r-process). However, current stellar models cannot completely explain the relative abundance of these elements partially because of nuclear physics uncertainties. To address this problem, a ?-decay spectroscopy experiment was performed at RI Beam Factory (RIBF) at RIKEN, aimed at studying a wide range of very neutron-rich nuclei with Z˜60 that are progenitors of the rare-earth elements with mass number A˜460. The experiment provides a test of nuclear models as well as experimental inputs for r-process calculations. This contribution presents the experimental setup and some preliminary results of the experiment.

Wu, J.; Nishimura, S.; Lorusso, G.; Xu, Z. Y.; Baba, H.; Browne, F.; Daido, R.; Doornenbal, P.; Fang, Y. F.; Ideguchi, E.; Isobe, T.; Li, Z.; Patel, Z.; Rice, S.; Simpson, G.; Sinclair, L.; Söderström, P. A.; Sumikama, T.; Watanabe, H.; Yagi, A.; Yokoyama, R.; Aoi, N.; Garrote, F. L. Bello; Benzoni, G.; Gey, G.; Gottardo, A.; Nishibata, H.; Odahara, A.; Sakurai, H.; Tanaka, M.; Taprogge, J.; Yamamoto, T.; Eurica Collaboration

2014-05-01

211

Geochemistry for Chemists.  

ERIC Educational Resources Information Center

A geochemistry course for chemists is described. Includes: (1) general course information; (2) subject matter covered; and (3) a consideration of the uses of geochemistry in a chemistry curriculum, including geochemical "real world" examples, geochemistry in general chemistry, and geochemistry as an elective. (JN)

Hostettler, John D.

1985-01-01

212

The provenance of Cretaceous to Quaternary sediments in the Tarfaya basin, SW Morocco: Evidence from trace element geochemistry and radiogenic Nd-Sr isotopes  

NASA Astrophysics Data System (ADS)

We present trace element compositions, rare earth elements (REEs) and radiogenic Nd-Sr isotope analyses of Cretaceous to recent sediments of the Tarfaya basin, SW Morocco, in order to identify tectonic setting, source rocks composition and sediments provenance. The results suggest that the sediments originate from heterogeneous source areas of the Reguibat Shield and the Mauritanides (West African Craton), as well as the western Anti-Atlas, which probably form the basement in this area. For interpreting the analyzed trace element results, we assume that elemental ratios such as La/Sc, Th/Sc, Cr/Th, Th/Co, La/Co and Eu/Eu? in the detrital silicate fraction of the sedimentary rocks behaved as a closed system during transport and cementation, which is justified by the consistency of all obtained results. The La/Y-Sc/Cr binary and La-Th-Sc ternary relationships suggest that the Tarfaya basin sediments were deposited in a passive margin setting. The trace element ratios of La/Sc, Th/Sc, Cr/Th and Th/Co indicate a felsic source. Moreover, chondrite-normalized REE patterns with light rare earth elements (LREE) enrichment, a flat heavy rare earth elements (HREE) and negative Eu anomalies can also be attributed to a felsic source for the Tarfaya basin sediments. The Nd isotope model ages (TDM = 2.0-2.2 Ga) of the Early Cretaceous sediments suggest that sediments were derived from the Eburnean terrain (Reguibat Shield). On the other hand, Late Cretaceous to Miocene--Pliocene sediments show younger model ages (TDM = 1.8 Ga, on average) indicating an origin from both the Reguibat Shield and the western Anti-Atlas. In contrast, the southernmost studied Sebkha Aridal section (Oligocene to Miocene-Pliocene) yields older provenance ages (TDM = 2.5-2.6 Ga) indicating that these sediments were dominantly derived from the Archean terrain of the Reguibat Shield.

Ali, Sajid; Stattegger, Karl; Garbe-Schönberg, Dieter; Frank, Martin; Kraft, Steffanie; Kuhnt, Wolfgang

2014-02-01

213

Study of rare earth element effect on microstructures and mechanical properties of an Al-Cu-Mg-Si cast alloy  

Microsoft Academic Search

The improvements of microstructures and properties of a high strength aluminum cast alloy were studied. The effects of rare earth elements on the microstructures and mechanical properties of the high strength cast alloy Al-Cu-Mg-Si were investigated. The result shows that the addition of rare earth elements can change the microstructures in refining the grain size of the alloy and making

Weiwei WAN; Jianmin HAN; Weijing LI; Jinhua WANG

2006-01-01

214

Palaeoenvironment of Northwestern India during the late Cretaceous Deccan volcanic episode from trace-element and stable-isotope geochemistry of intertrappean ostracod shells  

NASA Astrophysics Data System (ADS)

The Deccan Traps are flood basalts distributed widely across western and central peninsular India and formed at the end of the Cretaceous. The Deccan volcanism has been implicated in the mass extinctions that occurred at this time. Sediments preserved within the basalts are known as the Deccan intertrappeans. Many of the intertrappean rock sequences are fossiliferous and therefore provide an excellent opportunity to reconstruct terrestrial palaeoenvironments of peninsular India during the late Cretaceous. We evaluate the use of, and apply, trace-element (Mg/Ca and Sr/Ca) and stable isotope (?18O and ?13C) ratios from well-preserved ostracod shells, from intertrappean localities, with particular focus on one site, Lakshmipur, in northwestern India. We show that variations in preservation within well-defined limits do not appear to have significant effects on the geochemical signatures. Differences in stable isotope values between individual species are most likely related to species-specific offsets from equilibrium for oxygen, and differences in habitat for carbon. The geochemical data for the Lakshmipur section suggest that it represents a freshwater body that underwent significant evaporative enrichment, with evidence of wide variability in the aquatic environment on short timescales. These findings are broadly consistent with the palaeoecological evidence from this site and with other palaeoenvironmental reconstructions from the region. Any marine influence at this near-coastal site was probably too minor to have had any effect on the trace-element or stable isotope geochemistry of the ostracods at Lakshmipur, although other sites with palaeocological evidence for an unequivocal marine influence also show some geochemical signs of seawater intrusion. We conclude that the trace-element and stable isotope determinations of intertrappean ostracods have good potential for reconstructing late Cretaceous climate and aquatic environments.

Bajpai, Sunil; Holmes, Jonathan; Bennett, Carys; Mandal, Nivedita; Khosla, Ashu

2013-08-01

215

Volatile (sulphur and chlorine), major, and trace element geochemistry of mafic to intermediate tephras from the Chilean Southern Volcanic Zone (33-43°S)  

NASA Astrophysics Data System (ADS)

Here we present the first systematic investigation of volatile geochemistry along the Southern Volcanic Zone (SVZ) of Chile. Holocene olivine-hosted melt inclusions in the most mafic tephras sampled from 16 volcanoes along the volcanic front of the SVZ between 33°S and 43°S were analysed for pre-eruptive sulphur, chlorine, and major element contents. These results are combined with trace element compositions of the host whole rocks. The highest fractionation-corrected gas contents occur in the least-degassed melt inclusions from small monogenetic cones of Los Hornitos, Cabeza de Vaca, and Apagado from both the transitional and the southern-central SVZ, reaching ~3,000 ?g/g S and 1,400 ?g/g Cl, while the lowest abundances of ~1,100 ?g/g S and ~600 ?g/g Cl were found in the central SVZ at Volcán Lonquimay, Volcán Llaima, and Volcán Villarrica. Chlorine co-varies with trace element indicators for the degree of melting and/or source enrichment, such that the lowest Cl contents are found in high-degree melts from the most depleted mantle sources. The size of the volcanic edifices correlates inversely with Cl abundances in the melt. This could reflect more extensive degassing during ascent through the complex magma plumbing systems beneath the stratovolcanoes or greater dilution during larger degrees of melting of more depleted sources, or a combination of these factors. Compared to other subduction zones, the SVZ melt inclusions exhibit Cl and S abundances in the same range as most of those from the Central American and those from the Marianas arcs.

Wehrmann, Heidi; Hoernle, Kaj; Jacques, Guillaume; Garbe-Schönberg, Dieter; Schumann, Kai; Mahlke, Julia; Lara, Luis E.

2014-03-01

216

Anais do 2. Congresso Brasileiro de Geoquimica. (Proceedings of 2. Brazilian Geochemical Congress).  

National Technical Information Service (NTIS)

Some works about geochemistry are presented, including themes about geochemical exploration, lithogeochemistry and isotope geochemistry, environmental geochemistry, analytical geochemistry, geochemistry of carbonatites and rare earth elements and organic ...

1989-01-01

217

Origin of the earth's moon - Constraints from alkali volatile trace elements  

NASA Astrophysics Data System (ADS)

Although the moon is depleted in volatile elements compared to the earth, these depletions are not in accord with simple volatility. For example, the Cs/Rb ratios of the earth and moon inferred from basalt are approximately one seventh and one half of the CI ratio, respectively. Volatility considerations alone predict that the lunar Cs/Rb ratio should be equal to or lower than the terrestrial ratio if the moon was derived entirely from earth mantle material. Thus hypotheses such as rotational fission which invoke derivation of lunar material entirely from the earth's mantle may be excluded. The collisional ejection hypothesis of lunar origin requires at least 18 percent of lunar material to be derived from a projectile with dehydrated CI composition to match the lunar Cs/Rb ratio, and 25-50 percent to match both the lunar Cs/Rb ratio and absolute concentrations of Cs and Rb. It remains to be demonstrated that this relatively large contribution of projectile material is consistent with other elemental abundances and element ratios in the moon.

Kreutzberger, M. E.; Drake, M. J.; Jones, J. H.

1986-01-01

218

Major-element geochemistry of the Silent Canyon-Black Mountain peralkaline volcanic centers, northwestern Nevada Test Site: applications to an assessment of renewed volcanism  

USGS Publications Warehouse

The Silent Canyon and Black Mountain volcanic centers are located in the northern part of the Nevada Test Site. The Silent Canyon volcanic center is a buried cauldron complex of Miocene age (13-15 m.y.). Black Mountain volcanic center is an elliptical-shaped cauldron complex of late Miocene age. The lavas and tuffs of the two centers comprise a subalkaline-peralkaline association. Rock types range from quartz normative subalkaline trachyte and rhyolite to peralkaline comendite. The Gold Flat Member of the Thirsty Canyon Tuff (Black Mountain) is a pantellerite. The major-element geochemistry of the Black Mountain-Silent Canyon volcanic centers differs in the total range and distribution of Si02, contents, the degree of peralkalinity (molecular Na2O+K2O>Al2O3) and in the values of total iron and alumina through the range of rock types. These differences indicate that the suites were unrelated and evolved from differing magma bodies. The Black Mountain volcanic cycle represents a renewed phase of volcanism following cessation of the Timber Mountain-Silent Canyon volcanic cycles. Consequently, there is a small but numerically incalculable probability of recurrence of Black Mountain-type volcanism within the Nevada Test Site region. This represents a potential risk with respect to deep geologic storage of high-level radioactive waste at the Nevada Test Site.

Crowe, Bruce M.; Sargent, Kenneth A.

1979-01-01

219

Heavy metals and rare earth elements source-sink in some Egyptian cigarettes as determined by neutron activation analysis.  

PubMed

Heavy metals and rare earth elements in two types of cigarettes were studied. The contents of trace elements were determined by using delayed neutron activation analysis. In the present study 11 elements have been detected in popular and fine brand cigarettes marketed in Egypt. Evaluation of these elements with their potential hazards for smokers is briefly discussed. The material balance (source and sink) for each element was determined. Also the ratio of element recovery to the total amount was assessed. PMID:10376325

Nada, A; Abdel-Wahab, M; Sroor, A; Abdel-Haleem, A S; Abdel-Sabour, M F

1999-07-01

220

Improved provenance tracing of Asian dust sources using rare earth elements and selected trace elements for palaeomonsoon studies on the eastern Tibetan Plateau  

NASA Astrophysics Data System (ADS)

The Asian Monsoon forms an important part of the earth's climate system, yet our understanding of the past interactions between its different sub-systems, the East Asian and Indian monsoons, and between monsoonal winds and other prevailing wind currents such as the Westerly jet, is limited, particularly in central Asia. This in turn affects our ability to develop climate models capable of accurately predicting future changes in atmospheric circulation patterns and monsoon intensities in Asia. Provenance studies of mineral dust deposited in terrestrial settings such as peat bogs can address this problem directly, by offering the possibility to examine past deposition rates and wind direction, and hence reconstruct past atmospheric circulation patterns. However, such studies are challenged by several issues, most importantly the identification of proxies that unambiguously distinguish between the different potential dust sources and that are independent of particle size. In addition, a single analytical method that is suitable for sample preparation of both dust source (i.e. desert sand, soil) and receptor (i.e. dust archive such as peat or soil profiles) material is desirable in order to minimize error propagation derived from the experimental and analytical work. Here, an improved geochemical framework of provenance tracers to study atmospheric circulation patterns and palaeomonsoon variability in central Asia is provided, by combining for the first time mineralogical as well as major and trace elemental (Sc, Y, Th and the rare earth elements) information on Chinese (central Chinese loess plateau, northern Qaidam basin and Taklamakan, Badain Juran and Tengger deserts), Indian (Thar desert) and Tibetan (eastern Qinghai-Tibetan Plateau) dust sources. Quartz, feldspars and clay minerals are the major constituents of all studied sources, with highly variable calcite contents reflected in the CaO concentrations. Chinese and Tibetan dust sources are enriched in middle REE relative to the upper continental crust and average shale but the Thar desert has a REE signature distinctly different from all other dust sources. There are significant differences in major, trace and REE compositions between the coarse and fine fractions of the surface sands, with the finest <4 ?m fraction enriched in Al 2O 3, Fe 2O 3, MnO, MgO and K 2O and the <32 ?m fractions in Sc, Y, Th and the REE relative to the coarse fractions. The <4 ?m fraction best represents the bulk REE geochemistry of the samples. The provenance tracers Y/?REE, La/Er, La/Gd, Gd/Er, La/Yb, Y/Tb, Y/La, Y/Nd and to a certain extent the europium anomaly Eu/Eu ? (all REE normalized to post-Archean Australian shale, PAAS) are particle size-independent tracers, of which combinations of Y/?REE, La/Yb, Y/Tb, Y/La and Eu/Eu ? can be used to distinguish the Thar desert, the Chinese deserts, the Chinese loess plateau and the Tibetan soils. Their independence upon grain size means that these tracers can be applied to the long-range provenance tracing of Asian dust even when only bulk samples are available in the source region. Combinations of La/Th, Y/Tb, Y/?REE, Sc/La and Y/Er distinguish the Tibetan soils from the Chinese loess plateau and the Chinese deserts. La/Th and notably Th/?REE isolate the signature of the Badain Juran desert and the combination of Sc/La and Y/Er that of the Taklamakan desert. The similarity in all trace and REE-based provenance tracers between the northern Qaidam basin and Tengger desert suggests that these two deposits may have a common aeolian source.

Ferrat, Marion; Weiss, Dominik J.; Strekopytov, Stanislav; Dong, Shuofei; Chen, Hongyun; Najorka, Jens; Sun, Youbin; Gupta, Sanjeev; Tada, Ryuji; Sinha, Rajiv

2011-11-01

221

Contribution to the geochemistry of trace elements in the sediments of the Noun River and tributaries, western Cameroon.  

PubMed

This study reports on the distribution of trace elements in the sediments of the Noun River valley. Two groups of trace elements have emerged based on their distribution and geochemical behaviour. The first group shows lower values whereas the second group aligns higher values. Elements like Al and Sr in one side and Zn, Zr in the other present concentrations statistically different from those of the rocks compared to other elements in trace analyzed (Cr, Ni, Ba, Co, Cu, Fe, Mn, V, As and Pb). The trace elements Al, Sr, Zr, Zn and Pb in the sediments of the Noun River show concentrations rather lower than those of the world. The average concentrations in elements C (3.72%), N (0.27%), S (0.05%) and of the ratios C/N (13.77) and N/S (5.29) reflect those resulting from the decomposition of the organic matter which derives from soils with very small concentrations in S. The Noun valley sediments are mostly of primary (quartz, microcline, plagioclase, orthoclase, ilmenite, anatase) and newly formed or secondary (kaolinite, gibbsite, hematite, goethite) minerals. This mineralogy and the overall low concentration of the studied trace elements, with Al, Fe, Ti and Mn as most abundant elements, is consistent with the local geology made up of the basic rocks (basalts, volcanic ash) and of the acid rocks (granites, gneiss). Overall the trace elements concentration and distribution suggest their geogene origin. Yet, this study is a first contribution of its kind towards the development of a baseline geochemical database essential for a sustainable and healthier Noun valley ecosystem. PMID:19090098

Njofang, C; Matschullat, J; Tchouankoué, J P; Amougou, A

2007-09-15

222

Rare earth elements as nonabsorbable fecal markers in studies of iron absorption.  

PubMed

The use of rare earth elements as nonabsorbable fecal markers for studies of iron absorption from sources labeled extrinsically with stable isotopes was evaluated. On 3 successive days 13 healthy fasting adults were given different stable isotopes of iron with samarium, ytterbium, or dysprosium. On day 1, three meals were given with 57Fe (1 mg per meal) plus samarium (0.33 mg per meal); on day 2, identical meals (taken with a calcium supplement to reduce iron bioavailability) were given with equivalent amounts of 58Fe-labeled iron and ytterbium; on day 3, a well-absorbed reference dose of 54Fe (3 mg) was given with 1 mg Dy. A complete fecal collection was carried out for 5-9 d and each stool was analyzed for rare earth elements by inductively coupled plasma-mass spectrometry and iron isotopes by thermal ionization quadrupole mass spectrometry. Mean recovery of rare earth elements was 101%, indicating that they are totally unabsorbed. The excretory pattern of the iron isotopes and the rare earth elements was very similar; the correlation coefficients between samarium and 57Fe, ytterbium and 58Fe, and dysprosium and 54Fe were 0.992, 0.989, and 0.988, respectively (P < 0.001). Iron absorption was calculated as the difference between isotope dose and fecal excretion. Mean (+/-SEM) iron absorption was 16.7 +/- 2.4%, 4.3 +/- 1.6%, and 40.3 +/- 3.1% on days 1-3, respectively. Predicted values estimated from the first 4 d of pooled feces, using the rare earth element recovery data to produce corrected figures for unabsorbed isotope, were in close agreement: 19.1 +/- 2.1%, 4.6 +/- 1.7%, and 40.8 +/- 3.1%, respectively (P < 0.001). With the diet of medium iron bioavailability and with the highly bioavailable reference dose it was possible to predict iron absorption accurately from only one or two stools, provided that they were sufficiently enriched with isotope and a rare earth element. PMID:9094881

Fairweather-Tait, S J; Minihane, A M; Eagles, J; Owen, L; Crews, H M

1997-04-01

223

Structural Responses and Finite Element Modeling of Hakka Tulou Rammed Earth Structures  

NASA Astrophysics Data System (ADS)

Hakka Tulous are rammed earth structures that have survived the effects of aging and natural elements upwards of even over a thousand years. These structures have housed the Hakka people of the Fujian Province, China in natural yet modern housing that has provided benefits over newer building materials. The key building material, rammed earth, which is used for the walls of the Hakka Tulou structures, has provided structural stability along with thermal comfort to the respective inhabitants of the Hakka Tulous. Through material testing and analysis this study has examined how the Tulou structures have maintained their structural stability while also providing thermal comfort. Reports of self healing cracks in the rammed earth walls were also analyzed for their validity in this study. The study has found that although the story of the self healing crack cannot be validated, there is reason to believe that with the existence of lime, some type of autogenous healing could occur on a small scale. The study has also found, through the use of nondestructive testing, that both the internal wooden systems (flooring, roof, and column support) and the rammed earth walls, are still structurally sound. Also, rammed earth's high thermal mass along with the use of sufficient shading has allowed for a delay release of heat energy from the walls of the Tulous, thus providing thermal comfort that can be felt during both night and day temperatures. The Hakka Tulou structures have been found to resist destruction from natural disasters such as strong earthquakes even when more modern construction has not. Through finite element modeling, this study has shown that the high volume of rammed earth used in the construction of the Hakka Tulous helps dissipate lateral force energy into much lower stresses for the rammed earth wall. This absorption of lateral force energy allows the rammed earth structures to survive even the strongest of earthquakes experienced in the region. The Hakka Tulou, if rated by the LEED green building certification program, would earn the highest certification as this rammed earth construction has offered efficient living for hundreds of years. As historic as these rammed earth structures are, they present an environmentally friendly option to structures of the future.

Sranislawski, Daniel

224

Thermal effects on rare earth element and strontium isotope chemistry in single conodont elements  

Microsoft Academic Search

A low-blank, high sensitivity isotope dilution, ICP-MS analytical technique has been used to obtain REE abundance data from single conodont elements weighing as little as 5 ?g. Sr isotopes can also be measured from the column eluants enabling Sr isotope ratios and REE abundance to be determined from the same dissolution. Results are comparable to published analyses comprising tens to

H. A. Armstrong; D. G. Pearson; M. Griselin

2001-01-01

225

Trace Element Geochemistry of Oceanic Peridotites and Silicate Melt Inclusions: Implications for Mantle Melting and Ocean Ridge Magmagenesis.  

National Technical Information Service (NTIS)

The mantle melting process is fundamental to describing basalt genesis and crustal accretion at mid-ocean ridges. The dissertation examines the trace element compositions of abyssal peridotites and discusses how they preserve details of the melting proces...

K. T. M. Johnson

1990-01-01

226

Trace Element and Isotope Geochemistry of Cretaceous-Tertiary Boundary Sediments: Identification of Extra-Terrestrial and Volcanic Components.  

National Technical Information Service (NTIS)

Trace element and stable isotope analyses were performed on a series of sediment samples crossing the Cretaceous-Tertiary (K-T) boundary from critical sections at Aumaya and Sopelano, Spain. The aim is to possibly distinguish extraterrestrial vs. volcanic...

S. V. Margolis E. F. Doehne

1988-01-01

227

Radiogenic isotopes: systematics and applications to earth surface processes and chemical stratigraphy  

Microsoft Academic Search

Radiogenic isotopes have wide application to chemical stratigraphy, geochronology, provenance studies, and studies of temporal changes in Earth surface processes. This paper briefly reviews the principles of radiogenic isotope geochemistry and the distribution of a number of elements of interest in the environment, and then uses this information to explore the range of applications to chemical stratigraphy and other fundamental

Jay L. Banner

2004-01-01

228

Principles and Applications of Geochemistry, 2nd Edition  

NASA Astrophysics Data System (ADS)

Many academic geology departments do not include geochemistry in their undergraduate core curriculums. The second edition of Principles and Applications of Geochemistry demonstrates why this should change. Gunter Faure's book clearly shows the important role played by quantitative geochemical analysis in our understanding of Earth processes, both natural and anthropogenic. Intended as an introductory inorganic geochemistry text for senior undergraduates or first-year graduate students, the book makes even the most difficult concepts readily understandable. Beyond its lucid technical explanations, it also includes engaging discussions of the history of geochemistry as a science.

Marcantonio, Franco

229

Synthesis of aluminum garnets of rare-earth elements and yttrium with combined deposition of hydroxides  

SciTech Connect

This work is concerned with the study of the mechanism of the formation of aluminum garnets of rare-earth elements as well as the conditions for their synthesis by the method of combined deposition of hydroxides. The deposition was conducted by continuously dripping a mixture of a 0.5 M solution of nitric acid salts of aluminum and rare-earth elements or yttrium into a 1 M solution of ammonium hydroxide while constantly mixing the suspension and monitoring the pH (9.5-10). The deposits were filtered, flushed with distilled water, and dried at 100-150/sup 0/C. The impurity content in the starting reagents did not exceed 10/sup -2/ mass %. The studies were carried out by means of thermal, complex thermal, and x-ray phase analysis.

Glushkova, V.B.; Zinov'ev, S.Yu.; Krzhizhanovskaya, V.A.; Kuznetsov, A.K.

1986-12-01

230

Refertilization of ancient lithospheric mantle beneath the central North China Craton: Evidence from petrology and geochemistry of peridotite xenoliths  

Microsoft Academic Search

The petrology and geochemistry of peridotite xenoliths in the Cenozoic basalts from Fanshi, the central North China Craton (NCC), provide constraints on the evolution of sub-continental lithospheric mantle. These peridotite xenoliths are mainly spinel-facies lherzolites with minor harzburgites. The lherzolites are characterized by low forsterite contents in olivines (Fo<91) and light rare earth element (LREE) enrichments in clinopyroxenes. In contrast,

Yan-Jie Tang; Hong-Fu Zhang; Ji-Feng Ying; Jin Zhang; Xiao-Ming Liu

2008-01-01

231

Dripwater organic matter and trace element geochemistry in a semi-arid karst environment: Implications for speleothem paleoclimatology  

NASA Astrophysics Data System (ADS)

A series of four short-term infiltration experiments which revealed hydrochemical responses relevant to semi-arid karst environments were carried out above Cathedral Cave, Wellington, New South Wales (NSW), Australia. Dripwater samples were collected at two sites for trace element and organic matter analysis. Organic matter was characterised using fluorescence and interpreted using a PARAFAC model. Three components were isolated that represented unprocessed, soil-derived humic-like and fulvic-like material, processed humic/fulvic-like material and tryptophan-like fluorescence. Principal Component Analysis (PCA) performed on the entire dataset comprising trace element concentrations and PARAFAC scores revealed two dominant components that were identified as soil and limestone bedrock. The soil component was assigned based on significant contributions from the PARAFAC scores and additionally included Ba, Cu, Ni and Mg. The bedrock component included the expected elements of Ca, Mg and Sr as well as Si. The same elemental behaviour was observed in recent stalagmite growth collected from the site. Our experiments demonstrate that existing paleoclimate interpretations of speleothem Mg and Sr, developed in regions of positive water balance, are not readily applicable to water limited environments. We provide a new interpretation of trace element signatures unique to speleothems from water limited karst environments.

Rutlidge, Helen; Baker, Andy; Marjo, Christopher E.; Andersen, Martin S.; Graham, Peter W.; Cuthbert, Mark O.; Rau, Gabriel C.; Roshan, Hamid; Markowska, Monika; Mariethoz, Gregoire; Jex, Catherine N.

2014-06-01

232

Composition of the earth's upper mantle. II - Volatile trace elements in ultramafic xenoliths  

NASA Technical Reports Server (NTRS)

Radiochemical neutron activation analysis was used to determine the nine volatile elements Ag, Bi, Cd, In, Sb, Se, Te, Tl, and Zn in 19 ultramafic rocks, consisting mainly of spinel and garnet lherzolites. A sheared garnet lherzolite, PHN 1611, may approximate undepleted mantle material and tends to have a higher volatile element content than the depleted mantle material represented by spinel lherzolites. Comparisons of continental basalts with PHN 1611 and of oceanic ridge basalts with spinel lherzolites show similar basalt: source material partition factors for eight of the nine volatile elements, Sb being the exception. The strong depletion of Te and Se in the mantle, relative to lithophile elements of similar volatility, suggests that 97% of the earth's S, Se and Te may be in the outer core.

Morgan, J. W.; Wandless, G. A.; Petrie, R. K.; Irving, A. J.

1980-01-01

233

Distribution of alkaline earth elements between aqueous solutions and polymeric sorbent impregnated with 8-hydroxyquinoline  

SciTech Connect

The interphase distribution of microimpurities of alkaline earth elements (AEE) between solutions of alkali metal chlorides and a macroporous styrene-divinyl-benzene copolymer impregnated with 8-hydroxyquinoline was studied. The influence of the phase composition on the distribution coefficients of AEE and 8-hydroxyquinoline was examined. The advantages of sorption of the impurities by an impregnated sorbent over liquid extraction for thorough purification of salt solutions were shown.

Turanov, A.N.; Kremenskaya, I.N.; Putrya, L.V.

