Sample records for re-os pyrite geochronology

  1. Re-Os pyrite geochronology of Zn-Pb mineralization in the giant Caixiashan deposit, NW China (United States)

    Li, Dengfeng; Chen, Huayong; Hollings, Pete; Zhang, Li; Mi, Mei; Li, Jie; Fang, Jing; Wang, Chengming; Lu, Wanjian


    The newly discovered Caixiashan Irish-type Zn-Pb deposit (˜131 Mt at 3.95 % Zn + Pb), located in the Eastern Tianshan of Xinjiang, is one of the largest Zn-Pb deposits in NW China. Massive colloform/framboidal textured syn-sedimentary pyrite yielded a Re-Os isochron age of 1019 ± 70 Ma (MSWD = 3.5), which is interpreted to be the depositional age of the Kawabulake group that hosts the ore. The age of the main mineralization stage is constrained by two types of pyrite: the layered pyrite coexists with recrystallized calcite and dolomite and is locally replaced by sphalerite, whereas the euhedral pyrite occurs with galena that crosscuts the massive sphalerite. The layered pyrite yielded a Re-Os age of 859 ± 79 Ma (MSWD = 6.7; initial 187Os/188Os ratio [IOs] = 0.19 ± 0.25) and the euhedral pyrite 837 ± 39 Ma (MSWD = 6.5; [IOs] = 0.16 ± 0.09), which are interpreted to be the Zn and Pb mineralization ages, respectively. The low radiogenic initial Os values of the Zn-Pb mineralization suggest interaction between a hydrothermal fluid and a mafic or ultramafic source rock with a mantle Os signature with some contamination with Mesoproterozoic Kawabulake group. Based on our new Re-Os ages, we conclude that the giant Caixiashan Zn-Pb deposit formed in the early Neoproterozoic and it represents a newly identified mineralization epoch in the Eastern Tianshan of the Central Asia Orogenic Belt.

  2. Re-Os sulfide geochronology of the Red Dog sediment-hosted Zn-Pb-Ag deposit, Brooks Range, Alaska (United States)

    Morelli, R.M.; Creaser, R.A.; Selby, D.; Kelley, K.D.; Leach, D.L.; King, A.R.


    The Red Dog sediment-hosted deposit in the De Long Mountains of northern Alaska is the largest Zn producer in the world. Main stage mineralization is characterized by massive sulfide ore and crosscutting subvertical veins. Although the vein mineralization is clearly younger than the massive ore, the exact temporal relationship between the two is unclear. Re-Os geochronology of pyrite is used to determine the absolute age of main stage ore at Red Dog. A 10-point isochron on both massive and vein pyrite yields an age of 338.3 ?? 5.8 Ma and is interpreted to represent the age of main stage ore. The Re-Os data indicate that both massive and vein ore types are coeval within the resolution of the technique. Formation of the Red Dog deposit was associated with extension along a passive continental margin, and therefore the Re-Os age of main stage ore constrains the timing of rifting as well as the age of the host sedimentary rocks. Sphalerite from both massive and vein ore yields imprecise ages and shows a high degree of scatter compared to pyrite. We suggest that the Re-Os systematics of sphalerite can be disturbed and that this mineral is not reliable for Re-Os geochronology. ?? 2004 by Economic Geology.

  3. Re-Os dating of pyrite from Giant Bayan Obo REE-Nb-Fe deposit

    Institute of Scientific and Technical Information of China (English)

    LIU Yulong; YANG Gang; CHEN Jiangfeng; DU Andao; XIE Zhi


    Six pyrite samples from the giant Bayan Obo REE-Nb-Fe deposit are dated by Re-Os technique. Pyrite studied is associated with barite and separated from a vein cutting REE mineralization. Pyrites analyzed contain 16-30 ng Re and 0.10-0.16 ng Os, and yield a Caledonian isochron age of 439 ± 86 Ma. High Re/Os ratio, low Os concentration and highly radiogenic Os isotopic ratios of these samples suggest that they are of crustal origin. The northern margin of the North China Block was a passive continental margin, but not a subduction zone with enormous volcanic activities in the Early Paleozoic Era. Our Re-Os result provides new evidences, showing that Bayan Obo deposit experienced a thermal disturbance of crustal origin in the Caledonian time and some isotopic systems recorded only the time of the disturbance, not the mineralization age.

  4. Re-Os geochronology of the El Salvador porphyry Cu-Mo deposit, Chile: Tracking analytical improvements in accuracy and precision over the past decade (United States)

    Zimmerman, Aaron; Stein, Holly J.; Morgan, John W.; Markey, Richard J.; Watanabe, Yasushi


    Sulfide minerals from the El Salvador porphyry Cu-Mo deposit, Chile, were dated by Re-Os geochronology to clarify the timing and duration of mineralization. As these data are collected over the past 10 years, they chronicle the evolution of Re-Os analytical procedures and improvements in spike-sample equilibration, mass spectrometry and data reduction. Included in the data is the first tennantite-pyrite Re-Os isochron along with tennantite-enargite-pyrite Os tracing of ore metals based on initial osmium systematics (187Os/188Osi). Porphyry-associated mineralization follows the traditional early (A), transitional (B), and late (D) stage classification of relative timing of vein formation. Most Cu- and Mo-bearing sulfides were deposited during stages A and B. Field relationships clearly show the B-stage veins are older than the D-stage veins. Samples analyzed with Carius tube digestion and mixed-double spike indicate B-stage molybdenite mineralization between 41.8 and 41.2 Ma. These ages best represent the timing of main-stage mineralization at El Salvador. A five-point 187Re-187Os isochron for pyrite-tennantite from the latest D-stage veins yields an age of 42.37 ± 0.45 Ma. The isochron age, while older, is within error of early analyses of molybdenite by alkaline fusion digestion using single Re and Os spikes (42.4-42.0 Ma). A separate pyrite and tennantite-enargite pair containing significant common Os yields an initial 187Os/188Os ratio of 0.134 ± 0.042, compatible with a predominantly mantle origin. We appreciate the early analyses for their historical significance while emphasize the geological implications of the 41.8-41.2 Ma molybdenite ages. Temperature estimates by sulfur thermometry and fluid inclusions are 390-510 °C for the B-stage molybdenites and 230-240 °C for the latest D-stage pyrite and tennantite. Analyses based on Carius tube digestion and updated spike calibrations suggest a ∼0.6 m.y. duration (∼41.8 to 41.2 Ma) in-line with published

  5. Temporal evolution of mineralization events in the Bohemian Massif inferred from the Re-Os geochronology of molybdenite (United States)

    Ackerman, Lukáš; Haluzová, Eva; Creaser, Robert A.; Pašava, Jan; Veselovský, František; Breiter, Karel; Erban, Vojtěch; Drábek, Milan


    Molybdenite is a common mineral accompanying Sn-W, Au, and base metal mineralizations located in different geotectonic units of the Bohemian Massif, but it is also widespread in granitoids and/or related quartz veins/pegmatites forming disseminated Mo mineralization. Thirty Re-Os ages were obtained for molybdenite samples from the Bohemian Massif to provide constraints on the timing and duration of mineralization event(s) within the framework of previously published geochronological data for the host and/or associated rocks. The obtained data for Sn-W-(Li) deposits in the Erzgebirge metallogenetic province indicate the predominance of one and/or multiple short-time mineralization events taking place between ˜319 and 323 Ma, with the exception of the Krupka deposit associated with the Altenberg-Teplice caldera where the data may suggest prolonged activity until ˜315 Ma. The ages of the Pb-Zn-(Au-Mo) Hůrky u Rakovníka and Fe-Cu-As Obří důl mineralizations from the exocontacts of the Čistá pluton and Krkonoše-Jizera Plutonic Complex, respectively, provide evidence for synchronous emplacement of the ore and the associated granitic rocks. In contrast, the Padrť Fe-As-Mo mineralization postdates the age of the associated Padrť granite. Disseminated Mo mineralization in Cadomian and Variscan granitoids and/or related to quartz veins/pegmatites provides Re-Os ages that overlap with the previously published geochronological data for the host rocks, suggesting coeval evolution. Molybdenite samples from the Sázava suite granites of the Central Bohemian Plutonic Complex (CBPC) have resolvable younger ages than their host granites, but similar to the age of spatially related Au mineralization which is associated with the latest evolution of the CBPC.

  6. Re-Os systematics and age of pyrite associated with stratiform Zn-Pb mineralization in the Howards Pass district, Yukon and Northwest Territories, Canada (United States)

    Kelley, Karen D.; Selby, David; Falck, Hendrik; Slack, John F.


    Stratiform Zn-Pb deposits hosted in unmetamorphosed carbonaceous and siliceous mudstones of the Ordovician to Silurian Duo Lake Formation define the Howards Pass district in Yukon Territory and Northwest Territories, western Canada. Collectively, the deposits are amongst the largest in the world, containing drill-indicated and inferred resources of 423 Mt at 4.84 % Zn and 1.59 % Pb. Sulphide textures include (a) fine-scale laminations of sphalerite, galena, and pyrite from rock; (b) layers of coarse sulphide that are structurally controlled by microfolds; and (c) veins that cut bedding and sulphide laminations. The finely interlaminated nature of sulphides with mudstone has been used as evidence for syngenetic mineralizing processes, whereas paleomagnetic data determined on coarse layered sulphides suggest a Middle Jurassic age of mineralization. Here, we present new rhenium-osmium (Re-Os) isotopic data for 12 pyrite separates obtained from 4 laminated sulphide-rich samples from the XY Central (XYC) and Don (DON) deposits and for 1 unmineralized organic-rich mudstone ˜20 m stratigraphically below the sulphide-bearing zone. Pyrite separates that lack mudstone inclusions ("pure") from the XYC deposit contain 2.2 to 4.0 ppb Re and 93.4 to 123.4 ppt Os; pure pyrite from the DON deposit is significantly more enriched in Re and Os (34-37 ppb Re; 636.8-694.9 ppt Os). The 187Re/188Os values of pure pyrite separates from the XYC and DON deposits range from 137.6 to 197 and 182.1 to 201.4, respectively. Regression of all pure pyrite Re-Os data from both deposits yields an isochron age of 442 ± 14 Ma (MSWD = 7.4) and an initial 187Os/188Os (Osi) value of 0.71 ± 0.07. The Re-Os age indicates that the early phase of pyrite precipitation (and by inference, sphalerite and galena) occurred during the early Silurian, consistent with biostratigraphic ages of the host rocks. The Osi value of ˜0.8 for earliest Silurian seawater recorded from organic-rich shale in the basal

  7. Fluid inclusion characteristics and molybdenite Re-Os geochronology of the Qulong porphyry copper-molybdenum deposit, Tibet (United States)

    Li, Yang; Selby, David; Feely, Martin; Costanzo, Alessandra; Li, Xian-Hua


    The Qulong porphyry copper and molybdenum deposit is located at the southwest margin of the Lhasa Terrane and in the eastern region of the Gangdese magmatic belt. It represents China's largest porphyry copper system, with ˜2200 million tonnes of ore comprising 0.5 % Cu and 0.03 % Mo. The mineralization is associated with Miocene granodiorite, monzogranite and quartz-diorite units, which intruded into Jurassic volcanic units in a post-collisional (Indian-Asian) tectonic setting. Field observations and core logging demonstrate the alteration and mineralization at Qulong are akin to typical porphyry copper systems in subduction settings, which comprise similar magmatic-hydrothermal, potassic, propylitic and phyllic alteration assemblages. Molybdenite Re-Os geochronology confirms the relative timeframe defined by field observations and core logging and indicates that the bulk copper and molybdenum at Qulong were deposited within 350,000 years: between 16.10 ± 0.06 [0.08] (without and with decay constant uncertainty) and 15.88 ± 0.06 [0.08] Ma. This duration for mineralization is in direct contrast to a long-lived intrusive episode associated with mineralization based on previous zircon U-Pb data. Our fluid inclusion study indicates that the ore-forming fluid was oxidized and contained Na, K, Ca, Fe, Cu, Mo, Cl and S. The magmatic-hydrothermal transition occurred at ˜425 °C under lithostatic pressure, while potassic, propylitic and phyllic alteration occurred at hydrostatic pressure with temperature progressively decreasing from 425 to 280 °C. The fluid inclusion data presented here suggests that there has been ˜2.3 km of erosion at Qulong after its formation, and this erosion may be related to regional uplift of the Lhasa Terrane.

  8. Re-Os isotopic and trace element compositions of pyrite and origin of the Cretaceous Jinchang porphyry Cu-Au deposit, Heilongjiang Province, NE China (United States)

    Zhang, Peng; Huang, Xiao-Wen; Cui, Bin; Wang, Bo-Chao; Yin, Yi-Fan; Wang, Jing-Rui


    The Jinchang Cu-Au deposit in Northeast China contains more than 76 tons of Au and 4683 tons of Cu with average ore grades of 11.34 g/t Au and 1.44% Cu. The deposit is typical of porphyry types and consists of gold orebodies mainly hosted in a ∼113 Ma granitic porphyry and breccia pipes within the porphyry intrusion. Mineralization is closely associated with early potassic alteration and late phyllic alteration. Pyrite is the main Au-bearing mineral and contains 1.48-18.9 ppb Re and 11.4-38 ppt common Os. Extremely low common Os concentrations and high Re/Os ratios are indicative of derivation of ore-forming materials from the crust. Low Re in pyrite from the Jinchang deposit may indicate a mixing source of mantle and crust or a crustal source. Five Re-Os isotopic analyses yield a model 1 isochron age of 114 ± 22 Ma (2σ, MSWD = 0.15), similar to the age of the host porphyry. Pyrite contains detectable Co, Ni, Cu, Zn, As, Ag, Au, Sb, Pb and Bi. Pyrite has Co/Ni ratios similar to that of volcanogenic and hydrothermal sulfide deposits, indicating a magmatic-hydrothermal origin, and has Au and As contents similar to that of porphyry-epithermal systems. Pyrite grains from potassic and phyllic alteration stages have different trace element contents, reflecting the evolution of ore-forming fluids from magmatic dominated to magmatic mixed with meteoric water. In combination with regional geology, our new results are suggestive of origin of the Jinchang Cu-Au deposit from contemporary intrusions of granitic porphyries related to the Early Cretaceous subduction of the Paleo-Pacific plate.

  9. The Re-Os Isotopic System: Geochemistry and Methodology at the Geochronological Research Center (CPGeo of the University of São Paulo, Brazil

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    Ciro Teixeira Correia


    Full Text Available The Re-Os isotopic system is an important tool for the study of mantle-crust processes, geochronology and the tracingof source reservoirs for metal deposition. Rhenium and osmium differ fundamentally from other lithophile isotopic systemswith regards to their behavior during partial melting processes, coupled with the chalcophile/siderophile nature of bothelements. These differences make the system extremely useful for a number of novel applications not traditionally addressedby lithophile isotopic systems. A low-blank technique for the analysis of Re-Os isotopes in geological materials has beenestablished at the Geochronological Research Center (CPGeo of the Geosciences Institute of the University of São Paulo,Brazil, with the aim of furthering knowledge of regional geology, tectonic evolution, petrology and ore deposition in SouthAmerica. The techniques described here use isotope dilution to simultaneously determine the concentration of Os and Re aswell the Os isotopic composition of geologic materials. Sample digestion and sample-isotopic spike equilibration are achievedin sealed borosilicate glass tubes at high temperature. Osmium is separated and purified by carbon tetrachloride solventextraction and micro-distillation techniques. Rhenium is separated and purified by anion exchange chromatography. Accuracyof the concentration and isotopic determinations is monitored by the analysis of a certified reference material (WPR-1 andthe use of the Department of Terrestrial Magnetism (DTM Os isotopic standard. Measured values and precision of thesestandards is within error and comparable to established Re-Os laboratories.

  10. Geochemistry and Re-Os geochronology of the organic-rich sedimentary rocks in the Jingtieshan Fe-Cu deposit, North Qilian Mountains, NW China (United States)

    Yang, Xiuqing; Zhang, Zuoheng; Li, Chao; Duan, Shigang; Jiang, Zongsheng


    The Jingtieshan Group in the North Qilian Mountains, NW China, is dominantly composed of banded iron formations (BIFs), copper deposits and organic-rich sedimentary rocks (ORS, carbonaceous phyllite). X-ray diffraction analysis of the ORS shows the mineral assemblage to be quartz + clay minerals. The total organic carbon contents show a range of 0.44-1.72%. Here we present the results of the geochemistry and Re-Os geochronology of the ORS from the Jingtieshan Group. The high values of Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), Plagioclase Index of Alteration (PIA), and Th/U ratio, indicate intense weathering. The Al2O3/TiO2, Zr/Sc, Th/Sc, La/Th ratios, high rare earth elements abundances, light rare earth elements enrichment (normalized to chondrite), and distinctly negative Eu anomalies, suggest that the Jingtieshan Group ORS were derived mainly from felsic volcanic units. The new Re-Os isochron age of 1308 ± 100 Ma (2σ, n = 6, MSWD = 23) broadly overlap with the previous published ages determined using Sm-Nd and U-Pb isotope systems. The new age represents the depositional age of the Jingtieshan Group, as well that of BIF in the Jingtieshan area. Furthermore, the initial 187Os/188Os ratios (0.44 ± 0.07) indicate that the Os in the seawater was dominantly derived from hydrothermal fluids (∼75%). The Ce anomaly (Ce/Ce∗ = 0.95-1.00) and V/(V + Ni) ratios (0.71-0.86), as well as the lack of enrichment in redox-sensitive trace elements such as U, V, Zn, Pb, Cu, Ni, Cr, Co and Mn, together with the presence of overlying BIF, suggest that the Jingtieshan area represents a ferruginous deep-water succession. This, and intense submarine hydrothermal activities contributed to the deposition of the Jingtieshan BIF.

  11. Re-Os and U-Pb geochronology of the Laochang Pb-Zn-Ag and concealed porphyry Mo mineralization along the Changning-Menglian suture, SW China: implications for ore genesis and porphyry Cu-Mo exploration (United States)

    Deng, Xiao-Dong; Li, Jian-Wei; Zhao, Xin-Fu; Wang, Hong-Qiang; Qi, Liang


    Numerous polymetallic volcanogenic massive sulfide (VMS), vein, and replacement deposits are distributed along the Changning-Menglian suture zone in Sanjiang Tethyan metallogenic province, SW China. Laochang is the largest Pb-Zn-Ag vein and replacement deposit in this area, with a proven reserve of 0.51 Mt Pb, 0.34 Mt Zn, and 1,737 t Ag. Its age and relationship to magmatic events and VMS deposits in the region, however, have long been debated. In this paper, we present pyrite Re-Os and titanite U-Pb ages aiming to provide significant insights into the timing and genesis of the Pb-Zn-Ag mineralization. Pyrite grains in textural equilibrium with galena, sphalerite, and chalcopyrite from stratabound Pb-Zn-Ag and Cu-bearing Pb-Zn-Ag orebodies have a Re-Os isochron age of 45.7 ± 3.1 Ma (2 σ, mean square weighted deviation (MSWD) = 0.45), whereas titanite grains intergrown with sulfide minerals yield a weighted mean 206Pb/238U age of 43.4 ± 1.2 Ma (2 σ, n = 8). A Mo-mineralized granitic porphyry intersected by recent drilling below the Laochang Pb-Zn-Ag ores yields a zircon U-Pb age of 44.4 ± 0.4 Ma (2 σ, n = 12). Within analytical uncertainties, the ages of the Pb-Zn-Ag deposit and the concealed Mo-mineralized porphyry are indistinguishable, indicating that they are products of a single magmatic hydrothermal system. The results show that Laochang Pb-Zn-Ag deposit is significantly younger than the host mafic volcanic rock (zircon U-Pb age of 320.8 ± 2.7 Ma; 2 σ, n = 12) and Silurian VMS deposits along the Changning-Menglian suture zone, arguing against its origin as a Carboniferous VMS deposit as many researchers claimed. The initial 187Os/188Os ratio (0.540 ± 0.012) obtained from the pyrite Re-Os isochron suggests that metals were likely derived from the granitic porphyry that formed from a hybrid magma due to mixing of crustal- and mantle-derived melts, rather than from the mafic volcanic host rocks as previously thought. Our results favor that the Laochang

  12. Genesis of the Datuanshan stratabound skarn Cu(-Mo) deposit, Middle-Lower Yangtze Valley, Eastern China: constraints from geology, Re-Os geochronology, mineralogy, and sulfur isotopes (United States)

    Cao, Yi; Gao, Fuping; Du, Yangsong; Du, Yilun; Pang, Zhenshan


    Stratabound deposits are the most abundant and economically significant ore type in the Middle-Lower Yangtze River Valley, one of the most important metallogenic belts in China. The Datuanshan deposit is one of the largest and most representative stratabound Cu(-Mo) deposits in the Tongling district of the Middle-Lower Yangtze River metallogenic belt. All the orebodies of the Datuanshan deposit occur around Mesozoic quartz monzodiorite and are tabular or semi-tabular bodies along bedding-parallel faults within upper Permian to Lower Triassic strata. However, discordant and crosscutting relationships (e.g., the host rocks crosscut by skarn- and quartz-sulfide veins, with alteration halos around the veins) have also been found, especially along the skarn-host contact and orebody-host contact, indicating that skarnitization and mineralization postdated the deposition of the host sediments. The skarn consists mainly of prograde garnet and pyroxene and retrograde alteration assemblages of amphibole, epidote, and chlorite, as well as quartz and sulfides. Electron microprobe analyses show that the garnets and pyroxenes are grossular-andradite and hedenbergite-diopside series, respectively, and all samples plot in the field of typical skarn copper deposits worldwide. Molybdenite samples from stratiform copper ores yield Re-Os model ages of 138.2-139.9 Ma with a weighted mean age of 139.2 ± 0.9 Ma. This is reasonably consistent with the ages of the stratiform Mo ores (138.0-140.8 Ma) and genetically related quartz monzodiorite (135.2-139.3 Ma) in the Datuanshan deposit, indicating that the stratiform Cu and Mo mineralization was contemporaneous with emplacement of the quartz monzodiorite magmas in the Early Cretaceous. Fifteen δ34S values for sulfides range from -1.8 to +4.7 ‰, with a mean of 0.5 ‰, indicating that the sulfur was derived mainly from a magmatic source. Moreover, the sulfur isotope values of the ores are consistent with those of Mesozoic intermediate

  13. U-Pb zircon and Re-Os molybdenite geochronology from La Caridad porphyry copper deposit: insights for the duration of magmatism and mineralization in the Nacozari District, Sonora, Mexico (United States)

    Valencia, V. A.; Ruiz, J.; Barra, F.; Geherls, G.; Ducea, M.; Titley, S. R.; Ochoa-Landin, L.


    Uranium-lead zircon (laser ablation multi-collector ICP-MS spot analysis) ages from La Caridad porphyry copper deposit in the Nacozari District, Northeastern Sonora, Mexico, suggest a short period of magmatism, between 55.5 and 52.6 Ma. Two U-Pb ages from the mineralized quartz monzonite unit, showing different textural characteristics, yielded indistinguishable crystallization ages (~54 Ma), and indicate that the intrusion responsible for the mineralization occurred as a single large complex unit, instead of multiple pulses of magmatism. Some zircons analyzed also show inherited ages in cores recording dates of 112-124 Ma, 141-166 Ma and 1.4 Ga. The Re-Os molybdenite ages from the potassic and phyllic hydrothermal alteration veins yielded identical ages within error, 53.6±0.3 Ma and 53.8±0.3 Ma, respectively (weighted average of 53.7±0.21 Ma), supporting a restricted period for the mineralization. The geochronological data thus indicate a short-lived magmatic and hydrothermal system. The inherited zircons of Precambrian and Late Jurassic-Mid Cretaceous age found in the intrusive rocks of La Caridad deposit, can be explained considering two possible scenarios within the tectonic/magmatic evolution of the area. The first scenario considers the presence of a Precambrian anorogenic granitic basement that is intruded by Mesozoic (Jurassic-Cretaceous) units present beneath the La Caridad deposit. The second scenario suggests that the Mesozoic Glance Conglomerate Formation of Arizona underlies the Paleocene volcanic-igneous pile in the La Caridad area.

  14. U-Pb Geochronology of VMS mineralization in the Iberian Pyrite Belt (United States)

    Barrie, Tucker C.; Amelin, Yuri; Pascual, Emilio


    A geochronology study using U-Pb isotope dilution TIMS analyses of zircon has been conducted to determine the ages of volcanic-associated massive sulfide (VMS) deposits in the Iberian Pyrite Belt (IPB), the world's most prolific VMS province. Ages have been determined for host rocks to four VMS systems that span the IPB: the giant Rio Tinto and Aljustrel districts in the central region, Lagoa Salgada to the west, and Las Cruces to the east. A sample of chloritized quartz porphyritic dacite/rhyolite in the footwall of the San Dionisio massive sulfide deposit of the Rio Tinto district is 349.76±0.90 Ma. This is taken as the best age estimate of the mineralization in the Rio Tinto district, probably the world's largest volcanogenic massive sulfide system. Two xenocrystic zircons from the same sample yielded 207Pb/206Pb ages of 414 and 416 Ma, which provide a minimum estimate for the age of the inherited component. A biotite tonalite from the Campofrio area, 3.5 km north of the center of the Rio Tinto district, is chemically similar to the felsic host rock protolith at Rio Tinto. The Campofrio sample has an age of 346.26±0.81 Ma, slightly younger and outside of the 2σ error for the Rio Tinto age; therefore, this phase of this intrusion was not a heat source for the hydrothermal system that formed the deposits of the Rio Tinto district. The Campofrio sample also has three zircon analyses with 207Pb/206Pb minimum ages of 534, 536, and 985 Ma, indicating inheritance from Ordovician and Neoproterozoic sources. In the Aljustrel VMS district, a U-Pb zircon age of 352.9±1.9 Ma characterizes the altered Green Tuff host rock of the Algares deposit, which is slightly older than the Rio Tinto age. Two zircons with 207Pb/206Pb ages of 531 and 571 Ma from this sample indicate inheritance from a Cambrian or older source. The age of mineralization at Lagoa Salgada is given by essentially identical ages of 356.21±0.73 and 356.4±0.8 Ma, for footwall and hanging wall samples

  15. U-Pb, Re-Os, and 40Ar/39Ar geochronology of the Nambija Au-skarn and Pangui porphyry Cu deposits, Ecuador: implications for the Jurassic metallogenic belt of the Northern Andes (United States)

    Chiaradia, Massimo; Vallance, Jean; Fontboté, Lluis; Stein, Holly; Schaltegger, Urs; Coder, Joshua; Richards, Jeremy; Villeneuve, Mike; Gendall, Ian


    New U-Pb, Re-Os, and 40Ar/39Ar dates are presented for magmatic and hydrothermal mineral phases in skarn- and porphyry-related ores from the Nambija and Pangui districts of the Subandean zone, southeastern Ecuador. Nambija has been one of the main gold-producing centers of Ecuador since the 1980s due to exceptionally high-grade ores (average 15 g/t, but frequently up to 300 g/t Au). Pangui is a recently discovered porphyry Cu-Mo district. The geology of the Subandean zone in southeastern Ecuador is dominated by the I-type, subduction-related, Jurassic Zamora batholith, which intrudes Triassic volcanosedimentary rocks. The Zamora batholith is in turn cut by porphyritic stocks, which are commonly associated with skarn formation and/or porphyry-style mineralization. High precision U-Pb and Re-Os ages for porphyritic stocks (U-Pb, zircon), associated prograde skarn (U-Pb, hydrothermal titanite), and retrograde stage skarn (Re-Os, molybdenite from veins postdating gold deposition) of the Nambija district are all indistinguishable from each other within error (145 Ma) and indicate a Late Jurassic age for the gold mineralization. Previously, gold mineralization at Nambija was considered to be Early Tertiary based on K-Ar ages obtained on various hydrothermal minerals. The new Jurassic age for the Nambija district is slightly younger than the 40Ar/39Ar and Re-Os ages for magmatic-hydrothermal minerals from the Pangui district, which range between 157 and 152 Ma. Mineralization at Nambija and Pangui is associated with porphyritic stocks that represent the last known episodes of a long-lived Jurassic arc magmatism (˜190 to 145 Ma). A Jurassic age for mineralization at Nambija and Pangui suggests that the Northern Andean Jurassic metallogenic belt, which starts in Colombia at 3° N, extends down to 5° S in Ecuador. It also adds a new mineralization style (Au-skarn) to the metal endowment of this belt.

  16. Re-Os geochronology and Os isotope fingerprinting of petroleum sourced from a Type I lacustrine kerogen: insights from the natural Green River petroleum system in the Uinta Basin and hydrous pyrolysis experiments (United States)

    Cumming, Vivien M.; Selby, David; Lillis, Paul G.; Lewan, Michael D.


    Rhenium–osmium (Re–Os) geochronology of marine petroleum systems has allowed the determination of the depositional age of source rocks as well as the timing of petroleum generation. In addition, Os isotopes have been applied as a fingerprinting tool to correlate oil to its source unit. To date, only classic marine petroleum systems have been studied. Here we present Re–Os geochronology and Os isotope fingerprinting of different petroleum phases (oils, tar sands and gilsonite) derived from the lacustrine Green River petroleum system in the Uinta Basin, USA. In addition we use an experimental approach, hydrous pyrolysis experiments, to compare to the Re–Os data of naturally generated petroleum in order to further understand the mechanisms of Re and Os transfer to petroleum. The Re–Os geochronology of petroleum from the lacustrine Green River petroleum system (19 ± 14 Ma – all petroleum phases) broadly agrees with previous petroleum generation basin models (∼25 Ma) suggesting that Re–Os geochronology of variable petroleum phases derived from lacustrine Type I kerogen has similar systematics to Type II kerogen (e.g., Selby and Creaser, 2005a, Selby and Creaser, 2005b and Finlay et al., 2010). However, the large uncertainties (over 100% in some cases) produced for the petroleum Re–Os geochronology are a result of multiple generation events occurring through a ∼3000-m thick source unit that creates a mixture of initial Os isotope compositions in the produced petroleum phases. The 187Os/188Os values for the petroleum and source rocks at the time of oil generation vary from 1.4 to 1.9, with the mode at ∼1.6. Oil-to-source correlation using Os isotopes is consistent with previous correlation studies in the Green River petroleum system, and illustrates the potential utility of Os isotopes to characterize the spatial variations within a petroleum system. Hydrous pyrolysis experiments on the Green River Formation source rocks show that Re and Os transfer

  17. Petrography, geochemistry and geochronology of granite hosted rhyodacites associated with a disseminated pyrite mineralization (Arnolz, Southern Bohemian Massif, Austria) (United States)

    Göd, Richard; Kurzweil, Johannes; Klötzli, Urs


    The study focuses on a subvolcanic rhyodacite dyke intruding a fine grained biotite granite and paragneisses of the South Bohemian Massif, part of the Variscan Orogenic Belt in Central Europe. The subvertical dyke strikes NNE, displays a thickness of about 30 m and has been traced by boulder mapping for approximately 7 km. The rhyodacites have been affected by two hydrothermal fluids. An older one of oxidizing condition giving rise to a reddish to brownish type of rock (Type I) and a younger fluid of reducing condition causing a greenish variety (Type II). The hydrothermal alteration is associated with the formation of the clay minerals chlorite, sericite, kaolinite and smectite and a disseminated pyrite mineralization. Bulk chemistries of the rhyodacites emphasize the hydrothermal alterations to be isochemical with the exception of sulphur enriched up to a maximum of 0.6 wt%. Trace element composition of the rhyodacites points to a barren geochemical environment in terms of base and precious elements. Sulphur isotope investigations of pyrites from the rhyodacites and the hosting granites respectively yield d34S data ranging from +0.07 to -2.22 ‰, emphasizing a magmatic origin of the sulphur. Geochronological investigations yield in situ U/Pb zircon ages of 312 ± 4 Ma for the biotite granite and of 292 ± 4 Ma for the rhyodacitic dykes indicating a time gap of ≈ 20 Ma between these two intrusive events. A contemporaneous but geochemically specialized granitic intrusion associated with NW striking "felsitic" dykes occurs about 10 to 20 km to the NW of Arnolz. However, the rhyodacites around Arnolz differ significantly from these felsitic dykes in their geochemistry and alteration phenomena which points to a different magmatic source. This coincides with a change in the orientation of the dykes from a NW direction controlling the geochemically specialized intrusions in the NW to a dominating NNE direction mirrored by the studied rhyodacites at Arnolz.

  18. Petrography, geochemistry and geochronology of granite hosted rhyodacites associated with a disseminated pyrite mineralization (Arnolz, Southern Bohemian Massif, Austria) (United States)

    Göd, Richard; Kurzweil, Johannes; Klötzli, Urs


    The study focuses on a subvolcanic rhyodacite dyke intruding a fine grained biotite granite and paragneisses of the South Bohemian Massif, part of the Variscan Orogenic Belt in Central Europe. The subvertical dyke strikes NNE, displays a thickness of about 30 m and has been traced by boulder mapping for approximately 7 km. The rhyodacites have been affected by two hydrothermal fluids. An older one of oxidizing condition giving rise to a reddish to brownish type of rock (Type I) and a younger fluid of reducing condition causing a greenish variety (Type II). The hydrothermal alteration is associated with the formation of the clay minerals chlorite, sericite, kaolinite and smectite and a disseminated pyrite mineralization. Bulk chemistries of the rhyodacites emphasize the hydrothermal alterations to be isochemical with the exception of sulphur enriched up to a maximum of 0.6 wt%. Trace element composition of the rhyodacites points to a barren geochemical environment in terms of base and precious elements. Sulphur isotope investigations of pyrites from the rhyodacites and the hosting granites respectively yield d34S data ranging from +0.07 to -2.22 ‰, emphasizing a magmatic origin of the sulphur. Geochronological investigations yield in situ U/Pb zircon ages of 312 ± 4 Ma for the biotite granite and of 292 ± 4 Ma for the rhyodacitic dykes indicating a time gap of ≈ 20 Ma between these two intrusive events. A contemporaneous but geochemically specialized granitic intrusion associated with NW striking "felsitic" dykes occurs about 10 to 20 km to the NW of Arnolz. However, the rhyodacites around Arnolz differ significantly from these felsitic dykes in their geochemistry and alteration phenomena which points to a different magmatic source. This coincides with a change in the orientation of the dykes from a NW direction controlling the geochemically specialized intrusions in the NW to a dominating NNE direction mirrored by the studied rhyodacites at Arnolz.

  19. Zircon U-Pb and molybdenite Re-Os geochronology and Sr-Nd-Pb-Hf isotopic constraints on the genesis of the Xuejiping porphyry copper deposit in Zhongdian, Northwest Yunnan, China (United States)

    Leng, Cheng-Biao; Zhang, Xing-Chun; Hu, Rui-Zhong; Wang, Shou-Xu; Zhong, Hong; Wang, Wai-Quan; Bi, Xian-Wu


    The Xuejiping porphyry copper deposit is located in northwestern Yunnan Province, China. Tectonically, it lies in the southern part of the Triassic Yidun island arc. The copper mineralization is mainly hosted in quartz-dioritic and quartz-monzonitic porphyries which intruded into clastic-volcanic rocks of the Late Triassic Tumugou Formation. There are several alteration zones including potassic, strong silicific and phyllic, argillic, and propylitic alteration zones from inner to outer of the mineralized porphyry bodies. The ages of ore-bearing quartz-monzonitic porphyry and its host andesite are obtained by using the zircon SIMS U-Pb dating method, with results of 218.3 ± 1.6 Ma (MSWD = 0.31, N = 15) and 218.5 ± 1.6 Ma (MSWD = 0.91, N = 16), respectively. Meanwhile, the molybdenite Re-Os dating yields a Re-Os isochronal age of 221.4 ± 2.3 Ma (MSWD = 0.54, N = 5) and a weighted mean age of 219.9 ± 0.7 Ma (MSWD = 0.88). They are quite in accordance with the zircon U-Pb ages within errors. Furthermore, all of them are contemporary with the timing of the Garzê-Litang oceanic crust subduction in the Yidun arc. Therefore, the Xuejiping deposit could be formed in a continental margin setting. There are negative ɛNd(t) values ranging from -3.8 to -2.1 and relatively high initial 87Sr/86Sr ratios from 0.7051 to 0.7059 for the Xuejiping porphyries and host andesites. The (206Pb/204Pb)t, (207Pb/204Pb)t and (208Pb/204Pb)t values of the Xuejiping porphyries and host andesites vary from 17.899 to 18.654, from 15.529 to 15.626, and from 37.864 to 38.52, respectively, indicative of high radiogenic Pb isotopic features. In situ Hf isotopic analyses on zircons by using LA-MC-ICP-MS exhibit that there are quite uniform and slightly positive ɛHf(t) values ranging from -0.2 to +3.2 (mostly between 0 and +2), corresponding to relatively young single-stage Hf model ages from 735 Ma to 871 Ma. These isotopic features suggest that the primary magmas of the Xuejiping porphyries and

  20. Genesis of the Au-Bi-Cu-As, Cu-Mo ± W, and base-metal Au-Ag mineralization at the Mountain Freegold (Yukon, Canada): constraints from Ar-Ar and Re-Os geochronology and Pb and stable isotope compositions (United States)

    Bineli Betsi, Thierry; Lentz, David; Chiaradia, Massimo; Kyser, Kurt; Creaser, Robert A.


    The genesis of mineralized systems across the Mountain Freegold area, in the Dawson Range Cu-Au ± Mo Belt of the Tintina Au province was constrained using Pb and stable isotope compositions and Ar-Ar and Re-Os geochronology. Pb isotope compositions of sulfides span a wide compositional range (206Pb/204Pb, 18.669-19.861; 208Pb/204Pb, 38.400-39.238) that overlaps the compositions of the spatially associated igneous rocks, thus indicating a magmatic origin for Pb and probably the other metals. Sulfur isotopic compositions of sulfide minerals are broadly similar and their δ34S (Vienna-Canyon Diablo Troilite (V-CDT)) values range from -1.4 to 3.6 ‰ consistent with the magmatic range, with the exception of stibnite from a Au-Sb-quartz vein, which has δ34S values between -8.1 and -3.1 ‰. The δ34S values of sulfates coexisting with sulfide are between 11.2 and 14.2 ‰; whereas, those from the weathering zone range from 3.7 to 4.3 ‰, indicating supergene sulfates derived from oxidation of hypogene sulfides. The δ13C (Vienna Peedee Belemnite (VPDB)) values of carbonate range from -4.9 to 1.1 ‰ and are higher than magmatic values. The δ18O (V-SMOW) values of magmatic quartz phenocrysts and magmatic least-altered rocks vary between 6.2 and 10.1 ‰ and between 5.0 and 10.1 ‰, respectively, whereas altered magmatic rocks and hydrothermal minerals (quartz and magnetite) are relatively 18O-depleted (4.2 to 7.9 ‰ and -6.3 to 1.5 ‰, respectively). Hydrogen isotope compositions of both least-altered and altered igneous rock samples are D-depleted (from -133 to -161 ‰ Vienna-Standard Mean Ocean Water (V-SMOW)), consistent with differential magma degassing and/or post-crystallization exchange between the rocks and meteoric ground water. Zircon from a chlorite-altered dike has a U-Pb crystallization age of 108.7 ± 0.4 Ma; whereas, the same sample yielded a whole-rock Ar-Ar plateau age of 76.25 ± 0.53 Ma. Likewise, molybdenite Re-Os model ages range from 75.8 to

  1. Refinement of the time-space evolution of the giant Mio-Pliocene Río Blanco-Los Bronces porphyry Cu-Mo cluster, Central Chile: new U-Pb (SHRIMP II) and Re-Os geochronology and 40Ar/39Ar thermochronology data (United States)

    Deckart, Katja; Clark, Alan H.; Cuadra, Patricio; Fanning, Mark


    Representing one of the largest known (estimated >5 Gt at 1 % Cu and 0.02 % Mo) porphyry system, the Río Blanco-Los Bronces deposit incorporates at least five hypabyssal intrusive and hydrothermal centres, extending for about 5 km from the Río Blanco and Los Bronces mines in the north, through the Don Luis mine, to the Sur Sur mine, La Americana and Los Sulfatos in the south. The new geochronology data, which now include data on different molybdenite vein types, confirm the U-Pb ages of the pre-mineralisation intrusions but slightly increase their age range from 8.8 to 8.2 Ma. The distinct magmatic pulses of the mineralisation-associated porphyritic intrusives (Late Porphyries) indicate an age interval instead of the previously suggested individual ages: the quartz monzonite porphyry ranges from 7.7 to 6.1 Ma (Sur Sur 5.74 ± 0.13 Ma), the feldspar porphyry shows an interval from 5.8 to 5.2 Ma and the Don Luis porphyry from 5.2 to 5.0 Ma. The new Re-Os data on distinct molybdenite vein types confirm the protracted history of Cu(-Mo) mineralisation, inferred previously. The vein development occurred at least from 5.94 to 4.50 Ma, indicating a time-span of 1.5 Ma for the hydrothermal activity. Hydrothermal minerals dated by the 40Ar/39Ar method are generally too young to record the age of early, high-temperature mineralisation. The majority of the 40Ar/39Ar data in the Río Blanco porphyry cluster record reheating by either the youngest member of the Late Porphyry suite or the post-mineralisation dacite or rhyolite plug formations at around 4.9-4.7 Ma.

  2. The Re/Os Clock Revisited

    CERN Multimedia

    Leal, L C; Kitis, G; Guber, K H; Quaranta, A; Koehler, P E


    The purpose of the proposed project of an accurate measurement of the relevant neutron cross sections of $^{186}$Os and $^{187}$Os is to remove the principal nuclear physics uncertainties in the analysis of the Re/Os cosmochronometer. The necessary cross section information will be obtained in complementary experiments at the nTOF facility at CERN and at the Karlsruhe Van de Graaff accelerator. Transformation of these results into significantly improved stellar reaction rates will allow to evaluate the age of the elements in the framework of galactic chemical evolution models.

  3. Re/Os cosmochronometer: measurement of neutron cross sections

    Energy Technology Data Exchange (ETDEWEB)

    Mosconi, M.


    This experimental work is devoted to the improved assessment of the Re/Os cosmochronometer. The dating technique is based on the decay of {sup 187}Re (t{sub 1/2}=41.2 Gyr) into {sup 187}Os and determines the age of the universe by the time of onset of nucleosynthesis. The nucleosynthesis mechanisms, which are responsible for the {sup 187}Re/{sup 187}Os pair, provide the possibility to identify the radiogenic fraction of {sup 187}Os exclusively by nuclear physics considerations. Apart from its radiogenic component, {sup 187}Os can be synthesized otherwise only by the s process, which means that this missing fraction can be reliably determined and subtracted by proper s-process modeling. On the other hand, {sup 187}Re is almost completely produced by the r process. The only information needed for the interpretation as a cosmic clock is the production rate of {sup 187}Re as a function of time. The accuracy of the s-process calculations that are needed to determine the nucleosynthetic abundance of {sup 187}Os depends on the quality of the neutron capture cross sections averaged over the thermal neutron spectrum at the s-process sites. Laboratory measurements of these cross sections have to be corrected for the effect of nuclear levels, which can be significantly populated at the high stellar temperatures during the s process. The neutron capture cross sections of {sup 186}Os, {sup 187}Os and {sup 188}Os have been measured at the CERN n TOF facility in the range between 0.7 eV and 1 MeV. From these data, Maxwellian averaged cross sections have been determined for thermal energies from 5 to 100 keV with an accuracy around 4%, 3%, and 5% for {sup 186}Os, {sup 187}Os, and {sup 188}Os, respectively. Since, the first excited state in {sup 187}Os occurs at 9.75 keV, the cross section of this isotope requires a substantial correction for thermal population of low lying nuclear levels. This effect has been evaluated on the basis of resonance data derived in the (n, {gamma

  4. Re/Os cosmochronometer: measurement of neutron cross sections

    Energy Technology Data Exchange (ETDEWEB)

    Mosconi, M.


    This experimental work is devoted to the improved assessment of the Re/Os cosmochronometer. The dating technique is based on the decay of {sup 187}Re (t{sub 1/2}=41.2 Gyr) into {sup 187}Os and determines the age of the universe by the time of onset of nucleosynthesis. The nucleosynthesis mechanisms, which are responsible for the {sup 187}Re/{sup 187}Os pair, provide the possibility to identify the radiogenic fraction of {sup 187}Os exclusively by nuclear physics considerations. Apart from its radiogenic component, {sup 187}Os can be synthesized otherwise only by the s process, which means that this missing fraction can be reliably determined and subtracted by proper s-process modeling. On the other hand, {sup 187}Re is almost completely produced by the r process. The only information needed for the interpretation as a cosmic clock is the production rate of {sup 187}Re as a function of time. The accuracy of the s-process calculations that are needed to determine the nucleosynthetic abundance of {sup 187}Os depends on the quality of the neutron capture cross sections averaged over the thermal neutron spectrum at the s-process sites. Laboratory measurements of these cross sections have to be corrected for the effect of nuclear levels, which can be significantly populated at the high stellar temperatures during the s process. The neutron capture cross sections of {sup 186}Os, {sup 187}Os and {sup 188}Os have been measured at the CERN n TOF facility in the range between 0.7 eV and 1 MeV. From these data, Maxwellian averaged cross sections have been determined for thermal energies from 5 to 100 keV with an accuracy around 4%, 3%, and 5% for {sup 186}Os, {sup 187}Os, and {sup 188}Os, respectively. Since, the first excited state in {sup 187}Os occurs at 9.75 keV, the cross section of this isotope requires a substantial correction for thermal population of low lying nuclear levels. This effect has been evaluated on the basis of resonance data derived in the (n, {gamma

  5. Abundances and isotopic compositions of rhenium and osmium in pyrite samples from the Huaibei coalfield, Anhui, China (United States)

    Liu, Gaisheng; Chou, C.-L.; Peng, Z.; Yang, G.


    Two pyrite samples from the Shihezi Formation (Lower Permian), Huaibei coalfield, Anhui, China, have been analyzed for abundances and isotopic compositions of rhenium and osmium using negative thermal ion mass spectrometry. The Re-Os ages of the pyrites are 64.4 and 226 Ma, which are younger than the formation age of the coal seam. The pyrite samples may consist of pyrite formed at various stages during the history of coal formation. The ??Osvalues of the two pyrite samples are +17 and +18, respectively. Such high ??Osvalues are reported for the first time for recycles crustal materials from a sedimentary basin. ?? Springer-Verlag 2007.

  6. Re-Os isotopic system and formation age of subcontinental lithosphere mantle

    Institute of Scientific and Technical Information of China (English)


    The determination of the formation age of subcontinental Lithosphere Mantle (SCLM) is a widely concerned issue in mantle geochemistry. It is difficult to obtain the formation age of SCLM using lithophile isotopic systems such as Rb-Sr, Sm-Nd, U-Th-Pb, etc., but as siderophile elements, the Re-Os isotopic system provides a powerful tool for that work. Here a comprehensive review on the recent development in Re-Os dating for SCLM has been given.

  7. Geochronology of the western and central Brooks Range, Alaska: Implications for the geologic evolution of the Anarraaq and Red Dog Zn-Pb-Ag deposits (United States)

    Rombach, C.S.; Layer, P.W.


    A compilation of published geochronology of rocks and minerals from the western and central Brooks Range provides a framework for understanding the complex history of the Brooks Range and northern Alaska. A simplified timeline of events comprises (1) Devonian extension, (2) Mississippian extension and Zn-Pb-Ag mineralization, (3) a passive interval, (4) pre-Brooks Range orogeny rock-formation and thermal event, (5) inception of Brooks Range orogeny, (6) exhumation and the end of main-stage deformation, and (7) subsequent episodic deformation. This compilation is supplemented by new 40Ar/39Ar dates of white mica from the Anarraaq and Red Dog Zn-Pb-Ag (+ barite) deposits from the western Brooks Range. The deposits are hosted in black shale and carbonate rocks of the Late Mississippian-Early Pennsylvanian Kuna Formation. Quartz-pyrite-white mica grains in sedimentary rocks above the Anarraaq deposit yield an age of 195.0 ?? 2.0 Ma, and paragenetically late quartz-pyrite-white mica from the Main orebody at the Red Dog deposit has an age of 126.1 ?? 0.7 Ma. These white micas are much younger than the age of Zn-Pb-Ag mineralization at Red Dog (338 ?? 5.8 Ma Re-Os age of pyrite). The date for white mica from Anarraaq (???195 Ma) appears to be related to a large-scale thermal event in the region immediately before the inception of the Brooks Range orogeny. The white mica from the Red Dog deposit (???126 Ma) correlates with the later stages of the orogeny, a period of blueschist metamorphism, extension, and rapid exhumation, which varied with geographic location. These dates suggest that the Red Dog deposits underwent significant hydrothermal overprinting during multiple episodes of the Brooks Range orogeny. ?? 2004 by Economic Geology.

  8. Re-Os Isotopes Distinguish Crust vs. Slab Inputs to Northern Cascade Arc Basalts (United States)

    Mullen, E.; Gannoun, A.; Nauret, F.; Schiano, P.; Weis, D.


    Delineating the relative contributions of mantle, slab, and crust to arc magmas is particularly challenging in the Cascades where the continental crust is juvenile and contrasts little with magmas in traditional radiogenic isotope systems (Sr-Nd-Hf-Pb). The Re-Os isotope system offers a sensitive technique for evaluating these contributions because even young crust has significantly higher Os ratios than the mantle. We analyzed Re-Os isotope ratios in 33 primitive basalts from 9 volcanic centers of the northern Cascade Arc (Garibaldi Volcanic Belt, GVB). Although GVB basalts have mantle-like Sr-Pb-Nd-Hf ratios (Mullen & Weis, 2015, EPSL), the range in 187Os/188Os is very large (0.13-0.99) with [Os] of Cinder Cone/Mt. Garibaldi, Salal Glacier, Mt. Meager, Indian Pass/Glacier Peak) has low Os isotopic ratios (0.13-0.19), only slightly elevated relative to global mantle wedge peridotites (≤0.16), indicating minimal crustal contamination. Group 1 samples lie on Os-Sr isotope mixing curves indicating variable sediment input to the mantle. Os ratios of Group 2 basalts (Silverthrone, Bridge River, Elaho, Cheakamus, Mt. Baker, Glacier Peak) extend to extremely high values, up to 0.99, and lie on different Os-Sr mixing curves indicating addition of a crustal contaminant. Sr-Nd-Hf-Pb isotopic ratios cannot be used to identify this crustal input because Groups 1 and 2 are identical in these isotope systems. Interaction with a mafic underplate from older Cenozoic or accreted Mesozoic arcs is likely, and Re-Os analyses of basement samples (in progress) will provide a test of this hypothesis. This study reveals that most primitive magmas in the Cascades have suffered variable crustal contamination, but only the Re-Os isotope system has the potential to delineate the extent of this involvement.

  9. Re Os isotopes applied to the epithermal gold deposits near Bucaramanga, northeastern Colombia (United States)

    Mathur, R.; Ruiz, J.; Herb, P.; Hahn, L.; Burgath, K.-P.


    The epithermal gold mineralization near Bucaramanga, Colombia, is spatially associated with a dacitic porphyry of Upper Cretaceous to Early Tertiary age. Two mining districts in the vicinity of Bucaramanga, the California and the Vetas, host different styles of mineralization that could be interpreted as high- and low-sulfidation style mineralization, respectively. Re-Os isotope systematics were used on sulfide-gold-rich gravity concentrates in an attempt to determine both the ages of the epithermal deposits and the possible genetic relationships between the porphyry and the epithermal mineralization. The concentration of Os for sulfide samples taken from both systems is relatively uniform, ranging from 19 to 35 ppt (parts per trillion), whereas the Re concentration varies significantly, with the California system averaging 10 ppb (parts per billion) and the Vetas system averaging 140 ppb. The samples from the high-sulfidation California deposit form an isochron with an age of 57±10 Ma (MSWD=0.8), which overlaps with the age of the dacitic volcanism. The initial 187Os/ 188Os of the isochron is 1.20±0.13 and indicates a predominately crustal source for the Os and, by inference, gold. The samples from the Vetas low-sulfidation system have very high Re/Os ratios and do not lie on the isochron. These data reveal a difference between two epithermal systems that border one intrusion. Sulfide samples from the high-sulfidation system are isotopically homogenous with respect to Re-Os (form an isochron) and probably represent mineralization linked closely with the high temperature volatiles/fluids from the magma. In contrast, the sulfides from the Vetas system are in disequilibrium with respect to Re-Os and may illustrate mineralization that is not directly related to similar magmatic fluids.

  10. Preparation and certification of Re-Os dating reference materials: Molybdenites HLP and JDC (United States)

    Du, A.; Wu, S.; Sun, D.; Wang, Shaoming; Qu, W.; Markey, R.; Stain, H.; Morgan, J.; Malinovskiy, D.


    Two Re-Os dating reference material molybdenites were prepared. Molybdenite JDC and molybdenite HLP are from a carbonate vein-type molybdenum-(lead)- uranium deposit in the Jinduicheng-Huanglongpu area of Shaanxi province, China. The samples proved to be homogeneous, based on the coefficient of variation of analytical results and an analysis of variance test. The sampling weight was 0.1 g for JDC and 0.025 g for HLP. An isotope dilution method was used for the determination of Re and Os. Sample decomposition and preconcentration of Re and Os prior to measurement were accomplished using a variety of methods: acid digestion, alkali fusion, ion exchange and solvent extraction. Negative thermal ionisation mass spectrometry and inductively coupled plasma-mass spectrometry were used for the determination of Re and 187Os concentration and isotope ratios. The certified values include the contents of Re and Os and the model ages. For HLP, the Re content was 283.8 ?? 6.2 ??g g-1, 187Os was 659 ?? 14 ng g-1 and the Re-Os model age was 221.4 ?? 5.6 Ma. For JDC, the Re content was 17.39 ?? 0.32 ng g-1, 187Os was 25.46 ?? 0.60 ng g-1 and the Re-Os model age was 139.6 ?? 3.8 Ma. Uncertainties for both certified reference materials are stated at the 95% level of confidence. Three laboratories (from three countries: P.R. China, USA, Sweden) joined in the certification programme. These certified reference materials are primarily useful for Re-Os dating of molybdenite, sulfides, black shale, etc.

  11. A gallery of oil components, their metals and Re-Os signatures (United States)

    Stein, Holly J.; Hannah, Judith L.


    Most sediment-hosted metallic ore deposits are one degree of freedom from hydrocarbon. That is, sulfide fluid inclusions may contain vestiges of travel in tandem with hydrocarbon-bearing fluids. For metallic ore deposits of stated metamorphic and magmatic origin, the degrees of freedom are several times more or, in some cases, no relationship exists. Still, the fetish for stereotyping and classifying ore types into hardline ore deposit models (or hybrid models when the data are wildly uncooperative) impedes our ability to move toward a better understanding of source rock. Fluids in the deeper earth, fluids in the crust, and the extraterrestrial rain of metals provide the Re-Os template for oil. So, too, this combination ultimately drives the composition of many metallic ore deposits. The world of crude oil and its complex history of maturation, migration, mixing, metal-rich asphaltene precipitation, and subsequent mobility of lighter and metal-poor components, is an untapped resource for students of ore geology. In the same way that Mississippi Valley-type lead and zinc deposits are described as the outcome of two converging and mixing fluids (metal-bearing and sulfur-bearing fluids), asphaltene precipitation can be an outcome of a lighter oil meeting and mixing with a heavier one. In the petroleum industry, this can spell economic disaster if the pore-space becomes clogged with a non-producible heavy oil or solid bitumen. In ore geology, sulfide precipitation on loss of permeability may create a Pb-Zn deposit. Petroleum systems provide a gallery of successive time-integrated Re-Os results. Heavy or biodegraded oils, if intersected by lighter oil or gas, can generate asphaltite or tar mats, and release a reservoir of still lighter oil (or gas). During this process there are opportunities for separation of metal-enriched aqueous fluids that may retain an imprint of their earlier hydrocarbon history, ultimately trapped in fluid inclusions. Salinity, temperature and p

  12. Re-Os isotopic composition of the Dongling ⅢCD iron meteorite

    Institute of Scientific and Technical Information of China (English)


    Re,Os concentrations and Os isotopic compositions of the Dongling ⅢCD iron meteorite were determined by N-TIMS technique. The result was compared with that of the other irons and chondrites. The Re and Os concentrations of the Dongling iron meteorite were plotted on the trends of the group ⅢA and ⅣA irons. The Pt-Os relation of the Dongling iron meteorite is similar to that of the group ⅡA irons. That suggests a higher fractionation for the Dongling iron meteorite.

  13. Paleoproterozoic pyrobitumen: Re-Os goechemistry reveals the fate of giant carbon accumulations in Russian Karelia (United States)

    Hannah, J. L.; Stein, H. J.; Yang, G.; Zimmerman, A.


    Carbon-rich pyrobitumen is exposed in abundance in the Onega Basin of Karelia, northwestern Russia - the fossil remains of a giant oil field [1]. The pyrobitumen, locally termed “shungite”, occurs as veins, lenses, and droplets within the Zaonezhskaya and Kondopozhskaya Formations, part of a Paleoproterozoic platform sequence developed on a rifted continental margin. In its purest form, this material approaches 100% C. Less pure pyrobitumen occurs in Corg-rich siltstones, which are intercalated with basaltic flows and sills, including peperites. Locally, the pyrobitumen forms a massive organo-siliceous diapir, cross-cutting the sedimentary section. A Re-Os isochron for six samples of Corg-rich siltstone taken from a mine adit in Shunga village yields a precise age of 2.05 Ga [2], fitting existing constraints for the depositional age. The initial 187Os/188Os ratio given by the isochron for the Shunga adit samples is within uncertainty of chondritic (0.113 at 2.05 Ga), as expected in a restricted rift basin dominated by hydrothermal Os. Re-Os data for samples from ICDP FAR-DEEP drillhole 13A near Shunga village, tell the rest of the story. Eleven ~500 mg samples, drilled from two 3-cm intervals 0.5 m apart in a single core, yield an isochron age of ~1.73 Ga with initial 187Os/188Os = 5. This age is consistent with the latest phase of the Svecofennian orogeny [3], known to have impacted the Onega Basin. Assuming isotopic homogenization (maturation) of the pyrobitumen took place during a relatively brief thermal maximum, the largest control on the present-day 187Os/188Os is the 187Re/188Os. The 187Re/188Os for the 17 siltstone samples analyzed to date range from 280 to 1250. An average 187Re/188Os of 900 will raise the 187Os/188Os from 0.113 to about 5 during the 320 m.y. between deposition (2.05 Ga) and maturation (1.73 Ga) - precisely the value determined by our isochron. Similarly, the lower 187Re/188Os of 280 for three samples of lustrous pyrobitumen from the

  14. Ab initio study of interstitial cluster interaction with Re, Os, and Ta in W (United States)

    Setyawan, Wahyu; Nandipati, Giridhar; Kurtz, Richard J.


    The stability of tungsten self-interstitial atom (SIA) clusters is studied using first-principles methods. Clusters from one to seven SIAs are systematically explored from 1264 unique configurations. Finite-size effect of the simulation cell is corrected based on the scaling of formation energy versus inverse volume cell. Furthermore, the accuracy of the calculations is improved by treating the 5p semicore states as valence states. Configurations of the three most stable clusters in each cluster size n are presented, which consist of parallel [111] dumbbells. The evolution of these clusters leading to small dislocation loops is discussed. The binding energy of size-n clusters is analyzed relative to an n → (n-1) + 1 dissociation and is shown to increase with size. Extrapolation for n > 7 is presented using a dislocation loop model. In addition, the interaction of these clusters with a substitutional Re, Os, or Ta solute is explored by replacing one of the dumbbells with the solute. Re and Os strongly attract these clusters, but Ta strongly repels. The strongest interaction is found when the solute is located on the periphery of the cluster rather than in the middle. The magnitude of this interaction decreases with cluster size. Empirical fits to describe the trend of the solute binding energy are presented.

  15. Guided ion beam and theoretical studies of the reactions of Re+, Os+, and Ir+ with CO (United States)

    Kim, JungSoo; Cox, Richard M.; Armentrout, P. B.


    The kinetic-energy dependences of the reactions M+ + CO where M+ = Re+, Os+, and Ir+ are studied using guided ion-beam tandem mass spectrometry. Formation of both MO+ and MC+ was observed in endothermic processes for all three metals. Modeling of the data provides thresholds that yield 0 K bond dissociation energies (BDEs, in eV) of 4.67 ± 0.09 (Re+-O), 4.82 ± 0.14 (Os+-O), 4.25 ± 0.11 (Ir+-O), 5.13 ± 0.12 (Re+-C), 6.14 ± 0.14 (Os+-C), and 6.58 ± 0.12 (Ir+-C). These BDEs agree well with literature values within experimental uncertainties demonstrating that ground state products are formed for all cases even though some of the reactions are formally spin forbidden. Quantum mechanical calculations at several levels of theory and using several basis sets were performed for MC+ and MO+ (with comparable results taken from the literature in some cases). B3LYP and CCSD(T) calculated ground state BDEs agree reasonably well with experimental values. The ground states in B3LYP and CCSD(T)/CBS calculations are -3Σ (ReC+), 2Δ (OsC+), and +1Σ or 3Δ (IrC+) after including spin-orbit considerations. Relaxed potential energy surfaces (PESs) for the M+ + CO reactions show crossings between surfaces of different spin states such that products can be formed with no barriers in excess of the substantial endothermicities. Unlike results for these metal cations reacting with O2, the kinetic energy dependent cross sections for the formation of MO+ in the M+ + CO reactions exhibit only one feature. Reasons for this differential behavior are discussed in detail.

  16. Pyrite oxidation by thermophilic archaebacteria

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, L.; Olsson, G.; Holst, O.; Karlsson, H.T. (Lund Univ. (Sweden))


    Three species of thermophilic archaebacteria of the genera Sulfolobus (Sulfolobus acidocaldarius and S. solfataricus) and Acidianus (Acidianus brierleyi) were tested for their ability to oxidize pyrite and to grow autotropbically on pyrite, to explore their potential for use in coal desulfurization. Only A. brierleyi was able to oxidize and grow autotrophically on pyrite. Jarosite was formed during the pyrite oxidation, resulting in the precipitation of sulfate and iron. The medium composition affected the extent of jarosite formation.

  17. Re-Os and S isotope evidence for the origin of Platreef mineralization (Bushveld Complex) (United States)

    Yudovskaya, M.; Belousova, E.; Kinnaird, J.; Dubinina, E.; Grobler, D. F.; Pearson, N.


    The Bushveld Complex contains the largest platinum-group element (PGE) deposits of the world that are represented by persistent stratiform reefs highly enriched with PGE with respect to underlying and overlying rocks. New Re-Os isotope and elemental LA MC-ICPMS data on platinum-group minerals (PGM) from the mineralized reefs are presented with implications to correlation between the different segments of the Bushveld Complex and a role of superimposed processes at the reef formation. We analyzed laurite (RuS2), hollingworthite (RhAsS), sperrylite (PtAs2) and Pt-Fe alloys from the Merensky Reef, Pseudoreef and the PGE reef of the Platreef. The measured 187Os/188Os value for Platreef laurite is 0.1751 ± 0.0004 whereas the ratios for sperrylite and hollingworthite range to slightly higher values (0.1713-0.1818 and 0.1744-0.1835 respectively). The observed textures of the analyzed PGM, such as Pt-Fe symplectites in base metal sulfides (BMS), laurite inclusions in chromite and sperrylite rims around sulfide-silicate aggregates, are interpreted as features of primary magmatic crystallization whereas hollingworthite overgrowths and exsolutions in sperrylite are likely to have originated from later solid state transformation or metasomatic processes. The Platreef is a composite sill-like body in the northern limb correlative to the Critical Zone in terms of stratigraphic position, whole-rock geochemistry and isotope characteristics. The pristine magmatic character of sulfides and PGM in the stratiform reefs at the top of the Platreef strongly resembles the style of Merensky Reef mineralization. However, the basal part of the Platreef pyroxenitic sequence is variably contaminated and mineralized with a significant hydrothermal overprint. Sulfides from underlying Lower Zone peridotite yield δ34S values varying from +9‰ to +14.2‰ that are much higher than the values for the overlying Platreef and are a consequence of sulfur assimilation from sedimentary sulfates. The

  18. Re-Os Dating of Galena and Sphalerite from Lead-Zinc Sulfide Deposits in Yunnan Province, SW China

    Institute of Scientific and Technical Information of China (English)

    Yingying Liu; Liang Qi; Jianfeng Gao; Lin Ye; Zhilong Huang; Jiaxi Zhou


    Dating of lead-zinc deposits is of critical importance for better understanding of ore ge-nesis, but has long been a big challenge due to the lack of suitable minerals that can be unequivocally linked to the ore genesis and that can be used for tradition radiometric methods. This kind of deposits have simple mineralogy dominated by galena and sphalerite commonly associated with calcite and oth-er gangue minerals. Both galena and sphalerite have low and high variable Re concentrations and thus Re-Os dating of these minerals have been less promising. In addition, the recovery of Re is extremely low for galena when conventional method was applied, lending additional difficulty in precisely dating galena. In this study, we investigate the recovery of Re using different media for anion exchange sepa-ration and reporte a revised preparation method for Re-Os dating of galena and sphalerite. By using the new protocol, two reliable Re-Os isochron ages of galena and sphalerite from the Fule (20.4±3.2 Ma) and Laochang (308±25 Ma) Pb-Zn deposits in Yunnan Province, SW China, are achieved.

  19. In-situ U-Pb, Hf and Re-Os isotopic analyses of the Xiangshan Ni-Cu-Co deposit in Eastern Tianshan (Xinjiang), Central Asia Orogenic Belt: Constraints on the timing and genesis of the mineralization (United States)

    Han, Chunming; Xiao, Wenjiao; Zhao, Guochun; Ao, Songjian; Zhang, Jien; Qu, Wenjun; Du, Andao


    The timing and genesis of the major Ni-Cu-Co sulfide deposit in the Xiangshan intrusion have been studied based on newly obtained in-situ U-Pb, Hf and Re-Os isotopic analyses. The SIMS U-Pb zircon ages of the gabbro hosting the Ni-Cu-Co sulfide deposit indicate that the Xiangshan intrusion was emplaced at 279.6 ± 1.1 Ma (95% confidence level, MSWD = 1.30, n = 15). On the basis of combined geological and geochronological evidence, we suggest that the Xiangshan and other adjacent Ni-Cu deposits were formed in the same period. Sulphides have low common Os concentrations and high Re/Os ratios, similar to sulphide ores from the Duluth, Sally Malay and Voisey Bay complexes. The Re-Os isotopic data from the disseminated and massive ores from the Xiangshan intrusion do not form a single isochron, as they have different initial Os ratios. The Hf and Os isotopic data suggest that the Xiangshan intrusion and associated Ni-Cu-Co mineralization were derived from crustally contaminated mantle melts. The geochemical data show a tholeiitic affinity and a strong suprasubduction zone signature with negative Nb, Sr, and Ti anomalies similar to N-MORB and E-MORB. We suggest that the mafic-ultramafic rocks and associated Ni-Cu mineralization of the Eastern Tianshan orogen formed in an Alaska-type subduction zone-arc setting. Some diagnostic features of ridge-trench interaction are present in the Chinese East Tianshan orogen (e.g. granites, adakites, high-Mg andesites, near-trench magmatism, Alaskan-type mafic-ultramafic complexes, high-temperature metamorphic belts that prograde rapidly from low-grade belts, and orogenic gold deposits). The above distinctive rock groups are probably related to the same thermal event, ridge subduction, as in the Cenozoic orogen of Alaska. We suggest that ridge subduction is the most plausible mechanism to provide the necessary heat. Ridge subduction provides an important promising model for understanding many aspects of the evolution of the Chinese

  20. New Re-Os Isotopic Constrains on the Formation of the Metalliferous Deposits of the Lower Cambrian Niutitang Formation

    Institute of Scientific and Technical Information of China (English)

    Yong Fu; Lin Dong; Chao Li; Wenjun Qu; Haoxiang Pei; Wenlang Qiao; Bing Shen


    ABSTRACT:The Terreneuvian Epoch (541–521 Ma)is also an important period for metallogenesis in South China, as was represented by the widespread occurrences of Ni-Mo polymetallic layers on the antecedent shallow platform margin and the V-enriched black shales in deeper slope-basin settings. In this study, we have measured Re-Os isochron ages of Ni-Mo polymetallic layers (Songlin, Niuchang, Sancha, Chuanpengwan), V-rich black shales (Bahuang), and non-metalliferous black shales (Shuidong) in the basal Niutitang Formation in Guizhou and Hunan province, South China. The Ni-Mo polymetal-lic layers and V-enriched black shales have similar Re-Os isochron ages, suggesting concurrent deposi-tion of these two types of metalliferous ores. This suggestion is consistent with the traditional strati-graphic correlation by using the nodular phosphorite bed directly underlying these metalliferous layers as a stratigraphic marker. Furthermore, the metalliferous ores and non-metalliferous black shales have similar initial 187Os/188Os ratios of 0.8–0.9, arguing for a dominant seawater origin with minor contri-bution of hydrothermal activity. Furthermore, Re-Os isotopic data also imply that Ni-Mo and V ore might have derived from the same source. We suggest that the spatial distribution of metalliferous ores can be explained by the development of non-sulfidic anoxic-suboxic wedge (NSASW) in the slope-basin and sulfidic wedge in the previous platform margin. Upwelling of deep water first transects the mildly reduced, organic rich NSASW, in which V (V) is reduced to V (IV), and is preferentially removed from seawater by organometallic complex formation. As a result, V-rich black shale deposits in the slope-basin of Yangtze Platform. Further movement of deep water into the sulfidic platform margin results in Ni-Mo polymetallic layer formation.

  1. Re-Os isotope measurements of single sulfide inclusions in a Siberian diamond and its nitrogen aggregation systematics (United States)

    Pearson, D. G.; Shirey, S. B.; Bulanova, G. P.; Carlson, R. W.; Milledge, H. J.


    We have measured the Re-Os isotopic compositions of individual syngenetic sulfide inclusions from three different growth zones within a central cross section plate cut from a single Siberian diamond. Individual sulfides in their diamond host were isolated by laser cutting. The sulfides, and hence the different growth zones of the diamond have been suggested to differ in age by up to 2 Ga on the basis of their Pb isotope compositions. Re-Os model ages of the four inclusions range from 3.1 ± 0.3 to 3.5 ± 0.3 Ga and suggest a Middle Archaean age for the diamond. A sulfide inclusion in the rim of the diamond is very different in elemental composition from those of the core and intermediate zones. It is enriched in Os, Re, Pb, and Zn and has more radiogenic Os and Pb isotopes. The inclusion is connected to the surface of the diamond by a healed crack, revealed by cathodoluminescence. The compositional distinction may be caused either by postformational interaction between an ancient sulfide and a fluid, possibly at the time of kimberlite eruption, or later stage growth of new diamond plus sulfide. Such chemical complexities, and the presence of healed fractures within the host diamond, emphasize the desirability of analyzing individual inclusions from well-characterized diamonds if isotope data for inclusions are to be better understood. Nitrogen contents and aggregation state in the core and intermediate zone of the host diamond closely approximate theoretically calculated isotherms based on consideration of experimentally determined nitrogen aggregation kinetics. The nitrogen content of the rim diamond is too low to obtain spectra that allow accurate deconvolution of relative aggregation levels for use in residence time calculations. The aggregation state of nitrogen in the core and intermediate growth zones is compatible with a long, ca. 3 Ga mantle residence time at normal lithospheric temperatures. The similarity of the sulfide inclusion Re-Os model ages to the

  2. Pyrite oxidation by microbial consortia (United States)

    Bostick, B. C.; Revill, K. L.; Doyle, C.; Kendelewicz, T.; Brown, G. E.; Spormann, A. M.; Fendorf, S.


    Acid mine drainage (AMD) is formed through pyrite oxidation, which produces acidity and releases toxic metals associated with pyrite and other sulfide minerals. Microbes accelerate pyrite oxidation markedly, thereby playing a major role in the production of AMD. Here, we probe pyrite oxidation by consortia of Thiobacillus ferrooxidans and thiooxidans using surface-sensitive photoelectron spectroscopy and X-ray absorption spectroscopy and compare them with surfaces oxidized through chemical and single species cultures. Microbial oxidation resulted in the formation of distinct oxidized surface species distributed non-uniformly over the pyrite surface; consortia produced a surface both more heterogeneous and more oxidized. In contrast, chemical oxidation proceeds without the build-up of passivating oxidation products. Surface morphology was not correlated with sites of nucleation or oxidation in any obvious manner. These results demonstrate that microbial oxidation occurs through a similar mechanism to chemical oxidation, but that the presence of complex microbial communities may impact the manner by which pyrite oxidation proceeds.

  3. U-Pb, Re-Os and Ar-Ar dating of the Linghou polymetallic deposit, Southeastern China: Implications for metallogenesis of the Qingzhou-Hangzhou metallogenic belt (United States)

    Tang, Yanwen; Xie, Yuling; Liu, Liang; Lan, Tingguan; Yang, Jianling; Sebastien, Meffre; Yin, Rongchao; Liang, Songsong; Zhou, Limin


    The Qingzhou-Hangzhou metallogenic belt (QHMB) in Southeastern China has gained increasingly attention in recent years. However, due to the lack of reliable ages on intrusions and associated deposits in this belt, the tectonic setting and metallogenesis of the QHMB have not been well understood. The Linghou polymetallic deposit in northwestern Zhejiang Province is one of the typical deposits of the QHMB. According to the field relationships, this deposit consists of the early Cu-Au-Ag and the late Pb-Zn-Cu mineralization stages. Molybdenite samples with a mineral assemblage of molybdenite-chalcopyrite-pyrite ± quartz are collected from the copper mining tunnel near the Cu-Au-Ag ore bodies. Six molybdenite samples give the Re-Os model ages varying from 160.3 to 164.1 Ma and yield a mean age of 162.2 ± 1.4 Ma for the Cu-Au-Ag mineralization. Hydrothermal muscovite gives a well-defined Ar-Ar isochron age of 160.2 ± 1.1 Ma for the Pb-Zn-Cu mineralization. Three phases of granodioritic porphyry have been distinguished in this deposit, and LA-ICP-MS zircon U-Pb dating shows that they have formed at 158.8 ± 2.4 Ma, 158.3 ± 1.9 Ma and 160.6 ± 2.1 Ma, comparable to the obtained ages of the Cu-Au-Ag and Pb-Zn-Cu mineralization. Therefore, these intrusive rocks have a close temporal and spatial relationship with the Cu-Au-Ag and Pb-Zn-Cu ore bodies. The presences of skarn minerals (e.g., garnet) and vein-type ores, together with the previous fluid inclusion and H-O-C-S-Pb isotopic data, clearly indicate that the Cu-Au-Ag and Pb-Zn-Cu mineralization are genetically related to these granodiorite porphyries. This conclusion excludes the possibility that this deposit is of ;SEDEX; type and formed in a sag basin of continental rifts setting as previously proposed. Instead, it is proposed that the Linghou polymetallic and other similar deposits in the QHMB, such as the 150-160 Ma Yongping porphyry-skarn Cu-Mo, Dongxiang porphyry? Cu, Shuikoushan/Kangjiawang skarn Pb

  4. Methods of isotopic geochronology (United States)

    Gorokhov, I. M.; Levchenkov, O. A.