1987-07-01

234

Encapsulation of the platinum and neighboring metals within cluster iodides of rare-earth elements  

Microsoft Academic Search

Syntheses of new cluster phases containing encapsulated heterometals have been explored through reactions between the rare-earth metal Y, Pr, or Gd (R), RIâ, and a 3d, 4d, or 5d element (Z) at 750-1,000°C in sealed Nb containers. New PrâIââZ (SCâClââN-type) phases are obtained for Z = Cu, Ru, Rh, Pd, Re, Os, Ir, and Pt. New GdâIââZ phases occur for

Martin W. Payne; John D. Corbett

1990-01-01

235

Seawater rare-earth element patterns preserved in apatite of Pennsylvanian conodonts?  

Microsoft Academic Search

Past workers have used rare-earth element patterns recorded in biogenic apatite as proxies for original seawater chemistry. To explore the potency of this approach, we analyzed Pennsylvanian conodonts from limestones, gray shales, and black shales of the Fort Scott and Pawnee formations (Desmoinesian) and Swope and Dennis formations (Missourian) in Kansas, Missouri, and Iowa, U.S.A. Analysis of individual platform conodonts

Camomilia A. Bright; Anna M. Cruse; Timothy W. Lyons; Kenneth G. MacLeod; Michael D. Glascock; Raymond L. Ethington

2009-01-01

236

Cathodoluminescence of synthetic (doped with rare-earth elements) and natural anhydrites  

Microsoft Academic Search

In order to interpret cathodoluminescence (CL) spectra of natural anhydrites, synthetic crystals were indirectly obtained by precipitation of gypsum from solutions containing doping rare-earth elements (REE), and by transformation into anhydrite by dehydration at 800°C during 3 h. Analyses by ICP-MS of several anhydrites obtained from solutions containing 130 ppm of REE clearly showed that light REE (LREE) can be

A. Baumer; Ph. Blanc; F. Cesbron; D. Ohnenstetter

1997-01-01

237

A new highT(c) oxide superconductor without a rare earth element  

Microsoft Academic Search

A new high-T(c) oxide superconductor of the Bi-Sr-Ca-Cu-O system without any rare earth element was discovered. The oxide BiSrCaCu2O(x) has T(c) of about 105 K, higher than that of YBa2Cu3O7 by more than 10 K. In this oxide, the coexistence of Sr and Ca is necessary to obtain high T(c).

Hiroshi Maeda; Yoshiaki Tanaka; Masao Fukutomi; Toshihisa Asano

1988-01-01

238

Rare earth and high field strength element partitioning between iron-rich clinopyroxenes and felsic liquids  

Microsoft Academic Search

Rare earth elements are commonly assumed to substitute only for Ca in clinopyroxene because of the similarity of ionic radii\\u000a for REE3+ and Ca2+ in eightfold coordination. The assumption is valid for Mg-rich clinopyroxenes for which observed mineral\\/melt partition coefficients\\u000a are readily predicted by the lattice strain model for substitution onto a single site (e.g., Wood and Blundy 1997). We

P. H. OlinJ; J. A. Wolff

2010-01-01

239

Trace element geochemistry of zircons from mineralizing and non-mineralizing igneous rocks related to gold ores at Yanacocha, Peru  

NASA Astrophysics Data System (ADS)

Zircons record important details about the evolution of magmatic systems, are relatively insensitive to alteration, and have been used to investigate the geochemistry, temperature, and oxidation state of volcanic and plutonic system. We examine zircons that span 6-7 m.y. of calc-alkaline volcanic activity in the Yanacocha district of northern Peru, where dacitic intrusions are associated with high-sulfidation gold deposits. The 14.5-8.4 Ma Yanacocha Volcanics include cogenetic lavas and pyroclastic rocks and are underlain by the andesites and dacites of the Calipuy Group, the oldest Cenozoic rocks in the region. We present data for magmatic zircons from the Cerro Fraile dacitic pyroclastics (15.5-15.1 Ma) of the Calipuy Group, and multiple eruptive units within the younger Yanacocha Volcanics: the Atazaico Andesite (14.5-13.3 Ma), the Quilish Dacite (~14-12 Ma), the Azufre Andesite (12.1-11.6 Ma), the San Jose Ignimbrite (11.5-11.2 Ma), and the Coriwachay Dacite (11.1-8.4 Ma). Epithermal high sulfidation (alunite-bearing) gold deposits are associated with the dacite intrusions of the Coriwachay and Quilish Dacites. Zircons from the non-mineralizing rocks typically have lower Hf concentrations and record Ti-in-zircon temperatures that are ~100°C hotter than zircons from the mineralizing intrusions. Temperatures recorded by zircons from the mineralizing intrusions are remarkably similar to those of the underlying Cerro Fraile dacite pyroclastics, but the zircons discussed here generally record SHRIMP-RG 206Pb/238U ages within error of previously published Ar-Ar eruption ages (eliminating antecrystic or xenocrystic origins). These observations suggest that zircons in the mineralizing intrusions form after greater extents of crystallization (and thus record elevated Hf concentrations and lower temperatures) than do zircons in the non-mineralized deposits. Unlike zircons from mineralized units associated with the porphyry Cu(Mo) deposits in Yerington, Nevada, which generally have Eu/Eu* ratios approaching 1 (i.e., Eu-anomalies that decrease in magnitude) with increasing Hf (and thus increasing crystallization), zircons associated with mineralized deposits in the Coriwachay and Quilish intrusions at Yanacocha typically have Eu-anomalies that are highly variable but do not vary systematically during magma evolution. These Eu/Eu* versus Hf trends are inconsistent with observations from the porphyry Cu-Mo(Au) deposit at El Salvador, Chile, where zircons from all porphyry intrusions have Eu-anomalies that become systematically more negative during magma evolution but with highest Eu/Eu* occurring in mineralized intrusions. We explore a variety of scenarios to explain the Eu/Eu* systematics of zircons from Yanacocha, including changes to the magmatic oxidation state as a consequence of anhydrite breakdown and progressive degassing.

Koleszar, A. M.; Dilles, J. H.; Kent, A. J.; Wooden, J. L.

2012-12-01

240

Trace and Rare-Earth Element Geochemistry of the Karalar (Gazipafla—Antalya) Barite-Galena Deposits, Southern Turkey  

Microsoft Academic Search

The Karalar barite-galena deposits are typical examples of carbonate-hosted barite-galena deposits that occur widely in the central Taurides. Recent mining activity has been concentrated in the Büyük and Boyal›k mine areas. The mineralisation occurs as ore veins along fault zones and as ore-filled breccia zones along the strongly deformed lower walls of limestone blocks in the Permian limestones of the

GÜLCAN BOZKAYA; AHMET GÖKÇE; Nadir Toprak; Element Jeokimyas; Güney Türkiye

2004-01-01

241

Transport of rare earth element-tagged soil particles in response to thunderstorm runoff.  

PubMed

The downslope transport of rare earth element-tagged soil particles remobilized during a spring thunderstorm was studied on both a natural prairie and an agricultural field in southwestern Iowa (U.S.A.). A technique was developed for tagging natural soils with the rare earth elements Eu, Tb, and Ho to approximately 1,000 ppm via coprecipitation with MnO2. Tagged material was replaced in target locations; surficial soil samples were collected following precipitation and runoff; and rare earth element concentrations were determined by inductively coupled plasma mass spectrometry. Diffusion and exponential models were applied to the concentration-distance data to determine particle transport distances. The results indicate that the concentration-distance data are well described by the diffusion model, butthe exponential model does not simulate the rapid drop-off in concentrations near the tagged source. Using the diffusion model, calculated particle transport distances at all hillside locations and at both the cultivated and natural prairie sites were short, ranging from 3 to 73 cm during this single runoff event. This study successfully demonstrates a new tool for studying soil erosion. PMID:11529577

Matisoff, G; Ketterer, M E; Wilson, C G; Layman, R; Whiting, P J

2001-08-15

242

Evaluating rare earth element availability: a case with revolutionary demand from clean technologies.  

PubMed

The future availability of rare earth elements (REEs) is of concern due to monopolistic supply conditions, environmentally unsustainable mining practices, and rapid demand growth. We present an evaluation of potential future demand scenarios for REEs with a focus on the issue of comining. Many assumptions were made to simplify the analysis, but the scenarios identify some key variables that could affect future rare earth markets and market behavior. Increased use of wind energy and electric vehicles are key elements of a more sustainable future. However, since present technologies for electric vehicles and wind turbines rely heavily on dysprosium (Dy) and neodymium (Nd), in rare-earth magnets, future adoption of these technologies may result in large and disproportionate increases in the demand for these two elements. For this study, upper and lower bound usage projections for REE in these applications were developed to evaluate the state of future REE supply availability. In the absence of efficient reuse and recycling or the development of technologies which use lower amounts of Dy and Nd, following a path consistent with stabilization of atmospheric CO(2) at 450 ppm may lead to an increase of more than 700% and 2600% for Nd and Dy, respectively, over the next 25 years if the present REE needs in automotive and wind applications are representative of future needs. PMID:22304002

Alonso, Elisa; Sherman, Andrew M; Wallington, Timothy J; Everson, Mark P; Field, Frank R; Roth, Richard; Kirchain, Randolph E

2012-03-20

243

Trace element geochemistry of scheelite and rutile from metaturbidite-hosted quartz vein gold deposits, Meguma Terrane, Nova Scotia, Canada: genetic implications  

NASA Astrophysics Data System (ADS)

Scheelite and rutile from several metaturbidite-hosted gold-bearing quartz vein deposits of the Meguma Terrane of Nova Scotia were analyzed for trace elements including rare earth elements, niobium and tantalum. Scheelites have high concentrations of Sr, Nb, Y and rare earth elements (REE) with bell-shaped chondrite-normalized REE patterns accompanied by both positive and negative Eu anomalies. They also have high Nb/Ta ratios (80-300). Three distinct trace element types of the scheelites are interpreted to reflect chemical differences in the pulses of hydrothermal fluids. Hydrothermal rutiles have high contents of W (up to 4.2 wt.% WO3), are rich in Ta compared to Nb and have a very low Nb/Ta ratio (~0.3). Hydrothermal fluids which produced both scheelite with a high Nb/Ta and rutile with a low Nb/Ta ratio are an efficient medium for fractionation of this ratio although these two minerals play an important role during the process.

Dostal, Jaroslav; Kontak, Daniel J.; Chatterjee, A. K.

2009-12-01

244

Evidence for a Magmatic Source of Heat for the Steamboat Springs Geothermal System Using Trace Elements and Gas Geochemistry  

Microsoft Academic Search

The objective of this project is the development of a representa- tive geochemical database for a comprehensive suite of elemental and isotopic parameters (i.e., beyond the typical data suite) for geo- thermal fluids in the Great Basin. Preliminary assessment suggests that there are significant differences between magmatic-driven and extensional geothermal systems. In particular, fluids in magmatic systems have higher concentrations

Greg B. Arehart; Mark F. Coolbaugh; Simon R. Poulson

245

Distribution coefficients of 60 elements on TODGA resin: application to Ca, Lu, Hf, U and Th isotope geochemistry.  

PubMed

Batch equilibration experiments are conducted to measure the distribution coefficients (K(d)) of a large number of elements in nitric, nitric plus hydrofluoric, and hydrochloric acids on Eichrom TODGA extraction chromatography resin. The K(d)s are used to devise a multi-element extraction scheme for high-precision elemental and isotopic analyses of Ca, Hf, Lu, Th and U in geological materials, using high-purity lithium metaborate (LiBO(2)) flux fusion that allows rapid digestion of even the most refractory materials. The fusion melt, dissolved in nitric acid, is directly loaded to a TODGA cartridge on a vacuum chamber for elemental separation. An Ln-Spec cartridge is used in tandem with TODGA for Lu purification. The entire procedure, from flux digestion to preparation for isotopic analysis, can be completed in a day. The accuracy of the proposed technique is tested by measuring the concentrations of Ca (standard bracketing), Hf, Lu, Th and U (isotope dilution), and the isotopic composition of Hf in geostandards (USNM3529, BCR-2, BHVO-1, AGV-1 and AGV-2). All measurements are in excellent agreement with recommended literature values, demonstrating the effectiveness of the proposed analytical procedure and the versatility of TODGA resin. PMID:20298848

Pourmand, Ali; Dauphas, Nicolas

2010-05-15

246

The atmospheric transport and deposition of smelter emissions: evidence from the multi-element geochemistry of snow, Quebec, Canada  

NASA Astrophysics Data System (ADS)

Abundances of 35 elements and ions were determined by inductively coupled plasma mass spectrometry, inductively coupled plasma atomic emission spectroscopy, and ion chromatography, in samples of snowpack obtained using ultraclean procedures, along three 50-km radial transects emanating from the Horne base metal smelter in Rouyn-Noranda, Quebec. This was done to constrain: what is emitted; regional background concentrations of elements in snow; the rate of anthropogenic deposition on the surrounding landscape; how far emissions are transported; and what processes control their deposition. The approach used is at least as effective as methods based on isotopic ratios but has the added advantage of providing direct constraint on a large suite of elements, and of being independent of changes in the isotopic composition of emissions. Reproducibility of the method was determined using field duplicates and blanks. This accounts for snow heterogeneity, analytical precision, reagent quality, and sample handling and was determined to be ±20%. Concentrations of Cu, Pb, and Zn near the smelter are 525, 353, and 149 ?g/L meltwater, respectively, and drop to 2.1, 3.5, and 3.1 ?g/L by 45 km distance. The level of enrichment of these elements, relative to upper crustal abundances, similarly drops from about 10,000 to 100 from proximal through to distal sites, forming an "enrichment gradient." This is the result of a binary mix of smelter emissions and regional background concentrations. Elements that display a significant gradient must therefore be emitted by the smelter. This method shows that Cu, Ag, In, Sb, Pb, As, Tl, Mo, Zn, Cd, Co, Be, Ni, Na, Ba, Fe, Cr, V, Ti, Y, Al, U, Ce, Li, S, La, and Sr are deposited on the landscape by the smelter. For many elements, the slope of this binary mixing line is still non-zero at a distance of 50 km, indicating that the impact of the smelter is still detectable, and that regional background levels have not yet been reached. Data from more distant sites are used to estimate regional background concentrations to be 1.1, 1.7, and 1.6 ?g/L meltwater for Cu, Pb, and Zn, respectively. We quantify the partitioning of elements between the dissolved phase (meltwater) and the solid phase (particulates) in melted snow. It varies with distance from the smelter but is element specific. Representative end-members are: Tl, Cu, Pb, Zn, and Sb with 78, 68, 67, 55, and 20% in the dissolved phase near the smelter, respectively, vs. 4, 60, 73, 80, 58% at distances greater than 35 km. This is due to changes in mineralogy and particle size. The significance of this is, that for those elements with high variation such as Tl and Sb, only the total load (meltwater + particulate) can reliably reflect atmospheric deposition. For those elements that vary little such as Cu and Pb, measurement of just the dissolved load (meltwater) can be used as an adequate proxy for the total deposition. Observed patterns of deposition suggest that inside 15 km radius, it occurs by wet+dry mechanisms whereas beyond 15 km wet deposition dominates. Emissions transported beyond 15 km are therefore available for long-range transport during dry weather and likely have an atmospheric residence time similar to that of water vapour. A well fitting mathematical model supports this interpretation. Using modelled background concentrations, the model can account for only 49, 15, 23, and 9% of reported emissions of Cu, Pb, Zn, and Cd within 50 km of the smelter, respectively. Using lower (minimal) background concentrations based on observations at more distant sites, these numbers increase to 78, 19, and 43%, respectively (Cd excluded), and can be considered maximums. The rest of the emissions are therefore transported further distances during dry weather.

Telmer, Kevin; Bonham-Carter, Graeme F.; Kliza, Deborah A.; Hall, Gwendy E. M.

2004-07-01

247

Introduction to urban watershed geochemistry  

NSDL National Science Digital Library

The main goal of this multi-part field and lab exercise is to introduce students to practical aspects of soil and water geochemistry. Some of the analyses for this lab are conducted in the field using field analytical instruments and rest of the analyses is conducted in a wet chemistry/geochemistry lab. There are several objectives: 1. Learn how to sample water and soil samples in a safe and effective manner 2. Collect basic aqueous chemical parameters in the field 3. Compare field collected data with that obtained using advanced instruments in the laboratory 4. Determine bulk physical and chemical properties of the soils in the lab 5. Determine trace and major element concentrations of the soils in the laboratory At the end of this exercise students will gain a better appreciation for how soil and water quality is assessed in multiple ways. They are also introduced to basic "tools-of-the-trade" in the environmental geochemistry and also using Excel to make simple and advanced calculations as well as for plotting data. During preparation of lab reports, they are introduced to basic elements of an effective data-based technical paper. Key words: urban watershed, soil chemistry, water chemistry, aqueous geochemistry, field analysis, analytical chemistry

Vulava, Vijay

248

Medical geochemistry of tropical environments  

NASA Astrophysics Data System (ADS)

Geochemically, tropical environments are unique. This uniqueness stems from the fact that these terrains are continuously subjected to extreme rainfall and drought with resulting strong geochemical fractionation of elements. This characteristic geochemical partitioning results in either severe depletion of elements or accumulation to toxic levels. In both these situations, the effect on plant, animal and human health is marked. Medical geochemistry involves the study of the relationships between the geochemistry of the environment in which we live and the health of the population living in this particular domain. Interestingly, the relationships between geochemistry and health are most marked in the tropical countries, which coincidentally are among the poorest in the world. The very heavy dependence on the immediate environment for sustainable living in these lands enables the medical geochemist to observe correlations between particular geochemical provinces and the incidence of certain diseases unique to these terrains. The aetiology of diseases such as dental and skeletal fluorosis, iodine deficiency disorders, diseases of humans and animals caused by mineral imbalances among others, lie clearly in the geochemical environment. The study of the chemistry of the soils, water and stream sediments in relation to the incidence of geographically distributed diseases in the tropics has not only opened up new frontiers in multidisciplinary research, but has offered new challenges to the medical profession to seriously focus attention on the emerging field of medical geochemistry with the collaboration of geochemists and epidemiologists.

Dissanayake, C. B.; Chandrajith, Rohana

1999-10-01

249

Geochemistry of Snowball Earth glacial tillites from China and North America: implications for the bulk composition of the Neoproterozoic upper crust  

NASA Astrophysics Data System (ADS)

In order to understand the differentiation of the Earth and growth of continents through time, it is critical to have reliable estimates for the average composition of the continental crust. Attempts to develop average compositional models for the upper continental crust have often relied upon the analysis of sediments and sedimentary rocks, based on the assumption that these provide natural averages of large crustal areas. Shales are among the most frequently used proxies, although some workers have also studied loess. The advantage of loess, especially that which is derived from glacial processes, is that it is typically produced by physical weathering alone and should lack the elemental fractionation produced by chemical weathering. Glacial tillites should also provide this advantage, and in addition, they should lack element fractionation caused by eolian particle sorting that is observed in loess. Here, we present new major and trace element data for glacial tillites from the Neoproterozoic, collected in southern China and the eastern U.S. Samples were collected from tillites of the Marinoan(?) Nantuo and Sturtian Gucheng Formations in Hubei Province, China (n = 21), and the Sturtian Konnarock Formation in the Appalachians of southwestern Virginia (n = 11). Values for the chemical index of alteration (Al2O3/Al2O3+K2O+Na2O+CaO) for these rocks are low, between 60 and 70 for most of the Chinese samples and 53 and 60 for all of the American ones, reflecting derivation from material that has experienced very little chemical weathering. The individual samples from the two localities show remarkable homogeneity, but their average compositions are distinct. The Chinese tillites match more closely the average upper crust composition of Rudnick and Gao (2003) than the Virginia ones, but the former still show a few major differences. Select soluble elements, such as Sr, Tl, and U, are depleted by as great a factor as ten, whereas other soluble elements, such as Li, Rb, and Cs, are either enriched or similar to the upper crustal model. By contrast, the Virginia tillites show major enrichment in the high field strength elements and rare earth elements, and depletion in the first row transition metals associated with mafic minerals (e.g., Ni, Cr, Sc, V). These tillites also show a stronger negative Eu anomaly. The difference between the Chinese and Virginia Neoproterozoic tillites likely reflects the different provenance of the Virginia samples, but in detail, the implications of this observation are unclear. The Virginia tillite chemistry is similar to local Neoproterozoic A-type granites in the Appalachians, but is also similar to the regionally extensive Grenvillian basement. This is an important distinction, as it goes to the question of whether or not the till represents the integration of a large area, as opposed to being primarily locally derived. In the case of the Chinese tillites, published detrital zircon and whole-rock Nd isotopic data suggests the provenance encompassed a large crustal area, strengthening their legitimacy as a proxy for the average upper crust.

Gaschnig, R. M.; Rudnick, R. L.; McDonough, W. F.; Gao, S.; Hu, Z.; Zhou, L.

2012-12-01

250

Toward understanding early Earth evolution: Prescription for approach from terrestrial noble gas and light element records in lunar soils  

PubMed Central

Because of the almost total lack of geological record on the Earth's surface before 4 billion years ago, the history of the Earth during this period is still enigmatic. Here we describe a practical approach to tackle the formidable problems caused by this lack. We propose that examinations of lunar soils for light elements such as He, N, O, Ne, and Ar would shed a new light on this dark age in the Earth's history and resolve three of the most fundamental questions in earth science: the onset time of the geomagnetic field, the appearance of an oxygen atmosphere, and the secular variation of an Earth–Moon dynamical system.

Ozima, Minoru; Yin, Qing-Zhu; Podosek, Frank A.; Miura, Yayoi N.

2008-01-01

251

G3 (Geochemistry, Geophysics, Geosystems)  

NSDL National Science Digital Library

_G3 (Geochemistry, Geophysics, Geosystems)_ is a forthcoming electronic journal that will be issued by the Geochemical Society and the American Geophysical Union (AGU). This journal publishes "relevant observational, experimental, and theoretical investigations of the solid Earth, hydrosphere, atmosphere, and biosphere that pertain to understanding the Earth as a system." Scientists interested in contributing to this journal must submit material electronically via a Web form. Although a starting date of publication has not been mentioned at the Website, email announcements will be sent to subscribers (subscription is free) once the journal begins publication.

252

Reconciling the elemental and Sr isotope composition of Himalayan weathering fluxes: insights from the carbonate geochemistry of stream waters  

Microsoft Academic Search

Determining the relative proportions of silicate vs. carbonate weathering in the Himalaya is important for understanding atmospheric CO2 consumption rates and the temporal evolution of seawater Sr. However, recent studies have shown that major element mass-balance equations attribute less CO2 consumption to silicate weathering than methods utilizing Ca\\/Sr and 87Sr\\/86Sr mixing equations. To investigate this problem, we compiled literature data

ANDREW D. JACOBSON; J OEL D. BLUM; LYNN M. WALTER

2002-01-01

253

Geochemistry of Fresh Submarine HSDP-2 Glasses from Mauna Kea Volcano: Unexpected Mobility of 'Immobile' Trace Elements  

NASA Astrophysics Data System (ADS)

The Hawaii Scientific Drilling Project-2 provides the opportunity to investigate the geochemical evolution of the submarine section of Mauna Kea. Our previous analyses of bulk-rock trace element concentrations had revealed relatively high degrees of scatter of trace element ratios such as Th/U, Ta/U and even Nb/Ta, and we suspected that many of the samples had been affected by seawater alteration. Fortunately, fresh glasses are found throughout the drill core in many glass-rich hyaloclastic and pillow basalts with glass proportions up to 10%. We therefore determined incompatible trace elements such as Th, U, Nb, Ta, Zr, Ba, Pb, Rb in carefully handpicked, fresh glasses in 16 samples derived from depths between 1310 m and 3050 m. The samples were crushed to less than 0.425 mm grain size in order to obtain very fresh glass fragments free of contamination by alteration products, olivines or other minerals. The glass fractions and their corresponding bulk samples were analyzed for major and trace elements by EMP, MIC-SSMS and HR-ICPMS. The differences between glass and bulk are particularly obvious in Pb, Rb, Cs and U. As expected, Pb, Rb and Cs were found to be mobile, with concentrations in the bulk samples varying by up to a factor of 5 relative to the glass samples. Similarly, U concentrations in glass are up to a factor of 2 higher than in bulk samples. More surprising is the observation that Th and Ta are quite probably mobile, because these elements are normally believed to be immobile. However, these results are consistent with those of Bienvenue et al. (1990), who found that Th appears to be sensitive to seawater alteration. Our glass data indicate that Ta/U (3.7+/-0.2) is uniform along the sequence, in contrast to the bulk data which show a large scatter (3.7-6.5). Th/U ratios in the glasses show a maximum (~3.5) at a depth of ~2100 m, whereas low ratios of about 3 were found in depths of 1300-1400 m and 2800-3000 m. The high Th/U ratios in the 2100 m region are associated with low SiO2 contents, high 208Pb*/206Pb*(Eisele et al., 2002; Blichert-Toft et al., 2002) and high 3He/4He ratios (Kurz, personal comm., Althaus et al., 2002). Thus, it appears that the high Th/U values are not caused by melting effects but are features of an anomalous source chemistry sampled by the volcano at this stratigraphic level.

Amini, M. A.; Jochum, K. P.; Stoll, B.; Willbold, M.; Sobolev, A. V.; Hofmann, A. W.

2002-12-01

254

The 2 Ga peraluminous magmatism of the Jacobina — Contendas Mirante Belt (Bahia) Brazil): Major and trace-element geochemistry and metallogenic potential  

NASA Astrophysics Data System (ADS)

The Jacobina — Contendas Mirante belt represents a Transamazonian (2 Ga), N-S, 500-km long, elongated orogenic domain in the central part of the São Francisco craton, Bahia state. Numerous syntectonic to post-tectonic peraluminous leucogranites were emplaced along the major structures of the belt. Their mineralogical and geochemical and some of their metallogenetic characteristics are very similar to their Hercynian and Himalayan equivalents. However, their average peraluminous index varies from one granitic pluton to another and biotite is, on average, slightly more magnesian in the Transamazonian leucogranites. Higher oxygen fugacity is indicated by the general occurrence of magnetite, the stability of allanite and sometimes epidote in most of the plutons and by biotite chemistry. The peraluminous magmatism of the Jacobina-Contendas Mirante belt results from crustal partial melting during a continental collision event at 2 Ga. Trace-element geochemistry implies variable source composition and/or melting conditions for the different granitic plutons and some different facies within the same plutonic unit. The scarcity of ilmenite, the general occurrence of magnetite, and the relatively low peraluminous index of some of these granites suggest that graphite-beating sediments are not a significantly source material. From their mineralogical and geochemical characteristics, acid meta-igneous rocks such as the Sete Voltas TTG suite of presumed Archaean age, seem to represent a suitable source for these granites. Sn, W, Li, F and Be enrichment of most Transamazonian leucogranites is much weaker than in the mineralized Variscan equivalents. The Caetano-Aliança and Riacho das Pedras granites represent the most specialized granitic bodies. Beryl (emerald), molybdenite and scheelite mineralizations are related to some of these granites which intrude ultrabasic formations: the Campo Formoso and the Carnaiba granites. In many of these granites, uranium content is comparable to values measured in mineralized Hercynian leucogranites. The occurrence of hexavalent uranium minerals, mineralization and episyenitic alteration are favourable criteria for finding Variscan-type uranium ore deposits.

Cuney, Michel; Sabaté, Pierre; Vidal, Philippe; Marinho, Moacyr M.; Conceiçao, Herbet

1990-12-01

255

Bioleaching of rare earth and radioactive elements from red mud using Penicillium tricolor RM-10.  

PubMed

The aim of this work is to investigate biological leaching of rare earth elements (REEs) and radioactive elements from red mud, and to evaluate the radioactivity of the bioleached red mud used for construction materials. A filamentous, acid-producing fungi named RM-10, identified as Penicillium tricolor, is isolated from red mud. In our bioleaching experiments by using RM-10, a total concentration of 2% (w/v) red mud under one-step bioleaching process was generally found to give the maximum leaching ratios of the REEs and radioactive elements. However, the highest extraction yields are achieved under two-step bioleaching process at 10% (w/v) pulp density. At pulp densities of 2% and 5% (w/v), red mud processed under both one- and two-step bioleaching can meet the radioactivity regulations in China. PMID:23548400

Qu, Yang; Lian, Bin

2013-05-01

256

Separation method and yields of small quantities of rare earth elements  

NASA Astrophysics Data System (ADS)

The EMIS PARSIFAL was designed to purify very small quantities of radioactive isotopes. Yields are therefore an important component of the separations. The ionization is done in a thermoionization source or a plasma source, according to the physical properties of the concerned elements. For rare earth elements (REE), hydroxides are electrodeposited on a tantalum wire; for thermoionization, the wire is introduced in a tungsten crucible whose depth is linked to the boiling point of the element. Samples weigh between 0.2 and 0.9 mg. The crucible, heated at 3050°C by electron bombardment, gives REE yields from 20 to 40% and usually 50% for europium. The total beam intensity is about 5 × 10 -6 A and separations last from 2 to 20 hours until the whole sample is consumed.

Boulin, Y.; Juery, A.

1992-08-01

257

Rare earth elements recycling from waste phosphor by dual hydrochloric acid dissolution.  

PubMed

This paper is a comparative study of recycling rare earth elements from waste phosphor, which focuses on the leaching rate and the technical principle. The traditional and dual dissolution by hydrochloric acid (DHA) methods were compared. The method of dual dissolution by hydrochloric acid has been developed. The Red rare earth phosphor (Y0.95Eu0.05)2O3 in waste phosphor is dissolved during the first step of acid leaching, while the Green phosphor (Ce0.67Tb0.33MgAl11O19) and the Blue phosphor (Ba0.9Eu0.1MgAl10O17) mixed with caustic soda are obtained by alkali sintering. The excess caustic soda and NaAlO2 are removed by washing. The insoluble matter is leached by the hydrochloric acid, followed by solvent extraction and precipitation (the DHA method). In comparison, the total leaching rate of the rare earth elements was 94.6% by DHA, which is much higher than 42.08% achieved by the traditional method. The leaching rate of Y, Eu, Ce and Tb reached 94.6%, 99.05%, 71.45%, and 76.22%, respectively. DHA can decrease the consumption of chemicals and energy. The suggested DHA method is feasible for industrial applications. PMID:24681591

Liu, Hu; Zhang, Shengen; Pan, Dean; Tian, Jianjun; Yang, Min; Wu, Maolin; Volinsky, Alex A

2014-05-15

258

Genesis of the Jinchuan PGE deposit, China: evidence from fluid inclusions, mineralogy and geochemistry of precious elements  

NASA Astrophysics Data System (ADS)

The Jinchuan deposit is a platinum group element (PGE)-rich sulfide deposit in China. Drilling and surface sampling show that three categories of platinum group element (PGE) mineralization occur; type I formed at magmatic temperatures, type II occurs in hydrothermally altered zones of the intrusion, and type III in sheared dunite and lherzolite. All ore types were analyzed for Os, Ir, Ru, Rh, Pd, Pt and Au, as well as for Cu, Ni, Co and S. Type I ore has (Pt + Pd)/(Os + Ir + Ru + Rh) ratios of <7 and relatively flat chondrite-normalized noble metal patterns; the platinum group minerals (PGM) are dominated by sperrylite and moncheite associated with chalcopyrite, pyrrhotite and pentlandite. Type II has (Pt + Pd)/(Os + Ir + Ru + Rh) ratios from 40 to 330 and noble metal distribution patterns with a positive slope; the most common PGM are sperrylite and Pd bismuthotelluride phases concentrated mostly at the margins of base metal sulfides. Type III ores have the highest (Pt + Pd)/(Os + Ir + Ru + Rh) ratios from 240 to 710; the most abundant PGM are sperrylite and phases of the Pt-Pd-Te-Bi-As-Cl system. It is concluded that the Jinchuan deposit formed as a result of primary magmatic crystallization followed by hydrothermal remobilization, transport, and deposition of the PGE.

Yang, X.-Z.; Ishihara, S.; Zhao, D.-H.

2006-01-01

259

Major and trace element geochemistry of Archean sulfidic black shale horizons as a potential vectoring tool for VMS exploration  

NASA Astrophysics Data System (ADS)

Metalliferous black shale horizons are a common but minor component of many subaqueous volcanic successions. These horizons are commonly drilled during volcanogenic massive sulfide (VMS) deposit exploration programs. Although ore metal enrichment can be identified by conventional assay methods, matrix dilution and post-burial hydrothermal and metamorphic activity may obscure information on the type and mechanism of metal addition to the shale. We used a combination of geochemical investigations at a variety of scales to discriminate between VMS-prospective and VMS-barren horizons. In addition, element signatures associated with hydrothermal plume fallout were identified and used and to determine relative direction to the palaeo-venting centre. Portable x-ray fluorescence (pXRF) analysers were used to identify and correlate prospective horizons within exploration drill cores. pXRF is a rapid and relatively inexpensive method of analysis that can deliver quantitative geochemical information at a cm-scale and help to identify intervals meriting further, more costly and time-consuming analyses. Subsequently, laser-ablation ICP-MS analysis of metal sulfides was used to constrain hydrothermal, hydrogenous and diagenetic end-member compositions, and to quantify element remobilization during post-burial alteration. These data were then used to refine the pXRF survey methodology and develop primary vectors toward potential concealed base metal deposits.

Chapman, J. B.; Peter, J. M.; Layton-Matthews, D.; Gemmell, J. B.

2009-05-01

260

Rare-earth elements in Egyptian granite by instrumental neutron activation analysis.  

PubMed

The mobilization of rare-earth elements (REEs) in the environment requires monitoring of these elements in environmental matrices, in which they are mainly present at trace levels. The similarity in REEs chemical behavior makes the separate determination of each element by chemical methods difficult; instrumental neutron activation analysis (INAA), based on nuclear properties of the elements to be determined, is a method of choice in trace analysis of REEs and related elements. Therefore, INAA was applied as a sensitive nondestructive analytical tool for the determination of REEs to find out what information could be obtained about the REEs of some Egyptian granite collected from four locations in Aswan area in south Egypt as follows wadi El-Allaqi, El-Shelal, Gabel Ibrahim Pasha and from Sehyel Island and to estimate the accuracy, reproducibility and detection limit of NAA method in case of the given samples. The samples were properly prepared together with standards and simultaneously irradiated in a neutron flux of 7 x 10(11)n/cm(2)s in the TRIGA Mainz research reactor facilities. The following elements have been determined: La, Ce, Nd, Sm, Eu, Yb and Lu. The gamma spectra was collected by HPGe detector and the analysis was done by means of computerized multichannel analyzer. The X-ray fluorescence (XRF) was also used. PMID:17208446

El-Taher, A

2007-04-01

261

Trace Element Partitioning Between Earths Lower Mantle Minerals and Iron Alloy Melts  

NASA Astrophysics Data System (ADS)

The physical conditions (pressure-temperature-oxygen fugacity) and iron alloy compositions involved in the formation of Earths core are relatively poorly constrained. Current geochemical core formation models rely heavily on arguments related to how trace elements are distributed between metal and silicate during metal segregation. Hypotheses concerning the timing of Earths accretion and core segregation also require knowledge of metal-silicate partition coefficients for parent and daughter isotopes in key isotopic systems (e.g., W-Hf, U-Pb). Many studies (e.g., Righter, Ann Rev Earth Planet Sci 2003) have focused on metal melt - silicate melt partitioning at upper mantle and transition zone pressures (P < 25 GPa) and high temperatures. In contrast, little is known about the partitioning of trace elements between metals and lower mantle minerals and melts, even though the later stages of core formation, characterised by high-energy processes related to collisions of Mars-sized objects, likely involved liquid iron alloys percolating through a solid or molten lower mantle matrix. We will present results of a systematic study of the distribution of trace elements between lower mantle minerals (Ca and Mg perovskite, and ferropericlase) and a range of iron alloy melts, to assess the redistribution of trace elements as metallic melts percolate through the lower mantle. Experiments are performed using a 10/3.5 assembly in a conventional Walker-type multi-anvil press (P < 26 GPa), and using a 7/2 assembly in a spherically-constrained multi-anvil press with sintered diamond pressure-transmitting cubes (P > 30 GPa). Starting materials include end-member silicates (wollastonite, enstatite), MgO, and Fe-light element (S, Si) mixtures. Trace elements added include slightly siderophile (Mn, V, Cr), moderately siderophile (P, W, Co, Ni, Mo) and highly siderophile elements, as well as key parent-daughter pairs, and run products are analysed by laser ablation ICP-MS. Implications of our data for core formation models will be discussed.

van Westrenen, W.; Schmidt, M.; Günther, D.; Stewart, A.

2004-12-01

262

Late Holocene Multiproxy Record (Palynology, Stable Isotope and Multi-Element Geochemistry) of Lake Santa Maria del Oro, Western Mesoamerica.  

NASA Astrophysics Data System (ADS)

We present the palynological, stable isotope and major element (ITRAX X-Ray fluorescence) data from a 850-cm sediment sequence from the deepest part of lake Santa María del Oro (SMO) in order to document changes in the climatic and limnological conditions and in the vegetation for the last ca. 5000 yr. SMO is a crater lake of (750 m asl, 2 km diam.) located in a tropical sub-humid climate (1250 mm/yr, average annual temperature 21° C) at the transition between the temperate central Mexican highlands and the arid northern regions. Tropical deciduous forests which loose their leaves for 8 months in a year and the tropical oak forests are the main plant communities in the lake catchments. The western part of Mesoamerica is the cradle of maize (Zea mays ssp. mays ) agriculture; this region is probably one of the two centers of maize domestication based on the presence of one of its closets wild relative teosinte (Zea mays ssp. parviglumis ). Chronology was established with 8 AMS radiocarbon dates. Sediments are finely laminated, with some intervals dominated by black and brown clayey silt and others by brown clayey silt and calcareous silt. In some levels, laminae are characterized by silts and fine sands. Authigenic carbonate laminations are formed during the summer season, when the highest temperatures are reached in the area. Throughout the pollen analysis, teosinte pollen and maize pollen was recorded. The major element concentration (Ca and Ti) in the bulk sediments was analyzed by ITRAX multi-element scanner and the isotopic data (?13C and ?18O) in authigenic carbonates by mass spectrometer. Ca and Ti ITRAX intensities were calibrated to mass % by using the linear relationship between ITRAX intensity and mass % obtained through conventional XRF analysis. Preliminary pollen data of SMO sediments indicates abundant pollen of teosinte from ca. 2000 to 100 BC and maize presence at ca. 1300 BC and ca. 900 BC along with high charcoal particle concentrations, suggesting early agricultural activity in the area, being the first record of maize in the western region of Mesoamerica. The phases with higher concentration of Ti are identified as periods of higher inflow into the lake basin (BC 1700-1400, 0- AD 200, AD 900 and AD 1800-1900). Phases of higher evaporative conditions are identify at ca. BC 700, BC 400, AD 400-800 and AD 1900-2003 based on Ca high values and enriched ?18O and ?13C. There exists a negative relationship between Ca and Ti. Evidence of changes in climatic conditions is inferred from the data.

Lozano, S.; Caballero, M.; Rodriguez, A.; Roy, P.; Sosa, S.

2007-05-01

263

Experimental Simulations of Core Formation at High Pressure and Temperature: Constraints on Candidate Light Elements in the Earth's Core  

Microsoft Academic Search

Although a number of candidate light elements have been suggested to alloy with Fe in the Earth's core, there is no general consensus on which is the most predominant, due to the lack of knowledge about this portion of the Earth. We have carried out experimental simulations on possible core formation processes by examining the behavior of iron in the

T. Uchida; Y. Wang; M. L. Rivers; S. R. Sutton

2002-01-01

264

Selective liquid chromatographic separation of yttrium from heavier rare earth elements using acetic acid as a novel eluent.  

PubMed

One of the major difficulties in the rare earth elements separation is purification of yttrium from heavy rare earth elements. Thus, an HPLC method using acetic acid as novel eluent was explored for selective separation of yttrium form the heavy rare earth elements. When acetic acid is used as a mobile phase yttrium eluted with the lighter lanthanides. This is contrary to its relative position amongst heavier lanthanides when eluents commonly used for separation of rare earth elements were employed. The shift in elution position of yttrium with acetic acid as eluent may reflect a relatively lower stability constant of the yttrium-AcOH complex (in the same order as for the lighter lanthanides) compared to the corresponding AcOH complexes with heavy lanthanides, enabling selective separation of yttrium from the latter. The method was successfully used for selective separation of yttrium in mixed rare earth sample containing about 80% of yttrium and about 20% of heavy rare earth oxides. Thus, the use of AcOH as eluent is an effective approach for separating and determining the trace amounts of heavy rare earth elements in large amounts of yttrium matrix. Separation was performed on C18 column by running appropriate elution programs. The effluent from the column was monitored with diode array detector at absorbance wavelength of 658nm after post column derivatization with Arsenazo III. PMID:23932372

Kifle, Dejene; Wibetoe, Grethe

2013-09-13

265

Comparison of the partitioning behaviours of yttrium, rare earth elements, and titanium between hydrogenetic marine ferromanganese crusts and seawater  

Microsoft Academic Search

In order to evaluate details of the partitioning behaviours of Y, rare earth elements (REEs), and Ti between inorganic metal oxide surfaces and seawater, we studied the distribution of these elements in hydrogenetic marine ferromanganese (Fe-Mn) crusts from the Central Pacific Ocean. Nonphosphatized Fe-Mn crusts display shale-normalized rare earths and yttrium (REYSN) patterns (Y inserted between Dy and Ho) that

Michael Bau; Andrea Koschinsky; Peter Dulski; James R. Hein

1996-01-01

266

Determination of rare earth elements and thorium in britholite ore by energy dispersive X-ray fluorescence spectrometry  

Microsoft Academic Search

A radioisotope-excited X-ray fluorescence technique is applied for the determination of thorium and rare earth elements in britholite ore from Canada. An annular source of57Co is employed for excitation of characteristic K X-rays of thorium and rare earth elements. The peak ratios of lanthanides were used to remove the difficulties because of overlapping lines at the 33–50 keV energy region.

N. Efe; S. Akman; P. Arikan

1987-01-01

267

Thermo-tectonic history of Variscan post-collisional plutons from the Danubian domain (Romanian Southern Carpathians) as recorded by zircon trace element geochemistry and thermometry  

NASA Astrophysics Data System (ADS)

The Romanian Southern Carpathians show a complicated nappe structure completed during the Alpine orogeny (mid to late Cretaceous), with the Danubian domain (a collection of Neoproterozoic granitoids and metamorphic rocks, Paleozoic metasediment and Mesozoic sediments) situated in the lowermost tectonostratigraphic position, topped by the Severin nappe system (Jurassic ophiolites and associated rocks), and Getic-Supragetic nappe system (pre-Alpine gneisses and sediments), the uppermost unit in the Alpine stack. During the latest stages of the Variscan orogeny, the Neoproterozoic basement of the Danubian domain was intruded by numerous granitoid plutons, preserving ages that indicate important post-collisional magmatic activity. Ten statistically representative zircon populations from ten different Variscan plutons were studied by means of electron probe micro-analyzer (EPMA) and laser ablation inductively coupled plasma-mass spectrometry (LA ICP-MS). Cathodoluminescence imaging revealed that the majority of the samples are extensively zoned and have strong inheritance. While both cores and rims were analyzed, a clear distinction has been made between them in the graphical representation and interpretation of data. There is a visible positive correlation between the total trace elemental compositions of the zircons and their ages. Furthermore, ?REE (ranging between 212 and 2796ppm) is fairly well correlated with temperatures (545 to 755°C) calculated using the Ti-in-zircon thermometer. However, there is a wide variation in zircon trace elemental composition (e.g., HREE, Sm, Nd, Sr, Hf, Th/U) between the individual plutons, and sometimes within the same pluton. In-pluton variability is frequently correlated with variations in the whole rock geochemistry and petrology with the intrusions. Such variations can be attributed to melting of heterogeneous protoliths (both crust- and mantle-derived) or to variations of the physical parameters (e.g., temperature and pressure,) during melting, which may be linked to a change in the tectonic regimes during orogenic events, such as transition from crust thickening to delamination. Considering the relatively narrow age window, and the zircons' geochemical heterogeneity, it may be inferred that latest stages of the Variscan magmatism in the Danubian domain was characterized by abrupt changes in the geodynamic setting that could imply intrusion of mantle-derived magmas as a result of crust and mantle decoupling

Stremtan, C.; Ryan, J.; Balintoni, I.; Balica, C.

2012-04-01

268

JGR special section: Gas Geochemistry  

NASA Astrophysics Data System (ADS)

The Journal of Geophysical Research-Solid Earth and Planets will devote a special section of an issue to regularly reviewed papers on the gas geochemistry of volca-nism, earthquakes, resource exploration, and the earth's interior. Interested authors are invited to submit three copies of each manuscript by July 1, 1985, to Gerald Schubert, Editor, Journal of Geophysical Research—Solid Earth and Planets, Department of Earth and Space Sciences, University of California, Los Angeles, CA 90024, and one copy to the guest associate editor for the special section, Chi-Yu King, U.S. Geological Survey, 345 Middle-field Rd., MS/977, Menlo Park, CA 94025 (telephone: 415-323-8111, ext. 2706 or FTS 467-2706). King should also be informed of the title of each paper by May 1, 1985.

269

Transition region of the earth's upper mantle  

NASA Technical Reports Server (NTRS)

The chemistry of the earth's mantle is discussed using data from cosmochemistry, geochemistry, petrology, seismology, and mineral physics. The chondritic earth, the upper mantle and the 400-km discontinuity, the transition region, lower mantle mineralogy, and surface wave tomography are examined. Three main issues are addressed: (1) whether the mantle is homogeneous in composition or chemically stratified, (2) whether the major element chemistry of the mantle is more similar to upper mantle peridotites or to chondrites, and (3) the nature of the composition of the source region of basalts erupted at midocean ridges.

Anderson, D. L.; Bass, J. D.

1986-01-01

270

Comments on "Geochemistry, petrogenesis and tectonic setting of the Samothraki mafic suite, NE Greece: Trace-element, isotopic and zircon age constraints" by Nikola Koglin, Dimitrios Kostopoulos and Thomas Reischmann, Tectonophysics 473 (2009), 53-68  

NASA Astrophysics Data System (ADS)

The manuscript "Geochemistry, petrogenesis and tectonic setting of the Samothraki mafic suite, NE Greece: Trace-element, isotopic and zircon age constraints" presented by Koglin et al. (2009a) tries to re-interpret the Samothraki ophiolite as a non ophiolitic mafic suite, which has been generated in a propagated fore-arc rift setting. However, incomplete sampling by the authors and overinterpretation of the few data are suspicious. The geochemical and petrological similarity of the Samothraki mafic sequence with other well-known ophiolites is not acknowledged and the proposed geotectonic regime is unrealistic.

Tsikouras, Basilios; Hatzipanagiotou, Konstantin

2010-03-01

271

Using mineral trace element geochemistry to track magma processes in a "big tank" magma chamber: a laser ablation ICP-MS study of hornblende and augite  

NASA Astrophysics Data System (ADS)

Processes in magma chambers have been the subject of many discussions. Incremental emplacement models, supported by U-Pb zircon geochronology, preclude mixing, fractional crystallization and assimilation as chamber-wide processes. However, low-velocity seismic anomalies interpreted as partially molten areas in the crust, voluminous dacitic ignimbrites, and field evidence for crystal accumulation argue for large volumes of crystal-rich mush in the crust. In this study we use the trace element composition of liquidus phases augite and hornblende in the Wooley Creek batholith (WCb), Klamath Mountains, northern California, to reconstruct the geochemical history of the batholith. The WCb is a tilted pluton emplaced between 160 and 155 Ma. The lower WCb ranges from 2-pyroxene gabbro to hornblende tonalite. Variations in the texture and the proportions of hornblende and pyroxene suggest that the lower part was emplaced as several magma batches that reached hornblende stability at different temperatures and times. Augite crystals are normally zoned, with variable Cr (200-3000 ppm) and Ti (1000-4000 ppm) concentrations. Eu anomalies get progressively larger toward the rims, suggesting an evolution of individual melt batches by simple fractional crystallization. The central part of the pluton is mainly hornblende biotite quartz-diorite. Mafic enclaves and syn-plutonic dikes are abundant. Pyroxenes is rarely preserved in that part of the pluton. The upper WCb ranges from hornblende biotite quartz diorite to hornblende biotite granite. Bulk rock major element geochemical trends are consistent with upward differentiation of a single, unified magma batch. This interpretation is supported by homogenous trace element compositions of hornblende throughout the upper part of the pluton. Dacitic roof dikes contain hornblende phenocrysts identical to those in the upper WCb, indicating that the mush present in the upper WCb was eruptible. Two-pyroxene andesitic roof dikes are common and were interpreted as originating from the lower WCb. Oscillatory trace element zoning of augite plus low Cr (<1000 ppm) and high Ti (>3000 ppm) concentrations suggest that the dikes were derived from the central WCb, where evidence of replenishment and mingling is widespread. Thus, the lower and central parts of the pluton were emplaced as multiple, distinct magma batches. In contrast, the upper part of the pluton can be explained as (1)several batches of internally homogeneous magma emplaced at different times, with successively more evolved magma emplaced toward the top, or (2) evolution from a single large magma volume ('big tank') that could have been emplaced incrementally or as one batch. Existence of an upper 'big tank' is consistent with the lack of internal contacts, the presence of coherent geochemical trends and the presence of dacitic roof dikes compositionally identical to the upper part of the WCb. This study shows that mineral trace element geochemistry is a powerful tool in deciphering the size and evolution of magma batches within crystallized plutons.

Coint, N.; Barnes, C. G.; Barnes, M. A.; Yoshinobu, A. S.

2011-12-01

272

A compilation of whole-rock and glass major-element geochemistry of Kilauea Volcano, Hawai'i, near-vent eruptive products: January 1983 through September 2001  

USGS Publications Warehouse

This report presents major-element geochemical data from 652 glasses (~6,520 analyses) and 795 whole-rock aliquots from 1,002 fresh samples of olivine-tholeiitic lava collected throughout the near-continuous eruption of Kïlauea Volcano, Hawai'i, from January 1983 through September 2001. The data presented herein provide a unique temporal compilation of lava geochemistry that best reflects variations of pre-eruptive magma compositions during prolonged rift-zone eruption. This document serves as a repository for geochemical data referred to in U.S. Geological Survey Professional Paper 1676 (Heliker, Swanson, and Takahashi, eds., 2003) which includes multidisciplinary research papers pertaining to the first twenty years of Puu Oo-Kupaianaha eruption activity. Details of eruption characteristics and nomenclature are provided in the introductory chapter of that volume (Heliker and Mattox, 2003). Geochemical relations among all or portions of this data set are depicted and interpreted by Thornber (2003), Thornber and others (2003) and Thornber (2001). Trace element compositions and Nd, Sr and Pb isotopic analyses of representative samples of this select eruption suite will be provided in a separate and complimentary open file report. From 1983 to October 2001, approximately 2,500 eruption samples were collected and archived by the U.S. Geological Survey’s Hawaiian Volcano Observatory (HVO). Geochemical data for 1,002 of these samples are included here. Previous reports present bulk-lava major- element chemistry for eruption samples collected from 1983 to 1986 and from 1990 to 1994 (Neal and others, 1988 and Mangan and others, 1995, respectively). Major element glass chemistry and thermometry data for samples collected from 1983 to 1994 is reported by Helz and Hearn (1998) and whole-rock and glass chemistry for samples collected from September 1994 to October 2001 is provided by Thornber and others (2002). This report is a compilation of previously published data along with unpublished whole-rock data for the 1986–1990 eruptive interval (episode 48, see Heliker and Mattox, 2003). The geochemical data in this report is mostly limited to well-quenched samples collected at or near their respective vents. The samples include tephra and spatter, in addition to lava dipped from lava lakes, lava tubes, and surface lava flows. The details of sample collection techniques as described by Thornber and others (2002) are generally applicable for this entire sampling interval. Specifically excluded from this database are samples of distal surface flows, many of which were collected for topical studies of emplacement dynamics (for example, Cashman and others, 1999). Samples of sluggish or crystal-laden tube flows collected during eruptive pauses were also excluded, because they bear visual, petrographic and geochemical evidence for crystal accumulation during surface-flow stagnation. In addition, the pre-1992 whole-rock major element data reported here has been corrected to compensate for minor analytical discrepancies between pre- and post-1991 XRF analyses. These discrepancies resulted from a change in instrumentation at the USGS Denver analytical laboratories. This select suite of time-constrained geochemical data is suitable for constructing petrologic models of pre-eruptive magmatic processes associated with prolong rift zone eruption of Hawaiian shield volcanoes.

Thornber, Carl R.; Hon, Ken; Heliker, Christina; Sherrod, David A.

2003-01-01

273

Mineralogy, major and trace element geochemistry of riverbed sediments in the headwaters of the Yangtze, Tongtian River and Jinsha River  

NASA Astrophysics Data System (ADS)

We collected riverbed sediments of the headwaters of the Yangtze River (Chumaer River, Tuotuo River, Gaerqu River and Buqu River), Tongtian River and Jinsha River (HTJR) flowing on the eastern Tibetan Plateau and analyzed their mineralogical features, major and trace element contents. The results show: (i) very poor correlations of Na 2O, K 2O, CaO, Ba, and Sr to SiO 2, LREE to Th, HREE to Hf, and Ta/La to Ti, and characteristics of Eu anomaly (the ratios of (Eu/Eu *) N range from 0.60 to 0.83 with an average value of 0.71) all indicate that the Jinsha River sediments have not undergone much mineralogical sorting; (ii) illite and chlorite are predominant clay minerals, and quartz, calcite, dolomite, albite, and K-feldspar are prevailing non-clay minerals. The characteristics of mineral assemblage indicate relatively weak chemical weathering degree in these river basins; (iii) very high contents of Fe 2O 3, MgO, TiO 2, Sc, V, Cr, Co, and Ni at Panzhihua mainly result from the huge-sized V-Ti magnetite deposits occurred in layered gabbroic intrusion; and (iv) the chemical alteration index (CIA) in the HTJR ranges from 46.5 to 69.2 and with an average value of 60.5 which indicates relatively weak weathering degree.

Wu, Weihua; Xu, Shijun; Lu, Huayu; Yang, Jiedong; Yin, Hongwei; Liu, Wen

2011-01-01

274

Systematics of metal-silicate partitioning for many siderophile elements applied to Earth’s core formation  

NASA Astrophysics Data System (ADS)

Superliquidus metal-silicate partitioning was investigated for a number of moderately siderophile (Mo, As, Ge, W, P, Ni, Co), slightly siderophile (Zn, Ga, Mn, V, Cr) and refractory lithophile (Nb, Ta) elements. To provide independent constrains on the effects of temperature, oxygen fugacity and silicate melt composition, isobaric (3 GPa) experiments were conducted in piston cylinder apparatus at temperature between 1600 and 2600 °C, relative oxygen fugacities of IW-1.5 to IW-3.5, and for silicate melt compositions ranging from basalt to peridotite. The effect of pressure was investigated through a combination of piston cylinder and multi-anvil isothermal experiments between 0.5 and 18 GPa at 1900 °C. Oxidation states of siderophile elements in the silicate melt as well as effect of carbon saturation on partitioning are also derived from these results. For some elements (e.g. Ga, Ge, W, V, Zn) the observed temperature dependence does not define trends parallel to those modeled using metal-metal oxide free energy data. We correct partitioning data for solute interactions in the metallic liquid and provide a parameterization utilized in extrapolating these results to the P- T- X conditions proposed by various core formation models. A single-stage core formation model reproduces the mantle abundances of several siderophile elements (Ni, Co, Cr, Mn, Mo, W, Zn) for core-mantle equilibration at pressures from 32 to 42 GPa along the solidus of a deep peridotitic magma ocean (˜3000 K for this pressure range) and oxygen fugacities relevant to the FeO content of the present-day mantle. However, these P- T- fO 2 conditions cannot produce the observed concentrations of Ga, Ge, V, Nb, As and P. For more reducing conditions, the P- T solution domain for single stage core formation occurs at subsolidus conditions and still cannot account for the abundances of Ge, Nb and P. Continuous core formation at the base of a magma ocean at P- T conditions constrained by the peridotite liquidus and fixed fO 2 yields concentrations matching observed values for Ni, Co, Cr, Zn, Mn and W but underestimates the core/mantle partitioning observed for other elements, notably V, which can be reconciled if accretion began under reducing conditions with progressive oxidation to fO 2 conditions consistent with the current concentration of FeO in the mantle as proposed by Wade and Wood (2005). However, neither oxygen fugacity path is capable of accounting for the depletions of Ga and Ge in the Earth's mantle. To better understand core formation, we need further tests integrating the currently poorly-known effects of light elements and more complex conditions of accretion and differentiation such as giant impacts and incomplete equilibration.