    Papers are presented on such topics as the age of the chemical elements; the age of meteorites, the moon, and the earth; isotopic ages of the most ancient terrestrial formations; and the Archean evolution of Enderby Land in the Antarctic as evidenced by isotopic dating. Consideration is also given to a uranium-lead geochronology technique for investigating Precambrian ore deposits, a Pb-Pb technique of zircon dating, and the potentials and limitations of Sm-Nd geochronology.

  5. Pyritization in the Gaojiashan Biota

    Institute of Scientific and Technical Information of China (English)

    CAI YaoPing; HUA Hong


    The Late Sinian (Ediacaran) Gaojiashan Biota was a soft-bodied fossil-Lagerst(a)tte dominated by substantial pyritized, three-dimensionally preserved tubular and conotubular fossils. Soft-tissue pyritization is extremely scarce in the fossil records, especially in the Precambrian, therefore it has very important and unique significance for the study of pyritization in the Gaojiashan Biota. Early pyritization played a pivotal role in the fossil preservation and two main factors ensured the successful pyritization of the fossils, namely rapid burial and permineralization. The former was controlled by secular storm deposition, and the latter was achieved by sufficient supply of available iron from sediments. SEM data of Conotubus demonstrate two types of preservation of the tubes (defined as type A and type B, respectively). In type A, pyritization took place relatively earlier and completely preserved both tube wall and coelom, but no detailed structure. While in type B, pyritization took place somewhat later and preserved the integrated tube wall, but partially the coelom. The size frequency distribution of the pyrite framboids suggests that pyritization took place in two different environments with entire different oxygen content.

  6. Re-Os dating of Mo-bearing black shale of the Laoyaling deposit, Tongling, Anhui Province, China

    Institute of Scientific and Technical Information of China (English)

    YANG Gang; CHEN Jiangfeng; DU Andao; QU Wenjun; YU Gang


    Laoyaling is a typical stratiform deposit in the Tongling district and the molybdenum orebody is hosted by black shale of the Dalong Formation of the Upper Permian system. Eight black shale samples from the Laoyaling Mo orebody were dated by Re-Os technique using ICP-MS,which give an isochron age of 234.2±7.3 Ma with an initial 187Os/188Os ratio of 1.37±0.39. The apparent Re-Os age is a few million years younger than the depositional age of the Late Permian. The young isochron age may be caused by the later hydrothermal disturbance or mass fractionation during ICP-MS measurement. However, the obtained isochron age is close to the depositional age and far earlier than those of the Late Yanshanian intrusions. It suggests that the Mo ore of the Laoyaling deposit is sedimentary in origin and not related to the Late Yanshanian magmatism. Black shales of the Upper Permian are distributed widely in the Mid-Lower Yangtze region, our result is important for understanding the ore-forming processes in the region and broadens the exploration target.

  7. Re-Os (ICP-MS) dating of the massive sulfide ores from the Jinchuan Ni-Cu-PGE deposit

    Institute of Scientific and Technical Information of China (English)

    YANG Gang; DU Andao; LU Jiren; QU Wenjun; CHEN Jiangfeng


    Massive sulfide ore from the Jinchuan Ni-Cu-PGE deposit was dated by Re-Os technique using Carius Tube digestion, Os distillation, Re extraction by acetone and ICP-MS measurement. An isochron giving an age of 833 ± 35 Ma, initial 187Os/188Os ratio of 0.279 ± 0.018 (MSWD = 1.7) and γOs = 130 ± 15 is obtained. The Re-Os age obtained agrees, within analytical uncertainties, with previous SHRIMP zircon U-Pb age of 827 ± 8 Ma (n=5, MSWD = 4.3). The result suggests that the deposit was formed at Neoproterozoic and that the formation of the Jinchuan Ni-Cu-PGE sulfide deposit may be closely related to the plume activity, which were attributed to the breakup of the Rodinia supercontinent. The high γOs of the massive ores suggests that crustal material was involved in the formation of the Jinchuan deposit, however, the quantity of the added crustal material is less than 10%.

  8. Neoproterozic Re-Os age of a sulfide inclusion in a superdeep diamond: Implications for mantle convection beneath Juina, Brazil (United States)

    Shirey, S. B.; Smit, K.; Nestola, F.; Steele, A.; Bulanova, G.; Smith, C. B.


    Diamonds from the Juina area Brazil have long been known for their sublithospheric or superdeep (e.g. from depths of 300-800 km) origins. These diamonds have yielded new information about high pressure mantle mineralogy, deep crustal recycling, diamond source fluids, and mantle transition zone water content. A type II (low N) diamond (sample J1) from the 93.1±1.5 myr old (Heaman 7IKC 1998 ) Collier 4 kimberlite was studied previously (Walter et al. Nature 2008; Bulanova et al. CMP 2010) as part of a larger suite of eclogitic-composition, inclusion-bearing type II Collier 4 diamonds with complex internal growth structure. Major and trace element analyses of mineral inclusions in these diamonds include Ca-Ti-Si perovskite, Ca-rich majoritic-garnet, clinopyroxene, olivine, jeffbenite, minerals with stoichiometries of CAS and K-hollandite phases, SiO2, FeO, native iron, low-Ni sulfides, and Ca-Mg-carbonate. The C isotopic compositions of the diamond hosts range from a δ13C of -25 to -5‰ ( J1 being -15‰). Collier 4 diamonds have been interpreted to crystallize from carbonatitic melts derived from the recycling of oceanic lithosphere at TransitionZone depths (Walter et al. Nature 2008; Bulanova et al. CMP 2010). A rare Fe-sulfide inclusion in the core of diamond J1 has been dated with the Re-Os system in order to provide age and compositional constraints on the proposed oceanic slab recycling. The rim of J1 contained inclusions of Ca-Ti-Si perovskite that yielded U-Pb age of 101±7 Ma and eclogitic (low Cr, high Ca) majorite that yielded formation pressures (Si - Al+Cr geobarometry) >8 GPa (Bulanova et al. CMP 2010). The Fe-sulfide analyzed was low Ni pyrrhotite determined to be Fe10S11 of a rare 11T polytype by single-crystal X-ray diffraction. The 27 ug interior pyrrhotite had a high Re/Os (187Re/188Os = 854) typical of MORB (Re/Os ~100) and radiogenic Os isotopic composition (187Os/188Os = 8.50±1.38) that yields a 602±16 Ma model age relative to normal mantle

  9. Pyrite oxidation by sulfolobus acidocaldarius

    Energy Technology Data Exchange (ETDEWEB)

    Tobita, M.; Yokozeki, M.; Nishikawa, N.; Kawakami, Y. (Institute of Research and Innovation, Kashiwa (Japan). Dept. of Biotechnology)


    Two strains of Sulfolobus acidocaldarius, a thermoacidophilic archaebacterium, were examined for their pyrite-oxidizing ability. S. acidocaldarius ATCC 33909 was shown to possess iron-oxidizing activity by ferrous sulfate oxidizing experiments, but S. acidocaldarius No. 7 did not have it. Pyrite-oxidizing rate of S. acidocaldarius ATCC 33909 was 1.6-fold higher than that of strain 7 though they had a similar level of self-oxidizing ability. These results show that the iron-oxidizing activity accelerates pyrite oxidation.

  10. Re-Os dating of sulphide inclusions zonally distributed in single Yakutian diamonds: Evidence for multiple episodes of Proterozoic formation and protracted timescales of diamond growth (United States)

    Wiggers de Vries, D. F.; Pearson, D. G.; Bulanova, G. P.; Smelov, A. P.; Pavlushin, A. D.; Davies, G. R.


    The timing of diamond formation in the Siberian lithospheric mantle was investigated by Re-Os isotope dating of sulphide inclusions from eclogitic and lherzolitic diamonds from the Mir, 23rd Party Congress and Udachnaya kimberlite pipes in Yakutia. The diamonds contained multiple sulphide inclusions distributed over their core-to-rim zones. Cathodoluminescence, carbon isotope and nitrogen aggregation studies demonstrate that the diamonds are zoned and that the distinct zones are associated with different diamond growth episodes. There are coherent relationships between carbon isotope composition, nitrogen concentration and aggregation state of the diamond hosts, and major and trace element compositions, Re-Os compositions and initial Os isotope ratios of the included sulphides. This suggests that the different diamond and sulphide populations formed at different times from fluids/melts with different chemical compositions. Based on the Re-Os isochron ages and the nitrogen aggregation states we conclude that the sulphides are co-genetic with their diamond hosts.

  11. Evaluating Re-Os systematics in organic-rich sedimentary rocks in response to petroleum generation using hydrous pyrolysis experiments (United States)

    Rooney, Alan D.; Selby, David; Lewan, Michael D.; Lillis, Paul G.; Houzay, Jean-Pierre


    Successful application of the 187Re-187Os geochronometer has enabled the determination of accurate and precise depositional ages for organic-rich sedimentary rocks (ORS) as well as establishing timing constraints of petroleum generation. However, we do not fully understand the systematics and transfer behaviour of Re and Os between ORS and petroleum products (e.g., bitumen and oil). To more fully understand the behaviour of Re-Os systematics in both source rocks and petroleum products we apply hydrous pyrolysis to two immature hydrocarbon source rocks: the Permian Phosphoria Formation (TOC = 17.4%; Type II-S kerogen) and the Jurassic Staffin Formation (TOC = 2.5%; Type III kerogen). The laboratory-based hydrous pyrolysis experiments were carried out for 72 h at 250, 300, 325 and 350 °C. These experiments provided us with whole rock, extracted rock and bitumen and in some cases expelled oil and asphaltene for evaluation of Re-Os isotopic and elemental abundance. The data from these experiments demonstrate that the majority (>95%) of Re and Os are housed within extracted rock and that thermal maturation does not result in significant transfer of Re or Os from the extracted rock into organic phases. Based on existing thermodynamic data our findings suggest that organic chelating sites have a greater affinity for the quadravalent states of Re and Os than sulphides. Across the temperature range of the hydrous pyrolysis experiments both whole rock and extracted rock 187Re/188Os ratios show small variations (3.3% and 4.7%, for Staffin, respectively and 6.3% and 4.9% for Phosphoria, respectively). Similarly, the 187Os/188Os ratios show only minor variations for the Staffin and Phosphoria whole rock and extracted rock samples (0.6% and 1.4% and 1.3% and 2.2%). These isotopic data strongly suggest that crude oil generation through hydrous pyrolysis experiments does not disturb the Re-Os systematics in ORS as supported by various studies on natural systems. The elemental

  12. Palynology, geochemistry and Re-Os age of the Lower-Middle Pennsylvanian stage boundary, central Appalachian basin, USA (United States)

    Geboy, N.; Tripathy, G. R.; Ruppert, L. F.; Eble, C. F.; Blake, B. M.; Hannah, J. L.; Stein, H. J.


    The central Appalachian basin (CAB) in the eastern United States contains complicated sedimentary sequences often with thin and discontinuous strata. As an economically important coal-producing region, the basin's architectural framework and depositional history are important to understand. Typically, eustatic marine incursions, marked with black shale deposits, are used for basin-wide correlation. The Betsie Shale Member of the Kanawha Formation represents one of these relatively thick and laterally extensive marine zones. This study examines the palynoflora of the Matewan coalbed, which conformably underlies the Betsie, in the context of a new Re-Os date for the Betsie Shale Member and additional geochemical measures. At its base, the Matewan contains abundant lycopsid tree spores, indicative of a submerged, flooded paleomire. Upsection, biodiversity increases to include small fern and calamite spores as well as cordaite pollen. Combined with an observed increase of inertinite, the diversification of palynoflora suggests surficial peat exposure and drying out of the paleomire. A S-rich (28 wt. %) shaley parting separates these lower and upper benches of the Matewan and may represent an initial marine pulse prior to the glacioeustatic incursion that ultimately flooded the Matewan and deposited the overlying Betsie Shale. The Betsie is organic-rich (3.05 - 4.89 wt. % TOC) with Re and Os content ranging from 320 - 1,200 ppb and 1.5 - 5.3 ppb, respectively. The highly enriched Re values result in notably high parent:daughter ratios (187Re/188Os = 3,644 - 5,737). The Re-Os isotopic data yield a Model 1 age of 323 ± 7.8 Ma (n = 7; MSWD = 0.63) with evidence that the true age lies closer to the younger end of the uncertainty. This age is consistent with previous paleontologic-based interpretations but represents the first directly measured radiometric date for the Betsie. An absolute age for the Betsie is a critical result, as the member is correlated with units in

  13. Ab initio calculations of mechanical properties of bcc W-Re-Os random alloys: effects of transmutation of W (United States)

    Li, Xiaojie; Schönecker, Stephan; Li, Ruihuan; Li, Xiaoqing; Wang, Yuanyuan; Zhao, Jijun; Johansson, Börje; Vitos, Levente


    To examine the effect of neutron transmutation on tungsten as the first wall material of fusion reactors, the elastic properties of W1-x-y  Re x  Os y (0  ⩽  x, y  ⩽  6%) random alloys in body centered cubic (bcc) structure are investigated systematically using the all-electron exact muffin-tin orbitals (EMTO) method in combination with the coherent-potential approximation (CPA). The calculated lattice constant and elastic properties of pure W are consistent with available experiments. Both Os and Re additions reduce the lattice constant and increase the bulk modulus of W, with Os having the stronger effect. The polycrystalline shear modulus, Young’s modulus and the Debye temperature increase (decrease) with the addition of Re (Os). Except for C 11, the other elastic parameters including C 12, C 44, Cauchy pressure, Poisson ratio, B/G, increase as a function of Re and Os concentration. The variations of the latter three parameters and the trend in the ratio of cleavage energy to shear modulus for the most dominant slip system indicate that the ductility of the alloy enhances with increasing Re and Os content. The calculated elastic anisotropy of bcc W slightly increases with the concentration of both alloying elements. The estimated melting temperatures of the W-Re-Os alloy suggest that Re or Os addition will reduce the melting temperature of pure W solid. The classical Labusch-Nabarro model for solid-solution hardening predicts larger strengthening effects in W1-y  Os y than in W1-x  Re x . A strong correlation between C‧ and the fcc-bcc structural energy difference for W1-x-y  Re x  Os y is revealed demonstrating that canonical band structure dictates the alloying effect on C‧. The structural energy difference is exploited to estimate the alloying effect on the ideal tensile strength in the [0 0 1] direction.

  14. Re-Os Dating of the Pulang Porphyry Copper Deposit in Zhongdian, NW Yunnan, and Its Geological Significance

    Institute of Scientific and Technical Information of China (English)

    ZENG Pusheng; HOU Zengqian; WANG Haiping; QU Wenjun; MENG Yifeng; YANG Zhusen; LI Wenchang


    The Pulang porphyry copper deposit is located in the Zhongdian island arc belt, NW Yunnan, in the central part of the Sanjiang area, SW China, belonging to the southern segment of the Yidun island arc belt on the western margin of the Yangtze Platform. In the Yidun island arc, there occur well-known "Gacun-style" massive sulfide deposits in the northern segment and plenty of porphyry copper deposits in the southern segment, of which the Pulang porphyry copper deposit is one of the representatives. Like the Yulong porphyry copper deposit, this porphyry copper deposit is also one of the most important porphyry copper deposits in the eastern Qinghai-Tibet Plateau. But it is different from other porphyry copper deposits in the eastern Qinghai-Tibet Plateau (e.g. those in the Gangdise porphyry copper belt and Yulong porphyry copper belt) in that it formed in the Indosinian period, while others in the Himalayan period. Because of its particularity among the porphyry copper deposits of China, this porphyry copper deposit is of great significance for the study of the basic geology and the evaluation and prediction of mineral resources in the Zhongdian island arc belt.However, no accurate chronological data are available for determining the timing of mineralization of the porphyry copper deposit. By field observation in the study area and Re-Os dating of molybdenite and K-Ar dating of hydrothermal minerals and whole rock from the typical geological bodies, the timing of mineralization of the porphyry copper deposit has systematically been determined for the first time. The K-Ar age for the hydrothermal mineralization of biotite-quartz monzonitic porphyry that has undergone patassic silicate (biotite and K-feldspar) alteration ranges from 235.4±2.4 to 221.5±2.0 Ma and the Re-Os age for molybdenite in the quartz-molybdenite stage is ~213±3.8 Ma. These data are very close to each other, suggesting that the ore-forming processes of the Pulang porphyry copper deposit was

  15. Re-Os isotopic systematics of primitive lavas from the Lassen region of the Cascade arc, California (United States)

    Borg, L.E.; Brandon, A.D.; Clynne, M.A.; Walker, R.J.


    Rhenium-osmium isotopic systematics of primitive calc-alkaline lavas from the Lassen region appear to be controlled by mantle wedge processes. Lavas with a large proportion of slab component have relatively low Re and Os abundances, and have radiogenic Os and mid ocean ridge basalt-like Sr and Pb isotopic compositions. Lavas with a small proportion of slab component have higher Re and Os elemental abundances and display mantle-like Os, Sr, Nd, and Pb isotopic compositions. Assimilation with fractional crystallization can only generate the Re-Os systematics of the Lassen lavas from a common parent if the distribution coefficient for Re in sulfide is ~40-1100 times higher than most published estimates and if most incompatible element abundances decrease during differentiation. High Re/Os ratios in mid ocean ridge basalts makes subducted oceanic crust a potential source of radiogenic Os in volcanic arcs. The slab beneath the southernmost Cascades is estimated to have 187Os/188Os ratios as high as 1.4. Mixing between a slab component and mantle wedge peridotite can generate the Os isotopic systematics of the Lassen lavas provided the slab component has a Sr/Os ratio of ~7.5X105 and Os abundances that are 100-600 times higher than mid ocean ridge basalts. For this model to be correct, Os must be readily mobilized and concentrated in the slab component, perhaps as a result of high water and HCl fugacities in this subduction environment. Another possible mechanism to account for the correlation between the magnitude of the subduction geochemical signature and Os isotopic composition involves increasing the stability of an Os-bearing phase in mantle wedge peridotites as a result of fluxing with the slab component. Melting of such a source could yield low Os magmas that are more susceptible to crustal contamination, and hence have more radiogenic Os isotopic compositions, than magmas derived from sources with a smaller contribution from the slab. Thus, the addition of the

  16. Ab initio calculations of mechanical properties of bcc W-Re-Os random alloys: effects of transmutation of W. (United States)

    Li, Xiaojie; Schönecker, Stephan; Li, Ruihuan; Li, Xiaoqing; Wang, Yuanyuan; Zhao, Jijun; Johansson, Börje; Vitos, Levente


    To examine the effect of neutron transmutation on tungsten as the first wall material of fusion reactors, the elastic properties of W1-x-y  Re x  Os y (0  ⩽  x, y  ⩽  6%) random alloys in body centered cubic (bcc) structure are investigated systematically using the all-electron exact muffin-tin orbitals (EMTO) method in combination with the coherent-potential approximation (CPA). The calculated lattice constant and elastic properties of pure W are consistent with available experiments. Both Os and Re additions reduce the lattice constant and increase the bulk modulus of W, with Os having the stronger effect. The polycrystalline shear modulus, Young's modulus and the Debye temperature increase (decrease) with the addition of Re (Os). Except for C 11, the other elastic parameters including C 12, C 44, Cauchy pressure, Poisson ratio, B/G, increase as a function of Re and Os concentration. The variations of the latter three parameters and the trend in the ratio of cleavage energy to shear modulus for the most dominant slip system indicate that the ductility of the alloy enhances with increasing Re and Os content. The calculated elastic anisotropy of bcc W slightly increases with the concentration of both alloying elements. The estimated melting temperatures of the W-Re-Os alloy suggest that Re or Os addition will reduce the melting temperature of pure W solid. The classical Labusch-Nabarro model for solid-solution hardening predicts larger strengthening effects in W1-y  Os y than in W1-x  Re x . A strong correlation between C' and the fcc-bcc structural energy difference for W1-x-y  Re x  Os y is revealed demonstrating that canonical band structure dictates the alloying effect on C'. The structural energy difference is exploited to estimate the alloying effect on the ideal tensile strength in the [0 0 1] direction.

  17. Ab initio study of interstitial cluster interaction with Re, Os, and Ta in W

    Energy Technology Data Exchange (ETDEWEB)

    Setyawan, Wahyu; Nandipati, Giridhar; Kurtz, Richard J.


    The stability of tungsten self-interstitial atom (SIA) clusters is studied using first-principles methods. Clusters from one to seven SIAs are systematically explored from 1264 unique configurations. Finite-size effect of the simulation cell is corrected based on the scaling of formation energy versus inverse volume cell. Furthermore, the accuracy of the calculations is improved by treating the 5p semicore states as valence states. Configurations of the three most stable clusters in each cluster size n are presented, which consist of parallel [111] dumbbells. The evolution of these clusters leading to small dislocation loops is discussed. The binding energy of size-n clusters is analyzed relative to an n → (n-1) + 1 dissociation and is shown to increase with size. Extrapolation for n > 7 is presented using a dislocation loop model. In addition, the interaction of these clusters with a substitutional Re, Os, or Ta solute is explored by replacing one of the dumbbells with the solute. Re and Os strongly attract these clusters, but Ta strongly repels. The strongest interaction is found when the solute is located on the periphery of the cluster rather than in the middle. The magnitude of this interaction decreases with cluster size. Empirical fits to describe the trend of the solute binding energy are presented.

  18. The neutron capture cross sections of 186;187;188 Os and their application to Re/Os cosmochronometer

    CERN Document Server

    Fujii, Kaori; Mastinu, P; Milazzo, P M


    The aim of this thesis is a fine determination of 186;187;188Os neutron capture cross sections, in order to remove principal nuclear physics uncertainties on the age of the universe determined using the Re/Os cosmochronometer. A general introduction including stellar nucleosynthesis, nuclear cosmochronometry,available neutron facilities and neutron reaction features is given. Dedicated measurements of the 186;187;188Os capture cross sections have been performed at the CERN neutron time-of- ight facility, n TOF, in the neutron energy range from 1 eV up to 1 MeV. The details of the measurement and the data treatment are reported. Using obtained capture yields, resolved resonance region analysis is completed. Resonance parameters have been extracted from a full R-matrix fit. A statistical analysis has been performed and the related averaged resonance parameters are derived. This information is crucial for a complete understanding and modelling in terms of the Hauser-Feshbach statistical model of the capture and ...

  19. In situ Re-Os isotope ages of sulfides in Hannuoba peridotitic xenoliths: Significance for the frequently-occurring mantle events beneath the North China Block

    Institute of Scientific and Technical Information of China (English)


    In situ Re-Os isotopes of sulfides in peridotitic xenoliths from Cenozoic Hannuoba basalts were analyzed by LAM-MC-ICPMS. The suifides developed two types of occurrences including silicate-enclosed and interstitial. In the enclosed sulfides, 187Os/188Os vary from 0.1124 to 0.1362 and 187Re/188Os from 0.0026 to 1.8027. In the interstitial ones, 187Os/188Os have a range from 0.1174 to 0.1354 and 187Re/188Os from 0.0365 to 1.4469. The oldest age, calculated by TRD for the enclosed sulfides, is 2.1 Ga. An isochron age of 2.3±1.2 Ga is obtained by five grains of enclosed sulfides and primitive mantle. The sulfides used have lower Re-Os isotopic ratio than primitive mantle. Meanwhile, an isochron age of 645±225 Ma is given by all interstitial sulfides and the enclosed sulfides with higher Re-Os isotopic ratio due to Re addition after mantle formation. In addition, the model age of 1.3 Ga recorded by one interstitial sulfide, having similar TDM and TRD, should be meaningful to deep thermal event. The coexistence of different ages, revealed by in situ Re-Os isotope, indicates frequently-occurring mantle events beneath Hannuoba area.

  20. The 982 Ma Re-Os age of copper-nickel sulfide ores in the Baotan area, Guangxi and its geological significance

    Institute of Scientific and Technical Information of China (English)

    毛景文; 杜安道


    Re-Os dating on copper-nickel sulfide ores from the Baotan area, Guangxi, yielded an ore-forming age of 982±21 Ma(2σ), which demonstrates that copper-nickel sulfide deposits and their related mafic-ultramafic rocks occurred in the same period of time with the ophiolites in northeastern Jiangxi. Both of them are the products of collision-convergence between the Cathaysian plate and Yangtze plate and the subsequent extensional environment. Calculation of the γOs of the 982 Ma copper-nickel sulfide ores and its correlation with Re/Os indicate that injection-type massive ores display lower γOs values(-15.6 to -8.2) and lower Re/Os ratios(0.32 to 0.43), while basal liquation-type ores have γOs= -27.9 to -7.3 and Re/Os=5.36 to 11.24. This suggests that these copper-nickel sulfide ores and their related mafic-ultramafic rocks were derived from a Re-depleted mantle source and that contamination with some crustal material occurred during their intrusion.

  1. Oxidation of pyrite: Consequences and significance

    Directory of Open Access Journals (Sweden)

    Dimitrijević Mile D.


    Full Text Available This paper presents the most important studies on the oxidation of pyrite particularly in aqueous solutions. The consequences of pyrite oxidation was examined, as well as its importance, from both the technical-technological and environmental points of view. The oxidation of pyrite was considered in two parts. The spontaneous oxidation of pyrite in nature was described in the first part, with this part comprising pyrite oxidation in deposits depots and mines. It is explained how way natural electrochemical processes lead to the decomposition of pyrite and other minerals associated with pyrite. The oxidation of pyrite occurring during technological processes such as grinding, flotation and leaching, was shown in the second part. Particular emphasis was placed on the oxidation of pyrite during leaching. This part includes the leaching of sulphide and oxide ores, the leaching of pyrite coal and the leaching of refractory gold-bearing ores (pressure oxidation, bacterial oxidation, oxidation by means of strong oxidants and the electrolysis of pyrite suspensions. Various mechanisms of pyrite oxidation and of the galvanic interaction of pyrite with other sulphide minerals are shown.

  2. Pyrite synthesis via polysulfide compounds (United States)

    Luther, George W., III


    The reactions of Fe(II) and Fe(III) solutions with polysulfide solutions prepared from freshly synthesized Na 2S x ( x = 2, 4, 5) were studied at 25 and 100°C over the pH range 5.5 to 8. Direct and instantaneous pyrite formation was not observed in any reaction. High temperature reactions are nearly quantitative over periods of four hours with Fe(II) and polysulfide solutions. The rate of reaction at room temperature is comparable to that found by RICKARD (1975), and the observations reported here are in agreement with his mechanism of pyrite formation. Based on the polarographic results of these reactions and previous work, a refinement of the mechanism which includes dissolved iron sulfide complexes is proposed. Every reaction of equimolar amounts of polysulfide and Fe(II) gave the kinetic product "FeS" (an example of the Ostwald step rule). Polarographic results demonstrate that the "FeS" initially formed consists of (1) a complex of the form Fe(SH) + and (2) solid FeS. When excess polysulfide is present, a complex of form [Fe(SH) S x] - is present. This complex should readily allow for (1) the reduction of polysulfide by sulfide which produces S 22- in unprotonated form, and (2) the change of Fe(II) from high spin to low spin during the formation of pyrite. The reduction of polysulfide by sulfide was proposed by RICKARD (1975), but at the pH of the solutions studied herein, S 22- in solution should be protonated. The 22- ion is critical in the formation and structure of pyrite ( TOSSEL et al., 1981). The proposed complex allows for a cyclic intermediate which cleaves the reacting polysulfide to form S 22- unprotonated. As this process occurs, there is a change in the spin state of the Fe(II) from the high spin t 2g4e g2 to the low spin t 2g6 state which is an electron configuration exhibiting kinetic inertness. On change of the Fe(II) spin state, the complex irreversibly decomposes to form pyrite. The complex may be a cluster complex containing two or more

  3. Pyritized ooids from the Arabian Sea basin

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, P.S.; Rao, Ch.M.; Reddy, N.P.C.

    . Occurrence of pyrite at turbidite intervals suggests that pyritization in high organic carbon and H2S abundant environments was mainly controlled by the supply of reactive iron. From the distribution of pyrite in the core it is inferred that reactive iron...

  4. PGE geochemistry and Re Os dating of massive sulfide ores from the Baimazhai Cu Ni deposit, Yunnan province, China (United States)

    Sun, Xiaoming; Wang, Shengwei; Sun, Weidong; Shi, Guiyong; Sun, Yali; Xiong, Dexin; Qu, Wenjun; Du, Andao


    The Baimazhai deposit in Yunnan Province is one of the largest Cu-Ni sulfide deposits hosted in mafic-ultramafic intrusions in China. Concentrations of platinum-group elements (PGE) in massive sulfide ores and host rocks from Baimazhai were determined by using inductively coupled plasma mass spectrometry (ICP-MS) following nickel sulfide fire assay pre-concentration. The results show that the total PGE (ΣPGE) are quite low, decreasing gradually from central massive ores (78.2-556 ppb) to olivine pyroxenite (0.472-67.0 ppb), gabbro (0.847 ppb) and, websterite (0.76-0.809). The intruded lamprophyre dykes also show low ΣPGE (2.98-4.07 ppb). The ΣPGE exhibit obvious positive correlations with Au, Ni and Cu contents. Primitive mantle normalized PGE patterns of the massive Cu-Ni ores are of the Pt-Pd type with relatively steep and trough-like patterns, which are similar to those of the host rocks. In addition, the Pt/Pd and Cu/Pd ratios of the massive sulfide ores are similar to those of olivine pyroxenite, gabbro and websterite. These characteristics suggest that sulfides in the massive ores are of magmatic origin, co-genetic with their host rocks. The relatively high Pt/Pd ratios of the Baimazhai massive sulfide ores (averaging 0.83) and their host rocks imply that the Baimazhai sulfides formed in a single sulfide saturation event, but not through multiple sulfide injections. High Ir contents (0.77-5.52 ppb, averaging 2.35 ppb) and dramatically variable Pd/Ir ratios (4.76-296, averaging 138) of the massive sulfide ores suggest that the Baimazhai sulfide ores might have suffered significant late stage hydrothermal alteration. The Baimazhai massive sulfide ores yield a Re-Os isochron age of 259 ± 20 Ma (MSWD = 0.025), which is the same as the major eruption stage of the Emeishan large igneous province and the Baimazhai intrusion, further supporting their magmatic origin. The initial 187Os/ 188Os value of 0.456 ± 0.026 indicates that crustal contamination has played

  5. Re-Os isotope evidence from Mesozoic and Cenozoic basalts for secular evolution of the mantle beneath the North China Craton (United States)

    Huang, Feng; Xu, Ji-Feng; Liu, Yong-Sheng; Li, Jie; Chen, Jian-Lin; Li, Xi-Yao


    The mechanism and process of lithospheric thinning beneath the North China Craton (NCC) are still debated. A key criterion in distinguishing among the proposed mechanisms is whether associated continental basalts were derived from the thinning lithospheric mantle or upwelling asthenosphere. Herein, we investigate the possible mechanisms of lithospheric thinning based on a systematic Re-Os isotopic study of Mesozoic to Cenozoic basalts from the NCC. Our whole-rock Re-Os isotopic results indicate that the Mesozoic basalts generally have high Re and Os concentrations that vary widely from 97.2 to 839.4 ppt and 74.4 to 519.6 ppt, respectively. They have high initial 187Os/188Os ratios ranging from 0.1513 to 0.3805, with corresponding variable γOs(t) values (+20 to +202). In contrast, the Re-Os concentrations and radiogenic Os isotope compositions of the Cenozoic basalts are typically lower than those of the Mesozoic basalts. The lowest initial 187Os/188Os ratios of the Cenozoic basalts are 0.1465 and 0.1479, with corresponding γOs(t) values of +15 and +16, which are within the range of ocean island basalts. These new Re-Os isotopic results, combined with the findings of previous studies, indicate that the Mesozoic basalts were a hybrid product of the melting of pyroxenite and peridotite in ancient lithospheric mantle beneath the NCC. The Cenozoic basalts were derived mainly from upwelling asthenosphere mixed with small amounts of lithospheric materials. The marked differences in geochemistry between the Mesozoic and Cenozoic basalts suggest a greatly reduced involvement of lithospheric mantle as the magma source from the Mesozoic to the Cenozoic. The subsequent lithospheric thinning of the NCC and replacement by upwelling asthenospheric mantle resulted in a change to asthenosphere-derived Cenozoic basalts.

  6. Bioflotation of pyrite with Thiobacillus ferrooxidans

    Institute of Scientific and Technical Information of China (English)

    Shaoxian Song; Yimin Zhang; Shouci Lu


    Bioflotation of pyrite with bacteria Thiobacillus ferrooxidans in the presence or absence of potassium ethyl xanthate was studied on a pure pyrite through microflotation and electrophoretic light scattering measurements. The experimental results showed that in the absence of xanthate, pyrite flotation is slightly enhanced by Thiobacillus ferrooxidans. However, with xanthate as a collector, pyrite flotation is strongly depressed after being exposed to the bacteria. The longer is the time when the pyrite is exposed to the bacteria, the stronger the depression is. The mechanism of the depression might be due to the formation of the biofilms of Thiobacillus ferrooxidans on pyrite surfaces, preventing the adsorption of xanthate on pyrite surfaces in the form of dixanthogen or xanthate ions.

  7. Re-Os isotopic data for molybdenum from Hejiangkou tungsten and tin polymetallic deposit in Chenzhou and its geological significance

    Institute of Scientific and Technical Information of China (English)

    刘德波; 杨柳; 邓湘伟; 戴雪玲; 王雄军; CHONGkhaiyuen; 杜高峰; 魏和平


    Hejiangkou W−Sn-polymetallic deposit is a newly found deposit in Xitian ore field, one of the important and large scale W−Sn-polymetallic ore fields in the middle segment of Nanling metallogenic zone. Re−Os isotope dating was used on three molybdenite samples from Hejiangkou deposit to determine the ore forming period. The result is (224.9±2.6)Ma−(225±3.1)Ma and isochron age is (225.5±3.6)Ma. The field geological observations, geochronological data and optical petrography indicated that Hejiangkou deposit underwent multi-period of superimposed mineralization. It can be differentiated into three periods composed of six mineralization stages. The first period is the initial period for hydrothermal metasomatism and metal element enrichment during Indosinian Epoch. Further enrichment, strong brittle fracturing and hydrothermal metasomatism, remobilization and superimposition happened in the second period, during early Yanshanian. It is the major mineralization period of Hejiangkou deposit and can be subdivided into four mineralization stages, namely the skarn stage, oxide stage, high-temperature sulfide stage and low-temperature sulfide stage. And the third period is the mineralization period of a porphyry-skarn system related to the emplacement of the granite porphyry dyke. As minerogenic epoch of Hejiangkou deposit is similar with Hehuaping deposit, they show the possibility of Indosinian mineralization event in Nanling metallogenic zone. It can be an important perspective in any future mineral exploration in the same metallogenic zone.

  8. Decay constants in geochronology

    Institute of Scientific and Technical Information of China (English)

    IgorM.Villa; PaulR.Renne


    Geologic time is fundamental to the Earth Sciences, and progress in many disciplines depends critically on our ability to measure time with increasing accuracy and precision. Isotopic geochronology makes use of the decay of radioactive nuclides as a help to quantify the histories of rock, minerals, and other materials. Both accuracy and precision of radioisotopic ages are, at present, limited by those of radioactive decay constants. Modem mass spectrometers can measure isotope ratios with a precision of 10-4 or better. On the other hand, the uncertainties associated with direct half-life determinations are, in most cases, still at the percent level. The present short note briefly summarizes progress and problems that have been encountered during the Working Group's activity.

  9. In Situ Planetary Geochronology Technology Project (United States)

    National Aeronautics and Space Administration — Geochronology is the science of determining the age of rocks, fossils, and sediments.  The science of geochronology is the prime tool used to attempt to derive...

  10. A comparison of selected Precambrian Brazilian chromitites: Chromite, PGE-PGM, and Re/Os as parental source indicators (United States)

    Girardi, V. A. V.; Ferrario, A.; Correia, C. T.; Diella, V.


    Mineralogical and geochemical studies were carried out in chromitites belonging to the mafic-ultramafic bodies of Niquelândia, Luanga, and Campo Formoso, which are, respectively, included in the Goiás Massif and the Amazon and São Francisco cratons. The main platinum-group minerals (PGM) included or associated with chromite grains are laurite in Niquelândia and Campo Formoso and sperrylite and braggite in Luanga. The most common primary base metal sulfides (BMS) are pentlandite, chalcopyrite, and minor pyrrhotite. Also present are base metal alloys (BMA), such as awaruite, and the BMS millerite, pyrite, and copper as secondary mineral phases linked to later alteration process. The Luanga chromites display the lowest Cr 2O 3/Al 2O 3 and Cr 2O 3/FeO t ratios. The chondrite-normalized profiles are strongly enriched in the platinum PGE subgroup (PPGE, Pt, Pd, Rh). The average Pd/Ir ratio (24.2) and 187Os/ 188Os values (0.17869-0.18584) are very high. Niquelândia chromites have higher Cr 2O 3/Al 2O 3 and Cr 2O 3/FeO t ratios than Luanga. Its PGE contents are low and chondrite-normalized profiles depleted, mainly in the PPGE subgroup. The average Pd/Ir ratio (0.45) and 187Os/ 188Os values (0.12598-0.12777) are low. Campo Formoso chromites have the highest Cr 2O 3/Al 2O 3 and Cr 2O 3/FeO t ratios; its average Pd/Ir ratio (0.72) and chondrite-normalized profiles (except the pronounced Ru spike) are closer to those of Niquelândia. The remarkable differences in terms of chromite bulk-composition, PGE contents and patterns, Pd/Ir ratios, and 187Os/ 188Os values associated with probable distinctions in the inferred geochemical compositions of the respective parental magmas indicate that the Luanga and Niquelândia complexes originated from distinct parental sources. Geochemical and isotopic features indicate that Luanga chromitites and associated rocks are consistent with a parental magma, either originated from an enriched mantle reservoir or strongly contaminated

  11. Depressing effect of hydroxamic polyacrylamide on pyrite

    Institute of Scientific and Technical Information of China (English)

    张剑锋; 胡岳华; 王淀佐; 徐竞


    The performance of hydroxamic polyacrylamide(HPAM) in mineral flotation was tested on the samples of calcite, diaspore and pyrite. It is found that HPAM expresses intensive depression on pyrite and can be used as effective depressants for pyrite. The depression mechanism of HPAM to pyrite was investigated by the determination of contact angle, zeta potential, adsorptive capacity for collectors and infrared spectrum. A lower contact angle,more negative zeta potential, less xanthate adsorptive capacity, and the formation of chemical bonding were determined, which reveals that the strong chemical interactions exist between HPAM and pyrite surface. The group electronegativity of HPAM was calculated to explain the differences of interaction between reagent and minerals.

  12. Ultrasonic ash/pyrite liberation

    Energy Technology Data Exchange (ETDEWEB)

    Yungman, B.A.; Buban, K.S.; Stotts, W.F.


    The objective of this project was to develop a coal preparation concept which employed ultrasonics to precondition coal prior to conventional or advanced physical beneficiation processes such that ash and pyrite separation were enhanced with improved combustible recovery. Research activities involved a series of experiments that subjected three different test coals, Illinois No. 6, Pittsburgh No. 8, and Upper Freeport, ground to three different size fractions (28 mesh [times] 0, 200 mesh [times] 0, and 325 mesh [times] 0), to a fixed (20 kHz) frequency ultrasonic signal prior to processing by conventional and microbubble flotation. The samples were also processed by conventional and microbubble flotation without ultrasonic pretreatment to establish baseline conditions. Product ash, sulfur and combustible recovery data were determined for both beneficiation processes.

  13. Interaction between pyrite and cysteine

    Institute of Scientific and Technical Information of China (English)

    LIU Jian-she; WANG Zhao-hui; LI Bang-mei; ZHANG Yan-hua


    The adsorption mechanism of cysteine on pyrite was studied by amounts adsorbed, FTIR and XRD measurements. The results obtained by adsorption experiment suggest that as the mass ratio of mineral to cysteine mp/mc is greater than 5, the amounts adsorbed on mineral is stable after adsorption for 15 min and cysteine adsorbing with mp/mc shows the same tendency. It can be inferred by its Langmuir-type adsorption isotherm that chemical interaction governs the entire adsorption process. The results from FTIR and XRD prove that the functional groups of cysteine appear with blue shift of their characteristic adsorption peak in FTIR spectrum; meanwhile, the lattice constant obviously decreases and the widening of crystal planes such as (210), (220) and (211) is found after cysteine adsorbing on mineral.

  14. PGE, Re-Os, and Mo isotope systematics in Archean and early Proterozoic sedimentary systems as proxies for redox conditions of the early Earth (United States)

    Siebert, C.; Kramers, J. D.; Meisel, Th.; Morel, Ph.; Nägler, Th. F.


    Re-Os data and PGE concentrations as well as Mo concentrations and isotope data are reported for suites of fine clastic sediments and black shales from the Barberton Greenstone Belt, South Africa (Fig Tree and Moodies Groups, 3.25-3.15 Ga), the Belingwe Greenstone Belt, Zimbabwe (Manjeri Formation, ca. 2.7 Ga) and shales from the Witwatersrand, Ventersdorp and Transvaal Supergroups, South Africa ranging from 2.95 to 2.2 Ga. Moderately oxidizing conditions are required to mobilize Re and Mo in the environment, Mo fractionation only occurs in solution, and these parameters thus have potential use as paleoredox proxies for the early Earth. PGE + Re abundance patterns of Barberton Greenstone Belt sediments are uniform and very similar in shape to those of komatiites. This indicates (1) that the PGE came from a source of predominantly ultramafic composition and, (2) that PGE were transported and deposited essentially in particulate form. Sediments from the younger Belingwe Greenstone Belt show more fractionated PGE + Re patterns and have Re/Os ratios 10 to 100× higher than those of Barberton sediments. Their PGE abundance patterns and Re/Os ratios are intermediate between those of the mid-Archean shales and Neoproterozoic to Recent black shales. They reflect scavenging of Re from solution in the sedimentary environment. δ 98/95Mo values of black shales of all ages correlate with their concentrations. The Barberton Greenstone Belt samples have ˜1-3 ppm Mo, similar to a granitoid-basaltic source. This Mo has δ 98/95Mo between -1.9 and -2.4‰ relative to present day mean ocean water molybdenum, MOMO and is thus not isotopically fractionated relative to such a source. Similar to the PGE this indicates transport in solid form. Sediments from the Belingwe Greenstone Belt show in part enhanced Mo concentrations (up to 6 ppm) and Mo isotope fractionation (δ 98/95Mo up to -1.4‰ relative to MOMO). The combined PGE + Re and Mo data show mainly reducing conditions in the

  15. Significance of the whole rock Re-Os ages in cryptically and modally metasomatised cratonic peridotites: Constraints from HSE-Se-Te systematics (United States)

    Luguet, Ambre; Behrens, Melanie; Pearson, D. Graham; König, Stephan; Herwartz, Daniel


    The Re-Os isotopic system is the geochronometer of choice to constrain the timing of lithospheric mantle root formation and reconstruct the evolution of Earth's dynamics from the "mantle" perspective. In order to constrain the effects of metasomatic processes on the Re-Os isotopic system, eleven peridotites from the Letlhakane kimberlite pipe were investigated for whole rock major and trace elements, highly siderophile elements (HSE), Se, Te and 187Os/188Os signatures. These spinel peridotites (SP), garnet peridotites (GP), garnet-phlogopite peridotites (GPP) and phlogopite peridotites (PP) experienced cryptic metasomatism and the GP-GPP-PP additionally constitute a sequence of increasing modal metasomatism. The cryptically metasomatised SP appear devoid of base metal sulphides (BMS) and show suprachondritic Se/Te ratios (15-40) and extremely Pd- and Pt-depleted HSE patterns. These features are characteristic of high-degree partial melting residues. Their 187Os/188Os signatures are thus considered to be inherited from the partial melting event. This implies a Neoarchean (2.5-2.8 Ga, TRD eruption) stabilisation of the Letlhakane mantle root and supports the Letlhakane mantle root being a westerly extension of the Zimbabwe cratonic root. The modally metasomatised peridotites contain BMS whose abundance significantly increases from the GPP to the GP and PP. The BMS-poor GPP are only slightly richer in Pt and Pd than the BMS-free SP but have similarly high Se/Te ratios. The BMS-rich GP and PP exhibit significant enrichments in Pt, Pd, Se, Te resulting in HSE-Se-Te signatures similar to that of the Primitive Upper Mantle (PUM). Addition of 0.001-0.05 wt.% metasomatic BMS ± PGM (platinum group minerals, i.e., Pt-tellurides) to highly refractory residues, such as the Letlhakane SP, reproduce well the HSE-Se-Te systematics observed in the BMS-poor and BMS-rich modally metasomatised peridotites. In the GPP, the negligible addition of metasomatic BMS ± PGM did not disturb

  16. Re-Os isotopes and PGE geochemistry of black shales and intercalated Ni-Mo polymetallic sulfide bed from the Lower Cambrian Niutitang Formation, South China

    Institute of Scientific and Technical Information of China (English)

    JIANG Shaoyong; YANG Jinghong; LING Hongfei; FENG Hongzhen; CHEN Yongquan; CHEN Jianhua


    The Lower Cambrian Niutitang Formation consists of a thick black shale sequence with a regionally distributed conformable Ni-Mo polymetallic sulfide horizon and a chert bed at its basal strata on theYangtze Platform, South China. In this paper, we discuss all available data on Re-Os isotopes and Platinum Group Element (PGE) distribution pattern of the Ni-Mo polymetallic sulfide ore and its host rocks (black shales, cherts, and phosphorites) from Guizhou and Hunan provinces. Our results show that the black shales and the Ni-Mo sulfide ore have a high initial 187Os/188Os ratio of 0.78~0.86, indicating that the Early Cambrian ocean across the Yangtze Platform had a highly radiogenic Os value. This ratio is slightly lower than but still similar to present-day seawater, possibly as a result of high continental weathering at that time. The Ni-Mo sulfide ore yields a Re-Os isochron of 537±10 Ma (MSWD=11.9), possibly representing the depositional age of the Niutitang Formation. The chondrite-normalized PGE pattern, Pt anomaly (Pt/Pt*), Pt/Pd, Ir/Pd, Au/Ir and Re/Mo ratios of the Ni-Mo sulfide ore and its host rocks from South China indicate a varying source contribution of the PGE and other metals for different rocks. It is suggested that the cherts and Ni-Mo sulfide ore may have a significant proportion of PGE and probably other metals deriving from submarine-hydrothermal fluids with a mantle signature.

  17. Re - Os isotopic constraints on the origin of volcanic rocks, Gorgona Island, Colombia: Os isotopic evidence for ancient heterogeneities in the mantle (United States)

    Walker, R.J.; Echeverria, L.M.; Shirey, S.B.; Horan, M.F.


    The Re - Os isotopic systematics of komatiites and spatially associated basalts from Gorgona Island, Colombia, indicate that they were produced at 155??43 Ma. Subsequent episodes of volcanism produced basalts at 88.1??3.8 Ma and picritic and basaltic lavas at ca. 58 Ma. The age for the ultramafic rocks is important because it coincides with the late-Jurassic, early-Cretaceous disassembly of Pangea, when the North- and South-American plates began to pull apart. Deep-seated mantle upwelling possibly precipitated the break-up of these continental plates and caused a tear in the subducting slab west of Gorgona, providing a rare, late-Phanerozoic conduit for the komatiitic melts. Mantle sources for the komatiites were heterogeneous with respect to Os and Pb isotopic compositions, but had homogeneous Nd isotopic compositions (??Nd+9??1). Initial 187Os/186Os normalized to carbonaceous chondrites at 155 Ma (??Os) ranged from 0 to +22, and model-initial ?? values ranged from 8.17 to 8.39. The excess radiogenic Os, compared with an assumed bulk-mantle evolution similar to carbonaceous chondrites, was likely produced in portions of the mantle with long-term elevated Re concentrations. The Os, Pb and Nd isotopic compositions, together with major-element constraints, suggest that the sources of the komatiites were enriched more than 1 Ga ago by low (<20%) and variable amounts of a basalt or komatiite component. This component was added as either subducted oceanic crust or melt derived from greater depths in the mantle. These results suggest that the Re - Os isotope system may be a highly sensitive indicator of the presence of ancient subducted oceanic crust in mantle-source regions. ?? 1991 Springer-Verlag.

  18. ReOs isotope systematics of NiCu sulfide ores, Sudbury Igneous Complex, Ontario: evidence for a major crustal component (United States)

    Walker, R.J.; Morgan, J.W.; Naldrett, A.J.; Li, C.; Fassett, J.D.


    Sudbury Igneous Complex sublayer ores from the Levack West, Falconbridge and Strathcona mines were analyzed for their Re and Os concentrations and Os isotopic compositions. The ReOs isotope systematics of three ores from the different mines give isochron ages of 1840 ?? 60 Ma, 1770 ?? 60 Ma and 1780 ?? 110 Ma, suggesting that the ReOs system became closed at the time of, or soon after the 1850 ?? 1 Ma crystallization age of the complex. The Os isotopic compositions of different portions of the complex at the time of crystallization varied considerably, with initial 187Os 186Os1850 ranging from 4.64 at Levack West to 7.55 at Strathcona. These heterogeneities require that the Os, and probably also the other platinum-group elements contained in the ores, were derived from at least two sources. In addition, the high initial 187Os 186Os ratios indicate that the Os was derived predominantly from ancient crust. Previous studies have suggested that the complex either crystallized from a mixture of mantle-derived basaltic melt and ancient continental crust, or was derived exclusively from the fusion of ancient continental crust resulting from a meteorite impact. Results of modelling suggest that if a contemporaneous mantle-derived basaltic melt was involved in the origin of the SIC, it likely contributed < 50% of the Os to all three ores. The large percentage of ancient crust involved in the production of the ores is most consistent with an interpretation of substantial crustal fusion resulting from meteorite impact. ?? 1991.

  19. Pyrite Stability Under Venus Surface Conditions (United States)

    Kohler, E.; Craig, P.; Port, S.; Chevrier, V.; Johnson, N.


    Radar mapping of the surface of Venus shows areas of high reflectivity in the Venusian highlands, increasing to 0.35 ± 0.04 to 0.43 ± 0.05 in the highlands from the planetary average of 0.14 ± 0.03. Iron sulfides, specifically pyrite (FeS2), can explain the observed high reflectivity. However, several studies suggest that pyrite is not stable under Venusian conditions and is destroyed on geologic timescales. To test the stability of pyrite on the Venusian surface, pyrite was heated in the Venus simulation chamber at NASA Goddard Space Flight Center to average Venusian surface conditions, and separately to highland conditions under an atmosphere of pure CO2 and separately under an atmosphere of 96.5% CO2, 3.5% N2 and 150 ppm SO2. After each run, the samples were weighed and analyzed using X-Ray Diffraction (XRD) to identify possible phase changes and determine the stability of pyrite under Venusian surface conditions. Under a pure CO2 atmosphere, the Fe in pyrite oxidizes to form hematite which is more stable at higher temperatures corresponding to the Venusian lowlands. Magnetite is the primary iron oxide that forms at lower temperatures corresponding to the radar-bright highlands. Our experiments also showed that the presence of atmospheric SO2 inhibits the oxidation of pyrite, increasing its stability under Venusian conditions, especially those corresponding to the highlands. This indicates that the relatively high level of SO2 in the Venusian atmosphere is key to the stability of pyrite, making it a possible candidate for the bright radar signal in the Venusian highlands.

  20. Reply to the comment by Wu et al. (2016) on "Behavior of Re and Os during contact between an aqueous solution and oil: Consequences for the application of the Re-Os geochronometer to petroleum" [Geochim. Cosmochim. Acta 158 (2015) 1-21 (United States)

    Reisberg, Laurie; Michels, Raymond; Mahdaoui, Fatima


    We reply here to the questions raised by Wu et al. concerning the results published by Mahdaoui et al. (2015). This paper describes experiments in which aqueous solutions containing ReO4- and OsCl62- were brought in contact with natural oils at various ranges of concentration, time and temperature. The main observation is that the transfer of Re and Os to oils is very efficient under all experimental conditions. Wu et al. argue that thermodynamic equilibrium was not achieved in these experiments as apparent partition coefficients are inconsistent. They conclude that the experiments were flawed by possible leaking of reactors and that the conclusions by Mahdaoui et al. (2015) were not justified. In the following reply we explain that Mahdaoui et al. (2015) never claimed that thermodynamic equilibrium was achieved. Any calculations or considerations in this context are therefore meaningless. We recall the objectives of our publication, which were to experimentally test the behavior of ReO4- and OsCl6- (two plausible chemical forms of Re and Os in deep aquifers of petroleum systems) in aqueous solution-oil systems. To our knowledge these are the first experiments of their kind. The parameters that could influence the precision and reproducibility of our results were discussed in detail in Mahdaoui et al. (2015). The essential point is that all 60 of the experiments provide evidence of substantial transfer of Re and Os from water to oil. In contrast to what was mistakenly understood by Wu et al., the paper does not challenge the use of Re-Os to date geological events affecting petroleum. Instead, by providing a mechanism that might allow Os isotopic homogenization on a basin-wide scale, a critical step missing from most current models, it offers a possible explanation of how Re-Os geochronology in oils could potentially work. More generally, our study suggests that transfer of Re and Os from waters to oil may be an important phenomenon that should not be overlooked.

  1. Re-Os and Lu-Hf isotopic constraints on the formation and age of mantle pyroxenites from the Bohemian Massif (United States)

    Ackerman, Lukáš; Bizimis, Michael; Haluzová, Eva; Sláma, Jiří; Svojtka, Martin; Hirajima, Takao; Erban, Vojtěch


    We report on the Lu-Hf and Re-Os isotope systematics of a well-characterized suite of spinel and garnet pyroxenites from the Gföhl Unit of the Bohemian Massif (Czech Republic, Austria). Lu-Hf mineral isochrons of three pyroxenites yield undistinguishable values in the range of 336-338 Ma. Similarly, the slope of Re-Os regression for most samples yields an age of 327 ± 31 Ma. These values overlap previously reported Sm-Nd ages on pyroxenites, eclogites and associated peridotites from the Gföhl Unit, suggesting contemporaneous evolution of all these HT-HP rocks. The whole-rock Hf isotopic compositions are highly variable with initial εHf values ranging from - 6.4 to + 66. Most samples show a negative correlation between bulk rock Sm/Hf and εHf and, when taking into account other characteristics (e.g., high 87Sr/86Sr), this may be explained by the presence of recycled oceanic sediments in the source of the pyroxenite parental melts. A pyroxenite from Horní Kounice has decoupled Hf-Nd systematics with highly radiogenic initial εHf of + 66 for a given εNd of + 7.8. This decoupling is consistent with the presence of a melt derived from a depleted mantle component with high Lu/Hf. Finally, one sample from Bečváry plots close to the MORB field in Hf-Nd isotope space consistent with its previously proposed origin as metamorphosed oceanic gabbro. Some of the websterites and thin-layered pyroxenites have variable, but high Os concentrations paralleled by low initial γOs. This reflects the interaction of the parental pyroxenitic melts with a depleted peridotite wall rock. In turn, the radiogenic Os isotope compositions observed in most pyroxenite samples is best explained by mixing between unradiogenic Os derived from peridotites and a low-Os sedimentary precursor with highly radiogenic 187Os/188Os. Steep increase of 187Os/188Os at nearly uniform 187Re/188Os found in a few pyroxenites may be connected with the absence of primary sulfides, but the presence of minor

  2. Age and evolution of the lithospheric mantle beneath the Khanka Massif: Geochemical and Re-Os isotopic evidence from Sviyagino mantle xenoliths (United States)

    Guo, Peng; Xu, Wen-Liang; Wang, Chun-Guang; Wang, Feng; Ge, Wen-Chun; Sorokin, A. A.; Wang, Zhi-Wei


    New geochemical and Re-Os isotopic data of mantle xenoliths entrained in Cenozoic Sviyagino alkali basalts from the Russian Far East provide insights into the age and evolution of the sub-continental lithospheric mantle (SCLM) beneath the Khanka Massif, within the Central Asian Orogenic Belt (CAOB). These mantle xenoliths are predominantly spinel lherzolites with minor spinel harzburgite. The lherzolites contain high whole-rock concentrations of Al2O3 and CaO, with low forsterite content in olivine (Fo = 89.5-90.3%) and low Cr# in spinel (0.09-0.11). By contrast, the harzburgite is more refractory, containing lower whole rock Al2O3 and CaO contents, with higher Fo (91.3%) and spinel Cr# (0.28). Their whole rock and mineral compositions suggest that the lherzolites experienced low-degree (1-4%) batch melting and negligible metasomatism, whereas the harzburgite underwent a higher degree (10%) of fractional melting, and experienced minor post-melting silicate metasomatism. Two-pyroxene rare earth element (REE)-based thermometry (TREE) yields predominant equilibrium temperatures of 884-1043 °C, similar to values obtained from two-pyroxene major element-based thermometry (TBKN = 942-1054 °C). Two lherzolite samples yield high TREE relative to TBKN (TREE - TBKN ≥ 71 °C), suggesting that they cooled rapidly as a result of the upwelling of hot asthenospheric mantle material that underplated a cold ancient lithosphere. The harzburgite with a low Re/Os value has an 187Os/188Os ratio of 0.11458, yielding an Os model age (TMA) relative to the primitive upper mantle (PUM) of 2.09 Ga, and a Re depletion ages (TRD) of 1.91 Ga; both of which record ancient melt depletion during the Paleoproterozoic ( 2.0 Ga). The 187Os/188Os values of lherzolites (0.12411-0.12924) correlate well with bulk Al2O3 concentrations and record the physical mixing of ancient mantle domains and PUM-like ambient mantle material within the asthenosphere. This indicates that the SCLM beneath the Khanka

  3. Geochemical, mineralogical and Re-Os isotopic constraints on the origin of Tethyan oceanic mantle and crustal rocks from the Central Pontides, northern Turkey (United States)

    Çelik, Ömer Faruk; Marzoli, Andrea; Marschik, Robert; Chiaradia, Massimo; Mathur, Ryan


    Chromite, ultramafic and mafic rocks from Eldivan, Yapraklı, Ayli Dağ, Küre, Elekdağ and Kızılırmak in northern Turkey have been studied to determine their mineral and whole-rock geochemical, and Re-Os isotope geochemical characteristics. Most of the studied peridotites display depleted but commonly V-shaped chondrite-normalized rare-earth element (REE) patterns while some peridotites as well as pyroxenites from all areas exhibit light REE depleted patterns. Olivine (forsterite 82 to 92 mol%) and spinel (chromium number 13 to 63) in the studied peridotites exhibit a wide range of compositions. Compositions of spinels suggest that peridotites from Eldivan, Ayli Dağ and Küre experienced relatively large degrees of partial melting ( 15 and 19 wt%), whereas those of the Kızılırmak area most likely reflect lower melting degrees ( 4-6 wt%). Whole-rock and mineral chemical data indicate that the ultramafic rocks are similar to abyssal and supra-subduction zone peridotites. The ultramafic rocks of the investigated areas exhibit a wide range of 187Re/188Os (0.12 to 6.6) and measured 187Os/188Os (0.122-1.14), while the basaltic rocks from Küre, Eldivan and Kızılırmak areas have high 187Re/188Os (128-562) and measured 187Os/188Os (0.724-1.943). On the other hand, chromite from Eldivan, Elekdağ and Kızılırmak show high Os contents (21.81-44.04 ppb) and low 187Re/188Os (0.015-0.818) and 187Os/188Os (0.122-0.133). Re-Os model ages (TChur) for all analyzed samples yielded scattered ages ranging from Jurassic to Proterozoic. Overall, geochemical data are interpreted to reflect different degrees of partial melting, melt - rock interactions and metasomatic effects that produced a heterogeneous mantle in a supra-subduction setting.


    Institute of Scientific and Technical Information of China (English)

    杨刚; 谢智; 陈江峰


    铁陨石中的Re,Os含量反映其结晶分异历史。通过铁陨石定年修正187Re的衰变常数为:λ(187Re)=1.666×10-11a-1。Re Os同位素测年法可以直接用于对铁陨石的定年,结果表明天然铁陨石大体同时形成,但Re Os定年技术已有可能揭示不同化学群铁陨石形成年代的序列,但研究尚需深入。这些方法也可以用来探讨铁陨石和石铁陨石的形成源区、冷却历史和后期变化。虽然在石陨石中Re,Os同位素的浓度很低,但也有了探索性研究成果。随着技术的不断发展,Re Os同位素体系在天体化学中的作用将愈加明显和重要。%The concentrations of Re and Os in iron meteorites could indicate the history of differentiation and crystallization of irons. The decay constant of 187Re has been corrected by studying iron meteorites and the new decay constant λ(187Re)=1.666×10-11a-1. Re-Os chronology could be directly used to date iron meteorites. The results from the method show that all iron meteorites were formed at about the same time. However, further study suggests that different groups of irons were crystallized at slightly different times. This method also helps in studying the source, cooling history and secondary alterations of the chondrites and iron meteorites. Although the Re and Os concentrations are very low in the ordinary chondrites, some results have been obtained in this field. As a powerful cosmochemical tracer, the Re-Os isotopic system will help much in a better understanding of origin and evolution of meteorites.


    Institute of Scientific and Technical Information of China (English)


    The experimental studies on the microbial flotation of a pure pyrite sample using Thiobacillus ferrooxidans was conducted in the laboratory. The results indicate that Thiobacillus ferrooaidans has strong depression effect on the flotation of pyrite. Thiobacillus f errooxidans can adsorb on the surface of pyrite in a very short time (a few min. ), changing the surface from hydrophobic into hydrophilic and making the pyrite particles to lose their floatability. Therefore, Thiobacillus ferrooxidans is an effective microbial depressant of pyrite. It has also been pointed out that the depression of pyrite by Thiobacillus ferrooxidans is caused by the adsorption of the microbial colloids, but not by the oxidation effect.

  6. Distribution of arsenic, selenium, and other trace elements in high pyrite Appalachian coals: evidence for multiple episodes of pyrite formation (United States)

    Diehl, S.F.; Goldhaber, M.B.; Koenig, A.E.; Lowers, H.A.; Ruppert, L.F.


    Pennsylvanian coals in the Appalachian Basin host pyrite that is locally enriched in potentially toxic trace elements such as As, Se, Hg, Pb, and Ni. A comparison of pyrite-rich coals from northwestern Alabama, eastern Kentucky, and West Virginia reveals differences in concentrations and mode of occurrence of trace elements in pyrite. Pyrite occurs as framboids, dendrites, or in massive crystalline form in cell lumens or crosscutting veins. Metal concentrations in pyrite vary over all scales, from microscopic to mine to regional, because trace elements are inhomogeneously distributed in the different morphological forms of pyrite, and in the multiple generations of sulfide mineral precipitates. Early diagenetic framboidal pyrite is usually depleted in As, Se, and Hg, and enriched in Pb and Ni, compared to other pyrite forms. In dendritic pyrite, maps of As distribution show a chemical gradient from As-rich centers to As-poor distal branches, whereas Se concentrations are highest at the distal edges of the branches. Massive crystalline pyrite that fills veins is composed of several generations of sulfide minerals. Pyrite in late-stage veins commonly exhibits As-rich growth zones, indicating a probable epigenetic hydrothermal origin. Selenium is concentrated at the distal edges of veins. A positive correlation of As and Se in pyrite veins from Kentucky coals, and of As and Hg in pyrite-filled veins from Alabama coals, suggests coprecipitation of these elements from the same fluid. In the Kentucky coal samples (n = 18), As and Se contents in pyrite-filled veins average 4200 ppm and 200 ppm, respectively. In Alabama coal samples, As in pyrite-filled veins averages 2700 ppm (n = 34), whereas As in pyrite-filled cellular structures averages 6470 ppm (n = 35). In these same Alabama samples, Se averages 80 ppm in pyrite-filled veins, but was below the detection limit in cell structures. In samples of West Virginia massive pyrite, As averages 1700 ppm, and Se averages 270

  7. Catalytic activity of pyrite for coal liquefaction reaction; Tennen pyrite no shokubai seino ni kansuru kento

    Energy Technology Data Exchange (ETDEWEB)

    Hirano, K.; Kozu, M.; Okada, T.; Kobayashi, M. [Nippon Coal Oil Co. Ltd., Tokyo (Japan)


    Since natural pyrite is easy to obtain and cheap as coal liquefaction catalyst, it is to be used for the 150 t/d scale NEDOL process bituminous coal liquefaction pilot plant. NEDO and NCOL have investigated the improvement of catalytic activity of pulverized natural pyrite for enhancing performance and economy of the NEDOL process. In this study, coal liquefaction tests were conducted using natural pyrite catalyst pulverized by dry-type bowl mill under nitrogen atmosphere. Mechanism of catalytic reaction of the natural pyrite was discussed from relations between properties of the catalyst and liquefaction product. The natural pyrite provided an activity to transfer gaseous hydrogen into the liquefaction product. It was considered that pulverized pyrite promotes the hydrogenation reaction of asphaltene because pulverization increases its contact rate with reactant and the amount of active points on its surface. It was inferred that catalytic activity of pyrite is affected greatly by the chemical state of Fe and S on its surface. 3 refs., 4 figs., 1 tab.

  8. Re-Os isotope systematics in black shales from the Lesser Himalaya: their chronology and role in the 187Os/ 188Os evolution of seawater (United States)

    Singh, Sunil K.; Trivedi, J. R.; Krishnaswami, S.


    Re and Os abundances and Os isotope systematics have been measured in a number of black shales sampled from outcrops and two underground phosphorite mines, Maldeota and Durmala, in the Lesser Himalaya. The Re and Os concentrations in these samples exhibit wide range, 0.2 to 264 ng/g and 0.02 to 13.5 ng/g, respectively, with a mean Re/Os of ˜25. The 187Os/ 188Os of these samples also show a broad range 1.02 to 11.6, with many of them far more radiogenic than the currently eroding continental crust. The black shales from the Maldeota and Durmala mines, collected a few meters above the Krol-Tal (Pc-C) boundary and occurring in the same stratigraphic horizon, yield 187Re- 187Os isochron ages of 554 ± 16 and 552 ± 22 Ma, respectively, consistent with fossil evidences and those assigned for the Pc-C boundary at various other locations. These results indicate closed system behaviour of Re and Os in these mine samples and reaffirm the validity of 187Re- 187Os pair to date organic-rich sediments. The age of these mine samples from the outer belt seems to be a few hundred millions of years younger than the preliminary Re-Os age of 839 ± 138 Ma for black shales from Theog, collected from the inner belt. These initial results lean toward the hypothesis that the inner belt sediments were deposited earlier than the outer belt; however, more analyses of black shales are needed to confirm this. The role of weathering black shales from the Himalaya in contributing to the Os isotope evolution of seawater over the past ˜25 Ma was assessed using a simple budget model for seawater Os and assuming values for Os fluxes and 187Os/ 188Os based on the available limited data on Os concentration and its 187Os/ 188Os in rivers and oceans. These calculations indicate that the required contributions from black shale weathering to account for the entire increase in oceanic 187Os/ 188Os over the past ˜16 Ma is difficult to satisfy by varying only the Os flux from HTP rivers ( 187Os/ 188Os

  9. Optimisation of sample preparation protocols for measurement of PGE and Re-Os in organic-rich shales by isotope dilution ICP-MS (United States)

    Rammensee, Philipp; Aulbach, Sonja; Gudelius, Dominik; Brey, Gerhard


    Platinum-group elements (PGE) and Re-Os isotopes, which are variably redox-sensitive and fluid-soluble, have potential as proxies for the oxygenation of the atmosphere and oceans (e.g. [1]). However, analysis of these elements in organic rich shales (ORS) is challenging due to abundances of chromatography is necessary to minimise the effects of interfering elements, but presents its own challenges. We are in the process of conducting variations of acid digestion and column chromatographic protocols on reference sample SDO-1 (Devonian Ohio Shale, USGS). We aim to identify the optimum protocol to investigate PGE-Re-Os systematics of ORS that were sampled as part of the Barberton Drilling Project BARB5 drill core, in order to constrain the changes in detrital and hydrogenous contributions to the sediment with time, to assess the extent of euxinity in the sedimentary basin and to look for evidence of transient "whiffs of oxygen" [1]. The following digestion methods were tested: (1) 4h acid digestion in High Pressure Asher (HPA) apparatus with reverse aqua regia at 300°C and 130 bar (only this digestion allows extraction of volatilised Os in CHCl3 followed by HBr); (2) 3h reverse aqua regia digestion in centrifuge vials on hotplate at 80°C; (3) 48h reverse aqua regia digestion in closed Teflon beakers on hotplate at 140°C followed by a HF/HNO3 digestion step; (4) 48h HF/HNO3 digestion of ashed sample powder in closed Teflon beaker at 140°C on hotplate followed by an aqua regia digestion step. Column chromatographic approaches to decrease the concentrations of interfering elements (Y, Zr, Mo, Cd, Hf, Hg) include the use of cation- and anion resins, and variations of the molarity and composition of the eluent. Preliminary results show that digestion method (1) leaves behind small amounts of presumably PGE-free silica gel; (2) yields consistently higher Re concentrations with an expectedly large amount of solid residue; (3) produces an insoluble sludge; (4) allows

  10. Pyrite Oxidation Related to Pyritic Minesite Spoils and Its Controls:A Review

    Institute of Scientific and Technical Information of China (English)

    郑作平; H.H.GERKE; 等


    Pyrite oxidation is considered to be a main contribution to the acidification of minesite spoils and the generation of the Acid Mine Drainage(AMD) which has become the greatest threat to the ecological environment,In this paper,pyrite oxidation and its controls are reviewed with respect to the latest literature,conceptual Model and empirical rate law model with reference to indoor experiments are classified and presented to describe pyrite oxidation in heterogeneous minesite spoil piles.The influences of Thiobacillus(T) ferrooxidans on pyrite oxidation are simply summarized.In order to prevent the generation of the AMD,three approaches including the addition of alkali to minesite spoil,use of dry covers,and coating on the minesite spilk surface,are discussed.

  11. Re-Os isotopic dating of chalcopyrite from the Abalieke copper-lead deposits in West Kunlun, China%西昆仑阿巴列克铜铅矿床黄铜矿Re-Os定年及地质意义

    Institute of Scientific and Technical Information of China (English)

    张正伟; 漆亮; 沈能平; 游富华; 张中山; 周灵洁


    It is a very important and effective method of analyzing the ore-forming processes by taking advantage of geochemistry analytical approaches as well as traditional ways, such as testing the Re-Os, discriminating the paragenetic association of the minerals and the tectonic settings. Seven chalcopyrite and one pyrite samples from the main orebody of Abalieke Cu-Pb deposit are used for Re-Os dating. The chalcopyrite is associated with galenite and dolomite which contain 626 x 10 " ~ 14533 x 10 ~ of Re and 0. 026 x 10 ~0. 36 x 10 "9 of Os respectively, and yield a Hercynina isochron age of 331. 3 ±5. 2Ma. High Re/Os ratio, low Os concentration and highly radiogenic Os isotopic ratios of these samples suggest that they are of crustal origin. The tectonic evolving shows that the southwestern margin of the Tarim block was a passive continental margin in the Late Paleozoic era. Because of the Paleo-Tethys ocean movement during Carboniferous, the depression basin are formed in margin of Tarim craton, comprised lead-zinc deposits in clastic rock-carbonate host stratum that cover up the Devonian. This Re-Os isotopic dating age of chalcopyrite is nearly closed with ore-hosted stratum. Our Re-Os result provides new evidences, showing that Abalieke Cu-Pb deposit experienced the syngenetic ore-forming process in Hercynina Also this study gives important geochemical evidence on such issues; the lead-zinc deposits are mainly sedimentary formation-controlled type; the ore-forming elements mainly came from stratum; mineralization occurred in the joint position between Upper Devonian and Lower Carboniferous, while the rock in which mainly consist of sandstone and carbonatite formation. It can be seen that the metallogenic system of the copper-lead-zinc strata-bound deposits in carbonate rock has a certain complexity and provides wider space for further researches.%除了传统的测试Rb-Sr、Sm-Nd、U-Th-Pb、K-Ar或Ar-Ar等方法来讨论碳酸盐岩层控型铅锌矿的成矿年

  12. Nucleic acid interactions with pyrite surfaces (United States)

    Mateo-Martí, E.; Briones, C.; Rogero, C.; Gomez-Navarro, C.; Methivier, Ch.; Pradier, C. M.; Martín-Gago, J. A.


    The study of the interaction of nucleic acid molecules with mineral surfaces is a field of growing interest in organic chemistry, origin of life, material science and biotechnology. We have characterized the adsorption of single-stranded peptide nucleic acid (ssPNA) on a natural pyrite surface, as well as the further adsorption of ssDNA on a PNA-modified pyrite surface. The characterization has been performed by means of reflection absorption infrared spectroscopy (RAIRS), atomic force microscopy (AFM) and X-ray photoemission spectroscopy (XPS) techniques. The N(1s) and S(2p) XPS core level peaks of PNA and PNA + DNA have been decomposed in curve-components that we have assigned to different chemical species. RAIRS spectra recorded for different concentrations show the presence of positive and negative adsorption bands, related to the semiconducting nature of the surface. The combination of the information gathered by these techniques confirms that PNA adsorbs on pyrite surface, interacting through nitrogen-containing groups of the nucleobases and the iron atoms of the surface, instead of the thiol group of the molecule. The strong PNA/pyrite interaction inhibits further hybridization of PNA with complementary ssDNA, contrary to the behavior reported on gold surfaces.

  13. Cu-Mo-Au mineralization in Qarachilar area, Qaradagh batholith (NW Iran): Fluid inclusion and stable isotope studies and Re-Os dating (United States)

    Simmonds, Vartan; Moazzen, Mohssen


    The Qaradagh batholith is located in NW Iran, neighboring the Meghri-Ordubad granitoid in southern Armenia. This magmatic complex is emplaced in the northwestern part of the Urumieh-Dokhtar magmatic arc, which formed through north-eastward subduction of Neo-Tethyan oceanic crust beneath the central Iranian domain in the late-Mesozoic and early-Cenozoic and hosts most of the porphyry copper deposits and prospects in Iran, such as Sarcheshmeh and Sungun. The Qaradagh batholith is comprised of Eocene-Oligocene intrusive rocks occurring as multi-episode stocks, where the dominant rock type is granodiorite. Hydrothermal alterations have also occurred in these rocks including potassic, phyllic-sericitic, argillic and propylitic alterations and silicification. These alterations are accompanied by vein-type and disseminated Cu, Mo and Au mineralization. The Qarachilar area is located in the central part of the Qaradagh batholith, which hosts mono-mineralic and quartz-sulfide veins and veinlets (several mm to hydrothermal aqueous fluids have most likely experienced boiling and also mixed with low temperature and low salinity superficial fluids. Occurrence of boiling is also supported by the coexistence of liquid-rich and vapor-rich 2-phase inclusions as well as multi-phase halite-bearing inclusions which homogenize in a similar range of TH. The calculated minimum pressure at the time of entrapment is estimated about 50 to 120 bar, which is equal to the hydrostatic depth of 500-1100 m. Stable isotope studies of O, H and S on the quartz and sulfide samples taken from quartz-sulfide veins-veinlets reveal a magmatic origin for the ore-bearing fluid and its sulfur content. The δ18O values for quartz and fluid are about 11.13-12.47 ‰ and 5.78-6.89 ‰ (SMOW), respectively, the δD values are about -93 and -50 ‰ and the δ34S values of sulfide minerals are about -1.37-0.49‰ (VCDT). Re-Os model ages calculated for molybdenite samples range between 25.19±0.19 and 31.22±0

  14. An integrated petrological, geochemical and Re-Os isotope study of peridotite xenoliths from the Argyle lamproite, Western Australia and implications for cratonic diamond occurrences (United States)

    Luguet, A.; Jaques, A. L.; Pearson, D. G.; Smith, C. B.; Bulanova, G. P.; Roffey, S. L.; Rayner, M. J.; Lorand, J.-P.


    An integrated study of the petrology and Re-Os geochemistry of a suite of peridotite xenoliths, some carrying abundant diamonds, from the richly diamondiferous Argyle AK1 lamproite pipe provides definitive evidence for a depleted lithospheric root of Neoarchean age (T RD eruption ˜ 2.2-3.1 Ga) beneath the Proterozoic Halls Creek Orogen at the margin of the Kimberley Craton, Western Australia. The microdiamonds from the peridotitic xenoliths are similar in their properties to the minor population of small, commercial sized, peridotitic diamonds from Argyle, both formed in the Archean from isotopically mantle-like carbon. The major element bulk chemistry and mineral chemistry of the Argyle peridotites are slightly less depleted than Archean cratonic peridotites as a whole but similar to those reported from Neoarchean-Paleoproterozoic cratonic provinces. The Argyle peridotite xenoliths were derived from within the diamond stability field (1050-1300 °C and 4.9-5.9 GPa) near the base of the lithosphere (typically 160-200 km depth) with a geothermal gradient of 41.5 mW/m 2. This thick diamondiferous lithosphere, estimated at up to 225 km thick from present day seismic S-wave tomography, appears to have persisted since the time of eruption of the Argyle lamproite (˜ 1180 Ma). The existence of late Archean age lithosphere beneath the Argyle diamond pipe, in a region where no crustal rocks of Archean age are known, suggests a decoupling of the crust and mantle in the region of the Halls Creek Orogen, perhaps as a consequence of Paleoproterozoic (˜ 1.85 Ga) reworking and/or subduction at the margin of the Kimberley Craton. The confirmation of an Archean lithospheric root beneath the Argyle pipe at the margin of the Kimberley Craton seemingly conforms with "Clifford's Rule", regarding the restriction of economic diamond deposits to those underlain by Archean cratons. However, Argyle owes its rich diamond grades not to its Neoarchean mantle roots but to the presence of

  15. Pyrite oxidation by Acidithiobacillus ferrooxidans bacteria

    Directory of Open Access Journals (Sweden)

    Savić Dragiša S.


    Full Text Available The kinetic model of pyrite particle dissolution by the action of bacteria Acidithiobacillus ferrooxidans in a shaken Erlenmeyer flask was presented. The model agreed well with the experimental data for the extracted iron and the number of cells in the liquid phase. The specific growth rate of the adsorbed cells was evaluated (μA = 1,6 d-1 by fitting the experimental data to the model curve. Also, the relevance of the two proposed mechanisms for the bacterial dissolution of sulphide (direct and indirect was discussed, indicating that the indirect one was dominant. The adsorption process of A. ferrooxidans to the pyrite surface was well correlated by a Langmuir type isotherm.

  16. The Adsorption of Cu Species onto Pyrite Surface and Its Effect on Pyrite Flotation

    Directory of Open Access Journals (Sweden)

    Bo Yang


    Full Text Available The adsorption of Cu species onto pyrite surface and its effect on flotation were investigated by using microflotation tests, first-principle calculations, and XPS surface analysis. The results indicated that the flotation of pyrite appears to be activated with CuSO4 only at alkaline pH, while being depressed at acidic and neutral pH. The adsorption of copper ions on pyrite surface was pH-dependent, and the adsorption magnitude of copper ions at alkaline pH is higher than that at acidic and neutral pH due to a strong interaction between O atom in Cu(OH2 and surface Fe atom except for the interaction between Cu atom and surface S atom. At acidic and neutral pH, there is only an interaction between Cu atom and surface S atom. The adsorption was relatively weak, and more copper ions in solution precipitated the collector and depressed the flotation of pyrite. XPS analysis confirmed that more copper ionic species (Cu(I and Cu(II are adsorbed on the pyrite surface at alkaline pH than that at acidic and neutral pH.

  17. Utilization of coal-derived pyrite by electrolysis

    Institute of Scientific and Technical Information of China (English)

    LI Deng-xin; M.Makino; GAO Jin-sheng; MENG Fan-l ing


    The utilization of coal-derived pyrite by electrolysis was studie d. It is obvious that the sulfur and Fe in pyrite can be electrolyzed into Fe 3+ and SO2-4, and the no pollutant is drained off. In this paper, the infl uence of conditions, including electrolysis potential, time, temperature, the acidity of electrolysis solutions, the concentration of adding agent, the concentration of pyrite, and the rate of conversion of pyrite (Cr) was investigated. Cr increase s with the rise of potential, time, temperature, acidity and the concentration o f additive agent, but decreases with the rise of concentration of pyrite. At th e certain conditions (at the potential of 3.0 V, temperature of 298 K, time of 12 h , the concentration of MnSO4 of 6%, concentration of pyrite of 4%, and concent ra tion of acid of 10%), Cr is high to 93%. In the same time, the mechanism of elec trolysis of pyrite was provided. The electrolysis of pyrite is actually the r ecycle of Mn ion between anodic surface and pyrite. At last, the production of F eSO4*7H2O through electrolysis of pyrite was introduced.

  18. Utilization of coal-derived pyrite by electrolysis

    Institute of Scientific and Technical Information of China (English)

    李登新; M.Makinot; 高晋生; 孟繁玲


    The utilization of coal-derived pyrite by electrolysis was studied. It is obvious that the sulfur and Fe in pyrite can be electrolyzed into Fe3+ and SO2-4, and the no pollutant is drained off. In this paper, the influence of conditions, including electrolysis potential, time, temperature, the acidity of electrolysis solutions, the concentration of adding agent, the concentration of pyrite, and the rate of conversion of pyrite (Cr) was investigated. Cr increases with the rise of potential, time, temperature, acidity and the concentration of additive agent, but decreases, with the rise of concentration of pyrite. At the certain conditions (at the potential of 3.0 V, temperature of 298 K, time of 12 h, the concentration of MnSO4 of 6%, concentration of pyrite of 4%, and concentration of acid of 10%), Cr is high to 93%. In the same time, the mechanism of electrolysis of pyrite was provided. The electrolysis of pyrite is actually the recycle of Mn ion between anodic surface and pyrite. At last, the production of FeSO4·7H2O through electrolysis of pyrite was introduced.

  19. Effects of pyrite on the spontaneous combustion of coal

    Institute of Scientific and Technical Information of China (English)

    Jun Deng; Xiaofeng Ma; Yutao Zhang; Yaqing Li; Wenwen Zhu


    Pyrite has a significant effect on the spontaneous combustion of coal. The presence of pyrite can change the propensity of coal towards spontaneous combustion. The influences of various pyrite contents on the parameters of spontaneous combustion, such as index gases, temperature and released heat etc., were investigated in this study. Coal samples with different pyrite contents (0%, 3%, 5%, 7%and 9%) were made by mixing coal and pyrite. The oxidation experiments under temperature-programmed condition were carried out to test the release rate of gaseous oxidation products at different temperatures. Differential scanning calorimeter (DSC) was employed to measure the intensity of heat release during coal oxidation for various pyrite contents. The results indicate that pyrite can nonlinearly accelerate the process of spontaneous combustion. The coal sample with a pyrite content of 5% has the largest CO release rate and oxygen adsorption as well. However, the coal sample with a pyrite content of 7% has the largest rate of heat flow according to the results from the DSC tests. Pyrite contents of 5%–7% in coal has the most significant effects on spontaneous combustion within the range of this study. The conclusions are conducive to the evaluation and control for the spontaneous combustion of coal.

  20. 内蒙古白乃庙铜(钼)矿床辉钼矿Re Os 同位素年龄及其地质意义%Re Os Isotopic Dating of Molybdenite from the Bainaimiao Cu(Mo) Deposit in Inner Mongolia and Its Geological Significance

    Institute of Scientific and Technical Information of China (English)

    冯晓曦; 姚书振; 段明; 曲凯; 王佳营; 冯旭彪; 李超; 周利敏


    The Bainaimiao Cu(Mo)deposit is the most important ones in the north margin of North China plate.It is composed of south belt and north belt.In south belt,ore bodies are concordant with ore-hosting green schist of the Cambrain Bainaimiao Formation,with near-bedded and lenticular shapes, the major bodies in north belt are located in granodiorite intrusion and partly extending into host rocks. The metallogenic age of this deposit has been disputed for many years.To dtermine the minerlization age,Re Os isotopic dating of five molybdenite samples,separated from both south and north ore belt, are completed,five molybdenite samples yield isotopic model ages of (435.8±6.0)Ma to (443.0±6.1) Ma,and an isochron age of (440.5±4.4)Ma (2σ,MSWD=1.4).These ages are well concordant with the emplacement age (440.0 Ma)of the granodiorite.Combining with regional geological background and deposit characteristics,authors think synthetically that the deposit formed in Early Silurian and has close relationship with granodioritic (440.0 Ma ) magmatic activities in Early Silurian. The mineralization age is also consist with the period (446.0 453.0 Ma)of the intensive southward subduction of the paleo-Asian oceanic plate beneath to the northern margin of the North China plate.By synthetical analysis,authors conclude that the major metallogenetic event were resulted from the evolution of the trech-basin-arc system and continent margin accretion in the North China plate during the Early Paleozoic epoch.%内蒙古白乃庙铜(钼)矿床是华北板块北缘中段最重要的一个铜(钼)矿床,矿床由南、北两矿带构成。南矿带矿体主要产于寒武系白乃庙组绿片岩中,矿体产状与围岩基本一致;北矿带矿体大部分产于花岗闪长岩体中,部分延进围岩。利用 Re Os 同位素定年方法对南、北矿带主要矿段的5件辉钼矿样品进行了成矿时代研究,结果表明,辉钼矿样品的 Re Os 同位素模式年龄为(435.8±6

  1. 内蒙古兴和县曹四夭特大型钼矿床辉钼矿Re-Os同位素年龄及地质意义%Re-Os Isotopic Age Dating of the Molybdenite Separated from the Caosiyao Giant Molybdenum Deposit, Xinghe County, Inner Mongolia, and Its Geological Significances

    Institute of Scientific and Technical Information of China (English)

    聂凤军; 李香资; 李超; 赵宇安; 刘翼飞


    porphyry stocks as veins, veinlets and disseminated blocks. The molybdenum ore consists of pyrite, molybdenite, chalcopyrite, sphalerite, wolframite, K-feldspar, quartz, sericite, chlorite and epidote. As the most important economic molybdenum mineral, molybdenite occurs as impregnation, radioflake, thin film, aggregated flakes and veinlet. Re-Os isotopic age dating on four molybdenite samples from the main orebody gives model ages of 131. 9 ± 2. 3Ma, 131. 2±2. 3Ma, 129. 7 ± 2. OMa and 128. 6 ± 2. 4Ma, with an average value of 130. 4 ±2. 4Ma, which is similar to that of zircon U-Pb age of the ore-bearing granitoid porphyry. As the Re-Os model ages are in agreement with field geological evidences, and the molybdenite has co-existing relations with pyrite and chalcopyrite, it has been suggested that the Re-Os model ages represent the ore-forming time of the Mo mineralization occurring in the Caosiyao district and its neighboring area. Preliminary studies show that the Caosiyao deposit were formed during the Mesozoic Yanshanian extensional tectonic movements that resulted in the intensive igneous activities. It is believed to be a product of the Early Cretaceous intraplate granitoid magmatism within the Liangcheng uplift. The well-developed high K and SiO2 granitoid porphyry stocks and dykes might have acted as the "engines" of the ore-forming systems. Most of the Mo was derived from partial melting of the Precambrian continental crust. The ore-forming fluid was dominated by magmatic water at the early metallogenic stage, and was characterized by mixture with magmatic water as the major source at the main metallogenic stage. The combined geochemical data, field geological observations and petrological evidence indicate that the Caosiyao deposit belongs to the porphyry type Mo deposit. The genetic model and mineral exploration criteria of the Caosiyao deposit can also be used as useful tools during the comprehensive evaluation of concealed Mo deposits in Inner Mongolian

  2. Interfacial interaction of bio-leaching of pyrite mineral

    Institute of Scientific and Technical Information of China (English)

    GU Guo-hua; WANG nui; SUO Jun; QIU Guan-zhou; HAO Ye


    Electrokinetic and contact angle measurements were used to discuss the interracial interaction on bio-leaching of pyrite mineral. Surface energy parameters of pyrite mineral and thiobaeillus ferrooxidans were Gbtained by calculating according to formula of Young's equation and contact angle measurements. The results show that surface energy of thiobacillus ferrooxidans is much higher than that of pyrite mineral, and the reaction of pyrite mineral with thiobacillus ferrooxidans causes the reduction of the pyrite surface energy. The interfacial interaction energies between pyrite mineral and thiobacillus ferrooxidans were also obtained based onpolar interfacial interaction theory and electrokinetic and contact angle measurements. The thermodynamics approach only considering Lifshitz-van der Waals and Lewis acid-base interaction fails to explain the adhesion behavior of the bacteria, but theextended Derjaguin-Landan-Verwey-Overbeek theory concerning Lifshitz-van der Waals and Lewis acid-base and the electrostatic can exactly predict interracial interaction.

  3. Thermoacidophilic archaea for pyrite oxidation in coal desulphurization

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, Liselotte


    The desulfurization of low-sulfur coals has been demonstrated with the thermoacidophilic archaeon Acidianus brierleyi. A. brierleyi facilitates the removal of inorganic sulfur from coal and oxidizes mineral pyrite. The results imply that the mechanism behind microbial coal desulfurization and pyrite oxidation is a combination of biotic and abiotic leaching of pyrite. The extent of sulfur removal is dependent on the type of coal and is closely related to he amount of pyritic sulfur in the coal. Studies have shown that neither ash content nor heating value were dramatically affected by the microbial treatment. The use of the archaea Sulfolobus acidocaldarius and Sulfolobus solfataricus, as well as the mesophilic bacteria Thiobacillus ferrooxidans and several Pseudomonas species, has also been studied for coal desulfurization and mineral pyrite oxidation. The archaea and Pseudomonas species did not grow autotrophically on mineral pyrite neither did they oxidize pyrite in coal. The oxidation rate was, however, 5-10 times less than with A. brierleyi on mineral pyrite. The rate of sulfur removal from coal was in the same range as for A. brierleyi which indicates that different reactions are rate limiting in coal depyritization than in mineral pyrite oxidation. 133 refs, 18 figs, 3 tabs

  4. 内蒙古红岭铅锌多金属矿床辉钼矿Re-Os 同位素年龄及其意义%Re-Os Radiometric Dating of Molybdenite in Hongling Lead-Zinc Polymetallic Deposit,Inner Mongolia,and Its Significance

    Institute of Scientific and Technical Information of China (English)

    万多; 李剑锋; 王一存; 王可勇; 王志高; 魏良民


    Hongling lead-zinc polymetallic deposit share many similarities with others from the southern Daxinganling poly-metallic metallogenic belt.There are two types of molybdenum mineralization in the mining area,including porphyry and skarn.The former,displaying spot-disseminated feature,occurs in granite porphyry,whereas the latter,displaying film like feature,occurs in quartz.The metallogenic age of Hongling deposit can be constrained from Re-Os isotopic dating of the two kinds of molybdenite.Five samples of spot-disseminated molybdenite yield model ages varying from 139.9±2.3 Ma to 141.5± 3.2 Ma,with an isochron age of 140.3±3.4 Ma (MSWD=0.082),and a weighted average of 140.10±1.80 Ma.The isochron age and weighted average model age are consistent with one another,implying that molybdenum mineralization in Hongling de-posit occurred in Late Jurassic.A film-like molybdenite sample yielded a model age of 143.7±3.6 Ma,representing the initial stage of lead-zinc mineralization.The Re-1 87 Os contents of the film-like molybdenite are higher than that of spot-disseminated molybdeniteby one order of magnitude,which hints that they have different origins and there are two phases of molybdenum mineralization.The characteristics of Re content of the 6 molybdenite samples suggest that the ore-forming elements had a shal-low source,and was mainly derived from the crust.The extremely low content of Re might be du to the low Re content within its parent magma as well as its paragenetic mineral assemblage.Combined with the results of previous study,it is concluded that (a)both rock-and ore-forming materials of Hongling deposit came from hyperplasia crust;and (b)the deposit formed in a dynamical environment of continental crust extension post Mongolia-Okhotsk collisional orogeny.%红岭铅锌多金属矿床为大兴安岭南段多金属成矿带的代表性矿床之一.区内发育斑岩型和矽卡岩型2种钼矿化,前者为产于花岗斑岩内呈斑点-浸染状产出的

  5. Pyritic ash-flow tuff, Yucca Mountain, Nevada -- A discussion

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, S.I.; Larson, L.T.; Noble, D.C. [Univ. of Nevada, Reno, NV (United States)


    Textural and mineralogic evidence exists for at least one episode of widespread hydrothermal alteration of volcanic rocks deep in Yucca Mountain, Nevada. Despite this evidence, Castor et al. infer that most of the pyrite found in tuffs at Yucca Mountain was introduced as ejecta (lithic fragments) incorporated during the eruptions of the tuffs, rather than by in-situ hydrothermal activity. Their conclusions appear to be based on their observation that most of the pyrite resides in unaltered to variably altered and veined lithic fragments, whereas pyrite-bearing veins are absent in the tuff matrix, titanomagnetite and mafic phenocrysts in the matrix are generally not replaced by pyrite, and feldspar phenocrysts in the pyritic tuff matrix are generally unaltered. Castor et al. dismiss the much smaller quantities of pyrite disseminated in the tuff matrix, including relatively rare pyritized hornblende and biotite grains, as xenolithic as well. The pyritic tuffs belong to large-volume, subalkaline rhyolite ash-flow units (ca. > 150 to 250 km{sup 3} each). The interpretation of Castor et al. has broad implications for the temperature, fO{sub 2} and fS{sub 2} of major ash flow eruptions. Pyrite origin also bears on the nature of past fluid flow and water-rock reactions at Yucca Mountain, which in turn are important factors in assessing the potential for currently undiscovered mineral resources in the area of the proposed nuclear waste repository. We have studied core and cuttings from the same drill holes studied by Castor et al., as well as other drill holes. It is our contention that the inconsistent lateral and stratigraphic distribution of the pyrite, textural features of the pyrite, and phase stability considerations are incompatible with the {open_quotes}lithic{close_quotes} origin of Castor et al., and are more reasonably explained by in-situ formation from hydrothermal fluids containing low, but geochemically significant, concentrations of reduced sulfur.

  6. Pyrite Surface after Thiobacillus ferrooxidans Leaching at 30℃

    Institute of Scientific and Technical Information of China (English)


    In order to investigate the effect of Thiobacillus ferrooxidans on the oxidation of pyrite, two parallel experiments, which employed H2SO4 solutions and acidic solutions inoculated with Thiobacillus ferrooxidans, were designed and carried out at 30℃. The initial pH of the two solutions was adjusted to 2.5 by dropwise addition of concentrated sulphuric acid. The surfaces of pyrite before exposure to leaching solutions and after exposure to the H2SO4 solutions and acidic solutions inoculated with Thiobacillus ferrooxidans were observed by scanning electron microscopy (SEM). There were a variety of erosion patterns by Thiobacillusferrooxidans on the bio-leached pyrite surfaces. A conclusion can be drawn that the oxidation of pyrite might have been caused by erosion of the surfaces.Attachment of the bacteria to pyrite surfaces resulted in erosion pits, leading to the oxidation of pyrite.It is possible that the direct mechanism plays the most important role in the oxidation of pyrite. The changes in iron ion concentrations of both the experimental solutions with time suggest that Thiobacillus ferrooxidans can enhance greatly the oxidation of pyrite.

  7. Selective separation of pyrite and chalcopyrite by biomodulation. (United States)

    Chandraprabha, M N; Natarajan, K A; Modak, Jayant M


    Selective separation of pyrite from other associated ferrous sulphides at acidic and neutral pH has been a challenging problem. This paper discusses the utility of Acidithiobacillus ferrooxidans for the selective flotation of chalcopyrite from pyrite. Consequent to interaction with bacterial cells, pyrite remained depressed even in the presence of potassium isopropyl xanthate collector while chalcopyrite exhibited significant flotability. However, when the minerals were conditioned together, the selectivity achieved was poor due to the activation of pyrite surface by the copper ions in solution. The selectivity was improved when the sequence of conditioning with bacterial cells and collector was reversed, since the bacterial cells were able to depress collector interacted pyrite effectively, while having negligible effect on chalcopyrite. The observed behaviour is analysed and discussed in detail. The separation obtained was significant both at acidic and alkaline pH. This selectivity achieved was retained when the minerals were interacted with both bacterial cells and collector simultaneously.

  8. An improved pyrite pretreatment protocol for kinetic and isotopic studies (United States)

    Mirzoyan, Natella; Kamyshny, Alexey; Halevy, Itay


    An improved pyrite pretreatment protocol for kinetic and isotopic studies Natella Mirzoyan1, Alexey Kamyshny Jr.2, Itay Halevy1 1Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel 2Geological and Environmental Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel Pyrite is one of the most abundant and widespread of the sulfide minerals with a central role in biogeochemical cycles of iron and sulfur. Due to its diverse roles in the natural and anthropogenic sulfur cycle, pyrite has been extensively studied in various experimental investigations of the kinetics of its dissolution and oxidation, the isotopic fractionations associated with these reactions, and the microbiological processes involved. Pretreatment of pyrite for removal of oxidation impurities to prevent experimental artifacts and inaccuracies is often practiced. While numerous pyrite-cleaning methods have been used in experiments, a common pyrite pretreatment method, often used to investigate pyrite chemistry by the isotopic fractionations associated with it, includes several rinses by HCl, acetone and deionized water. Elemental sulfur (S0) is a common product of incomplete pyrite oxidation. Removal of S0 is desirable to avoid experimental biases associated with its participation in pyrite transformations, but is more complicated than the removal of sulfate. Although rinsing with an organic solvent is in part aimed at removing S0, to the best of our knowledge, the extraction efficiency of S0 in existing protocols has not been assessed. We have developed and tested a new protocol for elemental sulfur removal from the surface of pyrite by ultrasonication with warm acetone. Our data demonstrate the presence of large fractions of S0 on untreated pyrite particle surfaces, of which only approximately 60% was removed by the commonly used pretreatment method. The new protocol described here was found to be more efficient at S0 removal than the commonly used method

  9. Greigite: a true intermediate on the polysulfide pathway to pyrite

    Directory of Open Access Journals (Sweden)

    Benning Liane G


    Full Text Available Abstract The formation of pyrite (FeS2 from iron monosulfide precursors in anoxic sediments has been suggested to proceed via mackinawite (FeS and greigite (Fe3S4. Despite decades of research, the mechanisms of pyrite formation are not sufficiently understood because solid and dissolved intermediates are oxygen-sensitive and poorly crystalline and therefore notoriously difficult to characterize and quantify. In this study, hydrothermal synchrotron-based energy dispersive X-ray diffraction (ED-XRD methods were used to investigate in situ and in real-time the transformation of mackinawite to greigite and pyrite via the polysulfide pathway. The rate of formation and disappearance of specific Bragg peaks during the reaction and the changes in morphology of the solid phases as observed with high resolution microscopy were used to derive kinetic parameters and to determine the mechanisms of the reaction from mackinawite to greigite and pyrite. The results clearly show that greigite is formed as an intermediate on the pathway from mackinawite to pyrite. The kinetics of the transformation of mackinawite to greigite and pyrite follow a zero-order rate law indicating a solid-state mechanism. The morphology of greigite and pyrite crystals formed under hydrothermal conditions supports this conclusion and furthermore implies growth of greigite and pyrite by oriented aggregation of nanoparticulate mackinawite and greigite, respectively. The activation enthalpies and entropies of the transformation of mackinawite to greigite, and of greigite to pyrite were determined from the temperature dependence of the rate constants according to the Eyring equation. Although the activation enthalpies are uncharacteristic of a solid-state mechanism, the activation entropies indicate a large increase of order in the transition state, commensurate with a solid-state mechanism.

  10. Pyrite surface characterization and control for advanced fine coal desulfurization technologies

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiang-Huai.


    The objective of this project is to conduct extensive studies on the surface reactivity of pyrite by using electrochemical, surface analysis, potentiometric and calorimetric titration, and surface hydrophobicity characterization techniques and to correlate the alteration of the coal-pyrite surface with the efficiency of pyrite rejection in coal flotation. The products as well as their structure, the mechanisms and the kinetics of the oxidation of coal-pyrite surfaces and their interaction with various chemical reagents will be systematically studied and compared with that of mineral-pyrite and synthetic pyrite to determine the correlation between the surface reactivity of pyrite and the bulk chemical properties of pyrite and impurities. The surface chemical studies and the studies of floatability of coal-pyrite and the effect of various parameters such as grinding media and environment, aging under different atmospheres, etc. on thereof, are directed at identifying the causes and possible solutions of the pyrite rejection problems in coal cleaning.

  11. The effect of quartz on the flotation of pyrite depressed by serpentine

    Directory of Open Access Journals (Sweden)

    Bo Feng


    Full Text Available The effect of quartz particles on the flotation of pyrite depressed by serpentine has been investigated through flotation tests, adsorption tests, zeta potential measurements and DLVO calculation. The results show that the presence of hydrophilic serpentine slimes on pyrite surface reduces collector adsorption and results in lower recovery of pyrite. The finer the serpentine slime is, the lower the pyrite recovery will be. Quartz particles do not interfere with pyrite flotation. However, the addition of quartz particles increases the adsorption of collector on pyrite surface and limits the detrimental effect of serpentine on pyrite flotation. The fine-grained quartz is more effective. Zeta potential measurements and DLVO calculation illustrate that the zeta potential of quartz is more negative than that of pyrite and the attraction force between serpentine and quartz is stronger than force between serpentine and pyrite, thus some serpentine slimes were transferred from pyrite surface to quartz in the process of attrition.

  12. Electrodeposition of dixanthogen(TETD) on pyrite surface

    Institute of Scientific and Technical Information of China (English)

    LI Wei-zhong; QIN Wen-qing; SUN Wei; QIU Guan-zhou


    The electrochemical reaction of xanthate on the surface of pyrite was studied using cyclic voltammogrametry, chronopotentiometry and rotating-disc electrode measurements. Experimental results demonstrate that the first step in the reaction is electrochemical adsorption of xanthate ion, and then the adsorbed ion associates with a xanthate ion from the solution and forms a dixanthogen on the pyrite electrode surface. The diffusion coefficient of butyl xanthate on pyrite electrode surface can be determined to be about 1.09×10-6 cm2/s. Using the galvanostatic technique, the kinetic parameters of oxidation of the butyl xanthate ion on the pyrite surface are calculated as Ja=200 μA/cm2, β= 0.203 and J0=27.1 μA/cm2.

  13. Magnetic properties related to thermal treatment of pyrite

    Institute of Scientific and Technical Information of China (English)


    Detailed rock magnetic experiments were conducted on high-purity natural crystalline pyrite and its products of thermal treatments in both argon and air atmospheres. In argon atmosphere (reducing environment), the pyrite is altered by heating to magnetite and pyrrhotite; the latter is stable in argon atmosphere, and has coercive force and coercivity of remanence of ~20 and ~30 mT, respectively. Whereas in air, the pyrite is ultimately oxidized to hematite. First order reversal curve (FORC) diagram of the end product shows that the remanence coercivity of hematite is up to ~1400 mT. The corresponding thermal transformation process of pyrite in air can be simply summarized as pyrite→ pyrrhotite→magnetite→hematite. These results are helpful for understanding of sedimentary magnetism, secondary chemical remanence and meteorolite magnetic properties.

  14. Magnetic properties related to thermal treatment of pyrite

    Institute of Scientific and Technical Information of China (English)

    WANG Lei; PAN YongXin; LI JinHua; QIN HuaFeng


    Detailed rock magnetic experiments were conducted on high-purity natural crystalline pyrite and its products of thermal treatments in both argon and air atmospheres. In argon atmosphere (reducing environment), the pyrite is altered by heating to magnetite and pyrrhotite; the latter is stable in argon atmosphere, and has coercive force and coercivity of remanence of ~20 and ~30 mT, respectively.Whereas in air, the pyrite is ultimately oxidized to hematite. First order reversal curve (FORC) diagram of the end product shows that the remanence coercivity of hematite is up to ~1400 mT. The corresponding thermal transformation process of pyrite in air can be simply summarized as pyrite→pyrrhotite→magnetite→hematite. These results are helpful for understanding of sedimentary magnetism, secondary chemical remanence and meteorolite magnetic properties.

  15. Improving Consistency in Laser Ablation Geochronology (United States)

    Horstwood, Matt; Gehrels, George; Bowring, James


    Workshop on Data Handling in LA-ICP-MS U-Th-Pb Geochronology; San Francisco, California, 12-13 December 2009; The use of uranium-thorium-lead (U-Th-Pb) laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) geochronology involves rapid analysis of U-and Th-rich accessory minerals. It routinely achieves 1-2% precision for U-Th-Pb dates constituting detrital mineral age spectra and for dating igneous and metamorphic events. The speed and low setup and analysis cost of LA-ICP-MS U-Th-Pb geochronology has led to a proliferation of active laboratories. Tens of thousands of analyses are produced per month, but there is little agreement on how to transform these data into accurate U-Th-Pb dates. Recent interlaboratory blind comparisons of zircon samples indicate that resolvable biases exist among laboratories and the sources of bias are not fully understood. Common protocols of data reduction and reporting are essential for scientists to be able to compare and interpret these data accurately.

  16. Nannobacteria and the formation of framboidal pyrite: Textural evidence

    Indian Academy of Sciences (India)

    Robert L Folk


    Study of sedimentary pyrite in the form of framboids, euhedral crystals or metasomatic masses has revealed that their surfaces are commonly covered with spheroids of about 50 nm. This applies to all the examples studied, from modern to Proterozoic. These spheroids are interpreted as the pyritized corpses of nannobacterial cells; if correct, this indicates that precipitation of iron sulfide was performed by these dwarf forms of bacteria, often associated with decaying organic matter.

  17. Rapid method to determine proximate analysis and pyritic sulfur

    Energy Technology Data Exchange (ETDEWEB)

    Rowe, M.W.; Hyman, M.


    The use of thermomagnetogravimetry has been proposed as an alternative to the ASTM methods for measuring the pyritic sulphur content of coal and for proximate analysis. This paper presents a comparison of the results of thermogravimetry for proximate analysis and thermomagnetometry for pyritic sulphur with ASTM values on the same samples. The thermomagnetogravimetric technique is quicker and easier than the ASTM methods, and of comparable accuracy.

  18. Enabling iron pyrite (FeS2) and related ternary pyrite compounds for high-performance solar energy applications (United States)

    Caban Acevedo, Miguel

    The success of solar energy technologies depends not only on highly efficient solar-to-electrical energy conversion, charge storage or chemical fuel production, but also on dramatically reduced cost, to meet the future terawatt energy challenges we face. The enormous scale involved in the development of impactful solar energy technologies demand abundant and inexpensive materials, as well as energy-efficient and cost-effective processes. As a result, the investigation of semiconductor, catalyst and electrode materials made of earth-abundant and sustainable elements may prove to be of significant importance for the long-term adaptation of solar energy technologies on a larger scale. Among earth-abundant semiconductors, iron pyrite (cubic FeS2) has been considered the most promising solar energy absorber with the potential to achieve terawatt energy-scale deployment. Despite extensive synthetic progress and device efforts, the solar conversion efficiency of iron pyrite has remained below 3% since the 1990s, primarily due to a low open circuit voltage (V oc). The low photovoltage (Voc) of iron pyrite has puzzled scientists for decades and limited the development of cost-effective solar energy technologies based on this otherwise promising semiconductor. Here I report a comprehensive investigation of the syntheses and properties of iron pyrite materials, which reveals that the Voc of iron pyrite is limited by the ionization of a high density of intrinsic bulk defect states despite high density surface states and strong surface Fermi level pinning. Contrary to popular belief, bulk defects most-likely caused by intrinsic sulfur vacancies in iron pyrite must be controlled in order to enable this earth-abundant semiconductor for cost-effective and sustainable solar energy conversion. Lastly, the investigation of iron pyrite presented here lead to the discovery of ternary pyrite-type cobalt phosphosulfide (CoPS) as a highly-efficient earth-abundant catalyst material for

  19. Pyrite and pyritic mill tailing as a source of iron in a calcareous iron-deficient soil

    Energy Technology Data Exchange (ETDEWEB)

    Barrau, E.M.; Berg, W.A.


    Mill wastes from ore processing, particularly acid-forming pyrites, often pose disposal problems. This greenhouse study evaluated pyrite and a pyritic mill tailing as Fe sources on an Fe-deficient calcareous soil. Pyrite and tailing <0.1 mm in diameter were applied at rates of 45 and 135 metric ton/ha. Controls, 200 and 600 ppM Fe as Fe/sub 2/(SO/sub 4/)/sub 3/ and 5 and 15 ppM Fe as FeEDDHA, were used as standards. The treatments were seeded with sudangrass (Sorghum vulgare sudanense) and six successive crops were harvested. Sudangrass yields increased 160 to 200% with pyrite and tailing treatments; these yields were significantly greater than the control and were comparable to yields from the other Fe sources. The 5 ppM FeEDDHA treatment, however, increased yield for only the first two crops. Plant-available soil Fe measured by DTPA extraction increased with all Fe treatments, while the levels of DTPA-extractable Zn and Mn remained the same or increased slightly. DTPA-extractable Cu doubled with the high rate of pyrite addition. The concentration of Fe in the plants remained the same or increased slightly with the Fe treatments, while concentrations of Zn, Cu, and Mn all decreased.

  20. Cold seep carbonates along the Norwegian margin, insights into U-Th geochronology and S geochemistry (United States)

    Cremiere, A.; Lepland, A.; Wing, B. A.; Sahy, D.; Condon, D. J.; Chand, S.; Noble, S. R.; Bui, T. H.; Thorsnes, T.; Brunstad, H.


    Cold seep carbonates along the Norwegian margin, insights into U-Th geochronology and S geochemistryAuthigenic carbonate crusts form in shallow subsurface of marine sediments due to the microbial anaerobic oxidation of methane (AOM). As a result they are unique archives of the locus and intensity of past methane seepage that can be dated by using U-daughter decay affording the unique opportunity to constrain the absolute timing of methane release events. Because AOM is mainly driven by the microbial reduction of seawater sulfate, multiple sulfur isotope compositions of paired carbonate-associated sulfate (CAS) and pyrite in seep carbonates taken as proxies for porewater sulfate and sulfide, respectively, have the potential to reconstruct the biogeochemical conditions under which seep carbonates precipitate. Methane-derived carbonate crusts were collected from several seepage sites on the Norwegian continental shelf, including sites in the North Sea, the Norwegian Sea and the Barents Sea. The U-Th dating results constrain the main episode of carbonate crust formation in the Barents and Norwegian seas during the time interval between 14 and 7 ka. Such ages suggest that the methane seepage along the northern Norwegian margin was most active after the collapse of the Scandinavian ice sheet and deglaciation of the area that took place at about 15 ka. The methane flux for the carbonate crust formation was likely provided by the dissociation of methane hydrates that extensively formed in underlying sediments during the last glacial period, but became unstable due to depressuring effects of retreating ice sheet. The precipitation of studied North Sea carbonate crusts occurred more recently, from 6 to 1 ka, suggesting that their formation is unrelated to the glacial history of the area. The paired sulfur stable isotope compositions of pyrite-CAS record a large range of fractionation factors (from 30 to 70 ‰) reflecting change of sulfate-reduction rates possibly controlled

  1. Geochemical characteristics of pyrite in Duolanasayi gold deposit, Xinjiang

    Institute of Scientific and Technical Information of China (English)

    CHEN Guodong; XIAO Huiliang; WANG Henian; ZHOU Jiyuan


    The Duolanasayi gold deposit, 60 km NW of Habahe County, Xinjiang Uygur Autonomous Region, is a mid-large-scale gold deposit controlled by brittle-ductile shearing, and superimposed by albitite veins and late-stage magma hydrothermal solutions. There are four types of pyrite, which are contained in the light metamorphosed rocks (limestone, siltstone), altered-mineralized rocks (chlorite-schist, altered albite-granite, mineralized phyllite), quartz veins and carbonatite veinlets. The pyrite is the most common ore mineral. The Au-barren pyrite is present mainly in a simple form and gold-bearing pyrite is present mainly in a composite form. From the top downwards, the pyrite varies in crystal form from {100} and {210}+{100} to {210}+{100}+{111} to {100}+{111}. Geochemical studies indicate that the molecular contents of pyrite range from Fe1.057S2 to Fe0.941S2. Gold positively correlates with Mn, Sr, Zn, Te, Pb, Ba and Ag. There are four groups of trace elements: Fe-Cu-Sr-Ag, Au-Te-Co, As-Pb-Zn and Mn-V-Ti-Ba-Ni-Cr in pyrite. The REE characteristics show that the total amount of REE (ΣREE) ranges from 32.35×10 -6 to 132.18×10 -6; LREE/HREE, 4.466-9.142; (La/Yb)N, 3.719-11.133; (Eu/Sm)N, 0.553-1.656; (Sm/Nd)N, 0.602-0.717; La/Yb, 6.26-18.75; δEu, 0.628-2.309; δCe, 0.308-0.816. Sulfur isotopic compositions (δ 34S=-2.46‰--7.02‰) suggest that the sulfur associated with gold mineralization was derived from the upper mantle or lower crust.

  2. Establishing Denudation Chronology through Weathering Geochronology (United States)

    Riffel, S. B.; Vasconcelos, P. M.; Farley, K. A.; Carmo, I. O.


    Planar landforms - erosion surfaces - are used as temporal markers in denudation chronology. These surfaces are interpreted as the result of long-term weathering and denudation controlled by a specific base level within a given time-interval characterized by long-term tectonic stability. The presence of several planar landforms at distinct elevations is interpreted as evidence for distinct denudation events, separated by periods of tectonic reactivation and crustal uplift. We selected an area in the Paraná-La Plata basin, southern Brazil (25°S lat.) to investigate if the application of weathering geochronology by the 40Ar/39Ar and (U-Th)/He methods could permit differentiating different elevation landsurfaces. We dated supergene Mn oxyhydroxides by 40Ar/39Ar geochronology and coexisting supergene Fe oxyhydroxides by the (U-Th)/He method from one of the three regional landsurfaces - The First, Second, and Third Paraná plateaus - previously identified in this area. Two sites were sampled from the Second Paraná Plateau: a ferricrust at Serra das Almas (7 hand specimens of goethite at 1080 m of altitude) and deeply weathered ferricretes and saprolites at Vila Velha (11 hand specimens of cryptomelane and 14 of goethite at 910 m of altitude). The Serra das Almas sites hosts a stratified weathering profile with ferricrust, and mottle zone. The Vila Velha site results from intense weathering that led to the precipitation of well-crystallized supergene minerals precipitated within fractures in the saprolites. The geochronological results are correlatable between the two sites and the two distinct methods (40Ar/39Ar and (U-Th)/He), and they reveal three generations of weathering and mineral precipitation: Late Eocene-Oligocene, Early Miocene, and Pleistocene. The geochronological results suggested that the Second Paraná Plateau formed by regional erosion during the Oligocene, and that this landsurface has been continuously exposed to weathering and erosion since then

  3. Arsenic incorporation into authigenic pyrite, Bengal Basin sediment, Bangladesh (United States)

    Lowers, H.A.; Breit, G.N.; Foster, A.L.; Whitney, J.; Yount, J.; Uddin, Md. N.; Muneem, Ad. A.


    Sediment from two deep boreholes (???400 m) approximately 90 km apart in southern Bangladesh was analyzed by X-ray absorption spectroscopy (XAS), total chemical analyses, chemical extractions, and electron probe microanalysis to establish the importance of authigenic pyrite as a sink for arsenic in the Bengal Basin. Authigenic framboidal and massive pyrite (median values 1500 and 3200 ppm As, respectively), is the principal arsenic residence in sediment from both boreholes. Although pyrite is dominant, ferric oxyhydroxides and secondary iron phases contain a large fraction of the sediment-bound arsenic between approximately 20 and 100 m, which is the depth range of wells containing the greatest amount of dissolved arsenic. The lack of pyrite in this interval is attributed to rapid sediment deposition and a low sulfur flux from riverine and atmospheric sources. The ability of deeper aquifers (>150 m) to produce ground water with low dissolved arsenic in southern Bangladesh reflects adequate sulfur supplies and sufficient time to redistribute the arsenic into pyrite during diagenesis.

  4. Pyrite oxidation under simulated acid rain weathering conditions. (United States)

    Zheng, Kai; Li, Heping; Wang, Luying; Wen, Xiaoying; Liu, Qingyou


    We investigated the electrochemical corrosion behavior of pyrite in simulated acid rain with different acidities and at different temperatures. The cyclic voltammetry, polarization curve, and electrochemical impedance spectroscopy results showed that pyrite has the same electrochemical interaction mechanism under different simulated acid rain conditions, regardless of acidity or environmental temperature. Either stronger acid rain acidity or higher environmental temperature can accelerate pyrite corrosion. Compared with acid rain having a pH of 5.6 at 25 °C, the prompt efficiency of pyrite weathering reached 104.29% as the acid rain pH decreased to 3.6, and it reached 125.31% as environmental temperature increased to 45 °C. Increasing acidity dramatically decreases the charge transfer resistance, and increasing temperature dramatically decreases the passivation film resistance, when other conditions are held constant. Acid rain always causes lower acidity mine drainage, and stronger acidity or high environmental temperatures cause serious acid drainage. The natural parameters of latitude, elevation, and season have considerable influence on pyrite weathering, because temperature is an important influencing factor. These experimental results are of direct significance for the assessment and management of sulfide mineral acid drainage in regions receiving acid rain.

  5. Hydrogeologic and environmental impact of amjhore pyrite mines, India (United States)

    Choubey, Vishnu D.; Rawat, Rajendra K.


    Drainage from active and inactive pyrite mines has produced chemical and physical pollution of both ground- and surface water in Amjhore region. In the present case, chemical pollution is caused by exposing pyrite minerals to oxidation or leaching, resulting in undesirable concentrations of dissolved materials. Pyrite mining suddenly exposed large quantities of sulfides to direct contact with oxygen, and oxidation proceeds rapidly, resulting in acidity and release of metal (Fe) and sulfates to the water system, eventually resulting in water pollution in the region. The magnitude and impact of the problem is just being recognized and, as the present and the future projected demand for clean water is of top priority, the present studies were undertaken. Mine drainage includes water flowing from the surface and underground mines and runoff or seepage from the pyrite mines. This article describes the various hydrologic factors that control acid water formation and its transport. The mine drainage is obviously a continuing source of pollution and, therefore, remedial measures mainly consisting of a double-stage limestone-lime treatment technique have been suggested. The present results will be used to develop an alternative and more effective abatement technology to mitigate acid production at the source, namely, the technique of revegetation of the soil cover applied to the waste mine dump material. Water quality change is discussed in detail, with emphasis on acidity formed from exposed pyrite material and on increase in dissolved solids. Preventive and treatment measures are recommended.

  6. Hydrogeological and environmental impact of Amjhore pyrite mines, India

    Energy Technology Data Exchange (ETDEWEB)

    Choubey, V.D.; Rawat, R.K. (Indian School of Mines, Dhanbad (India))

    Drainage from active and inactive pyrite mines has produced chemical and physical pollution of both ground and surface water in Amjhore region. In the present case, chemical pollution is caused by exposing pyrite minerals to oxidation or leaching, resulting in undesirable concentrations of dissolved materials. Pyrite mining suddenly exposed large quantities of sulfides to direct contact with oxygen, and oxidation proceeds rapidly, resulting in acidity and release of metal (Fe) and sulfates to the water system, eventually resulting in water pollution in the region. The magnitude and impact of the problem is just being recognized and, as the present and the future projected demand for problem demand for clean water is of top priority, the present studies were undertaken. Mine drainage includes water flowing from the surface and underground mines and runoff or seepage from the pyrite mines. This article describes the various hydrologic factors that control acid water formation and its transport. The mine drainage is obviously a continuing source of pollution and, therefore, remedial measures mainly consisting of a double-stage limestone-lime treatment technique have been suggested. The present results will be used to develop an alternative and more effective abatement technology to mitigate acid production at the source, namely, the technique of revegetation of the soil cover applied to the waste mine dump material. Water quality change is discussed in detail, with emphasis on acidity formed from exposed pyrite material and on increase in dissolved solids. Preventive and treatment measures are recommended.

  7. Re-Os isotopic age dating of molybdenite separates from Hashitu Mo deposit in Linxi County of Inner Mongolia and its geological significance%内蒙古林西县哈什吐钼矿床辉钼矿铼-锇年龄及其地质意义

    Institute of Scientific and Technical Information of China (English)

    张可; 聂凤军; 侯万荣; 李超; 刘勇


    Located in the eastern part of the southern Da Hinggan Ling Late Paleozoic orogenic belt between the Silas Wood Aaron River and the Erlian-Hegenshan structure zone, the newly discovered Hashitu ore deposit is a medium-size porphyry molybdeoum deposit occurring in east-central Inner Mongolian. The Hashitu granite porphyry and biotite granite were emplaced in the widespread Quaternary sedimentary sequence in the Hashitu mineralized area. The granite porphyry intruded into the biotite granite in a slightly later period, and the two granite intrusions made up a Yanshanian complex. The Mo mineralization occurred entirely in the two types of Mesozoic granitic intrusive rocks in stratiform, lenticular and chambered forms at large steep angles. The metallic minerals of the ores from Hashitu are mainly molybdenite and subordinate, pyrite, chalcopyrite, pyrrhotite, arsenopyrite and galena, whereas the gangue mineral assemblage consists of mainly quartz, sericite and subordinately chlorite, epidote, fluorite and feldspar. Re-Os isotopic age dating of ten molybdenite separates from No. 1 Mo ore body yielded an isochron age of (148.8 ± 1.6) Ma and model ages ranging from (147.0 ± 2.2) Ma to (149.5 ± 2.3) Ma with an average of (148.22 ± 0.67) Ma. As the age is in agreement with field geological evidence, the authors hold that the molybdenum was concentrated from the Mo-bearing hydrothermal fluid after the intrusion of the granite porphyry and biotite granite during the Late Jurassic period. The Re content of molybdenite is (652~2 055) × 10-9, averaging 1 284 × 10-9. The content of Re in the Hashitu Mo deposit in comparison with the Re values of other molybdenum-bearing deposits indicates that the ore-forming materials of the Hashitu Mo deposit might have been derived mainly from the crustal source.%内蒙古哈什吐矿床是新发现的钼矿床.为进一步查明哈什吐钼矿床的形成时间,首次对主要钼矿体的10件辉钼矿样品进行铼-锇同位素分

  8. A study of the interfacial chemistry of pyrite and coal in fine coal cleaning using flotation

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Chengliang [Univ. of Kentucky, Lexington, KY (United States)


    Surface oxidation, surface charge, and flotation properties have been systematically studied for coal, coal-pyrite and ore-pyrite. Electrochemical studies show that coal-pyrite exhibits much higher and more complex surface oxidation than ore-pyrite and its oxidation rate depends strongly on the carbon/coal content. Flotation studies indicate that pyrites have no self-induced floatability. Fuel oil significantly improves the floatability of coal and induces considerable flotation for coal-pyrite due to the hydrophobic interaction of fuel oil with the carbon/coal inclusions on the pyrite surface. Xanthate is a good collector for ore-pyrite but a poor collector for coal and coal-pyrite. The results from thermodynamic calculations, flotation and zeta potential measurements show that iron ions greatly affect the flotation of pyrite with xanthate and fuel oil. Various organic and inorganic chemicals have been examined for depressing coal-pyrite. It was found, for the first time, that sodium pyrophosphate is an effective depressant for coal-pyrite. Solution chemistry shows that pyrophosphate reacts with iron ions to form stable iron pyrophosphate complexes. Using pyrophosphate, the complete separation of pyrite from coal can be realized over a wide pH range at relatively low dosage.

  9. Investigating Age Resolution in Laser Ablation Geochronology (United States)

    Horstwood, Matt; Kosler, Jan; Jackson, Simon; Pearson, Norman; Sylvester, Paul


    Workshop on Data Handling in LA-ICP-MS U-Th-Pb Geochronology; Vancouver, British Columbia, Canada, 12-13 July 2008; Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) uranium-thorium-lead (U-Th-Pb) dating is an increasingly popular approach for determining the age of mineral grains and the timing of geological events. The spatial resolution offered by this technique allows detailed investigations of complex igneous and metamorphic processes, and the speed of data capture allows vast amounts of information to be gathered rapidly. Laser ablation U-Th-Pb dating is therefore becoming an increasingly influential technique to the geochronology community, providing cost-effective and ready access to age data for laboratories and end users worldwide. However, complications in acquiring, processing, and interpreting data can lead to inaccurate age information entering the literature. With the numbers of practitioners expanding rapidly, the need to standardize approaches and resolve difficulties (particularly involving the subjectivity in processing laser ablation U-Th-Pb data) is becoming important.

  10. Biogenic syngenetic pyrite from tuffaceous sedimentary RF3-V rocks (United States)

    Kozyreva, Irina; Nikulova, Natalia


    Biogenic framboidal pyrite was found in intraformational tuffaceous sedimentary gravelites, within basic volcanites (RF3-V) in Subpolar Urals (Sablya Ridge). Pyrite grains (Fe 44.07-44,33, S 50.22-53.31 wt. %) are composed of ball-like microconcretions, sometimes intergrown with crystals of pentagondodecahedron and cubic habit. The microconcretions (20 to 40 mcm) are roundish and composed of microcrystals, which end faces form spherical surface. The nuclei of the microconcretions are represented by frambohedrons 4-5 mcm in size, which are pyritized cells of sulphate-reducing colonial coccoid microfossils. The formation of the frambohedrons occurred synchronously to sedimentation in stagnant reducing environment at interaction of biogenic hydrogen sulphide with water-dissolved iron. The biogenic hydrogen sulphide is reduced by microorganisms in the conditions of free and unrestricted access of dissolved sulphate ions sourced from sulphur of fumarole gases. Iron came from washed-out basic volcanites. The growth of outer radial parts of microconcretions occurred during compaction of sediments in diagenetic stage. The quantity of dissolved sulphate and iron during pyrite formation exceeded possibilitites of bacterial "starters" which resulted in the formation of pyrites of other morphological varieties. This is confirmed by the accretion of concentric rays of the concretions and cubic microcrystals of pyrite in the aggregate grains. The formation of tuffaceous sediments occurred during temporary decrease of volcanic activity in a continuous linear water flow with stagnant areas composed of water-displaced pebbles from underlying metaterrigenous rocks (RF 1-2), which were exposed beyond the development area of volcanic strata, unchanged clasts of recent and synchronously formed basic and medium volcanites with participation of air-driven ashes and influence of volcanic gases in the presence of sulphate-reducing bacteria. The work is financially supported by the Program

  11. Mechanism of separating pyrite and dolomite by flotation

    Institute of Scientific and Technical Information of China (English)

    Anping Liu; Wen Ni; Wei Wu


    To study the mechanism of separating pyrite and dolomite by flotation, the acting mechanisms of WHL depressor and both the minerals were studied by means of thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrareddiffuse reflection spectroscopy (FTIR-DRS), and X-ray photoelectron spectroscopy (XPS). The results indicated that WHL formed metal salts with metal ions dissolved in water from dolomite and pyrite, which then deposited on their surfaces. Both of the minerals could be depressed by WHL. In the process of flotation, sulfur was created besides the WHL being absorbed on the surface of the sulfur concentrate, and its recovery rate was slightly affected.

  12. SEM and AFM images of pyrite surfaces after bioleaching by the indigenous Thiobacillus thiooxidans. (United States)

    Liu, H-L; Chen, B-Y; Lan, Y-W; Cheng, Y-C


    The bioleaching mechanism of pyrite by the indigenous Thiobacillus thiooxidans was examined with the aid of scanning electron microscopy (SEM) and atomic force microscopy (AFM) images of the pyrite surface. The presence of pyrite eliminated the lag phase during growth of this microorganism. This was due to the stimulatory effect on cell growth of the slight amount of Cu2+ that had leached from the pyrite. Zn2+ was found to be much more readily solubilized than Cu2+. The efficiency of bioleaching was four times higher than that of chemical leaching. SEM images provided evidence of direct cell attachment onto the pyrite surface, thereby enhancing the bioleaching rate. Furthermore, extracellular polymeric substances (EPSs) were found on the pyrite surface after 4 days of oxidation. AFM images showed that the pyrite surface area positively correlated with the oxidation rate. A combination of direct and indirect mechanism is probably responsible for the oxidation of pyrite by T. thiooxidans.

  13. Study of possibilities of pyrite content reduction in black coals from the Mecsek Area

    Energy Technology Data Exchange (ETDEWEB)

    Petho, S.; Bokanyi, L.


    Certain parts of the pyrite content of coals can be removed by physical methods in inorganic form. The pyrite content of the Hungarian black coals as well as the pyrite distribution, as a function of density and grain size, are discussed. Based on literature data and laboratory experiments the pyrite content reduction by means of flotation, magnetic and gravitation enrichment is dealt with. Conclusions are drawn on how to apply these different procedures in black coal processing in Hungary.

  14. Semiconductor electrochemistry of coal pyrite. Final technical report, September 1990--September 1995

    Energy Technology Data Exchange (ETDEWEB)

    Osseo-Asare, K.; Wei, D.


    This project is concerned with the physiochemical processes occuring at the pyrite/aqueous interface, in the context of coal cleaning, desulfurization, and acid mine drainage. The use of synthetic particles of pyrite as model electrodes to investigate the semiconductor electrochemistry of pyrite is employed.

  15. Galvanic interaction between galena and pyrite in an open system

    Institute of Scientific and Technical Information of China (English)

    ZHOU Li; LI Heping; XU Liping


    Galvanic interactions between sulfide minerals have very important influences on hydrometallurgical processes, the supergene enrichment of sulfides and the formation of acid mine drainage. By changing the concentrations of Fe3 + , the pH values, status of the flowing of the solution and the solution salinity ( e. g. the concentrations of Na2 SO4 ) and monitoring the galvanic currents and potentials, studies were conducted in this work on the galvanic interaction between pyrite acting as the anode and galena acting as the cathode. The results indicated that the concentrations of Fe3 + , pH values and the flowing of the solution exhibit a great effect on the galvanic interaction of galena-pyrite couple, while the salinity of the solution has only a slight influence on the interaction. The experiments also revealed that in case cracks exist on the surface of pyrite electrode, the potential of pyrite will decrease so sharply as to be lower than that of galena under the same experimental condition. The experimental results were explained in terms of the Butler-Volume equation and the theory of mixed potential.

  16. Contribution of microorganisms to the oxidation of pyrite

    NARCIS (Netherlands)

    Arkesteyn, G.J.M.W.


    Optimum conditions for the accumulation of substantial amounts of pyrite (FeS 2 ) in the sediment are found in estuarine areas, especially in the tropics. In such areas anaerobic conditions prevail owing to continuous saturation with water. There is an abundant supply of organic matter, i

  17. Characterization and separation of pyrite from Abu Tartur black shale

    Institute of Scientific and Technical Information of China (English)

    Ibrahim S.S.; El Kammar A.M.; Guda A.M.


    This work aimed for pyrite separation from Abu Tartur black shale as a source of sulfur to be an added economic value of Abu Tartur area. The considered samples in the present work were collected from a core drilled in Abu Tartur plateau representing the pyrite-rich black shale of the U. Cretaceous age. Sample characterization was carried out using petrographic microscope, XRD, DTA/DTG, C/S and XRF techniques. Clay minerals, silt-sized quartz, calcite, and hematite were the main minerals associating pyr-ite (5.34%). Liberation behavior of the sample was about 80%below 5 lm. Sample processing was achieved through one-day soaking followed by classification using 1 inch Mozley hydro-cyclone where about 35.5% by weight went to underflow and 64.5% went to overflow. The underflow product was subjected to an advanced gravity separation process using SB-40 Falcon Concentrator through a CCD statistical design prepared by Design-Expert 6.0 software proposed to opti-mize the separation process through a study for the effects of frequency (Hz) and water pressure (Psi) on both assay and recovery of the sulfur-rich heavy fraction. A heavy concentrate weighed 10.90%with inorganic sulfur content reached 11.37%(21.24%pyrite) with overall recovery (50.01%) was obtained after two cleaning at the optimum conditions.

  18. Investigation of pyrite surface state by DFT and AFM

    Institute of Scientific and Technical Information of China (English)

    先永骏; 聂琪; 文书明; 刘建; 邓久帅


    The surface states of pyrite (FeS2) were theoretically investigated using first principle calculation based on the density functional theory (DFT). The results indicate that both the (200) and (311) surfaces of pyrite undergo significant surface atom relaxation after geometry optimization, which results in a considerable distortion of the surface region. In the normal direction, i.e., perpendicular to the surface, S atoms in the first surface layer move outward from the bulk, while Fe atoms move toward the bulk, forming an S-rich surface. The surface relaxation processes are driven by electrostatic interaction, which is evidenced by a relative decrease in the surface energy after surface relaxation. Such a relaxation process is visually interpreted through the qualitative analysis of molecular mechanics. Atomic force microscopy (AFM) analysis reveals that only sulfur atom is visible on the pyrite surface. This result is consistent with the DFT data. Such S-rich surface has important influence on the flotation properties of pyrite.

  19. The mechanisms of pyrite oxidation and leaching: A fundamental perspective (United States)

    Chandra, A. P.; Gerson, A. R.


    Pyrite is the earth's most abundant sulfide mineral. Its frequent undesirable association with minerals of economic value such as sphalerite, chalcopyrite and galena, and precious metals such as gold necessitates costly separation processes such as leaching and flotation. Additionally pyrite oxidation is a major contributor to the environmental problem of acid rock drainage. The surface oxidation reactions of pyrite are therefore important both economically and environmentally. Significant variations in electrical properties resulting from lattice substitution of minor and trace elements into the lattice structure exist between pyrite from different geographical locations. Furthermore the presence of low coordination surface sites as a result of conchoidal fracture causes a reduction in the band gap at the surface compared to the bulk thus adding further electrochemical variability. Given the now general acceptance after decades of research that electrochemistry dominates the oxidation process, the geographical location, elemental composition and semi-conductor type (n or p) of pyrite are important considerations. Aqueous pyrite oxidation results in the production of sulfate and ferrous iron. However other products such as elemental sulfur, polysulfides, hydrogen sulfide, ferric hydroxide, iron oxide and iron(III) oxyhydroxide may also form. Intermediate species such as thiosulfate, sulfite and polythionates are also proposed to occur. Oxidation and leach rates are generally influenced by solution Eh, pH, oxidant type and concentration, hydrodynamics, grain size and surface area in relation to solution volume, temperature and pressure. Of these, solution Eh is most critical as expected for an electrochemically controlled process, and directly correlates with surface area normalised rates. Studies using mixed mineral systems further indicate the importance of electrochemical processes during the oxidation process. Spatially resolved surface characterisation of fresh

  20. Detrital geochronology of unroofing magmatic complexes (United States)

    Malusà, Marco Giovanni; Villa, Igor Maria; Vezzoli, Giovanni; Garzanti, Eduardo


    Tectonic reconstructions performed in recent years are increasingly based on petrographic (Dickinson & Suczek, 1979; Garzanti et al., 2007) and geochronological (Brandon et al., 1998; DeCelles et al., 2004) analyses of detrital systems. Detrital age patterns are traditionally interpreted as a result of cooling induced by exhumation (Jäger, 1967; Dodson, 1973). Such an approach can lead to infer extremely high erosion rates (Giger & Hurford 1989) that conflict with compelling geological evidence (Garzanti & Malusà, 2008). This indicates that interpretations solely based on exhumational cooling may not have general validity (Villa, 2006). Here we propose a new detrital geochronology model that takes into account the effects of both crystallization and exhumational cooling on geochronometers, from U-Pb on zircon to fission tracks on apatite. This model, specifically designed for unroofing magmatic complexes, predicts both stationary and moving mineral-age peaks. Because its base is the ordinary interaction between endogenic and exogenic processes, it is applicable to any geological setting. It was tested on the extremely well-studied Bregaglia-Bergell pluton in the Alps, and on the sedimentary succession derived from its erosion. The consistency between predicted and observed age patterns validates the model. Our results demonstrate that volcanoes were active on top of the growing Oligocene Alps, and resolve a long-standing paradox in quantitative erosion-sedimentation modelling, the scarcity of sediment during apparently fast erosion. Dickinson, W. R. & Suczek, C. A. Plate tectonics and sandstone composition. Am. Assoc. Petrol. Geol. Bull. 63, 2164-2172 (1979). Garzanti, E., Doglioni, C., Vezzoli. G. & Andò, S. Orogenic belts and orogenic sediment provenance. J. Geol. 115, 315-334 (2007). Brandon, M. T., Roden-Tice, M. K. & Garver, J. I. Cenozoic exhumation of the Cascadia accretionary wedge in the Olympic Mountains, northwest Washington State. Geol. Soc. Am. Bull

  1. Definition of petroleum generating time for Lower Cambrian bitumen of the Kuangshanliang in the west Sichuan Basin,China:Evidence from Re-Os isotopic isochron age%川西矿山梁下寒武统沥青脉油气生成时间的厘定--来自于固体沥青Re-Os同位素等时线年龄的证据

    Institute of Scientific and Technical Information of China (English)

    王杰; 腾格尔; 刘文汇; 马亮帮; 陶成; 周圆圆; 王萍; 李超


    Bitumen veins an d oil seepages,especially Lower Cambrian bitumen veins,were widely distributed in the north part of Longmenshan Mountain in western Sichuan Basin,which indicates that the prospect for Sinian and Cambrian oil reservoir is fine in the area.Although some progress has been made in the origin of bitumen veins in Lower Cambrian,there are still big differences in the source rocks.At the same time,pe-troleum producing time of bitumen vein is lack of systematically researches.Rhenium(Re)-Osmium(Os)i-sotopic chronology is a new method to apply for geochronology of hydrocarbon accumulation,and can di-rectly date the age of source rock,oil,oil sand and bitumen.The pre-treatment means and experimental in-strument on extraction and dissolution of asphaltenes,purification,enrichment and separation of Re and Os were established by a series conditional tests.Re-Os isotopic chronology consists of sample preparation,dis-solution,Re and Os purification and chemical separation,Re and Os isotope mass spectrometry measure-ments,and data treatment of by Isoplot software.The research for Re-Os isotopic isochron age and source rock of bitumen indicates that the asphalt maturity is low,the generating time of predecessor hydrocarbon is between 572Ma and 559Ma of Late Sinian in Neoproterozoic era,and it came from the very old source rocks in the Lower Cambrian in the Kuangshanliang structure.By means of Re-Os isochron ages,initial 187 Os/188 Os ratios,carbon isotope compositions and biomarkers,the Lower Cambrian bitumen in Guan-gyuan area is originated from the fine source rocks of the Doushantuo Formation in Sinian,and the hydro-carbon source rocks were of low maturity and generated a certain amount of thick oil from 572Ma to 559Ma.Subsequently,thick oil entered the Dengying layer and formed paleo-oil reservoir.Because of the late.%川西龙门山北段沥青脉与油苗广泛分布,尤其是下寒武统沥青脉,说明在龙门山褶皱带北段东缘具有寻找震旦

  2. Pyrite sulfur isotopes reveal glacial-interglacial environmental changes (United States)

    Pasquier, Virgil; Sansjofre, Pierre; Rabineau, Marina; Revillon, Sidonie; Houghton, Jennifer; Fike, David A.


    The sulfur biogeochemical cycle plays a key role in regulating Earth’s surface redox through diverse abiotic and biological reactions that have distinctive stable isotopic fractionations. As such, variations in the sulfur isotopic composition (δ34S) of sedimentary sulfate and sulfide phases over Earth history can be used to infer substantive changes to the Earth’s surface environment, including the rise of atmospheric oxygen. Such inferences assume that individual δ34S records reflect temporal changes in the global sulfur cycle; this assumption may be well grounded for sulfate-bearing minerals but is less well established for pyrite-based records. Here, we investigate alternative controls on the sedimentary sulfur isotopic composition of marine pyrite by examining a 300-m drill core of Mediterranean sediments deposited over the past 500,000 y and spanning the last five glacial-interglacial periods. Because this interval is far shorter than the residence time of marine sulfate, any change in the sulfur isotopic record preserved in pyrite (δ34Spyr) necessarily corresponds to local environmental changes. The stratigraphic variations (>76‰) in the isotopic data reported here are among the largest ever observed in pyrite, and are in phase with glacial-interglacial sea level and temperature changes. In this case, the dominant control appears to be glacial-interglacial variations in sedimentation rates. These results suggest that there exist important but previously overlooked depositional controls on sedimentary sulfur isotope records, especially associated with intervals of substantial sea level change. This work provides an important perspective on the origin of variability in such records and suggests meaningful paleoenvironmental information can be derived from pyrite δ34S records.

  3. Bio-leaching effects of Leptospirillum ferriphilum on the surface chemical properties of pyrite

    Institute of Scientific and Technical Information of China (English)


    Leptospirillum ferriphilum cultured using different energy sources(either soluble ferrous ion or pyrite) changed the surface properties of pyrite.Cell adsorption,zeta-potential,hydrophobicty,FT-IR spectra and surface morphology were investigated.Adhesion of bacterial cells to the pyrite surface is a fast process.Furthermore,the adsorption of cells grown in pyrite is greater than of cells grown in soluble ferrous ion.The Iso-Electric Point(IEP) of pyrite treated with L.ferriphilum approaches that of the cell...

  4. New constraints on the Paleoarchean meteorite bombardment of the Earth - Geochemistry and Re-Os isotope signatures of spherule layers in the BARB5 ICDP drill core from the Barberton Greenstone Belt, South Africa (United States)

    Schulz, Toni; Koeberl, Christian; Luguet, Ambre; van Acken, David; Mohr-Westheide, Tanja; Ozdemir, Seda; Reimold, Wolf Uwe


    Archean spherule layers, resulting from impacts by large extraterrestrial objects, to date represent the only remnants of the early meteorite, asteroid, and comet bombardment of the Earth. Only few Archean impact debris layers have been documented, all of them embedded in the 3.23-3.47 billion year old successions of the Barberton Greenstone Belt (BGB) in South Africa and the Pilbara Craton in Western Australia. Some of them might be correlated with each other. Given the scarcity of Archean spherule deposits, four spherule layer intersections from the recently recovered BARB5 drill core from the central Barberton Greenstone Belt, analyzed in this study, provide an opportunity to gain new insight into the early terrestrial impact bombardment. Despite being hydrothermally overprinted, siderophile element abundance signatures of spherule-rich samples from the BARB5 drill core, at least in part, retained a meteoritic fingerprint. The impact hypothesis for the generation of the BARB5 spherule layers is supported by correlations between the abundances of moderately (Cr, Co, Ni) and highly siderophile (Re, Os, Ir, Pt, Ru and Pd) elements, whose peak concentrations and interelement ratios are within the range of those for chondrites. Rhenium-Osmium isotope evidence further support the impact hypothesis. Collectively, this study provides evidence for extraterrestrial admixtures ranging between ∼40 and up to 100% to three of the four analyzed BARB5 spherule layers, and a scenario for their genesis involving (i) impact of a chondritic bolide into a sedimentary target, (ii) varying admixtures of meteoritic components to target materials, (iii) spherule formation via condensation in an impact vapor plume, (iv) transportation of the spherules and sedimentation under submarine conditions, followed by (v) moderate post-impact remobilization of transition metals and highly siderophile elements.

  5. 沥青样品铼-锇同位素分析溶解实验研究%Dissolving Experimental Research of Re-Os Isotope System for Bitumen Samples

    Institute of Scientific and Technical Information of China (English)

    李超; 屈文俊; 王登红; 陈郑辉; 杜安道; 张长青


    The content of Re-Os in asphalt samples is relatively low, and CO2 are released in digestion because of large amounts of organic matter. It is important to control the amount of asphalt in the sample and the proportion of oxidant to ensure the Os recovery and stability of the measured signal. The method for the Re-Os isotope was improved because of large amounts of organic matter contained in bitumen samples. The Oxidants was changed to 3 mL HC1, 4 mL HNO3 and 3mL H2 O2 from the original 3 mL HC1 and 6 mL HNO3, the improved method making the Os measured signal approximately 2 times larger than before. Changes in oxidants composition increase the amount of the bitumen sample weight greatly from th eoriginal 0.2 g to 0. 4 g. Influence of H2 O2 added with routine reverse aqua regia and direct distillation from a Carius tube on the signal intensity of osmium measured by Inductively Coupled Plasma-MassSpectrometry( ICP-MS ). Was studied. Bitumen samples were dissolved and equilibrated with a known amount of 185Re and 190Os tracers in 2 mL HC1, 5 mL HNO3 and 2 mL H2O2 by a Carius tube at 200℃ for 12 h and 240℃ for 12 h, with the Os and Re separated using direct distillation or routine distillation and solvent extraction techniques, respectively. 187Re/185 Re, 187Os/190Os and 192Os/190Os were determined by ICP-MS. Bitumen samples in lead-zinc deposits from Yunnan Province were analyzed. The isochron ages was (60 ± 2 ) Ma ( MSWD = 2. 5, n = 7 ), and the initial 187Os/188Os values was 4. 36 ±0. 14. The results show that Re-Os isotope is an effective tool to date bitumen samples and the Os in the bitumen originated from the crust. The established method can be used to date and trace the source of bitumen samples.%沥青样品中Re、Os含量较低,且组成复杂,因含有大量有机质,在溶样过程中会释放大量CO2,需要大量氧化剂.控制样品称样量和氧化剂比例、用量对保证Os的回收率以及测量信号的稳定性非常重要.本文根

  6. Surface electrochemical control for fine coal and pyrite separation. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Wadsworth, M.E.; Bodily, D.M.; Hu, Weibai; Chen, Wanxiong; Huang, Qinping; Liang, Jun; Riley, A.M.; Li, Jun; Wann, Jyi-Perng; Zhong, Tingke; Zhu, Ximeng


    Laboratory flotation tests were carried out on three coals and on coal pyrite. Floatability measurements included natural floatability, flotation with a xanthate collector and salt flotation. The ranking of the floatability of the three coals were: Upper Freeport > Pittsburgh > Illinois. The floatability of mineral pyrite and coal pyrite increased markedly with xanthate concentration, but decreased with increased pH. In general, coal pyrite was more difficult to float than mineral pyrite. This was attributed to the presence of surface carbonaceous and mineral matter, since floatability of coal pyrite improved by acid pretreatment. Flotation tests demonstrated that the floatability of coal and mineral pyrite was greatly enhanced by the presence of an electrolyte. Flotation was also enhanced by the addition of modifiers such as CuSO{sub 4}, Na{sub 2}S, CO{sub 2} and EDTA. Lime additions markedly reduced the floatability of coal pyrite. Enhanced floatability of coal pyrite resulted when the pyrite was anodically oxidized in a specially constructed electrochemical flotation cell Pretreatment in potential ranges previously observed for polysulfide and sulfur film formation resulted in the enhanced floatability. While interesting trends and influences, both chemical and electrochemical, markedly improved the floatability of coal, there is little hope for reverse flotation as an effective technology for coal/coal-pyrite separations. The effects of poor liberation and entrainment appear overriding.

  7. Trace metal pyritization variability in response to mangrove soil aerobic and anaerobic oxidation processes. (United States)

    Machado, W; Borrelli, N L; Ferreira, T O; Marques, A G B; Osterrieth, M; Guizan, C


    The degree of iron pyritization (DOP) and degree of trace metal pyritization (DTMP) were evaluated in mangrove soil profiles from an estuarine area located in Rio de Janeiro (SE Brazil). The soil pH was negatively correlated with redox potential (Eh) and positively correlated with DOP and DTMP of some elements (Mn, Cu and Pb), suggesting that pyrite oxidation generated acidity and can affect the importance of pyrite as a trace metal-binding phase, mainly in response to spatial variability in tidal flooding. Besides these aerobic oxidation effects, results from a sequential extraction analyses of reactive phases evidenced that Mn oxidized phase consumption in reaction with pyrite can be also important to determine the pyritization of trace elements. Cumulative effects of these aerobic and anaerobic oxidation processes were evidenced as factors affecting the capacity of mangrove soils to act as a sink for trace metals through pyritization processes.

  8. Comparative Mössbauer study of the oxidation of pyrite under different conditions (United States)

    Gracia, M.; Gancedo, J. R.; Martínez-Alonso, A.; Tascón, J. M. D.