Siebert, Julien; Corgne, Alexandre; Ryerson, Frederick J.

2011-03-01

275

Geochemistry of U and Th and its Influence on the Origin and Evolution of the Crust of Earth and the Biological Evolution  

Microsoft Academic Search

We have investigated the migration behaviors of uranium (U) and thorium (Th) in Earth and other terrestrial planets. Theoretical models of U and Th migration have been proposed. These models suggest that the unique features of Earth are closely connected with its unique U and Th migration models and distribution patterns. In the Earth, U and Th can combine with

Xuezhao Bao; Ali Zhang

2007-01-01

276

Geochemistry of U and Th and its Influence on the Origin and Evolution of the Earth's Crust and the Biological Evolution  

Microsoft Academic Search

We have investigated the migration behaviors of uranium (U) and thorium (Th) in Earth and other terrestrial planets. Theoretical models of U and Th migration have been proposed. These models suggest that the unique features of Earth are closely connected with its unique U and Th migration models and distribution patterns. In the Earth, U and Th can combine with

Xuezhao Baoa; Ali Zhang

277

Rare-Earth Elements in Lighting and Optical Applications and Their Recycling  

NASA Astrophysics Data System (ADS)

Rare-earth elements (REEs) are used in lighting and optical applications to enable color and light adjustment, miniaturization, and energy efficiency. Common applications of REEs include phosphors for light-emitting diodes, lasers, and electronic video displays. This article reviews how REEs are widely used in these applications. However, supply constraints, including rising prices, environmental concerns over mining and refining processes, and China's control over the supply of the vast majority of REEs, are of concern for manufacturers. In view of these supply constraints, this article discusses ways for manufacturers of lighting and optical devices to identify potential substitutes and recycling methods for REEs.

Song, Xin; Chang, Moon-Hwan; Pecht, Michael

2013-10-01

278

Rare-earth elemental analysis of banded iron-formations by instrumental neutron activation analysis  

Microsoft Academic Search

Representative banded iron-formations (BIFs) from various locations of the eastern Indian geological belt were investigated\\u000a by instrumental neutron activation analysis (INAA). After pre-concentration, irradiation was carried out using a neutron flux\\u000a of 5.1·1016 m?2·s?1, 1.0·1015 m?2·s?1 and 3.7·1015 m?2s?1, with thermal, epi-thermal and fast neutrons, respectively. The activities in these samples were measured by a HPGe detector.\\u000a Ten rare-earth elements,

P. K. Nayak; B. Wierczinski; S. Lahiri

2008-01-01

279

The mobility of rare-earth elements during hydrothermal activity: A review  

Microsoft Academic Search

The mobility of the rare-earth elements (REE) during hydrothermal activities is increasingly documented. Geological and experimental\\u000a evidence suggests that REE may be mobile in solutions rich in F-, Cl-, HCO3\\u000a -, CO3\\u000a 2-, HPO4\\u000a 2-, PO4\\u000a 3-, or in combinations of the above ligands, even though little has been known about which ligand or which combination is most\\u000a effective in

Xiong Yongliang; Zhai Yusheng

1991-01-01

280

Effect of rare earth element additions on the impression creep of Sn–9Zn solder alloy  

Microsoft Academic Search

Creep behavior of the Sn–9Zn–RE alloys containing 0.1, 0.25 and 0.5 wt.% rare earth (RE) elements was studied by impression\\u000a testing and compared to that of the eutectic Sn–9Zn alloy. The tests were carried out under constant punching stress in the\\u000a range 40–135 MPa and at temperatures in the range 298–420 K. Results showed that for all loads and temperatures, Sn–9Zn–0.25RE\\u000a had the

R. Mahmudi; A. R. Geranmayeh; B. Zahiri; M. H. Marvasti

2010-01-01

281

Concentration levels of rare-earth elements and thorium in plants from the Morro do Ferro environment as an indicator for the biological availability of transuranium elements  

Microsoft Academic Search

Plants and soils from a natural thorium and rare-earth element occurrence (Morro do Ferro, Brazil) were analyzed by alpha spectrometry (Th) and ICP-AES (REE), after pre-concentration of the elements by solvent extraction, co-precipitation and ion exchange procedures. Leaching experiments with humic acid solutions and different soils were performed to estimate the fraction of elements biologically available. High concentrations of the

N. Miekeley; E. A. Casartelli; R. M. Dotto

1994-01-01

282

Earth Science Information System (ESIS)  

USGS Publications Warehouse

The Earth Science Information System (ESIS) was developed in 1981 by the U.S. Geological Survey's Office of the Data Administrator. ESIS serves as a comprehensive data management facility designed to support the coordination, integration, and standardization of scientific, technical, and bibliographic data of the U.S. Geological Survey (USGS). ESIS provides, through an online interactive computer system, referral to information about USGS data bases, data elements which are fields in the records of data bases, and systems. The data bases contain information about many subjects from several scientific disciplines such as: geology, geophysics, geochemistry, hydrology, cartography, oceanography, geography, minerals exploration and conservation, and satellite data sensing.

U.S. Geological Survey

1982-01-01

283

Metasomatic- hydrothermal processes in the Qatruyeh area, Iran: Mineralogy and trace elements geochemistry of metasedimentary rock- hosted iron indices  

NASA Astrophysics Data System (ADS)

The Qatruyeh iron indices are located at about 40 Km northeast of Neyriz, in the eastern edge of the HP-LT Sanandaj-Sirjan metamorphic belt, Zagros Mountain. Qatruyeh indices are contained within the metasedimentary rocks of the Late Proterozoic- early Paleozoic, which consists predominantly of dolomitic limestone, greenschist and quartzite. Field investigations, mineralogical studies and XRD analyses indicate that orebodies are dominated by magnetite. The structures of orebodies are mainly formed as thin layers and massive, which are located between dolomitic limestones and greenschists. Tourmaline, muscovite, chlorite, talc, martite, specularite, goethite, limonite, pyrite and chalcopyrite are present as minor minerals. The area has experienced two different stages of metasomatic- hydrothermal alterations. The iron ores were formed during the metasomatic- hydrothermal processes. Those processes are: (1) Na-Ca alteration and (2) mineralization (Oxidation-Sulfidation). The first stage of alteration follows the attainment of peak regional metamorphic condition (187± 2.6 Ma based on zircon SHRIMP U- Pb). This alteration is accompanied with Low-grade magnetite ores formation (50 % Fe2O3t), replacement textures, gradual transformation between layered ores and host rock. Wet chemistry analyses on magnetite shows that Na-Ca alteration caused increasing Cr and Cu as transition metals and Ni, Co and V were depleted. Metasedimentary rock-hosted iron deposits indicate that Na-Ca alteration increase Cu, Ni, Cr, Co, Zn as immobile elements and Na-Fe, whereas the LILE (Pb, Sr) were depleted. The formation of paragonite-tourmaline is also occurs as a part of iron deposition process in the stage. The second stage of metasomatic- hydrothermal alteration is accompanied with widespread veins and veinlets of High-grade magnetite (75 % Fe2O3t) - hematite- Quartz. Mineralization took place along host rock fractures with passage of saline, hot and oxidized aqueous fluids. Paragonite altered to muscovite in the host-rocks and ores in the stage. Sulfide replacement is generally occurred as a late stage phase.

Rajabzadeh, M. A.; Asadi, S.

2009-04-01

284

The light element component of the Earth’s core: Constraints from in situ X-Radiography in the LHDAC  

NASA Astrophysics Data System (ADS)

The light element budget of the Earth’s core depends in part on the high-pressure melting relations of the relevant iron rich binary systems. Candidate alloying elements include H, C, O, Si and S, due to their cosmochemical abundance. Many of these systems are known to contain eutectic points, the temperatures and compositions of which are critical to reconstructing the phase relations of these systems. Thus far most studies reporting the composition of eutectic liquids depend on ex situ analysis with a potential for systematic errors introduced by quench induced exsolution. To circumvent this issue we have developed an in situ technique for the determination of liquid compositions in iron-rich binary systems at simultaneous high-pressure and high-temperature conditions. Samples consist of Fe(1-x)O or FeS, surrounded by a ring of iron forming a ‘donut’ with a diameter of ~100?m and a thickness of ~20?m. Pressure is monitored by ruby fluorescence. The sample is heated at the boundary between the iron and light element compound using two 100 W IR lasers in a double-sided configuration at beamline 12.2.2 at the Advanced Light Source. Temperature is measured by spectroradiometry. Before, during and after melting, X-radiographic images of the sample are taken by shining a defocused beam of synchrotron X-rays through the sample and onto a CdWO4 phosphor. The visible light from the phosphor is then focused onto a high resolution CCD, where absorption contrast images are recorded. The absorption of the molten region is then determined, and it’s composition calculated by comparison to the absorption of the two solid end members. In previous work we measured the composition of the Fe-FeS eutectic to 20 GPa and the Fe-Fe3C eutectic to 44 GPa [1,2]. Further, we saw no discernible solubility of oxygen in liquid iron up to 43 GPa [1]. Here we extend the data for sulfur up to 70 GPa and for oxygen up to 63 GPa. Our new sulfur data fit well with previous studies at lower pressure, and suggest that the sulfur content of the eutectic is tending to ~15wt% with increasing pressure. In the Fe-FeO system, upon reaching the Fe-FeO eutectic temperature (indicated by a plateau in the power-temperature function), no evidence of a melt was seen within the absorption contrast images. Only when the temperature was raised above this first plateau to a second plateau, representing the melting point of FeO did a ‘ledge’ appear in the absorption contrast image, suggesting the presence of a liquid with a composition intermediate between Fe and FeO. Further, the composition of this ledge was pressure insensitive, and close to a 50:50 mix of Fe and FeO. We interpret these results as the formation of a eutectic melt with an oxygen content below the detection limit (~1 wt%), followed by melting of the FeO end-member and the subsequent mixing of the two liquid phases. These results suggest that the solubility of oxygen remains below ~1wt% beyond 60 GPa, in contradiction with several recent studies [3]. [1] Walker, D., et al. Chem Geol., 2008. [2] Lord, O. T., et al. EPSL, 2009. [3] Seagle, C. T., et al. EPSL, 2008.

Lord, O. T.; Walter, M. J.; Walker, D.; Clark, S. M.

2009-12-01

285

Thickening and propagation of the Pamir plateau: insights from monazite and titanite geochronology and trace-element geochemistry, eastern Tajikistan  

NASA Astrophysics Data System (ADS)

The Pamir plateau contains extensive exposures of mid-lower crust, depths not widely exposed in the Tibetan plateau. Determining the spatial and temporal patterns of crustal thickening of the Pamir plateau is critical for understanding how orogenic plateaux are constructed and propagate. The Pamir dome cores consist of upper-amphibolite facies para- and orthogneisses and schists, with the characteristic peak mineral assemblage of kyanite + biotite + garnet ± muscovite in pelites. Thermobarometry indicates peak metamorphism at 600-750°C and 6-10 kbar, representing exhumation depths of 20-35 km (McGraw et al., in review). U-Th-Pb ages of monazite and titanite from the Pamir domes were determined to investigate the timing of thickening and cooling of the mid to lower crust. The closure temperatures of monazite (?700 °C) and titanite (~650-700 °C) make them especially useful geochronometers for dating high-grade metamorphism. Additionally, maps of yttrium (Y) in monazite and garnet and Zr-in-titanite thermometry allow more robust interpretations of isotopic age information. Ages were obtained using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) following the acquisition of backscattered electron and x-ray element maps to characterize grain zoning and guide LA-ICP-MS spot placement. The monazites in the rock matrix and as garnet inclusions are chiefly Cenozoic and range from 30 to 18 Ma. They record crystallization during prograde and peak metamorphism, based on textures and compositions. The dated titanites are exclusively polycrystalline aggregates recrystallized during metamorphism. They range from 40 to 10 Ma and define two populations of ~40-32 Ma and ~19-10 Ma. The older titanite ages are restricted to the central Pamir where metamorphic temperatures were <650°C, and the youngest ages come from the southern Pamir, where metamorphic temperatures were above titanite closure to Pb. The oldest ages are therefore likely prograde, and the youngest likely reflect closure during exhumation. The spatial patterns of monazite and titanite ages are consistent with westward thickening and southward exhumation. Westward thickening might have been caused by flow from the topographically higher Tibetan plateau, whereas exhumation may have been controlled by the initiation of intracontinental subduction.

Stearns, M. A.; Hacker, B. R.; Kylander-Clark, A. R.; Ratschbacher, L.; Seward, G.

2011-12-01

286

Behavior of rare earth and trace elements in Lake Tanganyika and its three major tributaries  

NASA Astrophysics Data System (ADS)

Water samples were collected, during the rainy and dry seasons 2003, from three major rivers and several locations of the Lake Tanganyika. They were directly filtered (0.45 im pore size) into pre-washed polyethylene bottles, and acidified at pH 2. Finnigan Element 2 high resolution (HR)-IC-MPS was used to measure trace and rare earth elements (REE) concentrations under clean laboratory conditions, and (115In) was used as an internal standard. Because of the close relationship between light rare earth element (LREE) and Fe, riverine REE of the three were used to study the process trace element scavenging by Fe oxyhydroxides in three different two sub-basins of the lake. This confirmed by the significant positive correlation between Nd and Fe. The vertical distribution of Fe and Mn oxides were also used to investigate removal and release of trace elements in the water column. The normalized lacustrine REE to their riverine counterpart showed a gradual removal of REE across the lake, which was in the order of LREE>MREE>HREE. Hence, the rivers are the sole source of the lacustrine REE abundance. Coincidence of Fe maxima with those of Ce anomalies and La indicates that trace element profiles are chiefly controlled by the coating of Fe oxyhydroxides through oxidation of Fe2+ to Fe3+ under high dissolved oxygen contents and pH and vice versa. Due to differences in hydrodynamics between the extreme ends of the lake (upwelling in the southern end during the dry season), high mixing between bottom water and surface was observed at the surface in the Southern Basin while the mixing occurred mainly between 40 m and 80 m depth in the Northern Basin. There was also a clear similarity between Ba and NO3- and PO43- profiles in the southern end of the lake, supporting the idea that deep anoxic water, rich in nutrients and trace elements, are bought the surface during this period of intensive upwelling. In conclusion, the surface water chemical compositions of Lake Tanganyika are controlled by fluvial inputs and the seasonal changes in hydrodynamics across the lake.

Sako, A.; Johnson, R.

2004-12-01

287

Geochemistry, petrogenesis and tectonic setting of the Samothraki mafic suite, NE Greece: Trace-element, isotopic and zircon age constraints  

NASA Astrophysics Data System (ADS)

The Samothraki mafic suite in the north-eastern Aegean Sea, Greece, is an 'in situ' magmatic complex comprising gabbros, sparse dykes and basalt flows and pillows cut by late dolerite dykes. We have determined the age of the complex by SHRIMP zircon geochronology of a gabbro as 159.9 ± 4.5 Ma (i.e. Oxfordian; early Late Jurassic), which precludes any correlation with the so-called Lesvos ophiolite further south (253.1 ± 5.6 Ma; Latest Permian). Six distinct, hitherto unrecognised, geochemical groups have been identified among the basalts and dolerites of the Samothraki mafic suite on the basis of trace-element and Nd-Sr isotopic characteristics. All groups show the presence of an enriched component in their source region, be that a long-term enriched mantle reservoir or an enriched melt. They also invariably show evidence of the addition of subduction-related hydrous fluids. Some groups testify to recent depletion events of long-term enriched mantle, some to the involvement of strongly depleted, recently refertilised mantle, and others to significant addition of melts either from subducted sediments or continental crust. None of the groups bear resemblance to mid-ocean ridge or back-arc basin basalts thus suggesting that the Samothraki mafic suite cannot represent mature back-arc basin crust. In view of recent advances in back-arc basin geology and the data collected here, the Samothraki mafic suite could represent a slab-edge segment of an evolved back-arc basin near the trench, a situation that satisfies the inflow of fertile mantle, the strong signature of sediment melts and the rare occurrence of boninite-like melts. Alternatively, it could represent the embryonic stages of back-arc basin formation either by a propagating rift tip into continental crust or by oblique subduction causing back-arc rifting of continental crust and creation of nascent transtensional basins. Restoration of block configuration in NE Greece before extensional collapse of the Hellenic hinterland and exhumation of the Rhodope Metamorphic Core Complex (mid-Eocene to mid-Miocene) results in a continuous ophiolite belt from Guevgueli to Samothraki, thus assigning the latter to the Innermost Hellenic Ophiolite Belt. We propose that the Samothraki mafic suite originated via rift propagation of the Sithonia ophiolite spreading ridge into the Chortiatis calc-alkaline arc (and its basement) which was partly assimilated. Our model does not favour southward intra-oceanic subduction of the Meliata-Maliac Ocean under the Vardar Ocean whereby Samothraki is located in the back-arc spreading centre. The autochthonous rift-related origin, the enriched geochemical characteristics and the lack of common features with known ophiolite types suggests calling the igneous complex of Samothraki Island a "mafic suite" rather than an "ophiolite".

Koglin, Nikola; Kostopoulos, Dimitrios; Reischmann, Thomas

2009-07-01

288

Earth Observatory Satellite system definition study. Report no. 5: System design and specifications. Part 1: Observatory system element specifications  

NASA Technical Reports Server (NTRS)

The performance, design, and quality assurance requirements for the Earth Observatory Satellite (EOS) Observatory and Ground System program elements required to perform the Land Resources Management (LRM) A-type mission are presented. The requirements for the Observatory element with the exception of the instruments specifications are contained in the first part.

1974-01-01

289

Rare earth elements in soils from selected areas on the Island of Hawaii  

SciTech Connect

Fifty soil samples for the wet, windward (east) side and dry, leeward (west) side of the Island of Hawaii were analyzed for La, Ce, Sm, Eu, Yb, and Lu by neutron activation/gamma-ray spectroscopic analysis. Data on concentrations in each sample are listed and analyzed statistically for soil samples collected from the western slope of Kohala Mountain, the western coastal plain of Mauna Kea, and the Northeastern coastal plain of Maunal Loa. Rare earth element (REE) concentrations are two to six times greater in soils from the western, dry side of the island, and good statistical correlation is exhibited among the samples for pairs of individual REEs. In the organic-rich soils of the east side, correlations are poor but are markedly improved when sample weights are adjusted for weight due to organic matter and water in soil colloids. If the mean compositions of selected rock samples from the Hawaii Reference Suite are representative of the compositions of the parent materials, REEs in the soils are moderately enriched (up to two times, based on oven-dry weights). Rare earth element concentrations in the island's western soils are as much as two times greater than the mean REE values of common sedimentary rocks worldwide; however, they are well within the concentration ranges of soils of continental origin. The eastern soils tend to have less La and Ce, but similar amounts of the middle and heavy REEs.

Barnard, W.M.; Halbig, J.B.

1985-07-01

290

Rare earth element components in atmospheric particulates in the Bayan Obo mine region.  

PubMed

The Bayan Obo mine, located in Inner Mongolia, China, is the largest light rare earth body ever found in the world. The research for rare earth elements (REEs) enrichment in atmospheric particulates caused by mining and ore processing is fairly limited so far. In this paper, atmospheric particulates including total suspended particulate (TSP) matter and particles with an equivalent aerodynamic diameter less than 10 ?m (PM10) were collected around the Bayan Obo mine region, in August 2012 and March 2013, to analyze the levels and distributions of REEs in particles. The total concentrations of REEs for TSP were 149.8 and 239.6 ng/m(3), and those for PM10 were 42.8 and 68.9 ng/m(3), in August 2012 and March 2013, respectively. Enrichment factor was calculated for all 14 REEs in the TSP and PM10 and the results indicated that REEs enrichment in atmosphere particulates was caused by anthropogenic sources and influenced by the strong wind in springtime. The spatial distribution of REEs in TSP showed a strong gradient concentration in the prevailing wind direction. REE chondrite normalized patterns of TSP and PM10 were similar and the normalized curves inclined to the right side, showing the conspicuous fractionation between the light REEs and heavy REE, which supported by the chondrite normalized concentration ratios calculated for selected elements (La(N)/Yb(N), La(N)/Sm(N), Gd(N)/Yb(N)). PMID:24657942

Wang, Lingqing; Liang, Tao; Zhang, Qian; Li, Kexin

2014-05-01

291

Determination of Earth structure using waveform inversion and Spectral-Element Method  

NASA Astrophysics Data System (ADS)

Recent progress in large scale computing by using Spectral-Element Method and the Earth Simulator has demonstrated possibilities to perform full-waveform inversion of three dimensional (3D) seismic velocity structure inside the Earth. Specifically Liu and Tromp (2006) have shown that it becomes feasible to compute finite frequency kernel for seismic velocity structure based on adjoint method. We plan to apply their method to obtain 3D velocity structure beneath East Asia. We take one chunk from global mesh of Spectral-Element Method and compute synthetic seismograms with accuracy of about 10 second. We use GAP-P2 mantle tomography model (Obayashi et al., 2009) as an initial 3D model and try to use as many broadband seismic stations available in this region, including Ocean Bottom Seismographs deployed in Philippine sea, as possible to perform inversion. Before accumulating finite frequency adjoint kernels for seismic velocity structure, we estimated influences of the initial 3D model on the focal mechanism and hypocenter location. We chose earthquakes occurred at various locations and depths in this region from Global CMT catalog. We picked up time windows for P and S waves that give decent match between data and synthetics for 3D model and determine the best fit solutions for source mechanism and hypocenter. We found that the redetermined solutions do not differ much from the Global CMT solutions, which shows that he Global CMT solutions can be used as initial solutions in the inversion. We then use the time windows for P and S waves to compute adjoint sources and calculate adjoint kernels for seismic velocity structure. We will discuss source and receiver pairs obtained in this region for the inversion and the sensitivities of the kernels to specific structure inside Earth.

Obayashi, M.; Tsuboi, S.; Tono, Y.; Suetsugu, D.

2010-12-01

292

Computational Design of Solar Energy Harvesting Materials Made of Earth-Abundant Elements  

NASA Astrophysics Data System (ADS)

Very large-scale deployment of photovoltaic (PV) technology based on both the first and second generation solar cells posts serious questions on the materials supply as they rely on either high-purity and high-quality silicon crystals or rare elements such as indium and tellurium. ``Ancient'' PV materials made of earth-abundant elements, such as oxides and sulfides of copper and iron, have attracted resurgent interests. There is also intensive research devoted to the search for ``modern'' earth-abundant PV materials, with a recent promising example being Cu2ZnSnSe4. Computational approaches play a key role in this endeavor by guiding the screening and optimization of the materials toward high device performance. In this paper, I will focus on two aspects of computational design of earth-abundant PV materials. First, I will discuss the methods for accurately predicting band gaps of semiconductor materials. The emphasis will be on the performance of hybrid functional method on different classes of materials. Based on these understandings, I will discuss how to tune the band gap of a material to match the solar spectrum. For example, one could reduce of the band gap of anatase to 1.5 eV by the chemical codoping approach. Second, I will discuss the methods for accurate computation of defect properties, which is important as the defectiveness is intrinsic to the low-cost synthesized materials. I will introduce a method for calculation of defect formation energies by minimizing the error due to the ``band-gap problem'' of the density functional theory. I will also discuss approaches to mitigating the effects of defects, e.g., by passivation.

Sun, Yiyang

2012-02-01

293

Physicochemical variations in atmospheric aerosols recorded at sea onboard the Atlantic-Mediterranean 2008 Scholar Ship cruise (Part II): Natural versus anthropogenic influences revealed by PM 10 trace element geochemistry  

NASA Astrophysics Data System (ADS)

The geochemistry of PM 10 filter samples collected at sea during the Scholar Ship Atlantic-Mediterranean 2008 research cruise reveals a constantly changing compositional mix of pollutants into the marine atmosphere. Source apportionment modelling using Positive Matrix Factorization identifies North African desert dust, sea spray, secondary inorganic aerosols, metalliferous carbon, and V-Ni-bearing combustion particles as the main PM 10 factors/sources. The least contaminated samples show an upper continental crust composition (UCC)-normalised geochemistry influenced by seawater chemistry, with marked depletions in Rb, Th and the lighter lanthanoid elements, whereas the arrival of desert dust intrusions imposes a more upper crustal signature enriched in "geological" elements such as Si, Al, Ti, Rb, Li and Sc. Superimposed on these natural background aerosol loadings are anthropogenic metal aerosols (e.g. Cu, Zn, Pb, V, and Mn) which allow identification of pollution sources such as fossil fuel combustion, biomass burning, metalliferous industries, and urban-industrial ports. A particularly sensitive tracer is La/Ce, which rises in response to contamination from coastal FCC oil refineries. The Scholar Ship database allows us to recognise seaborne pollution sourced from NW Africa, the Cape Verde and Canary islands, and European cities and industrial complexes, plumes which in extreme cases can produce a downwind deterioration in marine air quality comparable to that seen in many cities, and can persist hundreds of kilometres from land.

Moreno, Teresa; Pérez, Noemi; Querol, Xavier; Amato, Fulvio; Alastuey, Andrés; Bhatia, Ravinder; Spiro, Baruch; Hanvey, Melanie; Gibbons, Wes

2010-07-01

294

Composition of the earth's upper mantle-I. Siderophile trace elements in ultramafic nodules  

USGS Publications Warehouse

Seven siderophile elements (Au, Ge, Ir, Ni, Pd, Os, Re) were determined by radiochemical neutron activation analysis in 19 ultramafic rocks, which are spinel lherzollites-xenoliths from North and Central America, Hawaii and Australia, and garnet Iherzolitexenoliths from Lesotho. Abundances of the platinum metals are very uniform in spinel lherzolites averaging 3.4 ?? 1.2 ppb Os, 3.7 ?? 1.1 ppb Ir, and 4.6 ?? 2.0 ppb Pd. Sheared garnet lherzolite PHN 1611 has similar abundances of these elements, but in 4 granulated garnet lherzolites, abundances are more variable. In all samples, the Pt metals retain cosmic ( Cl-chondrite) ratios. Abundances of Au and Re vary more than those of Pt metals, but the Au/Re ratio remains close to the cosmic value. The fact that higher values of Au and Re approach cosmic proportions with respect to the Pt metals, suggests that Au and Re have been depleted in some ultramafic rocks from an initially chondrite-like pattern equivalent to about 0.01 of Cl chondrite abundances. The relative enrichment of Au and Re in crustal rocks is apparently the result of crust-mantle fractionation and does not require a special circumstance of core-mantle partitioning. Abundances of moderately volatile elements Ni, Co and Ge are very uniform in all rocks, and are much higher than those of the highly siderophile elements Au, Ir, Pd, Os and Re. When normalized to Cl chondrites, abundances of Ni and Co are nearly identical, averaging 0.20 ?? 0.02 and 0.22 ?? 0.02, respectively; but Ge is only 0.027 ?? 0.004. The low abundance of Ge relative to Ni and Co is apparently a reflection of the general depletion of volatile elements in the Earth. The moderately siderophile elements cannot be derived from the same source as the highly siderophile elements because of the marked difference in Cl chondrite-normalized abundances and patterns. We suggest that most of the Ni, Co and Ge were enriched in the silicate by the partial oxidation of pre-existing volatile-poor Fe-Ni, whereas the corresponding highly siderophile elements remained sequestered by the surviving metal. The highly siderophile elements may have been introduced by a population of ~103 large (~1022 g) planetisimals, similar to those forming the lunar mare basins. ?? 1981.