    Samples of pyrite-rich brown coal from As Pontes and Meirama coalfields (Spain) were oxidized either by air at atmospheric pressure or by a cool oxygen plasma generated by radiofrequency activation. Despite the very different nature and characteristics of the oxidizing media, in both cases the RT Mössbauer spectra were easily fitted to two doublets, whose parameters matched those of pyrite and jarosite (hydrated iron (III) sulphate). The extent of pyrite oxidation to jarosite was monitored by the relative spectral areas of pyrite and jarosite doublets. Both, air and plasma, oxidized pyrite to the same extent and in a similar way, in contrast to coal organic matter, which was scarcely modified by air but completely oxidized by the plasma at the same temperature (ca. 423 K). The incomplete oxidation of pyrite by plasma is attributed to the action of a thin calcium sulphate layer which hinders the access of activated oxygen to small pyrite crystals.

  9. Comparative Moessbauer study of the oxidation of pyrite under different conditions

    Energy Technology Data Exchange (ETDEWEB)

    Gracia, M.; Gancedo, J.R.; Martinez-Alonso, A.; Tascon, J.M.D. (Instituto de Quimica Fisica ' Rocasolano' , Madrid (Spain))


    Samples of pyrite-rich brown coal from As Pontes and Meirama coalfields (Spain) were oxidized either by air at atmospheric pressure or by a cool oxygen plasma generated by radiofrequency activation. Despite the very different nature and characteristics of the oxidizing media, in both cases the RT Moessbauer spectra were easily fitted to two doublets, whose parameters matched those of pyrite and jarosite (hydrated iron (III) sulphate). The extent of pyrite oxidation to jarosite was monitored by the relative spectral areas of pyrite and jarosite doublets. Both, air and plasma, oxidized pyrite to the same extent and in a similar way, in contrast to coal organic matter, which was scarcely modified by air but completely oxidized by the plasma at the same temperature (ca. 423 K). The incomplete oxidation of pyrite by plasma is attributed to the action of a thin calcium sulphate layer which hinders the access of activated oxygen to small pyrite crystals. 18 refs., 3 tabs., 2 figs.

  10. Isotope Geochronology: Technique and Application%同位素地质年龄测定技术及应用

    Institute of Scientific and Technical Information of China (English)

    陈文; 万渝生; 李华芹; 张宗清; 戴檀谟; 施泽恩; 孙敬博


    了困扰,有时不能给出正确可信的年龄.⑤Re-Os法:是目前能够直接测定金属矿床矿化年龄的唯一成熟方法.但在实验技术和应用方面还存在不少问题:a.近年来发现有些金属矿床辉钼矿的Re-Os年龄高于其赋矿围岩的年龄,原因不明;b.黄铁矿等多数硫化物矿物含Re量很低,并含有一定程度的普通Os,对样品化学制备过程中低本底的要求很高,一般实验室难以达到,普通Os也难以准确扣除;c.后期的热液活动有时可以使Os同位素发生重置,因此,金属硫化物Re-Os同位素体系封闭温度及其影响因素是一个亟待解决的问题.⑥(U-Th)/He法:(U-Th)/He同位素系统的优势是其封闭温度是已有同位素体系中最低的,能够记录地质体经历较低温度范围的时代与温度信息.该方法在矿床年代学研究中也具有可观应用前景.其不足之处是因为封闭温度很低,在用于地质体定年时要特别关注冷却速率和再加热作用的影响.%Isotope geochronology is a newly developed interdisciplinary science which combines geoscience, physics, chemistry and technical sciences, and is a young and energetic branch of earth science. The decay of radioactive isotopes is used to determine the formation age of geological body and the age of geological events, with aiming to study the formation history and evolution of earth and planetary materials. This paper presents brief introduction and summary of relative high-precise isotope dating methods in terms of theory, experiment techniques, application scope, precautions for use, in hope of providing a useful reference to geologist. Main isotope dating methods involved s are U-Pb, Ar-Ar, Rb-Sr, Sm-Nd, Re-Os and (U-Th)/He methods. (l)U-Pb method: It is one of the earliest radioactive methods for determination of geological age as well as the most important isotope dating method in China so far. In the past 10 years, the introduction of zircon U-Pb dating technique

  11. Source of arsenic-bearing pyrite in southwestern Vermont, USA: Sulfur isotope evidence

    Energy Technology Data Exchange (ETDEWEB)

    Mango, Helen, E-mail: [Department of Natural Sciences, Castleton State College, 233 South Street, Castleton, VT 05735 (United States); Ryan, Peter, E-mail: [Department of Geology, Middlebury College, 276 Bicentennial Way, Middlebury, VT 05753 (United States)


    Arsenic-bearing pyrite is the source of arsenic in groundwater produced in late Cambrian and Ordovician gray and black slates and phyllites in the Taconic region of southwestern Vermont, USA. The aim of this study is to analyze the sulfur isotopic composition of this pyrite and determine if a relationship exists between pyrite δ{sup 34}S and arsenic content. Pyrite occurs in both sedimentary/diagenetic (bedding-parallel layers and framboids) and low-grade metamorphic (porphyroblast) forms, and contains up to > 2000 ppm As. The sulfur isotopic composition of arsenic-bearing pyrite ranges from − 5.2‰ to 63‰. In the marine environment, the sulfur in sedimentary pyrite becomes increasingly enriched in {sup 34}S as the geochemical environment becomes increasingly anoxic. There is a positive correlation between δ{sup 34}S and arsenic content in the Taconic pyrite, suggesting that uptake of arsenic by pyrite increased as the environment became more reducing. This increased anoxia may have been due to a rise in sea level and/or tectonic activity during the late Cambrian and Ordovician. Low-grade metamorphism appears to have little effect on sulfur isotope composition, but does correlate with lower arsenic content in pyrite. New groundwater wells drilled in this region should therefore avoid gray and black slates and phyllites that contain sedimentary/diagenetic pyrite with heavy δ{sup 34}S values. - Highlights: • Pyrite is the source of arsenic in groundwater in the Taconic region of Vermont, USA. • As-bearing pyrite δ{sup 34}S = – 5.2 to 63‰ with higher {sup 34}S as environment becomes more anoxic. • High sea level, tectonic activity create anoxia, with incorporation of As into pyrite. • New wells should avoid slate/phyllite containing sedimentary pyrite with heavy δ{sup 34}S.

  12. A proposed new type of arsenian pyrite: Composition, nanostructure and geological significance (United States)

    Deditius, Artur P.; Utsunomiya, Satoshi; Renock, Devon; Ewing, Rodney C.; Ramana, Chintalapalle V.; Becker, Udo; Kesler, Stephen E.


    This report describes a new form of arsenian pyrite, called As3+-pyrite, in which As substitutes for Fe [(Fe,As)S2], in contrast to the more common form of arsenian pyrite, As1--pyrite, in which As1- substitutes for S [Fe(As,S)2]. As3+-pyrite has been observed as colloformic overgrowths on As-free pyrite in a hydrothermal gold deposit at Yanacocha, Peru. XPS analyses of the As3+-pyrite confirm that As is present largely as As3+. EMPA analyses show that As3+-pyrite incorporates up to 3.05 at % of As and 0.53 at. %, 0.1 at. %, 0.27 at. %, 0.22 at. %, 0.08 at. % and 0.04 at. % of Pb, Au, Cu, Zn, Ni, and Co, respectively. Incorporation of As3+ in the pyrite could be written like: As+yAu+1-y(□)⇔2Fe; where Au+ and vacancy (□) help to maintain the excess charge. HRTEM observations reveal a sharp boundary between As-free pyrite and the first overgrowth of As3+-pyrite (20-40 nm thick) and co-linear lattice fringes indicating epitaxial growth of As3+-pyrite on As-free pyrite. Overgrowths of As3+-pyrite onto As-free pyrite can be divided into three groups on the basis of crystal size, 8-20 nm, 100-300 nm and 400-900 nm, and the smaller the crystal size the higher the concentration of toxic arsenic and trace metals. The Yanacocha deposit, in which As3+-pyrite was found, formed under relatively oxidizing conditions in which the dominant form of dissolved As in the stability field of pyrite is As3+; in contrast, reducing conditions are typical of most environments that host As1--pyrite. As3+-pyrite will likely be found in other oxidizing hydrothermal and diagenetic environments, including high-sulfidation epithermal deposits and shallow groundwater systems, where probably kinetically controlled formation of nanoscale crystals such as observed here would be a major control on incorporation and release of As3+ and toxic heavy metals in oxidizing natural systems.

  13. EARTHTIME: Teaching geochronology to high school students (United States)

    Bookhagen, Britta; Buchwaldt, Robert; McLean, Noah; Rioux, Matthew; Bowring, Samuel


    The authors taught an educational module developed as part of the EARTHTIME ( outreach initiative to 215 high school students from a Massachusetts (USA) High School as part of an "out-of-school" field trip. The workshop focuses on uranium-lead (U-Pb) dating of zircons and its application to solving a geological problem. The theme of our 2.5-hour module is the timing of the K-T boundary and a discussion of how geochronology can be used to evaluate the two main hypotheses for the cause of the concurrent extinction—the Chicxlub impact and the massive eruption of the Deccan Traps. Activities are divided into three parts: In the first part, the instructors lead hands-on activities demonstrating how rock samples are processed to isolate minerals by their physical properties. Students use different techniques, such as magnetic separation, density separation using non-toxic heavy liquids, and mineral identification with a microscope. We cover all the steps from sampling an outcrop to determining a final age. Students also discuss geologic features relevant to the K-T boundary problem and get the chance to examine basalts, impact melts and meteorites. In the second part, we use a curriculum developed for and available on the EARTHTIME website ( The curriculum teaches the science behind uranium-lead dating using tables, graphs, and a geochronology kit. In this module, the students start by exploring the concepts of half-life and exponential decay and graphically solving the isotopic decay equation. Manipulating groups of double-sided chips labeled with U and Pb isotopes reinforces the concept that an age determination depends on the Pb/U ratio, not the absolute number of atoms present. Next, the technique's accuracy despite loss of parent and daughter atoms during analysis, as well as the use of isotopic ratios rather than absolute abundances, is explained with an activity on isotope dilution. Here the students

  14. Pyrite surface characterization and control for advanced fine coal desulfurization technologies. First annual report, September 1, 1990--August 30, 1991

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiang-Huai


    The objective of this project is to conduct extensive studies on the surface reactivity of pyrite by using electrochemical, surface analysis, potentiometric and calorimetric titration, and surface hydrophobicity characterization techniques and to correlate the alteration of the coal-pyrite surface with the efficiency of pyrite rejection in coal flotation. The products as well as their structure, the mechanisms and the kinetics of the oxidation of coal-pyrite surfaces and their interaction with various chemical reagents will be systematically studied and compared with that of mineral-pyrite and synthetic pyrite to determine the correlation between the surface reactivity of pyrite and the bulk chemical properties of pyrite and impurities. The surface chemical studies and the studies of floatability of coal-pyrite and the effect of various parameters such as grinding media and environment, aging under different atmospheres, etc. on thereof, are directed at identifying the causes and possible solutions of the pyrite rejection problems in coal cleaning.

  15. Protein footprinting by pyrite shrink-wrap laminate. (United States)

    Leser, Micheal; Pegan, Jonathan; El Makkaoui, Mohammed; Schlatterer, Joerg C; Khine, Michelle; Law, Matt; Brenowitz, Michael


    The structure of macromolecules and their complexes dictate their biological function. In "footprinting", the solvent accessibility of the residues that constitute proteins, DNA and RNA can be determined from their reactivity to an exogenous reagent such as the hydroxyl radical (·OH). While ·OH generation for protein footprinting is achieved by radiolysis, photolysis and electrochemistry, we present a simpler solution. A thin film of pyrite (cubic FeS2) nanocrystals deposited onto a shape memory polymer (commodity shrink-wrap film) generates sufficient ·OH via Fenton chemistry for oxidative footprinting analysis of proteins. We demonstrate that varying either time or H2O2 concentration yields the required ·OH dose-oxidation response relationship. A simple and scalable sample handling protocol is enabled by thermoforming the "pyrite shrink-wrap laminate" into a standard microtiter plate format. The low cost and malleability of the laminate facilitates its integration into high throughput screening and microfluidic devices.

  16. Building Interactive Visualizations for Geochronological Data (United States)

    Zeringue, J.; Bowring, J. F.; McLean, N. M.; Pastor, F.


    Since the early 1990s, Ken Ludwig's Isoplot software has been the tool of choice for visualization and analysis of isotopic data used for geochronology. The software is an add-in to Microsoft Excel that allows users to generate visual representations of data. However, recent changes to Excel have made Isoplot more difficult to use and maintain, and the software is no longer supported. In the last several years, the Cyber Infrastructure Research and Development Lab for the Earth Sciences (CIRDLES), at the College of Charleston, has worked collaboratively with geochronologists to develop U-Pb_Redux, a software product that provides some of Isoplot's functionality for U-Pb geochronology. However, the community needs a full and complete Isoplot replacement that is open source, platform independent, and not dependent on proprietary software. This temporary lapse in tooling also presents a tremendous opportunity for scientific computing in the earth sciences. When Isoplot was written for Excel, it gained much of the platform's flexibility and power but also was burdened with its limitations. For example, Isoplot could not be used outside of Excel, could not be cross-platform (so long as Excel wasn't), could not be embedded in other applications, and only static images could be produced. Nonetheless this software was and still is a powerful tool that has served the community for more than two decades and the trade-offs were more than acceptable. In 2014, we seek to gain flexibility not available with Excel. We propose that the next generation of charting software be reusable, platform-agnostic, and interactive. This new software should allow scientists to easily explore—not just passively view—their data. Beginning in the fall of 2013, researchers at CIRDLES began planning for and prototyping a 21st-century replacement for Isoplot, which we call Topsoil, an anagram of Isoplot. This work is being conducted in the public domain at We

  17. Statistics of large detrital geochronology datasets (United States)

    Saylor, J. E.; Sundell, K. E., II


    Implementation of quantitative metrics for inter-sample comparison of detrital geochronological data sets has lagged the increase in data set size, and ability to identify sub-populations and quantify their relative proportions. Visual comparison or application of some statistical approaches, particularly the Kolmogorov-Smirnov (KS) test, that initially appeared to provide a simple way of comparing detrital data sets, may be inadequate to quantify their similarity. We evaluate several proposed metrics by applying them to four large synthetic datasets drawn randomly from a parent dataset, as well as a recently published large empirical dataset consisting of four separate (n = ~1000 each) analyses of the same rock sample. Visual inspection of the cumulative probability density functions (CDF) and relative probability density functions (PDF) confirms an increasingly close correlation between data sets as the number of analyses increases. However, as data set size increases the KS test yields lower mean p-values implying greater confidence that the samples were not drawn from the same parent population and high standard deviations despite minor decreases in the mean difference between sample CDFs. We attribute this to the increasing sensitivity of the KS test when applied to larger data sets, which in turn limits its use for quantitative inter-sample comparison in detrital geochronology. Proposed alternative metrics, including Similarity, Likeness (complement to Mismatch), and the coefficient of determination (R2) of a cross-plot of PDF quantiles, point to an increasingly close correlation between data sets with increasing size, although they are the most sensitive at different ranges of data set sizes. The Similarity test is most sensitive to variation in data sets with n < 100 and is relatively insensitive to further convergence between larger data sets. The Likeness test reaches 90% of its asymptotic maximum at data set sizes of n = 200. The PDF cross-plot R2 value

  18. Heterocoagulation of chalcopyrite and pyrite minerals in flotation separation. (United States)

    Mitchell, Timothy K; Nguyen, Anh V; Evans, Geoffrey M


    Heterocoagulation between various fine mineral particles contained within a mineral suspension with different structural and surface chemistry can interfere with the ability of the flotation processes to selectively separate the minerals involved. This paper examines the interactions between chalcopyrite (a copper mineral) and pyrite (an iron mineral often bearing gold) as they approach each other in suspensions with added chemicals, and relates the results to the experimental data for the flotation recovery and selectivity. The heterocoagulation was experimentally studied using the electrophoretic light scattering (ELS) technique and was modelled by incorporating colloidal forces, including the van der Waals, electrostatic double layer and hydrophobic forces. The ELS results indicated that pyrite has a positive zeta potential (zeta) up to its isoelectric point (IEP) at approximately pH 2.2, while chalcopyrite has a positive zeta up to its IEP at approximately pH 5.5. This produces heterocoagulation of chalcopyrite with pyrite between pH 2.2 and pH 5.5. The heterocoagulation was confirmed by the ELS spectra measured with a ZetaPlus instrument from Brookhaven and by small-scale flotation experiments.

  19. Effect of processing history of pyrite on its leaching kinetics

    Institute of Scientific and Technical Information of China (English)

    赵中伟; 李洪桂; 孙培梅; 李运姣; 霍广生


    Different researchers often attained scattered kinetic results for the same leaching process. Usually, the difference is ascribed to the variation in mineral resource, chemical composition and, accuracy of experimental methods, while less attention is paid to the sample processing history. The present study shows that processing history of pyrite sample can cause great changes in its physico-chemical properties. Crushing, grinding and milling lead to an increase of the leachability of pyrite and the leaching becomes less temperature dependence owing to the decreasing of apparent activation energy of the reaction. The activation energy for its leaching in H2SO4-HNO3 solution is depressed from 73.9 to 47.5kJ/mol after being activated through vibrating milling for 40min. On the contrary, aging causes the reverse change owing to the release of extra inner energy stored during mechanical treatments. Thus activity of pyrite will decrease towards its original value. Surely the processing history of concentrate sample should be taken into consideration when studying the kinetics of leaching reaction.

  20. Source of arsenic-bearing pyrite in southwestern Vermont, USA: sulfur isotope evidence. (United States)

    Mango, Helen; Ryan, Peter


    Arsenic-bearing pyrite is the source of arsenic in groundwater produced in late Cambrian and Ordovician gray and black slates and phyllites in the Taconic region of southwestern Vermont, USA. The aim of this study is to analyze the sulfur isotopic composition of this pyrite and determine if a relationship exists between pyrite δ(34)S and arsenic content. Pyrite occurs in both sedimentary/diagenetic (bedding-parallel layers and framboids) and low-grade metamorphic (porphyroblast) forms, and contains up to >2000 ppm As. The sulfur isotopic composition of arsenic-bearing pyrite ranges from -5.2‰ to 63‰. In the marine environment, the sulfur in sedimentary pyrite becomes increasingly enriched in (34)S as the geochemical environment becomes increasingly anoxic. There is a positive correlation between δ(34)S and arsenic content in the Taconic pyrite, suggesting that uptake of arsenic by pyrite increased as the environment became more reducing. This increased anoxia may have been due to a rise in sea level and/or tectonic activity during the late Cambrian and Ordovician. Low-grade metamorphism appears to have little effect on sulfur isotope composition, but does correlate with lower arsenic content in pyrite. New groundwater wells drilled in this region should therefore avoid gray and black slates and phyllites that contain sedimentary/diagenetic pyrite with heavy δ(34)S values.


    Institute of Scientific and Technical Information of China (English)

    吴自成; 刘继顺; 张彩华; 舒国文; 王伟


    菲莫铜钼多金属矿床是哀牢山造山带内较典型的铜钼多金属矿床,研究采用电感耦合等离子体质谱仪法对菲莫铜钼多金属矿床辉钼矿的Re-Os同位素精确测年,获得辉钼矿Re-Os同位素模式年龄为47.81 Ma±0.71 Ma;而哀牢山铜多金属成矿带镇沅、墨江、大坪大型金矿的成矿时间均与之相当,约50 Ma±.这暗示了喜马拉雅期由于印度板块向北碰撞,造成古特提斯洋消失,碰撞造山过程导致上地幔及下地壳等深部物质部分熔融,红河、哀牢山走滑挤压引起的热流值上升造成了深熔作用导致地壳深部物质进一步熔融,造成了哀牢山带大规模的构造-岩浆热事件,从而为形成诸多铜、金及多金属矿床提供了大量的成矿物质和动力、热流条件.%ICP-MS method is used to study the Re-Os isotopes for molybdenite samples of Feimo Cu-Mo polymetallic deposit. It is revealed that the ore-forming age is 47. 81 + 0. 71Ma on average, similar to the gold deposit mineralization time (50 Mai) of Zhenyuan, Mojiang and Daping in Ailaoshan area. It indicates that northward subduction of Indian Plate under the Euro-Asia Plate in Himalayan resulted in the closet of Paleo-Tethys ocean,and during the collision orogeny,the deep material in upper mantle and lower crust are partly melting. Large-scale tectonic and mag-matic activities occurred in Ailaoshan belt duo to the strike-slip and compression and brought a-bout the melting of material of deep crust and the uplift of thermal flow, which provided driving force,hydrothermal fluid and a lot of ore-forming materials,forming plenty of polymetallic ore deposits.

  2. Combined Whole-Rock to Nano-Scale Investigations Reveal Contrasting Response of Pt-Os and Re-Os Isotope Systematics During Magmatic and Post-Magmatic Processes (United States)

    Coggon, J. A.; Luguet, A.; Lorand, J. P.; Fonseca, R.; Wainwright, A.; Appel, P.; Hoffmann, J. E.; Nowell, G. M.


    Advances in single-grain and micro- and nano-analytical techniques in recent years have been particularly important to the study of highly siderophile elements (HSE) and have contributed significantly to our knowledge and understanding of their host phases and behaviour. Furthermore, whole-rock- to nano-scale studies provide new perspectives for investigation of HSE isotope systematics. Recent multi-scale 187Re-187Os and 190Pt-186Os studies facilitate comparison, to a previously unattainable degree, of the differing responses of these two decay systems to magmatic and post-magmatic processes. It is well established that mafic-ultramafic melts are sensitive to disturbance of their Re-Os isotope systematics by crustal assimilation, due to the incompatibility and resulting enrichment of Re in crustal lithologies. In contrast the very long half-life and extremely low atomic abundance of 190Pt, combined with relatively low Pt concentrations in crustal rocks, generally render the Pt-Os isotope system insensitive to modification during assimilation. However, using new single chromite grain data (Coggon et al., 2015) from the >3.811 Ga Ujaragssuit nunât layered ultramafic body, Greenland, we show that it is possible to distinguish two distinct episodes of 187Os/188Os modification; Country rock contamination of the parent melt was followed by later metamorphic disturbance of the isotope system. The Pt-Os data (Coggon et al., 2013) from the same samples show no evidence of crustal assimilation, but preserve signatures of mantle melting at ~4.1 Ga as well as disturbance during metamorphism. Macro- to micro-petrographic study clearly demonstrates that Pt, Re and Os are hosted by different mineral phases, of different origins, in these samples. This, together with the physical parameters of the decay systems reported above, leads to the dissimilar behaviour and response of the 187Re-187Os and 190Pt-186Os isotope systems during both magmatic and post-magmatic processes and

  3. Interfacial electrokinetic characteristics before and after bioleaching microorganism adhesion to pyrite

    Institute of Scientific and Technical Information of China (English)

    LIU Jian-she; WANG Zhao-hui; CHEN Hong; ZHANG Yan-hua


    Zeta potentials of pyrite and Acidithiobacillusferrooxidans cultured by sulfur in different levels of ionic strength and pH values were measured by Coulter Delsa 440SX zeta potential determinator. Meanwhile, the effects of bacterial adhesion and bacterial concentration on zeta potential of pyrite after adsorption were investigated. The results show that with the increase of ionic strength,zeta potentials of pyrite decrease in the range of pH 2.5-10.5 and the isoelectric point(IEP) of mineral shifts to the left. It is also found that the specific adsorption on pyrite of chloride ion can affect zeta potentials of pyrite sharply. As bacterial adsorption occurs,IEP of pyrite shifts towards that of Acidithiobacillus ferrooxidans; as bacterial concentration is increscent, this tendency is even larger and more obvious. Finally, a reasonable explanation for above-mentioned experimental phenomena was given by electrical double layer model and surface ionization model.

  4. Speciation of arsenic in pyrite by micro-X-ray absorption fine- structure spectroscopy (XAFS)

    Energy Technology Data Exchange (ETDEWEB)

    Paktunc, D. (CCM)


    Pyrite (FeS2) often contains variable levels of arsenic, regardless of the environment of formation. Arsenian pyrite has been reported in coals, sediments and ore deposits. Arsenian pyrite having As concentrations of up to 10 wt % in sedimentary rocks (Kolker et al. 1997), about 10 wt% in gold deposits (Fleet et al. 1993), 12 wt % in a refractory gold ore (Paktunc et al. 2006) and 20 wt % in a Carlin-type gold deposit in Nevada (Reich et al. 2005) have been reported. Arsenian pyrite is the carrier of gold in hydrothermal Carlin-type gold deposits, and gold concentrations of up to 0.9 wt % have been reported (Reich et al. 2005; Paktunc et al. 2006). In general, high Au concentrations correlate with As-rich zones in pyrite (Paktunc et al. 2006). Pyrite often ends up in mining and metallurgical wastes as an unwanted mineral and consititutes one of the primary sources of As in the wastes. Arsenic can be readily released to the environment due to rapid oxidative dissolution of host pyrite under atmospheric conditions. Pyrite is also the primary source of arsenic in emissions and dust resulting from combustion of bituminous coals. Despite the importance of arsenian pyrite as a primary source of anthropogenic arsenic in the environment and its economic significance as the primary carrier of gold in Carlin-type gold deposits, our understanding of the nature of arsenic in pyrite is limited. There are few papers dealing with the mode of occurrence of arsenic by bulk XAFS in a limited number of pyrite-bearing samples. The present study documents the analysis of pyrite particles displaying different morphologies and a range of arsenic and gold concentrations to determine the nature and speciation of arsenic.

  5. Pyritization of the Coastal Sediments in the Kelantan Plains in the Malay Peninsula during the Holocene

    Directory of Open Access Journals (Sweden)

    M. S.K. Enio


    Full Text Available Problem statement: For a number of geological reasons a proportion of the present coastal plains in the Malay Peninsula were inundated by seawater in the past when pyrite in some of the soils is believed to have been mineralized. Random survey of these sites showed a unique distribution and depth of pyritic layer in the soils along the coastal plains. A study was conducted in order to explain the mechanism of pyritization in the sediments of the present day coastal plains in Kelantan, Peninsular Malaysia. Approach: Soil surveys were conducted and soils were sampled and analyzed. Spatial distribution of the pyritic soils was used to construct an imaginary line to indicate the probable position of the shoreline when the sea level was at its highest. Results: Results of the study showed that soils containing pyrite occur sporadically in the plains. This pyrite occurs in the soils at varying depth; some soils have pyritic layer below 2 m from the surface (northern region, while others have pyrite in the surface horizon (southern region. Pyrite was formed by the reaction of ferrous and sulfide ions which were respectively reduced from ferric ions (sediments and sulfate (seawater ions, respectively. In the middle of the study area, pyritic layer overlain by peaty materials were observed. Conclusion: The presence of pyrite in the soils can be used as an evidence for sea level rise in the area during the Holocene. This pyrite is assumed to have been formed about 6,000 years BP when the sea level rose 3-5 m above the present. Its oxidation has caused untold damage to the productivity of the paddy soils in the area.

  6. Iron Phosphate Coating:A Novel Approach to Controlling Pyrite Oxidation

    Institute of Scientific and Technical Information of China (English)



    A novel coating technique was develped for controlling pyrite oxidation .The technique involved leaching pyrite particles with a solution containing low concentrations of phosphate and hydrogen peroxide.During the leaching rpocess,the iron released from pyrite by hydrogen proxide was precipitated by phosphate as a ferric phosphate coating .This coating was shown to be able to effectively prevent pyirte from oxidation and it could be established at the expense of only surface portions of pyrite.The emergence of this technique could provide a unique potential route for abating acid mine draingage and reclaiming sulfide-containing degraded mining land.

  7. Paleoredoc and pyritization of soft-bodied fossils in the Ordovician Frankfort Shale of New York

    DEFF Research Database (Denmark)

    Farrell, Una C.; Briggs, Derek E. G.; Hammarlund, Emma U.


    Multiple beds in the Frankfort Shale (Upper Ordovician, New York State), including the original "Beecher's Trilobite Bed," yield fossils with pyritized soft-tissues. A bed-by-bed geochemical and sedimentological analysis was carried out to test previous models of soft-tissue pyritization by inves......Multiple beds in the Frankfort Shale (Upper Ordovician, New York State), including the original "Beecher's Trilobite Bed," yield fossils with pyritized soft-tissues. A bed-by-bed geochemical and sedimentological analysis was carried out to test previous models of soft-tissue pyritization...

  8. Spectroscopic study of cystine adsorption on pyrite surface: From vacuum to solution conditions

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Arenillas, M.; Mateo-Marti, E., E-mail:


    Highlights: • Successful adsorption of cystine on pyrite surface under several conditions. • Detailed XPS spectroscopic characterization of cystine adsorption on pyrite surface. • Spectroscopy evidence, oxidation and anoxic conditions adjust molecular adsorption. • Molecular chemistry on pyrite is driven depending on the surrounding conditions. • The cystine/pyrite(100) model is in good agreement with Wächtershäuser’s theory. - Abstract: We characterized the adsorption of cystine molecules on pyrite surface via X-ray photoelectron spectroscopy. Anoxic conditions were simulated under ultra-high-vacuum conditions. In contrast, to simulate oxidation conditions, the molecules were adsorbed on pyrite surface from solution. A novel comparative analysis revealed remarkable differences with respect to molecular adsorption and surface chemistry induced by environmental conditions. Molecular adsorption under anoxic conditions was observed to be more favorable, concentrating a large number of molecules on the surface and two different chemical species. In contrast, the presence of oxygen induced an autocatalytic oxidation process on the pyrite surface, which facilitated water binding on pyrite surface and partially blocked molecular adsorption. Pyrite is a highly reactive surface and contains two crucial types of surface functional groups that drive molecular chemistry on the surface depending on the surrounding conditions. Therefore, the system explored in this study holds interesting implications for supporting catalyzed prebiotic chemistry reactions.

  9. Hot-Water Deposition of Pyritic Stromatolite and Its Relation to Biomineralization

    Institute of Scientific and Technical Information of China (English)


    Pyritic stromatolite, a rich pyrite ore, is scattered as reef masses in sedex deposits of the Proterozoic Yanshan rift trough. The pyritic stromatolite consists of a core and alternating concentric rims of light colloidal pyrite and dark organic materials. The concentric rims are cemented together by trichomes highly similar to the trichomic microorganisms inhabiting substantively around the black chimneys on the current sea beds while the core is composed chiefly of groups of thermophilous sulphur bacteria. Biomarkers for the molecules of pyritic stromatolite include pristane, phytane, regular isoprenoids paraffin, methyl-heptadecyl, and so on. This study reveals the existence of methane-yielding bacteria in the pyritic stromatolite and reflects the evolution of thermophilous thallophyta.Long pulsation of mineralizing thermal solutions venting up along contemporaneous faults in rift troughs contributed greatly not just to the reproduction of thermophilous organisms living around the vents, but to their adsorption of Fe2+ from the solutions in a reducing environment. Pyritic stromatolite constantly took shape through metabolism and reduction of these organisms. Owing to the uneven development of the organic communities close to the vents or the hydrothermal plumes, pyritic stromatolite occurred eventually as scattered reef masses. This mineralizing mechanism may be summarized as the following procedure: flowing of hydrothermal fluids associated with submarine exhalation(r) adsorption and metabolism of thermophilous micro-organisms(r) reduction of organic materials(r) formation of deposits of pyritic stromatolite.

  10. Re-Os Isotopic Dating of Molybdenite of Pingdi Molybdenum Deposits in Wuyishan,Fujian Province and Its Geological Significance%福建武夷山坪地钼矿辉钼矿铼-锇同位素定年及其地质意义

    Institute of Scientific and Technical Information of China (English)

    王翠芝; 李超


    this molybdenum deposit. We collected molybdenites with different occurrences and elevations from different ore bodies of Pingdi molybnum deposits for Re-Os isotopic dating. The isochron age of (102.9 ±1.8) Ma(MSWD =2.1) , and the model age of (107.4 ±3. 3) Ma ( MSWD = 16) were obtained. This results indicated the multi-stages mineralization with three types of molybdenite such as fine veins in rock of K-feldspar granite, thick veins in "bedding joint" of K-feldspar granite and in breccia silicified rocks controlled by fractures, which were formed in different metallogenic phases ,(111.20 ±1.7) Ma-(111. 60 ±1.6) Ma, (105.60 ±1.6) Ma - (107.40 ± 1. 6) Ma and (103.70±1.7) Ma, the mineralization periods during late stage of early cretaceous. This isotopic data provided the new geochemical evidences for Mesozoic tectonic magma evolution and guided regional ore-exploration of Pucheng-Ningde NW tectonic belt of Southeast coast of Fujian Province.

  11. The Re-Os isotope system of the Xiongcun porphyry copper-gold deposit, Tibet%西藏雄村斑岩铜矿床辉钼矿Re-Os同位素体系

    Institute of Scientific and Technical Information of China (English)

    黄勇; 唐菊兴; 丁俊; 张丽; 郎兴海


    辉钼矿Re-Os同位素测年是现今研究斑岩铜矿成矿时限最有效的手段.本文通过开展冈底斯成矿带雄村斑岩铜金矿辉钼矿Re-Os同位素年代学研究,并结合前人已发表的数据,认为雄村斑岩铜金矿床成矿时限为171~175Ma.Ⅰ号矿体可能受到始新世大规模的岩浆活动扰动,辉钼矿在经历过后期热事件影响,在辉钼矿中形成有极微量富Re的K-硅酸盐矿物,Ⅰ号矿体辉钼矿Re含量比Ⅱ号矿体以及Ⅲ号矿体中辉钼矿Re含量高出1~4倍,其Re-Os同位素年龄比真实年龄偏低,不能完全代表成矿年龄.同时通过与冈底斯成矿带斑岩-矽卡岩铜钼矿床,钼/钼铜矿床的对比研究后发现,雄村斑岩铜金矿中辉钼矿Re含量比同一成矿带上中新世斑岩铜钼矿床中辉钼矿Re含量高出一个数量级,比古新世—始新世斑岩钼矿/钼铜矿床中辉钼矿Re含量高出两个数量级.辉钼矿Re含量变化特征与成矿物质的来源、钼的浓度、成矿母岩组分以及成矿期间的物理/化学条件有关.%Re-Os dating of molybdenite is an efficient means to restrict the time of mineralization. The age of mineralization of the Xiongcun porphyry copper-gold deposit is confined between 171 Ma and 175 Ma based on this study and other data available. No. Ⅰ ore body of the Xiongcun deposit was affected by later magmtic thermal event. Molybdenite contains trace K-Si silicate enriched in Re. As a result of this event, the Re content of molybdenite is one to four times higher than that of molybdenite in No.Ⅱ ore body and No. Ⅲ ore body, and the age of molybdenite in No. Ⅰ ore body is younger than the real age. The authors also compared the Re content of molybdenite between this deposit and other porphyry-skarn deposits within this belt and found that the content of Re shows systematic variation. The Re content of the Xiongcun porphyry copper-gold deposit is one order of magnitude high than that of Miocene

  12. Re-Os dating of mineralization in Siah Kamar porphyry Mo deposit (NW Iran) and investigating on its temporal relationship with porphyry Cu-Mo deposits in the southern Lesser Caucasus, NW and central Iran (United States)

    Simmonds, Vartan; Moazzen, Mohssen; Selby, David


    The Neo-Tethyan basin closure in Iran is characterized by the Urumieh-Dokhtar magmatic arc (UDMA), formed by north-eastward subduction of the Neo-Tethyan oceanic crust during the Alpine orogeny. This belt also coincides with the porphyry copper metallogenic belt of Iran, which hosts many porphyry Cu-Mo deposits (PCDs) and prospects, such as Sungun (NW Iran) and Sarcheshmeh (central Iran). The Siah Kamar porphyry Mo deposit (PMD) is the first discovered porphyry molybdenum deposit on this belt, which is located 10 km west of Mianeh (NW Iran), with 39.2 Mt proved reserves @ 539 ppm Mo and 66.4 Mt probable reserves @ 266 ppm Mo. The host porphyry stock has quartz-monzonitic composition, which intruded the volcanic and pyroclastic rocks of Eocene age. Re content of molybdenites is about 10.44-41.05 ppm which, considering the several tens of ppm concentration, is comparable with porphyry Mo deposits (e.g., Climax in USA), being clearly distinguished from porphyry Cu-Mo deposits. Re-Os dating of molybdenites from this PMD has given model ages between 28.1±0.15 to 29.06±0.2 Ma, and isochron age of 28.0±2.1 Ma, corresponding to the middle Oligocene (upper part of Rupelian). Comparing the ages determined for Siah Kamar PMD with porphyry Cu-Mo mineralizations in the Lesser Caucasus indicates that it is younger than most of the dated PCDs and prospects there, especially those of upper Eocene, while it is a little older than Paragachay and first-stage Kadjaran PCDs [1]. In a regional scale of NW Iran, it shows a narrow overlap with vein-type Cu-Mo-Au mineralizations in Qarachilar (Qaradagh batholith) and is nearly coeval with Haftcheshmeh PCD, indicating that mineralization in the Siah Kamar PMD corresponds to the second porphyry mineralization epoch in NW Iran, proposed by [2]. Meanwhile, mineralization in Siah Kamar is older than all the porphyry Cu-Mo mineralizations along the central and SE parts of the UDMA, except the Bondar Hanza PCD in Kerman zone, which nearly

  13. Molybdenite Re/Os dating, zircon U-Pb age and geochemistry of granitoids in the Yangchuling porphyry W-Mo deposit (Jiangnan tungsten ore belt), China: Implications for petrogenesis, mineralization and geodynamic setting (United States)

    Mao, Jingwen; Xiong, Bikang; Liu, Jun; Pirajno, Franco; Cheng, Yanbo; Ye, Huishou; Song, Shiwei; Dai, Pan


    The Yangchuling W-Mo deposit, located in the Jiangnan porphyry-skarn (JNB) tungsten ore belt, is the first recognized typical porphyry W-Mo deposit in China in the 1980's. Stockworks and disseminated W-Mo mineralization occur in the roof pendant of a 0.3 km2 monzogranitic porphyry stock that intruded into a granodiorite stock, hosted by Neoproterozoic phyllite and slate. LA-ICPMS zircon U-Pb analyses suggest that of the monzogranitic porphyry and granodiorite were formed at 143.8 ± 0.5 Ma and 149.8 ± 0.6 Ma, respectively. Six molybdenite samples yielded a Re-Os weighted mean age of 146.4 ± 1.0 Ma. Geochemical data show that both granodiorite and monzogranitic porphyry are characterized by enrichment of large ion lithophile elements (LILE) relative to high field strength elements (HFSE), indicating a peraluminous nature (A/CNK = 1.01-1.08). Two granitoids are characterized by a negative slope with significant light REE/heavy REE fractionation [(La/Yb)N = 8.38-23.20] and negative Eu anomalies (Eu/Eu* = 0.69-0.76). The P2O5 contents of the Yangchuling granitoids range from 0.12% to 0.17% and exhibit a negative correlation with SiO2, reflecting that they are highly fractionated I-type. They have high initial 87Sr/86Sr ratios (0.7104-0.7116), low negative εNd(t) (- 5.05 to - 5.67), and homogeneous εHf(t) between - 1.39 and - 2.17, indicating similar sources. Additionally, two-stage Nd model ages (TDM2) of 1.3-1.4 Ga and two-stage Hf model ages (TDM2) of 1.2-1.3 Ga are consistent, indicating that Neoproterozoic crustal rocks of the Shuangqiaoshan Group could have contributed to form the Yangchuling magmas. Considering the two groups of parallel Late Mesozoic ore belts, namely the Jiangnan porphyry-skarn tungsten belt (JNB) in the south and the Middle-Lower Yangtze River porphyry-skarn Cu-Au-Mo-Fe ore belt (YRB) in the north, the Nanling granite-related W-Sn ore belt (NLB) in the south, the neighboring Qin-Hang porphyry-skarn Cu-Mo-hydrothermal Pb-Zn-Ag ore belt (QHB

  14. Study of initial stage of mechanochemical transformation in pyrite

    Directory of Open Access Journals (Sweden)

    Paneva D.


    Full Text Available The initial stage of transformation of pyrite to Fe(II-sulfate as a result of mechanical milling is studied by X-ray powder diffraction (XRD, Moessbauer spectroscopy (MS, Infrared (IR and X-ray photoelectron spectroscopy (XPS techniques. A degree of conversion of 0.071 is achieved in the time interval of 0 36 min. The kinetic data satisfy the equation of a shrinking core reaction 1-(1-α1/3=kt. The reaction is of the first order. The calculated rate constant is k=6.434.10-4 min-1. .

  15. Molecular Ink Processed Iron Pyrite Thin Films for Photovoltaics


    Weber, Amanda Sue


    Thin-film photovoltaics (PV) have the potential to supply our future energy needs, but the dominant commercial thin film technologies rely on rare or toxic elements that may limit their capacity to scale to the terawatt levels of electricity generation needed to impact global energy demand. Iron pyrite (FeS2) is a promising, earth-abundant material that has a suitable band gap of 0.95 eV, a large optical absorption coefficient, and adequate carrier diffusion lengths for use in PV. Unfortunate...

  16. Manipulation of pyrite colonization and leaching by iron-oxidizing Acidithiobacillus species. (United States)

    Bellenberg, Sören; Barthen, Robert; Boretska, Mariia; Zhang, Ruiyong; Sand, Wolfgang; Vera, Mario


    In this study, the process of pyrite colonization and leaching by three iron-oxidizing Acidithiobacillus species was investigated by fluorescence microscopy, bacterial attachment, and leaching assays. Within the first 4-5 days, only the biofilm subpopulation was responsible for pyrite dissolution. Pyrite-grown cells, in contrast to iron-grown cells, were able to oxidize iron(II) ions or pyrite after 24 h iron starvation and incubation with 1 mM H₂O₂, indicating that these cells were adapted to the presence of enhanced levels of reactive oxygen species (ROS), which are generated on metal sulfide surfaces. Acidithiobacillus ferrivorans SS3 and Acidithiobacillus ferrooxidans R1 showed enhanced pyrite colonization and biofilm formation compared to A. ferrooxidans (T). A broad range of factors influencing the biofilm formation on pyrite were also identified, some of them were strain-specific. Cultivation at non-optimum growth temperatures or increased ionic strength led to a decreased colonization of pyrite. The presence of iron(III) ions increased pyrite colonization, especially when pyrite-grown cells were used, while the addition of 20 mM copper(II) ions resulted in reduced biofilm formation on pyrite. This observation correlated with a different extracellular polymeric substance (EPS) composition of copper-exposed cells. Interestingly, the addition of 1 mM sodium glucuronate in combination with iron(III) ions led to a 5-fold and 7-fold increased cell attachment after 1 and 8 days of incubation, respectively, in A. ferrooxidans (T). In addition, sodium glucuronate addition enhanced pyrite dissolution by 25%.

  17. Microbial acceleration of aerobic pyrite oxidation at circumneutral pH. (United States)

    Percak-Dennett, E; He, S; Converse, B; Konishi, H; Xu, H; Corcoran, A; Noguera, D; Chan, C; Bhattacharyya, A; Borch, T; Boyd, E; Roden, E E


    Pyrite (FeS2 ) is the most abundant sulfide mineral on Earth and represents a significant reservoir of reduced iron and sulfur both today and in the geologic past. In modern environments, oxidative transformations of pyrite and other metal sulfides play a key role in terrestrial element partitioning with broad impacts to contaminant mobility and the formation of acid mine drainage systems. Although the role of aerobic micro-organisms in pyrite oxidation under acidic-pH conditions is well known, to date there is very little known about the capacity for aerobic micro-organisms to oxidize pyrite at circumneutral pH. Here, we describe two enrichment cultures, obtained from pyrite-bearing subsurface sediments, that were capable of sustained cell growth linked to pyrite oxidation and sulfate generation at neutral pH. The cultures were dominated by two Rhizobiales species (Bradyrhizobium sp. and Mesorhizobium sp.) and a Ralstonia species. Shotgun metagenomic sequencing and genome reconstruction indicated the presence of Fe and S oxidation pathways in these organisms, and the presence of a complete Calvin-Benson-Bassham CO2 fixation system in the Bradyrhizobium sp. Oxidation of pyrite resulted in thin (30-50 nm) coatings of amorphous Fe(III) oxide on the pyrite surface, with no other secondary Fe or S phases detected by electron microscopy or X-ray absorption spectroscopy. Rates of microbial pyrite oxidation were approximately one order of magnitude higher than abiotic rates. These results demonstrate the ability of aerobic microbial activity to accelerate pyrite oxidation and expand the potential contribution of micro-organisms to continental sulfide mineral weathering around the time of the Great Oxidation Event to include neutral-pH environments. In addition, our findings have direct implications for the geochemistry of modern sedimentary environments, including stimulation of the early stages of acid mine drainage formation and mobilization of pyrite-associated metals

  18. Leaching of pyrite by acidophilic heterotrophic iron-oxidizing bacteria in pure and mixed cultures

    Energy Technology Data Exchange (ETDEWEB)

    Bacelar-Nicolau, P.; Johnson, D.B. [Univ. of Wales, Bangor (United Kingdom). School of Biological Sciences


    Seven strains of heterotrophic iron-oxidizing acidophilic bacteria were examined to determine their abilities to promote oxidative dissolution of pyrite (FeS{sub 2}) when they were grown in pure cultures and in mixed cultures with sulfur-oxidizing Thiobacillus spp. Only one of the isolates (strain T-24) oxidized pyrite when it was grown in pyrite-basal salts medium. However, when pyrite-containing cultures were supplemented with 0.02% (wt/vol) yeast extract, most of the isolates oxidized pyrite, and one (strain T-24) promoted rates of mineral dissolution similar to the rates observed with the iron-oxidizing autotroph Thiobacillus ferroxidans. Pyrite oxidation by another isolate (strain T-21) occurred in cultures containing between 0.005 and 0.05% (wt/vol) yeast extract but was completely inhibited in cultures containing 0.5% yeast extract. Ferrous iron was also needed for mineral dissolution by the iron-oxidizing heterotrophs, indicating that these organisms oxidize pyrite via the indirect mechanism. Mixed cultures of three isolates (strains T-21, T-232, and T-24) and the sulfur-oxidizing autotroph Thiobacillus thiooxidans promoted pyrite dissolution; since neither strains T-21 and T-23 nor T. thiooxidans could oxidize this mineral in yeast extract-free media, this was a novel example of bacterial synergism. Mixed cultures of strains T-21 and T-23 and the sulfur-oxidizing mixotroph Thiobacillus acidophilus also oxidized pyrite but to a lesser extent than did mixed cultures containing T. thiooxidans. Pyrite leaching by strain T -23 grown in an organic compound-rich medium and incubated either shaken or unshaken was also assessed. The potential environmental significance of iron-oxidizing heterotrophs in accelerating pyrite oxidation is discussed.

  19. Carrier-microencapsulation using Si-catechol complex for suppressing pyrite floatability

    Energy Technology Data Exchange (ETDEWEB)

    Jha, R.K.T.; Satur, J.; Hiroyoshi, N.; Ito, M.; Tsunekawa, M. [Hokkaido University, Hokkaido (Japan). Graduate School of Engineering


    Pyrite (FeS{sub 2}) is a common sulfide mineral associated with valuable metal minerals and coal, and it is rejected as a gangue mineral using physical separation techniques such as froth flotation and discharged into tailing pond. In the flotation, pyrite is frequently entrapped in the froth due to its hydrophobic nature. Formation of acid mine drainage due to the air-oxidation of pyrite in the tailing pond is also a serious problem. The authors have proposed carrier-microencapsulation (CME) as a method for suppressing both the floatability and oxidation of pyrite. In this method, pyrite is coated with a thin layer of metal oxide or hydroxide using catechol solution as a carrier combined with metal ions. The layer converts the pyrite surface from hydrophobic to hydrophilic and acts as a protective coating against oxidation. The present study demonstrates the effect of CME using Si-catechol complex to suppress the pyrite floatability: The bubble pick-up experiments showed that attachment of pyrite particles to air bubble is suppressed by the CME treatment at pH 4-10, Si-catechol complex concentration over 0.5 mol m{sup -3} and treatment time within 2 min. The Hallimond tube flotation experiments showed that the pyrite floatability is suppressed by the CME treatment even in the presence of typical flotation collectors such as kerosene and xanthate. SEM-EDX analysis confirmed that Si present on the pyrite surface treated by Si-catechol complex, implying that SiO{sub 2} or SiOH{sub 4} layer formed by the CME treatment convert the pyrite surface hydrophobic to hydrophilic.

  20. Sub-micron geochronology by EPMA (United States)

    Jercinovic, M. J.; Williams, M. L.; Berman, R.


    Actinide-bearing, geochronologically applicable accessory phases can exhibit remarkably complex internal compositional structures, commonly revealing polygenesis and allowing timing constraints to be placed on the structural and metamorphic evolution of multiply tectonized terrains. These fine-scale mineral domains have been revealed by high resolution compositional mapping by EPMA of natural monazite (LREE PO4), and can exist at nearly all spatial scales, including domains substantially below 1 micron in width. Accurate compositional characterization of such domains by any technique is difficult, but hardware and software developments in EPMA offer some opportunities to approach these challenging but important targets accurately. In this regard, we have analyzed Paloeproterozoic (ca. 1.8 Ga) monazite domains which penetrate along cleavage planes in larger, older monazite grains (ca. 2.55 and 2.37 Ga) from the Boothia peninsula, Nanavut Canada. As such, this represents a successful nanogeochronologic analysis. The direct analytical volume, as defined by the convolution of the error functions resulting from primary (beam) electron scattering and characteristic X-ray generation volume dimensions, can be restricted to considerably less than 1 micron with the use of high brightness sources (LaB6, CeB6, or Schottky) and modest beam energy (15kV or less) in monazite (Z ca. 39). However, the analysis is rendered far more complex by the effects of boundary fluorescence and beam damage. For this analysis, we use a high thermal/electrical conductivity double coating of aluminum and carbon to mitigate sample damage at high current density. Although imperfect (there remains a net loss of P relative to REEs and actinides), this analysis results in relatively minor counting errors relative to the concentrations, and accuracy can be further improved by use of time-dependent count acquisition methods. Reduction of the beam energy substantially below 10kV results in extreme damage

  1. Electrochemical Properties for Co-Doped Pyrite with High Conductivity

    Directory of Open Access Journals (Sweden)

    Yongchao Liu


    Full Text Available In this paper, the hydrothermal method was adopted to synthesize nanostructure Co-doped pyrite (FeS2. The structural properties and morphology of the synthesized materials were characterized using X-ray diffraction (XRD and scanning electron microscopy (SEM, respectively. Co in the crystal lattice of FeS2 could change the growth rate of different crystal planes of the crystal particles, which resulted in various polyhedrons with clear faces and sharp outlines. In addition, the electrochemical performance of the doping pyrite in Li/FeS2 batteries was evaluated using the galvanostatic discharge test, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that the discharge capacity of the doped material (801.8 mAh·g−1 with a doping ratio of 7% was significantly higher than that of the original FeS2 (574.6 mAh·g−1 because of the enhanced conductivity. Therefore, the doping method is potentially effective for improving the electrochemical performance of FeS2.

  2. Surfactant-Assisted Hydrothermal Synthesis of Single Phase Pyrite FeS2 Nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Wadia, Cyrus; Wu, Yue; Gul, Sheraz; Volkman, Steven; Guo, Jinghua; Alivisatos, Paul


    Iron pyrite nanocrystals with high purity have been synthesized through a surfactant-assisted hydrothermal reaction under optimum pH value. These pyrite nanocrystals represent a new group of well-defined nanoscale structures for high-performance photovoltaic solar cells based on non-toxic and earth abundant materials.

  3. Relationship between pyrite Stability and arsenic mobility during aquifer storage and recovery in southwest central Florida. (United States)

    Jones, Gregg W; Pichler, Thomas


    Elevated arsenic concentrations are common in water recovered from aquifer storage and recovery (ASR) systems in west-central Florida that store surface water. Investigations of the Suwannee Limestone of the Upper Floridan aquifer, the storage zone for ASR systems, have shown that arsenic is highest in pyrite in zones of high moldic porosity. Geochemical modeling was employed to examine pyrite stability in limestone during simulated injections of surface water into wells open only to the Suwannee Limestone with known mineralogy and water chemistry. The goal was to determine if aquifer redox conditions could be altered to the degree of pyrite instability. Increasing amounts of injection water were added to native storage-zone water, and resulting reaction paths were plotted on pyrite stability diagrams. Native storage-zone water plotted within the pyrite stability field, indicating that conditions were sufficiently reducing to allow for pyrite stability. Thus, arsenic is immobilized in pyrite, and its groundwater concentration should be low. This was corroborated by analysis of water samples, none of which had arsenic concentrations above 0.036 microg/L. During simulation, however, as injection/native storage-zone water ratios increased, conditions became less reducing and pyrite became unstable. The result would be release of arsenic from limestone into storage-zone water.

  4. Fabrication and characterization of PDLLA/pyrite composite bone scaffold for osteoblast culture

    Indian Academy of Sciences (India)

    Lifang Zhang; Yanyan Zheng; Chengdong Xiong


    A series of highly interconnected porous poly(D,L-lactide acid) (PDLLA)/pyrite (Zi-Ran-Tong, FeS2) scaffold containing 5–20% of pyrite was fabricated by particle leaching combined with the thermal-induced phase separation method. Pyrite (FeS2, named as Zi-Ran-Tong in Chinese medicine), as a traditional Chinesemedicine, has been used in the Chinese population to treat bone diseases and to promote bone healing. The mechanical properties of the PDLLA scaffold were significantly enhanced after the addition of pyrite. The osteoblastic ROS17/2.8 cell line was used and seeded on the PDLLA/pyrite scaffold to study its potential to support the growth of osteoblastic cells and to estimate the optimal dose of pyrite for bone tissue engineering. The effects of pyrite on cell proliferation and differentiation were evaluated by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide and alkaline phosphatase activity assay. The cells on the porous composite scaffold formed a continuous layer on the outer and inner surface observed by scanning electron microscopy and fluorescence microscope. The results strongly suggested that the PDLLA/pyrite composite scaffold could stimulate the growth of ROS17/2.8 cells in vitro and it could be potentially used as a scaffold for bone tissue engineering.

  5. Isotopic and microbiological signatures of pyrite-driven denitrification in a sandy aquifer

    NARCIS (Netherlands)

    Zhang, Y.-C.; Slomp, C.P.; Broers, H.P.; Bostick, B.; Passier, H.F.; Böttcher, M.E.; Omoregie, E.O.; Lloyd, J.R.; Polya, D.A.; Van Cappellen, P.


    Denitrificationdriven by pyrite oxidation can play a major role in the removal of nitrate from groundwater systems. As yet, limited information is available on the interactions between the micro-organisms and aqueous and mineral phases in aquifers where pyrite oxidation is occurring. In this study,

  6. Intermediary sulfur compounds in pyrite oxidation: implications for bioleaching and biodepyritization of coal

    Energy Technology Data Exchange (ETDEWEB)

    Schippers, A.; Rohwerder, T.; Sand, W. [Hamburg Univ. (Germany). Inst. fuer Allgemeine Botanik und Botanischer Garten


    Accumulation of elemental sulfur during pyrite oxidation lowers the efficiency of coal desulfurization and bioleaching. In the case of pyrite bioleaching by Leptospirillum ferrooxidans, an iron(II)-ion-oxidizing organism without sulfur-oxidizing capacity, from the pyritic sulfur moiety about 10% elemental sulfur, 2% pentathionate, and 1% tetrathionate accumulated by a recently described cyclic pyrite oxidation mechanism. In the case of pure cultures of Thiobacillus ferrooxidans and mixed cultures of L. ferrooxidans and T. thiooxidans, pyrite was nearly completely oxidized to sulfate because of the capacity of these cultures to oxidize both iron(II) ions and sulfur compounds. Pyrite oxidation in acidic solutions, mediated chemically by iron(III) ion, resulted in an accumulation of similar amounts of sulfur compounds as obtained with L. ferrooxidans. Changes of pH to values below 2 or in the iron ion concentration are not decisive for diverting the flux of sulfur compounds. The literature on pyrite bioleaching is in agreement with the findings indicating that the chemistry of direct and indirect pyrite leaching is identical. (orig.)

  7. Bio-reduction of pyrite investigated in a gas lift loop reactor

    NARCIS (Netherlands)

    Hol, A.; Weijden, van der R.D.; Weert, van G.; Kondos, P.; Buisman, C.J.N.


    To liberate gold from refractory pyrite, oxidative destruction techniques that consume lots of energy and generate acidic waste streams are custom. As an alternative the “bio-reduction” of pyrite is proposed and investigated in this study. Bio-reduction is an anaerobic process based on sulfate/sulfu

  8. Framboidal and idiomorphic pyrite in the upper Maastrichtian sedimentary rocks at Gabal Oweina, Nile Valley, Egypt: Formation processes, oxidation products and genetic implications to the origin of framboidal pyrite (United States)

    Soliman, Mamdouh F.; El Goresy, Ahmed


    The upper Maastrichtian organic-rich sediments studied at Gabal Oweina, Egypt, are moderately enriched in syngenetic and diagenetic pyrite. Pyrite occurs mostly as layers or bands, group of lamina, lenses, diagenetic intercalated pockets, burrow fills and disseminated individual pyrite framboids and crystals within the host sediments. The pyritic thin bands and lamina consist mostly of unconsolidated to compact-oriented pyrite (oriented along the bedding planes) in gypsiferous-clayey matrix and less common as poorly oriented pyrite crystallites. In several cases, pyrite crystals of the latter type depict zoning, fracturing and micro-concretions. Pyritic burrow fills are composed mainly of pyrite, phosphatic ooids, microfossils, glauconitic grains, poorly graphitized carbon and native sulfur. Pyrite replaces minerals other than gypsum, sulfur or carbon. It also replaces microfossils thus turning some of the phosphatic ooids and microfossils to pyritized pseudomorphs. None of the studied phosphate ooids or framboids contains any mackinawite, pyrrhotite or greigite. Based on the microscopic and SEM observations of the micro-textures of disseminated pyrite found at Gabal Oweina section, four morphological forms of primary pyrite could be identified: (1) Grouped multiple-framboids; (2) Individual framboids; (3) Pyrite idiomorphic crystal overgrowths on framboids and (4) Single and aggregates of euhedral pyrite crystals. The multiple-framboid formation may have emerged from three successive processes: nucleation and growth of individual aggregates of the microcrystals to form combined micro-framboids (the growth of framboids); and followed by grouping of the several pyrite framboids. Direct pyrite nucleation (shell formation), crystallization, and aggregation processes might complete a single framboid. The disseminated single and aggregated euhedral pyrite crystals bear evidence indicating that their formation was via nucleation and growth of pyrite crystallites and

  9. The coupled geochemistry of Au and As in pyrite from hydrothermal ore deposits (United States)

    Deditius, Artur P.; Reich, Martin; Kesler, Stephen E.; Utsunomiya, Satoshi; Chryssoulis, Stephen L.; Walshe, John; Ewing, Rodney C.


    The ubiquity of Au-bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of Au and As in this sulfide occurs under a wide range of physico-chemical conditions. Despite significant advances in the last 20 years, fundamental factors controlling Au and As ratios in pyrite from ore deposits remain poorly known. Here we explore these constraints using new and previously published EMPA, LA-ICP-MS, SIMS, and μ-PIXE analyses of As and Au in pyrite from Carlin-type Au, epithermal Au, porphyry Cu, Cu-Au, and orogenic Au deposits, volcanogenic massive sulfide (VHMS), Witwatersrand Au, iron oxide copper gold (IOCG), and coal deposits. Pyrite included in the data compilation formed under temperatures from ∼30 to ∼600 °C and in a wide variety of geological environments. The pyrite Au-As data form a wedge-shaped zone in compositional space, and the fact that most data points plot below the solid solubility limit defined by Reich et al. (2005) indicate that Au1+ is the dominant form of Au in arsenian pyrite and that Au-bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native Au. The analytical data also show that the solid solubility limit of Au in arsenian pyrite defined by an Au/As ratio of 0.02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal-chemical properties of pyrite and post-depositional alteration. Compilation of Au-As concentrations and formation temperatures for pyrite indicates that Au and As solubility in pyrite is retrograde; Au and As contents decrease as a function of increasing temperature from ∼200 to ∼500 °C. Based on these results, two major Au-As trends for Au-bearing arsenian pyrite from ore deposits are defined. One trend is formed by pyrites from Carlin-type and orogenic Au deposits where compositions are largely controlled by fluid-rock interactions and/or can be highly perturbed by changes in temperature and

  10. Lipid extraction and esterification for microalgae-based biodiesel production using pyrite (FeS2). (United States)

    Seo, Yeong Hwan; Sung, Mina; Oh, You-Kwan; Han, Jong-In


    In this study, pyrite (FeS2) was used for lipid extraction as well as esterification processes for microalgae-based biodiesel production. An iron-mediated oxidation reaction, Fenton-like reaction, produced an expected degree of lipid extraction, but pyrite was less effective than FeCl3 commercial powder. That low efficiency was improved by using oxidized pyrite, which showed an equivalent lipid extraction efficiency to FeCl3, about 90%, when 20 mM of catalyst was used. Oxidized pyrite was also employed in the esterification step, and converted free fatty acids to fatty acid methyl esters under acidic conditions; thus, the fatal problem of saponification during esterification with alkaline catalysts was avoided, and esterification efficiency over 90% was obtained. This study clearly showed that pyrite could be utilized as a cheap catalyst in the lipid extraction and esterification steps for microalgae-based biodiesel production.

  11. Pyrite surface interaction with selected organic aqueous species under anoxic conditions

    Directory of Open Access Journals (Sweden)

    Bebié Joakim


    Full Text Available The interaction between low-molecular weight organic compounds and pyrite under anoxic conditions has been studied using a combination of electrophoresis and batch sorption experiments. The results suggest that acetate, carbamide, ethylamine, formamide, purine, D-ribose, and adenine, as well as the amino acids alanine, cysteine and glycine, interact within the electrophoretic shearplane of the pyrite surface. The observed surface interaction between the negatively charged surface of pyrite and the organic aqueous species takes place regardless of the formal charge of the aqueous species of interest. This indicates that the interaction of organic molecules with pyrite surfaces under anoxic conditions is dictated by interactions with specific surface sites (thiol or iron surface sites rather than electrostatic forces. Dissolved metals typically enhance the interaction of the organics species. This enhancement is either due to an alteration in the distribution of thiol and iron groups on the pyrite surface or by the formation of ternary surface complexes.

  12. Occurrence and Geological Genesis of Pyrites in Late Paleozoic Coals in North China

    Institute of Scientific and Technical Information of China (English)

    刘大锰; 杨起; 等


    The occurrence and geological genesis of pyrites in Late Paleozoic colas of North china have been systematically studied in terms of coal petrology,coal chemistry,elemental geochemistry and sulfur isotope geochemistry.The results suggest that eight types of pyrite,i.e.,framboidal,automorphic graular,oolitic,massive,homogeneous spherical,allotriomorphic,nodular,joint-and fisure-filling pyrintes can be subdivided under the microscope,Four generations of pyrite are also reconized according to the shape,size,coexisting assemblage,spacial distribution relationship with macerals,the contents of sulfur and iron.atomic S/Fe ratios and associated elements in pryites.Sulfur in Late Palozoic colas of North China is of diverse source as evidenced by sulfur isotope variations in the pyrites.The δ34S values of pyrite generated at the early stage ted to be negative,and at the late stage,positive.

  13. Spectroscopic study of cystine adsorption on pyrite surface: From vacuum to solution conditions (United States)

    Sanchez-Arenillas, M.; Mateo-Marti, E.


    We characterized the adsorption of cystine molecules on pyrite surface via X-ray photoelectron spectroscopy. Anoxic conditions were simulated under ultra-high-vacuum conditions. In contrast, to simulate oxidation conditions, the molecules were adsorbed on pyrite surface from solution. A novel comparative analysis revealed remarkable differences with respect to molecular adsorption and surface chemistry induced by environmental conditions. Molecular adsorption under anoxic conditions was observed to be more favorable, concentrating a large number of molecules on the surface and two different chemical species. In contrast, the presence of oxygen induced an autocatalytic oxidation process on the pyrite surface, which facilitated water binding on pyrite surface and partially blocked molecular adsorption. Pyrite is a highly reactive surface and contains two crucial types of surface functional groups that drive molecular chemistry on the surface depending on the surrounding conditions. Therefore, the system explored in this study holds interesting implications for supporting catalyzed prebiotic chemistry reactions.

  14. Remnant colloform pyrite at the haile gold deposit, South Carolina: A textural key to genesis (United States)

    Foley, N.; Ayuso, R.A.; Seal, R.R.


    Auriferous iron sulfide-bearing deposits of the Carolina slate belt have distinctive mineralogical and textural features-traits that provide a basis to construct models of ore deposition. Our identification of paragenetically early types of pyrite, especially remnant colloform, crustiform, and layered growth textures of pyrite containing electrum and pyrrhotite, establishes unequivocally that gold mineralization was coeval with deposition of host rocks and not solely related to Paleozoic tectonic events. Ore horizons at the Haile deposit, South Carolina, contain many remnants of early pyrite: (1) fine-grained cubic pyrite disseminated along bedding; (2) fine- grained spongy, rounded masses of pyrite that may envelop or drape over pyrite cubes; (3) fragments of botryoidally and crustiform layered pyrite, and (4) pyritic infilling of vesicles and pumice. Detailed mineral chemistry by petrography, microprobe, SEM, and EDS analysis of replaced pumice and colloform structures containing both arsenic compositional banding and electrum points to coeval deposition of gold and the volcanic host rocks and, thus, confirms a syngenetic origin for the gold deposits. Early pyrite textures are present in other major deposits of the Carolina slate belt, such as Ridgeway and Barite Hill, and these provide strong evidence for models whereby the sulfide ores formed prior to tectonism. The role of Paleozoic metamorphism was to remobilize and concentrate gold and other minerals in structurally prepared sites. Recognizing the significance of paragenetically early pyrite and gold textures can play an important role in distinguishing sulfide ores that form in volcanic and sedimentary environments from those formed solely by metamorphic processes. Exploration strategies applied to the Carolina slate belt and correlative rocks in the eastern United States in the Avalonian basement will benefit from using syngenetic models for gold mineralization.

  15. Control of pyrite surface chemistry in physical coal cleaning. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Luttrell, G.H.; Yoon, R.H.; Richardson, P.E.


    In Part I, Surface Chemistry of Coal Pyrite the mechanisms responsible for the inefficient rejection of coal pyrite were investigated using a number of experimental techniques. The test results demonstrate that the hydrophobicity of coal pyrite is related to the surface products formed during oxidation in aqueous solutions. During oxidation, a sulfur-rich surface layer is produced in near neutral pH solutions. This surface layer is composed mainly of sulfur species in the form of an iron-polysulfide along with a smaller amount of iron oxide/hydroxides. The floatability coal pyrite increases dramatically in the presence of frothers and hydrocarbon collectors. These reagents are believed to absorb on the weakly hydrophobic pyrite surfaces as a result of hydrophobic interaction forces. In Part III, Developing the Best Possible Rejection Schemes, a number of pyrite depressants were evaluated in column and conventional flotation tests. These included manganese (Mn) metal, chelating agents quinone and diethylenetriamine (DETA), and several commercially-available organic depressants. Of these, the additives which serve as reducing agents were found to be most effective. Reducing agents were used to prevent pyrite oxidation and/or remove oxidation products present on previously oxidized surfaces. These data show that Mn is a significantly stronger depressant for pyrite than quinone or DETA. Important factors in determining the pyrite depression effect of Mn include the slurry solid content during conditioning, the addition of acid (HCl), and the amount of Mn. The acid helps remove the oxide layer from the surface of Mn and promotes the depression of pyrite by Mn.

  16. Semiconductor electrochemistry of coal pyrite. Final technical report, September 1990--September 1995

    Energy Technology Data Exchange (ETDEWEB)

    Osseo-Asare, K.; Wei, Dawei


    This project seeks to advance the fundamental understanding of the physico-chemical processes occurring at the pyrite/aqueous interface, in the context of coal cleaning, coal desulfurization, and acid mine drainage. Central to this research is the use of synthetic microsize particles of pyrite as model microelectrodes to investigate the semiconductor electrochemistry of pyrite. The research focuses on: (a) the synthesis of microsize particles of pyrite in aqueous solution at room temperature, (b) the formation of iron sulfide complex, the precursor of FeS or FeS{sub 2}, and (c) the relationship between the semiconductor properties of pyrite and its interfacial electrochemical behavior in the dissolution process. In Chapter 2, 3 and 4, a suitable protocol for preparing microsize particles of pyrite in aqueous solution is given, and the essential roles of the precursors elemental sulfur and ``FeS`` in pyrite formation are investigated. In Chapter 5, the formation of iron sulfide complex prior to the precipitation of FeS or FeS{sub 2} is investigated using a fast kinetics technique based on a stopped-flow spectrophotometer. The stoichiometry of the iron sulfide complex is determined, and the rate and formation constants are also evaluated. Chapter 6 provides a summary of the semiconductor properties of pyrite relevant to the present study. In Chapters 7 and 8, the effects of the semiconductor properties on pyrite dissolution are investigated experimentally and the mechanism of pyrite dissolution in acidic aqueous solution is examined. Finally, a summary of the conclusions from this study and suggestions for future research are presented in Chapter 9.

  17. Retention and reduction of uranium on pyrite surface; Retention et reduction de l'uranium a la surface de la pyrite

    Energy Technology Data Exchange (ETDEWEB)

    Eglizaud, N


    In the hypothesis of a storage of the spent fuel in a deep geological formation, understanding the uranium dispersion in the environment is important. Pyrite is a reducing mineral present in the Callovo-Oxfordian argilites, the geological formation actually studied for such a storage. However, pyrite impact on uranium migration has already been poorly studied. The aim of the study was to understand the mechanisms of uranium(VI) retention and reduction on the pyrite surface (FeS{sub 2}). Solution chemistry was therefore coupled with solid spectroscopic studies (XPS and Raman spectroscopy). All uranium-pyrite interactions experiments were performed under an anoxic atmosphere, in a glove box. Pyrite dissolution under anoxic conditions releases sulfoxy-anions and iron(II), which can then be adsorbed on the pyrite surface. This adsorption was confirmed by interaction experiments using iron(II) isotopic dilution. Uranium(VI) is retained by an exchange reaction with iron(II) adsorbed on sulphur sites, with a maximal amount of sorbed uranium at pH {>=} 5.5. Cobalt(II) and europium(III) are also adsorbed on the pyrite surface above pH 5.5 confirming then that reduction is not required for species to adsorb on pyrite. When the concentration of uranium retained is lower than 4 x 10{sup -9} mol g{sup -1}, an oxidation-reduction reaction leads to the formation of a uranium (VI) (IV) mixed oxide and to solid sulphur (d.o. {>=} -I). During this reaction, iron remains mostly at the +II oxidation degree. The reaction products seem to passivate the pyrite surface: at higher amounts of retained uranium, the oxidation-reduction reaction is no longer observed. The surface is saturated by the retention of (3.4 {+-} 0.8) x 10{sup -7} mol L{sup -1} of uranium(VI). Modelling of uranium sorption at high surface coverage ({>=} 4 x 10{sup -9} mol g{sup -1}) by the Langmuir model yields an adsorption constant of 8 x 10{sup 7} L mol{sup -1}. Finally, a great excess of uranium(VI) above the

  18. Ultrasonic ash/pyrite liberation. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Yungman, B.A.; Buban, K.S.; Stotts, W.F.


    The objective of this project was to develop a coal preparation concept which employed ultrasonics to precondition coal prior to conventional or advanced physical beneficiation processes such that ash and pyrite separation were enhanced with improved combustible recovery. Research activities involved a series of experiments that subjected three different test coals, Illinois No. 6, Pittsburgh No. 8, and Upper Freeport, ground to three different size fractions (28 mesh {times} 0, 200 mesh {times} 0, and 325 mesh {times} 0), to a fixed (20 kHz) frequency ultrasonic signal prior to processing by conventional and microbubble flotation. The samples were also processed by conventional and microbubble flotation without ultrasonic pretreatment to establish baseline conditions. Product ash, sulfur and combustible recovery data were determined for both beneficiation processes.

  19. Oxygen adsorption on pyrite (100) surface by density functional theory

    Institute of Scientific and Technical Information of China (English)

    孙伟; 胡岳华; 邱冠周; 覃文庆


    Pyrite (FeS2) bulk and (100) surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 (100) surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe2+ and S2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference.The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.

  20. All inorganic iron pyrite nano-heterojunction solar cells (United States)

    Kirkeminde, Alec; Scott, Randall; Ren, Shenqiang


    The large absorption coefficient of iron pyrite (FeS2) nanocrystals coupled with their low-cost and vast-abundance shows great promise as a potential photovoltaic absorber. Here, we demonstrate that bulk heterojunction (BHJ) nanostructures consisting of 80 nm FeS2 nanocubes (NCs) and 4 nm CdS quantum dot (QD) matrix, lead to a well-defined percolation network, which significantly improved open-circuit voltage (Voc) to 0.79 V and power conversion efficiency of 1.1% under AM 1.5 solar illumination. The localized surface plasmon resonances (LSPRs) arising from p-type colloidal FeS2 NCs exhibit plasmonic photoelectron conversion. Our approach can be applied to a wide range of colloidal nanocrystals exhibiting the LSPRs effect and is compatible with solution processing, thereby offering a general tactic to enhancing the efficiency of all inorganic BHJ solar cells and LSPRs-based NIR photodetectors.The large absorption coefficient of iron pyrite (FeS2) nanocrystals coupled with their low-cost and vast-abundance shows great promise as a potential photovoltaic absorber. Here, we demonstrate that bulk heterojunction (BHJ) nanostructures consisting of 80 nm FeS2 nanocubes (NCs) and 4 nm CdS quantum dot (QD) matrix, lead to a well-defined percolation network, which significantly improved open-circuit voltage (Voc) to 0.79 V and power conversion efficiency of 1.1% under AM 1.5 solar illumination. The localized surface plasmon resonances (LSPRs) arising from p-type colloidal FeS2 NCs exhibit plasmonic photoelectron conversion. Our approach can be applied to a wide range of colloidal nanocrystals exhibiting the LSPRs effect and is compatible with solution processing, thereby offering a general tactic to enhancing the efficiency of all inorganic BHJ solar cells and LSPRs-based NIR photodetectors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr32097e

  1. Role of hydrogen peroxide and hydroxyl radical in pyrite oxidation by molecular oxygen (United States)

    Schoonen, Martin A. A.; Harrington, Andrea D.; Laffers, Richard; Strongin, Daniel R.


    Hydrogen peroxide and hydroxyl radical are readily formed during the oxidation of pyrite with molecular oxygen over a wide range of pH conditions. However, pretreatment of the pyrite surface influences how much of the intermediates are formed and their fate. Acid-washed pyrite produces significant amounts of hydrogen peroxide and hydroxyl radical when suspended in air-saturated water. However, the hydrogen peroxide concentration shows an exponential decrease with time. Suspensions made with partially oxidized pyrite yield significantly lower amounts of hydrogen peroxide product. The presence of Fe(III)-oxide or Fe(III)-hydroxide patches facilitates the conversion of hydrogen peroxide to oxygen and water. Hence, the degree to which a pyrite surface is covered with patches of Fe(III)-oxide or Fe(III)-hydroxide patches is an important control on the concentration of hydrogen peroxide in solution. Hydrogen peroxide appears to be an important intermediate in the four-electron transfer from pyrite to molecular oxygen. Addition of catalase, an enzyme that decomposes hydrogen peroxide to water and molecular oxygen, to a pyrite suspension reduces the oxidation rate by 40%. By contrast, hydroxyl radical does not appear to play a significant role in the oxidation mechanism. It is estimated on the basis of a molecular oxygen and sulfate mass balance that 5-6% of the molecular oxygen is consumed without forming sulfate.

  2. [Characterization of oxidation on pyrite by in situ attenuated total reflection-Fourier transform infrared spectroscopy]. (United States)

    Zhang, Ping; Chen, Yong-Heng; Liu, Juan; Wang, Chun-Lin


    Pyrite is one of common natural minerals in the environment, which is easily oxidated and is the main source of acidity mine drainage (AMD). The study on the oxidation of pyrite is helpful to comprehend the mechanism of its pollution. In the present paper, the oxidation of pyrite under the condition of air and water was respectively investigated by the attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) through the designing experiment on the formation of carbon dioxide by the reaction of carbonate in pyrite with sulfuric acid formed by the oxidation of pyrite. The CO2 measurement by in situ ATR indicated that the oxidation rate of pyrite both in the air and in water both reduced by time and the latter reduced more obviously than the former, which indicates that the oxidation rate of pyrite in water is slower than that in the air. In the ATR measurement, the double absorption peaks at 2 350 cm(-1) that indicates CO2 have high selectivity, and permits the in situ analysis.

  3. Flocculation of Pyrite Fines in Aqueous Suspensions with Corn Starch to Eliminate Mechanical Entrainment in Flotation

    Directory of Open Access Journals (Sweden)

    Wei Ge


    Full Text Available The hydrophilic flocculation of pyrite fines in aqueous suspensions with corn starch was studied by measuring particle size distribution, microscopy observation and micro-flotation. Furthermore, the interaction of corn starch with pyrite was investigated by determining the adsorption density and based on zeta potential measurements and X-ray photoelectron spectrometer (XPS analysis in this work. The results of the particle size distribution measurement show that corn starch can effectively aggregate pyrite fines, and the pyrite floccules (flocs are sensitive to mechanical stirring. The micro-flotation results suggest that the mechanical entrainment of pyrite fines in flotation can be effectively eliminated through the formation of large-size flocs. The zeta potential of pyrite particles decreases with the addition of corn starch. The XPS results prove that carboxyl groups are generated on the digested corn starch, and both iron hydroxyl compounds and ferrous disulfide on the pyrite surface can chemically interact with the corn starch digested by sodium hydroxide.

  4. Particulate Pyrite Autotrophic Denitrification (PPAD) for Remediation of Nitrate-contaminated Groundwater (United States)

    Tong, S.; Rodriguez-Gonzalez, L. C.; Henderson, M.; Feng, C.; Ergas, S. J.


    The rapid movement of human civilization towards urbanization, industrialization, and increased agricultural activities has introduced a large amount of nitrate into groundwater. Nitrate is a toxic substance discharged from groundwater to rivers and leads to decreased dissolved oxygen and eutrophication. For this experiment, an electron donor is needed to convert nitrate into non-toxic nitrogen gas. Pyrite is one of the most abundant minerals in the earth's crust making it an ideal candidate as an electron donor. The overall goal of this research was to investigate the potential for pyrite to be utilized as an electron donor for autotrophic denitrification of nitrate-contaminated groundwater. Batch studies of particulate pyrite autotrophic denitrification (PPAD) of synthetic groundwater (100 mg NO3--N L-1) were set up with varying biomass concentration, pyrite dose, and pyrite particle size. Reactors were seeded with mixed liquor volatile suspended solids (VSS) from a biological nitrogen removal wastewater treatment facility. PPAD using small pyrite particles (treatment and promoted the utilization of pyrite in the field of environmental remediation.

  5. Geochronological constraints on the evolution of El Hierro (Canary Islands) (United States)

    Becerril, Laura; Ubide, Teresa; Sudo, Masafumi; Martí, Joan; Galindo, Inés; Galé, Carlos; Morales, Jose María; Yepes, Jorge; Lago, Marceliano


    New age data have been obtained to time constrain the recent Quaternary volcanism of El Hierro (Canary Islands) and to estimate its recurrence rate. We have carried out 40Ar/39Ar geochronology on samples spanning the entire volcanostratigraphic sequence of the island and 14C geochronology on the most recent eruption on the northeast rift of the island: 2280 ± 30 yr BP. We combine the new absolute data with a revision of published ages onshore, some of which were identified through geomorphological criteria (relative data). We present a revised and updated chronology of volcanism for the last 33 ka that we use to estimate the maximum eruptive recurrence of the island. The number of events per year determined is 9.7 × 10-4 for the emerged part of the island, which means that, as a minimum, one eruption has occurred approximately every 1000 years. This highlights the need of more geochronological data to better constrain the eruptive recurrence of El Hierro.

  6. Geochemical investigation of the galvanic effects during oxidation of pyrite and base-metals sulfides. (United States)

    Chopard, Aurélie; Plante, Benoît; Benzaazoua, Mostafa; Bouzahzah, Hassan; Marion, Philippe


    Predicting the water quality at mine sites is of significant importance for developing mines with respect for the environment. Acid mine drainage (AMD) occurs when sulfides are in contact with oxygen and water, and several parameters and mechanisms influence final drainage quality. Galvanic interactions influence the reactivity of sulfide minerals, which act as semi-conductors. These galvanic interactions have been insufficiently studied in the context of AMD generation. In this study, the influence of pyrite on the reactivity of sphalerite and chalcopyrite was investigated. Five blends, comprised of free grains of quartz/pyrite, quartz/chalcopyrite, quartz/sphalerite, quartz/pyrite/chalcopyrite, and quartz/pyrite/sphalerite, were subjected to geochemical testing. Five weathering cells were monitored over a 200-day period during which they were leached twice weekly. Leachates were analyzed for pH, Eh, electrical conductivity, and sulfate and metal concentrations. The results of these analyses showed that galvanic interactions occurred between free sulfide grains. Pyrite was galvanically protected over the full testing period in the quartz/pyrite/chalcopyrite blend, and partially protected in the quartz/pyrite/sphalerite blend. Moreover, the release of Cu from chalcopyrite and Zn, Mn, and Cd from sphalerite was accelerated in the presence of pyrite. This work provides a better understanding of the influence of pyrite on chalcopyrite and sphalerite reactivity by highlighting the galvanic effects. In the future, to improve the reliability of AMD prediction tests, galvanic interactions should be considered in both the prediction of the acid generation potential and the estimation of metal and metalloid release rates. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Adsorção de xantatos sobre pirita Adsorption of xanthate on pyrite

    Directory of Open Access Journals (Sweden)

    Fábio Garcia Penha


    Full Text Available This paper presents a study of adsorption of xanthate with alkyl chain of two (C2XK, four (C4XK and eight (C8XK atoms of carbon, on pyrite from Santa Catarina, Brazil. The results showed that pyrite surface changes from hydrophilic to hydrophobic when xanthate is adsorbed increasing the contact angle to 35º for C2XK, and to 90º for C4XK and C8XK. The rate of flotation of pyrite particles after adsorption increases with the increase of the number of carbon atoms in the alkyl chain in agreement with the results of contact angle measurements.

  8. Quantification of Pyritic Sulfur of One Colombian Coal by Mössbauer Spectroscopy (United States)

    Reyes, F.; Pérez Alcázar, G. A.; Barraza, J. M.; Bohórquez, A.; Tabares, J. A.


    The aim of this work was to identify and quantify by means of Mössbauer spectroscopy the amount of pyritic sulfur in coal samples of the Guachinte mine, Valle, Colombia. For the quantification a calibration curve for pyritic sulfur content vs. relative spectral area ratio of sulfur and pure (99.99%) Fe-powder was obtained, using Mössbauer spectroscopy. The samples used in the calibration were the representative ones of the fractions obtained after one and two hydrocyclonic removal processes of a homogeneous sample of raw coal. A linear relationship was obtained and used to determine the amount of pyritic sulfur of the original coal.

  9. Nickel mobilization in a groundwater well field: Release by pyrite oxidation and desorption from manganese oxides

    DEFF Research Database (Denmark)

    Postma, Dieke; Larsen, Flemming


    is furthermore characterized by enhanced Mn2+ concentrations. Apparently nickel accumulates on manganese oxides during pyrite oxidation. When the water table rises again, partially oxidized pyritic layers are resubmerged, and due to an insufficient supply of oxygen, the oxidation of Fe2+ released during pyrite...... oxidation becomes incomplete. The mobilized Fe2+ may reduce manganese oxides and thereby release large amounts of Ni2+ to the groundwater. Calculations using a surface complexation model indicate retardation of nickel to be strongly affected by bulk water composition. At the background groundwater...

  10. Selective separation of arsenopyrite from pyrite by biomodulation in the presence of Acidithiobacillus ferrooxidans. (United States)

    Chandraprabha, M N; Natarajan, K A; Somasundaran, P


    Effective methods for selective separation using flotation or flocculation of arsenopyrite from pyrite by biomodulation using Acidithiobacillus ferrooxidans are presented here. Adhesion of the bacterium to the surface of arsenopyrite was very slow compared to that to pyrite, resulting in a difference in surface modification of the minerals subsequent to interaction with cells. The cells were able to effectively depress pyrite flotation in presence of collectors like potassium isopropyl xanthate and potassium amyl xanthate. On the other hand the flotability of arsenopyrite after conditioning with the cells was not significantly affected. The activation of pyrite by copper sulfate was reduced when the minerals were conditioned together, resulting in better selectivity. Selective separation could also be achieved by flocculation of biomodulated samples.

  11. Electronic, thermodynamic and elastic properties of pyrite RuO_2

    Institute of Scientific and Technical Information of China (English)

    Yang Ze-Jin; Guo Yun-Dong; Wang Guang-Chang; Li Jin; Dai Wei; Liu Jin-Chao; Cheng Xin-Lu; Yang Xiang-Dong


    This paper calculates the elastic, thermodynamic and electronic properties of pyrite (Pa3) RuO_2 by the plane-wave pseudopotential density functional theory (DFT) method. The lattice parameters, normalized elastic constants, Cauchy pressure, brittle-ductile relations, heat capacity and Debye temperature are successfully obtained. The Murnaghan equation of state shows that pyrite RuO_2 is a potential superhard material. Internal coordinate parameter increases with pressure, which disagrees with experimental data. An analysis based on electronic structure and the pseudogap reveals that the bonding nature in RuO_2 is a combination of covalent, ionic and metallic bonding. A study of the elastic properties indicates that the pyrite phase is isotropic under usual conditions. The relationship between brittleness and ductility shows that pyrite RuO_2 behaves in a ductile matter at zero pressure and the degree of ductility increases with pressure.

  12. Geological significance of componential characteristics of pyrite from Shibaqinghao gold deposit in central Inner Mongolia, China

    Institute of Scientific and Technical Information of China (English)

    Yihong Liang; Hongying Zhang; Yanhua Ma


    There are two types of gold ore in Shibaqinghao gold deposit, mylonite ore and quartz vein ore. Pyrite accompanying with native gold in mylonite ore has Fe from 43.66 to 45.32 wt% and S from 52.64 to 53.55 wt%. It is clear that this kind of pyrite is poor in both sulphur and iron. That means that the mylonite ore may be related to metamorphic water. Pyrite in the quartz vein ore has Fe from 44.38 to 45.30 wt% and S from 53.08 to 54.00 wt%. It means that this kind of pyrite is poor in iron but rich in sulphur, while the quartz vein ore may be related to magma water.

  13. Pyrite Iron Sulfide Solar Cells Made from Solution Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Law, Matt [Univ. of California, Irvine, CA (United States)


    This document summarizes research done under the SunShot Next Generation PV II project entitled, “Pyrite Iron Sulfide Solar Cells Made from Solution,” award number DE-EE0005324, at the University of California, Irvine, from 9/1/11 thru 11/30/16. The project goal was to develop iron pyrite (cubic FeS2) as an absorber layer for solution-processible p-n heterojunction solar cells with a pathway to >20% power conversion efficiency. Project milestones centered around seven main Tasks: (1) make device-quality pyrite thin-films from solar ink; (2) develop an ohmic bottom contact with suitable low resistivity; (3) produce a p-n heterojunction with VOC > 400 mV; (4) make a solar cell with >5% power conversion efficiency; (5) use alloying to increase the pyrite band gap to ~1.2-1.4 eV; (6) produce a p-n heterojunction with VOC > 500 mV; and finally (7) make a solar cell with >10% power conversion efficiency. In response to project findings, the Tasks were amended midway through the project to focus particular effort on passivating the surface of pyrite in order to eliminate excessively-strong surface band bending believed to be responsible for the low VOC of pyrite diodes. Major project achievements include: (1) development and detailed characterization of several new solution syntheses of high-quality thin-film pyrite, including two “molecular ink” routes; (2) demonstration of Mo/MoS2 bilayers as good ohmic bottom contacts to pyrite films; (3) fabrication of pyrite diodes with a glass/Mo/MoS2/pyrite/ZnS/ZnO/AZO layer sequence that show VOC values >400 mV and as high as 610 mV at ~1 sun illumination, although these high VOC values ultimately proved irreproducible; (4) established that ZnS is a promising n-type junction partner for pyrite; (5) used density functional theory to show that the band gap of pyrite can be increased from ~1.0 to a more optimal 1.2-1.3 eV by alloying with oxygen; (6) through extensive measurements of ultrahigh

  14. New method for the simultaneous determination of pyrite content and proximate analysis in coal

    Energy Technology Data Exchange (ETDEWEB)

    Aylmer, D.M.; Rowe, M.W.


    A combined thermogravimetric and thermomagnetometric procedure using inert, oxidising and reducing gases is described. It is shown to give good agreement with the ASTM methods and to have advantages over the latter, especially as regards occluded or weathered pyrite.

  15. The role of sulfur-oxidizing bacteria Thiobacillus thiooxidans in pyrite weathering

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, K.; Tsunekawa, M.; Ohtsuka, T.; Konno, H. [Hokkaido University, Sapporo (Japan). Graduate School of Engineering


    The paper investigates the role of the sulfur-oxidizing bacteria Thiobacillus thiooxidans in pyrite weathering in order to clarify the effects of the bacteria on the dissolution behavior of pyrite and the formation of secondary minerals using Raman spectroscopy and powder X-ray diffraction (XRD) in addition to solution analysis. It was found that T. thiooxidans, when present with the iron-oxidizing bacteria Thiobacillus ferrooxidans, enhanced the dissolution of Fe and S species for pyrite, whereas T. thiooxidans alone did not oxidize pyrite. Enhancement of the consumption of elemental sulfur and regeneration of Fe(II) ions were also observed with T. thiooxidans together with T. ferrooxidans, while this did not occur with T. ferrooxidans alone.

  16. Copper-arsenic decoupling in an active geothermal system: A link between pyrite and fluid composition (United States)

    Tardani, Daniele; Reich, Martin; Deditius, Artur P.; Chryssoulis, Stephen; Sánchez-Alfaro, Pablo; Wrage, Jackie; Roberts, Malcolm P.


    Over the past few decades several studies have reported that pyrite hosts appreciable amounts of trace elements which commonly occur forming complex zoning patterns within a single mineral grain. These chemical zonations in pyrite have been recognized in a variety of hydrothermal ore deposit types (e.g., porphyry Cu-Mo-Au, epithermal Au deposits, iron oxide-copper-gold, Carlin-type and Archean lode Au deposits, among others), showing, in some cases, marked oscillatory alternation of metals and metalloids in pyrite growth zones (e.g., of Cu-rich, As-(Au, Ag)-depleted zones and As-(Au, Ag)-rich, Cu-depleted zones). This decoupled geochemical behavior of Cu and As has been interpreted as a result of chemical changes in ore-forming fluids, although direct evidence connecting fluctuations in hydrothermal fluid composition with metal partitioning into pyrite growth zones is still lacking. In this study, we report a comprehensive trace element database of pyrite from the Tolhuaca Geothermal System (TGS) in southern Chile, a young and active hydrothermal system where fewer pyrite growth rims and mineralization events are present and the reservoir fluid (i.e. ore-forming fluid) is accessible. We combined the high-spatial resolution and X-ray mapping capabilities of electron microprobe analysis (EMPA) with low detection limits and depth-profiling capacity of secondary-ion mass spectrometry (SIMS) in a suite of pyrite samples retrieved from a ∼1 km drill hole that crosses the argillic (20-450 m) and propylitic (650-1000 m) alteration zones of the geothermal system. We show that the concentrations of precious metals (e.g., Au, Ag), metalloids (e.g., As, Sb, Se, Te), and base and heavy metals (e.g., Cu, Co, Ni, Pb) in pyrite at the TGS are significant. Among the elements analyzed, As and Cu are the most abundant with concentrations that vary from sub-ppm levels to a few wt.% (i.e., up to ∼5 wt.% As, ∼1.5 wt.% Cu). Detailed wavelength-dispersive spectrometry (WDS) X

  17. Chalcophile Siderophile Trace Element Systematics of Hydrothermal Pyrite from Martian Regolith Breccia NWA 7533 (United States)

    Lorand, J.-P.; Hewins, R. H.; Humayun, M.; Remusat, L.; Zanda, B.; La, C.; Pont, S.


    Martian impact breccia NWA 7533 contains hydrothermal pyrite. Laser ablation ICPMS analyses show that its chalcophile siderophile element content was inherited from both early meteorite bombardment and later hydrothermal inputs from H2S fluids.

  18. Pyrite Genesis During Early Diagenesis in Yellow Sea and East China Sea

    Institute of Scientific and Technical Information of China (English)

    段伟民; 陈丽蓉


    The content and isotopic compositions of different sulphur species in pore-water and solid phases have been examined on five sediment cores taken from muddy sediment region in the Yellow Sea and the East China Sea. Relationships among these data have been investigated with the combination of morphology of mineral pyrite and organic matter so as to role out the diagenetic behaviour of sulphur species at the early stage of diagenesis in modern marine sediment and the origin of pyrite formation.

  19. Preparation of pyrite-coated sand grains for research on roll-type uranium deposits (United States)

    Gent, Carol A.


    Ordinary quartz sand grains can be coated with pyrite for use in laboratory experiments on the genetic geochemistry of roll-type uranium deposits. The sand is first added to a ferric chloride solution. The slow addition of sodium hydroxide to the mixture gives the sand grains an iron oxide coating. This coating is then converted to pyrite by reaction with hydrogen sulfide, thus yielding a product suitable for experimental use.

  20. The Fe removal through mineralogical phase transformation of pyrite by physicochemical method (United States)

    Kim, BongJu; Cho, Kanghee; Jo, JiYu; Bak, GeonYeong; Choi, NagChoul; Park*, Cheonyoung


    Gold is often associated with sulfide minerals (arsenopyrite, pyrite, chalcopyrite, pyrrhotite, galena) as ''invisible'' gold that is thought to consist either of submicrometer metallic particles or to be bound to sulfur in metal sulfide lattice. Pyrite is one of the major minerals accumulating gold in most ores, although a solubility of Au in nonarsenian pyrite is minor, and increased concentrations of gold are associated with arsenic content and iron deficiency. The objective of this study was to investigate the Fe removal through mineralogical phase transformation of pyrite by physical treatment (high frequency) and chemical leaching (ammonia solvent). The high frequency treatment experiment for the pyrite showed that (1) the pyrite phase was transformed pyrrhotite and magnetite, (2) mass loss of the sample by volatilization of included sulfur(S) in pyrite. The treated pyrite by high frequency was observed rim structure from photomicrograph result. Fe removal experiments for were performed under various conditions of high frequency exposure (10~60min), grain size (+140 mesh~-325mesh), sulfuric acid concentration (0.5~3.0M), ammonia sulfate concentration (1.7~6.8M), hydrogen peroxide concentration (0.5~3.0M). Increasing the high frequency exposure produced a positive effect on Fe removal in arsenopyrite. The highest percentage Fe removal of 95.53% was obtained under the following conditions by ammonia solvent: grain size = -325mesh, sulfuric acid concentration = 2.0M, ammonia sulfate concentration = 5.1M, hydrogen peroxide concentration = 1.0M. This subject is supported by Korea Ministry of Environment(MOE) as "Advanced Technology Program for Environmental Industry".

  1. Enhanced bioleaching on attachment of indigenous acidophilic bacteria to pyrite surface (United States)

    Wi, D. W.; Cho, K. H.; Kim, B. J.; Choi, N. C.; Park, C. Y.


    In recent years, bioleaching has been widely applied on an industrial scale due to the advantages of low cost and environment friendliness. The direct contact mechanism of bioleaching assumes the action of a metal sulfide-attached cell oxidizing the mineral by an enzyme system with oxygen to sulfate and metal cations. Fundamental surface properties of sulfide particles and leaching-bacteria in bioleaching play the key role in the efficiency of this process. The aim of this work is to investigate of direct contact bioleaching mechanism on pyrite through attachment properties between indigenous acidophilic bacteria and pyrite surfaces. The bacteria were obtained from sulfur hot springs, Hatchobaru thermal electricity plant in Japan. And pyrite was collected from mine waste from Gwang-yang abandoned gold mines, Korea. In XRD analyses of the pyrite, x-ray diffracted d-value belong to pyrite was observed. The indigenous acidophilic bacteria grew well in a solution and over the course of incubation pH decreased and Eh increased. In relation to a bacterial growth-curve, the lag phase was hardly shown while the exponential phase was very fast. Bioleaching experiment result was showed that twenty days after the indigenous acidophilic bacteria were inoculated to a pyrite-leaching medium, the bacterial sample had a greater concentration of Fe and Zn than within the control sample. In SEM-EDS analyses, rod-shaped bacteria and round-shaped microbes were well attached to the surface of pyrite. The size of the rod-shaped bacteria ranged from 1.05~1.10 ? to 4.01~5.38 ?. Round-shaped microbes were more than 3.0 ? in diameter. Paired cells of rod-shaped bacteria were attached to the surface of pyrite linearly.

  2. Application of fuel cell for pyrite and heavy metal containing mining waste (United States)

    Keum, H.; Ju, W. J.; Jho, E. H.; Nam, K.


    Once pyrite and heavy metal containing mining waste reacts with water and air it produces acid mine drainage (AMD) and leads to the other environmental problems such as contamination of surrounding soils. Pyrite is the major source of AMD and it can be controlled using a biological-electrochemical dissolution method. By enhancing the dissolution of pyrite using fuel cell technology, not only mining waste be beneficially utilized but also be treated at the same time by. As pyrite-containing mining waste is oxidized in the anode of the fuel cell, electrons and protons are generated, and electrons moves through an external load to cathode reducing oxygen to water while protons migrate to cathode through a proton exchange membrane. Iron-oxidizing bacteria such as Acidithiobacillus ferrooxidans, which can utilize Fe as an electron donor promotes pyrite dissolution and hence enhances electrochemical dissolution of pyrite from mining waste. In this study mining waste from a zinc mine in Korea containing 17 wt% pyrite and 9% As was utilized as a fuel for the fuel cell inoculated with A. ferrooxidans. Electrochemically dissolved As content and chemically dissolved As content was compared. With the initial pH of 3.5 at 23℃, the dissolved As concentration increased (from 4.0 to 13 mg/L after 20 d) in the fuel cell, while it kept decreased in the chemical reactor (from 12 to 0.43 mg/L after 20 d). The fuel cell produced 0.09 V of open circuit voltage with the maximum power density of 0.84 mW/m2. Dissolution of As from mining waste was enhanced through electrochemical reaction. Application of fuel cell technology is a novel treatment method for pyrite and heavy metals containing mining waste, and this method is beneficial for mining environment as well as local community of mining areas.

  3. Progressive oxidation of pyrite in five bituminous coal samples: An As XANES and 57Fe Mössbauer spectroscopic study (United States)

    Kolker, Allan; Huggins, Frank E.


    Naturally occurring pyrite commonly contains minor substituted metals and metalloids (As, Se, Hg, Cu, Ni, etc.) that can be released to the environment as a result of its weathering. Arsenic, often the most abundant minor constituent in pyrite, is a sensitive monitor of progressive pyrite oxidation in coal. To test the effect of pyrite composition and environmental parameters on the rate and extent of pyrite oxidation in coal, splits of five bituminous coal samples having differing amounts of pyrite and extents of As substitution in the pyrite, were exposed to a range of simulated weathering conditions over a period of 17 months. Samples investigated include a Springfield coal from Indiana (whole coal pyritic S = 2.13 wt.%; As in pyrite = detection limit (d.l.) to 0.06 wt.%), two Pittsburgh coal samples from West Virginia (pyritic S = 1.32–1.58 wt.%; As in pyrite = d.l. to 0.34 wt.%), and two samples from the Warrior Basin, Alabama (pyritic S = 0.26–0.27 wt.%; As in pyrite = d.l. to 2.72 wt.%). Samples were collected from active mine faces, and expected differences in the concentration of As in pyrite were confirmed by electron microprobe analysis. Experimental weathering conditions in test chambers were maintained as follows: (1) dry Ar atmosphere; (2) dry O2 atmosphere; (3) room atmosphere (relative humidity ∼20–60%); and (4) room atmosphere with samples wetted periodically with double-distilled water. Sample splits were removed after one month, nine months, and 17 months to monitor the extent of As and Fe oxidation using As X-ray absorption near-edge structure (XANES) spectroscopy and 57Fe Mössbauer spectroscopy, respectively. Arsenic XANES spectroscopy shows progressive oxidation of pyritic As to arsenate, with wetted samples showing the most rapid oxidation. 57Fe Mössbauer spectroscopy also shows a much greater proportion of Fe3+ forms (jarosite, Fe3+ sulfate, FeOOH) for samples stored under wet conditions, but much less

  4. Spatial Mapping for Managing Oxidized Pyrite (FeS2 in South Sumatra Wetlands, Indonesia

    Directory of Open Access Journals (Sweden)

    M. Edi Armanto


    Full Text Available The research aimed to analyze spatial mapping for managing oxidized pyrite (FeS2 in South Sumatra wetlands, Indonesia. The field observations are done by exploring several transect on land units. The field description refers to Soil Survey Staff (2014. Water and soil samples were taken from selected key areas for laboratory analysis. The vegetation data was collected by making sample plots (squares method placed on each vegetation type with plot sizes depending on the vegetation type, namely 10 x 10 m for secondary forests and 5 x 5 m for shrubs and grass. The observations of surface water level were done during the river receding with units of m above sea level (m asl. The research results showed that pyrite formation is largely determined by the availability of natural vegetation as Sulfur (S donors, climate and uncontrolled water balance and supporting fauna such as crabs and mud shrimp.  Climate and water balance as well as supporting faunas is the main supporting factors to accelerate the process of pyrite formation. Oxidized pyrite serves to increase soil acidity, becomes toxic to fish ponds and arable soils, plant growth and disturbing the water and soil nutrient balances. Oxidized pyrite is predominantly accelerated by the dynamics of river water and disturbed natural vegetation by human activities.  The pyrite oxidation management approach is divided into three main components of technologies, namely water management, land management and commodity management.

  5. Mineralogy, geochemistry and pyrite content of Bulgarian subbituminous coals, Pernik Basin

    Energy Technology Data Exchange (ETDEWEB)

    Kostova, I.; Petrov, O.; Kortenski, J. [Bulgarian Academy of Sciences, Sofia (Bulgaria). Inst. of Applied Mineralogy


    The mineralogy and geochemistry of Pernik subbituminous coals (coal bed A) and some genetic peculiarities related to the mineral formation were studied. The mineral matter of the coal consists chiefly of pyrite, kaolinite, siderite, quartz and calcite. Other minerals (dolomite, ankerite, plagioclase and some sulphates) are present in minor amounts, some occurring as accessory single crystals. Pyrite is them main mineral in these coals and exhibits a large array of textures and morphology. Isolated and clustered euhedral, bacterial and inorganic framboidal, cluster-like, homogeneous and microconcretional massive, infilling and replacing anhedral, and cleat-filling and fracture-filling infiltrational pyrite types were observed. Four stages of mineralization were distinguished: pyrite-kaolinite, pyrite, pyrte-siderite and sulphate stages. The amount of pyrite present in two sections of coal bed A was determined by quantitative powder X-ray diffraction analysis. The concentrations of 37 trace elements were determined. As, Cu, Co, Ni, Zn, Pb, V, Ti, Mo Rb, Cr and Mn are typomorphic for this coal. On the basis of their relation to organic or inorganic matter, four groups of trace elements were subdivided; and on the basis of cluster analysis four associations were differentiated. 19 refs., 31 figs., 2 tabs.

  6. Bio-oxidation of pyrite, chalcopyrite and pyrrhotite by Acidithiobacillus ferrooxidans

    Institute of Scientific and Technical Information of China (English)


    This paper deals with the bio-oxidation processes by Acidithiobacillus ferrooxidans of pyrite, chalcopyrite and pyrrhotite. Our experimental results show distinctive bio-oxidation characteristics for the three sulfide minerals. In the presence of A. ferrooxidans, the sulfide oxidation rates generally decrease in the order of pyrrhotite, chalcopyrite and pyrite. The pH during bio-oxidation of pyrite tends to decrease as a whole, whereas a rise-fall pattern was recorded for both chalcopyrite and pyrrhotite in their pH variations. No deposition was observed during the bio-oxidation of pyrite, suggesting a possible link to lower pH value in the process. However, large amounts of jarosite and element sulfur were determined in the bio-oxidation processes of chalcopyrite and pyrrhotite. A. ferrooxidans individuals were found directly as attachments to erosion pits on the smooth surface of pyrite. The erosion pits are similar to the bacterium in shape and length, and thus are probably products of dissolution of organic acid secreted by the cells on the mineral surface. More complicatedly, biofilm exists on the surfaces of chalcopyrite and pyrrhotite. This type of structured community of A. ferrooxidans is enclosed in the extracellular polymeric substances (EPS), and covered with the deposition generated in the bio-oxidation processes of chalcopyrite and pyrrhotite. Different bio-oxidation processes of pyrite, chalcopyrite and pyrrhotite may be linked mainly to characteristics of individual minerals and the pH in the reaction solution of the bio-oxidation system.

  7. A kinetic assessment of substantial oxidation by sulfolobus acidocaldarius in pyrite dissolution

    Energy Technology Data Exchange (ETDEWEB)

    Vitaya, V.B.; Koizumi, J.; Toda, K. (King Mongkuts Institute of Technology, Bangkok (Thailand). Dept. of Chemical Engineering)


    The relative contributions of biological and chemical reactions to the total rate of pyrite oxidation in the presence of Sulfolobus acidocaldarius were studied on the basis of experimental work coupled with mathematical modeling. Kinetic constants for the individual reactions were determined in independent experiments. The specific growth rate of cells on the pyrite surface, which is the only unknown parameter, was assumed to be [mu](s) 0.1 h[sup -1] and justified by the agreement of the simulated results of a proposed model and the experimental results. The model includes: reversible adsorption, biological dissolution of pyrite by the adsorbed cells, chemical dissolution of pyrite accompanied by the reduction of ferric ions to ferrous ions, biochemical oxidation of ferrous ions to ferric ions by free cells, and change of the surface area of pyrite particles. It is suggested that the contributions of direct (biological) and indirect (chemical) reaction to the total rate of pyrite oxidation were in a ratio of 2:1.

  8. Degradation of off-gas toluene in continuous pyrite Fenton system. (United States)

    Choi, Kyunghoon; Bae, Sungjun; Lee, Woojin


    Degradation of off-gas toluene from a toluene reservoir and a soil vapor extraction (SVE) process was investigated in a continuous pyrite Fenton system. The removal of off-gas toluene from the toluene reservoir was >95% by 8h in the pyrite Fenton system, while it was ∼97 % by 3h in classic Fenton system and then rapidly decreased to initial level by 8h. Continuous consumption of low Fe(II) concentration dissolved from pyrite surface (0.05-0.11 mM) was observed in the pyrite Fenton system, which can lead to the effective and successful removal of the gas-phase toluene due to stable production of OH radical (OH). Inhibitor and spectroscopic test results showed that OH was a dominant radical that degraded gas-phase toluene during the reaction. Off-gas toluene from the SVE process was removed by 96% in the pyrite Fenton system, and remnant toluene from rebounding effect was treated by 99%. Main transformation products from toluene oxidation were benzoic acid (31.4%) and CO2 (38.8%) at 4h, while traces of benzyl alcohol (1.3%) and benzaldehyde (0.7%) were observed. Maximum operation time of continuous pyrite Fenton system was estimated to be 56-61 d and its optimal operation time achieving emission standard was 28.9 d. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Research on Genesis of Pyrite near the Permian-Triassic Boundary in Meishan, Zhejiang, China

    Institute of Scientific and Technical Information of China (English)

    JIANG Yao-fa; TANG Yue-gang; CHOU Chen-lin


    The content and crystal forms of pyrite and sulfur isotope composition of pyrite sulfur as well as its vertical distribution near the Permian-Triassic (P/T) boundary in the Meishan section, Changxing county, Zhejiang province, China were studied using geological, petrological, mineralogical and geochemical methods (techniques). The result showed that the genesis of abundant pyrites in bed 24e2 at the uppermost part of the Changxing Formation in the Meishan section may be related to volcanic activity. In bed 24e2 of the Meishan section, pyrite has its highest content of 1.84% and the sulfur isotope composition has the highest δ34S value at +2.2‰ which is very similar to that of the average value of volcanic gas. There are some volcanic products such as β-quartz, siliceous cylinders and siliceous spherules which coexisted with pyrites in beds 24e2 and 24f. It can be concluded that a large quantity of volcanic ash fell into the South China Sea and was incorporated into marine sediments during the formation of limestone at the uppermost part of the Changxing Formation. The volcanic eruption with massive amounts of H2S and SO2 gas at the end of the Permian period resulted in the enrichment of H2S in the South China Sea areas. The reaction of H2S with reactive iron minerals formed the mass of abundant pyrites.

  10. Biogeochemistry of pyrite and iron sulfide oxidation in marine sediments

    DEFF Research Database (Denmark)

    Schippers, A.; Jørgensen, BB


    Pyrite (FeS2) and iron monosulfide (FeS) play a central role in the sulfur and iron cycles of marine sediments, They may be buried in the sediment or oxidized by O-2 after transport by bioturbation to the sediment surface. FeS2 and FeS may also be oxidized within the anoxic sediment in which NO3......-, Fe(III) oxides, or MnO2 are available as potential electron acceptors. In chemical experiments, FeS2 and FeS were oxidized by MnO2 but not with NO3- or amorphous Fe(III) oxide (Schippers and Jørgensen, 2001). Here we also show that in experiments with anoxic sediment slurries, a dissolution of tracer......-marked (FeS2)-Fe-55 occurred with MnO2 but not with NO3- or amorphous Fe(III) oxide as electron acceptor. To study a thermodynamically possible anaerobic microbial FeS, and FeS oxidation with NO3- or amorphous Fe(III) oxide as electron acceptor, more than 300 assays were inoculated with material from several...

  11. Early diagenetic pyrite morphology in a mudstone-dominated succession: the Lower Jurassic Cleveland Ironstone Formation, eastern England (United States)

    Taylor, K. G.; Macquaker, J. H. S.


    Diagenetic pyrite in the mudstones and ironstones of the Lower Jurassic Cleveland Ironstone Formation of eastern England exhibits two distinct morphologies: framboidal pyrite, commonly associated with organic matter, and euhedral pyrite, associated with detrital clay pellets. These two morphologies are mutually exclusive in occurrence. Framboidal pyrite is present in clay-rich mudstones, ooidal ironstones, apatite-rich units and some silt-rich mudstones. Euhedral pyrite is present in silt-rich and sand-rich mudstones. δ34S isotopic analysis of six samples of pyrite suggests that both types of pyrite morphology precipitated during early diagenesis from porewaters with open access to overlying sea-water, although both probably acted as sites for continued pyrite precipitation during burial. It is proposed that framboidal pyrite precipitated from iron-dominated porewaters at sites of sulfide supply (i.e. in the region of organic matter as a result of bacterial sulfate reduction) where, locally, sulfide production rates were high enough for porewaters to reach supersaturation with respect to FeS. Euhedral pyrite also precipitated from iron-dominated porewaters, but sulfide production rates from organic matter was such that FeS saturation was not reached at the sites of sulfide production. Instead, euhedral pyrite was precipitated directly from porewater when FeS2 saturation was reached. The control over pyrite morphology was probably the amount and reactivity of the organic matter within the deposited sediments. The sand-rich mudstones contained less reactive organic matter due to clastic dilution and deposition in shallower environments with O2-rich bottom waters. The ironstones and apatite-rich units were deposited under very low sedimentation rates, and as a result organic matter contents were very low and iron reduction dominated early diagenesis, which inhibited sulfate-reduction. The presence of minor framboidal pyrite within these units, however, suggests that

  12. High spatial resolution U-Pb geochronology and Pb isotope geochemistry of magnetite-apatite ore from the Pea Ridge iron oxide-apatite deposit, St. Francois Mountains, southeast Missouri, USA (United States)

    Neymark, Leonid; Holm-Denoma, Christopher S.; Pietruszka, Aaron; Aleinikoff, John N.; Fanning, C. Mark; Pillers, Renee M.; Moscati, Richard J.


    The Pea Ridge iron oxide-apatite (IOA) deposit is one of the major rhyolite-hosted magnetite deposits of the St. Francois Mountains terrane, which is located within the Mesoproterozoic (1.5–1.3 Ga) Granite-Rhyolite province in the U.S. Midcontinent. Precise and accurate determination of the timing and duration of oreforming processes in this deposit is crucial for understanding its origin and placing it within a deposit-scale and regional geologic context. Apatite and monazite, well-established U-Pb mineral geochronometers, are abundant in the Pea Ridge orebody. However, the potential presence of multiple generations of dateable minerals, processes of dissolution-reprecipitation, and occurrence of micrometer-sized intergrowths and inclusions complicate measurements and interpretations of the geochronological results. Here, we employ a combination of several techniques, including ID-TIMS and high spatial resolution geochronology of apatite and monazite using LA-SC-ICPMS and SHRIMP, and Pb isotope geochemistry of pyrite and magnetite to obtain the first direct age constraints on the formation and alteration history of the Pea Ridge IOA deposit. The oldest apatite TIMS 207Pb*/206Pb* dates are 1471 ± 1 and 1468 ± 1 Ma, slightly younger than (but within error of) the ~1474 to ~1473 Ma U-Pb zircon ages of the host rhyolites. Dating of apatite and monazite inclusions within apatite provides evidence for at least one younger metasomatic event at ~1.44 Ga, and possibly multiple superimposed metasomatic events between 1.47 and 1.44 Ga. Lead isotop analyses of pyrite show extremely radiogenic 206Pb/204Pb ratios up to ~80 unsupported by in situ U decay. This excess radiogenic Pb in pyrite may have been derived from the spatially associated apatite as apatite recrystallized several tens of million years after its formation. The low initial 206Pb/204Pb ratio of ~16.5 and 207Pb/204Pb ratio of ~15.4 for individual magnetite grains indicate closed U-Pb system behavior in

  13. DFT study on the galvanic interaction between pyrite (100) and galena (100) surfaces (United States)

    Ke, Baolin; Li, Yuqiong; Chen, Jianhua; Zhao, Cuihua; Chen, Ye


    The galvanic interaction between pyrite and galena surface has been investigated using density functional theory (DFT) method. The calculated results show that galvanic interactions between pyrite and galena surface are decreased with the increase of contact distance. The galvanic interactions still occurs even the distance larger than the sum of two atoms radius (≈2.8 Å), and the limit distance of galvanic interaction between galena and pyrite surface is about 10 Å, which is consistent with the quantum tunneling effect. Through Mulliken charge population calculation, it is found that electrons transfer from galena to pyrite. For galena surface, Pb 6s and 6p states lose electrons and S 3p state loses a small amount of electrons, which causes the electron loss of galena. For pyrite surface, Fe 4p state obtains large numbers of electrons, resulting in the decrease of positive charge of Fe atom. However, the 3p state of S atom loses a small numbers of electrons. The reactivity of mineral surface has also been studied by calculating the frontier orbitals of minerals. Results suggest that the highest occupied molecular orbital (HOMO) coefficients of galena are increased whereas those of pyrite are decreased with the enhancing galvanic interaction, indicating that the oxidation of galena surface would be enhanced due to the galvanic interaction. The Fukui indices and dual descriptor values of surface atoms suggest that the nucleophilicity of the galena surface increases, meanwhile, the electrophilicity of pyrite surface increases with the decrease of the contact distance. In addition, the density of states (DOS) of atoms results show that the activity of electrons in Pb 6s and 6p orbitals enhances while the activity of electrons in Fe 3d orbitals weaken due to the galvanic contact between minerals.

  14. Action time effect of lime on its depressive ability for pyrite

    Institute of Scientific and Technical Information of China (English)

    Tichang Sun


    Two sample groups of bulk concentrates consisting mainly of pyrite and chalcopyrite from Daye and Chenghchao Mines in Hubei Province of China were used to investigate the effect of the action time of lime on its depressive ability for pyrite. The experimental results conducted with different samples and collectors showed that the action time between lime and pyrite markedly influences the depressive ability of lime. The depressive ability of lime increased with the action time increasing. It was also proved that the depressive results obtained at a large lime dosage after a shorter action time are similar to those obtained at a small lime dosage after a longer action time. The increase of depressive ability of lime after a longer action time is because that there are different mechanisms in different action time. The composition on the surface of pyrite acted for different time with lime was studied by using ESCA (Electron Spectroscopic Chemical Analysis). The results showed that iron hydroxide and calcium sulphate formed on the pyrite surface at the presence of lime in the pulp but the amounts of iron hydroxide and calcium sulphate were different at different action time. At the beginning action time the compound formed on the pyrite surface was mainly calcium sulphate and almost no iron hydroxide formed; but with the action time increasing, iron hydroxide formed. The longer the action time, the more iron hydroxide and the less calcium sulphate formed. It was considered that the stronger depressive ability of lime after a longer action time is because more iron hydroxide forms on the pyrite surface.

  15. Geochronology of the Rio Formoso estuarine by {sup 210}Pb

    Energy Technology Data Exchange (ETDEWEB)

    Arruda, Gilberto N.; Lyra, Denilson T.; Melo, Julyanne T.B.; Farias, Emerson E.G.; Franca, Elvis J.; Santos, Thiago O., E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Souza Neto, Joao A., E-mail: [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil)


    Uranium series disequilibrium is useful for dating methods, in which profile sediments can be considered as historical records of anthropogenic events regarding the distribution and impacts of chemical substances on the environment. In this study, 2 deep sediment profiles (about 1 m) were collected, layered at each 3 cm, oven-dried and homogenized. The radiochemical separation of {sup 210}Pb consisted of using hydrobromic acid and an ion exchange resin (DOWEX) for precipitating {sup 210}Pb in the form of lead chromate. After 10 days, the radioactivity was therefore measured by means of the low level gas flow proportional counter, model S5-XLB, from Canberra. Sedimentation rate were obtained by CIC (Constant Initial Concentration) model assumes a constant sedimentation rate throughout the period over which unsupported {sup 210}Pb is measurable. Some sediment profiles were not dated since the percentage of sand was quite high in top layers or a high percentage of organic matter and water in excess were observed in the all sediment samples. {sup 210}Pb geochronology was successfully applied to age nine sediment profiles, in which higher sedimentation rates were observed in the middle portion of the estuarine probably related to shrimp farming impacts. By using geochronology, the detection of human impacts on chemical element distribution could be enhanced in the case of environmental monitoring studies in the Rio Formoso estuarine. (author)

  16. Dynamics of electrodeposition of tetraethylthioram disulphide(TETD) on pyrite surface

    Institute of Scientific and Technical Information of China (English)


    The electrode process of pyrite in diethyldithiocarbamate (DDTC) solution pH 11.4 was investigated by using cyclic voltammetry, potentiostatic and ehronopotentiometry. Tetraethylthioram disulphide (TETD) was electrodeposited on pyrite electrode surface as the electrode potential is higher than 0.2 V. The relationship of the current density caused by diffusion and reaction time can be ascertained as i = 1/(9.08×10-5 + 4.77 × 10-3 t0.5 ), and the diffusion coefficient of DDTC on pyrite surface is about 3.72×10-6 cm2/s.At pH 11.4, the thickness of TETD adsorbed on pyrite surface is about 1.63 molecule layer. The electrochemical dynamics equation of the reduction of TETD on pyrite surface is given as η = 0.116- 0.0641og[1-(t/τ)0.5]. The kinetic parameters were determined as follows: the exchange current density (io) is 3.08μA/cm2; the transmission coefficient(α) is 0.462.

  17. Pyrite Oxidation in Leaching Process of Radionuclides and Heavy Metals from Uranium Mill Tailings

    Institute of Scientific and Technical Information of China (English)


    Pyrite is a sensitive mineral in the geological environment, and its oxidation produces an important geochemical and environmental effect on the control of the redox and pH conditions. Column experiment results were used for modeling the geochemical processes in uranium mill tailings under lcaching conditions. Oxidation of pyrite dominates the control of the tailings leaching process. The experimental and modeling results show that the leachate chemistry changes substantially with the decrease in pyrite consumption. In the initial stage of the leaching experiment, the pyrite is consumed several hundred times greater than that in the later stages, for much more oxygen is present in the tailings in the initial stage. As the experiment continues, the tailings is gradually saturated with water and the oxygen concentration greatly decreases and so does pyrite consumption. The experimental and modeling results are useful for the design of mill tailing decommissioning., oxidation process and transport of radioactive nuclides and heavy metals can be constrained by controlling the oxygen concentration of tailings and the infiltration of meteoric water.

  18. Trace element mapping of pyrite from Archean gold deposits – A comparison between PIXE and EPMA

    Energy Technology Data Exchange (ETDEWEB)

    Agangi, A., E-mail: [University of Johannesburg, Department of Geology, Auckland Park 2006 (South Africa); Przybyłowicz, W., E-mail: [Materials Research Department, iThemba LABS, National Research Foundation, Somerset West 7129 (South Africa); AGH University of Science and Technology, Faculty of Physics & Applied Computer Science, Al. A. Mickiewicza 30, 30-059 Krakow (Poland); Hofmann, A., E-mail: [University of Johannesburg, Department of Geology, Auckland Park 2006 (South Africa)


    Chemical zoning of pyrites can record the evolution of mineralising fluids at widely varying P–T conditions ranging from diagenesis to medium-grade metamorphism. If preserved, zoning can reveal growth textures, brecciation and veining, resorption and recrystallisation events, thus shedding light on the processes that contributed to ore formation. Chemical zoning of sulfides is invisible in optical microscopy, but can be studied by chemical etching, high-contrast back-scattering electron images, and elemental imaging. In this study we compared micro-PIXE and WDS-EPMA elemental maps on the chemically zoned pyrites in mineralised vein-bearing samples from the Sheba and Fairview gold mines in the Barberton Greenstone Belt, South Africa. Elemental images show complex distribution of trace elements, suggesting multiple events of pyrite crystallisation and gold deposition. EPMA maps show fine-scale variations reflecting growth and recrystallisation textures marked, in particular, by variations of As, Ni, and Co. In PIXE maps, gold occurs both as finely-distributed and discrete inclusions, suggesting incorporation in the pyrite structure as solid solution, and deposition as electrum inclusions, respectively. Micro-PIXE and EPMA provide complementary information, forming together a powerful tool to obtain information on chemical zoning of pyrites in ore deposits.

  19. A demonstration of an affinity between pyrite and organic matter in a hydrothermal setting

    Directory of Open Access Journals (Sweden)

    Holm Nils G


    Full Text Available Abstract One of the key-principles of the iron-sulphur world theory is to bring organic molecules close enough to interact with each other, using the surface of pyrite as a substrate in a hydrothermal setting. The present paper explores the relationship of pyrite and organic matter in a hydrothermal setting from the geological record; in hydrothermal calcite veins from Carboniferous limestones in central Ireland. Here, the organic matter is accumulated as coatings around, and through, pyrite grains. Most of the pyrite grains are euhedral-subhedral crystals, ranging in size from ca 0.1-0.5 mm in diameter, and they are scattered throughout the matrix of the vein calcite. The organic matter was deposited from a hydrothermal fluid at a temperature of at least 200°C, and gives a Raman signature of disordered carbon. This study points to an example from a hydrothermal setting in the geological record, demonstrating that pyrite can have a high potential for the concentration and accumulation of organic materials.

  20. Pyrite Formation in Organic-rich Clay, Calcitic and Coal-Forming Environments

    Institute of Scientific and Technical Information of China (English)

    Gordana DEVI(C); Petar PFENDT; Branimir JOVAN(C)I(C)EVI(C); Zoran POPOVIC


    The early diagenetic characteristics of pyrite formation processes in a Miocene freshwater sequence of mixed sediments (coal fragments in clays, sandstones or shales) alternating with continuous brown coal layers was investigated. Based on abundant minerals, the following main sedimentary environments were distinguished: the illite-montmorillonitic (I-M), calcitic (Ct) and coal-forming environment (CL). For these hydrogeochemically differing environments the effects of limiting factors on the pyrite formation process (availability of sulphate and Fe, amount of organic matter and participation of organic sulphur) were assessed by correlation analysis. Significant differences in the effects of these limiting factors in the particular environments were observed. These differences were explained taking in account the different oxidative activity, Fe-complex and surface complex forming properties of hnmic substances in dependence of pH of environment and the abundance of sorptionally active clay minerals. In environments having a relatively low pH and containing clay minerals (I-Mand CL-environments) the oxidative activity of humic substances (Hs) on pyrite precursors was greatly prevented however pyrite formation depended on reactive Fe availability as the consequence of complex formation. On the contrary, in environments with a relatively high pH, as it was the calcitic,the oxidative activity of Hs was greatly enhanced, thus oxidizing the sulfur precursors of pyrite. The oxidation degree of organic matter was probably also a consequence of the differing activity of the humic electron-acceptors.

  1. New method for the simultaneous determination of pyrite content and proximate analysis in coal and lignite

    Energy Technology Data Exchange (ETDEWEB)

    Aylmer, D.M.


    The new method combines thermogravimetry and thermomagnetometry and utilizes inert, oxidizing, and reducing gases. Results by the new technique are compared to the ASTM method, one set obtained by the author on a Fisher Coal Analyzer and one set by the Coal Research Laboratory of the Pennsylvania State University. Comparison of thermo-magneto-gravimetric-analysis with the ASTM method indicates good agreement and comparable accuracy. These studies show that the thermo-magneto-gravimetric-analysis are: 1) ease of determination of both proximate analysis and pyrite, which permits use of unskilled technicians; 2) widespread availability of the apparatus; 3) cost effectiveness due to use of unskilled operators; 4) automation, presently available for proximate analysis on some commercial instruments and is easily accomplished for pyrite analysis, as well; 5) advantage over pyrite analysis by the ASTM method in two situations: first, when pyrite is totally surrounded by acid-insoluble organic-material and secondly where significant amounts of pyrite have been oxidized to FeSO/sub 4/; and 6) a permanent record of the measurements, which are continuous, is made in contrast to the ASTM method which records only initial and final conditions.

  2. [Limestone and pyrite-limestone constructed wetlands for treating river water]. (United States)

    Zhang, Jing; Li, Rui-hua; Li, Jie; Hu, Jun-song; Sun, Qian-qian


    Polluted river water was treated with limestone and pyrite-limestone subsurface horizontal constructed wetlands. The aims were to know the performance of two wetlands on removal of common pollutants, especially nitrogen and phosphorus, and analyze the actions of these minerals. The relationship between hydraulic retention time and purification performance of two constructed wetlands was studied. The optimal hydraulic retention time for pollutant removal was about 3 d, The average removal efficiency of COD, TN and TP were 51%, 70% and 95%, respectively. With same influent and hydraulic loading, the average removal efficiency of COD, NH4+ -N, TN and TP were 53.93%, 82.13%, 66%, 50.9%, and 51.66%, 77.43%, 72.06%, 97.35% for limestone and pyrite-limestone constructed wetlands, respectively. There were few differences between limestone and pyrite-limestone wetlands on COD removal, but the nitrogen and phosphorus removal of pyrite-limestone constructed wetland was higher than that of limestone constructed wetland. The phosphorus removal of pyrite-limestone wetland was more efficiency and stable, not affected by temperature.

  3. Galvanic Interaction between Chalcopyrite and Pyrite with Low Alloy and High Carbon Chromium Steel Ball

    Directory of Open Access Journals (Sweden)

    Asghar Azizi


    Full Text Available This study was aimed to investigate the galvanic interaction between pyrite and chalcopyrite with two types of grinding media (low alloy and high carbon chromium steel ball in grinding of a porphyry copper sulphide ore. Results indicated that injection of different gases into mill altered the oxidation-reduction environment during grinding. High carbon chromium steel ball under nitrogen gas has the lowest galvanic current, and low alloy steel ball under oxygen gas had the highest galvanic current. Also, results showed that the media is anodic relative to pyrite and chalcopyrite, and therefore pyrite or chalcopyrite with a higher rest potential acted as the cathode, whilst the grinding media with a lower rest potential acted as the anode, when they are electrochemically contacted. It was also found that low alloy steel under oxygen produced the highest amount of EDTA extractable iron in the slurry, whilst high carbon chromium steel under nitrogen atmosphere led to the lowest amount.

  4. Crystalomorphological Characteristics of Pyrite in Hydrothermal Gold Deposit--An Experimental Study

    Institute of Scientific and Technical Information of China (English)

    蔡元吉; 周茂


    On the basis of the geological characteristics of primary gold deposits, with an experiment on modelling the environment of gold mineralization , the evolutionary array and growth mechanism and their relationship with gold mineralization of the crystal forms of pyrite, i. e. pentagonal dodecahedron, octahedron and cube, formed under the different values of fo2, fs2, T (℃), P(Pa) and C (salinity) in the hy-drothermal system are studied. The results show that the crystal form of pyrite is not only related to the temperature L, but also affected by the geochemistry of iron and sulfur which formed pyrite and other physicochemical conditions.Our results promote the study of gold mineralization, genetic and prospecting mineralogy.

  5. Hydrometallurgical-UV process to produce ferrous sulfate from the pyrite present in coal tailings

    Energy Technology Data Exchange (ETDEWEB)

    Viganico, E.M.; Silva, R.A. [South Rio Grande Federal Univ., Porto Alegre (Brazil).Graduate Program in Mining, Metallurgical and Materials Technology Center


    The oxidation of pyrite can promote acid mine drainage (AMD). This study developed a hydrometallurgical-UV route for the production of ferrous sulfate. The laboratory study was conducted using a pyrite concentrate obtained from a processed coal tailing. Leaching of the tailing was performed in packed bed columns in an oxidizing environment with an aqueous medium. Recirculation of the liquor produced an Fe{sup 3+} iron rich extract. Ultraviolet irradiation was then used to convert the Fe{sup 3+} to Fe{sup 2+}. Heat provided by the UV lamps caused the ferrous sulfate to crystallize. X-ray diffraction (XRD) studies of the crystals demonstrated that it is possible to produce commercial-grade ferrous sulfate heptahydrate crystals from the pyrite present in coal tailings. The crystals are used to treat anemia in humans and animals, and are also used as reagents for waste and waste water treatment. 7 refs., 2 tabs., 2 figs.

  6. Ferruginous Microspherules in Bauxite at Maochang, Guizhou Province, China: Products of Microbe-Pyrite Interaction?

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yuefei; WANG Rucheng; LU Jianjun; LI Yiliang


    The Maochang bauxite in Guizhou Province is one of the important aluminum ore deposits in southwestern China. Ferruginous spherules, measuring about a few microns across, were found in the transitional layer of the deposit. The EDS and XRD results show that the microspherules are composed mostly of iron (hydr)oxide minerals (goethite) with only weak presence of aluminum and silicon.Occasionally, some pyrite micrograins with dissolved surface are found associated with goethite within the spherules. It is thus suggested that microspherules are linked to pyrite oxidization. It is also thought that microbial activities contribute not only to pyrite oxidization, but also to ball-like assemblage of the iron (hydr)oxides. The mechanism of the formation of ferruginous microspherules is also believed to be important in studying geomicrobiology of bauxite.

  7. Evidence for microbial dissolution of pyrite from the Lower Cambrian oolitic limestone, South China

    Directory of Open Access Journals (Sweden)

    W. Liu


    Full Text Available The oxidative dissolution of the sulphide mineral pyrite (FeS2 has been of significant interest since it affects global geochemical cycles, generates acid mine drainage, and is used in industrial metal extraction. Several different groups of prokaryotes are known to catalyze the dissolution of pyrite and use the free energy generated from the oxidation, which may result in the dissolution of the mineral and the precipitation of the secondary ferric iron minerals either on the cell surface or is separated from the cells. However, straightforward evidence for such metabolic process in the ancient sediments is rare. Here we report pyrite crystals from the Lower Cambrian oolitic limestones that show indications of microbial erosion in various degrees. Erosion pits and tubular micro-tunnels with characteristic shapes and sizes in our samples are generally similar to those obtained from the laboratory studies on the oxidative dissolution of pyrite by iron-oxidizing bacteria. Diagenetic examination demonstrates that the bioerosion predates the consolidation of the limestone. In addition, bacillus-sized and -shaped microfossils encrusted with iron oxides are present in our samples, which are very likely to be fossilized sheaths produced by iron-oxidizing bacteria. Our findings indicate that the microbial oxidative dissolution of pyrite existed in the Cambrian shallow marine carbonate sediments. Furthermore, we suggest that characteristic pitting patterns on the pyrite crystals from ancient sediments are an important clue to trace the evolution of life, in particular, the evolution of metabolism like microbial iron oxidation in the remote past on our planet, independent of biomarkers, isotopic signals and body fossils as well.

  8. Pyrite-enhanced methylene blue degradation in non-thermal plasma water treatment reactor

    Energy Technology Data Exchange (ETDEWEB)

    Benetoli, Luis Otavio de Brito, E-mail: [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil); Cadorin, Bruno Mena; Baldissarelli, Vanessa Zanon [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil); Geremias, Reginaldo [Departamento de Ciencias Rurais, Universidade Federal de Santa Catarina (UFSC), Curitibanos, SC (Brazil); Goncalvez de Souza, Ivan [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil); Debacher, Nito Angelo, E-mail: [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil)


    Highlights: Black-Right-Pointing-Pointer We use O{sub 2} as the feed gas and pyrite was added to the non-thermal plasma reactor. Black-Right-Pointing-Pointer The methylene blue removal by NTP increased in the presence of pyrite. Black-Right-Pointing-Pointer The total organic carbon content decreased substantially. Black-Right-Pointing-Pointer The acute toxicity test showed that the treated solution is not toxic. Black-Right-Pointing-Pointer The dye degradation occurs via electron impact as well as successive hydroxylation. - Abstract: In this study, methylene blue (MB) removal from an aqueous phase by electrical discharge non-thermal plasma (NTP) over water was investigated using three different feed gases: N{sub 2}, Ar, and O{sub 2}. The results showed that the dye removal rate was not strongly dependent on the feed gas when the electrical current was kept the same for all gases. The hydrogen peroxide generation in the water varied according to the feed gas (N{sub 2} < Ar < O{sub 2}). Using O{sub 2} as the feed gas, pyrite was added to the reactor in acid medium resulting in an accentuated increase in the dye removal, which suggests that pyrite acts as a Fenton-like catalyst. The total organic carbon (TOC) content of the dye solution decreased slightly as the plasma treatment time increased, but in the presence of the pyrite catalyst the TOC removal increased substantially. The acute toxicity test using Artemia sp. microcrustaceans showed that the treated solution is not toxic when Ar, O{sub 2} or O{sub 2}-pyrite is employed. Electrospray ionization mass spectrometry analysis (ESI-MS) of the treated samples indicated that the dye degradation occurs via high energy electron impact as well as successive hydroxylation in the benzene rings of the dye molecules.

  9. Geochronology and Tectonic Evolution of the Lincang Batholith in Southwestern Yunnan, China


    Hongyuan Zhang; Junlai Liu; Wenbin Wu


    Geochronological research of the Lincang Batholith is one key scientific problem to discuss the tectonic evolution of the Tethys. Two granitic specimens were selected from the Mengku-Douge area in the Lincang Batholith to perform the LA-ICPMS Zircon U-Pb dating based on thorough review of petrological, geochemical, and geochronological data by the former scientists. Rock-forming age data of biotite granite specimen from Kunsai is about 220 Ma, the Norian age. However, the west sample from Men...

  10. Contributions to the research on the principles of a pyrite solar cell. Beitraege zur Erforschung der Grundlagen einer Pyritsolarzelle

    Energy Technology Data Exchange (ETDEWEB)

    Sailer, B.


    Within the framework of the dissertation experiences on pyrite thin film production by plasma sulfurization of iron films and thermal sulfurization of iron films in closed, evacuated quartz ampullas are given. X-ray investigation show that both methods are suitable for pyrite thin film production. Problems have been shown concerning film porosity, film adhesion on the substrates and film stability. (BWI)

  11. Atomistic simulation of the structure and elastic properties of pyrite (FeS2) as a function of pressure

    CSIR Research Space (South Africa)

    Sithole, Happy M


    Full Text Available Interatomic potential parameters have been derived at simulated temperatures of 0 K and 300 K to model pyrite FeS2. The predicted pyrite structures are within 1% of those determined experimentally, while the calculated bulk modulus is within 7...

  12. Proving of Golden Pyrite (golden pyrite (Pyr-d. Patogenesia de Pirita dorada (pirita dorada (Pyr-d. Patogenesia de Pirita dorada (pirita dorada (Pyr-d.

    Directory of Open Access Journals (Sweden)

    Silvia Waisse Priven


    Full Text Available The results of the proving of Golden Pyrite are presented here. The proving followed the protocol adopted for Brosimum gaudichaudii, further modified to adjust to our group’s demands. They are also presented a thematic study of the remedy, its reportorial rubrics, its differential diagnosis and new rubrics that ought to be added to the repertory. The experience created the need of suggesting new practical guidelines to be included in the protocol.

  13. A combined chemical, isotopic and microstructural study of pyrite from roll-front uranium deposits, Lake Eyre Basin, South Australia (United States)

    Ingham, Edwina S.; Cook, Nigel J.; Cliff, John; Ciobanu, Cristiana L.; Huddleston, Adam


    The common sulfide mineral pyrite is abundant throughout sedimentary uranium systems at Pepegoona, Pepegoona West and Pannikan, Lake Eyre Basin, South Australia. Combined chemical, isotopic and microstructural analysis of pyrite indicates variation in fluid composition, sulfur source and precipitation conditions during a protracted mineralization event. The results show the significant role played by pyrite as a metal scavenger and monitor of fluid changes in low-temperature hydrothermal systems. In-situ micrometer-scale sulfur isotope analyses of pyrite demonstrated broad-scale isotopic heterogeneity (δ34S = -43.9 to +32.4‰VCDT), indicative of complex, multi-faceted pyrite evolution, and sulfur derived from more than a single source. Preserved textures support this assertion and indicate a genetic model involving more than one phase of pyrite formation. Authigenic pyrite underwent prolonged evolution and recrystallization, evidenced by a genetic relationship between archetypal framboidal aggregates and pyrite euhedra. Secondary hydrothermal pyrite commonly displays hyper-enrichment of several trace elements (Mn, Co, Ni, As, Se, Mo, Sb, W and Tl) in ore-bearing horizons. Hydrothermal fluids of magmatic and meteoric origins supplied metals to the system but the geochemical signature of pyrite suggests a dominantly granitic source and also the influence of mafic rock types. Irregular variation in δ34S, coupled with oscillatory trace element zonation in secondary pyrite, is interpreted in terms of continuous variations in fluid composition and cycles of diagenetic recrystallization. A late-stage oxidizing fluid may have mobilized selenium from pre-existing pyrite. Subsequent restoration of reduced conditions within the aquifer caused ongoing pyrite re-crystallization and precipitation of selenium as native selenium. These results provide the first qualitative constraints on the formation mechanisms of the uranium deposits at Beverley North. Insights into

  14. Morphology, origin and infrared microthermometry of fluid inclusions in pyrite from the Radka epithermal copper deposit, Srednogorie zone, Bulgaria (United States)

    Kouzmanov, Kalin; Bailly, Laurent; Ramboz, Claire; Rouer, Olivier; Bény, Jean-Michel


    Pyrite samples from the Radka epithermal, replacement type, volcanic rock-hosted copper deposit, Bulgaria, have been studied using near-infrared (IR) microscopy. Two generations of pyrite based on their textures, composition and behaviour in IR light can be distinguished. Electron microprobe analyses, X-ray elemental mapping and Fourier transform infrared spectroscopy were used to study the relationship between crystal zoning, trace element contents and IR transmittance of pyrite. The observed crystal zoning is related to variable arsenic contents in massive fine-grained and colloform pyrite from the early pyrite-quartz assemblage, and cobalt contents in pyrite crystals from the late quartz-pyrite vein assemblage. There is a negative correlation between trace element content and IR transmittance of pyrite. The IR transparency of pyrite is thus a sensitive indicator of changes in trace element concentrations. Fluid inclusions have only been found in the second pyrite generation. Scanning electron microscopy observations on open fluid inclusion cavities permitted the crystallographic features of vacuoles to be determined. A characteristic feature of primary fluid inclusions in pyrite is a negative crystal habit, shaped mainly by {100}, {111} and {210}. This complicated polyhedral morphology is the reason for the observed opacity of some isometric primary inclusions. Secondary fluid inclusion morphology depends on the nature of the surface of the healed fracture. Recognition of the primary or secondary origin of fluid inclusions is enhanced by using crystallographically oriented sections. Microthermometric measurements of primary inclusions indicate that the second pyrite generation was deposited at maximum P-T conditions of 400 °C and 430 bar and from a fluid of low bulk salinity (3.5-4.6 wt%), possibly KCl-dominant. There are large ranges for homogenisation temperatures in secondary inclusions because of necking-down processes. Decrepitation features of some of

  15. Synchrotron Spectroscopic Studies of the Reaction of Cleaved Pyrite ( {FeS2}) Surfaces with Cr(VI) Solutions (United States)

    Doyle, C. S.; Kendelewicz, T.; Bostick, B. C.; Brown, G. E.


    Pyrite is one of the most common sulfide ores, and the separation of valuable sulfide minerals from it has been an area of considerable interest for a long time. This extraction has led to a large quantity of pyrite waste, typically remaining in mine tailings piles which can interact with oxygen and surface water. The oxidation of pyrite under these conditions leads to the commonly known environmental problem of acid mine drainage, with acidification of surface waters, and the release of potentially toxic metals remaining within the pyrite matrix. A microscopic understanding of this oxidation process is extremely important and has been the aim of a number of studies. We apply the methods of synchrotron based surface science to this problem, utilizing surface sensitive photoemission and X-ray absorption spectroscopy to study the surface species present on the pyrite surface at the initial stages of oxidation. We have reacted pyrite surfaces with solutions containing chromate. Chromium exists in solution in two principal valence states, trivalent Cr(III) and hexavalent Cr(VI). Hexavalent chromium is itself considered an environmental problem due to its high toxicity and solubility, and thus mobility, whilst trivalent chromium is much less toxic and relatively insoluble. Hexavalent chromate is a strong oxidizing agent, and will react rapidly with the pyrite surface allowing the identification of oxidized iron and sulfur surface species. The possibility of using pyrite as a means of reducing chromate, and at the same time using chromate to passivate the pyrite surface to further oxidation through the buildup of a non-reactive iron-chromium (oxy)hydroxide layer will be investigated. The work was performed on rods cut from a natural pyrite single crystal from the Logroño region of Spain. The rods were then fractured over a reaction vessel, producing a fresh (100) surface for each experiment. The pyrite surfaces were reacted with 50 μM Cr(VI) solutions for 5 minutes at

  16. Pyritization processes and greigite formation in the advancing sulfidization front in the Upper Pleistocene sediments of the Black Sea

    DEFF Research Database (Denmark)

    Neretin, LN; Bottcher, ME; Jørgensen, BB


    Pyritization in late Pleistocene sediments of the Black Sea is driven by sulfide formed during anaerobic methane oxidation. A sulfidization front is formed by the opposing gradients of sulfide and dissolved iron. The sulfidization processes are controlled by the diffusion flux of sulfide from above...... and by the solid reactive iron content. Two processes of diffusion-limited pyrite formation were identified. The first process includes pyrite precipitation with the accumulation of iron sulfide precursors with the average chemical composition of FeSn (n = 1.10-1.29), including greigite. Elemental sulfur...... and polysulfides, formed from H,S by a reductive dissolution of Fe(Ill)-containing minerals, serve as intermediates to convert iron sulfides into pyrite. In the second process, a "direct" pyrite precipitation occurs through prolonged exposure of iron-containing minerals to dissolved sulfide. Methane-driven sulfate...

  17. Preparation of natural pyrite nanoparticles by high energy planetary ball milling as a nanocatalyst for heterogeneous Fenton process

    Energy Technology Data Exchange (ETDEWEB)

    Fathinia, Siavash [Department of Mining Engineering, Faculty of Engineering and Technology, Imam Khomeini International University, Qazvin (Iran, Islamic Republic of); Research Laboratory of Advanced Water and Wastewater Treatment Processes, Department of Applied Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz (Iran, Islamic Republic of); Fathinia, Mehrangiz [Research Laboratory of Advanced Water and Wastewater Treatment Processes, Department of Applied Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz (Iran, Islamic Republic of); Rahmani, Ali Akbar [Department of Mining Engineering, Faculty of Engineering and Technology, Imam Khomeini International University, Qazvin (Iran, Islamic Republic of); Khataee, Alireza, E-mail: [Research Laboratory of Advanced Water and Wastewater Treatment Processes, Department of Applied Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz (Iran, Islamic Republic of)


    Graphical abstract: - Highlights: • Pyrite nanoparticles were successfully produced by planetary ball milling process. • The physical and chemical properties of pyrite nanoparticles were fully examined. • The degradation of AO7 was notably enhanced by pyrite nanoparticles Fenton system. • The influences of basic operational parameters were investigated using CCD. - Abstract: In the present study pyrite nanoparticles were prepared by high energy mechanical ball milling utilizing a planetary ball mill. Various pyrite samples were produced by changing the milling time from 2 h to 6 h, in the constant milling speed of 320 rpm. X-ray diffraction (XRD), scanning electron microscopy (SEM) linked with energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FT-IR) analysis and Brunauer–Emmett–Teller (BET) were performed to explain the characteristics of primary (unmilled) and milled pyrite samples. The average particle size distribution of the produced pyrite during 6 h milling was found to be between 20 nm and 100 nm. The catalytic performance of the different pyrite samples was examined in the heterogeneous Fenton process for degradation of C.I. Acid Orange 7 (AO7) solution. Results showed that the decolorization efficiency of AO7 in the presence of 6 h-milled pyrite sample was the highest. The impact of key parameters on the degradation efficiency of AO7 by pyrite nanoparticles catalyzed Fenton process was modeled using central composite design (CCD). Accordingly, the maximum removal efficiency of 96.30% was achieved at initial AO7 concentration of 16 mg/L, H{sub 2}O{sub 2} concentration of 5 mmol/L, catalyst amount of 0.5 g/L and reaction time of 25 min.


    Energy Technology Data Exchange (ETDEWEB)

    Daniel Tao


    The objective of this research program is to develop a novel integrated process to eliminate millions of tons of gypsum and pyrite wastes generated annually by the U.S. energy industries and reduce the emission of millions of tons of greenhouse gas carbon dioxide. This was accomplished by converting gypsum and pyrite wastes to marketable products such as lime, direct reduced iron (DRI), and sulfur products and obviating the need to calcine millions of tons of limestone for use in utility scrubbers. Specific objectives included: (1) Develop a novel, integrated process for utilizing two major wastes generated by mining and energy industries to produce lime for recycling and other marketable products. (2) Study individual chemical reactions involved in pyrite decomposition, DRI production, and Muller-Kuhne process for lime regeneration to determine optimum process variables such as temperature, time, and reactant composition. (3) Investigate techniques for effective concentration of pyrite from tailing waste and methods for effective separation of DRI from calcium sulfide.

  19. Pyrite nanoparticles as a Fenton-like reagent for in situ remediation of organic pollutants

    Directory of Open Access Journals (Sweden)

    Carolina Gil-Lozano


    Full Text Available The Fenton reaction is the most widely used advanced oxidation process (AOP for wastewater treatment. This study reports on the use of pyrite nanoparticles and microparticles as Fenton reagents for the oxidative degradation of copper phthalocyanine (CuPc as a representative contaminant. Upon oxidative dissolution in water, pyrite (FeS2 particles can generate H2O2 at their surface while simultaneously promoting recycling of Fe3+ into Fe2+ and vice versa. Pyrite nanoparticles were synthesized by the hot injection method. The use of a high concentration of precursors gave individual nanoparticles (diameter: 20 nm with broader crystallinity at the outer interfaces, providing a greater number of surface defects, which is advantageous for generating H2O2. Batch reactions were run to monitor the kinetics of CuPc degradation in real time and the amount of H2O2. A markedly greater degradation of CuPc was achieved with nanoparticles as compared to microparticles: at low loadings (0.08 mg/L and 20 h reaction time, the former enabled 60% CuPc removal, whereas the latter enabled only 7% removal. These results confirm that the use of low concentrations of synthetic nanoparticles can be a cost effective alternative to conventional Fenton procedures for use in wastewater treatment, avoiding the potential risks caused by the release of heavy metals upon dissolution of natural pyrites.