Morgan, J. W.; Wandless, G. A.; Petrie, R. K.; Irving, A. J.

1981-01-01

295

Thermodynamic properties of the rare earth element vapor complexes LnAl{sub 3}Cl{sub 12} from Ln = La to Ln = Lu  

SciTech Connect

The rare earth element complexes have never been analyzed in the gaseous state due to experimental concerns. The thermodynamic properties of rare earth element complexes are important for various applications, from high-intensity discharge lamps to recovery of rare earth metals. 46 refs., 4 figs., 1 tab.

Zhi-Chang Wang; Lin-Shan Wang [Northeastern Univ., Liaoning (China)

1997-04-09

296

'Nano' Morphology and Element Signatures of Early Life on Earth: A New Tool for Assessing Biogenicity  

NASA Technical Reports Server (NTRS)

The relatively young technology of NanoSIMS is unlocking an exciting new level of information from organic matter in ancient sediments. We are using this technique to characterize Proterozoic organic material that is clearly biogenic as a guide for interpreting controversial organic structures in either terrestrial or extraterrestrial samples. NanoSIMS is secondary ion mass spectrometry for trace element and isotope analysis at sub-micron resolution. In 2005, Robert et al. [1] combined NanoSIMS element maps with optical microscopic imagery in an effort to develop a new method for assessing biogenicity of Precambrian structures. The ability of NanoSIMS to map simultaneously the distribution of organic elements with a 50 nm spatial resolution provides new biologic markers that could help define the timing of life s development on Earth. The current study corroborates the work of Robert et al. and builds on their study by using NanoSIMS to map C, N (as CN), S, Si and O of both excellently preserved microfossils and less well preserved, non-descript organics in Proterozoic chert from the ca. 0.8 Ga Bitter Springs Formation of Australia.

Oehler, D. Z.; Mostefaoui, S.; Meibom, A.; Selo, M.; McKay, D. S.; Robert, F.

2006-01-01

297

Earth  

NSDL National Science Digital Library

With three levels to choose from on each page - beginner, intermediate or advanced - this site provides information on our plant Earth. There is a section about water on earth and its many different varities, like freshwater, groundwater, and frozen water. There is information about the chemical make-up of water and many images showing the different water anvironments. There is a section about life in water, such as animals, plants, and plankton.

2008-10-03

298

Partition coefficients for rare earth elements in mafic minerals of high silica rhyolites: the importance of accessory mineral inclusions  

Microsoft Academic Search

REE concentrations of mafic mineral separates from high-silica rhyolites measured by INAA are high and variable compared to electron microprobe analyses of the minerals themselves. The mafic phases commonly contain inclusions or have adhering grains of accessory rare earth element (REE)-rich minerals. Optical and electron microscopic observation revealed discrete grains of chevkinite (rare earth titano-silicate) included within clinopyroxenes from the

P MICHAEL

1988-01-01

299

Partition coefficients for rare earth elements in mafic minerals of high silica rhyolites: The importance of accessory mineral inclusions  

Microsoft Academic Search

REE concentrations of mafic mineral separates from high-silica rhyolites measured by INAA are high and variable compared to electron microprobe analyses of the minerals themselves. The mafic phases commonly contain inclusions or have adhering grains of accessory rare earth element (REE)-rich minerals. Optical and electron microscopic observation revealed discrete grains of chevkinite (rare earth titano-silicate) included within clinopyroxenes from the

Peter J. Michael

1988-01-01

300

Development and application of a sensitive and rapid analytical method to determine the rare-earth elements in surface waters  

Microsoft Academic Search

A new cost-effective method to determine the 14 rare-earth elements (REE's) in waters to levels as low as 0.2–1.0 ng l?1 (ppt) has been established. Inductively coupled plasma mass spectrometry (ICP-MS) is used for measurement following automated preconcentration using the Dionex® MetPac CC-1 resin of iminodiacetate functionality. The free REE ion is chelated onto the resin while alkali and alkaline-earth

Gwendy E. M. Hall; Judy E. Vaive; John W. McConnell

1995-01-01

301

Origin of middle rare earth element enrichment in acid mine drainage-impacted areas.  

PubMed

The commonly observed enrichment of middle rare earth elements (MREE) in water sampled in acid mine drainage (AMD)-impacted areas was found to be the result of preferential release from the widespread mineral pyrite (FeS2). Three different mining-impacted sites in Europe were sampled for water, and various pyrite samples were used in batch experiments with diluted sulphuric acid simulating AMD-impacted water with high sulphate concentration and high acidity. All water samples independent on their origin from groundwater, creek water or lake water as well as on the surrounding rock types showed MREE enrichment. Also the pyrite samples showed MREE enrichment in the respective acidic leachate but not always in their total contents indicating a process-controlled release. It is discussed that most probably complexation to sulphite (SO3 (2-)) or another intermediate S-species during pyrite oxidation is the reason for the MREE enrichment in the normalized REE patterns. PMID:24385183

Grawunder, Anja; Merten, Dirk; Büchel, Georg

2014-06-01

302

Rare earths, other trace elements and iron in Luna 20 samples.  

NASA Technical Reports Server (NTRS)

The results of the analysis by neutron activation of six samples from the Luna 20 mission and one sample of less than 1 mm fines from Apollo 16 are reported. The concentrations of the rare-earth elements (REE) in the samples of fines from Luna 20 and Apollo 16 are less than those found for corresponding materials from the mare areas but a negative Eu anomaly is still present. The concentrations of the REE in fines from Luna 20 are only about two-thirds as great as in the sample of Apollo 16 fines, but the concentration of Co, Sc and Cr are greater by factors ranging from 1.5 to 2.3.

Helmke, P. A.; Blanchard, D. P.; Jacobs, J. W.; Haskin, L.; Haskin, A.

1973-01-01

303

Light shifts and magic wavelengths for heavy alkaline earth elements: Ba and Ra  

NASA Astrophysics Data System (ADS)

In this paper, we investigate light shifts of heavy alkaline earth elements barium (Ba) and radium (Ra), which are interesting for optical lattice clocks and for permanent electric dipole moment searches. Detailed knowledge is required in the design of efficient loading of atoms from a magneto-optical trap into an optical dipole trap, to facilitate Doppler cooling while trapping and to achieve longer lifetimes of the trapped atoms with reduced heating rates. The wavelength dependence of light shifts of the ns2 1S0 ground state, the nsnp 3P1 and ns(n - 1)d 1D2 excited states in barium (n = 6) and the n s2 1S0 ground state, the nsnp 3P1 and ns(n - 1)d 3D2 excited states in radium (n = 7) are calculated. Several magic wavelengths in the visible and infrared regions accessible with commercial lasers for optical dipole trapping of Ba and Ra are identified.

Dammalapati, U.; Santra, B.; Willmann, L.

2012-01-01

304

Isomorphous substitutions of rare earth elements for calcium in synthetic hydroxyapatites.  

PubMed

Polycrystalline hydroxyapatites Ca(10-x)REE(x)(PO(4))(6)(OH)(2-x)O(x) were synthesized and studied by X-ray powder diffraction, infrared absorption, diffuse-reflectance spectroscopy, and thermogravimetry. The solubility limits x(max) of rare earth elements (REE) in Ca hydroxyapatites decreases with an increasing REE atomic number from x(max) = 2.00 for La, Pr, and Nd to x(max) = 0.20 for Yb at 1100 °C. Refinements of X-ray diffraction patterns by the Rietveld method show that REE atoms substitute for Ca preferentially at the Ca(2) sites of the apatite structure. The substitution decreases the Ca(2)-O(4) atomic distances in the calcium coordination polyhedra and increases the Ca(2)-O(1,2,3) distances. This observation shows that interatomic distances depend not only on radii of the ions involved in the substitution but also on their charges. PMID:20957990

Ardanova, Lyudmyla I; Get'man, Evgeni I; Loboda, Stanislav N; Prisedsky, Vadim V; Tkachenko, Tatiana V; Marchenko, Valeriy I; Antonovich, Valeriy P; Chivireva, Nataliya A; Chebishev, Konstantin A; Lyashenko, Alexandra S

2010-11-15

305

Behavior of Rare Earth Element In Geothermal Systems; A New Exploration/Exploitation Tool  

SciTech Connect

The goal of this four-year project was to provide a database by which to judge the utility of the rare earth elements (REE) in the exploration for and exploitation of geothermal fields in the United States. Geothermal fluids from hot springs and wells have been sampled from a number of locations, including: (1) the North Island of New Zealand (1 set of samples); (2) the Cascades of Oregon; (3) the Harney, Alvord Desert and Owyhee geothermal areas of Oregon; (4) the Dixie Valley and Beowawe fields in Nevada; (5) Palinpion, the Philippines: (6) the Salton Sea and Heber geothermal fields of southern California; and (7) the Dieng field in Central Java, Indonesia. We have analyzed the samples from all fields for REE except the last two.

Scott A. Wood

2002-01-28

306

Enhancement of ferroelectricity and ferromagnetism in rare earth element doped BiFeO3  

NASA Astrophysics Data System (ADS)

Rare earth element doped BiFeO3 thin films were fabricated using the pulsed laser deposition method and various targets made from different starting Fe2O3 and Fe3O4 iron source materials. The films fabricated using the targets made from Fe3O4 exhibit great enhancement in their ferroelectricity, due to greatly reduced electrical leakage, as well as enhanced magnetization compared to those films deposited using targets from Fe2O3. It is suggested that the Fe2+ ion plays an important role in compensating for the charge imbalance and reducing current leakage, as well as enhancing the magnetic moment through the introduction of antiferrimagnetic ordering at Fe2+ site.

Cheng, Z. X.; Wang, X. L.; Dou, S. X.; Kimura, H.; Ozawa, K.

2008-12-01

307

Distribution of rare earth elements and uranium in various components of ordinary chondrites  

NASA Astrophysics Data System (ADS)

Rare earth elements (REE) and uranium were studied for their distributions in various component phases of four ordinary chondrites. Kesen (H4), Richardton (H5), Bruderheim (L6), and Saint Severin (LL6). A selective dissolution method was applied for the phase fractionation. The REE were analysed by neutron activation analysis, and U was determined by neutron-induced fission tracks. The present study revealed that both REE and U are highly enriched in the Ca-phosphate minerals with different enrichment factors, implying chemical fractionation between them. The phosphates seem to be responsible for more than 80 percent of the light REE in all chondrites. On the other hand, only 20-40 percent of the total U resides in the Ca-phosphates. This difference in enrichments might have been caused through the levels of metamorphic activity on the meteoritic parent bodies.

Ebihara, M.; Honda, M.

1984-06-01

308

Effects of continents on Earth cooling: Thermal blanketing and depletion in radioactive elements  

NASA Astrophysics Data System (ADS)

Estimate of mantle heat flow under continental shields are very low, indicating a strong insulating effect of continents on mantle heat loss. This effect is investigated with a simple approach: continents are introduced in an Earth cooling model as perfect thermal insulators. Continental growth rate has then a strong influence on mantle cooling. Various continental growth models are tested and are used to compute the mantle depletion in radioactive elements as a function of continental crust extraction. Results show that the thermal blanketing effect of continents strongly affects mantle cooling, and that mantle depletion must be taken into account in order not to overestimate mantle heat loss. In order to obtain correct oceanic heat flow for present time, continental growth must begin at least 3 Gy ago and steady-state for continental area must be reached for at least 1.5 Gy in our cooling model.

Grigné, Cécile; Labrosse, Stéphane

309

Galileo Earth approach navigation using connected-element interferometer phase-delay tracking  

NASA Technical Reports Server (NTRS)

The application of a Connected-Element Interferometer (CEI) to the navigation of the Galileo spacecraft during its encounter with Earth in December 1990 is investigated. A CEI tracking demonstration is planned for the week of November 11 through 18, 1990, from 27 days to 20 days prior to Earth encounter on December 8. During this period, the spacecraft will be tracked daily with Deep Space Network Stations 13 and 15 at Goldstone. The purpose of this work is twofold: first, to establish and define the navigation performance expected during the tracking demonstration and, second, to study, in a more general sense, the sensitivity of orbit demonstration results obtained with CEI to the data density within CEI tracking passes and to important system parameters, such as baseline orientation errors and the phase-delay measurement accuracy. Computer simulation results indicate that the use of CEI data, coupled with conventional range and Doppler data, may reduce the uncertainty in the declination of the spacecraft's incoming trajectory by 15 to 66 percent compared with the operational solution using range and Doppler data only. The level of improvement depends upon the quantity and quality of the CEI data.

Thurman, S. W.

1990-01-01

310

Rare earth elements in human hair from a mining area of China.  

PubMed

Rare earth minerals have been mined for more than 50 years in Inner Mongolia of China. In the mining area rare earth elements (REE) may be significantly accumulated in humans. Therefore, the aim of this paper is to characterize the REE concentrations in hair of local residents. REE concentrations in hair of 118 subjects were determined. The results showed that the mean concentrations of the determined REE in the hair of both females and males were usually higher from mining area than from control area. The mean concentrations of all the fifteen REE were much higher in hair of males than in hair of females from mining area. This suggested that males might be more sensitive to REE than females. In addition, the mean contents of the REE in hair of miners, particularly light REE (La, Ce, Pr and Nd), were usually much higher than the values in hair of non-miners from both mining area and control area, indicating that the miners were exposed to higher concentrations of REE in occupational environment. Among age groups, the relationships between REE concentrations and age groups showed that more and more concentrations of light REE accumulated in body of both females and males with age until 60 years, while heavy REE concentrations decreased with age in males who were exposed to low concentrations of heavy REE. PMID:23830573

Wei, Binggan; Li, Yonghua; Li, Hairong; Yu, Jiangping; Ye, Bixiong; Liang, Tao

2013-10-01

311

Quantitative estimation of concentrations of dissolved rare earth elements using reflectance spectroscopy  

NASA Astrophysics Data System (ADS)

Characteristic spectral parameters such as the wavelength and depth of absorption bands are widely used to quantitatively estimate the composition of samples from hyperspectral reflectance data in soil science, mineralogy as well as vegetation study. However, little research has been conducted on the spectral characteristic of rare earth elements (REE) and their relationship with chemical composition of aqueous solutions. Reflectance spectra of ore leachate solutions and contaminated stream water from a few REE mines in the Jiangxi Province, China, are studied for the first time in this work. The results demonstrate that the six diagnostic absorption features of the rare earths are recognized in visible and near-infrared wavelengths at 574, 790, 736, 520, 861, and 443 nm. The intensity of each of these six absorption bands is linearly correlated with the abundance of total REE, with the r2 value >0.95 and the detection limit at ?75,000 ?g/L. It is suggested that reflectance spectroscopy provides an ideal routine analytical tool for characterizing leachate samples. The outcome of this study also has implications for monitoring the environmental effect of REE mining, in particular in stream water systems by hyperspectral remote sensing.

Dai, Jingjing; Wang, Denghong; Wang, Runsheng; Chen, Zhenghui

2013-01-01

312

Rare earth element complexation by PO 43- ions in aqueous solution  

NASA Astrophysics Data System (ADS)

Complexation of trivalent rare earths by PO 43- ions has been assessed at t = 25° C by examining the influence of aqueous phosphate concentrations on the distributions of 144Ce and 153Gd between 0.68 molar NaClO 4 and tributyl phosphate (TBP). Estimated Ce 3+ and Gd 3+ phosphate complexation constants appropriate to zero ionic strength are Ce3+ + PO43- ? CePO40; logL?10 ? 11.7 Gd3+ + PO43- ? GdPO40; logL?1o = 12.2. Our estimates of these formation constants at zero ionic strength are approximately seven to eight orders of magnitude lower than previously reported estimates for lanthanide and actinide PO 43- complexation. Linear free energy relationships relating the complexation of Ca 2+ and lanthanides (Ln 3+) by a variety of organic ligands, in conjunction with previous direct observations of CaPO 4- formation, are consistent with the experimentally derived CePO 40 and GdPO 40 formation constants reported in this work. Gadolinium speciation calculations indicate that the PO 43- ion can effectively compete with the CO 32- ion for free Gd 3+ in model groundwater at pH 7-9. Rare earth element phosphate complexation is a significant process in natural freshwater systems which are neutral to mildly basic when the concentration ratio [HPO 42-] /[HCO 3-] is greater than approximately 1 × 10 -3.

Byrne, Robert H.; Lee, Jong Hyeon; Bingler, Linda S.

1991-10-01

313

Determination of Earth structure using waveform inversion and Spectral-Element Method for Eastern Asian region  

NASA Astrophysics Data System (ADS)

Recent progress in large scale computing by using Spectral-Element Method and the Earth Simulator has demonstrated possibilities to perform full-waveform inversion of three dimensional (3D) seismic velocity structure inside the Earth. Specifically Liu and Tromp (2006) have shown that it becomes feasible to compute finite frequency kernel for seismic velocity structure based on adjoint method. We apply their method to obtain 3D velocity structure beneath East Asia. We take one chunk from global mesh of Spectral-Element Method and compute synthetic seismograms with accuracy of about 10 second. We use GAP-P2 mantle tomography model (Obayashi et al., 2009) as an initial 3D model and try to use as many broadband seismic stations available in this region, including Ocean Bottom Seismographs deployed in Philippine sea, as possible to perform inversion. We calculate synthetic seismograms for this initial 3D model and source receiver pairs. We then use the time windows for P and S waves to compute adjoint sources and calculate misfit adjoint kernels for seismic velocity structure. The kernels are calculated for all the time windows of P and S waves simultaneously. We sum up the event misfit kernels and perform the first iteration to improve the initial velocity model using the steepest decent method. The results of the first iteration shows that the differences between the initial model and the improved model is less than 1%, which shows that the modification resulted from the first iteration was quite modest. However the modifications to the initial model show different pattern among P-waves and S-waves, which implies that the scaling relation to obtain S-waves velocity model from P-wave velocity model might be revised in this region.

Tsuboi, S.; Obayashi, M.; Tono, Y.; Suetsugu, D.

2011-12-01

314

A major light rare-earth element (LREE) resource in the Khanneshin carbonatite complex, southern Afghanistan  

USGS Publications Warehouse

The rapid rise in world demand for the rare-earth elements (REEs) has expanded the search for new REE resources. We document two types of light rare-earth element (LREE)-enriched rocks in the Khanneshin carbonatite complex of southern Afghanistan: type 1 concordant seams of khanneshite-(Ce), synchysite-(Ce), and parisite-(Ce) within banded barite-strontianite alvikite, and type 2 igneous dikes of coarse-grained carbonatite, enriched in fluorine or phosphorus, containing idiomorphic crystals of khanneshite-(Ce) or carbocernaite. Type 1 mineralized barite-strontianite alvikite averages 22.25 wt % BaO, 4.27 wt % SrO, and 3.25 wt % ? LREE2O3 (sum of La, Ce, Pr, and Nd oxides). Type 2 igneous dikes average 14.51 wt % BaO, 5.96 wt % SrO, and 3.77 wt % ? LREE2O3. A magmatic origin is clearly indicated for the type 2 LREE-enriched dikes, and type 1 LREE mineralization probably formed in the presence of LREE-rich hydrothermal fluid. Both types of LREE mineralization may be penecontemporaneous, having formed in a carbonate-rich magma in the marginal zone of the central vent, highly charged with volatile constituents (i.e., CO2, F, P2O5), and strongly enriched in Ba, Sr, and the LREE. Based on several assumptions, and employing simple geometry for the zone of LREE enrichment, we estimate that at least 1.29 Mt (million metric tonnes) of LREE2O3 is present in this part of the Khanneshin carbonatite complex.

Tucker, Robert D.; Belkin, Harvey E.; Schulz, Klaus J.; Peters, Stephen G.; Horton, Forrest; Buttleman, Kim; Scott, Emily R.

2012-01-01

315

Natural radioactivity and rare earth elements in feldspar samples, Central Eastern desert, Egypt.  

PubMed

The pegmatite bodies of the Eastern Desert of Egypt are widely distributed especially along the Marsa-Alam-Idfu road. The Abu Dob area covers about 150km(2) of the Arabian Nubian shield at the central part of the Eastern Desert of Egypt. Most of the pegmatite is zoned; the zonation starts with milky quartz at the core followed by alkali feldspar at the margins. The feldspars vary in color from rose to milky and in composition from K-feldspar to Na-feldspar, sometimes interactions of both types are encountered. Thirteen feldspar samples were collected from different locations in the Abu Dob area for measuring the natural radioactivity of (238)U, (232)Th and (40)K using an HPGe detector. The variation in concentration of radionuclides for the area under investigation can be classified into regions of high, medium and low natural radioactivity. The average concentration in BqKg(-1) has been observed to be from 9.5 to 183675.7BqKg(-1) for (238)U, between 6.1 and 94,314.2BqKg(-1) for (232)Th and from 0 to 7894.6BqKg(-1) for (40)K. Radium equivalent activities (Ra(eq)), dose rate (D(R)) and external hazard (H(ex)) have also been determined. In the present work, the concentration of rare earth elements are measured for two feldspar samples using two techniques, Environmental Scanning Electron microscope XIL 30 ESEM, Philips, and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The existence of rare earth elements in this area are very high and can be used in different important industries. PMID:21324705

Walley El-Dine, Nadia; El-Shershaby, Amal; Afifi, Sofia; Sroor, Amany; Samir, Eman

2011-05-01

316

Rare earth element carriers in the Shergotty meteorite and implications for its chronology  

SciTech Connect

Ion probe measurements of the rare earth element (REE) concentrations of individual grains of the Shergotty meteorite are reported. Phases analyzed include whitlockite, apatite, baddeleyite, augite, pigeonite, maskelynite and K-rich glass. U concentrations of whitlockite and apatite crystals were also obtained. The whole rock REE pattern is dominated by whitlockite, which contains over 95% of the light rare earth elements (LREE). REE concentrations in apatite are much lower than estimated by Laul et al. (1986). All of the whitlockites have the same relative abundances of LREE. The observation, by Jones et al. (1985), of a skeletal whitlockite with LREE enrichment is not confirmed by analyses of the same grain. Pyroxene rims are not enriched in LREE. No leachable carrier, enriched in LREE and associated with pyroxene, has been found. Instead, either a laboratory contamination or a petrographically cryptic phase such as a film on grain boundaries is suspected as the carrier of LREE enrichments. Estimates of REE abundances in the Shergotty intercumulus melt indicate that a complex petrogenesis is required, in agreement with the conclusions of McKay et al. (1986a). Pyroxene distribution coefficients measured experimentally are compared with estimates from measured REE abundances in augite and pigeonite. Evolution of REE abundances in the Shergotty late-stage interstitial melt, as inferred from analyses of whitlockite, conforms with trends predicted from partitioning considerations, and requires no special processes such as metasomatism. The average U concentrations of whitlockite and apatite are respectively 540 and 1,550 ppb. Although the calcium phosphates are enriched in U, they contain less than 20% of the U in Shergotty.

Lundberg, L.L.; Crozaz, G.; Zinner, E. (Washington Univ., St. Louis, MO (USA)); McKay, G. (NASA, Johnson Space Center, Houston, TX (USA))

1988-08-01

317

Late Cenozoic volcanism in the Rio Grande rift: Trace element, strontium isotopic and neodymium isotopic geochemistry of the Taos Plateau volcanics  

SciTech Connect

This thesis evaluates rubidium-strontium and samarium-neodymium isotopic and trace element data for a suite of petrologically diverse continental volcanics from the northern Rio Grande rift of the southwestern US and assesses the role of crustal contamination in generating the observed geochemical variations. Covariations of strontium and neodymium isotopic compositions with rock type suggest the operation of crustal contamination. However, the compositional patterns are too complex to support a simple binary mixing model. Some trace element variations suggest that fractional crystallization has been a significant process in the generation of the sample suite. The preferred, but not unique, model to account for the chemical variations requires contamination of an oceanic-type mantle melt by a partial melt of relatively mafic lower crust. The implications of this analysis for the composition of subcontinental mantle on a regional scale are discussed in light of isotopic studies, both local and global, of other continental volcanics; it is suggested that continental volcanics erupted through thick crust may seldom arrive uncontaminated at the earth's surface. Consequently, subcontinental mantle may be considerably more and less radiogenic in neodymium and strontium, respectively, than the isotopic ratios of continental basalts have led the authors to believe.

Williams, S.

1984-01-01

318

X-ray fluorescence analysis of rare earth elements in rocks using low dilution glass beads.  

PubMed

Major and trace elements (Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Rb, Sr, Y, Zr, La, Ce, Pr, Nd, Sm, Gd, Dy, Th and U) in igneous rocks were assayed with fused lithium borate glass beads using X-ray fluorescence spectrometry. Low dilution glass beads, which had a 1:1 sample-to-flux ratio, were prepared for determination of rare earth elements. Complete vitrification of 1:1 mixture required heating twice at 1200 degrees C with agitation. Extra pure reagents containing determinants were used for calibrating standards instead of the rock standard. The calibration curves of the 23 elements showed good linearity. Furthermore, the lower limits of detection corresponding to three times the standard deviation for blank measurements were 26 mass ppm for Na2O, 6.7 for MgO, 4.5 for Al2O3, 4.5 for SiO2, 18 for P2O5, 1.1 for K2O, 4.0 for CaO, 3.9 for TiO2, 1.6 for MnO, 0.8 for Fe2O3, 0.5 for Rb, 0.2 for Sr, 0.4 for Y, 0.5 for Zr, 3.3 for La, 6.5 for Ce, 2.7 for Pr, 2.1 for Nd, 1.7 for Sm, 0.7 for Gd, 2.7 for Dy, 0.5 for Th, and 0.6 for U. Using the present method, we determined the contents of these 23 elements in four rhyolitic and granitic rocks from Japan. PMID:16038502

Nakayama, Kenichi; Nakamura, Toshihiro

2005-07-01

319

Structural Elements in a Persistent Identifier Infrastructure and Resulting Benefits for the Earth Science Community  

NASA Astrophysics Data System (ADS)

We propose a wide adoption of structural elements (typed links, collections, trees) in the Handle System to improve identification and access of scientific data, metadata and software as well as traceability of data provenance. Typed links target the issue of data provenance as a means to assess the quality of scientific data. Data provenance is seen here as a directed acyclic graph with nodes representing data and vertices representing derivative operations (Moreau 2010). Landing pages can allow a human user to explore the provenance graph back to the primary unprocessed data, thereby also giving credit to the original data producer. As in Earth System Modeling no single infrastructure with complete data lifecycle coverage exists, we propose to split the problem domain in two parts. Project-specific infrastructures such as the German project C3-Grid or the Earth System Grid Federation (ESGF) for CMIP5 data are aware of data and data operations (Toussaint et al. 2012) and can thus detect and accumulate single nodes and vertices in the provenance graph, assigning Handles to data, metadata and software. With a common schema for typed links, the provenance graph is established as downstream infrastructures refer incoming Handles. Data in this context is for example hierarchically structured Earth System model output data, which receives DataCite DOIs only for the most coarse-granular elements. Using Handle tree structures, the lower levels of the hierarchy can also receive Handles, allowing authors to more precisely identify the data they used (Lawrence et al. 2011). We can e.g. define a DOI for just the 2m-temperature variable of CMIP5 data across many CMIP5 experiments or a DOI for model and observational data coming from different sources. The structural elements should be implemented through Handle values at the Handle infrastructure level for two reasons. Handle values are more durable than downstream websites or databases, and thus the provenance chain does not break if individual links become unavailable. Secondly, a single service cannot interpret links if downstream solutions differ in their implementation schemas. Emerging efforts driven by the European Persistent Identifier Consortium (EPIC) aim to establish a default mechanism for structural elements at the Handle level. We motivate to make applications, which take part in the data lifecycle, aware of data derivation provenance and let them provide additional elements to the provenance graph. Since they are also Handles, DataCite DOIs can act as a corner stone and provide an entry point to discover the provenance graph. References B. Lawrence, C. Jones, B. Matthews, S. Pepler, and S. Callaghan, "Citation and peer review of data: Moving towards formal data publication," Int. J. of Digital Curation, vol. 6, no. 2, 2011. L. Moreau, "The foundations for provenance on the web," Foundations and Trends® in Web Science, vol. 2, no. 2-3, pp. 99-241, 2010. F. Toussaint, T. Weigel, H. Thiemann, H. Höck, M. Stockhause: "Application Examples for Handle System Usage", submitted to AGU 2012 session IN009.