  20. Pyrite oxidation in saturated and Unsaturated Porous Media Flow: AComparison of alternative mathematical modeling approaches

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tianfu; White, Stephen P.; Pruess, Karsten


    Pyrite (FeS{sub 2}) is one of the most common naturally occurring minerals that is present in many subsurface environments. It plays an important role in the genesis of enriched ore deposits through weathering reactions, is the most abundant sulfide mineral in many mine tailings, and is the primary source of acid drainage from mines and waste rock piles. The pyrite oxidation reaction serves as a prototype for oxidative weathering processes with broad significance for geoscientific, engineering, and environmental applications. Mathematical modeling of these processes is extremely challenging because aqueous concentrations of key species vary over an enormous range, oxygen inventory and supply are typically small in comparison to pyrite inventory, and chemical reactions are complex, involving kinetic control and microbial catalysis. We present the mathematical formulation of a general multi-phase advective-diffusive reactive transport model for redox processes. Two alternative implementations were made in the TOUGHREACT and TOUGH2-CHEM simulation codes which use sequential iteration and simultaneous solution, respectively. The simulators are applied to reactive consumption of pyrite in (1) saturated flow of oxidizing water, and (2) saturated-unsaturated flow in which oxygen transport occurs in both aqueous and gas phases. Geochemical evolutions predicted from different process models are compared, and issues of numerical accuracy and efficiency are discussed.

  1. The Influence of Pyrite on the Solubility of Minjingu and Panda ...

    African Journals Online (AJOL)

    with pyrite also resulted into high amounts of A I and Mn being released in ... low P:S ratios this point was attained earlier than those with high P:S ratios. ..... tribution of ST AMICO staff who pro- ... maize- wheat rotation on submontarie soils.

  2. Comment on "Abiotic pyrite formation produces a large Fe isotope fractionation". (United States)

    Czaja, Andrew D; Johnson, Clark M; Yamaguchi, Kosei E; Beard, Brian L


    Guilbaud et al. (Reports, 24 June 2011, p. 1548) suggest that the geologic record of Fe isotope fractionation can be explained by abiological precipitation of pyrite. We argue that a detailed understanding of the depositional setting, mineralogy, and geologic history of Precambrian sedimentary rocks indicates that the Fe isotope record dominantly reflects biological fractionations and Fe redox processes.

  3. Degradation of anthraquinone dye reactive blue 4 in pyrite ash catalyzed Fenton reaction. (United States)

    Becelic-Tomin, Milena; Dalmacija, Bozo; Rajic, Ljiljana; Tomasevic, Dragana; Kerkez, Djurdja; Watson, Malcolm; Prica, Miljana


    Pyrite ash (PA) is created by burning pyrite in the chemical production of sulphuric acid. The high concentration of iron oxide, mostly hematite, present in pyrite ash, gives the basis for its application as a source of catalytic iron in a modified Fenton process for anthraquinone dye reactive blue 4 (RB4) degradation. The effect of various operating variables such as catalyst and oxidant concentration, initial pH and RB4 concentration on the abatement of total organic carbon, and dye has been assessed in this study. Here we show that degradation of RB4 in the modified Fenton reaction was efficient under the following conditions: pH=2.5; [PA]0=0.2 g L(-1); [H2O2]0=5 mM and initial RB4 concentration up to 100 mg L(-1). The pyrite ash Fenton reaction can overcome limitations observed from the classic Fenton reaction, such as the early termination of the Fenton reaction. Metal (Pb, Zn, and Cu) content of the solution after the process suggests that an additional treatment step is necessary to remove the remaining metals from the water. These results provide basic knowledge to better understand the modified, heterogeneous Fenton process and apply the PA Fenton reaction for the treatment of wastewaters which contains anthraquinone dyes.

  4. Influence of the sulfur species reactivity on biofilm conformation during pyrite colonization by Acidithiobacillus thiooxidans. (United States)

    Lara, René H; García-Meza, J Viridiana; Cruz, Roel; Valdez-Pérez, Donato; González, Ignacio


    Massive pyrite (FeS₂) electrodes were potentiostatically modified by means of variable oxidation pulse to induce formation of diverse surface sulfur species (S(n)²⁻, S⁰). The evolution of reactivity of the resulting surfaces considers transition from passive (e.g., Fe(1-x )S₂) to active sulfur species (e.g., Fe(1-x )S(2-y ), S⁰). Selected modified pyrite surfaces were incubated with cells of sulfur-oxidizing Acidithiobacillus thiooxidans for 24 h in a specific culture medium (pH 2). Abiotic control experiments were also performed to compare chemical and biological oxidation. After incubation, the attached cells density and their exopolysaccharides were analyzed by confocal laser scanning microscopy (CLMS) and atomic force microscopy (AFM) on bio-oxidized surfaces; additionally, S(n)²⁻/S⁰ speciation was carried out on bio-oxidized and abiotic pyrite surfaces using Raman spectroscopy. Our results indicate an important correlation between the evolution of S(n)²⁻/S⁰ surface species ratio and biofilm formation. Hence, pyrite surfaces with mainly passive-sulfur species were less colonized by A. thiooxidans as compared to surfaces with active sulfur species. These results provide knowledge that may contribute to establishing interfacial conditions that enhance or delay metal sulfide (MS) dissolution, as a function of the biofilm formed by sulfur-oxidizing bacteria.

  5. Pyrite-pyrrhotite intergrowths in calcite marble from Bistriški Vintgar, Slovenia (United States)

    Zavašnik, J.


    Roman marble quarry in Bistrica gorge in southern Pohorje Mt. (north-eastern Slovenia) is situated in a 20 m thick lens of layered marble, at the contact zone between granodiorite and metamorphites. Grey and yellowish non-homogenous calcite marble is heavily included by mica, quartz, feldspars, zoisite, pyrite and amphiboles. In the present research, we have studied numerous pyrite (FeS2) crystals associated with yellowish-bronze non-stoichiometric pyrrhotite (Fe1-xS), not previously reported from this locality. SEM investigation revealed unusual sequence of crystallisation: primary skeletal pyrrhotite matrix is sparsely overgrown by well-crystalline pyrite, both being overgrown by smaller, well-developed hexagonal pyrrhotite crystals of the second generation. With TEM we identify the pyrrhotite as 5T-Fe1-xS phase, where x is about 0.1 and is equivalent to Fe9S10. The pyrite-pyrrhotite coexistence allows us a construction of fO2-pH diagram of stability fields, which reflects geochemical conditions at the time of marble re-crystallisation.

  6. Enhanced Photoresponse of FeS2 Films : The Role of Marcasite–Pyrite Phase Junctions

    NARCIS (Netherlands)

    Wu, Longfei; Dzade, N.Y.; Gao, L.; Scanlon, D. O.; Özturk, Zafer; Hollingsworth, N.; Weckhuysen, B.M.; Hensen, E. J. M.; de Leeuw, Nora H.; Hofmann, J. P.


    The beneficial role of marcasite in iron sulfide-based photo-electrochemical applications is reported for the first time. A spectacular improvement of the photoresponse observed experimentally for mixed pyrite/marcasite-FeS2 films can be ascribed to the presence of p/m phase junctions at the interfa

  7. Microbial Oxidation of Pyrite Coupled to Nitrate Reduction in Anoxic Groundwater Sediment

    DEFF Research Database (Denmark)

    Jørgensen, Christian Juncher; Elberling, Bo; Jacobsen, Ole Stig;


    denitrification process with pyrite as the primary electron donor. The process demonstrates a temperature dependency (Q10) of 1.8 and could be completely inhibited by addition of a bactericide (NaN3). Experimentally determined denitrification rates show that more than 50% of the observed nitrate reduction can...

  8. Degradation of Anthraquinone Dye Reactive Blue 4 in Pyrite Ash Catalyzed Fenton Reaction

    Directory of Open Access Journals (Sweden)

    Milena Becelic-Tomin


    Full Text Available Pyrite ash (PA is created by burning pyrite in the chemical production of sulphuric acid. The high concentration of iron oxide, mostly hematite, present in pyrite ash, gives the basis for its application as a source of catalytic iron in a modified Fenton process for anthraquinone dye reactive blue 4 (RB4 degradation. The effect of various operating variables such as catalyst and oxidant concentration, initial pH and RB4 concentration on the abatement of total organic carbon, and dye has been assessed in this study. Here we show that degradation of RB4 in the modified Fenton reaction was efficient under the following conditions: pH=2.5; [PA]0=0.2 g L−1; [H2O2]0=5 mM and initial RB4 concentration up to 100 mg L−1. The pyrite ash Fenton reaction can overcome limitations observed from the classic Fenton reaction, such as the early termination of the Fenton reaction. Metal (Pb, Zn, and Cu content of the solution after the process suggests that an additional treatment step is necessary to remove the remaining metals from the water. These results provide basic knowledge to better understand the modified, heterogeneous Fenton process and apply the PA Fenton reaction for the treatment of wastewaters which contains anthraquinone dyes.

  9. Pyrite oxidation in unsaturated aquifer sediments. Reaction stoichiometry and rate of oxidation

    DEFF Research Database (Denmark)

    Andersen, Martin Søgaard; Larsen, Flemming; Postma, Diederik Jan


    the reaction stoichiometry and partitioning of gases between the solution and the gas phase. Pyrite oxidation with concurrent calcite dissolution was found to be consistent with the experimental data while organic carbon oxidation was not. The reaction involves changes in the total volume of the gas phase...

  10. Re-Os isotope geochemistry of three Chinese chondrites

    Institute of Scientific and Technical Information of China (English)

    ZHI XiaChen; QIN Xie; SHI RenDeng; HONG JiAn


    Three Chinese ordinary chondrites, including Jilin (H5), Boxian (LL3.8) and Lujiang (LL6), have been studied for their Re and Os abundances and Os isotopic composition in whole-chondrite samples, separated magnetic and nonmagnetic fractions, and nodules.The results indicate that the Re and Os abundances of the whole-chondrite samples are in the ranges of corresponding H- and LL-Groups, respectively.The Re and Os abundances of magnetic fraction from Boxian and Lujiang are within the range of high-Os IIAB and IIIAB irons, whereas those of nonmagnetic fractions of Boxian and Lujiang are lower than the whole-chondrite values.The Re and Os abundances of nodules in Jilin are in the range of the LL-Group.187Re/188Os and 187Os/188Os ratios of the three whole chondrites are in the range of ordinary chondrites which locate around the isochron of IIAB+IIIAB irons.187Re/188Os and 187Os/188Os ratios of the magnetic and nonmagnetic fractions from Boxian have a larger difference.The nonmagnetic fraction of Lujiang may contain a recent addition of Re, which causes deviation of the 187Re/188Os ratio from the irons isochron.The Re and Os abundances of nodules in Jilin are lower than those of the whole-chondrite, but their 187Os/188Os ratios are higher than that of the whole chondrite.

  11. SHRIMP zircon U-Pb and Re-Os dating of No. 10 intrusive body and associated ores in Pobei mafic-ultramafic belt of Xinjiang and its significance%新疆坡北基性-超基性岩带10号岩体SHRIMPU-Pb和矿石Re-Os同位素定年及其意义

    Institute of Scientific and Technical Information of China (English)

    李华芹; 梅玉萍; 屈文俊; 蔡红; 杜国民


    Located in Beishan rift in the northeastern part of Tarim plate, the Pobei No. 10 mafic-ultramafic body in-truded into Early Carboniferous Hongliuyuan Formation. It is large in size and well differentiated, thus serving as one of the most important intrusive bodies in search for copper-nickel sulfides. According to its emplacement strata, it was previously thought that this intrusive body was formed in Late Carboniferous-Early Permian. The uthors performed dating by using such techniques as zircon U-Pb, disseminated ores Re-Os and Sr-Nd isotopic tracer with the purpose of systematic determination of the magmatie and mineralization ages, on such a basis, discussed the metallogenic significance of systematic differences between the ages dated by different isotopic sys-tems. Radiometric dating of the gabbro from the Pobei No. 10 mafic-ultramafie body yielded rather scattered zir-con age information, but obtained a main body zircon SHRIMP U-Pb age of (289± 13)Ma(95 % confidence, MSWD=4.9, n = 8), which is interpreted as the formation age of the host intrusive. The disseminated ores give an apparent Re-Os isochron age of (413 ± 20) Ma with an initial 187Os/188Os ratio of (0.226 ± 0.032). However, it is found that the apparent Re-Os isochron ages of disseminated ores are older than both the forma-tion age of the host intrusions and the ages of Pobei No. 10 mafic-ultramafic emplacement strata, which indicates that the apparent Re-Os isochron ages of disseminated ores are not reliable. It is suggested that the Pobei No. 10 mafic-ultramafic body and the deposit were formed at about 280 Ma ago. Because of heterogeneity in initial ~(187)Os/~(188)Os ratios of disseminated ores caused by crust contamination, the apparent dates older than the true age were obtained. Cu-Ni mineraliztion shows a close time-space relationship with the mafic-ultramafic intrusive body, implying a product of magmatic liquation. It is therefore concluded that the intrusion of Pobei No. 10 mafic

  12. Pyrite (FeS 2) oxidation: A sub-micron synchrotron investigation of the initial steps (United States)

    Chandra, Anand P.; Gerson, Andrea R.


    Pyrite is an environmentally significant mineral being the major contributor to acid rock drainage. Synchrotron based SPEM (scanning photoelectron microscopy) and micro-XPS (X-ray photoelectron spectroscopy) have been used to characterise fresh and oxidised pyrite (FeS 2) with a view to understanding the initial oxidation steps that take place during natural weathering processes. Localised regions of the pyrite surface containing Fe species of reduced coordination have been found to play a critical role. Such sites not only initiate the oxidation process but also facilitate the formation of highly reactive hydroxyl radical species, which then lead the S oxidation process. Four different S species are found to be present on fresh fractured pyrite surfaces: S 22-(bulk) (4-fold coordination), S 22-(surface) (3-fold coordination), S 2- and S 0/S n2- (metal deficient sulfide and polysulfide respectively). These species were found to be heterogeneously distributed on the fractured pyrite surface. Both O 2 and H 2O gases are needed for effective oxidation of the pyrite surface. The process is initiated when O 2 dissociatively and H 2O molecularly adsorb onto the surface Fe sites where high dangling bond densities exist. H 2O may then dissociate to produce rad OH radicals. The adsorption of these species leads to the formation of Fe-oxy species prior to the formation of sulfoxy species. Evidence suggests that Fe-O bonds form prior to Fe-OH bonds. S oxidation occurs through interactions of rad OH radicals formed at the Fe sites, with formation of SO 42- occurring via S 2O 32-/SO 32- intermediates. The pyrite oxidation process is electrochemical in nature and was found to occur in patches, where site specific adsorption of O 2 and H 2O has occurred. Fe and S oxidation was found to occur within the same area of oxidation probably in atomic scale proximity. Furthermore, the O in SO 42- arises largely from H 2O; however, depending on the surface history, SO 42- formed early in

  13. Nanoscale analysis of pyritized microfossils reveals differential heterotrophic consumption in the ~1.9-Ga Gunflint chert. (United States)

    Wacey, David; McLoughlin, Nicola; Kilburn, Matt R; Saunders, Martin; Cliff, John B; Kong, Charlie; Barley, Mark E; Brasier, Martin D


    The 1.88-Ga Gunflint biota is one of the most famous Precambrian microfossil lagerstätten and provides a key record of the biosphere at a time of changing oceanic redox structure and chemistry. Here, we report on pyritized replicas of the iconic autotrophic Gunflintia-Huroniospora microfossil assemblage from the Schreiber Locality, Canada, that help capture a view through multiple trophic levels in a Paleoproterozoic ecosystem. Nanoscale analysis of pyritic Gunflintia (sheaths) and Huroniospora (cysts) reveals differing relic carbon and nitrogen distributions caused by contrasting spectra of decay and pyritization between taxa, reflecting in part their primary organic compositions. In situ sulfur isotope measurements from individual microfossils (δ(34)S(V-CDT) +6.7‰ to +21.5‰) show that pyritization was mediated by sulfate-reducing microbes within sediment pore waters whose sulfate ion concentrations rapidly became depleted, owing to occlusion of pore space by coeval silicification. Three-dimensional nanotomography reveals additional pyritized biomaterial, including hollow, cellular epibionts and extracellular polymeric substances, showing a preference for attachment to Gunflintia over Huroniospora and interpreted as components of a saprophytic heterotrophic, decomposing community. This work also extends the record of remarkable biological preservation in pyrite back to the Paleoproterozoic and provides criteria to assess the authenticity of even older pyritized microstructures that may represent some of the earliest evidence for life on our planet.

  14. Paleogene continental margin truncation in southwestern Mexico: Geochronological evidence (United States)

    Schaaf, Peter; MoráN-Zenteno, Dante; HernáNdez-Bernal, Maria Del Sol; SolíS-Pichardo, Gabriela; Tolson, Gustavo; KöHler, Hermann


    The reasons for, and mechanisms of, continental margin truncation in SW Mexico where Mesozoic-Cenozoic plutons are situated directly on the Pacific coast, are not yet well understood. Large-scale dextral and/or sinistral displacements of the continental margin terranes, now forming parts of Baja California or the Chortis block, have been proposed. The well-defined along-coast NW-SE decreasing granitoid intrusion age trend (˜1.2 cm/yr in the 100 Ma-40 Ma time interval) between Puerto Vallarta and Zihuatanejo is interpreted by us to be a geometric artifact of oblique continental margin truncation rather than the consequence of a sinistral offset of the Chortis block from those latitudes toward the SE. Changes in the dip and velocity of the NNW-SSE trending Cretaceous-Tertiary subduction zone resulted in a landward migration of the magmatic arc. Taking into account certain stratigraphic affinities of Chortis and the Oaxaca and Mixteca terranes, together with the known displacement rates along the North America-Caribbean Plate boundary, the northwesternmost paleoposition of the Chortis block with respect to SW Mexico was near Zihuatanejo. In contrast, between Zihuatanejo and the Isthmus of Tehuantepec, the cessation of the Tertiary magmatism decreased more rapidly (˜7.7 cm/yr), although the trend is not so obvious. Starting in the late Eocene, Chortis moved about 1100 km to the SE along a transform boundary associated with the opening of the Cayman Trough. Based on our geochronological data and structural relationships between mylonite zones and plutons in the Acapulco-Tehuantepec area, we propose an approximately 650 km SE movement of Chortis from about 40-25 Ma, with a velocity of 6.5-4.3 cm/yr. Since this is considerably slower than the decreasing age trend obtained by us using the geochronological data, we consider batholith formation in this segment to predate and postdate the offshore passage of the North America-Farallon-Caribbean triple junction. Geological

  15. Attenuation of pyrite oxidation with a fly ash pre-barrier: Reactive transport modelling of column experiments

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Lopez, R.; Cama, J.; Nieto, J.M.; Ayora, C.; Saaltink, M.W. [University of Huelva, Huelva (Spain). Dept. of Geology


    Conventional permeable reactive barriers (PRBs) for passive treatment of groundwater contaminated by acid mine drainage (AMD) use limestone as reactive material that neutralizes water acidity. However, the limestone-alkalinity potential ceases as inevitable precipitation of secondary metal-phases on grain surfaces occurs, limiting its efficiency. In the present study, fly ash derived from coal combustion is investigated as an alternative alkalinity generating material for the passive treatment of AMD using solution-saturated column experiments. Unlike conventional systems, the utilization of fly ash in a pre-barrier to intercept the non-polluted recharge water before this water reacts with pyrite-rich wastes is proposed. Chemical variation in the columns was interpreted with the reactive transport code RETRASO. In parallel, kinetics of fly ash dissolution at alkaline pH were studied using flow-through experiments and incorporated into the model. In a saturated column filled solely with pyritic sludge-quartz sand (1: 10), oxidation took place at acidic conditions (pH 3.7). According to SO{sub 4}{sup 2-} release and pH, pyrite dissolution occurred favourably in the solution-saturated porous medium until dissolved O{sub 2} was totally consumed. In a second saturated column, pyrite oxidation took place at alkaline conditions (pH 10.45) as acidity was neutralized by fly ash dissolution in a previous level. At this pH Fe release from pyrite dissolution was immediately depleted as Fe-oxy(hydroxide) phases that precipitated on the pyrite grains, forming Fe-coatings (microencapsulation). With time, pyrite microencapsulation inhibited oxidation in practically 97% of the pyritic sludge. Rapid pyrite-surface passivation decreased its reactivity, preventing AMD production in the relatively short term.

  16. Arsenic chemistry with sulfide, pyrite, zero-valent iron, and magnetite (United States)

    Sun, Fenglong

    The aim of this thesis is to study the immobilization reactions of arsenic in water. Since compounds containing iron or sulfide are common in most natural and engineered systems, the research focused on the redox reactions and adsorption of arsenic with sulfide, pyrite, zero-valent iron (ZVI), and magnetite which were studied through wet chemistry methods and spectroscopic techniques. The kinetic and thermodynamic information of the reactions of As(V) with S(-II), As(V)/As(III) with pyrite and surface-oxidized pyrite, As(V) with ZVI and acid-treated ZVI, As(III) with magnetite was used to identify mechanisms. The necessity to maintain strictly anoxic conditions was emphasized for the study of arsenic redox chemistry with sulfides and ZVI. The major findings of this research can be stated as follows. First, dissolved sulfide reduced As(V) to lower valences to form a yellow precipitate at acidic pH. The reaction involved the formation of thioarsenic intermediate species. Dissolved O2, granular activated carbon (GAC) and dissolved Fe(II) inhibited the removal of As(V) by sulfide. Elemental sulfur catalyzed the reduction of As(V) by sulfide, which implied the possible benefit of using sulfur-loaded GAC for arsenic removal. Possible reaction mechanisms were discussed. Second, As(III) adsorbed on pristine pyrite over a broader pH range than on surface-oxidized pyrite, while As(V) adsorbed over a narrower pH range with pristine pyrite. As(V) was completely reduced to As(III) on pristine pyrite at acidic pH but not at higher pH. The reduction was first-order with respect to As(V). As(V) was not reduced on surface-oxidized pyrite at pH = 4--11. The different behaviors of As(V) and As(III) on pristine and surface oxidized pyrite determines the toxicity and mobility of arsenic under oxic/anoxic environments. Third, commercial ZVI reduced As(V) to As(III) at low pH (treated ZVI reduced As(V) to As(0), indicated by wet chemical analyses and by XANES/EXAFS, which could result in

  17. Existing forms of REE in gold-bearing pyrite of the Jinshan gold deposit,Jiangxi Province,China

    Institute of Scientific and Technical Information of China (English)

    毛光周; 华仁民; 高剑峰; 李伟强; 赵葵东; 龙光明; 陆慧娟


    Rare earth element(REE) is widely used in various fields of geology.Study of the existing forms of REE in geological objects is a necessity for us to solve geological problems related with REE.This paper tried to make it clear the existing forms of REE in gold-bearing pyrite in Jinshan gold deposit by stepwise dissolution test with ICP-MS analysis.Results showed that content of REE in fluid-inclusions of gold-bearing pyrite was very low,which only took about 0.07%-0.70% of the ΣREE,and that of pyrite phase ...

  18. The origin of copiapite from chlorite pyritic schist (Wiesciszowice, Lower Silesia, Poland) in the light of Moessbauer analysis

    Energy Technology Data Exchange (ETDEWEB)

    Adamczyk, Z., E-mail: [Silesian University of Technology, Institute of Applied Geology (Poland); Komraus, J. L., E-mail: [University of Silesia, Institute of Physics (Poland)


    This work presents the results of the analysis of copiapite, formed from weathering and oxidation of pyrite in pyritic schist from Wiesciszowice, Lower Silesia (Poland). The pure phase of copiapite was found in secondary minerals after pyrite and identified by optical microscopy, XRD and Moessbauer spectroscopy. In the analyzed copiapite major cations appear to be Fe{sup 2+} and Fe{sup 3+}. Some Fe{sup 3+} is substituted by other cations, mainly Al{sup 3+}. Al{sup 3+} probably comes from leaching of chlorite from which hydrated sulphates of iron, mainly szomolnokite, form followed by hydrated sulphates fibroferrite, which is replaced by copiapite.


    Institute of Scientific and Technical Information of China (English)

    章新喜; 陈清加


    The effect of removing pyrite and ash from fine coal with electrostatic separator is determined by the electric property of coal, the distribution of corona ion and electrostatic field, and the disperse and even feed. The dielectric constant of coal and mineral matter is studied in this paper and the amendment has been made to survey theory. The oscillogram is adopted to study the distribution of corona ion and electrostatic field. The paper details the study of remoing pyrite and ash from fine coal, and the test results demonstrate the high efficiency of removing pyrite and ash with electrostatic separator.

  20. Amino acid geochronology of raised beaches in south west Britain (United States)

    Bowen, D. Q.; Sykes, G. A.; Reeves (nee Henry), Alayne; Miller, G. H.; Andrews, J. T.; Brew, J. S.; Hare, P. E.

    Based on (1) the epimerization of L:isoleucine to D:alloisoleucine ( {D}/{L} ratios) in Patella vulgata, Littorina littorea, L. littoralis, L. saxatilis, Littorina species and Nucella lapillus from raised beaches in south west Britain, (2) statistical analysis of the {D}/{L} ratios, and (3) lithostratigraphic and geomorphic evaluation, three ( {D}/{L}) Stages are proposed. The {D}/{L} ratios for all the species measured are converted to a Patella vulgata standard. The three ( {D}/{L}) Stages are: (1) The Minchin Hole ( {D}/{L}) Stage, {D}/{L} ratios 0.175 ± 0.014, defined at a stratotype in Minchin Hole Cave, Gower, Wales. (2) A provisionally defined, but as yet, unamed ( {D}/{L}) Stage, because of the current unavailability of a suitable stratotype, with {D}/{L} ratios of 0.135 ± 0.014 (3) The Pennard ( {D}/{L}) Stage, {D}/{L} ratios 0.105 ± 0.016, defined at a stratotype in Minchin Hole Cave, Gower, Wales. Two geochronological models of the three high sea-level events representing the {D}/{L} Stages are constrained by uranium-series age determinations on stalagmite interbedded with marine beds in Minchin Hole and Bacon Hole Caves, Gower, Wales. A potential 'fixed point' in model evaluation is an age determination which is equivalent to Oxygen Isotope Sub-stage 5e (122 ka). The two models are:

  1. On the origin of framboidal pyrite in sediments of the Suakin Deep (Red Sea)Sur l'origine de la pyrite framboïdale dans les sédiments de la fosse Suakin (mer Rouge) (United States)

    Pierret, Marie-Claire; Blanc, Gérard; Clauer, Norbert


    Suakin Deep is one of the southern depressions of the Red Sea, with sediments containing up to 20 % of pyrite. Although metalliferous sediments result from hydrothermal activity in most deeps, those of Suakin have different characteristics. Pyrite is framboïdal and the REE patterns of its sediments are similar to those of biodetrital sediments. The sediments seem to be of biodetritic origin and to have undergone diagenetic changes without hydrothermal activity.

  2. Isotope geochronology of Dapingzhang spilite-keratophyre formation in Yunnan Province and its geological significance

    Institute of Scientific and Technical Information of China (English)

    钟宏; 胡瑞忠; 叶造军; 涂光炽


    On the basis of the geological field investigations and isotope geochronological studies the Sm-Nd isochron age (513 Ma?0 Ma), Rb-Sr isochron age (511 Ma? Ma) and K-Ar age (312-317 Ma) of the Dapingzhang spilite-keratophyre formation in Yunnan Province are presented. From these geochronological data it is evidenced that this suite of volcanic rocks was formed in the Cambrian and the parent magma was derived from a depleted mantle, which was influenced by crustal contamination and/or seawater hydrothermal alteration. During the Late Carboniferous the volcanic rocks experienced relatively strong geological reworking. This study provides geochronological evidence for the occurrence of Cambrian volcanic rocks in the Sanjiang (three-river) area.

  3. Isotope geochronology of Dapingzhang spilite-keratophyre formation in Yunnan Province and its geological significance

    Institute of Scientific and Technical Information of China (English)


    On the basis of the geological field investigations and isotope geochronological studies the Sm-Nd isochron age (513 Ma±40 Ma),Rb-Sr isochron age (511 Ma±8 Ma) and K-Ar age (312-317 Ma) of the Dapingzhang spilite-keratophyre formation in Yunnan Province are presented.From these geochronological data it is evidenced that this suite of volcanic rocks was formed in the Cambrian and the parent magma was derived from a depleted mantle,which was influenced by crustal contamination and/or seawater hydrothermal alteration.During the Late Carboniferous the volcanic rocks experienced relatively strong geological reworking.This study provides geochronological evidence for the occurrence of Cambrian volcanic rocks in the Sanjiang (three-river) area.

  4. Biohydrometallurgical process to produce the coagulant ferric sulfate from the pyrite present in coal tailings

    Energy Technology Data Exchange (ETDEWEB)

    Colling, A.V.; Santos Menezes dos, J.C.S.; Silveira, P.S.; Schneider, I.A.H. [South Rio Grande Federal Univ., Porto Alegre (Brazil). Graduate Program in Mining, Metallurgical and Materials Technology Center


    This paper presented details of a biohydrometallurgical study conducted to characterize the production of a ferric sulfate coagulate from pyrite (FeS{sub 2}) contained in coal tailings. Leaching experiments were conducted with coal tailings samples from the Santa Catarina mining site in Brazil. The experiments were conducted for sterile and non-sterile samples, as well as samples inoculated with acidophilic bacteria and acidophilic bacteria with the addition of nutrients. Samples were collected weekly in order to analyze total iron, sulfate, and the amounts of Acidithiobacillus ferroxidans bacteria. An analysis of the samples showed that the pyrite oxidation, iron sulfate production, and quantities of bacteria were higher in the column inoculated with the bacteria and nutrient additions. The samples produced an aqueous solution that was rich in ferric sulfate. Water treatment tests demonstrated that the resulting coagulant is as efficient as conventionally-produced coagulants. 8 refs., 2 tab., 2 figs.

  5. Simulation of electrocatalytic hydrogen production by a bioinspired catalyst anchored to a pyrite electrode. (United States)

    Zipoli, Federico; Car, Roberto; Cohen, Morrel H; Selloni, Annabella


    The possibility of using the active site, the [FeFe](H) cluster, of the bacterial di-iron hydrogenases as a catalyst for hydrogen production from water by electro- or photocatalysis is of current scientific and technological interest. We present here a theoretical study of hydrogen production by a modified [FeFe](H) cluster stably linked to a pyrite electrode immersed in acidified water. We employed state-of-the-art electronic-structure and first-principles molecular-dynamics methods. We found that a stable sulfur link of the cluster to the surface analogous to that linking the cluster to its enzyme environment cannot be made. However, we have discovered a modification of the cluster which does form a stable, tridentate link to the surface. The pyrite electrode readily produces hydrogen from acidified water when functionalized with the modified cluster, which remains stable throughout the hydrogen production cycle.

  6. Pyrite thermochemistry, ash agglomeration, and char fragmentation during pulverized coal combustion. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Akan-Etuk, A.; Diaz, R.; Niksa, S.


    The objective of the present work is to introduce an experimental program that will eventually lead to time-resolved iron ash composition over the technological operating domain. The preceding literature survey suggests two important stipulations on any such experimental program. The first stipulation is that good control must be established over the operating conditions, to accurately quantify their effects. The other is that data must be obtained rapidly, to thoroughly cover the important operating domain. This work presents a series of studies that has characterized the desulfurization of pyrite during the early stages of combustion. An experimental system was established and used to monitor the effects of oxygen, temperature, and residence time on the evolution of condensed phase products of the combustion of pure pyrite. (VC)

  7. Pyrite thermochemistry, ash agglomeration, and char fragmentation during pulverized coal combustion

    Energy Technology Data Exchange (ETDEWEB)

    Akan-Etuk, A.; Diaz, R.; Niksa, S.


    The objective of the present work is to introduce an experimental program that will eventually lead to time-resolved iron ash composition over the technological operating domain. The preceding literature survey suggests two important stipulations on any such experimental program. The first stipulation is that good control must be established over the operating conditions, to accurately quantify their effects. The other is that data must be obtained rapidly, to thoroughly cover the important operating domain. This work presents a series of studies that has characterized the desulfurization of pyrite during the early stages of combustion. An experimental system was established and used to monitor the effects of oxygen, temperature, and residence time on the evolution of condensed phase products of the combustion of pure pyrite. (VC)

  8. Influences of silver sulfide on the bioleaching of chalcopyrite, pyrite and chalcopyrite-containing ore

    Institute of Scientific and Technical Information of China (English)

    胡岳华; 王军; 邱冠周; 王淀佐


    The effects of silver sulfide (Ag2S) on the bioleaching of chalcopyrite and pyrite were investigated in this paper. It has been shown that Ag2S enhanced the yields of bioleaching of chalcopyrite but inhibited the bio-oxidation of pyrite. The addition of Ag2S selectively increased the copper dissolution from the chalcopyrite-containing ores in shake flasks with a recovery of 85.3% compared with 24.3% without Ag2S, while slightly decreased the iron yields from 51% to 41.8%. The copper extraction of the chalcoopyrite-containing waste rock in column leaching charged with 18 kg mass increased up to 21.7% in the presence of Ag2S, while only 3.4% in the absence of the catalyst. The mechanism of Ag2S catalysis could be explained well by the "Mixed potential model".

  9. Preparation of Metallic Iron Powder from Pyrite Cinder by Carbothermic Reduction and Magnetic Separation

    Directory of Open Access Journals (Sweden)

    Hongming Long


    Full Text Available The reduction and magnetic separation procedure of pyrite cinder in the presence of a borax additive was performed for the preparation of reduced powder. The effects of borax dosage, reduction temperature, reduction time and grinding fineness were investigated. The results show that when pyrite cinder briquettes with 5% borax were pre-oxidized at 1050 °C for 10 min, and reduced at 1050 °C for 80 min, with the grinding fineness (<0.44 mm passing 81%, the iron recovery was 91.71% and the iron grade of the magnetic concentrate was 92.98%. In addition, the microstructures of the products were analyzed by optical microscope, scanning electron microscope (SEM, and mineralography, and the products were also studied by the X-ray powder diffraction technique (XRD to investigate the mechanism; the results show that the borax additive was approved as a good additive to improve the separation of iron and gangue.

  10. Factors Influencing Conversion of Pyritic Sulfur in Coal by Microwave Irradiation

    Institute of Scientific and Technical Information of China (English)

    SUI Jian-cai; XU Ming-hou; QIU Ji-hua; CHENG Rong


    The high sulfur coal from southwest of China was used to examine the influence of different factors such as irradiation time, particle size of coal, and leachant (Na2CO3, NaOH and CuCl2.2H2O)on the conversion rate of pyrite to pyrrhotite by microwave irradiation. Single factor experiment was performed firstly, then orthogonal test method was used to explore these factors. The result shows that the optimal treating conditions for the conversion are a treatment time of 3 min, a particle size from 0.086 mm to 0.102 mm, and a favorable leachant of sodium hydroxide. Under these conditions the conversion rate of pyrite can reach 45.7 %.

  11. Preparation of solid polyferric sulfate from pyrite cinders and its structure feature

    Institute of Scientific and Technical Information of China (English)

    郑雅杰; 龚竹青; 陈白珍; 刘立华


    Acid leaching solution was obtained after mixing pyrite cinders with H2SO4, then heating the mixture of pyrite cinders and H2SO4 at 200-300 ℃, leaching the heated mixture with water and filtrating. Polyferric sulfate (PFS) solution was produced by adding suitable amounts of FeSO4*7H2O and NaClO3 into acid leaching solution. By concentrating and drying PFS solution, solid PFS with alkali degree of 6.40%-22.4% was prepared. Fe4.67(SO4)6(OH)2*20H2O in the solid PFS was discovered by XRD analysis. FT-IR spectroscopy shows that the absorption peaks at 3 400 cm-1 and 1 635 cm-1 arise from OH and absorption peaks at 998 cm-1 and 669 cm-1 come from Fe-OH in the solid PFS.

  12. Comparisons of species and coagulation effects of PFS solution and solid PFS from pyrite cinders

    Institute of Scientific and Technical Information of China (English)

    郑雅杰; 龚竹青; 刘立华; 陈白珍


    Pyrite cinder is a kind of solid waste of sulfuric acid industry. After mixing pyrite cinders with sulfuric acid, ferric sulfate was obtained by heating, maturing, dissolving and filtrating. Suitable amounts of FeSO4 * 7H2O and NaClO3 were added into ferric sulfate solution and polyferric sulfate(PFS) solution was produced. Solid PFS was made by concentrating and drying PFS solution. Time-dependent complex colorimetric tests were done while ferron agent reacted with Fe3+ in the solution. The results show that the proportion of transitional low polymeric species and high polymeric species are increased after PFS solution is transferred into solid PFS. It was discovered by jar tests that solid PFS has very good coagulation effects relevant to the increase of transitional lower polymeric species.

  13. Pyrite oxidation in the presence of hematite and alumina: I. Batch leaching experiments and kinetic modeling calculations. (United States)

    Tabelin, Carlito Baltazar; Veerawattananun, Suchol; Ito, Mayumi; Hiroyoshi, Naoki; Igarashi, Toshifumi


    Pyrite is one of the most common and geochemically important sulfide minerals in nature because of its role in the redox recycling of iron (Fe). It is also the primary cause of acid mine drainage (AMD) that is considered as a serious and widespread problem facing the mining and mineral processing industries. In the environment, pyrite oxidation occurs in the presence of ubiquitous metal oxides, but the roles that they play in this process remain largely unknown. This study evaluates the effects of hematite (α-Fe2O3) and alumina (α-Al2O3) on pyrite oxidation by batch-reactor type experiments, surface-sensitive characterization of the oxidation layer and thermodynamic/kinetic modeling calculations. In the presence of hematite, dissolved sulfur (S) concentration dramatically decreased independent of the pH, and the formation of intermediate sulfoxy anionic species on the surface of pyrite was retarded. These results indicate that hematite minimized the overall extent of pyrite oxidation, but the kinetic model could not explain how this suppression occurred. In contrast, pyrite oxidation was enhanced in the alumina suspension as suggested by the higher dissolved S concentration and stronger infrared (IR) absorption bands of surface-bound oxidation products. Based on the kinetic model, alumina enhanced the oxidative dissolution of pyrite because of its strong acid buffering capacity, which increased the suspension pH. The higher pH values increased the oxidation of Fe(2+) to Fe(3+) by dissolved O2 (DO) that enhanced the overall oxidative dissolution kinetics of pyrite. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. High-resolution (SIMS) versus bulk sulfur isotope patterns of pyrite in Proterozoic microbialites with diverse mat textures (United States)

    Gomes, M. L.; Fike, D. A.; Bergmann, K.; Knoll, A. H.


    Sulfur (S) isotope signatures of sedimentary pyrite preserved in marine rocks provide a rich suite of information about changes in biogeochemical cycling associated with the evolution of microbial metabolisms and oxygenation of Earth surface environments. Conventionally, these S isotope records are based on bulk rock measurements. Yet, in modern microbial mat environments, S isotope compositions of sulfide can vary by up to 40‰ over a spatial range of ~ 1 mm. Similar ranges of S isotope variability have been found in Archean pyrite grains using both Secondary Ion Mass Spectrometry and other micro-analytical techniques. These micron-scale patterns have been linked to changes in rates of microbial sulfate reduction and/or sulfide oxidation, isotopic distillation of the sulfate reservoir due to microbial sulfate reduction, and post-depositional alteration. Fine-scale mapping of S isotope compositions of pyrite can thus be used to differentiate primary environmental signals from post-depositional overprinting - improving our understanding of both. Here, we examine micron-scale S isotope patterns of pyrite in microbialites from the Mesoproterozoic-Neoproterozoic Sukhaya Tunguska Formation and Neoproterozoic Draken Formation in order to explore S isotope variability associated with different mat textures and pyrite grain morphologies. A primary goal is to link modern observations of how sulfide spatial isotope distributions reflect active microbial communities present at given depths in the mats to ancient processes driving fine-sale pyrite variability in microbialites. We find large (up to 60‰) S isotope variability within a spatial range of less than 2.5cm. The micron-scale S isotope measurements converge around the S isotope composition of pyrite extracted from bulk samples of the same microbialites. These micron-scale pyrite S isotope patterns have the potential to reveal important information about ancient biogeochemical cycling in Proterozoic mat environments

  15. Dependence of reaction rate of pyrite oxidation on temperature, pH and oxidant concentration

    Institute of Scientific and Technical Information of China (English)

    LU; Long; WANG; Rucheng; XUE; Jiyue; CHEN; Fanrong; CHEN; J


    The kinetic sstudy of pyrite oxidation was performed in a series of experiments by a mixed flow reactor. The release rates of Fe(II) are in the order of 3.22×10-9-5.51×10-7 mol·m-2·s-1 at temperature (T ) 25 to 44℃, initial pH (pH )1.4 to 2.7, and initial Fe(III) concentration ([Fe(III)]I) 10-5 to 5×10-3 mol·kg-1. The release rate of Fe(II) increased with increasing T or/and pH or/and [Fe(III)]I in the above range. The rate law and activation energy of pyrite oxidation were derived by statistical analyses of Rfe(II) vs. [Fe(III)]I, Rfe(II) vs. pH and Rfe(II) vs. T, and are given as (1) Rate law: Rfe(II)=104.65e-64.54×103/8.31T[Fe(III)]i0.6./[H+]0.45 ; (2) activation energy: 64.54 ( 8.07 kJ·mol-1. The expression can be applied to more cases (e.g., quantifying the pollutant released from sulfide-rich mining waste and assessing reliable performance of underground repository sites where pyrite acts as an engineered barrier material). Using the rate law derived from this study, the magnitude of the pollutants transferred to secondary phases, soil and water from oxidized pyrite during Jiguanshan mine waste weathering was preliminarily estimated. The estimated magnitude is very high, suggesting that the pile has possibly posed significant impact on the water quality in this region.

  16. Pyrite as a proxy for the identification of former coastal lagoons in semiarid NE Brazil (United States)

    Ferreira, Tiago O.; Nóbrega, Gabriel N.; Albuquerque, Antonia G. B. M.; Sartor, Lucas R.; Gomes, Irlene S.; Artur, Adriana G.; Otero, Xosé L.


    This work aimed to test the suitability of pyrite (FeS2) as a proxy for reconstructing past marine environmental conditions along the semiarid coast of Brazil. Morphological description combined with physicochemical analyses including Fe partitioning were conducted for soil depth profiles (30 and 60 cm depths) at three sites in two contrasting lagoons of the state of Ceará: a suspected former lagoon that would have been transformed into a freshwater "lake" at a site vegetated by Juncus effusus (site P1), and another lagoon with connection to the sea at sites vegetated by J. effusus (site P2) or Portulaca oleracea (site P3). Soil samples were collected in September 2010. Site P3 had more reducing conditions, reaching Eh values of -132 mV in the surface layer (0-10 cm), whereas minimum values for the P1 and P2 sites were +219 and +85 mV, respectively. Lower pyritic Fe values were found at site P1, with a degree of pyritization (DOP) ranging from 10 to 13%. At sites P2 and P3, DOP ranged from 9 to 67% and from 55 to 72%, respectively. These results are consistent with an interruption of tidal channels by eolian dune migration inducing strong changes in the hydrodynamics and physicochemical characteristics (lower salinity, oxidizing conditions) of these sites, causing the dieback of suspected former mangroves and a succession to freshwater marshes with an intermediate salt marsh stage. Together with other physicochemical signatures, pyrite can evidently serve as a useful proxy in tracking environmental changes in such ecotones, with implications for coastal management.

  17. Mineral chemistry and isotope geochemistry of pyrite from the Heilangou gold deposit, Jiaodong Peninsula, Eastern China

    Institute of Scientific and Technical Information of China (English)

    Yutong Yan; Na Zhang; Shengrong Li; Yongsheng Li


    The Heilangou gold deposit is located in the northern QixiaePenglai gold belt, which is one amongst the three large gold belts in the eastern Shandong Province (Jiaodong Peninsula). The ore body has formed within the Guojialing granite. In this study, we report the mineral chemistry of pyrite, as well as the S, Pb, and HeO isotope data of the Heilangou gold deposit. The chemical composition of pyrite in the Heilangou gold deposit indicates that the associated gold deposit is a typical magmatic hydrothermal one. The geochemical signatures and crystal structure of pyrite show that the ore-forming materials have been derived from the crust. The S isotope data of the pyrites from Heilangou show an overall range from 5.5 to 7.8&and an average of 6.7&. The S isotope data in this deposit are similar to those from the deposits in the Jiaodong gold belt. The Pb and S isotope variations are small in the Heilangou gold deposit. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios are 17.4653e17.5958, 15.5105e15.5746 and 38.0749e38.4361, respec-tively. These data plot between the lower crust and the orogenic belt. The Pb isotope data in the Heilangou gold deposit are similar to those in the Linglong gold deposit. From the Qixia gold area (the Liukou and Majiayao gold deposits) to the MupingeRushan gold belt (Rushan gold deposit) to the ZhaoeYe gold belt (the Linglong, Sanshandao and Jiaojia gold deposits), the 206Pb/204Pb ratios progressively increase. The DeO isotope data obtained from quartz separates suggest that the ore-forming fluid was similar to a mixture of magmatic and meteoric waters. These results suggest that the ore-forming elements were primarily from source fluids derived from the lower crust.

  18. Equation of state of pyrite to 85 GPa and 2400 K (United States)

    Thompson, E. C.; Chidester, B.; Campbell, A. J.; Prakapenka, V.


    Pyrite (FeS2), a Pa3 space group non-magnetic semiconductor, is the most abundant iron sulfide in nature, yet the high cosmic abundance of sulfur is not reflected in the terrestrial crust, implying it is either sequestered in the Earth's interior or was volatilized during accretion. As it has widely been suggested that sulfur could be one of the contributing light elements leading to the density deficit of Earth's core, a robust thermal equation of state of FeS2 is vital for understanding the evolution and properties of Earth's interior. We performed X-ray diffraction measurements on FeS2 at the GSECARS sector 13-ID-D and HPCAT sector 16-ID-B beamlines at the Advanced Photon Source. Pressures from 17 to 85 GPa and temperatures up to 2400 K were achieved using laser-heated diamond anvil cells. Pressures were determined from the lattice parameters of KBr [1], which served as an insulator and pressure medium, and temperatures were determined by spectroradiometry. No phase transitions were observed in the pyrite structure over the pressure and temperature ranges investigated. By combining our new P-V-T data with previously published room temperature compression data [2], we have determined a thermal equation of state for FeS2, with bulk modulus K=182.6(74) GPa, pressure derivative K'=3.82(25), and αKT=0.00329(45). Our revised equation of state for pyrite is consistent with a core density deficit satisfied by 9-10 wt.% sulfur. We compare these findings to previously published ab intio equation of state parameters for pyrite under a similar range of pressures [3]. [1] Fischer et al. (2012) EPSL 357-358, 268-276. [2] Merkel et al. (2002) PCM 29, 1-9. [3] Le Page and Rodgers (2005) PCM 32, 564-567.

  19. Arsenopyrite and pyrite bioleaching: evidence from XPS, XRD and ICP techniques. (United States)

    Fantauzzi, Marzia; Licheri, Cristina; Atzei, Davide; Loi, Giovanni; Elsener, Bernhard; Rossi, Giovanni; Rossi, Antonella


    In this work, a multi-technical bulk and surface analytical approach was used to investigate the bioleaching of a pyrite and arsenopyrite flotation concentrate with a mixed microflora mainly consisting of Acidithiobacillus ferrooxidans. X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and X-ray-induced Auger electron spectroscopy mineral surfaces investigations, along with inductively coupled plasma-atomic emission spectroscopy and carbon, hydrogen, nitrogen and sulphur determination (CHNS) analyses, were carried out prior and after bioleaching. The flotation concentrate was a mixture of pyrite (FeS(2)) and arsenopyrite (FeAsS); after bioleaching, 95% of the initial content of pyrite and 85% of arsenopyrite were dissolved. The chemical state of the main elements (Fe, As and S) at the surface of the bioreactor feed particles and of the residue after bioleaching was investigated by X-ray photoelectron and X-ray excited Auger electron spectroscopy. After bioleaching, no signals of iron, arsenic and sulphur originating from pyrite and arsenopyrite were detected, confirming a strong oxidation and the dissolution of the particles. On the surfaces of the mineral residue particles, elemental sulphur as reaction intermediate of the leaching process and precipitated secondary phases (Fe-OOH and jarosite), together with adsorbed arsenates, was detected. Evidence of microbial cells adhesion at mineral surfaces was also produced: carbon and nitrogen were revealed by CHNS, and nitrogen was also detected on the bioleached surfaces by XPS. This was attributed to the deposition, on the mineral surfaces, of the remnants of a bio-film consisting of an extra-cellular polymer layer that had favoured the bacterial action.

  20. Further studies of the effects of oxidation on the surface properties of coal and coal pyrite

    Energy Technology Data Exchange (ETDEWEB)

    Herrera, Miguel Nicolas [Univ. of California, Berkeley, CA (United States)


    The objective of this research was to investigate the oxidation behavior of coal and coal pyrite and to correlate the changes in the surface properties induced by oxidation, along with the intrinsic physical and chemical properties of these organic and inorganic materials, with the behavior in physical coal cleaning processes. This provide more fundamental knowledge for understanding the way in which different factors interact in a medium as heterogeneous as coal. Fourteen coal samples of different ranks ranging from high to medium sulfur content were studied by dry oxidation tests at different temperatures and humidities, and by wet oxidation tests using different oxidizing agents. The concentration of surface oxygen functional groups was determined by ion-exchange methods. The changes in the coal composition with oxidation were analyzed by spectroscopic techniques. The wettability of as-received and oxidized coal and coal pyrite samples was assessed by film flotation tests. The electrokinetic behavior of different coals and coal pyrite samples was studied by electrokinetic tests using electrophoresis. Possible oxidation mechanisms have been proposed to explain the changes on the coal surface induced by different oxidation treatments.

  1. Selective Sulfidation of Lead Smelter Slag with Pyrite and Flotation Behavior of Synthetic ZnS (United States)

    Han, Junwei; Liu, Wei; Wang, Dawei; Jiao, Fen; Zhang, Tianfu; Qin, Wenqing


    The selective sulfidation of lead smelter slag with pyrite in the presence of carbon and Na salts, and the flotation behavior of synthetic ZnS were studied. The effects of temperature, time, pyrite dosage, Na salts, and carbon additions were investigated based on thermodynamic calculation, and correspondingly, the growth mechanism of ZnS particles was studied at high temperatures. The results indicated that the zinc in lead smelter slag was selectively converted into zinc sulfides by sulfidation roasting. The sulfidation degree of zinc was increased until the temperature, time, pyrite, and carbon dosages reached their optimum values, under which it was more than 95 pct. The growth of ZnS particles largely depended upon roasting temperature, and the ZnS grains were significantly increased above 1373 K (1100 °C) due to the formation of a liquid phase. After the roasting, the zinc sulfides generated had a good floatability, and 88.34 pct of zinc was recovered by conventional flotation.

  2. Further studies of the effects of oxidation on the surface properties of coal and coal pyrite

    Energy Technology Data Exchange (ETDEWEB)

    Herrera, M.N.


    The objective of this research was to investigate the oxidation behavior of coal and coal pyrite and to correlate the changes in the surface properties induced by oxidation, along with the intrinsic physical and chemical properties of these organic and inorganic materials, with the behavior in physical coal cleaning processes. This provide more fundamental knowledge for understanding the way in which different factors interact in a medium as heterogeneous as coal. Fourteen coal samples of different ranks ranging from high to medium sulfur content were studied by dry oxidation tests at different temperatures and humidities, and by wet oxidation tests using different oxidizing agents. The concentration of surface oxygen functional groups was determined by ion-exchange methods. The changes in the coal composition with oxidation were analyzed by spectroscopic techniques. The wettability of as-received and oxidized coal and coal pyrite samples was assessed by film flotation tests. The electrokinetic behavior of different coals and coal pyrite samples was studied by electrokinetic tests using electrophoresis. Possible oxidation mechanisms have been proposed to explain the changes on the coal surface induced by different oxidation treatments.

  3. Bio-decomposition of rock phosphate containing pyrites by Acidithiobacillus ferrooxidans

    Institute of Scientific and Technical Information of China (English)

    CHI Ru-an; XIAO Chun-qiao; HUANG Xiao-hui; WANG Cun-wen; WU Yuan-xin


    Leaching soluble phosphorus from rock phosphate containing pyrites by Acidithiobacillus ferrooxidans (A. f) is feasible,and the reaction mechanism is as follows. Pyrites are oxidized by A. f. to produce H2SO4 and FeSO4; the rock phosphate is decomposed by H2SO4, forming soluble phosphorus compounds; and Fe2+ from FeSO4 is oxidized to Fe3+, providing energy for the growth of A. f.. In this process, as H2SO4 is produced in the reaction, an acidic condition in the culture medium is formed, which benefits the growth of A. f. and aids both continuous oxidation of pyrites and leaching of soluble phosphorus from rock phosphate.The fraction of phosphorous leached can reach the largest in the presence of 1.0 g/L Fe3+, 200 mg/L Mg2+ and 400 mg/L NH4+. The optimal technological parameters on the fraction of phosphorous leached are as follows: the volume fraction of inocula of A. f, the

  4. Biogeochemical processes governing natural pyrite oxidation and release of acid metalliferous drainage. (United States)

    Chen, Ya-ting; Li, Jin-tian; Chen, Lin-xing; Hua, Zheng-shuang; Huang, Li-nan; Liu, Jun; Xu, Bi-bo; Liao, Bin; Shu, Wen-sheng


    The oxidative dissolution of sulfide minerals (principally pyrite) is responsible for the majority of acid metalliferous drainage from mine sites, which represents a significant environmental problem worldwide. Understanding the complex biogeochemical processes governing natural pyrite oxidation is critical not only for solving this problem but also for understanding the industrial bioleaching of sulfide minerals. To this end, we conducted a simulated experiment of natural pyrite oxidative dissolution. Pyrosequencing analysis of the microbial community revealed a distinct succession across three stages. At the early stage, a newly proposed genus, Tumebacillus (which can use sodium thiosulfate and sulfite as the sole electron donors), dominated the microbial community. At the midstage, Alicyclobacillus (the fifth most abundant genus at the early stage) became the most dominant genus, whereas Tumebacillus was still ranked as the second most abundant. At the final stage, the microbial community was dominated by Ferroplasma (the tenth most abundant genus at the early stage). Our geochemical and mineralogical analyses indicated that exchangeable heavy metals increased as the oxidation progressed and that some secondary sulfate minerals (including jarosite and magnesiocopiapite) were formed at the final stage of the oxidation sequence. Additionally, we propose a comprehensive model of biogeochemical processes governing the oxidation of sulfide minerals.

  5. Matrix composition and community structure analysis of a novel bacterial pyrite leaching community. (United States)

    Ziegler, Sibylle; Ackermann, Sonia; Majzlan, Juraj; Gescher, Johannes


    Here we describe a novel bacterial community that is embedded in a matrix of carbohydrates and bio/geochemical products of pyrite (FeS(2)) oxidation. This community grows in stalactite-like structures--snottites--on the ceiling of an abandoned pyrite mine at pH values of 2.2-2.6. The aqueous phase in the matrix contains 200 mM of sulfate and total iron concentrations of 60 mM. Micro-X-ray diffraction analysis showed that jarosite [(K,Na,H(3)O)Fe(3)(SO(4))(2)(OH)(6)] is the major mineral embedded in the snottites. X-ray absorption near-edge structure experiments revealed three different sulfur species. The major signal can be ascribed to sulfate, and the other two features may correspond to thiols and sulfoxides. Arabinose was detected as the major sugar component in the extracellular polymeric substance. Via restriction fragment length polymorphism analysis, a community was found that mainly consists of iron oxidizing Leptospirillum and Ferrovum species but also of bacteria that could be involved in dissimilatory sulfate and dissimilatory iron reduction. Each snottite can be regarded as a complex, self-contained consortium of bacterial species fuelled by the decomposition of pyrite.

  6. Hydrothermal vents as a source of pyrite and trace metal- containing mineral nanoparticles to the ocean (United States)

    Gartman, A.; Yucel, M.; Luther, G. W.


    The pathways by which metals from hydrothermal vents may be transported through the ocean are still largely unknown. We demonstrate that pyrite nanoparticles as small as 4nm aggregate into nanoframboids of 50-350nm and are emitted from high temperature black smokers from vents at Lau Basin and the East Pacific Rise. These nanoparticles, which contain other metals including copper, are characterized via chemical methods as well as by using a combination of physical chemical techniques (TEM, SEM-EDS and EELS). Data indicate that the metal sulfide nanoparticles from Lau Basin, a back arc basin and EPR 9N, a fast spreading mid ocean ridge, have similar morphology. We report that laboratory hydrothermal syntheses can reproduce the size and morphology of the natural pyrite nanoparticles. Laboratory oxidation experiments show that these synthesized pyrite nanoparticles are stable in oxic seawater for months, and thus provide a potential transport mechanism for iron far from vent sources. These nanoparticles as well as others including iron silicates, which have also been identified, likely influence the transport of iron and other elements from the hydrothermal environment to the ocean. Hydrothermal vents serve as nanoparticle 'factories' that fertilize the ocean with metals that are important in a variety of biogeochemical processes.

  7. Synthesis and adsorption/photocatalysis performance of pyrite FeS2 (United States)

    Liu, Shuling; Li, Miaomiao; Li, Shu; Li, Honglin; Yan, Lu


    FeS2 crystallites were synthesized successfully via a solvothermal method, using potassium ferrocyanide K4[Fe(CN)6]·3H2O as Fe source, sulfur powder as S source in the presence of polyvinyl pyrrolidone (PVP) as dispersant. And potassium carbonate provided an alkaline environment. The phase and morphology of the products were characterized by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). It was found that the temperature and solvent ratio (V:VO) play a crucial role in the formation of FeS2 with a cubic phase structure (pyrite). Then based on a series of experiments, the possible formation mechanism of pyrite FeS2 crystallites was proposed. In addition, research also showed that the as-prepared pyrite FeS2 crystallites could high-efficiently absorb or photocatalytically degrade some organic dyes such as Methylene blue (MB), Safranine T, Methyl orange (MO), Rhodamine B (Rh B) and Pyronine B. Furthermore, the adsorption and photocatalytic degradation abilities of FeS2 for organic dyes were also compared.

  8. Copper and cobalt recovery from pyrite ashes of a sulphuric acid plant. (United States)

    Erust, Ceren; Akcil, Ata


    The pyrite ashes formed as waste material during the calcination of concentrated pyrite ore used for producing sulphuric acid not only has a high iron content but also contains economically valuable metals. These wastes, which are currently landfilled or dumped into the sea, cause serious land and environmental pollution problems owing to the release of acids and toxic substances. In this study, physical (sulphation roasting) and hydrometallurgical methods were evaluated for their efficacy to recover non-iron metals with a high content in the pyrite ashes and to prevent pollution thereby. The preliminary enrichment tests performed via sulphation roasting were conducted at different roasting temperatures and with different acid amounts. The leaching tests investigated the impact of the variables, including different solvents, acid concentrations and leach temperatures on the copper and cobalt leaching efficiency. The experimental studies indicated that the pre-enrichment via sulphation roasting method has an effect on the leaching efficiencies of copper and cobalt, and that approximate recoveries of 80% copper and 70% cobalt were achieved in the H2O2-added H2SO4 leaching tests.

  9. Biogeneration of iron-based catalyst precursors by Acidianus brierleyi on high- and low-pyrite coals for direct liquefaction.

    Energy Technology Data Exchange (ETDEWEB)

    Murty, M.V.S.; Huggins, F.E.; Aleem, M.I.H.; Kermode, R.I.; Bhattacharyya, D. [University of Kentucky, Lexington, KY (United States). Dept. of Chemical Engineering


    Treatment of high-pyrite, high-sulphur Illinois (IBS) coals and pyrite-free Blind Canyon (DECS) coal with added pyrite in the presence of {ital Acidianus brierleyi} showed formation of iron oxyhydroxide (FeOOH) particles and subsequent sulphiding caused enhancement in liquefaction and oil yield. IBC No. 101 and 105, and DECS No. 17 containing different amounts of pyrite were treated with {ital A. brierleyi} to evaluate its effect on FeOOH formation. Chemical analysis of the liquid phase and Moessbauer analysis of the coals revealed that all the biotreated coals showed significant reduction in pyrite after 21 days (or less with pH alteration in the middle of IBC No. 105 coal run) of incubation. Further data on bioprocessed coals obtained from Moessbauer spectroscopy verified the formation of an FeOOH phase, which acts as a catalyst precursor for direct coal liquefaction (DCL). The direct liquefaction conversion and oil yield of the biotreated DECS No. 17 coal with added pyrite increased by 14 and 5% respectively, over the control which did not contain {ital A. brierleyi}. 40 refs., 8 figs., 2 tabs.

  10. Sulfur amino acids and alanine on pyrite (100) by X-ray photoemission spectroscopy: Surface or molecular role? (United States)

    Sanchez-Arenillas, M.; Galvez-Martinez, S.; Mateo-Marti, E.


    This paper describes the first successful adsorption of the cysteine, cystine, methionine and alanine amino acids on the pyrite (100) surface under ultra-high vacuum conditions with crucial chemical adsorption parameters driving the process. We have demonstrated by X-ray photoemission spectroscopy (XPS) that the surface pretreatment annealing process on pyrite surfaces is a critical parameter driving surface reactivity. The presence of enriched monosulfide species on the pyrite (100) surface favours the amino acid NH2 chemical form, whereas a longer annealing surface pretreatment of over 3 h repairs the sulfur vacancies in the pyrite, enriching disulfide species on the pyrite surface, which promotes NH3+ adsorption due to the sulfur vacancies in the pyrite being replaced by sulfur atom dimers (S22-) on the surface. Furthermore, even if the surface chemistry (monosulfide or disulfide species enrichment) is the main factor promoting a partial conversion from NH2 to NH3+ species, the unique chemical structure of each amino acid provides a particular fingerprint in the process.

  11. A silica/fly ash-based technology for controlling pyrite oxidation. Semi-annual, March 1, 1996 - August 31, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Evangelou, V.P. [USDOE Pittsburgh Energy Technology Center, PA (United States)


    The overall objective is to develop methodologies by which metasilicate or fly ash may produce an effective coating on pyrite surfaces for inhibiting pyrite oxidation. During the past six months, the investigators produced wet chemistry evidence demonstrating that pyrite-HCO{sub 3} complexes promote pyrite oxidation. This is an important finding for their over all strategy in controlling pyrite oxidation because it suggests that pyrite microencapsulation is important in order to control oxidation in near cirumneutral pH environments produced by addition of alkaline material, e.g., fly ash. In their previous studies, the investigators reported that pyrite microencapsulation could be carried out by reacting pyrite with a pH buffered solution and in the presence of metasilicate. The coating formed on the surface of pyrite appeared to be an amorphous iron-oxide-silicate material which inhibited pyrite oxidation. During this past six months, the investigators evaluated: the molecular mechanisms of silicate adsorption by iron oxide; the effects of silicate on the bulk and surface properties of iron oxides; and the effect of silicate on metal-cation adsorption properties by iron oxides.

  12. Episodic growth of Mt. Shasta, CA, documented by argon geochronology (United States)

    Calvert, A. T.; Christiansen, R. L.


    eruptive focus shifted 1.5 km north (Misery Hill) between 50-35 ka, erupting silicic andesite and mafic dacite onto all sectors of the volcano. Flank vents directly south and north erupted domes and lavas 20-15 ka. At ~11 ka a voluminous episode began with the subplinian Red Banks pumice followed shortly by Shastina andesite/dacite lavas, domes, and pyroclastic flows, and soon after by Black Butte flank dacites. Existing 14C geochronology, and stratigraphic studies of the deposits show no eruptive breaks and constrain the episode to have lasted less than a few hundred years. Subsequent Holocene eruptions all issued from the modern summit (Hotlum cone), producing at least 10 large lava flows directed toward the NE sector, along with pyroclastic and debris flows, and a summit dome. Preliminary argon geochronology in progress dates summit lavas at 8.8, 5.8 and 4.7 ka.

  13. Geology, zircon geochronology, and petrogenesis of Sabalan volcano (northwestern Iran) (United States)

    Ghalamghash, J.; Mousavi, S. Z.; Hassanzadeh, J.; Schmitt, A. K.


    Sabalan Volcano (NW Iran) is an isolated voluminous (4821 m elevation; > 800 km2) composite volcano that is located within the Arabia-Eurasia collision zone. Its edifice was assembled by recurrent eruptions of trachyandesite and dacite magma falling into a relatively restricted compositional range (56-67% SiO2) with high-K calc-alkaline and adakitic trace element (Sr/Y) signatures. Previous K-Ar dating suggested protracted eruptive activity between 5.6 and 1.4 Ma, and a two stage evolution which resulted in the construction of the Paleo- and Neo-Sabalan edifices, respectively. The presence of a topographic moat surrounding Neo-Sabalan and volcanic breccias with locally intense hydrothermal alteration are indicative of intermittent caldera collapse of the central part of Paleo-Sabalan. Volcanic debris-flow and debris-avalanche deposits indicate earlier episodes of volcanic edifice collapse during the Paleo-Sabalan stage. In the Neo-Sabalan stage, three dacitic domes extruded to form the summits of Sabalan (Soltan, Heram, and Kasra). Ignimbrites and minor pumice fall-out deposits are exposed in strongly dissected drainages that in part have breached the caldera depression. Lavas and pyroclastic rocks are varyingly porphyritic with Paleo-Sabalan rocks being trachyandesites carrying abundant phenocrysts (plagioclase + amphibole + pyroxene + biotite). The Neo-Sabalan rocks are slightly more evolved and include dacitic compositions with phenocrysts of plagioclase + amphibole ± alkali-feldspar ± quartz. All Sabalan rock types share a common accessory assemblage (oxides + apatite + zircon). High spatial resolution and sensitivity U-Pb geochronology using Secondary Ionization Mass Spectrometry yielded two clusters of zircon ages which range from 4.5 to 1.3 Ma and 545 to 149 ka, respectively (all ages are averages of multiple determinations per sample). U-Th zircon geochronology for selected Neo-Sabalan rocks agrees with the U-Pb ages, with the youngest zircon rims dating

  14. Geology, geochemistry and geochronology of the Songwe Hill carbonatite, Malawi (United States)

    Broom-Fendley, Sam; Brady, Aoife E.; Horstwood, Matthew S. A.; Woolley, Alan R.; Mtegha, James; Wall, Frances; Dawes, Will; Gunn, Gus


    Songwe Hill, Malawi, is one of the least studied carbonatites but has now become particularly important as it hosts a relatively large rare earth deposit. The results of new mapping, petrography, geochemistry and geochronology indicate that the 0.8 km diameter Songwe Hill is distinct from the other Chilwa Alkaline Province carbonatites in that it intruded the side of the much larger (4 × 6 km) and slightly older (134.6 ± 4.4 Ma) Mauze nepheline syenite and then evolved through three different carbonatite compositions (C1-C3). Early C1 carbonatite is scarce and is composed of medium-coarse-grained calcite carbonatite containing zircons with a U-Pb age of 132.9 ± 6.7 Ma. It is similar to magmatic carbonatite in other carbonatite complexes at Chilwa Island and Tundulu in the Chilwa Alkaline Province and others worldwide. The fine-grained calcite carbonatite (C2) is the most abundant stage at Songwe Hill, followed by a more REE- and Sr-rich ferroan calcite carbonatite (C3). Both stages C2 and C3 display evidence of extensive (carbo)-hydrothermal overprinting that has produced apatite enriched in HREE (<2000 ppm Y) and, in C3, synchysite-(Ce). The final stages comprise HREE-rich apatite fluorite veins and Mn-Fe-rich veins. Widespread brecciation and incorporation of fenite into carbonatite, brittle fracturing, rounded clasts and a fenite carapace at the top of the hill indicate a shallow level of emplacement into the crust. This shallow intrusion level acted as a reservoir for multiple stages of carbonatite-derived fluid and HREE-enriched apatite mineralisation as well as LREE-enriched synchysite-(Ce). The close proximity and similar age of the large Mauze nepheline syenite suggests it may have acted as a heat source driving a hydrothermal system that has differentiated Songwe Hill from other Chilwa carbonatites.

  15. The Violent Early Solar System, as Told by Sample Geochronology (United States)

    Cohen, Barbara


    One of the legacies of the samples collected by the Apollo and Luna missions is the link forged between radiometric ages of rocks and relative ages according to stratigraphic relationships and impact crater size-frequency distributions. Our current understanding of the history of the inner solar system is based on the relative chronology of individual planets, tied to the absolute geochronology of the Moon via these important samples. Sample ages have enabled us to infer that impact-melt breccias from Apollo 14 and 15 record the formation of the Imbrium Basin, those from the highland massifs at Apollo 17 record the age of Serenitatis, those from the KREEP-poor Apollo 16 site record the age of Nectaris, and materials from Luna 24 record the age of Crisium. Ejecta from smaller and younger craters Copernicus and Tycho were sampled at Apollo 12 and 17, respectively, and local craters such as Cone at Apollo 14, and North Ray and South Ray at Apollo 16 were also sampled and ages determined for those events. Much of what we understand about the lunar impact flux is based on these ages. Samples from these nearside locations reveal a preponderance of impact-disturbed or recrystallized ages between 3.75 and 3.95 billion years. Argon and lead loss (and correlated disturbances in the Rb-Sr system) have been attributed to metamorphism of the lunar crust by an enormous number of impacts in a brief pulse of time, called the Lunar Cataclysm or Late Heavy Bombardment. Subsequent high-precision geochronometric analyses of Apollo samples and lunar highlands meteorites show a wider range of ages, but very few older than 4 Ga. The paucity of ancient impact melt rocks has been interpreted to mean that either that most impact basins formed at this time, or that ejecta from the large, near-side, young basins dominates the Apollo samples.

  16. Geochemistry of Early Frasnian (Late Devonian) pyrite-ammonoid level in the Kostomłoty Basin, Poland, and a new proxy parameter for assessing the relative amount of syngenetic and diagenetic pyrite (United States)

    Pisarzowska, Agnieszka; Berner, Zsolt A.; Racki, Grzegorz


    Pyrite geochemistry (isotope and trace element composition, degree of pyritization, S/Corg ratio) was used in context of selected lithogeochemical parameters (major and trace elements, including sulphur, organic carbon, and δ13C of carbonate carbon) to constrain fluctuations in depositional conditions during the Early to Middle Frasnian carbon isotopic perturbation (punctata Event) in the Kostomłoty Basin, Poland. Based on the ratio between the sum of oxyanionic elements and transition metals in pyrite, a new proxy parameter (index of syngenetic pyrite, ISYP) is proposed for assessing the relative amount of syngenetic pyrite in a sample. The distribution of the ISYP along the Kostomłoty - Małe Górki section (upper Szydłówek to the basal Kostomłoty beds) is in concert with conclusions inferred from paleoecologic data and other geochemical parameters (degree of pyritization, S/Corg, δ34Spyrite). According to these, the lower segment of the Szydłówek Beds was deposited in a normally oxygenated environment, but undergoing increasing primary productivity in surface water, as indicated by an increase in δ13Ccarb and in Cu/Zr ratio in bulk rock, which triggered the periodic deposition of sediments slightly enriched in organic matter, notably within the pyrite-ammonoid level (= Goniatite Level). Fluctuating, but in general high S/Corg ratios, DOPR values and ISYP values suggest that during this time - against the background of a generally dysoxic environment - shorter or longer lasting episodes of more restricted (anoxic and possibly even euxinic) bottom water conditions developed. Low sedimentation rates enabled a continuous and practically unlimited supply of sulphate during bacterial sulphate reduction (BSR), which in turn led to a strong depletion of pyrite sulphur in 34S in this interval (constantly around -29‰). In contrast, below and above the Goniatite Level, higher δ34S values (up to + 3‰), are compatible with closed system conditions and higher

  17. Derivation of S and Pb in phanerozoic intrusion-related metal deposits from neoproterozoic sedimentary pyrite, Great Basin, United States (United States)

    Vikre, P.G.; Poulson, S.R.; Koenig, A.E.