Weigel, T.; Toussaiant, F.; Stockhause, M.; Höck, H.; Kindermann, S.; Lautenschlager, M.; Ludwig, T.

2012-12-01

320

Key Factors Controlling Space- and Time-Linked Rare Earth Element Distribution in Shallow Groundwaters  

NASA Astrophysics Data System (ADS)

This study investigates the effects of source-rock composition, redox changes and organic matter on the hydrochemistry of Rare Earth Elements (REE). Wetland groundwater samples as well as upland zone water samples were recovered weekly over a six month period (January to June 1999) from a small catchment (Petit Hermitage, France). The samples were filtered on the field using membrane filters of 0.22 ? m pore size, and then analyzed for their Dissolved Organic Carbon (DOC) as well as Fe, Mn, Al, Th, U and REE concentrations. The results are discussed in conjunction with previous published DOC and trace-element concentrations obtained on comparable samples from three other small catchments, namely : the Nsimi-Zoetele, Goyoum (both in Cameroon) and Kervidy/Coet-Dan (France) catchments (Viers et al., 1997; Braun et al., 1998; Dia et al., 2000). Despite marked differences (such as bioclimatic conditions, vegetation cover, basement rock composition or human activity), results are surprisingly similar with always the occurrence of two spatially distinct groundwater types including : (i) a shallow, organic-rich groundwater below wetlands recording high and variable REE contents and displaying slight or no negative Ce anomaly. In the wetland groundwaters, the REE and other trace-element concentrations seem to be controlled by seasonal dynamics, involving both temperature, whose onset at spring leads to higher organic carbon decomposition rates by microbial mass, and redox changes resulting in REE and other-trace element release in water when mineral phases occur to dissolve. (ii) The second groundwater type corresponds to a shallow, organic-poor groundwater type located below the hillslope domains. This second groundwater type displays lower REE (and other trace-element) concentrations, but distinguish from the former by the occurrence of very strong negative Ce anomalies, whose amplitude is variable, but appears to be linked to the sampling location along the catena. The comparison of the different catchments shows that the spatial variability of the REE signatures between the hillslope DOC-poor groundwaters and the wetland DOC-rich groundwaters has to be the same whatever may be the climatic and geologic context. These results assess the key roles played in the REE transfer to hydrosystems by (i) the occurrence of organic compounds, acting as a trace-element carrier phase and (ii) redox condition changes. Finally, we propose that topography could be the ultimate key factor, through its ability to control the water table depth and therefore the organic colloids enrichment when groundwaters are flowing into organic-rich soil horizons.

Dia, A.; Gruau, G.; Olivie-Lauquet, G.; Henin, O.; Petitjean, P.; Le Coz-Bouhnik, M.

2001-12-01

321

Subduction Zone Redox and the Deep Earth Cycles of Sulfur and Chalcophile Elements  

NASA Astrophysics Data System (ADS)

Subduction at convergent plate margins is a return flux to the mantle of rocks influenced by weathering, hydrothermal activity, atmospheric exchange, or bio-mineralization in the exosphere. The latter exogenic processes modify the long-term abundance and behaviour of certain elements in the deeper earth that can be traced over time in the chemistry of mantle-derived magmas. The redox budget of subduction is controlled by the flux of oxidized versus reduced forms of Fe, S, H, or C, and impacts the long-term evolution of oxygen on the planet, critical for life in the exosphere. In particular, the sulfur cycle is specifically tied to the evolution of oxygen on Earth's surface over time and critical to biogeochemical cycles on the surface. The behaviour of sulfur in the exogenic system is well-studied and fairly well understood using sedimentary records. An originally sulfidic ocean on Earth gave way with time and oxygenation to one that is sulfate dominated over the last two billion years. In contrast, far less is known of the deep earth cycle of S, and more so its history. The record of the endogenic cycle can only be monitored via what comes out of the mantle (magmas and their gases), or what goes down via subduction (hydrothermally-altered or weathered subducted lithosphere). Interest in the endogenic cycle of S is not new but several outstanding conundrums remain for sulfur in arc magmas that point to the importance of the subduction process. A hitherto ignored component of the paradox of the sulfur cycle is the sedimentary veneer that sits atop the subducted oceanic basalt crust. Compilations show only 0.12 wt% S in altered ocean basalt crust, but up to 10 times that amount in oceanic sediments, tied to their Fe content (in pyrite). These abundances may seem trivial, but the behaviour of this small amount of S in subduction is not fully appreciated and its oxidation potential in the arc mantle is enormous. The conversion of subducted sulfide to sulfate is a 8-electron change in redox state, with significant oxidation/ reduction capacity. The concomitant higher fO2 can in turn facilitate the mobility and/or extraction of chalcophile metals from the arc mantle into magmas by the melting process in arcs. Sedimentary records show that through most of Earth's history sulfur has mostly been subducted in reduced form as sulfide. The fate of sulfide in ocean sediments during subduction (and subsequent dehydration or melting) has not been thoroughly investigated, nor its interplay with other redox couples (C, H, Fe) in sediments, subducted basalt or in the mantle. I examine the redox controls on sulfate versus sulfide stability in subducted oceanic crust, and their disposition relative to other redox couples in the mantle. Sulfate-sulfide equilibria impact the fate of sulfur and chalcophile elements in subducted lithologies, especially if dehydrated or melted depending on a variety subduction P-T trajectories. In this light, new high P-T experiments show the utility of Cu as a proxy for S in the subduction system . These proxies can potentially be applied to examine the deep S cycle, subduction redox and its role in arc magmatism over geologic time.

Canil, D.

2013-12-01

322

Earth  

NSDL National Science Digital Library

This NASA (National Aeronautics and Space Administration) planet profile provides data and images of the planet Earth. These data include planet size, orbit facts, distance from the Sun, rotation and revolution times, temperature, atmospheric composition, density, surface materials and albedo. Images with descriptions show Earth features such as the Ross Ice Shelf in Antarctica, Simpson Desert in Australia, Mt. Etna in Sicily, the Cassiar Mountains in Canada, the Strait of Gibraltar, Mississippi River, Grand Canyon, Wadi Kufra Oasis in Libya, and Moon images such as Hadley Rille, Plum Crater, massifs and Moon rocks. These images were taken with the Galileo Spacecraft and by the Apollo missions.

323

Rare Earth Element Tracing for Bamsar, Revesht and Nezam-Abad Tungsten Deposits in Central Iran  

NASA Astrophysics Data System (ADS)

Bamsar, Revesht and Nezam-Abad tungsten deposits are located southwest of Shazand in central Iran. Rare Earth Element (REE) and other trace elements in samples of scheelite (CaWO4) from these deposits have been determined by Neutron Activation Analysis in order to constrain the composition and sources of the mineralizing fluids. Paleozoic and Triassic volcano-sedimentary rocks and upper Triassic-Jurassic detrital-chemical and volcanic units outcrop in the Shazand region. The intrusives in the region have granitic and granodioritic compositions that have caused metamorphic haloes in the upper Triassic-Jurassic units. Six ore-bearing skarn horizons have been identified at Bamsar, while granodioritic intrusives host vein-type mineralization at Revesht and Nezam-Abad. Revesht and Nezam-Abad scheelites have higher total REE and Na concentrations than Bamsar samples. Bamsar scheelites show flat chondrite-normalized REE (REEN) patterns, whereas scheelites from Revesht and Nezam-Abad exhibit hump-shaped REEN patterns with maximum REEN concentrations displaced towards Dy. Following the findings of Ghaderi et al. (1999) on scheelites from Western Australian gold deposits, it is suggested that Bamsar scheelites have variable Eu anomalies and trivalent REE concentrations and thus appear to contain mostly Eu2+ and to have formed under reduced conditions. Revesht and Nezam-Abad scheelites, on the other hand, exhibit no changes in the size of the Eu anomaly with REE concentration, implying a predominance of Eu3+ and crystallization under relatively oxidized conditions. Bamsar scheelites have (Ce/Lu)N > 1 and are interpreted to have crystallized from LREE-enriched fluids, whereas Revesht and Nezam-Abad scheelites with (Ce/Lu)N < 1 formed from LREE-depleted fluids. The elevated Na contents of Revesht and Nezam-Abad scheelites compared with Bamsar samples, suggest crystallization from hydrothermal fluids with higher Na activities. Reference: Ghaderi, M., Palin, J.M., Campbell, I.H., & Sylvester, P.J. (1999): Rare earth element systematics in scheelite from hydrothermal gold deposits in the Kalgoorlie-Norseman region, Western Australia. Economic Geology, v. 94, p. 423-437.

Ghaderi, M.

2001-12-01

324

Using rare earth elements for the identification of the geographic origin of food  

NASA Astrophysics Data System (ADS)

The European Union defined regimes within the Protected Geographical Status (PGS) framework to protect names of regional food specialities. Thus only food produced in a specific geographical area with a specific way of production or quality can be protected by a protected geographical indication (PGI) label. As such Styrian Pumpkin Seed Oil has been approved with this label, but as with many other high priced regional specialities, fraud cannot be excluded or nor identified. Thus the aim of this work is, to develop an analytical method for the control of the geographic origin of pumpkin seed oil and also to test the method for other protected products. The development of such a method is not only of interest for scientists, but also of importance for the consumer wanting to know the origin of the food products and the assurance of the purity and quality. The group of rare earth elements (REE) in plants also have a characteristic distribution pattern similar to upper crustal REE distributions. Since the REE concentrations are extremely low in pumpkin seed oil (ppt to low ppb), ICP-MS was the only sensitive tool able to produce validated results. The carrier of the REE are most likely small particles distributed within the pumpkin seed oil. Unlike, e.g., olive oil, pumpkin seed oil is bottled and sold unfiltered, which makes this Styrian speciality an interesting sampling target. As pumpkin seed oils from different geographic origin show variable trace element and rare earth distribution patterns, is should possible to trace the origin of these oils. In the current project pumpkin seeds from different regions in Austria and from abroad were sampled. The trace element patterns in the extracted oil of these seeds were determined and a preliminary classification with discriminate analysis was successfully done on a statistical basis. In addition to the study of the geographic origin it was demonstrated that REE distribution patterns can also be used for the identification of adulteration of high priced pumpkin seed oil with cheap neutral tasting refined oils. Interestingly enough, the variations of the REE patterns between oils from different regions are much more pronounced than their host soils. Thus we assume that microbiological processes in the rhizosphere are in control of the REE uptake into the plant. Regional variations of the microbiological composition of the soils and probably not only a priori the bulk soil composition of the minerals in the soil are the cause of the regional variations making it possible to identify the geographic origin of pumpkin seeds and as a consequence the pumpkin seed oil.

Meisel, T.; Bandoniene, D.; Joebstl, D.

2009-04-01

325

Geochemistry of Groundwater  

NASA Astrophysics Data System (ADS)

Differentiation of terrestrial planets includes separation of a metallic core and possible later fractionation of mineral phases within either a solid or molten mantle (Figure 1). Lithophile and siderophile elements can be used to understand these two different physical processes, and ascertain whether they operated in the early Earth. The distribution of elements in planets can be understood by measuring the partition coefficient, D (ratio of concentrations of an element in different phases (minerals, metals, or melts)). (14K)Figure 1. Schematic cross-section through the Earth, showing: (a) an early magma ocean stage and (b) a later cool and differentiated stage. The siderophile elements (iron-loving) encompass over 30 elements and are defined as those elements for which D(metal/silicate)>1, and are useful for deciphering the details of core formation. This group of elements is commonly broken up into several subclasses, including the slightly siderophile elements (1elements (MSEs; 10elements (HSEs; D>104). Because these three groups encompass a wide range of partition coefficient values, they can be very useful in trying to determine the conditions under which metal may have equilibrated with the mantle (or a magma ocean). Because metal and silicate may equilibrate by several different mechanisms, such as at the base of a deep magma ocean, or as metal droplets descend through a molten mantle, partition coefficients can potentially shed light on which mechanism may be most important, thus linking the physics and chemistry of core formation. In this chapter, we summarize metal/silicate partitioning of siderophile elements and show how they may be used to understand planetary core formation.Once a planet is differentiated into core and mantle, a mantle will cool during convection, and can start in either a molten or solid state, depending upon the initial thermal conditions. If hot enough, minerals will crystallize from a molten mantle, and become entrained in the convecting melt, or eventually settle out at the bottom. The entrainment and settling process has been studied in detail (e.g., Tonks and Melosh, 1990), and is a potential mechanism for differentiation between the deep and shallow parts of Earth's mantle. The lithophile elements, those elements that have D(metal/silicate) <1, fall into many different subclasses and all hold information about the deep mineral structure of the mantle. Rare-earth elements (REEs) have proven to be useful: europium anomalies have helped elucidate the role of plagioclase in lunar crust formation (e.g., Schnetzler and Philpotts, 1971; Weill et al., 1974), and LREE/HREE depletion and enrichment are indicators of partial melting in the presence of garnet in the mantle. High-field-strength elements (HFSEs) - niobium, zirconium, tantalum, and hafnium - are all refractory and hence more resilient to fractionation processes such as volatility or condensation. They also have an affinity for ilmenite and rutile, and can explain differences between lunar and martian samples as well as features of Earth's continental crust ( Taylor and McLennan, 1985). Alkaline-earth and alkaline elements include rubidium, strontium, barium, potassium, caesium, and calcium, some of which are involved in radioactive decay couples, e.g., Rb-Sr and K-Ar. The latter is important in understanding the contribution of radioactive decay to planetary heat production, and potential deep sources of radiogenic argon (see Chapter 2.06). Rubidium and potassium are further useful as tracers of hydrous phases such as mica and amphibole. Possible fractionation of any of these elements from chondritic abundances (see Chapter 2.01) can be assessed with the knowledge of partition coefficients. In this chapter we summarize our understanding of mineral/melt fractionation of minor and trace elements at high pressures and temperatures and discuss the implications for mantle differentiation.

Chapelle, F. H.

2003-12-01

326

The genetics of geochemistry.  

PubMed

Bacteria are remarkable in their metabolic diversity due to their ability to harvest energy from myriad oxidation and reduction reactions. In some cases, their metabolisms involve redox transformations of metal(loid)s, which lead to the precipitation, transformation, or dissolution of minerals. Microorganism/mineral interactions not only affect the geochemistry of modern environments, but may also have contributed to shaping the near-surface environment of the early Earth. For example, bacterial anaerobic respiration of ferric iron or the toxic metalloid arsenic is well known to affect water quality in many parts of the world today, whereas the utilization of ferrous iron as an electron donor in anoxygenic photosynthesis may help explain the origin of Banded Iron Formations, a class of ancient sedimentary deposits. Bacterial genetics holds the key to understanding how these metabolisms work. Once the genes and gene products that catalyze geochemically relevant reactions are understood, as well as the conditions that trigger their expression, we may begin to predict when and to what extent these metabolisms influence modern geochemical cycles, as well as develop a basis for deciphering their origins and how organisms that utilized them may have altered the chemical and physical features of our planet. PMID:15568975

Croal, Laura R; Gralnick, Jeffrey A; Malasarn, Davin; Newman, Dianne K

2004-01-01

327

The geochemistry of iodine — a review  

Microsoft Academic Search

Iodine has long been recognised as an important element environmentally. Despite this there are many gaps in our knowledge of its geochemistry and even where information is available much of this is based on old data which, in the light of recent data, are suspect.Iodine forms few independent minerals and is unlikely to enter most rock-forming minerals. In igneous rocks

Ronald Fuge; Christopher C. Johnson

1986-01-01

328

Earth Abides Arsenic Biotransformations  

NASA Astrophysics Data System (ADS)

Arsenic is the most prevalent environmental toxic element and causes health problems throughout the world. The toxicity, mobility, and fate of arsenic in the environment are largely determined by its speciation, and arsenic speciation changes are driven, at least to some extent, by biological processes. In this article, biotransformation of arsenic is reviewed from the perspective of the formation of Earth and the evolution of life, and the connection between arsenic geochemistry and biology is described. The article provides a comprehensive overview of molecular mechanisms of arsenic redox and methylation cycles as well as other arsenic biotransformations. It also discusses the implications of arsenic biotransformation in environmental remediation and food safety, with particular emphasis on groundwater arsenic contamination and arsenic accumulation in rice.

Zhu, Yong-Guan; Yoshinaga, Masafumi; Zhao, Fang-Jie; Rosen, Barry P.

2014-05-01

329

A chemical-spectrochemical method for the determination of rare earth elements and thorium in cerium minerals  

USGS Publications Warehouse

In a combined chemical-spectrochemical procedure for quantitatively determining rare earth elements in cerium minerals, cerium is determined volumetrically, a total rare earths plus thoria precipitate is separated chemically, the ceria content of the precipitate is raised to 80??0 percent by adding pure ceria, and the resulting mixture is analyzed for lanthanum, praseodymium, neodymium, samarium, gadolinium, yttrium, and thorium spectrochemically by means of the d.c. carbon arc. Spectral lines of singly ionized cerium are used as internal standard lines in the spectrochemical determination which is patterned after Fassel's procedure [1]. Results of testing the method with synthetic mixtures of rare earths and with samples of chemically analyzed cerium minerals show that the coefficient of variation for a quadruplicate determination of any element does not exceed 5??0 (excepting yttrium at concentrations less than 1 percent) and that the method is free of serious systematic error. ?? 1954.

Rose, Jr. , H. J.; Murata, K. J.; Carron, M. K.

1954-01-01

330

Studies on Microbial Heavy Metal Retention from Uranium Mine Drainage Water with Special Emphasis on Rare Earth Elements  

Microsoft Academic Search

Microbial heavy metal retention was studied using seepage water sampled from a former uranium mining site in Eastern Thuringia, Germany. The seepage water has a low pH and contains high concentrations of metals, including uranium, rare earth elements (REE), and other heavy metals. Microbial influence on sorption and\\/or active uptake of heavy metals was studied using REE patterns. Incubation of

D. Merten; E. Kothe; G. Büchel

2004-01-01

331

Crystal-chemical controls on rare-earth element concentrations in fossil biogenic apatites and implications for paleoenvironmental reconstructions  

Microsoft Academic Search

Fossil biogenic apatites display rare-earth element (REE) patterns which have been proposed to reflect environmental and biological controls on past seawater composition. These patterns can be separated in two groups: (1) patterns that are similar to those of open ocean and epicontinental waters and (2) patterns that exhibit a strong enrichment in intermediate REE (bell-shaped patterns). Because REE trapping in

Bruno Reynard; Christophe Lécuyer; Patricia Grandjean

1999-01-01

332

Nondestructive neutron activation analysis of rare earth elements in hot spring water samples in Kusatsu-shirane area, Japan  

Microsoft Academic Search

Hot spring water samples have been analyzed for their rare earth elements (REE's) determination by the nondestructive neutron activation method. Five REE's, La, Ce, Sm, Eu and Yb, have consequently been detected and determined with satisfactory precision. The method has been found to be simple and suited for the simultaneous analyses of several samples. To determine all the REE's, however,

T. Honda; T. Nozaki; T. Ossaka; T. Oi; H. Kakihana

1988-01-01

333

Geochemical Studies of Rare Earth Elements in the Portuguese Pyrite Belt, and Geologic and Geochemical Controls on Gold Distribution.  

National Technical Information Service (NTIS)

Geochemical and geologic studies were conducted by the U.S. Geological Survey and the Servicos Geologicos de Portugal in the Portuguese Pyrite Belt in southern Portugal during 1987 and 1988. The studies included (1) rare earth element distributions, (2) t...

D. J. Grimes R. L. Earhart D. de Carvalho V. Oliveira J. T. Oliveira

1998-01-01

334

Ligand extraction of rare earth elements from aquifer sediments: Implications for rare earth element complexation with organic matter in natural waters  

NASA Astrophysics Data System (ADS)

The ability of organic matter as well as carbonate ions to extract rare earth elements (REEs) from sandy sediments of a Coastal Plain aquifer was investigated for unpurified organic matter from different sources (i.e., Mississippi River natural organic matter, Aldrich humic acid, Nordic aquatic fulvic acid, Suwannee River fulvic acid, and Suwannee River natural organic matter) and for extraction solutions containing weak (i.e., CH 3COO -) or strong (i.e., CO32-) ligands. The experimental results indicate that, in the absence of strong REE complexing ligands in solution, the amount of REEs released from the sand is small and the fractionation pattern of the released REEs appears to be controlled by the surface stability constants for REE sorption with Fe(III) oxides/oxyhydroxides. In the presence of strong solution complexing ligands, however, the amount and the fractionation pattern of the released REEs reflect the strength and variation of the stability constants of the dominant aqueous REE species across the REE series. The varying amount of REEs extracted by the different organic matter employed in the experiments indicates that organic matter from different sources has different complexing capacity for REEs. However, the fractionation pattern of REEs extracted by the various organic matter used in our experiments is remarkable consistent, being independent of the source and the concentration of organic matter used, as well as solution pH. Because natural aquifer sand and unpurified organic matter were used in our experiments, our experimental conditions are more broadly similar to natural systems than many previous laboratory experiments of REE-humic complexation that employed purified humic substances. Our results suggest that the REE loading effect on REE-humic complexation is negligible in natural waters as more abundant metal cations (e.g., Fe, Al) out-compete REEs for strong binding sites on organic matter. More specifically, our results indicate that REE complexation with organic matter in natural waters is dominated by REE binding to weak sites on dissolved organic matter, which subsequently leads to a middle REE (MREE: Sm-Ho)-enriched fractionation pattern. The experiments also indicate that carbonate ions may effectively compete with fulvic acid in binding with dissolved REEs, but cannot out compete humic acids for REEs. Therefore, in natural waters where low molecular weight (LMW) dissolved organic carbon (DOC) is the predominant form of DOC (e.g., lower Mississippi River water), REEs occur as "truly" dissolved species by complexing with carbonate ions as well as FA, resulting in heavy REE (HREE: Er-Lu)-enriched shale-normalized fractionation patterns. Whereas, in natural terrestrial waters where REE speciation is dominated by organic complexes with high molecular weight DOC (e.g., "colloidal" HA), only MREE-enriched fractionation patterns will be observed because the more abundant, weak sites preferentially complex MREEs relative to HREEs and light REEs (LREEs: La-Nd).

Tang, Jianwu; Johannesson, Karen H.

2010-12-01

335

Distribution behavior of uranium, neptunium, rare-earth elements ( Y, La, Ce, Nd, Sm, Eu, Gd) and alkaline-earth metals (Sr,Ba) between molten LiCl?KCI eutectic salt and liquid cadmium or bismuth  

Microsoft Academic Search

Distribution coefficients of uranium neptunium, eight rare-earth elements (Y, La, Ce, Pr, Nd, Sm, Eu and Gd) and two alkaline-earth metals (Sr and Ba) between molten LiCl-KCI eutectic salt and either liquid cadmium or bismuth were measured at 773 K. Separation factors of trivalent rare-earth elements to uranium or neptunium in the LiCl-KCl\\/Bi system were by one or two orders

M. Kurata; Y. Sakamura; T. Hijikata; K. Kinoshita

1995-01-01

336

Rare-earth elements enrichment of Pacific seafloor sediments: the view from volcanic islands of Polynesia  

NASA Astrophysics Data System (ADS)

Rare-earth elements (REEs) are key metals for «green» technologies such as energy saving lamps or permanent magnets used in, e.g., wind turbines, hard disk drives, portable phone or electric or hybrid vehicles. Since several years, world demand for these metals is therefore drastically increasing. The quasi-monopolistic position of China, which produces around 95 % of global REEs production, generates risks for the industries that depend on a secure supply of REEs. In response, countries are developing and diversifying their supply sources, with new mining projects located outside China and efforts in the area of REEs recycling. Most of these projects focus on deposits related to carbonatites and alkaline-peralkaline magmatism, which are generally enriched in light REEs (LREEs) compared to the heavy REEs (HREEs)-enriched deposits of the ion-adsorption types, located in southern China. However, a recent study revealed new valuable resources corresponding to seafloor sediments located in the south-eastern and north-central Pacific. The deep-sea mud described by these authors show a higher HREE/LREE ratio than ion-adsorption deposits, a feature which significantly increases their economic interest. The authors suggest mid-ocean ridge hydrothermal activity as an explanation to this anomalous enrichment. However, several contributions have documented considerable REEs enrichment in basalts and peridotitic xenoliths from French Polynesia. Several arguments have been exposed in favour of a supergene origin, with a short migration, suggesting that REEs were collected from weathered basalts. The Tahaa volcanic island (Sous-le-Vent Island, Society Archipelago, French Polynesia) is the first location where such enrichment has been described. New petrographic and mineralogical investigations confirm a supergene mobilization of this abnormal occurrence. REE-bearing minerals (mainly phosphates of the rhabdophane group) are primarily located within basalt vesicles but also in crack that cross-cut the calcite filling the vesicles or the volcanic glass. They are also closely associated with Ni-Mg bearing phyllosilicates, which appear to nucleate from alteration of olivine and clinopyroxenes. Further investigations are done to evidence and confirm an anterior magmatic enrichment. On the basis of these observations, we believe that the anomalous enrichment observed in seafloor sediments could derive from abnormally-rich provinces corresponding to aerial basaltic formations from oceanic islands primarily enriched during weathering processes (Melleton et al., 2014). Melleton et al. (2014). Rare-earth elements enrichment of Pacific sea-floor sediments: the view from volcanic islands of Polynesia. In preparation.

Melleton, Jérémie; Tuduri, Johann; Pourret, Olivier; Bailly, Laurent; Gisbert, Thierry

2014-05-01

337

Efficient mobilization and fractionation of rare-earth elements by aqueous fluids upon slab dehydration  

NASA Astrophysics Data System (ADS)

The characteristic REE fractionation pattern in arc magmas compared to MOR-basalts results from the selective mobilization of light rare-earth elements (LREE) by slab-derived mobile components. However, the nature and composition of the slab flux, and the actual mechanisms responsible for the transfer of rare-earth elements (REE) from the slab to the mantle wedge remain unclear. We present experimental data on the solubility of selected REE in ligand-bearing aqueous fluids and a hydrous haplogranitic melt at 2.6 GPa and 600-800 °C, spanning the conditions relevant to slab dehydration and melting. The solubilities of REE in aqueous fluids increase more than an order of magnitude with temperature increasing from 600 to 800 °C. Addition of ligands such as Cl-, F-, CO32-, SO42- in relatively small concentrations (0.3-1.5 m [mol/kg H2O]) has a pronounced effect further enhancing REE solubilities. Each ligand yields a characteristic REE pattern by preferential dissolution of either the light or the heavy REE. For example, the addition of NaCl to the aqueous fluids yields highly elevated LREE/HREE ratios (La/Yb=17.4±4.3), whereas the addition of fluoride and sulfate ligands significantly increases the solubility of all REE with moderate LREE/HREE fractionation (La/Yb?4). The addition of Na2CO3 results in preferential increase of HREE solubilities, and yields La/Yb ratio of 1.6±0.5 by flattening the moderately fractionated REE pattern seen in pure aqueous fluids. The solubilities in hydrous haplogranite melt are moderate in comparison to those observed in aqueous fluids and do not lead to pronounced REE fractionation. Therefore, REE can be effectively mobilized and fractionated by aqueous fluids, compared to felsic hydrous melts. Furthermore, the aqueous fluid chemistry has a major role in determining REE mobilities and fractionation upon slab dehydration in addition to the significant control exerted by temperature. Our results show that chloride-bearing slab-derived aqueous fluids have a significant contribution to the formation of REE-signatures in arc-magmas, especially at lower slab surface temperatures.

Tsay, A.; Zajacz, Z.; Sanchez-Valle, C.

2014-07-01

338

Rare earth elements in the phosphatic-enriched sediment of the Peru shelf  

USGS Publications Warehouse

Apatite-enriched materials from the Peru shelf have been analyzed for their major oxide and rare earth element (REE) concentrations. The samples consist of (1) the fine fraction of sediment, mostly clay material, (2) phosphatic pellets and fish debris, which are dispersed throughout the fine-grained sediment, (3) tabular-shaped phosphatic crusts, which occur within the uppermost few centimeters of sediment, and (4) phosphatic nodules, which occur on the seafloor. The bulk REE concentrations of the concretions suggest that these elements are partitioned between the enclosed detrital material and the apatite fraction. Analysis of the fine-grained sediment with which the samples are associated suggested that this detrital fraction in the concretions should have shale REE values; the analysis of the fish debris suggested that the apatite fraction might have seawater values. The seawater contribution of REE's is negligible in the nodules and crust, in which the apatite occurs as a fine-grained interstitial cement. That is, the concentration of REE's and the REE patterns are predominantly a function of the amount of enclosed fine-grained sediment. By contrast, the REE pattern of the pelletal apatite suggests a seawater source and the absolute REE concentrations are relatively high. The REE P2O5 ratios of the apatite fraction of these samples thus vary from approximately zero (in the case of the crust and nodules) to as much as approximately 1.2 ?? 10-3 (in the case of the pellets). The range of this ratio suggests that rather subtle variations in the depositional environment might cause a significant variation in the REE content of this authigenic fraction of the sediment. Pelletal glauconite was also recovered from one sediment core. Its REE concentrations closely resemble those of the fish debris. ?? 1988.

Piper, D. Z.; Baedecker, P. A.; Crock, J. G.; Burnett, W. C.; Loebner, B. J.

1988-01-01

339

Yttrium and rare earth elements in fluids from various deep-sea hydrothermal systems  

NASA Astrophysics Data System (ADS)

Rare earth element (REE) and yttrium (Y) concentrations were measured in fluids collected from deep-sea hydrothermal systems including the Mid-Atlantic Ridge (MAR), i.e., Menez Gwen, Lucky Strike, TAG, and Snakepit; the East Pacific Rise (EPR), i.e., 13°N and 17-19°S; and the Lau (Vai Lili) and Manus (Vienna Woods, PacManus, Desmos) Back-Arc Basins (BAB) in the South-West Pacific. In most fluids, Y is trivalent and behaves like Ho. Chondrite normalized Y-REE (Y-REE N) concentrations of fluids from MAR, EPR, and two BAB sites, i.e., Vai Lili and Vienna Woods, showed common patterns with LREE enrichment and positive Eu anomalies. REE analysis of plagioclase collected at Lucky Strike strengthens the idea that fluid REE contents, are controlled by plagioclase phenocrysts. Other processes, however, such as REE complexation by ligands (Cl -, F - SO 42-), secondary phase precipitation, and phase separation modify REE distributions in deep-sea hydrothermal fluids. REE speciation calculations suggest that aqueous REE are mainly complexed by Cl - ions in hot acidic fluids from deep-sea hydrothermal systems. REE concentrations in the fluid phases are, therefore, influenced by temperature, pH, and duration of rock-fluid interaction. Unusual Y-REE N patterns found in the PacManus fluids are characterized by depleted LREE and a positive Eu anomaly. The Demos fluid sample shows a flat Y-REE N pattern, which increases regularly from LREE to HREE with no Eu anomaly. These Manus Basin fluids also have an unusual major element chemistry with relatively high Mg, SO 4, H 2S, and F contents, which may be due to the incorporation of magmatic fluids into heated seawater during hydrothermal circulation. REE distribution in PacManus fluids may stem from a subseafloor barite precipitation and the REE in Demos fluids are likely influenced by the presence of sulfate ions.

Douville, Eric; Bienvenu, Philippe; Charlou, Jean Luc; Donval, Jean Pierre; Fouquet, Yves; Appriou, Pierre; Gamo, Toshitaka

1999-03-01

340

Microdistributions and petrogenetic implications of rare earth elements in polymict ureilites  

NASA Astrophysics Data System (ADS)

Polymict ureilites contain various mineral and lithic clasts not observed in monomict ureilites, including plagioclase, enstatite, feldspathic melt clasts and dark inclusions. This paper investigates the microdistributions and petrogenetic implications of rare earth elements (REEs) in three polymict ureilites (Elephant Moraine (EET) 83309, EET 87720 and North Haig), focusing particularly on the mineral and lithic clasts not found in monomict ureilites. As in monomict ureilites, olivine and pyroxene are the major heavy (H)REE carriers in polymict ureilites. They have light (L)REE-depleted patterns with little variation in REE abundances, despite large differences in major element compositions. The textural and REE characteristics of feldspathic melt clasts in the three polymict ureilites indicate that they are most likely shocked melt that sampled the basaltic components associated with ureilites on their parent body. Simple REE modeling shows that the most common melt clasts in polymict ureilites can be produced by 20-30% partial melting of chondritic material, leaving behind a ureilitic residue. The plagioclase clasts, as well as some of the high-Ca pyroxene grains, probably represent plagioclase-pyroxene rock types on the ureilite parent body. However, the variety of REE patterns in both plagioclase and melt clasts cannot be the result of a single igneous differentiation event. Multiple processes, probably including shock melting and different sources, are required to account for all the REE characteristics observed in lithic and mineral clasts. The C-rich matrix in polymict ureilites is LREE-enriched, like that in monomict ureilites. The occurrence of Ce anomalies in C-rich matrix, dark inclusions and the presence of the hydration product, iddingsite, imply significant terrestrial weathering. A search for 26Mg excesses, from the radioactive decay of 26Al, in the polymict ureilite EET 83309 was negative.

Guan, Yunbin; Crozaz, Ghislaine

2001-08-01

341

Marine geochemistry  

NASA Astrophysics Data System (ADS)

During the last 4 years (January 1967 through December 1970) several major trends in marine geo-chemical studies in the United States can be noted, These are: (1) the intercalibration of radioactive, ‘chemical,’ and magnetic dating techniques in deep-sea sediments; (2) the improvement in the understanding of the major chemical controls on the composition of sea water and sediments derived from them including the carbon dioxide-calcium carbonate system; (3) the more refined application of uranium and thorium decay series nuclides to ocean circulation problems; (4) the improvement of the reliability of trace element analyses on natural waters including sea water, pore waters, and streams; and (5) the study of sources and chemical properties of detrital deep-sea deposits using isotopic, mineralogic, and chemical data.

Turekian, Karl K.

342

Oxidation Resistance of Fe80Cr20 Alloys Treated by Rare Earth Element Ion Implantation  

NASA Astrophysics Data System (ADS)

The oxidation behaviour of newly developed process of Fe80Cr20 alloy was studied as a function of temperature in the range 1173-1273 K for up to 100 h in flowing air, which corresponds to the Solid Oxide Fuel Cell (SOFC) environment operating conditions. The effects of rare earth element implantation and depth profile on the oxidation behaviour of specimens were analyzed based on oxide morphology and microstructure. Characterisation of the oxide phase products after oxidation was made by X-ray diffraction (XRD). The surface morphology of oxide scales was examined using the scanning electronic microscope (SEM) with energy-dispersive X-ray analysis (EDX). The rate constant of thermal oxidation was determined using Wagner method. Experimental results show that the specimens implanted with lanthanum have remarkably enhanced the oxidation resistance. The oxidation test indicates that the newly developed process of Fe80Cr20 implantation with lanthanum ions exhibit considerably greater improvement in the oxidation resistance compared to the specimens implanted with titanium. The newly developed process of Fe80Cr20 milled for 60h show better oxidation resistance compared to specimens milled for 40h.

Sebayang, Darwin; Khaerudini, Deni S.; Saryanto, H.; Hasan, Sulaiman; Othman, M. A.; Untoro, Puji

2011-10-01

343

Competition between humic acid and carbonates for rare earth elements complexation.  

PubMed

The competitive binding of rare earth elements (REE) to humic acid (HA) and carbonates was studied experimentally at various pH and alkalinity values by combining ultrafiltration and inductively coupled plasma mass spectrometry techniques. The results show that the REE species occur as binary humate or carbonate complexes but not as ternary REE-carbonate-humate as previously proposed. The results also reveal the strong pH and alkalinity dependence of the competition as well as the existence of a systematic fractionation across the REE series. Specifically, carbonate complexation is at a maximum at pH 10 and increase with increasing alkalinity and with the atomic number of the REE (LuCO(3)>LaCO(3)). Modeling of the data using Model VI and recently published stability constants for complexation of REE by humic acid well reproduced the experimental data, confirming the ability of Model VI to accurately determine REE speciation in natural waters. This modeling also confirms the reliability of recently published stability constants. This work shed more light not only on the competition between carbonates and HA for REE complexation but also on the reliability of WHAM 6 and Model VI for calculating the speciation of REE with organic matter in alkaline organic-rich water. PMID:17052726

Pourret, Olivier; Davranche, Mélanie; Gruau, Gérard; Dia, Aline

2007-01-01

344

On the non-uniform distribution of the angular elements of near-Earth objects  

NASA Astrophysics Data System (ADS)

We examine the angular distributions of near-Earth objects (NEOs) which are often regarded as uniform. The apparent distribution of the longitude of ascending node, ?, is strongly affected by well-known seasonal effects in the discovery rate of NEOs. The deviation from the expected ?-periodicity in the apparent distribution of ? indicates that its intrinsic distribution is slightly enhanced along a mean direction, ??=111°; approximately 53% of NEOs have ? values within ±90° of ??. We also find that each subgroup of NEOs (Amors, Apollos and Atens) has different observational selection effects which cause different non-uniformities in the apparent distributions of their arguments of perihelion ?, and longitudes of perihelion ?. For their intrinsic distributions, our analysis reveals that the Apollo asteroids have non-uniform ? due to secular dynamics associated with inclination-eccentricity-? coupling, and the Amors' ? distribution is peaked towards the secularly forced eccentricity vector. The Apollos' ? distribution is axial, favoring values near 0° and 180°; the two quadrants centered at 0° and 180° account for 55% of the Apollos' ? values. The Amors' ? distribution peaks near ??=4°; 61% of Amors have ? within ±90° of this peak. We show that these modest but statistically significant deviations from uniform random distributions of angular elements are owed to planetary perturbations, primarily Jupiter's. It is remarkable that this strongly chaotic population of minor planets reveals the presence of Jupiter in its angular distributions.

JeongAhn, Youngmin; Malhotra, Renu

2014-02-01

345

State of rare earth elements in different environmental components in mining areas of China.  

PubMed

China has relatively abundant rare earth elements (REEs) reserves and will continue to be one of the major producers of REEs for the world market in the foreseeable future. However, due to the large scale of mining and refining activities, large amounts of REEs have been released to the surrounding environment and caused harmful effects on local residents. This paper summarizes the data about the contents and translocation of REEs in soils, waters, atmosphere, and plants in REE mining areas of China and discusses the characteristics of their forms, distribution, fractionation, and influencing factors. Obviously high concentrations of REEs with active and bioavailable forms are observed in all environmental media. The mobility and bioavailability of REEs are enhanced. The distribution patterns of REEs in soils and water bodies are all in line with their parent rocks. Significant fractionation phenomenon among individual members of REEs was found in soil-plant systems. However, limited knowledge was available for REEs in atmosphere. More studies focusing on the behavior of REEs in ambient air of REE mining areas in China are highly suggested. In addition, systematic study on the translocation and circulation of REEs in various media in REEs mining areas and their health risk assessment should be carried out. Standard analytical methods of REEs in environments need to be established, and more specific guideline values of REEs in foods should also be developed. PMID:24135922

Liang, Tao; Li, Kexin; Wang, Lingqing

2014-03-01

346

Recycling rare earth elements from industrial wastewater with flowerlike nano-Mg(OH)(2).  

PubMed

Treatment of wastewater containing low-concentration yet highly-expensive rare earth elements (REEs) is one of the vital issues in the REEs separation and refining industry. In this work, the interaction and related mechanism between self-supported flowerlike nano-Mg(OH)2 and low-concentration REEs wastewater were investigated. More than 99% REEs were successfully taken up by nano-Mg(OH)2. Further analysis revealed that the REEs could be collected on the surface of Mg(OH)2 as metal hydroxide nanoparticles (<5 nm). An ion-exchange model was proposed as a critical factor for both guaranteeing the reaction speed and maintaining the self-supported structure of the materials. In addition, a method was developed to further separate the immobilized REEs and the residual magnesium hydroxide by varying the solution pH. In a pilot-scale experiment, the REEs from practical wastewater were immobilized effectively at a high flow rate. We anticipate this work can provide a good example for the recycling of valuable REEs in practical industrial applications. PMID:24032646

Li, Chaoran; Zhuang, Zanyong; Huang, Feng; Wu, Zhicheng; Hong, Yangping; Lin, Zhang

2013-10-01

347

Gupta potential for rare earth elements of the fcc phase: lanthanum and cerium  

NASA Astrophysics Data System (ADS)

The potential parameters for a Gupta-type many-body potential are fitted for the first two rare earth elements, La and Ce. The experimental cohesive energies, lattice parameters and elastic constants of ?-La and ?-Ce solids of the face-centered cubic (fcc) phase are well reproduced. The theoretical P-V curves, sound velocities and Debye temperatures of ?-La and ?-Ce solids are in reasonable agreement with experimental data. The vacancy formation energies and surface energies are also predicted. In particular, the phonon dispersion relationship and vibrational frequencies at high symmetric points within the first Brillouin zone from our potential are consistent with experimental ones. Molecular dynamics simulation are performed to determine the melting temperature of La and Ce solids as well as the radial distribution function of liquid La, which are also in line with experimental data. All these agreements indicate the validity of the current set of potential parameters. Thus, the Gupta potential developed here would be useful in future simulation of La, Ce solids and their alloys.

Fu, Jie; Zhao, Jijun

2013-09-01

348

Modeling of rare-earth element partitioning between particles and solution in aquatic environments  

SciTech Connect

The authors have modeled the partitioning of rare earth elements (REEs) between O-donor surface groups and aqueous solutions with a simple thermodynamic treatment. Their model predicts that the La-normalized ratios of adsorbed to dissolved REEs depend primarily on the first hydroxide binding contants of the REEs, their first and second carbonate complexing constants, and the ionic strength and carbonate concentration of the solution. For modern and for ancient seawater, they predict an overall light REE (LREE) enrichment of surfaces relative to coexisting aqueous solutions and a positive Eu anomaly in the adsorbed component. The REE pattern of average modern ocean water can be explained quantitatively if the oceans are equilibrated with particle surfaces having REE patterns similar to average upper continental crust. Applying their treatment to the REE patterns of sediments from the Archean Hamersley-basin iron formation, they show that the observed positive Eu anomalies and LREE depletions of these rocks can be qualitatively accounted for if a significant fraction of the REEs in these rocks were initially present as an adsorbed component equilibrated with Archean ocean water that had no Eu anomaly. This suggests that the sources of REEs in the Archean ocean could have been dominantly continental as they are today and that the observed positive Eu anomalies of banded iron formations need not be inherited from the aqueous solutions from which they were deposited and do not necessarily indicate a significant ocean hydrothermal component in these solutions. 42 refs., 3 figs.

Erel, Y.; Stolper, E.M. (California Inst. of Technology, Pasadena (United States))

1993-02-01

349

[Research on the cytotoxic and genotoxic effects of rare-earth element holmium to Vicia faba].  

PubMed

Crystal of nitrate, made by the reaction of holmium trioxide and nitric acid, was dissolved in distilled water, thus diluted into gradient solution. Soaked in the solution for 6 hours (6h), the root tips of Vicia faba were then recovered and cultivated for 22 h and 24 h, respectively. By observing the change of root tips and calculating the frequency of micronucleus (FMN), the frequency of chromosomal aberrations(CAF) and mitosis index (MI),we find that the dosage below 4mg/L (expressed by concentration of holmium trioxide) could accelerate the growth of root tips of Vicia faba. CAF and FMN increased while MI decreased with the rise of concentrations. From it a dosage effect relationship is clearly seen. And it indicated that the rare earth element holmium has certain cytotoxic and genotoxic effects. Furthermore, the different recovery groups have different FMN, CAF and MI, and the difference lies in the fact that FMN of 22 h recovery group was lower than that of 24 h recovery group, while CAF and MI were higher than those of 24 h recovery group. The results suggest that the statistics of FMN should be made after that of CAF. PMID:15639987

Qu, Ai; Wang, Cheng-Run; Bo, Jun

2004-03-01

350

Composition and evolution of the eucrite parent body - Evidence from rare earth elements. [extraterrestrial basaltic melts  

NASA Technical Reports Server (NTRS)

Quantitative modeling of the evolution of rare earth element (REE) abundances in the eucrites, which are plagioclase-pigeonite basalt achondrites, indicates that the main group of eucrites (e.g., Juvinas) might have been produced by approximately 10% equilibrium partial melting of a single type of source region with initial REE abundances which were chondritic relative and absolute. Since the age of the eucrites is about equal to that of the solar system, extensive chemical differentiation of the eucrite parent body prior to the formation of eucrites seems unlikely. If homogeneous accretion is assumed, the bulk composition of the eucrite parent body can be estimated; two estimates are provided, representing different hypotheses as to the ratio of metal to olivine in the parent body. Since a large number of differentiated olivine meteorites, which would represent material from the interior of the parent body, have not been detected, the eucrite parent body is thought to be intact. It is suggested that the asteroid 4 Vesta is the eucrite parent body.

Consolmagno, G. J.; Drake, M. J.

1977-01-01

351

Elements of a new Global Water Strategy for the Group on Earth Observations  

NASA Astrophysics Data System (ADS)

In order to address the need to review the scope and direction of GEO activities related to water and to provide guidance for the post-2015 GEO planning, the Integrated Global Water Cycle Observations (IGWCO) Community of Practice and the Committee on Earth Observation Satellites (CEOS) are working together to develop a strategy for GEO water activities over the next decade. This presentation will review the elements of the strategy which include topics as comprehensive as user needs and engagement, water cycle observational systems, assessment of water quality, data issues, interoperability and integration of water information systems and capacity building. Impediments in the flow of information and technological capabilities from the providers of new technologies, innovations and data products to the end users will be explored in terms of the nature of these impediments and how they can be overcome. To be successful in GEO's framework of volunteerism, the water strategy should build on activities that are on-going in related programmes at the international and national levels. In addition, implementation of the strategy will need to be supported through new initiatives and policies that promote greater integration. Suggestions for achieving these goals will be outlined at the end of the talk.

Lawford, Richard; Koike, Toshio; Ochiai, Osamu; Cripe, Douglas

2013-04-01

352

New fission fragment distributions and r-process origin of the rare-earth elements.  

PubMed

Neutron star (NS) merger ejecta offer a viable site for the production of heavy r-process elements with nuclear mass numbers A?140. The crucial role of fission recycling is responsible for the robustness of this site against many astrophysical uncertainties, but calculations sensitively depend on nuclear physics. In particular, the fission fragment yields determine the creation of 110?A?170 nuclei. Here, we apply a new scission-point model, called SPY, to derive the fission fragment distribution (FFD) of all relevant neutron-rich, fissioning nuclei. The model predicts a doubly asymmetric FFD in the abundant A?278 mass region that is responsible for the final recycling of the fissioning material. Using ejecta conditions based on relativistic NS merger calculations, we show that this specific FFD leads to a production of the A?165 rare-earth peak that is nicely compatible with the abundance patterns in the Sun and metal-poor stars. This new finding further strengthens the case of NS mergers as possible dominant origin of r nuclei with A?140. PMID:24483647

Goriely, S; Sida, J-L; Lemaître, J-F; Panebianco, S; Dubray, N; Hilaire, S; Bauswein, A; Janka, H-T

2013-12-13

353

Influence of different bentonites on the rare earth element concentrations of clarified Romanian wines.  

PubMed

The rare earth element (REE) concentrations of 19 Romanian young wine samples originating from the Dealurile Moldovei viticulture area were determined by double focusing inductively coupled plasma mass spectrometry (DF-ICP-MS) after microwave-assisted digestion with nitric acid. The determination of Eu was hampered by the BaO molecular interference. Generally, the red wine samples were more concentrated for REEs than the white wine samples studied. The REE concentrations of the four bentonites (Gelbenton, Evergel, BW200, Tükrös) determined after their fusion were higher by three orders of magnitude than those of the wine samples. After a simulated wine purification process performed with these bentonite samples and a red and white pool samples, the REE concentrations of the clarified wine samples increased by 1.2-1.5 times for red, and 1.3-3 times for white wines in case of the fibrous bentonite sample (Gelbenton), by about 2-5 times in case of the bentonite containing ovalbumin, caseine and gelatine (Evergel), meanwhile this factor was about 20-25 for Na bentonite powder samples (BW200, Tükrös). On basis of the chemometric evaluation using the REE concentrations as input data, the majority of the Feteasca wines belonged to the same cluster as well as the two Cabernet Sauvignon to another subcluster. The adequate choice of the bentonite may allow the use of REEs as fingerprints for determining the wine provenance. PMID:18970871

Mihucz, Victor G; Done, Carla J; Tatár, Eniko; Virág, István; Záray, Gyula; Baiulescu, Emil G

2006-12-15

354

LiYF4 (YLF) single crystals doped with rare-earth elements  

NASA Astrophysics Data System (ADS)

LiYF4 (YLF) is a very promising host material for lasers. Investigation of the spectroscopic and physical properties of YLF:Nd has suggested that this material may be a better candidate than Nd:YAG for generating short pulses with high peak power. This is a distinct advantage for many applications. Stimulated emission is attained at 1053 nm and 1047 nm. Also upconservation laser action in YLF and YLF:Er crystals is reported. More recently YLF doped with rare-earth elements has gained some attention. Pulsed room-temperature laser action at 2.06 micrometer has been achieved using YLF:Ho sensitized with Er and Tm. Using YLF:Pr blue light emission at 479 nm at room temperature was observed. Growth experiments of YLF:Nd crystals were carried by the Bridgman method. A vacuum furnace with cylindrical molybdenum heater and graphite crucible have been used. The temperature gradient of 25 degrees Celsius/cm has been achieved by using a stainless steel liner in the lower part of the furnace. The growth was performed in a nitrogen atmosphere. First crystals of YLF:Nd have been obtained.

Kowalczyk, E.; Kowalczyk, Z.; Grasza, K.; Gala, M.; Lukasiewicz, Tadeusz

1995-10-01

355

Rare earth element sorption onto hydrous manganese oxide: a modeling study.  

PubMed

Manganese oxides are important scavengers of rare earth elements (REE) in hydrosystems. However, it has been difficult to include Mn oxides in speciation models due to the lack of a comprehensive set of sorption reactions consistent with a given surface complexation model (SCM), as well as discrepancies between published sorption data and predictions using the available models. Surface complexation reactions for hydrous Mn oxide were described using a two surface site model and the diffuse double layer SCM. The specific surface area, surface side density, and pH(zpc) were fixed to 746 m2/g, 2.1 mmol/g, and 2.2, respectively. Two site types (?XOH and ?YOH) were also used with pK(a2) values of 2.35 (?XOH) and 6.06 (?YOH). The fraction of the high affinity sites was fixed at 0.36. Published REE sorption data were subsequently used to determine the equilibrium surface complexation constants, while considering the influence of pH, ionic strength, and metal loading. LogK increases from light REE to heavy REE and, more specifically, displays a convex tetrad effect. At low metal loading, the ?YOH site type strongly expresses its affinity toward REE, whereas at higher metal loading, the same is true for the ?XOH site type. This study thus provides evidence for heterogeneity in the distribution of the Mn oxide binding sites among REE. PMID:23266025

Pourret, Olivier; Davranche, Mélanie

2013-04-01

356

Determination of the rare-earth elements in geological materials by inductively coupled plasma mass spectrometry  

USGS Publications Warehouse

A method of analysis of geological materials for the determination of the rare-earth elements using the Inductively coupled plasma mass spectrometric technique (ICP-MS) has been developed. Instrumental parameters and factors affecting analytical results have been first studied and then optimized. Samples are analyzed directly following an acid digestion, without the need for separation or preconcentration with limits of detection of 2-11 ng/g, precision of ?? 2.5% relative standard deviation, and accuracy comparable to inductively coupled plasma emission spectrometry and instrumental neutron activation analysis. A commercially available ICP-MS instrument is used with modifications to the sample introduction system, torch, and sampler orifice to reduce the effects of high salt content of sample solutions prepared from geologic materials. Corrections for isobaric interferences from oxide ions and other diatomic and triatomic ions are made mathematically. Special internal standard procedures are used to compensate for drift in metahmetal oxide ratios and sensitivity. Reference standard values are used to verify the accuracy and utility of the method.

Lichte, F. E.; Meier, A. L.; Crock, J. G.

1987-01-01

357

Rare earth elements in the water column of Lake Vanda, McMurdo Dry Valleys, Antarctica  

NASA Astrophysics Data System (ADS)

We present data on the composition of water from Lake Vanda, Antarctica. Vanda and other lakes in the McMurdo Dry Valleys of Antarctica are characterized by closed basins, permanent ice covers, and deep saline waters. The meromictic lakes provide model systems for the study of trace metal cycling owing to their pristine nature and the relative simplicity of their biogeochemical systems. Lake Vanda, in the Wright Valley, is supplied by a single input, the Onyx River, and has no output. Water input to the lake is balanced by sublimation of the nearly permanent ice cap that is broken only near the shoreline during the austral summer. The water column is characterized by an inverse thermal stratification of anoxic warm hypersaline water underlying cold oxic freshwater. Water collected under trace-element clean conditions was analyzed for its dissolved and total rare earth element (REE) concentrations by inductively coupled plasma mass spectrometry. Depth profiles are characterized by low dissolved REE concentrations (La, Ce, <15 pM) in surface waters that increase slightly (La, 70 pM; Ce, 20 pM) with increasing depth to ˜55 m, the limit of the fresh oxic waters. Below this depth, a sharp increase in the concentrations of strictly trivalent REE (e.g., La, 5 nM) is observed, and a submaximum in redox sensitive Ce (2.6 nM) is found at 60- to 62-m depth. At a slightly deeper depth, a sharper Ce maximum is observed with concentrations exceeding 11 nM at a 67-m depth, immediately above the anoxic zone. The aquatic concentrations of REE reported here are ˜50-fold higher than previously reported for marine oxic/anoxic boundaries and are, to our knowledge, the highest ever observed at natural oxic/anoxic interfaces. REE maxima occur within stable and warm saline waters. All REE concentrations decrease sharply in the sulfidic bottom waters. The redox-cline in Lake Vanda is dominated by diffusional processes and vertical transport of dissolved species driven by concentration gradients. Furthermore, because the ultraoligotrophic nature of the lake limits the potential for organic phases to act as metal carriers, metal oxide coatings and sulfide phases appear to largely govern the distribution of trace elements. We discuss REE cycling in relation to the roles of redox reactions and competitive scavenging onto Mn- and Fe-oxides coatings on clay sized particles in the upper oxic water column and their release by reductive dissolution near the anoxic/oxic interface.