    The thick (???8 km), regionally extensive section of Neoproterozoic siliciclastic strata (terrigenous detrital succession, TDS) in the central and eastern Great Basin contains sedimentary pyrite characterized by mostly high d34S values (-11.6 to 40.8%, derived from reduction of seawater sulfate, and by markedly radiogenic Pb isotopes ( 207Pb/204Pb derivation of deposit S and Pb from TDS pyrite. Minor element abundances in TDS pyrite (e.g., Pb, Zn, Cu, Ag, and Au) compared to sedimentary and hydrothermal pyrite elsewhere are not noticeably elevated, implying that enrichment in source minerals is not a precondition for intrusion-related metal deposits. Three mechanisms for transferring components of TDS sedimentary pyrite to intrusion-related metal deposits are qualitatively evaluated. One mechanism involves (1) decomposition of TDS pyrite in thermal aureoles of intruding magmas, and (2) aqueous transport and precipitation in thermal or fluid mixing gradients of isotopically heavy S, radiogenic Pb, and possibly other sedimentary pyrite and detrital mineral components, as sulfide minerals in intrusion-related metal deposits. A second mechanism invokes mixing and S isotope exchange in thermal aureoles of Pb and S exsolved from magma and derived from decomposition of sedimentary pyrite. A third mechanism entails melting of TDS strata or assimilation of TDS strata by crustal or mantle magmas. TDS-derived or assimilated magmas ascend, decompress, and exsolve a mixture of TDS volatiles, including isotopically heavy S and radiogenic Pb from sedimentary pyrite, and volatiles acquired from deeper crustal or mantle sources. In the central and eastern Great Basin, the wide distribution and high density of small to mid-sized vein, replacement, and skarn intrusion-related metal deposits in lower Paleozoic rocks that contain TDS sedimentary pyrite S and Pb reflect (1) prolific Jurassic, Cretaceous, and Tertiary magmatism, (2) a regional, substrate reservoir of S and Pb in

  18. Pyrite deformation and connections to gold mobility: insight from micro-structural analysis and trace element mapping (United States)

    Dubosq, Renelle; Rogowitz, Anna; Lawley, Christopher; Schneider, David; Jackson, Simon


    Pyrite is an important and ubiquitous gold-bearing phase in many orogenic gold deposits making the study of its deformation behaviour under metamorphic conditions crucial to the understanding of gold (re)mobilization. However, pyrite deformation mechanisms and their influence on the retention or release of trace elements during deformation and metamorphism remain poorly understood. We propose a syn- to post-peak metamorphic and deformation driven gold upgrading model where gold is remobilized through deformation-induced diffusion pathways in the form of substructures in pyrite. The middle amphibolite facies assemblage (actinolite-biotite-plagioclase-almandine) of the Detour Lake deposit (Canada) makes it an ideal study area due to maximum temperatures reaching 550°C, exceeding the conditions for plastic deformation in pyrite (450°C). The world-class Detour Lake deposit, containing 16.4 Moz of Au at 1 g/t, is a Neoarchean orogenic gold ore body located in the northern Abitibi district within the Superior Province. The mine is situated along the high strain, sub-vertical ductile-brittle Sunday Lake Deformation Zone (SLDZ) parallel to the broadly E-W trending Abitibi greenstone belt. Herein we combine orientation contrast (OC) forescatter imaging, electron backscatter diffraction (EBSD) and 2D laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) trace element pyrite mapping to evaluate the influence of pyrite brittle and plastic deformation on the release of trace elements during syn-metamorphic gold remobilization. Local misorientation patterns in pyrite exhibit parallel bands that can be described by continuous rotation around one of the axes, whereas higher strain areas reveal more heterogeneous misorientation patterns and the development of low-angle grain boundaries with late fractures indicative of dislocation creep and strain hardening. These late fractures are an important micro-structural setting for gold and clusters of precious

  19. Geochronology Research and Its Significance for Mo-W Polymetallic Deposit of Dabao Mountain in Northern Guangdong province%粤北大宝山钼钨多金属矿床年代学研究及其意义

    Institute of Scientific and Technical Information of China (English)

    杜国民; 梅玉萍; 蔡红; 罗俊华


    Through the precise dating measuring of the pyrite and quartz minerals in different types of Mo-W polymetallic deposits in Dabao mountain, northern Guangdong province with Rb-Sr isochron method, the age of the pyrite in laminated ores is yielded 168±5Ma (95% reliability), the age of quartz minerals in quartz-molybdenite veins is yielded 164±3 Ma (95% reliability), and the age of quartz minerals in pyrite- quartz lodes is yielded 162±4 Ma (95% reliability) respectively. The results showed that the Cu-Pb-Zn ores and the Mo-W minerals of Dabao polymetallic deposit were formed at 168 - 162 Ma. The results also agreed with former studies that the pyrrhotite minerals formation time was between 165±1 Ma by Re-Os dating method. In consideration of the obviously coupled relationships of the formation time and space between the Cu-Pb-Zn and Mo-W minerals and the secondary dacite and granodiorite porphyry, it showed that the min- eralization of the deposit was related to the early magmatic activities of Yanshan movement in these areas.%本文对大宝山钼钨多金属矿床中不同类型矿石中黄铁矿及石英矿物用Rb-Sr等时线法进行了精细测定,分别获得层纹状矿石中黄铁矿的年龄为168±5Ma(95%可信度),辉钼矿石英脉中石英矿物年龄为164+3Ma(95%可信度)和黄铁矿石英脉中石英矿物年龄为162±4Ma(95%可信度),测定结果表明,大宝山铝钨多金属矿床铜铅锌和钼钨成矿阶段形成的时间在168~162Ma之间。本研究所获得的结果也与前人所获得的层状铜铅锌矿石和脉状矿石中辉钼矿的Re-Os模式年龄为165+1Ma一致。鉴于铜铅锌和钼钨矿床在形成时间和空间上与次英安斑岩和花岗闪长斑岩具有明显的耦合关系,据此表明,其成矿作用主要与区内燕山早期岩浆活动有关。

  20. Gold and trace element zonation in pyrite using a laser imaging technique: Implications for the timing of gold in orogenic and carlin-style sediment-hosted deposits (United States)

    Large, R.R.; Danyushevsky, L.; Hollit, C.; Maslennikov, V.; Meffre, S.; Gilbert, S.; Bull, S.; Scott, R.; Emsbo, P.; Thomas, H.; Singh, B.; Foster, J.


    Laser ablation ICP-MS imaging of gold and other trace elements in pyrite from four different sediment- hosted gold-arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit: an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements, in particular, As, Ni, Pb, Zn, Ag, Mo, Te, V, and Se; and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and/or hydrothermal pyrite or as narrow gold- arsenic rims on the outermost parts of the overgrowth hydrothermal pyrite. Compared to the diagenetic pyrites, the hydrothermal pyrites are commonly depleted in Ni, V, Zn, Pb, and Ag with cyclic zones of Co, Ni, and As concentration. The outermost hydrothermal pyrite rims are either As-Au rich, as in moderate- to high- grade deposits such as Carlin and Bendigo, or Co-Ni rich and As-Au poor as in moderate- to low-grade deposits such as Sukhoi Log and Spanish Mountain. The early enrichment of gold in arsenic-bearing syngenetic to diagenetic pyrite, within black shale facies of sedimentary basins, is proposed as a critical requirement for the later development of Carlin-style and orogenic gold deposits in sedimentary environments. The best grade sediment-hosted deposits appear to have the gold climax event, toward the final stages of deformation-related hydrothermal pyrite growth and fluid flow. ?? 2009 Society of Economic Geologists, Inc.

  1. Research on the growth orientation of pyrite grains in the colloform textures in Baiyunpu Pb-Zn polymetallic deposit, Hunan, China (United States)

    Gao, Shang; Huang, Fei; Gu, Xiangping; Chen, Zhenyu; Xing, Miaomiao; Li, Yongli


    A large number of colloform-textured pyrites were found in Baiyunpu Pb-Zn ore bodies in Xinshao County, Hunan, China. This study investigates the growth orientation of the pyrite grains in these structures by field emission scanning electron microscopy (FE-SEM), in situ micro X-ray diffraction (μXRD) and electron backscatter diffraction (EBSD). The growth proceeded from micro-crystalline cores in the colloform textures. Moreover, the pyrite layers were discrete and separated by locally significant quantities of galena and calcite. The μXRD results suggested clear crystalline characteristics and weakly preferred orientations of the colloform textures. EBSD confirmed that the pyrite grains exist preferred orientations or in the layered zones. According to the crystal growth theory, the formation and variation of crystal preferred orientations (CPOs) in pyrite are mainly restricted by the internal crystal structure of the pyrite and depends on the external environment conditions, such as trace element concentrations and the supersaturation degree. We inferred the evolutionary regularity of lattice planes with different indices in the pyrite crystal structure from morphological, compositional and growth orientation information, which reflect the crystal growth history of the colloform pyrite. This study will advance our understanding of the growth processes of colloform pyrite and environmental evolution in the Baiyunpu Pb-Zn polymetallic deposits.

  2. Flotation and Adsorption of a New Polysaccharide Depressant on Pyrite and Talc in the Presence of a Pre-Adsorbed Xanthate Collector

    Directory of Open Access Journals (Sweden)

    Wei Deng


    Full Text Available The flotation and adsorption of a new polysaccharide konjac gum (KG on pyrite and talc in the presence of pre-adsorbed potassium butyl xanthate (PBX is investigated. The micro-flotation results show that KG is a quality depressant for talc and that conditioning the minerals initially with PBX before KG will increase the recovery difference between pyrite and talc. The results of artificially mixing the minerals show that compared with adding KG before PBX, when minerals are pre-adsorbed with PBX, the grade and the recovery of sulfur (S increases by 1.96% and 5.44%, respectively. The contact angle results show that the addition of PBX before KG will increase the contact angles of pyrite, but the addition order of KG/PBX has little influence on the contact angles of talc. The adsorption tests show that KG can adsorb on pyrite and talc surfaces, while PBX can only adsorb on the pyrite surface. The addition order of KG/PBX affects the adsorption of KG and PBX on the pyrite surface but not on the talc surface. Fourier transform infrared (FTIR spectra analysis further demonstrates the chemical adsorption of KG on pyrite and talc surfaces, while PBX chemisorbs on the pyrite surface. Based on these analyses, a schematic illustration of the reagent adsorption forms on pyrite and talc surfaces is drawn to explain the competitive adsorption of KG and PBX on mineral surfaces.

  3. Direct Detection of Fe(II) in Extracellular Polymeric Substances (EPS) at the Mineral-Microbe Interface in Bacterial Pyrite Leaching. (United States)

    Mitsunobu, Satoshi; Zhu, Ming; Takeichi, Yasuo; Ohigashi, Takuji; Suga, Hiroki; Jinno, Muneaki; Makita, Hiroko; Sakata, Masahiro; Ono, Kanta; Mase, Kazuhiko; Takahashi, Yoshio


    We herein investigated the mechanisms underlying the contact leaching process in pyrite bioleaching by Acidithiobacillus ferrooxidans using scanning transmission X-ray microscopy (STXM)-based C and Fe near edge X-ray absorption fine structure (NEXAFS) analyses. The C NEXAFS analysis directly showed that attached A. ferrooxidans produces polysaccharide-abundant extracellular polymeric substances (EPS) at the cell-pyrite interface. Furthermore, by combining the C and Fe NEXAFS results, we detected significant amounts of Fe(II), in addition to Fe(III), in the interfacial EPS at the cell-pyrite interface. A probable explanation for the Fe(II) in detected EPS is the leaching of Fe(II) from the pyrite. The detection of Fe(II) also indicates that Fe(III) resulting from pyrite oxidation may effectively function as an oxidizing agent for pyrite at the cell-pyrite interface. Thus, our results imply that a key role of Fe(III) in EPS, in addition to its previously described role in the electrostatic attachment of the cell to pyrite, is enhancing pyrite dissolution.

  4. Direct Detection of Fe(II) in Extracellular Polymeric Substances (EPS) at the Mineral-Microbe Interface in Bacterial Pyrite Leaching (United States)

    Mitsunobu, Satoshi; Zhu, Ming; Takeichi, Yasuo; Ohigashi, Takuji; Suga, Hiroki; Jinno, Muneaki; Makita, Hiroko; Sakata, Masahiro; Ono, Kanta; Mase, Kazuhiko; Takahashi, Yoshio


    We herein investigated the mechanisms underlying the contact leaching process in pyrite bioleaching by Acidithiobacillus ferrooxidans using scanning transmission X-ray microscopy (STXM)-based C and Fe near edge X-ray absorption fine structure (NEXAFS) analyses. The C NEXAFS analysis directly showed that attached A. ferrooxidans produces polysaccharide-abundant extracellular polymeric substances (EPS) at the cell-pyrite interface. Furthermore, by combining the C and Fe NEXAFS results, we detected significant amounts of Fe(II), in addition to Fe(III), in the interfacial EPS at the cell-pyrite interface. A probable explanation for the Fe(II) in detected EPS is the leaching of Fe(II) from the pyrite. The detection of Fe(II) also indicates that Fe(III) resulting from pyrite oxidation may effectively function as an oxidizing agent for pyrite at the cell-pyrite interface. Thus, our results imply that a key role of Fe(III) in EPS, in addition to its previously described role in the electrostatic attachment of the cell to pyrite, is enhancing pyrite dissolution. PMID:26947441

  5. Re-Os dating of molybdenite from Tongchanggou Mo-polymetallic deposit in northwest Yunnan and its metallogenic environment%滇西北铜厂沟钼多金属矿床辉钼矿Re-Os同位素年龄及其成矿环境

    Institute of Scientific and Technical Information of China (English)

    李文昌; 余海军; 尹光侯; 曹晓民; 黄定柱; 董涛


    铜厂沟钼多金属矿床位于扬子陆块西缘坳陷带与义敦岛弧和甘孜-理塘结合带3个构造单元交汇部位,它是近年来对该区燕山期成矿作用研究并取得找矿突破的重要成果.该矿床包含了岩枝全岩矿化、顶部矽卡岩型及围岩热液脉型等热液交代矿化,构成了斑岩成矿系列.矿床已达大型,并显示出超大型的远景.运用辉钼矿Re-Os同位素定年技术,获得了6件样品的模式年龄,为(82.34±1.28)~(88.27±1.23) Ma,其加权平均年龄为(85±2) Ma,等时线年龄为(85±10) Ma,两者在误差范围内一致,表明成矿作用发生于燕山期,此时,该区处于中咱地块与扬子陆块强烈碰撞至后碰撞阶段,由于地壳加厚,壳熔或壳幔混熔形成了S型花岗(斑)岩和强烈的钼多金属矿化.铜厂沟矿床内辉钼矿样晶的w(Re)为16 440~43 530 ng/g,指示其成矿物质来源为壳幔混源,以壳源物质为主.据野外调查和室内研究推测,在该矿区的深部存在燕山期的隐伏花岗(斑)岩体,成矿作用与岩浆上侵有关.该区的燕山期酸性岩带穿过了义敦岛弧进入扬子陆块西缘,呈近NS向展布,滇西北地区,北部从休瓦促向南至热林、红山、铜厂沟,形成了一系列大-中型钼多金属矿床.成矿背景和成矿预测研究对该带的找矿勘查具有十分重要的指导意义.%The Tongchanggou Mo-polymetallic deposit lies in the western margin depression belt of the Yangtze land-mass and is adjacent to Yidun island arc and Garze-Litang suture zone. It is a representative ore deposit in studying Yanshanian mineralization and shows bright future for further prospecting. Some intrusions (or apophyses) have been wholly mineralized, and hydrothermal metasomatism in the upper part mainly displays skarn type and hydrothermal vein type mineralization in wall rocks, forming a porphyry minerogenetic series. The ore deposit is a large-size or even a superlarge deposit. Re-Os isotopic dating

  6. Cinnabar, arsenian pyrite and thallium-enrichment in active shallow submarine hydrothermal vents at Paleochori Bay, Milos Island, Greece (United States)

    Kati, Marianna; Voudouris, Panagiotis; Valsami-Jones, Eugenia; Magganas, Andreas; Baltatzis, Emmanouil; Kanellopoulos, Christos; Mavrogonatos, Constantinos


    We herein report the discovery of active cinnabar-depositing hydrothermal vents in a submarine setting at Paleochori Bay, within the offshore southeastern extension of the Milos Island Geothermal Field, South Aegean Active Volcanic Arc. Active, low temperature (up to 115 °C) hydrothermal venting through volcaniclastic material has led to a varied assemblage of sulfide and alteration mineral phases in an area of approximately 1 km2. Our samples recovered from Paleochori Bay are hydrothermal edifices composed of volcaniclastic detrital material cemented by pyrite, or pure sulfide (mainly massive pyrite) mounts. Besides pyrite and minor marcasite, the hydrothermal minerals include cinnabar, amorphous silica, hydrous ferric oxides, carbonates (aragonite and calcite), alunite-jarosite solid solution and Sr-rich barite. Among others, growth textures, sieve-textured pyrite associated with barite, alunite-jarosite solid solution and hydrous ferric oxides rims colloform-banded pyrite layers. Overgrowths of arsenian pyrite layers (up to 3.2 wt. % As and/or up to 1.1 wt. % Mn) onto As-free pyrite indicate fluctuation in As content of the hydrothermal fluid. Mercury, in the form of cinnabar, occurs in up to 5 μm grains within arsenian pyrite layers, usually forming distinct cinnabar-enriched micro-layers. Hydrothermal Sr-rich barite (barite-celestine solid solution), pseudocubic alunite-jarosite solid solution and Mn- and Sr-enriched carbonates occur in various amounts and closely associated with pyrite and/or hydrous ferric oxides. Thallium-bearing sulfides and/or sulfosalts were not detected during our study; however, hydrous ferric oxides show thallium content of up to 0.5 wt. % Tl. The following scenarios may have played a role in pyrite precipitation at Paleochori: (a) H2S originally dissolved in the deep fluid but separated upon boiling could have reacted with oxygenated seawater under production of sulphuric acid, thus causing leaching and dissolution of primary iron

  7. Multiscale characterization of pyritized plant tissues in blueschist facies metamorphic rocks (United States)

    Bernard, Sylvain; Benzerara, Karim; Beyssac, Olivier; Brown, Gordon E., Jr.


    Pyritized plant tissues with well-preserved morphology were studied in rocks from Vanoise (western Alps, France) that experienced high-pressure, low-temperature metamorphic conditions in the blueschist facies during the Alpine orogeny. Organic and inorganic phases composing these fossils were characterized down to the nanometer scale by Raman microspectroscopy, scanning transmission X-ray microscopy and transmission electron microscopy. The graphitic but disordered organic matter composing these fossils is chemically and structurally homogeneous and mostly contains aromatic functional groups. Its original chemistry remains undefined likely because it was significantly transformed by diagenetic processes and/or thermal degradation during metamorphism. Various mineral phases are closely associated with this organic matter, including sulphides such as pyrite and pyrrhotite, carbonates such as ankerite and calcite, and iron oxides. A tentative time sequence of formation of these diverse mineral phases relative to organic matter decay is proposed. The absence of traces of organic matter sulphurization, the pervasive pyritization of the vascular tissues and the presence of ankerite suggest that the depositional/diagenetic environment of these metasediments was likely rich in reactive iron. Fe-sulphides and ankerite likely precipitated early and might have promoted the preservation of the fossilized biological soft tissues by providing mechanical resistance to compaction during diagenesis and subsequent metamorphism. In contrast, iron oxides which form rims of 100-nm in thickness at the interface between organic matter and Fe-sulphides may result from metamorphic processes. This study illustrates that it may be possible in some instances to deconvolve metamorphic from diagenetic imprints and opens new avenues to better constrain processes that may allow the preservation of organic fossils during diagenesis and metamorphism.

  8. The pyrite-type high-pressure form of FeOOH (United States)

    Nishi, Masayuki; Kuwayama, Yasuhiro; Tsuchiya, Jun; Tsuchiya, Taku


    Water transported into Earth’s interior by subduction strongly influences dynamics such as volcanism and plate tectonics. Several recent studies have reported hydrous minerals to be stable at pressure and temperature conditions representative of Earth’s deep interior, implying that surface water may be transported as far as the core-mantle boundary. However, the hydrous mineral goethite, α-FeOOH, was recently reported to decompose under the conditions of the middle region of the lower mantle to form FeO2 and release H2, suggesting the upward migration of hydrogen and large fluctuations in the oxygen distribution within the Earth system. Here we report the stability of FeOOH phases at the pressure and temperature conditions of the deep lower mantle, based on first-principles calculations and in situ X-ray diffraction experiments. In contrast to previous work suggesting the dehydrogenation of FeOOH into FeO2 in the middle of the lower mantle, we report the formation of a new FeOOH phase with the pyrite-type framework of FeO6 octahedra, which is much denser than the surrounding mantle and is stable at the conditions of the base of the mantle. Pyrite-type FeOOH may stabilize as a solid solution with other hydrous minerals in deeply subducted slabs, and could form in subducted banded iron formations. Deep-seated pyrite-type FeOOH eventually dissociates into Fe2O3 and releases H2O when subducted slabs are heated at the base of the mantle. This process may cause the incorporation of hydrogen into the outer core by the formation of iron hydride, FeHx, in the reducing environment of the core-mantle boundary.

  9. Iron pyrite thin films synthesized from an Fe(acac)3 ink. (United States)

    Seefeld, Sean; Limpinsel, Moritz; Liu, Yu; Farhi, Nima; Weber, Amanda; Zhang, Yanning; Berry, Nicholas; Kwon, Yon Joo; Perkins, Craig L; Hemminger, John C; Wu, Ruqian; Law, Matt


    Iron pyrite (cubic FeS2) is a promising candidate absorber material for earth-abundant thin-film solar cells. Here, we report on phase-pure, large-grain, and uniform polycrystalline pyrite films that are fabricated by solution-phase deposition of an iron(III) acetylacetonate molecular ink followed by sequential annealing in air, H2S, and sulfur gas at temperatures up to 550 °C. Phase and elemental compositions of the films are characterized by conventional and synchrotron X-ray diffraction, Raman spectroscopy, Auger electron spectroscopy, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy (XPS). These solution-deposited films have more oxygen and alkalis, less carbon and hydrogen, and smaller optical band gaps (E(g) = 0.87 ± 0.05 eV) than similar films made by chemical vapor deposition. XPS is used to assess the chemical composition of the film surface before and after exposure to air and immersion in water to remove surface contaminants. Optical measurements of films rich in marcasite (orthorhombic FeS2) show that marcasite has a band gap at least as large as pyrite and that the two polymorphs share similar absorptivity spectra, in excellent agreement with density functional theory models. Regardless of the marcasite and elemental impurity contents, all films show p-type, weakly activated transport with curved Arrhenius plots, a room-temperature resistivity of ~1 Ω cm, and a hole mobility that is too small to measure by Hall effect. This universal electrical behavior strongly suggests that a common defect or a hole-rich surface layer governs the electrical properties of most FeS2 thin films.

  10. Evolution of biofilms during the colonization process of pyrite by Acidithiobacillus thiooxidans. (United States)

    González, Dulce M; Lara, René H; Alvarado, Keila N; Valdez-Pérez, Donato; Navarro-Contreras, Hugo R; Cruz, Roel; García-Meza, Jessica Viridiana


    We have applied epifluorescence principles, atomic force microscopy, and Raman studies to the analysis of the colonization process of pyrite (FeS(2)) by sulfuroxidizing bacteria Acidithiobacillus thiooxidans after 1, 15, 24, and 72 h. For the stages examined, we present results comprising the evolution of biofilms, speciation of S (n) (2-) /S(0) species, adhesion forces of attached cells, production and secretion of extracellular polymeric substances (EPS), and its biochemical composition. After 1 h, highly dispersed attached cells in the surface of the mineral were observed. The results suggest initial non-covalent, weak interactions (e.g., van der Waal's, hydrophobic interactions), mediating an irreversible binding mechanism to electrooxidized massive pyrite electrode (eMPE), wherein the initial production of EPS by individual cells is determinant. The mineral surface reached its maximum cell cover between 15 to 24 h. Longer biooxidation times resulted in the progressive biofilm reduction on the mineral surface. Quantification of attached cell adhesion forces indicated a strong initial mechanism (8.4 nN), whereas subsequent stages of mineral colonization indicated stability of biofilms and of the adhesion force to an average of 4.2 nN. A variable EPS (polysaccharides, lipids, and proteins) secretion at all stages was found; thus, different architectural conformation of the biofilms was observed during 120 h. The main EPS produced were lipopolysaccharides which may increase the hydrophobicity of A. thiooxidans biofilms. The highest amount of lipopolysaccharides occurred between 15-72 h. In contrast with abiotic surfaces, the progressive depletion of S (n) (2-) /S(0) was observed on biotic eMPE surfaces, indicating consumption of surface sulfur species. All observations indicated a dynamic biooxidation mechanism of pyrite by A. thiooxidans, where the biofilms stability and composition seems to occur independently from surface sulfur species depletion.

  11. Inertization of pyrite cinders and co-inertization with electric arc furnace flue dusts by pyroconsolidation at solid state. (United States)

    Viñals, J; Balart, M J; Roca, A


    The viability of a pyroconsolidation process to render pyrite cinders inert and to co-inert pyrite cinders with a hazardous polymetallic residue such as electric arc furnace flue dusts (EAF) containing Pb, Cu, Zn, As, Cr, Ni and Mo were investigated. The effects of pyroconsolidation temperature (800-1200 degrees C), milling pyrite cinders and additions of both CaO and EAF on the resulting microstructure of the pellets were determined. The microstructural changes were then compared with the results of the standard leaching tests. Full inertization of pyrite cinders was achieved after milling to < 100 micron followed by a pelletization and pyroconsolidation process at a temperature of 1200 degrees C. This process also allows co-inertization of pyrite cinders with controlled additions of EAF (up to approximately to 10%). Following pyroconsolidation at 1200 degrees C, the metallic elements were inert components in the four main phases: traces of Cr in hematite; Cr, Cu, Zn and Ni in spinel-phase; traces of Cr and Zn in calcium ferrites; and Pb and traces of Cu, Zn and Ba in K-Ca-Al-Fe glassy silicate.

  12. Surficial phase-identification and structural profiles from weathered natural pyrites: A grazing-incidence X-ray diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Cai Yuanfeng [State Key Laboratory of Mineral Deposits Research, Nanjing 210093 (China); Department of Earth Sciences, Nanjing University, Nanjing 210093 (China)], E-mail:; Pan, Yuguan [State Key Laboratory of Mineral Deposits Research, Nanjing 210093 (China); Xue Jiyue; Su Guizhen [Department of Earth Sciences, Nanjing University, Nanjing 210093 (China)


    Five pyrites with original crystal face (1 0 0) with different tarnish colours were selected from one pyrite-bearing ore sample from Tongling multi-metal deposit, Anhui, China. They are henna mottled with dark violet, yellow mottled with red, yellow, blue mottled with violet and reddish brown in surface colour. Grazing-incidence X-ray diffractometry (GIXRD) was used to study the phases formed or precipitated on the surface of pyrite (1 0 0) face during chemical weathering. By changing the incident angle, GIXRD can provide information on the changes in the mineral phases from the surface as a function of depth. Products formed or precipitated on the surface of pyrite (1 0 0) face are one or several sulfur or iron-bearing hydrated oxides and include gypsum, jalpaite, goethite, goldichite. The sulfur-bearing minerals present on the surface imply the oxidation of sulfur to sulfate, or the reduction of sulfur to sulfide. By analyzing a series of GIXRD patterns obtained at different angles of incidence for a single pyrite, the mineral assemblage differs from the surface into the body of the crystal. Taking the reddish brown sample as an example, four diffraction profiles at 2.575, 2.2105, 1.9118 and 1.613 A are present in the pattern of a 2{sup o} incident angle experiment whereas they cannot be found at a GIXRD angle smaller than 0.6{sup o}.

  13. Influence of Sulfobacillus thermosulfidooxidans on Initial Attachment and Pyrite Leaching by Thermoacidophilic Archaeon Acidianus sp. DSM 29099

    Directory of Open Access Journals (Sweden)

    Jing Liu


    Full Text Available At the industrial scale, bioleaching of metal sulfides includes two main technologies, tank leaching and heap leaching. Fluctuations in temperature caused by the exothermic reactions in a heap have a pronounced effect on the growth of microbes and composition of mixed microbial populations. Currently, little is known on the influence of pre-colonized mesophiles or moderate thermophiles on the attachment and bioleaching efficiency by thermophiles. The objective of this study was to investigate the interspecies interactions of the moderate thermophile Sulfobacillus thermosulfidooxidans DSM 9293T and the thermophile Acidianus sp. DSM 29099 during initial attachment to and dissolution of pyrite. Our results showed that: (1 Acidianus sp. DSM 29099 interacted with S. thermosulfidooxidansT during initial attachment in mixed cultures. In particular, cell attachment was improved in mixed cultures compared to pure cultures alone; however, no improvement of pyrite leaching in mixed cultures compared with pure cultures was observed; (2 active or inactivated cells of S. thermosulfidooxidansT on pyrite inhibited or showed no influence on the initial attachment of Acidianus sp. DSM 29099, respectively, but both promoted its leaching efficiency; (3 S. thermosulfidooxidansT exudates did not enhance the initial attachment of Acidianus sp. DSM 29099 to pyrite, but greatly facilitated its pyrite dissolution efficiency. Our study provides insights into cell-cell interactions between moderate thermophiles and thermophiles and is helpful for understanding of the microbial interactions in a heap leaching environment.

  14. Selenium, tellurium and precious metal mineralogy in Uchalinsk copper-zinc-pyritic district, the Urals (United States)

    Vikentev, I.


    During processing the most of Au, Ag, Se, Te, Pb, Bi, Sb, Hg as well as notable part of Cu, Zn and Cd fail for tailings and became heavy metal pollutants. Modes of occurrence of Au, Ag, Te and Se covers two giant VMS deposits: Uchaly (intensively deformed) and Uzelginsk (altered by late hydrothermal processes) as well as middle-sized Molodezn and West Ozern deposits (nondeformed) have been studied. Mineral forms of these elements as well as their presence in disperse mode in common ore minerals (pyrite, chalcopyrite, sphalerite) have been studied using SEM, EPMA, INAA, ICP-MS and LA-ICP-MS.

  15. Synthesis, characterization and processing of cubic iron pyrite nanocrystals in a photovoltaic cell

    Energy Technology Data Exchange (ETDEWEB)

    Alam Khan, M., E-mail:; Sarker, J.C.; Lee, Seunyong; Mangham, Scott C.; Manasreh, M.O.


    Cubic iron pyrite (fool's gold) nanocrystals with an average diameter of ∼60 nm were grown in an oleylamine ligand which acts as a solvent and surfactant without the utilization of alkyl phosphine and phosphonic acids at 230 °C in a Schlenk flask. For the first time photoluminescence properties of such cubic nanocrystals were analyzed at 77 K, showing band gaps of 1.71 eV. However, UV–Vis spectra shows a band gap of 1.41 eV for the same nanocrystals, close to the direct band gap (1.38 eV) of reported pyrite materials. The discrepancy of 0.3 eV in absorption (UV–Vis) and emission spectra (PL) are attributed to the phonon coupling (stokes shift). The prepared cubic nanocrystals were well suited for an inexpensive thin film solar cells and further processed and spin casted with a synthesized CdSe quantum dots in chloroform solvent as a bulk-heterojunction (BHJ) solar cell in order to get photovoltaic responses in real devices. We successfully report here an efficiency of 0.5% with the J{sub SC} of 3.7 mA/cm{sup −2} and V{sub OC} of 0.16 mV with a cell structure of ITO/PEDOT:PSS/FeS{sub 2}:CdSe/Au. The morphology and optoelectronic properties are elucidated by SEM, TEM, TEM-EDS, XRD, micro-Raman spectra, IV curve and micro-PL techniques. - Highlights: • Excellent cubic iron pyrite nanocrystals are synthesized by using an oleylamine ligand. • First time PL spectra were used to measure band gaps of such colloidal cubic nanocrytsals. • Pyrite ink was made in suitable solvent to fabricate practical devices. • A successful 0.5% efficiency is reported in bulk-heterojunction cell with CdSe QDs.

  16. Degree of trace metal pyritization in sediments from the Pacific coast of Baja California, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Nava Lopez, Carmen; Huerta Diaz, Miguel Angel [Instituto de Investigaciones Oceanologicas, Ensenada, Baja California (Mexico)


    We analyzed sediments from a core collected on the Pacific coast of Baja California, 45 km off the city of Tijuana and at 1257 m water depth (32 Celsius degrees 9.5N , 117 Celsius degrees 8.3W), for trace metal content in two operationally-defined fractions, HCl and pyrite. Our results indicate transference of Cu>Ni>Zn>>Hg y Ag from the HCl to the pyrite fraction. Sediments have degrees of pyritization (DOP) that average 7.2{+-} 4.9% with a maximum value of 18.5%. Average degrees of trace metal pyritization (DTMP) range from 6.2 {+-}2.1% to 83{+-} 8% for Mn and Hg, respectively, although maximum values for some metals were closed to 100%. This transference is apparently a function of the solubility products of metal sulfides and the relative abundances of metals in the HCl fraction, as suggested by the significant correlation (p<0.001) observed between these two parameters and the DTMP of a number of trace metals. A similar correlation was obtained from published data of two cores collected in the Gulf of Mexico. [Spanish] Se analizaron sedimentos de un nucleo recolectado en la costa del Pacifico de Baja California 45 km de la costa de la ciudad de Tijuana y a 1257 m de profundidad del agua (32 grados Celsius 9.5N, 117 grados Celsius 8.3W), para determinar su contenido de metales traza en dos fracciones operacionales definidas HCl y pirita. Los resultados indican una transferencia de Cu>Ni>Zn>>Hg y Ag de la fraccion de HCl a la fase piritica. Los grados de piritizacion (DOP) en los sedimentos promediaron 7.2{+-} 4.9%, con un valor maximo de 18.5%. Los valores promedio de los grados de piritizacion de metales traza (DTMP) abarcaron el intervalo de 6.2 {+-}2.1% a 83{+-}18% para Mn y Hg, respectivamente, aunque los valores maximos para algunos metales estuvieron cercanos al 100%. Esta transferencia aparentemente es funcion de los productos de solubilidad de los sulfuros metalicos y de la abundancia relativa de metales en la fraccion HCl, como sugiere la correlacion

  17. Determination of the Content of Heavy Metals in Pyrite Contaminated Soil and Plants

    Directory of Open Access Journals (Sweden)

    Miroslava Marić


    Full Text Available Determination of a pyrite contaminated soil texture, content of heavy metals in the soil and soil pH, was the aim in the investigation. Acidification of damaged soil was corrected by calcium carbonate. Mineral nutrients and organic matter (NPK, dung, earthworm cast, straw and coal dust were added to damaged soil. Afterwards, the soil was used for oat production. Determination of total heavy metal contents (Cu, Pb, Zn, Fe in soil was performed by atomic absorption spectrofotometry. Plant material (stems, seeds was analysed, too. Total concentration of the heavy metals in the plant material were greater than in crop obtained in unaffected soil.

  18. The effect of rehabilitation on the rate of oxidation of pyrite in a mine waste rock dump. (United States)

    Harries, J R; Ritchie, A I


    Temperature profiles within a mine waste rock dump undergoing pyritic oxidation have been used to estimate the rate of oxidation and the sites where oxidation was occurring. The waste rock dump is located at the abandoned Rum Jungle mine site in Northern Australia and was a major source of pollution to the local river system. The dump was rehabilitated in 1983-84 by reshaping to reduce erosion and covering with clay and soil to reduce infiltration of water.Heat source distributions were derived from temperature profiles measured in the dump. The oxidation of pyritic material is the main cause of heat in the dump, hence the rate and location of oxidation can be obtained from the distribution of heat sources. A comparison of the heat source distributions before and after rehabilitation showed that rehabilitation greatly reduced or stopped the oxidation of pyrite in the dump.

  19. Archaeal diversity and the extent of iron and manganese pyritization in sediments from a tropical mangrove creek (Cardoso Island, Brazil) (United States)

    Otero, X. L.; Lucheta, A. R.; Ferreira, T. O.; Huerta-Díaz, M. A.; Lambais, M. R.


    Even though several studies on the geochemical processes occurring in mangrove soils and sediments have been performed, information on the diversity of Archaea and their functional roles in these ecosystems, especially in subsurface environments, is scarce. In this study, we have analyzed the depth distribution of Archaea and their possible relationships with the geochemical transformations of Fe and Mn in a sediment core from a tropical mangrove creek, using 16S rRNA gene profiling and sequential extraction of different forms of Fe and Mn. A significant shift in the archaeal community structure was observed in the lower layers (90-100 cm), coinciding with a clear decrease in total organic carbon (TOC) content and an increase in the percentage of sand. The comparison of the archaeal communities showed a dominance of methanogenic Euryarchaeota in the upper layers (0-20 cm), whereas Crenarchaeota was the most abundant taxon in the lower layers. The dominance of methanogenic Euryarchaeota in the upper layer of the sediment suggests the occurrence of methanogenesis in anoxic microenvironments. The concentrations of Fe-oxyhydroxides in the profile were very low, and showed positive correlation with the concentrations of pyrite and degrees of Fe and Mn pyritization. Additionally, a partial decoupling of pyrite formation from organic matter concentration was observed, suggesting excessive Fe pyritization. This overpyritization of Fe can be explained either by the anoxic oxidation of methane by sulfate and/or by detrital pyrite tidal transportation from the surrounding mangrove soils. The higher pyritization levels observed in deeper layers of the creek sediment were also in agreement with its Pleistocenic origin.

  20. Electrochemical mineralization of the antibiotic levofloxacin by electro-Fenton-pyrite process. (United States)

    Barhoumi, Natija; Labiadh, Lazhar; Oturan, Mehmet A; Oturan, Nihal; Gadri, Abdellatif; Ammar, Salah; Brillas, Enric


    Levofloxacin is a large spectrum antibiotic from fluoroquinolones family, widely used and detected in natural waters. Here, this drug was degraded by a novel heterogeneous electro-Fenton (EF) process, so-called EF-pyrite, in which pyrite powder in suspension regulates the solution pH to 3.0 and supplies 0.2mM Fe(2+) as catalyst to the solution. Trials were performed with a stirred boron-doped diamond (BDD)/carbon-felt cell under O2 bubbling for cathodic H2O2 generation. Hydroxyl radicals formed from water oxidation at the BDD anode and in the bulk from Fenton's reaction between Fe(2+) and H2O2 were the main oxidizing agents. The effect of applied current and antibiotic concentration over the mineralization rate and degree, mineralization current efficiency and specific energy consumption was studied. An almost total mineralization was achieved for a 0.23mM drug solution operating at 300mA for 8h. The kinetic decay of the drug was followed by reversed-phase HPLC and obeyed a pseudo-first-order reaction. Ion-exclusion HPLC analysis of treated solutions revealed that oxalic and oxamic acids, the most persistent final products, were the predominant pollutants remaining in solution at long electrolysis time. Ion chromatography analysis confirmed the release of F(-), NO3(-) and NH4(+) ions during levofloxacin mineralization. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Efficient hydrogen evolution catalysis using ternary pyrite-type cobalt phosphosulphide

    KAUST Repository

    Cabán-Acevedo, Miguel


    The scalable and sustainable production of hydrogen fuel through water splitting demands efficient and robust Earth-abundant catalysts for the hydrogen evolution reaction (HER). Building on promising metal compounds with high HER catalytic activity, such as pyrite structure cobalt disulphide (CoS 2), and substituting non-metal elements to tune the hydrogen adsorption free energy could lead to further improvements in catalytic activity. Here we present a combined theoretical and experimental study to establish ternary pyrite-type cobalt phosphosulphide (CoPS) as a high-performance Earth-abundant catalyst for electrochemical and photoelectrochemical hydrogen production. Nanostructured CoPS electrodes achieved a geometrical catalytic current density of 10 mA cm at overpotentials as low as 48mV, with outstanding long-term operational stability. Integrated photocathodes of CoPS on n -p-p silicon micropyramids achieved photocurrents up to 35 mA cm at 0 V versus the reversible hydrogen electrode (RHE), onset photovoltages as high as 450 mV versus RHE, and the most efficient solar-driven hydrogen generation from Earth-abundant systems.

  2. Sulfidation Roasting of Hemimorphite with Pyrite for the Enrichment of Zn and Pb (United States)

    Min, Xiao-Bo; Xue, Ke; Ke, Yong; Zhou, Bo-Sheng; Li, Yang-Wen-Jun; Wang, Qing-Wei


    With the increasing consumption of zinc and the depletion of zinc sulfide ores, the exploitation of low-grade zinc oxide ores may be important for the sustainability of the zinc industry. Hemimorphite, a zinc hydroxyl silicate hydrate, is a significant source of Zn and Pb. It is difficult to obtain Zn and Pb from the hemimorphite using traditional technology. In this work, for the first time, sulfidation roasting of hemimorphite with pyrite was studied for the enrichment of Zn and Pb by a flotation process. Four stages of sulfidation roasting were determined based on x-ray diffraction and thermogravimetry analysis. Then, the effects of sulfidation temperature, pyrite dosage and reaction time on the sulfidation percentages were investigated at the laboratory scale. The experimental results showed that the sulfidation percentages of Pb and Zn were as high as 98.08% and 90.55% under optimum conditions, respectively. Finally, a flotation test was performed to enrich Zn and Pb in the sulfidation product. A flotation concentrate with 8.78% Zn and 9.25% Pb was obtained, and the recovery of Zn and Pb reached 56.14% and 75.94%, respectively.

  3. An experimental study of pyrite bio-leaching as a way to control spontaneous combustion

    Institute of Scientific and Technical Information of China (English)

    Yin Shenghua; Wu Aixiang; Liu Jinzhi; Huang Mingqing; Wang Hongjiang


    Bio-leaching of pyrite by native strains of acidophilic bacteria was examined by laboratory scale tests.Three groups of batch trials in agitated flasks and three continuous column leaching tests were performed.The leaching ability and efficiency of native bacteria was greatly improved by adaptation of the bacteria to the test conditions.These cultivated bacteria were then used for the leaching process.The changes in solution pH,Eh,Fe2+ concentration,and sulfate ion concentration were monitored throughout the tests.A portion of the pyritic sulfur is transformed into soluble sulfate ion.The desulfurization ratio of 42.6% was obtained in a flask shaking test and a ratio of 39.4% was obtained during column leaching.A weight gain test was performed on leached and unleached samples by exposing the samples to humid air for several days.A smaller weight gain of the bio-leached samples indicates that removing sulfur from the sulphide ore helps reduce its oxidation rate and the potential for spontaneous combustion.

  4. A novel magnetic 4A zeolite adsorbent synthesised from kaolinite type pyrite cinder (KTPC) (United States)

    Wang, Weiqing; Feng, Qiming; Liu, Kun; Zhang, Guofan; Liu, Jing; Huang, Yang


    As a solid waste, kaolinite type pyrite cinder (KTPC) is a special pyrite cinder, its mineral components include metakaolin and magnetite, and the chemical compositions of these minerals include SiO2, Al2O3, FeO and Fe2O3. In this study, a novel magnetic 4A zeolite adsorbent was synthesised from KTPC using the hydrothermal method, and the optimum hydrothermal synthesis conditions were investigated using X-ray diffraction (XRD) and by determining the specific surface area (SSA) and the saturated cation exchange adsorption capacity (SCEAC) to Cs+. Under the optimum hydrothermal synthesis conditions, the magnetic 4A zeolite adsorbent can be synthesised with high crystallinity, and the SSA and SCEAC to Cs+ are 24.49 m2/g and 106.63 mg/g, respectively. The further characterisations of pore size distribution, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), thermogravimetry-derivative thermogravimetry-differential thermal analysis (TG-DTG-DTA), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM) were performed. The results revealed that magnetic particles are coated onto the zeolite surface and further form magnetic aggregates, and the existing magnetic particles in KTPC do not change their crystal structure and do not affect the synthesis of the 4A zeolite. In addition, the synthesised 4A zeolite adsorbent can be used as a magnetic adsorbent in wastewater treatment with high magnetic sensitivity and is thermally stable up to approximately 900 °C.

  5. Bacterial communities involved in soil formation and plant establishment triggered by pyrite bioweathering on arctic moraines. (United States)

    Mapelli, Francesca; Marasco, Ramona; Rizzi, Agostino; Baldi, Franco; Ventura, Stefano; Daffonchio, Daniele; Borin, Sara


    In arctic glacier moraines, bioweathering primed by microbial iron oxidizers creates fertility gradients that accelerate soil development and plant establishment. With the aim of investigating the change of bacterial diversity in a pyrite-weathered gradient, we analyzed the composition of the bacterial communities involved in the process by sequencing 16S rRNA gene libraries from different biological soil crusts (BSC). Bacterial communities in three BSC of different morphology, located within 1 m distance downstream a pyritic conglomerate rock, were significantly diverse. The glacier moraine surrounding the weathered site showed wide phylogenetic diversity and high evenness with 15 represented bacterial classes, dominated by Alphaproteobacteria and pioneer Cyanobacteria colonizers. The bioweathered area showed the lowest diversity indexes and only nine bacterial families, largely dominated by Acidobacteriaceae and Acetobacteraceae typical of acidic environments, in accordance with the low pH of the BSC. In the weathered BSC, iron-oxidizing bacteria were cultivated, with counts decreasing along with the increase of distance from the rock, and nutrient release from the rock was revealed by environmental scanning electron microscopy-energy dispersive X-ray analyses. The vegetated area showed the presence of Actinomycetales, Verrucomicrobiales, Gemmatimonadales, Burkholderiales, and Rhizobiales, denoting a bacterial community typical of developed soils and indicating that the lithoid substrate of the bare moraine was here subjected to an accelerated colonization, driven by iron-oxidizing activity.

  6. 内蒙古苏尼特右旗毕力赫大型斑岩型金矿床辉钼矿Re-Os同位素年龄及其地质意义%Molybdnite Re-Os isotope age of Bilihe large-size porphyry gold deposit in Sunid Right Banner of Inner Mongolia and its geological significance

    Institute of Scientific and Technical Information of China (English)

    卿敏; 葛良胜; 唐明国; 屈文俊; 袁士松; 赵玉锁


    between hypo-volcanic complex body and overlying volcanic rocks as well as volcanic clastic rocks, especially in the inner-contact zone. It is the first time that a large-sized porphyry gold deposit was found in the northern margin of North China plate, i.e., the Bilihe large-size porphyry gold deposit in Sunid Right Banner of Inner Mongolia. In order to identify the porphyry gold (copper) metallogenic age, the authors used Re-Os isotope to test 6 molybdnite samples collected from the porphyry, which yielded the isochron age of (272.7 ± 1.6) Ma (MSWD = 0.57). Redefinition of the late Paleozoic ore-forming geological event of the Bilihe gold deposit has provided new evidence for the convergent plate structural system in the northern part of North China in late Paleozoic, recognized some basic geological problems of the northern part of North China, and given enlightenments in search for low temperature shallow-seated porphyry gold-polymetallic deposits in the magmatic arc environment of the middle-east segments of the Central Asian Orogenic Belt in late Paleozoic.

  7. Investigation by sup 5 sup 7 Fe- Moessbauer spectroscopy of some pyrite samples of different Romanian natural deposits

    CERN Document Server

    Constantinescu, S; Calogero, S


    Extracted pyrites from four Romanian geological deposits have been investigated by Moessbauer spectroscopy. The room temperature results of this investigation have been correlated with the data of sulfur isotope ratio and minor elements analysis of pyrite samples. The presence of three signals is identified in the Moessbauer spectra. They correspond to the two crystalline structure of FeS sub 2 while the third is suggested to be assigned to one of the components of the iron-sulfur-arsenic series of investigated minerals. (authors)

  8. Cretaceous Cu-Au, pyrite, and Fe-oxide-apatite deposits in the Ningwu basin, Lower Yangtze Area, Eastern China (United States)

    Yu, Jin-Jie; Lu, Bang-Cheng; Wang, Tie-Zhu; Che, Lin-Rui


    The Cretaceous Ningwu volcanic basin of the Middle and Lower Yangtze River Valley metallogenic belt of eastern China hosts numerous Fe-oxide-apatite, Cu-Au, and pyrite deposits. The mineralization in the Ningwu basin is associated with subvolcanic rocks, consisting of gabbro-diorite porphyry and/or pyroxene diorite. However, the mineralization is associated with subvolcanic and volcanic rock suite belonging to the Niangniangshan Formation in the Tongjing Cu-Au deposit, including nosean-bearing aegirine-augite syenites, quartz syenites, and quartz monzonites. The zoning displayed by the alteration and mineralization comprises: (1) an upper light-colored zone of argillic, carbonate, and pyrite alteration and silicification that is locally associated with pyrite and gold mineralization, (2) a central dark-colored zone of diopside, fluorapatite-magnetite, phlogopite, and garnet alteration associated with fluorapatite-magnetite mineralization, and (3) a lowermost light-colored zone of extensive albite alteration. The Cu-Au and pyrite orebodies are peripheral to the Fe-oxide-apatite deposits in this area and overlie the iron orebodies, including the Meishan Cu-Au deposit in the northern Ningwu basin and the pyrite deposits in the central Ningwu basin. The δ34S values of sulfides from the Fe-oxide-apatite, Cu-Au, and pyrite deposits in the Ningwu basin show large variation, with a mixed sulfur source, including magmatic sulfur and/or a mixture of sulfur derived from a magmatic component, country rock, and thermochemical reduction of sulfate at 200-300 °C. The ore-forming fluids associated with iron mineralization were derived mainly from magmatic fluids, and the late-stage ore-forming fluids related to Cu-Au and pyrite mineralization may have formed by the introduction of cooler meteoric water to the system. The Fe-oxide-apatite, Cu-Au, and pyrite deposits of the Ningwu basin formed in an extensional environment and are associated with a large-scale magmatic

  9. S/Se ratio of pyrite from eastern Australian VHMS deposits: implication of magmatic input into volcanogenic hydrothermal systems

    Energy Technology Data Exchange (ETDEWEB)

    Huston, D.L. [Geological Survey of Canada, Ottawa, ON (Canada); Sie, S.H.; Suter, G.F. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience; Cooke, D.R. [Tasmania Univ., Sandy Bay, TAS (Australia)


    The proton microprobe was used to determine the concentrations of over twenty trace elements in pyrite grains from four volcanic-hosted massive sulphide (VHMS) deposits in eastern Australia. Of the elements determined, Se has the most potential in resolving important problems in the genesis of this class of ore deposits. This paper summarises analytical conditions, describes the distribution of Se in pyrite in VHMS deposits as determined in this and other studies, discusses the speciation of Se in hydrothermal fluids, and presents a genetic model on the relative contribution of magmatic versus sea water Se (and S) in VHMS systems. 2 refs., 1 fig.

  10. Degradation of tyrosol by a novel electro-Fenton process using pyrite as heterogeneous source of iron catalyst. (United States)

    Ammar, Salah; Oturan, Mehmet A; Labiadh, Lazhar; Guersalli, Amor; Abdelhedi, Ridha; Oturan, Nihal; Brillas, Enric


    Tyrosol (TY) is one of the most abundant phenolic components of olive oil mill wastewaters. Here, the degradation of synthetic aqueous solutions of 0.30 mM TY was studied by a novel heterogeneous electro-Fenton (EF) process, so-called EF-pyrite, in which pyrite powder was the source of Fe(2+) catalyst instead of a soluble iron salt used in classical EF. Experiments were performed with a cell equipped with a boron-doped diamond anode and a carbon-felt cathode, where TY and its products were destroyed by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between Fe(2+) and H2O2 generated at the cathode. Addition of 1.0 g L(-1) pyrite provided an easily adjustable pH to 3.0 and an appropriate 0.20 mM Fe(2+) to optimize the EF-pyrite treatment. The effect of current on mineralization rate, mineralization current efficiency and specific energy consumption was examined under comparable EF and EF-pyrite conditions. The performance of EF-pyrite was 8.6% superior at 50 mA due to self-regulation of soluble Fe(2+) by pyrite. The TY decay in this process followed a pseudo-first-order kinetics. The absolute rate constant for TY hydroxylation was 3.57 × 10(9) M(-1) s(-1), as determined by the competition kinetics method. Aromatic products like 3,4-dihydroxyphenylethanol, 4-hydroxyphenylacetic acid, 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid and catechol, as well as o-benzoquinone, were identified by GC-MS and reversed-phase HPLC. Short-chain aliphatic carboxylic acids like maleic, glycolic, acetic, oxalic and formic were quantified by ion-exclusion HPLC. Oxalic acid was the major and most persistent product found. Based on detected intermediates, a plausible mineralization pathway for TY by EF-pyrite was proposed.

  11. Abiotic oxidation of pyrite by Fe(III) in acidic media and its implications for sulfur isotope measurements of lattice-bound sulfate in sediments

    Digital Repository Service at National Institute of Oceanography (India)

    Mazumdar, A.; Goldberg, T.; Strauss, H

    from our pure pyrite oxidation experiments show that in a solution of acidic pH, the amount of sulfate formed is very similar under both oxygenated and oxygen-free experimental conditions which is suggestive of the dominant role of Fe sup(3+) in pyrite...

  12. ID-TIMS Geochronology of ca 1 Ma leucogranites from the core of Nanga Parbat (United States)

    Bowring, S. A.; Searle, M. P.; Waters, D. J.; Hodges, K. V.; Schmitz, M. D.; Crowley, J.


    Although isotope-dilution, themal-ioniaztion mass spectrometry (ID-TIMS) is the most precise method available for U-Th-Pb geochronology of accessory minerals, the technique is traditionally not applied to samples youger than ca. 10 Ma due to low concentrations of radiogenic Pb. However, recent analytical advances allow the routine measurement of less than 5-10 picograms of radiogenic Pb, and the reduction of laboratory blanks to extremely low levels. As a consequence, it is now possible to use ID-TIMS for U-Pb geochronology of very young accessory mineral suites to develop new insights regarding the time scales and patterns of inheritance, melt production, and segregation in collisional orogens. The Nanga Parbat syntaxis of the northwestern Himalaya has had a long and complex thermal history, but it is famous for the evidence it provides for extremely young (Nanga Parbat in less than 1 million years.

  13. Provisional zircon and monazite uranium-lead geochronology for selected rocks from Vermont (United States)

    Aleinikoff, John N.; Ratcliffe, Nicholas M.; Walsh, Gregory J.


    This report presents the results of zircon and monazite uranium-lead (U-Pb) geochronologic analyses of 24 rock samples. The samples in this study were collected from mapped exposures identified while conducting either new, detailed (1:24,000-scale) geologic quadrangle mapping or reconnaissance mapping, both of which were used for compilation of the bedrock geologic map of Vermont. All of the collected samples were judged to be igneous rocks (either intrusive or extrusive) on the basis of field relations and geochemistry. The one exception is the Okemo Quartzite on Ludlow Mountain. These geochronologic data were used to supplement regional correlations between igneous suites on the basis of similar geochemistry and geologic mapping.

  14. The Potassium-Argon Laser Experiment (KArLE): In Situ Geochronology for Planetary Robotic Missions (United States)

    Cohen, Barbara


    The Potassium (K) - Argon (Ar) Laser Experiment (KArLE) will make in situ noble-gas geochronology measurements aboard planetary robotic landers and roverss. Laser-Induced Breakdown Spectroscopy (LIBS) is used to measure the K abun-dance in a sample and to release its noble gases; the evolved Ar is measured by mass spectrometry (MS); and rela-tive K content is related to absolute Ar abundance by sample mass, determined by optical measurement of the ablated volume. KArLE measures a whole-rock K-Ar age to 10% or better for rocks 2 Ga or older, sufficient to resolve the absolute age of many planetary samples. The LIBS-MS approach is attractive because the analytical components have been flight proven, do not require further technical development, and provide complementary measurements as well as in situ geochronology.

  15. Geochronology of Cenozoic rocks in the Bodie Hills, California and Nevada (United States)

    Fleck, Robert J.; du Bray, Edward A.; John, David A.; Vikre, Peter G.; Cosca, Michael A.; Snee, Lawrence W.; Box, Stephen E.


    The purpose of this report is to present geochronologic data for unaltered volcanic rocks, hydrothermally altered volcanic rocks, and mineral deposits of the Miocene Bodie Hills and Pliocene to Pleistocene Aurora volcanic fields of east-central California and west-central Nevada. Most of the data presented here were derived from samples collected between 2000–13, but some of the geochronologic data, compiled from a variety of sources, pertain to samples collected during prior investigations. New data presented here (tables 1 and 2; Appendixes 1–3) were acquired in three U.S. Geological Survey (USGS) 40Ar/39Ar labs by three different geochronologists: Robert J. Fleck (Menlo Park, CA), Lawrence W. Snee (Denver, CO), and Michael A. Cosca (Denver, CO). Analytical methods and data derived from each of these labs are presented separately.

  16. 某矿山硫铁矿尾砂浮选试验研究%Study on the flotation test of pyrite tailings from a pyrite mine

    Institute of Scientific and Technical Information of China (English)

    王淑红; 董风芝; 孙永峰


    在对试验用硫铁矿尾砂进行物理化学性质研究的基础上,对其进行浮选试验.以乙黄药为捕收剂,2号油为起泡剂,经过一粗一扫一精闭路试验,一次精选尾矿和扫选精矿合并返回粗选可以得到精矿品位41.07%、回收率92.73%、产率10.95%、尾矿品位0.4%的最终指标.%Flotation test was conducted on the basis of the study on physical and chemical characteristics of the tailings from pyrite ores.With ethylxanthate as collector and 2# oil as frother, roughing was under way in alkaline slurry with one roughing and one concentrating ,and the final indexes of concentrate grade of 41.07%, recovery rateof 92.73%, yield of 10.95% and grade of railings 0.4% are obtained.

  17. Small-Volume U-Pb Zircon Geochronology by Laser Ablation-Multicollector-ICP-MS (United States)


    detrital and metamorphic history of a granulite -facies paragneiss — demonstrate the utility of this technique to a variety of geologic problems and confirm... granulite -facies pelitic gneiss collected inn geochronology by laser ablation-multicollector-ICP-MS, Chemical Fig. 11. A) Concordia plot of all...zircons to unravel the detrital–metamorphic history of a granulite -facies paragneiss from east Greenland. In addition to the small spot diameter, the

  18. The Potassium-Argon Laser Experiment (karle): In Situ Geochronology for Planetary Missions (United States)

    Cohen, B. A.


    Isotopic dating is an essential tool to establish an absolute chronology for geological events. It enables a planet's crystallization history, magmatic evolution, and alteration to be placed into the framework of solar system history. The capability for in situ geochronology will open up the ability for this crucial measurement to be accomplished as part of lander or rover complement. An in situ geochronology package can also complement sample return missions by identifying the most interesting rocks to cache or return to Earth. Appropriate application of in situ dating will enable geochronology on more terrains than can be reached with sample-return missions to the Moon, Mars, asteroids, outer planetary satellites, and other bodies that contain rocky components. The capability of flight instruments to conduct in situ geochronology is called out in the NASA Planetary Science Decadal Survey and the NASA Technology Roadmap as needing development to serve the community's needs. Beagle 2 is the only mission launched to date with the explicit aim to perform in situ K-Ar isotopic dating [1], but it failed to communicate and was lost. The first in situ K-Ar date on Mars, using SAM and APXS measurements on the Cumberland mudstone [2], yielded an age of 4.21 +/- 0.35 Ga and validated the idea of K-Ar dating on other planets, though the Curiosity method is not purpose-built for dating and requires many assumptions that degrade its precision. To get more precise and meaningful ages, multiple groups are developing dedicated in situ dating instruments.

  19. Petrology and geochronology of eclogites from the Variscan Schwarzwald (F.R.G.)


    Kalt, Angelika; Hanel, Michael; Schleicher, Helmut; Kramm, Ulrich


    The Moldanubian basement of the Schwarzwald contains basic to ultrabasic rocks of both crustal and mantle origin which display high-pressure mineral assemblages or relics of such. In order to constrain the P-T-t evolution of the crustal high-pressure rocks, petrological and geochronological studies have been carried out on three eclogite samples. Geothermobarometric estimations indicate minimum metamorphic pressures of 1.6 GPa and equilibration temperatures of 670 750°C. Reaction textures doc...

  20. Zircon geochronology of intrusive rocks from Cap de Creus, eastern Pyrenees



    New petrological and U–Pb zircon geochronological information has been obtained from intrusive plutonic rocks and migmatites from the Cap de Creus massif (Eastern Pyrenees) in order to constrain the timing of the thermal and tectonic evolution of this northeasternmost segment of Iberia during late Palaeozoic time. Zircons from a deformed syntectonic quartz diorite from the northern Cap de Creus Tudela migmatitic complex yield a mean age of 298.8±3.8 Ma. A syntectonic granodiori...

  1. Paleoproterozoic anorogenic granitoids of the Zheltav sialic massif (Southern Kazakhstan): Structural position and geochronology (United States)

    Tretyakov, A. A.; Degtyarev, K. E.; Sal'nikova, E. B.; Shatagin, K. N.; Kotov, A. B.; Ryazantsev, A. V.; Pilitsyna, A. V.; Yakovleva, S. Z.; Tolmacheva, E. V.; Plotkina, Yu. V.


    The basement of the Zheltav sialic massif (Southern Kazakhstan) is composed of different metamorphic rocks united into the Anrakhai Complex. In the southeastern part of the massif, these rocks form a large antiform with the core represented by amphibole and clinopyroxene gneissic granite varieties. By their chemical composition, dominant amphibole (hastingsite) gneissic granites correspond to subalkaline granites, while their petroand geochemical properties make them close to A-type granites. The U-Pb geochronological study of accessory zircons yielded an age of 1841 ± 6 Ma, which corresponds to the crystallization age of melts parental for protoliths of amphibole gneissic granites of the Zheltav Massif. Thus, the structural-geological and geochronological data make it possible to define the Paleoproterozoic (Staterian) stage of anorogenic magmatism in the Precambrian history of the Zheltav Massif. The combined Sm-Nd isotopic—geochronological data and age estimates obtained for detrital zircons indicate the significant role of the Paleoproterozoic tectono-magmatic stage in the formation of the Precambrian continental crust of sialic massifs in Kazakhstan and northern Tien Shan.

  2. Evidence of CFC degradation in groundwater under pyrite-oxidizing conditions (United States)

    Sebol, L.A.; Robertson, W.D.; Busenberg, E.; Plummer, L.N.; Ryan, M.C.; Schiff, S.L.


    A detailed local-scale monitoring network was used to assess CFC distribution in an unconfined sand aquifer in southwestern Ontario where the zone of 1-5-year-old groundwater was known with certainty because of prior use of a bromide tracer. Groundwater ???5 years old was confined to an aerobic zone at ???5 m depth and had CFC concentrations consistent with modern atmospheric mixing ratios at recharge temperatures of 7-11 ??C, as was observed in the 3-m thick vadose zone at the site. At depths below 6 m, the groundwater became progressively more reducing, however, with a denitrifying horizon at 6-7 m depth, and a Mn and Fe reducing zone below 7 m depth. In the anaerobic zone, 3H/3He ratios indicated that groundwater-age continued to increase uniformly with depth, to a maximum value of 27 years at 13 m depth. CFC concentrations, however, decreased abruptly within the denitrifying zone, leading to substantial age overestimation compared to the 3H/3He ages. Noble gas data indicated that the apparent CFC mass loss was not likely the result of gas stripping from possible bubble formation; thus, CFC degradation was indicated in the anoxic zone. The field data are consistent with first-order degradation rates of 0.3 yr-1 for CFC-12, 0.7 yr-1 for CFC-11, and 1.6 yr-1 for CFC-113. CFC attenuation at this site coincides with a zone where reduced S (pyrite) is actively oxidized by NO3 and dissolved oxygen (DO). Similar behavior has been observed at other sites [Tesoriero, A.J., Liebscher, H., Cox, S.E., 2000. Mechanism and rate of denitrification in an agricultural watershed: electron and mass balance along groundwater flow path. Water Resour. Res. 36 (6), 1545-1559; Hinsby, K., Hojberg, A.L., Engesgaard, P., Jensen, K.H., Larsen, F., Plummer, L.N., Busenberg, E., Accepted for publication. Transport and degradation of chlorofluorocarbons (CFCs) in a pyritic aquifer, Rabis Creek, Denmark. Water Resour. Res.], further demonstrating that the use of CFCs for age-dating anaerobic

  3. Reactivity of Dazomet, a Hydraulic Fracturing Additive: Hydrolysis and Interaction with Pyrite (United States)

    Consolazio, N.; Lowry, G. V.; Karamalidis, A.; Hakala, A.


    The Marcellus Shale is currently the largest shale gas formation in play across the world. The low-permeability formation requires hydraulic fracturing to be produced. In this process, millions of gallons of water are blended with chemical additives and pumped into each well to fracture the reservoir rock. Although additives account for less than 2% of the fracking fluid mixture, they amount to hundreds of tons per frack job. The environmental properties of some of these additives have been studied, but their behavior under downhole conditions is not widely reported in the peer-reviewed literature. These compounds and their reaction products may return to the surface as produced or waste water. In the event of a spill or release, this water has the potential to contaminate surface soil and water. Of these additives, biocides may present a formidable challenge to water quality. Biocides are toxic compounds (by design), typically added to the Marcellus Shale to control bacteria in the well. An assessment of the most frequently used biocides indicated a need to study the chemical dazomet under reservoir conditions. The Marcellus Shale contains significant deposits of pyrite. This is a ubiquitous mineral within black shales that is known to react with organic compounds in both oxic and anoxic settings. Thus, the objective of our study was to determine the effect of pyrite on the hydrolysis of dazomet. Liquid chromatography-triple quadrupole mass spectrometry (LC-QQQ) was used to calculate the loss rate of aqueous dazomet. Gas chromatography-mass spectrometry (GC-MS) was used to identify the reaction products. Our experiments show that in water, dazomet rapidly hydrolyses in water to form organic and inorganic transformation products. This reaction rate was unaffected when performed under anoxic conditions. However, with pyrite we found an appreciable increase in the removal rate of dazomet. This was accompanied by a corresponding change in the distribution of observed

  4. Mechanisms of pyrite oxidation to non-slagging species. Quarterly report, April 1, 1995--June 30, 1995

    Energy Technology Data Exchange (ETDEWEB)

    Akan-Etuk, A.E.J.; Mitchell, R.E.


    This document is the fourth quarterly status report on a project that is conducted at the High Temperature Gasdynamics Laboratory at Stanford University, Stanford, California and is concerned with enhancing the transformation of iron pyrite to non-slagging species during staged, low-NO{sub x} pulverized coal (P.C.) combustion. The research project is intended to advance PETC`s efforts to improve our technical understanding of the high-temperature chemical and physical processes involved in the utilization of coal. The work focuses on the mechanistic description and rate quantification of the effects of fuel properties and combustion environment on the oxidation of iron pyrite to form the non-slagging species magnetite. The knowledge gained from this work is intended to be incorporated into numerical codes that can be used to formulate anti-slagging strategies involving minimal disturbance of coal combustor performance. This project is to be performed over the three-year period from September 1994 to August 1997. The project aims to identify the mechanisms of pyrite combustion and to quantify their effects, in order to formulate a general rate expression for the combustion of pyrite that accounts for coal properties as well as furnace conditions.

  5. Model-based integration and analysis of biogeochemical and isotopic dynamics in a nitrate-polluted pyritic aquifer

    NARCIS (Netherlands)

    Zhang, Y.-C.; Prommer, H.; Broers, H.P.; Slomp, C.P.; Greskowiak, J.; Van Der Grift, B.; Van Cappellen, P.


    Leaching of nitrate from agricultural land to groundwater and the resulting nitrate pollution are a major environmental problem worldwide. Its impact is often mitigated in aquifers hosting sufficiently reactive reductants that can promote autotrophic denitrification. In the case of pyrite acting as

  6. Element mobility during pyrite weathering: implications for acid and heavy metal pollution at mining-impacted sites (United States)

    Lu, Long; Wang, Rucheng; Chen, Fanrong; Xue, Jiyue; Zhang, Peihua; Lu, Jianjun


    Based on back scattered electron images and electron micro-probe analysis results, four alteration layers, including a transition layer, a reticulated ferric oxide layer, a nubby ferric oxide layer and a cellular ferric oxide layer, were identified in the naturally weathering products of pyrite. These layers represent a progressive alteration sequence of pyrite under weathering conditions. The cellular ferric oxide layer correlates with the strongest weathering phase and results from the dissolution of nubby ferric oxide by acidic porewater. Leaching coefficient was introduced to better express the response of element mobility to the degree of pyrite weathering. Its variation shows that the mobility of S, Co and Bi is stronger than As, Cu and Zn. Sulfur in pyrite is oxidized to sulfuric acid and sulfate that are basically released into to porewater, and heavy metals Co and Bi are evidently released by acid dissolution. As, Cu and Zn are enriched in ferric oxide by adsorption and by co-precipitation, but they would re-release to the environment via desorption or dissolution when porewater pH becomes low enough. Consequently, Co, Bi, As, Cu and Zn may pose a substantial impact on water quality. Considering that metal mobility and its concentration in mine waste are two important factors influencing heavy metal pollution at mining-impacted sites, Bi and Co are more important pollutants in this case.

  7. Study on Bailing Properties of Pyrite Cinder%硫酸渣成球性能研究

    Institute of Scientific and Technical Information of China (English)

    陈文达; 翟大成; 李航


    对硫酸渣成球性能进行了研究.对硫酸渣磨矿后,其粒度和成球性能得到很大的改善.通过对硫酸渣球团的落下强度、抗压强度和生球爆裂温度等进行测定,得出在粒度水平(74μm/95.1%)及膨润土为1.0%条件下,硫酸渣的成球性能较好,能够满足冶金工艺的要求.%The bailing pmpenies of pyrite cinder are studied in this paper. AFter grinding on pyrite cinder, particle size and bailing properties are greatlly improved. Through the measuring of drop strength, compressive strength and cracking temperture on pyrite cinder pellet, it is found that the bailing properties of pyrite cinder is best at the level panicle size (74μm95.1%) and 1.0% bentonite, which can meet the requirements of metallurgical technology.

  8. Redox potential (Eh) and anion effects of pyrite (FeS 2 ) leaching at pH 1 (United States)

    Chandra, Anand P.; Gerson, Andrea R.


    Pyrite plays the central role in the environmental issue of acid rock drainage. Natural weathering of pyrite results in the release of sulphuric acid which can lead to further leaching of heavy and toxic metals from other associated minerals. Understanding how pyrite reacts in aqueous solution is critical to understanding the natural weathering processes undergone by this mineral. To this end an investigation of the effect of solution redox potential (Eh) and various anions on the rate of pyrite leaching under carefully controlled conditions has been undertaken. Leaching of pyrite has been shown to proceed significantly faster at solution Eh of 900 mV (SHE) than at 700 mV, at pH 1, for the leach media of HCl, H 2SO 4 and HClO 4. The predominant effect of Eh suggests electrochemical control of pyrite leaching with similar mechanism(s) at Eh of 700 and 900 mV albeit with different kinetics. Leach rates at 700 mV were found to decrease according to HClO 4 > HCl > H 2SO 4 while at 900 mV the leach rate order was HCl > HClO 4 > H 2SO 4. Solution Fe 3+ activity is found to continually increase during all leaches; however, this is not accompanied by an increase in leach rate. Synchrotron based photoemission electron microscopy (PEEM) measurements showed a localised distribution of adsorbed and oxidised surface species highlighting that pyrite oxidation and leaching is a highly site specific process mediated by adsorption of oxidants onto specific surface sites. It appears that rates may be controlled, in part, by the propensity of acidic anions to bind to the surface, which varies according to SO42->Cl->ClO4-, thus reducing the reactive or effective surface area. However, anions may also be involved in specific reactions with surface leach products. Stoichiometric dissolution data (Fe/S ratio), XPS and XRD data indicate that the highest leach rates (in HCl media at 900 mV Eh) correlate with relatively lower surface S abundance. Furthermore, there are indications that

  9. Brittle tectonothermal evolution in the Forsmark area, central Fennoscandian Shield, recorded by paragenesis, orientation and 40Ar/ 39Ar geochronology of fracture minerals (United States)

    Sandström, Björn; Tullborg, Eva-Lena; Larson, Sven Åke; Page, Laurence


    In this paper, we show how studies of fracture mineral paragenesis, their orientation and 40Ar/ 39Ar geochronology can be applied in order to recognise the brittle tectonothermal evolution in an area. Samples were selected from nearly 18 km of drill cores from the upper 1 km of the Fennoscandian Shield obtained during the site investigation for a repository of spent nuclear fuel in Forsmark, central Sweden. Four major events of fracturing and/or reactivation of fractures associated with fracture mineralisation have been distinguished. The first event was characterised by precipitation of epidote, quartz and chlorite, along preferably sub-horizontal and gently-dipping fractures or steep, WNW-ESE to NW-SE fractures. Precipitation occurred between 1.8 and 1.1 Ga, possibly during the late stage of the Svecokarelian orogeny close to 1.8-1.7 Ga. The second event is associated with precipitation of hematite-stained adularia and albite, prehnite, laumontite, calcite and chlorite, preferably along steep, ENE-WSW to NNE-SSW and NNW-SSE fractures. Precipitation occurred around 1107 ± 7 to 1034 ± 3 Ma, probably due to effects from the Sveconorwegian orogeny. This event was followed by a period with dissolution of fracture minerals and subsequent precipitation of mainly calcite, quartz, pyrite and asphaltite during the Palaeozoic. The formation fluid emanated from an overlying organic-rich sedimentary cover. Precipitation occurred during reactivation of Proterozoic fractures, but formation of new fractures is also inferred, possibly due to far-field effects of the Caledonian orogeny, or elevated hydrostatic pressure due to its foreland basin. The latest event is dominated by clay minerals, chlorite and calcite along hydraulically conductive fractures. These minerals are prominent along sub-horizontal and gently-dipping fractures, but also occur in sets of steeply-dipping fractures. It is inferred that the hydraulically conductive fractures are Proterozoic structures in which

  10. A Comprehensive Utilization Process for Black Manganese-silver Ores by Pyrite Reducing Method

    Institute of Scientific and Technical Information of China (English)


    On a 5 kg bench scale, the separating of Mn-Ag from black manganese-silver ores by pyrite reducing was investigated. Leached Mn content of 98.3% (mass fraction) along with silver loss of 1.5% is achieved. The purification of solution by the precipitation method was effectively used. Chemical grade -MnO2 with TMn content of 60.13% (mass fraction) and MnO2 content of 92.28% (mass fraction) is obtained. Mn recovery efficiency is 94.04%. The residues from leaching Mn process of black Mn-Ag ores was employed for silver extraction by cyanidation with leached silver content of 92.17% (mass fraction), displacement ratio of 99.5%, recovery efficiency of 90.79%. Therefore, the present study provides a feasible process for making full use of black manganese-silver ore resources.

  11. Evaluating structure selection in the hydrothermal growth of FeS2 pyrite and marcasite (United States)

    Kitchaev, Daniil A.; Ceder, Gerbrand


    While the ab initio prediction of the properties of solids and their optimization towards new proposed materials is becoming established, little predictive theory exists as to which metastable materials can be made and how, impeding their experimental realization. Here we propose a quasi-thermodynamic framework for predicting the hydrothermal synthetic accessibility of metastable materials and apply this model to understanding the phase selection between the pyrite and marcasite polymorphs of FeS2. We demonstrate that phase selection in this system can be explained by the surface stability of the two phases as a function of ambient pH within nano-size regimes relevant to nucleation. This result suggests that a first-principles understanding of nano-size phase stability in realistic synthesis environments can serve to explain or predict the synthetic accessibility of structural polymorphs, providing a guideline to experimental synthesis via efficient computational materials design.

  12. Elastic stability and electronic structure of pyrite type PtN2: Ahard semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Rong; Zhan, Qian; Zhang, Xiao-Feng


    The elastic properties and electronic structure of PtN2 withthe pyrite structure (PtN2(C2)) were studied with first-principlescalculations. The crystal structure is demonstrated to be elasticallystable with a lower energy than the metastable fluorite structureproposed before. The calculated shear modulus of 214 GPa suggests thatPtN2(C2) is harder than some well known hard materials such as TiN andSiC. The high elastic moduli are attributed to a stacking ofcorner-shared PtN6 octahedra bonded by strong N-N covalent bonding. Incontrast to the metallic fluorite-type phase, PtN2(C2) is semiconductingwith an indirect band gap.

  13. Pyrite oxidation and reduction - Molecular orbital theory considerations. [for geochemical redox processes (United States)

    Luther, George W., III


    In this paper, molecular orbital theory is used to explain a heterogeneous reaction mechanism for both pyrite oxidation and reduction. The mechanism demonstrates that the oxidation of FeS2 by Fe(3+) may occur as a result of three important criteria: (1) the presence of a suitable oxidant having a vacant orbital (in case of liquid phase) or site (solid phase) to bind to the FeS2 via sulfur; (2) the initial formation of a persulfido (disulfide) bridge between FeS2 and the oxidant, and (3) an electron transfer from a pi(asterisk) orbital in S2(2-) to a pi or pi(asterisk) orbital of the oxidant.