De Carlo, Eric Heinen; Green, William J.

2002-04-01

358

Evaporation thermodynamics of monotellurides of selected rare Earth and alkaline Earth elements, and an attempt to systematic correlation between the standard enthalpies of formation  

NASA Astrophysics Data System (ADS)

A contribution was made to improve the knowledge of the thermochemical characteristics of monotellurides (especially the binary lanthanoide monotelluride) by the determination of the enthalpies of formation, as well as to improve the production and analysis method of these compounds. The fundamentals for the thermodynamical quantities determination of rare earth and alkaline earth elements are reviewed. The determination of the evaporation thermodynamical quantities and the enthalpy of formation of CaTe, SrTe, BaTe, SmTe, YbTe and TmTe 1,30 is outlined. The measurement and thermodynamical interpretation of the dissociation pressure as well as the determination of standard enthalpy of formation using the Knudsen effusion method are presented. The experimentally obtained enthalpies of formation are compared with thermodynamical data calculated from refined, prediction methods.

Ludwigs, Johannes

359

Genetic implications of minor-element and Sr-isotope geochemistry of alkaline rock complexes in the Wet Mountains area, Fremont and Custer counties, Colorado  

USGS Publications Warehouse

Concentrations of Rb, Sr, and REE (rare earth elements), and Sr-isotopic ratios in rocks of the Cambrian alkaline complexes in the Wet Mountains area, Colorado, show that rocks formed as end-products of a variety of magmas generated from different source materials. The complexes generally contain a bimodal suite of cumulus mafic-ultramafic rocks and younger leucocratic rocks that include nepheline syenite and hornblende-biotite syenite in the McClure Mountain Complex, nepheline syenite pegmatite in the Gem Park Complex, and quartz syenite in the complex at Democrat Creek. The nepheline syenite and hornblende-biotite syenite at McClure Mountain (535??5m.y.) are older than the syenitic rocks at Democrat Creek (511??8m.y.). REE concentrations indicate that the nepheline syenite at McClure Mountain cannot be derived from the hornblende-biotite syenite, which it intrudes, or from the associated mafic-ultramafic rocks. REE also indicate that mafic-ultramafic rocks at McClure Mountain have a source distinct from that of the mafic-ultramafic rocks at Democrat Creek. In the McClure Mountain Complex, initial87Sr/86Sr ratios for mafic-ultramafic rocks (0.7046??0.0002) are similar to those of hornblende-biotite syenite (0.7045??0.0002), suggesting a similar magmatic source, whereas ratios for carbonatites (0.7038??0.0002) are similar to those of nepheline syenite (0.7038??0.0002). At Democrat Creek, initial ratios of syenitic rocks (0.7032??0.0002) and mafic-ultramafic rocks (0.7028??0.0002) are different from those of corresponding rocks at McClure Mountain. ?? 1982 Springer-Verlag.

Armbrustmacher, T. J.; Hedge, C. E.

1982-01-01

360

Not So Rare Earth? New Developments in Understanding the Origin of the Earth and Moon  

NASA Technical Reports Server (NTRS)

A widely accepted model for the origin of the Earth and Moon has been a somewhat specific giant impact scenario involving an impactor to proto-Earth mass ratio of 3:7, occurring 50-60 Ma after T(sub 0), when the Earth was only half accreted, with the majority of Earth's water then accreted after the main stage of growth, perhaps from comets. There have been many changes to this specific scenario, due to advances in isotopic and trace element geochemistry, more detailed, improved, and realistic giant impact and terrestrial planet accretion modeling, and consideration of terrestrial water sources other than high D/H comets. The current scenario is that the Earth accreted faster and differentiated quickly, the Moon-forming impact could have been mid to late in the accretion process, and water may have been present during accretion. These new developments have broadened the range of conditions required to make an Earth-Moon system, and suggests there may be many new fruitful avenues of research. There are also some classic and unresolved problems such as the significance of the identical O isotopic composition of the Earth and Moon, the depletion of volatiles on the lunar mantle relative to Earth's, the relative contribution of the impactor and proto-Earth to the Moon's mass, and the timing of Earth's possible atmospheric loss relative to the giant impact.

Righter, Kevin

2007-01-01

361

Geochemistry all around us  

NSDL National Science Digital Library

This activity is actually a series of labs/field trip exercises I ran with my advanced geochemistry class a year ago. For this class, we went on a number of field trips to sample a number of local waters, including, High Cliff State Park, where the Niagran Escarpment is present, a local wetland reserve, Lake Winnebago, the Fox River (downstream from Lake Winnebago), and finally a nearby cave in the dolostone of the Niagran Escarpment. We tested these waters for a few relatively straightforward properties: hardness, alkalinity, pH, and dissolved oxygen. In the future I am going to expand these analyses to include analysis on our AA, and possibly sending samples away for ICP analysis on a suite of elements. These sampling trips followed our course materials looking at the thermodynamics of mineral solubility and the interaction of water with the atmosphere. Students were able to easily recognize how these waters were different, and were able to make reasonable hypotheses to explain these differences. Furthermore, because this was the first time I had sampled these waters (this was in my first year), I didn't know the answer, so students were themselves forced to determine whether their results were reasonable or not. As an additional note, I should credit Tony Hoch, my predecessor here at LU. Much of the material I used in these labs evolved from labs he had run while at LU.

Knudsen, Andrew

362

Chemical composition of modern and fossil Hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation - Part 2: Alkaline earth elements as tracers of watershed hydrochemistry and provenance  

NASA Astrophysics Data System (ADS)

For reconstructing environmental change in terrestrial realms the geochemistry of fossil bioapatite in bones and teeth is among the most promising applications. This study demonstrates that alkaline earth elements in enamel of Hippopotamids, in particular Ba and Sr are tracers for water provenance and hydrochemistry. The studied specimens are molar teeth from Hippopotamids found in modern and fossil lacustrine settings of the Western Branch of the East African Rift system (Lake Kikorongo, Lake Albert, and Lake Malawi) and from modern fluvial environments of the Nile River. Concentrations in enamel vary by ca. two orders of magnitude for Ba (120-9336 ?g g-1) as well as for Sr (9-2150 ?g g-1). Concentration variations in enamel are partly induced during post-mortem alteration and during amelogenesis, but the major contribution originates from the variable water chemistry in the habitats of the Hippopotamids which is dominated by the lithologies and weathering processes in the watershed areas. Amelogenesis causes a distinct distribution of Ba and Sr in modern and fossil enamel, in that element concentrations increase along profiles from the outer rim towards the enamel-dentin junction by a factor of 1.3-1.5. These elements are well correlated with MgO and Na2O in single specimens, thus suggesting that their distribution is determined by a common, single process. Presuming that the shape of the tooth is established at the end of the secretion process and apatite composition is in equilibrium with the enamel fluid, the maturation process can be modeled by closed system Rayleigh crystallization. Enamel from many Hippopotamid specimens has Sr/Ca and Ba/Ca which are typical for herbivores, but the compositions extend well into the levels of plants and carnivores. Within enamel from single specimens these element ratios covary and provide a specific fingerprint of the Hippopotamid habitat. All specimens together, however, define subparallel trends with different Ba/Sr ranging from 0.1 to 3. This ratio varies on spatial and temporal scales and traces provenance signals as well as the fractionation of the elements in the hydrological cycle. Thus, Sr concentrations and Ba/Sr in enamel differentiate between habitats having basaltic or Archean crustal rocks as the ultimate sources of Sr and Ba. The provenance signal is modulated by climate change. In Miocene to Pleistocene enamel from the Lake Albert region, Ba/Sr decreases systematically with time from about 2 to 0.5. This trend can be correlated with changes in climate from humid to arid in vegetation from C3 to C4 biomass as well as with increasing evaporation of the lake water. The most plausible explanation is that with time, Ba mobility decreased relative to that of Sr. This can arise if preferential adsorption of Ba to clay and Fe-oxide-hydroxide is related to increasing aridification. Additionally, weathering solutions and lake water can become increasingly alkaline and barite becomes stable. In this case, Ba will be preferentially deposited on the watershed of Lake Albert and rivers with low Ba/Sr will feed the habitats of the Hippopotamids.

Brügmann, G.; Krause, J.; Brachert, T. C.; Stoll, B.; Weis, U.; Kullmer, O.; Ssemmanda, I.; Mertz, D. F.

2012-03-01

363

Yttrium and rare earth elements in fluids from various deep-sea hydrothermal systems  

SciTech Connect

Rare earth element (REE) and yttrium (Y) concentrations were measured in fluids collected from deep-sea hydrothermal systems including the Mid-Atlantic Ridge (MAR), i.e., Menez Gwen, Lucky Strike, TAG, and Snakepit; the East Pacific Rise (EPR), i.e., 13{degree}N and 17--19{degree}S; and the Lau (Vai Lili) and Manus (Vienna Woods, PacManus, Desmos) Back-arc Basins (BAB) in the South-West Pacific. In most fluids, Y is trivalent and behaves like Ho. Chondrite normalized Y-REE (Y-REE{sub N}) concentrations of fluids from MAR, EPR, and two BAB sites, i.e., Vai Lili and Vienna Woods, showed common patterns with LREE enrichment and positive Eu anomalies. REE analysis of plagioclase collected at Lucky Strike strengthens the idea that fluid REE contents, are controlled by plagioclase phenocrysts. Other processes, however, such as REE complexation by ligands (Cl{sup {minus}}, F{sup {minus}}, So{sub 4}{sup 2{minus}}), secondary phase precipitation, and phase separation modify REE distributions in deep-sea hydrothermal fluids. REE speciation calculations suggest that aqueous REE are mainly complexed by Cl{sup {minus}} ions in hot acidic fluids from deep-sea hydrothermal systems. REE concentrations in the fluid phases are, therefore, influenced by temperature, pH, and duration of rock-fluid interaction. Unusual Y-REE{sub N} patterns found in the PacManus fluids are characterized by depleted LREE and a positive Eu anomaly. The Demos fluid sample shows a flat Y-REE{sub N} pattern, which increases regularly from LREE to HREE with no Eu anomaly. These Manus Basin fluids also have an unusual major element chemistry with relatively high Mg, So{sub 4}, H{sub 2}S, and F contents, which may be due to the incorporation of magmatic fluids into heated seawater during hydrothermal circulation. REE distribution in PacManus fluids may stem from a subseafloor barite precipitation and the REE in Demos fluids are likely influenced by the presence of sulfate ions.

Douville, E. [Univ. Bretagne Occidentale, Brest (France). Dept. de Chimie] [Univ. Bretagne Occidentale, Brest (France). Dept. de Chimie; [IFREMER Centre de Brest, Plouzane (France); Appriou, P. [Univ. Bretagne Occidentale, Brest (France)] [Univ. Bretagne Occidentale, Brest (France); Bienvenu, P. [CEA Cadarache, Saint Paul Lez Durance (France). Lab. d`Analyses Radiochimiques et Chimiques] [CEA Cadarache, Saint Paul Lez Durance (France). Lab. d`Analyses Radiochimiques et Chimiques; Charlou, J.L.; Donval, J.P.; Fouquet, Y. [IFREMER Centre de Brest, Plouzane (France)] [IFREMER Centre de Brest, Plouzane (France); Gamo, Toshitaka [Univ. of Tokyo, Nakano, Tokyo (Japan). Ocean Research Inst.] [Univ. of Tokyo, Nakano, Tokyo (Japan). Ocean Research Inst.

1999-03-01

364

Ocean particle chemistry: The fractionation of rare earth elements between suspended particles and seawater  

SciTech Connect

Sargasso Sea suspended particles were sequentially digested with three chemical treatments (acetic acid, mild HCl/HNO[sub 3], and HF/HNO[sub 3]/HCl in a bomb). The latter two treatments dissolve detrital minerals, while the acetic acid removes surface coatings (organic matter and Mn oxides). The rare earth element (REE) composition of the surface coatings, in marked contrast to the crust-like REE composition of the two detrital phases, is extensively fractionated with respect to both filtered seawater and the crust. Surface coatings are responsible for the removal and fractionation of REEs from seawater and, as such, play a key role in the marine geochemical cycles of trace elements. Relative to seawater, the surface coatings are systematically enriched tenfold across the trivalent REEs from Lu to La and develop large positive Ce-anomalies. The Ce-anomalies of the coatings switch from being negative (seawater-like) in the upper 100 m to being strongly positive at greater depths. The ingrowth of Ce and LREEs on particle surfaces reflects the in situ oxidation of dissolved Ce(III) to particulate Ce(IV), and the preferential removal of LREE(III)s over HREE(III)s. REEs(III) fractionation of this type is consistent with particle/solution models. Both processes appear to be related to the in situ formation of Mn oxide particles from the oxidation of dissolved Mn(II) in the upper 200 m of the water column. Preferential removal of LREEs in the upper waters is countered by their preferential release at depth due to remineralization of surface coatings on particles. A new method is explored for estimating the residence time of suspended particles by combining Ce concentration data of dissolved and surface-bound phases with the Ce(III) oxidation rate measurements of MOFFETT (1990). A Ce-based residence time of thirteen days is similar in magnitude to the value calculated from U-[sup 234]Th disequilibria in the Sargasso Sea.

Sholkovitz, E.R. (Woods Hole Oceanographic Institution, Woods Hole, MA (United States)); Landing, W.M.; Lewis, B.L. (Florida State Univ., Tallahassee, FL (United States))

1994-03-01

365

Rare Earth Element Measurements of Melilite and Fassaite in Allende Cai by Nanosims  

NASA Technical Reports Server (NTRS)

The rare earth elements (REEs) are concentrated in CAIs by approx. 20 times the chondritic average [e.g., 1]. The REEs in CAIs are important to understand processes of CAI formation including the role of volatilization, condensation, and fractional crystallization [1,2]. REE measurements are a well established application of ion microprobes [e.g., 3]. However the spatial resolution of REE measurements by ion microprobe (approx.20 m) is not adequate to resolve heterogeneous distributions of REEs among/within minerals. We have developed methods for measuring REE with the NanoSIMS 50L at smaller spatial scales. Here we present our initial measurements of REEs in melilite and fassaite in an Allende Type-A CAI with the JSC NanoSIMS 50L. We found that the key parameters for accurate REE abundance measurements differ between the NanoSIMS and conventional SIMS, in particular the oxide-to-element ratios, the relative sensitivity factors, the energy distributions, and requisite energy offset. Our REE abundance measurements of the 100 ppm REE diopside glass standards yielded good reproducibility and accuracy, 0.5-2.5 % and 5-25 %, respectively. We determined abundances and spatial distributions of REEs in core and rim within single crystals of fassaite, and adjacent melilite with 5-10 m spatial resolution. The REE abundances in fassaite core and rim are 20-100 times CI abundance but show a large negative Eu anomaly, exhibiting a well-defined Group III pattern. This is consistent with previous work [4]. On the other hand, adjacent melilite shows modified Group II pattern with no strong depletions of Eu and Yb, and no Tm positive anomaly. REE abundances (2-10 x CI) were lower than that of fassaite. These patterns suggest that fassaite crystallized first followed by a crystallization of melilite from the residual melt. In future work, we will carry out a correlated study of O and Mg isotopes and REEs of the CAI in order to better understand the nature and timescales of its formation process and subsequent metamorphic history.

Ito, M.; Messenger, Scott

2009-01-01

366

PQQ-dependent methanol dehydrogenases: rare-earth elements make a difference.  

PubMed

Methanol dehydrogenase (MDH) catalyzes the first step in methanol use by methylotrophic bacteria and the second step in methane conversion by methanotrophs. Gram-negative bacteria possess an MDH with pyrroloquinoline quinone (PQQ) as its catalytic center. This MDH belongs to the broad class of eight-bladed ? propeller quinoproteins, which comprise a range of other alcohol and aldehyde dehydrogenases. A well-investigated MDH is the heterotetrameric MxaFI-MDH, which is composed of two large catalytic subunits (MxaF) and two small subunits (MxaI). MxaFI-MDHs bind calcium as a cofactor that assists PQQ in catalysis. Genomic analyses indicated the existence of another MDH distantly related to the MxaFI-MDHs. Recently, several of these so-called XoxF-MDHs have been isolated. XoxF-MDHs described thus far are homodimeric proteins lacking the small subunit and possess a rare-earth element (REE) instead of calcium. The presence of such REE may confer XoxF-MDHs a superior catalytic efficiency. Moreover, XoxF-MDHs are able to oxidize methanol to formate, rather than to formaldehyde as MxaFI-MDHs do. While structures of MxaFI- and XoxF-MDH are conserved, also regarding the binding of PQQ, the accommodation of a REE requires the presence of a specific aspartate residue near the catalytic site. XoxF-MDHs containing such REE-binding motif are abundantly present in genomes of methylotrophic and methanotrophic microorganisms and also in organisms that hitherto are not known for such lifestyle. Moreover, sequence analyses suggest that XoxF-MDHs represent only a small part of putative REE-containing quinoproteins, together covering an unexploited potential of metabolic functions. PMID:24816778

Keltjens, Jan T; Pol, Arjan; Reimann, Joachim; Op den Camp, Huub J M

2014-07-01

367

Biogeochemical implications from dissolved rare earth element and Nd isotope distributions in the Gulf of Alaska  

NASA Astrophysics Data System (ADS)

Dissolved rare earth element (REE) concentrations and Nd isotope compositions were measured for surface waters and full water column profiles of the Gulf of Alaska (GoA), and compared to water mass properties and circulation in order to better understand the mechanisms controlling the input and transport of REEs in the ocean. The REEs display a typical open-ocean range of concentrations (i.e., La: 12-66 pM; Lu: 0.2-2.5 pM) and depth distributions (i.e., surface ocean depletion and enrichment with water depth). Nd isotope signatures are highly radiogenic, as expected for the North Pacific margin (ranging from -3.8 to +0.2 ?Nd). The most radiogenic values were found in the coastal waters but also in the cores of eddies, indicating efficient export of REEs from the margins and across the mixed layer. This is the first time that distinct Nd isotope distributions in near surface waters can be directly assigned to offshore eddy transport. A distinct mid-depth (˜2200 m) Nd isotope signal was found that most likely reflects advection of a water mass that formed through past down-welling in the Northern Pacific. Subsurface Nd isotope compositions appear to behave conservatively and can be explained through a REE distribution model proposed here. This model is based on multivariate analysis of the REEs and invokes two distinct “pools” of dissolved REEs: a “passive pool” complexed by carbonate ions, and a “bio-reactive pool” that is microbially manipulated. The latter “pool” is only significant in the upper water column and most likely reflects the indirect effects of microbial cycling of iron. Our model of the open ocean REE distribution contributes to explaining the conservative nature of Nd isotopes and provides a mechanism linking surface ocean and pore water REE dynamics.

Haley, Brian A.; Frank, Martin; Hathorne, Ed; Pisias, Nick

2014-02-01

368

Preparation of rare-earth element doped Mg2Si by FAPAS  

NASA Astrophysics Data System (ADS)

Rare-earth elements (Re) Sc and Y doped Mg2Si thermoelectric materials were made via a field-activated and pressure-assisted synthesis (FAPAS) method at 1023-1073 K, 50 MPa for 15 min. The samples created using this method have uniform and compact structures. The average grain size was about 1.5-2 ?m, the micro-content of Re did not change the matrix morphology. The sample with 2500 ppm Sc obtained the best See-beck coefficient absolute value, about 1.93 times of that belonging to non-doped Mg2 Si at about 408 K. The electric conductivity of the sample doped with 2000 ppm Y becomes 1.69 times of that of pure Mg2Si at 468 K, while the former had a better comprehensive electrical performance. Their thermal conductivity was reduced to 70% and 84% of that of non-doped Mg2Si. Thus, the figure of merit and ZT of these two samples were enhanced visibly, which were 3.3 and 2.4 times of the non-doped samples at 408 K and 468 K, respectively. The maximal ZT belonging to samples doped with 2500 ppm Sc went up to 0.42 at about 498 K, higher than 0.40 of sample doped with 2000 ppm Y at 528 K and 0.25 of non-doped Mg2Si at 678 K, and the samples doped with Sc seemed to get the best thermoelectric performances at lower temperature.

Liqi, Wang; Qingsen, Meng; Wenhao, Fan

2012-11-01

369

The Formation of Sulfate and Elemental Sulfur Aerosols Under Varying Laboratory Conditions: Implications for Early Earth  

NASA Technical Reports Server (NTRS)

The presence of sulfur mass-independent fractionation (S-MIF) in sediments more than 2.45 x 10(exp 9) years old is thought to be evidence for an early anoxic atmosphere. Photolysis of sulfur dioxide (SO2) by UV light with lambda < 220 nm has been shown in models and some initial laboratory studies to create a S-MIF; however, sulfur must leave the atmosphere in at least two chemically different forms to preserve any S-MIF signature. Two commonly cited examples of chemically different sulfur species that could have exited the atmosphere are elemental sulfur (S8) and sulfuric acid (H2S04) aerosols. Here, we use real-time aerosol mass spectrometry to directly detect the sulfur-containing aerosols formed when SO2 either photolyzes at wavelengths from 115 to 400 nm, to simulate the UV solar spectrum, or interacts with high-energy electrons, to simulate lightning. We found that sulfur-containing aerosols form under all laboratory conditions. Further, the addition of a reducing gas, in our experiments hydrogen (H2) or methane (CH4), increased the formation of S8. With UV photolysis, formation of S8 aerosols is highly dependent on the initial SO2 pressure; and S8 is only formed at a 2% SO2 mixing ratio and greater in the absence of a reductant, and at a 0.2% SO2 mixing ratio and greater in the presence of 1000 ppmv CH4. We also found that organosulfur compounds are formed from the photolysis of CH4 and moderate amounts of SO2, The implications for sulfur aerosols on early Earth are discussed.

DeWitt, H. Langley; Hasenkopf, Christa A.; Trainer, Melissa G.; Farmer, Delphine K.; Jimenez, Jose L.; McKay, Christopher P.; Toon, Owen B.; Tolbert, Margaret A.

2010-01-01

370

Recovery and separation of rare earth elements using columns loaded with DNA-filter hybrid.  

PubMed

Given that the supply of several rare earth elements (REEs) is sometimes limited, recycling REEs used in various advanced materials, such as Nd magnets, is important for realizing efficient use of REE resources. In the present work, the feasibility of using DNA for REE recovery and separation was examined, along with the identification of the binding site of REEs in DNA. In particular, a DNA-cellulose filter paper hybrid was prepared so that DNA-based materials can be used for the separation of REEs using columns loaded with DNA. N,N'-Disuccinimidyl was used as a cross-linker reagent for the fixation of DNA onto a fibrous cellulose filter. The results showed that (i) the DNA-filter hybrid has a sufficiently high affinity to adsorb REEs; (ii) the adsorption capacity was 0.182 mg/g for Nd; and (iii) the affinity of REEs for DNA was stronger for REEs with larger atomic numbers. The difference of the affinity among REEs in the third result was compared with the adsorption patterns of REEs discussed in the literature. The comparison suggests that phosphate in the DNA-filter paper hybrid was responsible for REE adsorption onto the hybrid. The results were supported by the Nd, Dy, and Lu L(III)-edge EXAFS; the REE-P shell was identified for the second neighboring atom, showing the importance of the phosphate site as REE binding sites. The difference in the affinity among REEs suggest that group separation of REEs (such as La, Ce, (Pr and Nd), (Ho, Dy, and Er), (Tb and Gd), (Sm, Eu), Tm, Yb, and Lu) is possible, although complete isolation of each REE from a solution containing all REEs may be difficult. For practical applications, Nd and Fe(III) were successfully separated from a synthetic solution of Nd magnet waste using columns loaded with the DNA-filter hybrid. PMID:23059995

Takahashi, Yoshio; Kondo, Kazuhiro; Miyaji, Asami; Umeo, Miyuki; Honma, Tetsuo; Asaoka, Satoshi

2012-01-01

371

Aluminium competitive effect on rare earth elements binding to humic acid  

NASA Astrophysics Data System (ADS)

Competitive mechanisms between rare earth elements (REE) and aluminium for humic acid (HA) binding were investigated by combining laboratory experiments and modeling to evaluate the effect of Al on REE-HA complexation. Results indicates that Al3+ competes more efficiently with heavy REE (HREE) than with light REE (LREE) in acidic (pH = 3) and low REE/HA concentration ratio conditions providing evidence for the Al high affinity for the few HA multidentate sites. Under higher pH - 5 to 6 - and high REE/HA conditions, Al is more competitive for LREE suggesting that Al is bound to HA carboxylic rather than phenolic sites. PHREEQC/Model VI Al-HA binding parameters were optimized to simulate precisely both Al binding to HA and Al competitive effect on REE binding to HA. REE-HA binding pattern is satisfactorily simulated for the whole experimental conditions by the ?LK1A optimization (i.e. ?LK1A controls the distribution width of log K around log KMA). The present study provides fundamental knowledge on Al binding mechanisms to HA. Aluminium competitive effect on other cations binding to HA depends clearly on its affinity for carboxylic, phenolic or chelate ligands, which is pH dependent. Under circumneutral pH such as in natural waters, Al should lead to LREE-depleted patterns since Al is expected to be bound to weak HA carboxylic groups. As deduced from the behavior of Al species, other potential competitor cations are expected to have their own competitive effect on REE-HA binding. Therefore, in order to reliably understand and model REE-HA patterns in natural waters, a precise knowledge of the exact behavior of the different REE competitor cations is required. Finally, this study highlights the ability of the REE to be used as a "speciation probe" to precisely describe cation interactions with HA as here evidenced for Al.

Marsac, Rémi; Davranche, Mélanie; Gruau, Gérard; Dia, Aline; Bouhnik-Le Coz, Martine

2012-07-01

372

Rare earth element distributions in anoxic waters of the Cariaco Trench  

NASA Astrophysics Data System (ADS)

The concentrations of dissolved and suspended particulate rare earth elements in the Cariaco Trench are reported. In solution all REE, notably Ce, show a sharp increase just at or below the oxic/anoxic interface at 300 meters depth. Particulate concentrations show a complementary decrease at the same depth. The overlying oxic waters exhibit a negative Ce anomaly; the anoxic waters carry a slightly positive Ce anomaly. The particulate Ce anomaly reaches a maximum just above the interface, coinciding with maxima for particulate Mn and Fe and minima for the dissolved Ce anomaly and dissolved Ce, Mn and Fe. Thermodynamic calculations predict that the solubility of Ce(IV)O 2 is greatly enhanced by the steep p?-drop at the O 2/H 2S interface whereas oxygenated seawater is grossly oversaturated with dissolved Ce(III). However, the dramatic shifts in pe and absolute total Ce concentration do not affect the relative speciation of Ce in solution, which varies only with pH and not with p? because dissolved Ce(IV)-species are negligible. The cycling of Ce across the oxic/anoxic boundary is driven largely by its own redox chemistry as with Fe and Mn. The remaining REE, being strictly trivalent, are recycled in association with the dissolution-precipitation of (ferro)manganese oxyhydroxides. The relative turnover rates at the interface are ranked as Mn > Ce = Ce-anomaly > Nd, Sm, Eu, La, Dy, Er. The observed absence of Eu anomalies would render in situ reduction of Eu(III) to Eu(II) unlikely; thermodynamic considerations also rule out the existence of Eu(II) species in low temperature reducing environments.

de Baar, Hein J. W.; German, Christopher R.; Elderfield, Henry; van Gaans, Pauline

1988-05-01

373

Origins of organic geochemistry  

USGS Publications Warehouse

When organic geochemistry actually began as a recognized geoscience is a matter of definition and perspective. Constraints on its beginning are placed by the historical development of its parent disciplines, geology and organic chemistry. These disciplines originated independently and developed in par