  14. Density functional calculation of equilibrium geometry and electronic structure of pyrite

    Institute of Scientific and Technical Information of China (English)

    邱冠周; 肖奇; 胡岳华; 徐竞


    The equilibrium geometry and electronic structure of pyrite has been studied using self-consistent density-functional theory within the local density approximation (LDA). The optimum bulk geometry is in good agreement with crystallographic data. The calculated band structure and density of states in the region around the Fermi energy show that valence-band maximum (VBM) is at X (100), and the conduction-band minimum (CBM) is at G (000). The indirect and direct band gaps are 0.6eV and 0.74eV, respectively. The calculated contour map of difference of charge density shows excess charge in nonbonding d electron states on the Fe sites. The density increases between sulfur nuclei and between iron and sulfur nuclei qualitatively reveal that S-S bond and Fe-S bond are covalent binding.

  15. Spin-driven symmetry breaking in the frustrated fcc pyrite MnS2. (United States)

    Kimber, Simon A J; Chatterji, Tapan


    We report the characterisation of natural samples of the cubic pyrite mineral MnS2 using very high resolution synchrotron x-ray diffraction techniques. At low temperatures we find a new low temperature polymorph, which results from coupling between magnetic and lattice degrees of freedom. Below the magnetic ordering temperature T(N) = 48 K, we detect a pseudo-tetragonal distortion with a tiny c/a ratio of 1.0006. The structure can be refined in the space group Pbca The symmetry lowering reduces magnetic frustration in the fcc Mn(2+) lattice and is likely responsible for the previously reported lock-in of the magnetic propagation vector. This behaviour is similar to the spin-Peierls phase transitions reported in other three-dimensional Heisenberg magnets like the chromate spinels.

  16. Near infrared to ultraviolet optical properties of bulk single crystal and nanocrystal thin film iron pyrite (United States)

    Subedi, Indra; Bhandari, Khagendra P.; Ellingson, Randall J.; Podraza, Nikolas J.


    We report optical properties of iron pyrite (FeS2) determined from ex situ spectroscopic ellipsometry measurements made on both a commercially available bulk single crystal and nanocrystalline thin film over a spectral range of 0.735-5.887 eV. The complex dielectric function, ɛ (E) = ɛ 1 (E) + iɛ 2 (E), spectra have been determined by fitting a layered parametric model to the ellipsometric measurements. Spectra in ɛ are modeled using a Kramers-Kronig consistent critical point parabolic band model involving seven critical points for the bulk single crystal and four critical points for the nanocrystalline film. Absorption coefficient spectra for both types of samples are also determined from ɛ. Critical point features in the nanocrystalline films are broader, have lower amplitude and lower energy critical points detected having a small blue shift when compared to the single crystal sample.

  17. Metalloproteins and the Pyrite-based Origin of Life: A Critical Assessment (United States)

    Rivas, Mario; Becerra, Arturo; Peretó, Juli; Bada, Jeffrey L.; Lazcano, Antonio


    We critically examine the proposal by Wächtershäuser (Prokaryotes 1:275-283, 2006a, Philos Trans R Soc Lond B Biol Sci 361: 787-1808, 2006b) that putative transition metal binding sites in protein components of the translation machinery of hyperthermophiles provide evidence of a direct relationship with the FeS clusters of pyrite and thus indicate an autotrophic origin of life in volcanic environments. Analysis of completely sequenced cellular genomes of Bacteria, Archaea and Eucarya does not support the suggestion by Wächtershäuser (Prokaryotes 1:275-283, 2006a, Philos Trans R Soc Lond B Biol Sci 361: 787-1808, 2006b) that aminoacyl-tRNA synthetases and ribosomal proteins bear sequence signatures typical of strong covalent metal bonding whose absence in mesophilic species reveals a process of adaptation towards less extreme environments.

  18. The volcanic-sedimentary sequence of the Lousal deposit, Iberian Pyrite Belt (Portugal) (United States)

    Rosa, Carlos; Rosa, Diogo; Matos, Joao; Relvas, Jorge


    The Iberian Pyrite Belt (IPB) is a massive sulfide province that is located in the south of Portugal and Spain, and hosts more than 90 massive sulfide deposits that amount to more than 1850 million metric tonnes of sulfide ore (Tornos, 2006). The ore deposits size, vary from ~1Mt to >100Mt (e.g. Neves Corvo and Aljustrel in Portugal, and Rio Tinto and Tharsis in Spain). The ore deposits are hosted by a submarine sedimentary and volcanic, felsic dominated, succession that constitutes the Upper Devonian to Lower Carboniferous Volcanic and Sedimentary Complex (VSC). The VSC ranges in thickness from approximately 600 to 1300 m (Tornos 2006). The VSC overlies the Phyllite-Quartzite Group (PQ) (Upper Devonian, base unknown) and is overlain by the Baixo Alentejo Flysch Group (Lower to Upper Carboniferous). The Lousal massive sulfide deposit is located in the western part of the IPB and occurs mostly interbedded with black mudstone. The VSC sequence at Lousal mine consists of a mudstone and quartzite sequence (PQ Group) in the lower part of the succession, over which a thick sequence of rhyolitic lavas (>300 m) occurs. Above the rhyolitic lavas there is a thick sequence of black and grey mudstone that hosts the massive sulfide ore bodies, and a rhyolitic sill. The upper part of the VSC sequence consists of a thick mudstone interval that hosts two thick basaltic units, locally with pillows. The rhyolites have small coherent cores, locally with flow bands, that grade to surrounding massive clastic intervals, with large lateral extent. The clasts show jigsaw-fit arrangement in many places and have planar or curviplanar margins and locally are perlitic at the margin. The top contact of these units is in most locations not exposed, which makes difficult to interpret the mode of emplacement. However, the thick clastic intervals, above described, are in accordance with quenching of volcanic glass with abundant water and therefore indicate that quenching of the rhyolites was the

  19. The role of isomorphous substitutions in natural selenides belonging to the pyrite group

    Energy Technology Data Exchange (ETDEWEB)

    Bindi, Luca [Museo di Storia Naturale, sez. di Mineralogia e Litologia, Universita degli Studi di Firenze, via La Pira 4, I-50121 Firenze (Italy)], E-mail:; Cipriani, Curzio [Museo di Storia Naturale, sez. di Mineralogia e Litologia, Universita degli Studi di Firenze, via La Pira 4, I-50121 Firenze (Italy); Pratesi, Giovanni [Museo di Storia Naturale, sez. di Mineralogia e Litologia, Universita degli Studi di Firenze, via La Pira 4, I-50121 Firenze (Italy); Dipartimento di Scienze della Terra, Universita degli Studi di Firenze, via La Pira 4, I-50121 Firenze (Italy); Trosti-Ferroni, Renza [Dipartimento di Scienze della Terra, Universita degli Studi di Firenze, via La Pira 4, I-50121 Firenze (Italy)


    The present paper reports chemical and structural data of selenide minerals belonging to the pyrite group. Eighteen samples of minerals in this group with variable chemical composition (7 samples of penroseite, NiSe{sub 2}; 10 samples of krutaite, CuSe{sub 2}; 1 sample of trogtalite, CoSe{sub 2}) were studied by means of X-ray single-crystal diffraction and electron microprobe. On the basis of information gained from the chemical characterization, we can conclude that a complete solid solution between NiSe{sub 2} and CuSe{sub 2} exists in nature with the absence of pure end-members. Although verified only for the Ni-rich members, we also infer a solid solution between NiSe{sub 2} and CoSe{sub 2}. The unit-cell parameters were modeled using a multiple regression method as a function of the Co, Ni, and Cu contents.

  20. Transport and degradation of chlorofluorocarbons (CFCs) in the pyritic Rabis Creek aquifer, Denmark (United States)

    Hinsby, K.; Hojberg, A.L.; Engesgaard, P.; Jensen, K.H.; Larsen, F.; Plummer, L.N.; Busenberg, E.


    Vertical profiles of the chlorofluorocarbons CFC-11, CFC-12, and CFC-113 penetrating aerobic and anaerobic parts of a shallow sandy aquifer show that the CFC gases are degraded in the groundwater in a pyritic sand aquifer at Rabis Creek, Denmark. Two-dimensional solute transport simulations with either zero-order or first-order degradation in the anaerobic zone corroborate this interpretation. The transport model was previously calibrated against detailed tritium profiles in the same wells. First-order degradation is found to best match the observed CFC profiles yielding an approximate half-life of a few months for CFC-11. Degradation is not as clearly recognized for CFC-12 and CFC-113, but it may occur with rates corresponding to a half-life of a few years or more. Data indicate a geochemical control of the CFC concentration gradient at the redox front and that denitrification and denitrifiers are not of major importance for the observed CFC degradation. The responsible mechanism behind the observed degradation is not known but we suggest that reductive dehalogenation by surface-bound Fe(II) on pyrite possibly enhanced by the presence of Fe(III)-bearing weathering products (green rust) may be a plausible mechanism. The observed data and the performed simulations confirm the potential application of the CFC gases as age-dating tools in the aerobic part of the investigated aquifer, but also that CFC data must be analyzed carefully before it is used as a dating tool in reducing aquifers because degradation may have occurred. The use of multiple or alternative tracers should be considered in anaerobic environments. Copyright 2007 by the American Geophysical Union.

  1. Natural Monocrystalline Pyrite as Sensor for Potentiometric Redox Titrations. Part I. Titrations with Permanganate

    Directory of Open Access Journals (Sweden)

    B. V. Vukanovic


    Full Text Available Results obtained in potentiometric titrations of Fe(II, Mn(II, Fe(CN64-, C2O42- and As(III with standard potassium permanganate solution, are presented. The titration end point (TEP was detected with a universal electrode whose sensor is natural crystalline pyrite. The titrations of As(III were carried out in HCl (1.2 M and H2SO4 solutions (0.1- 4.5 M, whereas oxalate was determined in H2SO4 (0.1-4.5 M. Iron(II and hexacyanoferrate(II were titrated in H2SO4 and also in H3PO4 solutions (0.1-4.5 M. The titrations of Mn(II were performed in H2P2O72- media at pH 4.0, 5.0, 6.0 and 7.0. The results obtained by using the pyrite electrode were compared with those obtained by the application of a Pt-electrode, and good agreement, reproducibility and accuracy were obtained. The potentials in the course of the titration and at the end-point (TEP are rapidly established. The potential changes at the TEP ranged from 90 to 330 mV/0.1 mL, depending on the titrated system. The highest changes were observed in titrations of Fe(II in H3PO4 (240-330 mV/0.1 mL. Reversed titrations were also performed and accurate and reproducible results were obtained.

  2. Trace elements contamination of agricultural soils affected by sulphide exploitation (Iberian Pyrite Belt, Sw Spain) (United States)

    López, María; González, Isabel; Romero, Antonio


    Agricultural soils of the Riotinto mining area (Iberian Pyrite Belt) have been studied to assess the degree of pollution by trace elements as a consequence of the extraction and treatment of sulphides. Fifteen soil samples were collected and analysed by ICP-OES and INAA for 51 elements. Chemical analyses showed an As-Cu-Pb-Zn association related with the mineralisation of the Iberian Pyrite Belt. Concentrations were 19-994 mg kg-1 for As, 41-4,890 mg kg-1 for Pb, 95-897 mg kg-1 for Zn and of 27-1,160 mg kg-1 for Cu. Most of the samples displayed concentrations of these elements higher than the 90th percentile of the corresponding geological dominium, which suggests an anthropogenic input besides the bedrock influence. Samples collected from sediments were more contaminated than leptosols because they were polluted by leachates or by mining spills coming from the waste rock piles. The weathering of the bedrock is responsible for high concentrations in Co, Cr and Ni, but an anthropogenic input, such as wind-blown dust, seems to be indicative of the high content of As, Cu, Pb and Zn in leptosols. The metal partitioning patterns show that most trace elements are associated with Fe amorphous oxy-hydroxides, or take part of the residual fraction. According to the results obtained, the following mobility sequence is proposed for major and minor elements: Mn, Pb, Cd, > Zn, Cu > Ni > As > Fe > Cr. The high mobility of Pb, Cu and Zn involve an environmental risk in this area, even in soils where the concentrations are not so high.

  3. Extracting gold from pyrite roster cinder by ultra-fine-grinding and resin-in-pulp

    Institute of Scientific and Technical Information of China (English)

    危俊婷; 严规有; 郭炳昆; 高桂兰


    The ultra-fine-grinding and resin-in-pulp with pH value of 10 are used to extract gold from pyrite roster cinder. During leaching process, aluminium oxide ball is used as stirring medium, hydrogen peroxide as leaching agent and sodium hexametaphosphate as grinding agent. With AM-26 resin as absorber and sulfocarbamide as eluent, gold is recovered from cyanide pulp of pyrite roster cinder by resin-in-pulp. The effects of contact time, temperature and acidity etc. on the gold absorption are investigated by static methods and dynamic method respectively. The effects of flow rate of solution on dynamic adsorption and elution of gold are studied. The results show that AM-26 resin has good adsorbability in cyanide solution, and gold can be easily eluated from the loaded resin with 0. 1mol/L hydrochloric acid and lmol/L sulfocabamide. The adsorption rate and the elution of gold exceed 98%. When leaching time is 2 h, mass ratio of liquid to solid 4: 1, consumption of sodium cyanide 3 kg/t, concentration of hydrogen peroxide and sodium hexametaphosphate 0. 05% respectively, adsorption time 30 min, temperature 10-30 ℃, volume of resin 3 mL, ratio of eluent to resin (10-20): 1, velocity of eluent 1.5 mL/min, the leaching rate of gold reaches 85%. Compared with traditional leaching technology, it can reduce leaching time, avoid complex filter process, decrease sodium cyanide consumption and increase leaching rate of gold by 35%.

  4. Phase Stability and Stoichiometry in Thin Film Iron Pyrite: Impact on Electronic Transport Properties. (United States)

    Zhang, Xin; Scott, Tom; Socha, Tyler; Nielsen, David; Manno, Michael; Johnson, Melissa; Yan, Yuqi; Losovyj, Yaroslav; Dowben, Peter; Aydil, Eray S; Leighton, Chris


    The use of pyrite FeS2 as an earth-abundant, low-cost, nontoxic thin film photovoltaic hinges on improved understanding and control of certain physical and chemical properties. Phase stability, phase purity, stoichiometry, and defects, are central in this respect, as they are frequently implicated in poor solar cell performance. Here, phase-pure polycrystalline pyrite FeS2 films, synthesized by ex situ sulfidation, are subject to systematic reduction by vacuum annealing (to 550 °C) to assess phase stability, stoichiometry evolution, and their impact on transport. Bulk probes reveal the onset of pyrrhotite (Fe(1-δ)S) around 400 °C, rapidly evolving into the majority phase by 425 °C. This is supported by X-ray photoelectron spectroscopy on (001) crystals, revealing surface Fe(1-δ)S formation as low as 160 °C, with rapid growth near 400 °C. The impact on transport is dramatic, with Fe(1-δ)S minority phases leading to a crossover from diffusive transport to hopping (due to conductive Fe(1-δ)S nanoregions in an FeS2 matrix), followed by metallicity when Fe(1-δ)S dominates. Notably, the crossover to hopping leads to an inversion of the sign, and a large decrease in magnitude of the Hall coefficient. By tracking resistivity, magnetotransport, magnetization, and structural/chemical parameters vs annealing, we provide a detailed picture of the evolution in properties with stoichiometry. A strong propensity for S-deficient minority phase formation is found, with no wide window where S vacancies control the FeS2 carrier density. These findings have important implications for FeS2 solar cell development, emphasizing the need for (a) nanoscale chemical homogeneity, and (b) caution in interpreting carrier types and densities.

  5. Pyrite oxidation in the presence of hematite and alumina: II. Effects on the cathodic and anodic half-cell reactions. (United States)

    Tabelin, Carlito Baltazar; Veerawattananun, Suchol; Ito, Mayumi; Hiroyoshi, Naoki; Igarashi, Toshifumi


    The oxidative dissolution of pyrite is an important process in the redox recycling of iron (Fe) and is well-known for its role in the formation of acid mine drainage (AMD), which is considered as the most serious and widespread problem after the closure of mines and mineral processing operations. Because this process requires the movement of electrons, common metal oxides in nature that have either semiconducting (e.g., hematite) or insulating (e.g., alumina) properties may have strong effects on it. In this study, changes in the electrochemical behavior of pyrite in the presence of hematite and alumina were investigated. Results showed that the formation of surface-bound species directly influenced the anodic and cathodic half-cell reactions as well as the transfer of electrons between these sites. Pyrite pretreated in the air became anodically more reactive than that pretreated in oxygenated water, but the type of oxidizing media had little effect on the cathodic half-cell reaction. The presence of hematite and alumina during pretreatment also had strong effects on the electrochemical properties of pyrite. Chronoamperometry measurements suggest that hematite and alumina enhanced the anodic half-cell reaction but suppressed the cathodic half-cell reaction of pyrite oxidation. Increased anodic half-cell reaction in the presence of hematite could be attributed to electron "bridging" and catalytic effects of this mineral. In contrast, the effects of alumina on the anodic half-cell reaction were indirect and could be explained by the formation of Fe(3+)-oxyhydroxide surface species during pretreatment. Suppression of the cathodic half-cell reaction by both minerals was attributed to their "protective" effect on cathodic sites. Our results also point to the cathodic half-cell reaction as the rate determining-step of the overall oxidative dissolution process.

  6. Stratigraphic and micropetrographic occurrences of pyrite in sediments at the confluence of carbonate and peat-forming depositional systems, southern Florida, USA

    Energy Technology Data Exchange (ETDEWEB)

    Brown, K.E.; Cohen, A.D. (University of South Carolina, Columbia, SC (United States). Dept. of Geological Sciences)


    This study was undertaken to investigate peat/carbonate relationships in a modern coal-forming setting, with initial research on pyrite and sulfur contents relative to stratigraphic and petrographic conditions. Over 40 closely spaced cores were taken from transects from Florida Bay inland through mangrove swamps and freshwater Everglades. Core stratigraphy confirms an overall transgressive sequence, but new evidence supports a small regression within the overall transgression. On average, both total S and pyrite are lowest at inland sites, highest near the coastline, and intermediate in Florida Bay sediments. Total S is higher in marine than freshwater peats, but freshwater peats overlain by marine peats are enriched in S. In cores that start with peat at the top, pyrite is generally absent or very low in the top 20 cm. Higher percentages of pyrite occur in carbonate rather than peat facies. Pyrite exists in three forms, framboidal aggregates, minute crystals, and large solitary crystals. Most of the pyrite occurs as minute crystals ([lt]2[mu]m) and framboidal aggregates. The occurrence of large crystals ([gt]2[mu]m) is less common and generally restricted to the cavities of larger cells or cavities within other organics (e.g. foraminifer, pollen grains, fungal sclerotia). A general relationship seems to exist in certain cases between the occurrence of spherical organic cell fillings and the occurrence of the framboidal form of pyrite. 37 refs., 20 figs., 2 tabs.

  7. Solution-based Syntheses of Iron Pyrite Thin Films for Photovoltaic and Protein Foot-printing Applications (United States)

    El Makkaoui, Mohammed

    Iron pyrite (cubic FeS2) is a non-toxic, earth abundant semiconductor possessing a set of excellent optical/electronic properties for serving as an absorber layer in PV devices. Additionally, pyrite is a very efficient hydroxyl radical generator via Fenton chemistry and has shown promise in oxidative protein and DNA foot-printing application. The main focus of this thesis is on fabricating phase and elementally pure iron pyrite thin films using a solution-based approach that employs hydrazine as a solvent. A precursor ink is formed at room temperature by mixing elemental iron and sulfur in anhydrous hydrazine and then deposited on Mo-coated glass substrates, via spin coating, to yield amorphous iron sulfide films that are then annealed in H2S (340°C) and sulfur gas (≤ 500 °C) to form uniform, polycrystalline and phase pure pyrite films with densely packed grains. This approach is likely to yield the most elementally pure pyrite thin films made to date, through a very simple and scalable process. The ink has shown to be very sensitive to environmental conditions and has a very short shelf life (˜1 day). Additionally, the film microstructure is greatly influenced by the S:Fe concentration ratio that when tuned to 3:1, yielded uniform, robust and optically flat iron sulfide thin films with an optimal thickness (˜320 nm) for PV application. The results however were not reproducible, mainly due to failure in applying multiple layers without compromising film morphology. Thinner (films, on the other hand, are reproducibly produced, but are too thin to be employed in PV devices. Direct annealing in sulfur gas at 475°C for 4 hours, bypassing the > 12 hour H2S annealing step, yielded phase pure pyrite films, with good morphology, at lower processing time and annealing temperatures (polymer laminates for protein foot-printing application in collaboration with the Brenowitz lab at the Albert Einstein College of Medicine and the Khine lab at the University of California

  8. Chemical and sulphur isotope compositions of pyrite in the Jaduguda U (-Cu-Fe) deposit, Singhbhum shear zone, eastern India: Implications for sulphide mineralization (United States)

    Pal, Dipak C.; Sarkar, Surajit; Mishra, Biswajit; Sarangi, A. K.


    The Jaduguda U (-Cu-Fe) deposit in the Singhbhum shear zone has been the most productive uranium deposit in India. Pyrite occurs as disseminated grains or in sulphide stringers and veins in the ore zone. Veins, both concordant and discordant to the pervasive foliation, are mineralogically either simple comprising pyrite ± chalcopyrite or complex comprising pyrite + chalcopyrite + pentlandite + millerite. Nickel-sulphide minerals, though fairly common in concordant veins, are very rare in the discordant veins. Pyrite in Ni-sulphide association is commonly replaced by pentlandite at the grain boundary or along micro-cracks. Based on concentrations of Co and Ni, pyrite is classified as: type-A - high Co (up to 30800 ppm), no/low Ni; type-B - moderate Co (up to 16500 ppm) and moderate to high Ni (up to 32700 ppm); type-C - no/low Co and high Ni (up to 43000 ppm); type-D - neither Co nor Ni. Textural and compositional data of pyrites suggest that the hydrothermal fluid responsible for pre-/early-shearing mineralization evolved from Co-rich to Ni-rich and the late-/post-shearing fluid was largely depleted in minor elements. Sulphur isotope compositions of pyrite mostly furnish positive values ranging between -0.33 and 12.06‰. Composite samples of pyrites with only type-A compositions and mixed samples of type-A and type-B are consistently positive. However, pyrite with mixed type-A and type-C and pyrite with type-D compositions have negative values but close to 0‰. By integrating minor element and sulphur isotope compositions of pyrite in conjunction with other published data on the Jaduguda deposit, it is proposed that reduced sulphur for the precipitation of most pyrites (type-A, type-B) was likely derived from isotopically heavy modified seawater. However, some later sulphur might be magmatic in origin remobilized from existing sulphides in the mafic volcanic rocks in the shear zone.

  9. Chemical and sulphur isotope compositions of pyrite in the Jaduguda U (–Cu–Fe) deposit, Singhbhum shear zone, eastern India: Implications for sulphide mineralization

    Indian Academy of Sciences (India)

    Dipak C Pal; Surajit Sarkar; Biswajit Mishra; A K Sarangi


    The Jaduguda U (–Cu–Fe) deposit in the Singhbhum shear zone has been the most productive uranium deposit in India. Pyrite occurs as disseminated grains or in sulphide stringers and veins in the ore zone. Veins, both concordant and discordant to the pervasive foliation, are mineralogically either simple comprising pyrite ± chalcopyrite or complex comprising pyrite + chalcopyrite + pentlandite + millerite. Nickel-sulphide minerals, though fairly common in concordant veins, are very rare in the discordant veins. Pyrite in Ni-sulphide association is commonly replaced by pentlandite at the grain boundary or along micro-cracks. Based on concentrations of Co and Ni, pyrite is classified as: type-A — high Co (up to 30800 ppm), no/low Ni; type-B — moderate Co (up to 16500 ppm) and moderate to high Ni (up to 32700 ppm); type-C — no/low Co and high Ni (up to 43000 ppm); type-D — neither Co nor Ni. Textural and compositional data of pyrites suggest that the hydrothermal fluid responsible for pre-/early-shearing mineralization evolved from Co-rich to Ni-rich and the late-/post-shearing fluid was largely depleted in minor elements. Sulphur isotope compositions of pyrite mostly furnish positive values ranging between -0.33 and 12.06%. Composite samples of pyrites with only type-A compositions and mixed samples of type-A and type-B are consistently positive. However, pyrite with mixed type-A and type-C and pyrite with type-D compositions have negative values but close to 0. By integrating minor element and sulphur isotope compositions of pyrite in conjunction with other published data on the Jaduguda deposit, it is proposed that reduced sulphur for the precipitation of most pyrites (type-A, type-B) was likely derived from isotopically heavy modified seawater. However, some later sulphur might be magmatic in origin remobilized from existing sulphides in the mafic volcanic rocks in the shear zone.

  10. Hydrochemical and stable isotope indicators of pyrite oxidation in carbonate-rich environment; the Hamersley Basin, Western Australia (United States)

    Dogramaci, Shawan; McLean, Laura; Skrzypek, Grzegorz


    Sulphur (S) is a commonly occurring element in most aquifers, primarily in oxidised (sulphates) and reduced (sulphides) forms. Sulphides often constitute a risk to groundwater quality due to acid rock drainage, especially in catchments that are subject to mining excavations or groundwater injection. However, in semi-arid regions detection of the acid rock drainage risk can be challenging and traditional methods based on observations of increasing SO4 concentrations or SO4/Cl ratios in surface and groundwater, are not necessarily applicable. In addition, decreasing pH, usually accompanying pyrite oxidation, can be masked by the high pH-neutralisation capacity of carbonate and silicate minerals. Analysis of 73 surface and groundwater samples from different water bodies and aquifers located in the Hamersley Basin, Western Australia found that most of the samples are characterised by neutral pH but there was also a large spatial variability in the dissolved sulphate (SO4) concentrations that ranged from 1 mg/L to 15,000 mg/L. Not surprisingly, groundwater in aquifers that contained pyrite had high sulphate concentrations (>1000 mg/L). This was associated with low δ34SSO4 values (+1.2‰ to +4.6‰) and was consistent with the values obtained from aquifer matrix pyritic rock samples (-1.9‰ to +4.4‰). It was also found that the SO4 concentrations and acidity levels were not only dependent on δ34SSO4 values and existence of pyrite but also on the presence of carbonate minerals in the aquifer matrix. The groundwater in aquifers containing both pyrite and carbonate minerals had a neutral pH and was also saturated with respect to gypsum and had high magnesium concentrations of up to 2200 mg/L suggesting de-dolomitisation as the process buffering the acidity generated by pyrite oxidation. Based on the findings from this study, a classification scheme has been developed for identification of the acid rock drainage contribution to groundwater that encompasses a myriad of

  11. Automating U-Pb IDTIMS data reduction and reporting: Cyberinfrastructure meets geochronology (United States)

    Bowring, J. F.; McLean, N.; Walker, J. D.; Ash, J. M.


    We demonstrate the efficacy of an interdisciplinary effort between software engineers and geochemists to produce working cyberinfrastructure for geochronology. This collaboration between CIRDLES, EARTHTIME and EarthChem has produced the software programs Tripoli and U-Pb_Redux as the cyber-backbone for the ID-TIMS community. This initiative incorporates shared isotopic tracers, data-reduction algorithms and the archiving and retrieval of data and results. The resulting system facilitates detailed inter-laboratory comparison and a new generation of cooperative science. The resolving power of geochronological data in the earth sciences is dependent on the precision and accuracy of many isotopic measurements and corrections. Recent advances in U-Pb geochronology have reinvigorated its application to problems such as precise timescale calibration, processes of crustal evolution, and early solar system dynamics. This project provides a heretofore missing common data reduction protocol, thus promoting the interpretation of precise geochronology and enabling inter-laboratory comparison. U-Pb_Redux is an open-source software program that provides end-to-end support for the analysis of uranium-lead geochronological data. The system reduces raw mass spectrometer data to U-Pb dates, allows users to interpret ages from these data, and then provides for the seamless federation of the results, coming from many labs, into a community web-accessible database using standard and open techniques. This EarthChem GeoChron database depends also on keyed references to the SESAR sample database. U-Pb_Redux currently provides interactive concordia and weighted mean plots and uncertainty contribution visualizations; it produces publication-quality concordia and weighted mean plots and customizable data tables. This initiative has achieved the goal of standardizing the data elements of a complete reduction and analysis of uranium-lead data, which are expressed using extensible markup

  12. 云浮硫铁矿及其焙烧灰渣中元素铊的组成特征%Distribution of Thallium in Pyrite Ores and Its Cinders of Yunfu Pyrite Mine,Guangdong

    Institute of Scientific and Technical Information of China (English)

    谢文彪; 陈永亨; 陈穗玲; 王甘霖; 常向阳


    本文研究了铊元素在云浮硫铁矿矿石及其焙烧灰和渣中的含量特征,并探讨了矿山开采和资源利用过程中产生的含铊废弃物对环境的影响。表明进一步开展相关的资源综合利用研究和废弃物综合治理研究是十分必要的。%In this paper,the content and distribution of thallium in pyrite ore,ash and cinder is studied.The effect of thallium in ore and cinder on environment is also approached.The study shows that it is necessary to research comprehensive utilization methods of this type of resources and complex harnessing way of pyrite ash and cinder.

  13. Advanced Cyberinfrastructure for Geochronology as a Collaborative Endeavor: A Decade of Progress, A Decade of Plans (United States)

    Bowring, J. F.; McLean, N. M.; Walker, J. D.; Gehrels, G. E.; Rubin, K. H.; Dutton, A.; Bowring, S. A.; Rioux, M. E.


    The Cyber Infrastructure Research and Development Lab for the Earth Sciences ( has worked collaboratively for the last decade with geochronologists from EARTHTIME and EarthChem to build cyberinfrastructure geared to ensuring transparency and reproducibility in geoscience workflows and is engaged in refining and extending that work to serve additional geochronology domains during the next decade. ET_Redux (formerly U-Pb_Redux) is a free open-source software system that provides end-to-end support for the analysis of U-Pb geochronological data. The system reduces raw mass spectrometer (TIMS and LA-ICPMS) data to U-Pb dates, allows users to interpret ages from these data, and then facilitates the seamless federation of the results from one or more labs into a community web-accessible database using standard and open techniques. This EarthChem database - - depends on keyed references to the System for Earth Sample Registration (SESAR) database that stores metadata about registered samples. These keys are each a unique International Geo Sample Number (IGSN) assigned to a sample and to its derivatives. ET_Redux provides for interaction with this archive, allowing analysts to store, maintain, retrieve, and share their data and analytical results electronically with whomever they choose. This initiative has created an open standard for the data elements of a complete reduction and analysis of U-Pb data, and is currently working to complete the same for U-series geochronology. We have demonstrated the utility of interdisciplinary collaboration between computer scientists and geoscientists in achieving a working and useful system that provides transparency and supports reproducibility, allowing geochemists to focus on their specialties. The software engineering community also benefits by acquiring research opportunities to improve development process methodologies used in the design, implementation, and sustainability of domain-specific software.

  14. Algorithms and software for U-Pb geochronology by LA-ICPMS (United States)

    McLean, Noah M.; Bowring, James F.; Gehrels, George


    The past 15 years have produced numerous innovations in geochronology, including experimental methods, instrumentation, and software that are revolutionizing the acquisition and application of geochronological data. For example, exciting advances are being driven by Laser-Ablation ICP Mass Spectrometry (LA-ICPMS), which allows for rapid determination of U-Th-Pb ages with 10s of micrometer-scale spatial resolution. This method has become the most commonly applied tool for dating zircons, constraining a host of geological problems. The LA-ICPMS community is now faced with archiving these data with associated analytical results and, more importantly, ensuring that data meet the highest standards for precision and accuracy and that interlaboratory biases are minimized. However, there is little consensus with regard to analytical strategies and data reduction protocols for LA-ICPMS geochronology. The result is systematic interlaboratory bias and both underestimation and overestimation of uncertainties on calculated dates that, in turn, decrease the value of data in repositories such as EarthChem, which archives data and analytical results from participating laboratories. We present free open-source software that implements new algorithms for evaluating and resolving many of these discrepancies. This solution is the result of a collaborative effort to extend the U-Pb_Redux software for the ID-TIMS community to the LA-ICPMS community. Now named ET_Redux, our new software automates the analytical and scientific workflows of data acquisition, statistical filtering, data analysis and interpretation, publication, community-based archiving, and the compilation and comparison of data from different laboratories to support collaborative science.

  15. Discussion: The timing of gold mineralization across the eastern Yilgarn Craton using U-Pb geochronology of hydrothermal phosphate minerals (United States)

    Bateman, Roger; Jones, Sarah


    The presentation of recent geochronological work on orogenic gold deposits in the Eastern Goldfields of the Yilgarn Craton, Western Australia, claims to prove that there is a single broad event of gold mineralization and that structural work demonstrating that there are a number of discrete gold mineralization events is wrong. This new data demonstrates no such thing, as this data, no doubt the best that can currently be produced, shows a very wide and inconsistent range in ages. Geochronology is not yet able to reliably separate these events, which appear to be spread over an interval of perhaps 30 Ma, up to ˜2635 Ma.

  16. Timing is Everything:The Boon and Bane of 14C Geochronology

    Energy Technology Data Exchange (ETDEWEB)

    Guilderson, T; Guilderson, T; Reimer, P J; Brown, T


    There are underappreciated limitations of the conversion of {sup 14}C-ages to the fixed, calendrical time-scale that bear directly upon our understanding of the dynamic climate system, or the relationship between the collapse of one civilization and it's neighbor's. In this paper we present a quantitative assessment of the limits of {sup 14}C-geochronology and calibration onto the absolute calendrical time-scale over the Holocene. We take into account not only the inherent limitations of the {sup 14}C-calendar calibration curve, but also analytical uncertainties.

  17. (U–Th)/He geochronology of goethite and the origin and evolution of cangas


    Monteiro, Hevelyn S.; VASCONCELOS,PAULO M.; Farley, Kenneth A.; Spier, Carlos A.; Mello, Claudio L.


    (U–Th)/He geochronology of 147 grains of goethite cements extracted from ferruginous duricrusts (cangas) developed on banded iron-formations from the Quadrilátero Ferrífero region, Minas Gerais, Brazil, records a history of protracted mineral dissolution–reprecipitation that started at ca. 48.1 ± 4.8 Ma and continues intermittently until the Present. A large majority of the samples (more than 30%) are younger than 2 Ma, revealing active mineral dissolution–reprecipitation in the recent pas...

  18. SHRIMP Zircon U-Pb and Molybdenite Re-Os Dating of the Skarn-type Tungsten Deposits in Southern Jiangxi Province, China, and Geological Implications: Examplified by the Jiaoli and Baoshan Tungsten Polymetallic Deposits%赣南矽卡岩型钨矿成岩成矿年代学及地质意义——以焦里和宝山矿床为例

    Institute of Scientific and Technical Information of China (English)

    丰成友; 曾载淋; 王松; 梁景时; 丁明


    Skarn-type tungsten deposit is a very important type of tungsten mineral resources in southern Jiangxi province.Based on detailed field investigation and analysis on major elements,trace elements,rare earth elements and radiometric dating,the ages of tungsten mineralization and petrogenesis of ore-bearing granitoids,and tectonic environment of the skarn-type tungsten deposits in southern Jiangxi province were studied.SHRIMP zircon U-Pb age for the medium to fine-gained porphyritic granodiorite from the Jiaoli ore district is 164.4 ±1.1 Ma.Molybdenite Re-Os isochron age for the related Jiaoli skarn tungsten deposit is 170.6 ±4.6 Ma.The SHRIMP zircon U-Pb age of the Baoshan medium to fine-grained granite is 156.6 ±3.9 Ma,whereas the molybdenite Re-Os mean model age for the related Baoshan skarn-type tungsten deposit is 161.0 ±1.9 Ma.Thus,W-Sn mineralization and granite crystallization taking place in Middle to Late Jurassic were contemporaneous.These new ages,combined with those available in the literature,indicate that the ages of the granites and related W-Sn ores are Middle to Late Jurassic with a peak at 150 to 160 Ma.It can be concluded that tungsten mineralization occurred under Jurassic intraplate extensional environment which was a phase of lithospheric thinning in southern China.%矽卡岩型钨矿是赣南地区的一种重要钨矿床类型.本文以焦里和宝山两个典型的矽卡岩型钨多金属矿床为例,开展了系统的成岩成矿年代学和岩石地球化学研究,结合区域钨锡矿床最新年代学研究成果,探讨了赣南地区钨矿的成岩成矿时代及形成构造环境.结果表明,焦里矽卡岩型钨多金属矿区斑状花岗闪长岩SHRIMP锆石U-Pb年龄为164.4±1.1 Ma,辉钼矿Re-Os等时线年龄为170.6 ±4.6 Ma;宝山矽卡岩型钨矿区花岗岩SHRIMP锆石U-Pb年龄为156.6±3.9 Ma,辉钼矿Re-Os模式年龄加权平均值为161.0±1.9 Ma,厘定了它们的成岩成矿年龄为中-晚侏罗世,同一矿

  19. Mineralization and trace element distribution in pyrite using EMPA in exploration drill holes from Cheshmeh Zard gold district, Khorasan Razavi Province, Iran

    Directory of Open Access Journals (Sweden)

    Zahra Alaminia


    Full Text Available Introduction Pyrite is the most abundant sulfide mineral in low sulfidation ore deposits. Experimental studies have shown that low-temperature ( 200°C from hydrothermal or metamorphic fluids (Butler and Rickard, 2000. Framboidal pyrite mostly occurs in sedimentary environments, though it could also form during metamorphism and hydrothermal alteration (Scott et al., 2009. The pyrite formed tends to be enriched in various trace elements such as Au and As. For this study we have combined the geology, alteration, mineralization with recent studies of the description of the deposit from core logging and underground mapping and geochemistry in the CheshmehZard gold district and also investigated the compositional variation and textural differences between pyrite types. This study is based on the results of our alteration and mineralization mapping and detailed logging of 1937.8 m of drill core. Materials and Methods Geology, hydrothermal alteration and mineralization were examined in drill holes along several cross sections. Host-rock alteration minerals and veins were determined for 11 samples using standard X-ray diffraction (XRD and X-ray fluorescence spectrometry (XRF techniques. Polished sections were studied by reflected light microscopy and backscattered electron images (BSE. In this study, the trace-element composition of pyrite samples from the Au-III vein system was obtained using electron microprobe analyzer (EMPA data. All analyseswere carried out at the department of Materials Engineering and Physics of the University of Salzburg in Austria. The EMPA measurements and BSE imaging were made using a JXA-8600 electron microprobe. Spot analyses of 30 pyrite grains from CheshmehZard are given in Table 1. Results The study area is located in the north of Khorasan Razavi Province 45 km to the south of Neyshabour. The area near CheshmehZard could become important as a site of economically significant gold mineralization. Six gold-bearing vein

  20. Peptide synthesis in aqueous environments: the role of extreme conditions and pyrite mineral surfaces on formation and hydrolysis of peptides. (United States)

    Schreiner, Eduard; Nair, Nisanth N; Wittekindt, Carsten; Marx, Dominik


    A comprehensive study of free energy landscapes and mechanisms of COS-mediated polymerization of glycine via N-carboxy anhydrides (NCAs, "Leuchs anhydrides") and peptide hydrolysis at the water-pyrite interface at extreme thermodynamic conditions is presented. Particular emphasis is set on the catalytic effects of the mineral surface including the putative role of the ubiquitous sulfur vacancy defects. It is found that the mere presence of a surface is able to change the free energetics of the elementary reaction steps. This effect can be understood in terms of a reduction of entropic contributions to the reactant state by immobilizing the reactants and/or screening them from bulk water in a purely geometric ("steric") sense. Additionally, the pyrite directly participates chemically in some of the reaction steps, thus changing the reaction mechanism qualitatively compared to the situation in bulk water. First, the adsorption of reactants on the surface can preform a product-like structure due to immobilizing and scaffolding them appropriately. Second, pyrite can act as a proton acceptor, thus replacing water in this role. Third, sulfur vacancies are found to increase the reactivity of the surface. The finding that the presence of pyrite speeds up the rate-determining step in the formation of peptides with respect to the situation in bulk solvent while stabilizing the produced peptide against hydrolysis is of particular interest to the hypothesis of prebiotic peptide formation at hydrothermal aqueous conditions. Apart from these implications, the generality of the studied organic reactions are of immediate relevance to many fields such as (bio)geochemistry, biomineralization, and environmental chemistry.

  1. Pyrite framboids associated with the Mesozoic Jehol Biota in northeastern China: Implications for microenvironment during early fossilization

    Institute of Scientific and Technical Information of China (English)


    Despite of the recent influx of reports describing important fossil specimens from the Mesozoic Jehol Biota, detailed information on the mechanism of fossilization and paleoenvironment in which these fossils were deposited is scanty. We present an analysis of microenvironment based upon scanning electron microscope observations of in situ pyrite framboids and microcrystallines of plant and vertebrate feather fossils in the Jehol Biota. Pyrite microcrystallines and framboids occur extensively inside and on surface of plant fossils.Framboids found on feathers and in sedimentary matrix were in a lower abundance. These framboids have diameters ranging from 6 μm to 31 μm with an average of 20 μm, indicating a dysoxic aqueous condition with free oxygen level less than 30 μmol/L for the microenvironment where these framboids were formed. The outgrowth of framboids inside plant tissues suggests the presence of water molecules and free oxygen at the cellular level during pyritization; the relative timing between tissue decay and framboid formation implies a rapid tissue degradation occurred during the very early stage of fossilization. This line of reasoning is consistent with the observation that cell level structure of plant fossils from these deposits is rarely preserved. We propose a "fossil envelop" model to accommodate the different geochemical conditions between the microenvironment surrounding the fossil material and the macroenvironment of background lake bottom water.

  2. Deep subsurface sulfate reduction and methanogenesis in the Iberian Pyrite Belt revealed through geochemistry and molecular biomarkers. (United States)

    Puente-Sánchez, F; Moreno-Paz, M; Rivas, L A; Cruz-Gil, P; García-Villadangos, M; Gómez, M J; Postigo, M; Garrido, P; González-Toril, E; Briones, C; Fernández-Remolar, D; Stoker, C; Amils, R; Parro, V


    The Iberian Pyrite Belt (IPB, southwest of Spain), the largest known massive sulfide deposit, fuels a rich chemolithotrophic microbial community in the Río Tinto area. However, the geomicrobiology of its deep subsurface is still unexplored. Herein, we report on the geochemistry and prokaryotic diversity in the subsurface (down to a depth of 166 m) of the Iberian Pyritic belt using an array of geochemical and complementary molecular ecology techniques. Using an antibody microarray, we detected polymeric biomarkers (lipoteichoic acids and peptidoglycan) from Gram-positive bacteria throughout the borehole. DNA microarray hybridization confirmed the presence of members of methane oxidizers, sulfate-reducers, metal and sulfur oxidizers, and methanogenic Euryarchaeota. DNA sequences from denitrifying and hydrogenotrophic bacteria were also identified. FISH hybridization revealed live bacterial clusters associated with microniches on mineral surfaces. These results, together with measures of the geochemical parameters in the borehole, allowed us to create a preliminary scheme of the biogeochemical processes that could be operating in the deep subsurface of the Iberian Pyrite Belt, including microbial metabolisms such as sulfate reduction, methanogenesis and anaerobic methane oxidation. © 2013 John Wiley & Sons Ltd.

  3. Thermal-sprayed, thin-film pyrite cathodes for thermal batteries -- Discharge-rate and temperature studies in single cells

    Energy Technology Data Exchange (ETDEWEB)



    Using an optimized thermal-spray process, coherent, dense deposits of pyrite (FeS{sub 2}) with good adhesion were formed on 304 stainless steel substrates (current collectors). After leaching with CS{sub 2} to remove residual free sulfur, these served as cathodes in Li(Si)/FeS{sub 2} thermal cells. The cells were tested over a temperature range of 450 C to 550 C under baseline loads of 125 and 250 mA/cm{sup 2}, to simulate conditions found in a thermal battery. Cells built with such cathodes outperformed standard cells made with pressed-powder parts. They showed lower interracial resistance and polarization throughout discharge, with higher capacities per mass of pyrite. Post-treatment of the cathodes with Li{sub 2}O coatings at levels of >7% by weight of the pyrite was found to eliminate the voltage transient normally observed for these materials. Results equivalent to those of standard lithiated catholytes were obtained in this manner. The use of plasma-sprayed cathodes allows the use of much thinner cells for thermal batteries since only enough material needs to be deposited as the capacity requirements of a given application demand.

  4. Application of the pyrite ash in the microwave Fenton process of decolorization of the synthetic color solution

    Directory of Open Access Journals (Sweden)

    Bečelić-Tomin Milena R.


    Full Text Available The aim of this study is to investigate the possibility of fly ash and pyrite ash applications as a Fenton catalysts in the advancement of the microwave/hydrogen peroxide (MW/H2O2 treatment in the Rhodamine B decolorization process. At the same time, a comparison of the influence of these heterogenous catalysts with the homogenous Fenton catalyst on the decolorization process was conducted. The influence of the catalyst was tracked in previously optimized conditions MW/H2O2: [Rhodamine B] = 0.2 mM; pH 3.2; temperature 85ºC; [H2O2] = 80 mM; power = 300 W. Under such conditions, the efficiency of 99.5% was achieved after 30 minutes of reaction time. The same efficiency was achieved through the application of MW/Fe2+/H2O2 and MW/pyrite ash/H2O2 after only 10 minutes of reaction time. The order of the tested integrated processes according to the initial reaction rate is as follows: MW/Fe2+/H2O2>MW/fly ash/H2O2>MW/H2O2. The results of this study present a basis for further research and optimization of water solution decolorization process through pyrite ash with MW and hydrogen peroxide application.

  5. An Innovative Approach to Separate Iron Oxide Concentrate from High-sulfur and Low-grade Pyrite Cinders

    Institute of Scientific and Technical Information of China (English)

    Yong LI; Fu-chun ZHOU; Zhao-xin ZHOU; Zhi-han TIAN; Chao YANG; Xi-ke TIAN


    High-sulfur and low-grade pyrite cinders are the waste products of sulfuric acid manufacturing plants. Many valuable components,such as iron oxide,are contained in pyrite cinders and difficult to be separated and puri-fied j ust via the high temperature roasting process.Considering this,an innovative method including water-washing, aqua regia leaching,hydrothermal alkali activation and acid-washing was developed.And the effects of different pa-rameters on recovery efficiency of iron oxide were systematically investigated.The optimum parameters were pro-posed as follows:water rinse-leaching at room temperature for 5-20 min,and melting at 160 ℃ for 2.0 h with NaOH (concentration of 30 mass%),followed by leaching with aqua regia solution (3.0 vol.%)for 1.0 h.After the treatment,the content of iron oxides increased from 54.3 to 96.0 mass% with the recovery rate exceeding 85%. Meanwhile,calcium sulphate was recovered as the high value-added products by alkali extraction liquid.Further-more,the phase transformation and microstructure of the samples in the process were studied by physicochemical methods to reveal the separation mechanisms of different components in the pyrite cinders.

  6. Single grain Rb-Sr dating of euhedral and cataclastic pyrite from the Qiyugou gold deposit in western Henan,central China

    Institute of Scientific and Technical Information of China (English)

    HAN YiGui; LI XiangHui; ZHANG ShiHong; ZHANG YuanHou; CHEN FuKun


    The Rb-Sr isotopic dating of pyrite mineral from ore deposits can directly provide mineralization age. However,many geological factors may affect the Rb-Sr isotopic system,which baffles application of this method. Employing ultra-low procedural blank Rb-Sr method,we have dated pyrites separated from the No. 4 breccia pipe of the Qiyugou gold deposit,western Henan Province. Single grains of euhedral pyrite crystal with few micro-cracks yield an isochron age of 126 ± 11 Ma,which represents time of the main mineralization stage of the deposit. Pyrite grains of cataclastic type show nevertheless scattered Rb-Sr isotopic composition and no reasonable isochron can be defined. Crystal morphology and mineral inclusion studies reveal that Rb and Sr of pyrite mineral probably are preserved mainly in biotite,K-feldspar,and sericite mineral inclusions. The dating results likely suggest that cataclastic pyrite is not suitable for the Rb-Sr dating due to modification of the Rb-Sr isotopic system by later hydrothermal activity of fluid.

  7. Quantifying Fenton reaction pathways driven by self-generated H2O2 on pyrite surfaces (United States)

    Gil-Lozano, C.; Davila, A. F.; Losa-Adams, E.; Fairén, A. G.; Gago-Duport, L.


    Oxidation of pyrite (FeS2) plays a significant role in the redox cycling of iron and sulfur on Earth and is the primary cause of acid mine drainage (AMD). It has been established that this process involves multi-step electron-transfer reactions between surface defects and adsorbed O2 and H2O, releasing sulfoxy species (e.g., S2O32-, SO42-) and ferrous iron (Fe2+) to the solution and also producing intermediate by-products, such as hydrogen peroxide (H2O2) and other reactive oxygen species (ROS), however, our understanding of the kinetics of these transient species is still limited. We investigated the kinetics of H2O2 formation in aqueous suspensions of FeS2 microparticles by monitoring, in real time, the H2O2 and dissolved O2 concentration under oxic and anoxic conditions using amperometric microsensors. Additional spectroscopic and structural analyses were done to track the dependencies between the process of FeS2 dissolution and the degradation of H2O2 through the Fenton reaction. Based on our experimental results, we built a kinetic model which explains the observed trend of H2O2, showing that FeS2 dissolution can act as a natural Fenton reagent, influencing the oxidation of third-party species during the long term evolution of geochemical systems, even in oxygen-limited environments.

  8. Mycorrhizal Fungal Community of Poplars Growing on Pyrite Tailings Contaminated Site near the River Timok

    Directory of Open Access Journals (Sweden)

    Marina Katanić


    Full Text Available Background and Purpose: Mycorrhizal fungi are of high importance for functioning of forest ecosystems and they could be used as indicators of environmental stress. The aim of this research was to analyze ectomycorrhizal community structure and to determine root colonization rate with ectomycorrhizal, arbuscular mycorrhizal and endophytic fungi of poplars growing on pyrite tailings contaminated site near the river Timok (Eastern Serbia. Materials and Methods: Identification of ectomycorrhizal types was performed by combining morphological and anatomical characterization of ectomycorrhizae with molecular identification approach, based on sequencing of the nuclear ITS rRNA region. Also, colonization of poplar roots with ectomycorrhizal, arbuscular mycorrhizal and dark septated endophytic fungi were analysed with intersection method. Results and Conclusions: Physico-chemical analyses of soil from studied site showed unfavourable water properties of soil, relatively low pH and high content of heavy metals (copper and zinc. In investigated samples only four different ectomycorrhizal fungi were found. To the species level were identified Thelephora terrestris and Tomentella ellisi, while two types remained unidentified. Type Thelephora terrestris made up 89% of all ectomycorrhizal roots on studied site. Consequently total values of Species richness index and Shannon-Weaver diversity index were 0.80 and 0.43, respectively. No structures of arbuscular mycorrhizal fungi were recorded. Unfavourable environmental conditions prevailing on investigated site caused decrease of ectomycorrhizal types diversity. Our findings point out that mycorrhyzal fungal community could be used as an appropriate indicator of environmental changes.

  9. Interaction of limestone grains and acidic solutions from the oxidation of pyrite tailings

    Energy Technology Data Exchange (ETDEWEB)

    Simon, M. [Departamento de Edafologia, EPS-CITE IIB, Canada San Urbano, Universidad de Almeria, 04120 Almeria (Spain)]. E-mail:; Martin, F. [Departamento de Edafologia, Facultad de Ciencias, Universidad de Granada, 18002 Granada (Spain); Garcia, I. [Departamento de Edafologia, EPS-CITE IIB, Canada San Urbano, Universidad de Almeria, 04120 Almeria (Spain); Bouza, P. [Centro Nacional Patagonico, CONICEF, Boulevard Brown s/n, 9120 Puerto Madryn, Chubut (Argentina); Dorronsoro, C. [Departamento de Edafologia, Facultad de Ciencias, Universidad de Granada, 18002 Granada (Spain); Aguilar, J. [Departamento de Edafologia, Facultad de Ciencias, Universidad de Granada, 18002 Granada (Spain)


    To characterise the coatings formed and to analyse element partitioning between the aqueous and solid phase, suspensions were prepared with four grain sizes of limestone and three different amounts of acidic solution from oxidized pyrite tailings. In all cases, red coatings with three different layers covered the grain surface, sealing off the acidic solution. The inner layer was composed mainly of basaluminite, the middle layer of schwertmannite, and the outer layer of gypsum and jarosite. Zn, Cd and Tl were co-precipitated by Fe and Al; As and Pb were co-precipitated almost completely by Fe; and Cu formed mainly Cu sulphates. All trace elements reached almost total precipitation at pH 6.3, but the precipitation of As and Pb tended to decrease as the pH rose. Consequently, liming should be calculated so that the soil pH does not exceed 6.3. This calculation should take into account that the armouring of the limestone grains can cause underestimations in the amount of liming material needed. - Basaluminite, schwertmannite and jarosite armored the limestone grains, and almost all trace elements co-precipitated, but the precipitation of As and Pb tended to decrease as the pH rose.

  10. Leachability and physical stability of solidified and stabilized pyrite cinder sludge from dye effluent treatment

    Directory of Open Access Journals (Sweden)

    Kerkez Đurđa V.


    Full Text Available This work is concerned with exploring the possibilities of using solidification/stabilization (S/S treatment for toxic sludge generated in dye effluent treatment, when pyrite cinder is used as catalytic iron source in the modified heterogeneous Fenton process. S/S treatment was performed by using different clay materials (kaolin, bentonite and native clay from the territory of Vojvodina and fly ash in order to immobilize toxic metals and arsenic presented in sludge. For the evaluation of the extraction potential of toxic metals and the effectiveness of the S/S treatment applied, four single-step leaching tests were performed. Leaching test results indicated that all applied S/S treatments were effective in immobilizing toxic metals and arsenic presented in sludge. X-ray diffraction analysis confirmed the formation of pozzolanic products, and compressive strength measurement proved the treatment efficacy. It can be concluded that the S/S technique has significant potential for solving the problem of hazardous industrial waste and its safe disposal. [Projekat Ministarstva nauke Republike Srbije, br. III43005 i br. TR37004

  11. Phytoremediation trials on metal- and arsenic-contaminated pyrite wastes (Torviscosa, Italy)

    Energy Technology Data Exchange (ETDEWEB)

    Vamerali, Teofilo [Department of Environmental Sciences, University of Parma, Viale G.P. Usberti 11/A, 43100 Parma (Italy)], E-mail:; Bandiera, Marianna; Coletto, Lucia; Zanetti, Federica [Department of Environmental Agronomy and Crop Sciences, University of Padova, Viale dell' Universita 16, 35020 Legnaro - Padova (Italy); Dickinson, Nicholas M. [Faculty of Science, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF (United Kingdom); Mosca, Giuliano [Department of Environmental Agronomy and Crop Sciences, University of Padova, Viale dell' Universita 16, 35020 Legnaro - Padova (Italy)


    At a site in Udine, Italy, a 0.7 m layer of As, Co, Cu, Pb and Zn contaminated wastes derived from mineral roasting for sulphur extraction had been covered with an unpolluted 0.15 m layer of gravelly soil. This study investigates whether woody biomass phytoremediation is a realistic management option. Comparing ploughing and subsoiling (0.35 m depth), the growth of Populus and Salix and trace element uptake were investigated in both pot and field trials. Species differences were marginal and species selection was not critical. Impaired above-ground productivity and low translocation of trace elements showed that bioavailable contaminant stripping was not feasible. The most significant finding was of coarse and fine roots proliferation in surface layers that provided a significant sink for trace elements. We conclude that phytostabilisation and effective immobilisation of metals and As could be achieved at the site by soil amelioration combined with woody species establishment. Confidence to achieve a long-term and sustainable remediation requires a more complete quantification of root dynamics and a better understanding of rhizosphere processes. - In As- and metal-contaminated pyrite wastes, contaminant stripping is not feasible, and root foraging and quantification of root dynamics holds the key to stabilisation in woody species.

  12. Iron pyrite: Phase and shape control by facile hot injection method (United States)

    Trinh, Thanh Kieu; Pham, Viet Thanh Hau; Truong, Nguyen Tam Nguyen; Kim, Chang Duk; Park, Chinho


    Pure phases of cubic and spherical FeS2 nanocrystals (NCs) with the mean size of 80 nm and 30 nm, respectively, were obtained using trioctylamine and oleylamine as the solvents to dissolve the sulfur source via a facile and efficient hot injection method. The pure phase formation and shape control were strongly dependent on the concentration of active sulfur source (H2S) that could be formed by the reaction between the elemental sulfur and a primary amine. The chemically active sulfur source could facilitate the formation of a pure FeS2 phase from a FeS phase via a Fe3S4 phase. In addition, the active sulfur concentration is believed to be the main factor to drive the orientation attachment to obtain different shapes of FeS2 NCs. The obtained FeS2 pyrite NCs with excellent phase purity and good optical properties are believed to have potential applications to various energy devices including low-cost photovoltaics.

  13. Composition and spectra of copper-carotenoid sediments from a pyrite mine stream in Spain (United States)

    Garcia-Guinea, Javier; Furio, Marta; Sanchez-Moral, Sergio; Jurado, Valme; Correcher, Virgilio; Saiz-Jimenez, Cesareo


    Mine drainages of La Poderosa (El Campillo, Huelva, Spain), located in the Rio Tinto Basin (Iberian Pyrite Belt) generate carotenoid complexes mixed with copper sulfates presenting good natural models for the production of carotenoids from microorganisms. The environmental conditions of Rio Tinto Basin include important environmental stresses to force the microorganisms to accumulate carotenoids. Here we show as carotenoid compounds in sediments can be analyzed directly in the solid state by Raman and Luminescence spectroscopy techniques to identify solid carotenoid, avoiding dissolution and pre-concentration treatments, since the hydrous copper-salted paragenesis do not mask the Raman emission of carotenoids. Raman spectra recorded from one of these specimens' exhibit major features at approximately 1006, 1154, and 1520 cm-1. The bands at 1520 cm-1 and 1154 cm-1 can be assigned to in-phase Cdbnd C (γ-1) and Csbnd C stretching (γ-2) vibrations of the polyene chain in carotenoids. The in-plane rocking deformations of CH3 groups linked to this chain coupled with Csbnd C bonds are observed in the 1006 cm-1 region. X-irradiation pretreatments enhance the cathodoluminescence spectra emission of carotenoids enough to distinguish organic compounds including hydroxyl and carboxyl groups. Carotenoids in copper-sulfates could be used as biomarkers and useful proxies for understanding remote mineral formations as well as for terrestrial environmental investigations related to mine drainage contamination including biological activity and photo-oxidation processes.

  14. Environmental regulatory failure and metal contamination at the Giap Lai pyrite mine, Northern Vietnam. (United States)

    Håkan Tarras-Wahlberg, N; Nguyen, Lan T


    The causes for the failure in enforcement of environmental regulations at the Giap Lai pyrite mine in northern Vietnam are considered and the environmental impacts that are associated with this mine are evaluated. It is shown that sulphide-rich tailings and waste rock in the mining area represent significant sources of acid rock drainage (ARD). The ARD is causing elevated metal levels in downstream water bodies, which in turn, represent a threat to both human health and to aquatic ecosystems. Metal concentrations in impacted surface waters have increased after mine closure, suggesting that impacts are becoming progressively more serious. No post-closure, remediation measures have been applied at the mine, in spite of the existence of environmental legislation and both central and regional institutions charged with environmental supervision and control. The research presented here provides further emphasis for the recommendation that, while government institutions may need to be strengthened, and environmental regulations need to be in place, true on the ground improvement in environmental quality in Vietnam and in many other developing countries require an increased focus on promoting public awareness of industrial environmental issues.

  15. On the pore water chemistry effect on spectral induced polarization measurements in the presence of pyrite (United States)

    Placencia-Gómez, Edmundo; Slater, Lee D.


    In order to expand the application of the induced polarization (IP) method as a technique for monitoring metallic mineral dissolution and precipitation mechanisms, we studied the effects of variations in pore water chemistry on the spectral induced polarization (SIP) response of a mixture of silica-sand and pyrite particles in the laboratory. We investigated the dependence of the SIP response on both pore water conductivity and pH for various chemical compositions: redox-passive (P) versus redox-active (A) ions, using CaCl2 as P-ions, and FeSO4 and FeCl3 as A-ion brines. The effect of pore water chemistry was evaluated by means of a recently proposed volumetric specific capacitance model. The SIP response (IP-effect) was primarily determined by the pore water conductivity and the specific capacitance was only weakly dependent on the chemical composition and pHw. We found that the specific capacitance varies to first order over a limited range and approximates a single value (≈ 302 F m- 3 in average). However, variations in the specific capacitance as a function of active versus inactive ion chemistry might be important to consider when using IP to monitor specific mineral dissolution and precipitation processes.

  16. Geochronologic constraints on magmatic intrusions and mineralization of the Zhunuo porphyry copper deposit in Gangdese, Tibet

    Institute of Scientific and Technical Information of China (English)


    In situ zircon U-Pb ages for the recently discovered Zhunuo porphyry copper deposit in the western part of the Gangdese metallogenic belt in Tibet were determined by sensitive high-resolution ion microprobe (SHRIMP). The ages can be divided into two separate groups, reflecting more than four major tectono-magmatic events in the area. The 62.5±2.5 Ma age of inherited zircons may be related to the volcanic eruption of the Linzizong Group formed shortly after the India-Asia continental collision. The 50.1±3.6 Ma age most likely corresponds to the time of underplating of mantle-derived mafic magma in Gangdese. The 15.6±0.6 Ma age obtained from magmatic zircons is interpreted as the age of crystallization of the Zhunuo ore-forming porphyry. Finally, a molybdenite Re-Os isochron age of 13.72±0.62 Ma is consistent with another zircon U-Pb age of 13.3 ±0.2 Ma, representing the time of copper mineralization. These ages, in combination with available literature data, indicate that magmatic crystallization and copper mineralization in the Gangdese metallogenic belt became gradually younger westward, and further suggest that the Zhunuo porphyry copper deposit was formed in the same tectonic stage as other porphyry copper deposits in the eastern and central Gangdese belt. This conclusion provides critical information for future exploration of porphyry copper deposits in western Gangdese.

  17. Applications of dendrochronology and sediment geochronology to establish reference episodes for evaluations of environmental radioactivity

    Energy Technology Data Exchange (ETDEWEB)

    Waugh, W.J.; Carroll, J.; Abraham, J.D.; Landeen, D.S. [Roy F. Weston, Inc., U.S. Department of Energy, Grand Junction Office, 2597 B 3/4 Road, Grand Junction, CO 81503 (United States)


    Dendrochronology and sediment geochronology have been used to demonstrate retrospective monitoring of environmental radioactivity at United States Department of Energy (DOE) sites. {sup 14}C in annual growth rings of sagebrush preserved the temporal and spatial patterns of {sup 14}C resulting from dispersion downwind of a nuclear fuel processing facility at the Hanford Site in Washington State. As far as 10 km downwind of the facility, {sup 14}C concentrations were significantly higher in growth rings formed during a fuel processing episode than in rings produced during preoperational or postoperational episodes. An episode of uranium mill tailings deposition in pond sediments at the Grand Junction Office in Colorado was reconstructed using {sup 210}Pb geochronology constrained by a marker of peak {sup 137}Cs fallout. Uranium concentrations in ponds sediments deposited after the processing episode provide a reasonable cleanup standard. These reference episodes of environmental radioactivity reconstructed from measurements taken within contaminated environments can improve or replace reference area data as baseline information for dose reconstructions, risk assessments, and the establishment of cleanup standards. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  18. Chemical Abrasion Applied to LA-ICP-MS U–Pb Zircon Geochronology

    Directory of Open Access Journals (Sweden)

    Quentin G. Crowley


    Full Text Available Zircon (ZrSiO4 is the most commonly used mineral in U–Pb geochronology. Although it has proven to be a robust chronometer, it can suffer from Pb-loss or elevated common Pb, both of which impede precision and accuracy of age determinations. Chemical abrasion of zircon involves thermal annealing followed by relatively low temperature partial dissolution in HF acid. It was specifically developed to minimize or eliminate the effects of Pb-loss prior to analysis using Thermal Ionization Mass Spectrometry (TIMS. Here we test the application of chemical abrasion to Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS by analyzing zircons from both untreated and chemically abraded samples. Rates of ablation for high alpha-dose non-treated zircons are up to 25% faster than chemically abraded equivalents. Ablation of 91500 zircon reference material demonstrates a ca. 3% greater down-hole fractionation of 206Pb/238U for non-treated zircons. These disparities necessitate using chemical abrasion for both primary reference material and unknowns to avoid applying an incorrect laser induced fractionation correction. All treated samples display a marked increase in the degree of concordance and/or lowering of common Pb, thereby illustrating the effectiveness of chemical abrasion to LA-ICP-MS U–Pb zircon geochronology.

  19. Paleontology and geochronology of the Long Beach core sites and monitoring wells, Long Beach, California (United States)

    McDougall, Kristin; Hillhouse, John; Powell, Charles; Mahan, Shannon; Wan, Elmira; Sarna-Wojcicki, Andrei M.


    The U.S. Geological Survey's Focus on Quaternary Stratigraphy in Los Angeles (FOQUS-LA) project was a cooperative coring program between Federal, State, and local agencies. It was designed to provide a better understanding of earthquake potentials and to develop a stratigraphic model of the western Los Angeles Basin in California. The biostratigraphic, geochronologic, and paleoecologic analyses of eight wells drilled during the FOQUS-LA project are presented. These analyses are based on microfossils (benthic and planktic foraminifers), macrofossils, paleomagnetic stratigraphy, optically stimulated luminescence, thermoluminescence, radiocarbon dating, and tephrochronology. A geochronologic framework (incorporating paleomagnetism, luminescence, and tephrochronology) was used to calibrate the sequence stratigraphic units in the FOQUS-LA wells and also was used to calibrate the ages of the microfossil stage and zonal boundaries. The results of this study show that (1) the offshore California margin zones can be used in a nearshore setting, and (2) the California margin zonal scheme refines the chronostratigraphic resolution of the benthic foraminiferal biostratigraphic framework for the Pacific Coast. Benthic foraminiferal stages are modified by the recognition of an early Hallian substage, which is a faunal change recognized throughout the Los Angeles Basin. Although no detailed macrofossil zonations exist for the Quaternary of southern California, several species, whose distribution is regulated by the climatic conditions, are useful as secondary marker species in the shallower water deposits of the Los Angeles Basin.

  20. SHRIMP zircon U-Pb geochronology of Indosinian granites in Hunan Province and its petrogenetic implications

    Institute of Scientific and Technical Information of China (English)

    WANG Yuejun; FAN Weiming; LIANG Xinquan; PENG Touping; SHI Yuruo


    The SHRIMP zircon U-Pb geochronology of three typically Indosinian granitic plutons with peraluminous and potassium-rich affinities (Tangshi ultraunit for Weishan and Baimashan, and Longtan ultraunit for Guandimiao) is presented in Hunan Province, South China. The analyses of zircons from biotite monozonite granites for Weishan, Baimashan and Guandimiao plutons show the single and tight clusters on the concordia, and yield the weighted mean 206Pb/238U ages of 244±4, 243±3 and 239±3 Ma, respectively, representing the crystallized ages of these Indosinian granites. These data suggest that the Indosinian granitic plutons as previously thought formed at a narrow age span. In combination with other data, it is inferred that the Indosinian granites within the South China Block probably distributed in Hunan, Jiangxi, Guangxi and Guangdong provinces as planar shape, and were the derivation of the crustal materials in the intracontinental thickening setting. These precisely geochronological data provide important constraints for better understanding the spatiotemporal pattern of the Indosinian peraluminous granites and early Mesozoic tectonic evolution of the South China Block.

  1. Developement of the Potassium-Argon Laser Experiment (KArLE) for In Situ Geochronology (United States)

    Cohen, Barbara A.


    Absolute dating of planetary samples is an essential tool to establish the chronology of geological events, including crystallization history, magmatic evolution, and alteration. Thus far, radiometric geochronology of planetary samples has only been accomplishable in terrestrial laboratories on samples from dedicated sample return missions and meteorites. In situ instruments to measure rock ages have been proposed, but none have yet reached TRL 6, because isotopic measurements with sufficient resolution are challenging. We have begun work under the NASA Planetary Instrument Definition and Development Program (PIDDP) to develop the Potassium (K) - Argon Laser Experiment (KArLE), a novel combination of several flight-proven components that will enable accurate KAr isochron dating of planetary rocks. KArLE will ablate a rock sample, measure the K in the plasma state using laser-induced breakdown spectroscopy (LIBS), measure the liberated Ar using quadrupole mass spectrometry (QMS), and relate the two by measuring the volume of the abated pit using a optical methods such as a vertical scanning interferometer (VSI). Our preliminary work indicates that the KArLE instrument will be capable of determining the age of several kinds of planetary samples to 100 Myr, sufficient to address a wide range of geochronology problems in planetary science. Additional benefits derive from the fact that each KArLE component achieves analyses common to most planetary surface missions.

  2. Geology, alteration, mineralization, petrogenesis, geochronology, geochemistry and airborne geophysics of Kuh Shah prospecting area, SW Birjand

    Directory of Open Access Journals (Sweden)

    Maryam Abdi


    Full Text Available The Kuh Shah prospecting area is located in Tertiary volcano-plutonic belt of the Lut Block. More than seventeen subvolcanic intermediate to acidic intrusive rocks, diorite to syenite in composition, were identified in the study area. The intrusions are related to hydrothermal alteration zones and contain argillic, propylitic, advanced argillic, silicified, quartz-sericite-pyrite, gossan and hydrothermal breccia which overprinted to each other and are accompanied by weathering which made it complicated to distinguish zoning. Mineralization is observed as sulfide (pyrite and rare chalcopyrite, disseminated Fe-oxides and quartz-Fe-oxide stockwork veinlets. Intrusive rocks are metaluminous, calc-alkaline with shoshonitic affinity with high values of magnetic susceptibility. The Kuh Shah intrusive rocks are classified as magnetite-series of oxidant I-type granitoids. Based on zircon U–Pb age dating, the age of these granitoid rocks is 39.7± 0.7 Ma (Middle Eocene. The radioisotope data (initial 87Sr/86Sr and 143Nd/144Nd ratios as well as εNd and geochemical data suggest that the Kuh Shah granitoid rocks formed from depleted mantle in a subduction-related magmatic arc setting. Geochemical anomalies of elements such as Cu, Au, Fe, Pb, Zn, As, Sb, Mo, Bi, Hg and also Mn, Ba, Te and Se, correlated with quartz-sericite-pyrite, gossan-stockwork-hydrothermal breccias, irregular silicified bodies and advanced argillic hydrothermal alteration zones. Geophysical anomalies correlated with hydrothermal alteration and mineralization zones. The interpretation of the results represents complex patterns of sub-circular to ellipsoid shape with north-east to south-west direction. These evidences are similar to the other for known Cu-Au porphyry and Au-epithermal systems in Iran and worldwide.

  3. Continued Development of in Situ Geochronology for Planetary Using KArLE (Potassium-Argon Laser Experiment) (United States)

    Devismes, D.; Cohen, B. A.


    Geochronology is a fundamental measurement for planetary samples, providing the ability to establish an absolute chronology for geological events, including crystallization history, magmatic evolution, and alteration events, and providing global and solar system context for such events. The capability for in situ geochronology will open up the ability for geochronology to be accomplished as part of lander or rover complement, on multiple samples rather than just those returned. An in situ geochronology package can also complement sample return missions by identifying the most interesting rocks to cache or return to Earth. The K-Ar radiometric dating approach to in situ dating has been validated by the Curiosity rover on Mars as well as several laboratories on Earth. Several independent projects developing in situ rock dating for planetary samples, based on the K-Ar method, are giving promising results. Among them, the Potassium (K)-Argon Laser Experiment (KArLE) at MSFC is based on techniques already in use for in planetary exploration, specifically, Laser-induced Breakdown Spectroscopy (LIBS, used on the Curiosity Chemcam), mass spectroscopy (used on multiple planetary missions, including Curiosity, ExoMars, and Rosetta), and optical imaging (used on most missions).

  4. Platinum-group element concentrations in pyrite from the Main Sulfide Zone of the Great Dyke of Zimbabwe (United States)

    Piña, R.; Gervilla, F.; Barnes, S.-J.; Oberthür, T.; Lunar, R.


    The Main Sulfide Zone (MSZ) of the Great Dyke of Zimbabwe hosts the world's second largest resource of platinum-group elements (PGE) after the Bushveld Complex in South Africa. The sulfide assemblage of the MSZ comprises pyrrhotite, pentlandite, chalcopyrite, and minor pyrite. Recently, several studies have observed in a number of Ni-Cu-PGE ore deposits that pyrite may host significant amounts of PGE, particularly Pt and Rh. In this study, we have determined PGE and other trace element contents in pyrite from the Hartley, Ngezi, Unki, and Mimosa mines of the Great Dyke by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Based on the textures and PGE contents, two types of pyrite can be differentiated. Py1 occurs as individual euhedral or subhedral grains or clusters of crystals mostly within chalcopyrite and pentlandite, in some cases in the form of symplectitic intergrowths, and is PGE rich (up to 99 ppm Pt and 61 ppm Rh; 1.7 to 47.1 ppm Ru, 0.1 to 7.8 ppm Os, and 1.2 to 20.2 ppm Ir). Py2 occurs as small individual euhedral or subhedral crystals within pyrrhotite, pentlandite, and less frequently within chalcopyrite and silicates and has low PGE contents (<0.11 ppm Pt, <0.34 ppm Rh, <2.5 ppm Ru, <0.37 ppm Ir, and <0.40 ppm Os). Py1 contains higher Os, Ir, Ru, Rh, and Pt contents than the associated pyrrhotite, pentlandite, and chalcopyrite, whereas Py2 has similar PGE contents as coexisting pyrrhotite and pentlandite. Based on the textural relationships, two different origins are attributed for each pyrite type. Py1 intergrowth with pentlandite and chalcopyrite is inferred to have formed by late, low temperature (<300 °C) decomposition of residual Ni-rich monosulfide solid solution, whereas Py2 is suggested to have formed by replacement of pyrrhotite and pentlandite caused by late magmatic/hydrothermal fluids.

  5. Bacterial Disproportionation of Elemental Sulfur Inferred from a Field Study of Stable-Isotope Fractionations between Elemental Sulfur and Pyrite (United States)

    Hardisty, D.; Pratt, L. M.; Olyphant, G. A.; Bell, J.; Johnson, A.


    Elemental sulfur (ES) is a common product of pyrite oxidation during acid mine drainage (AMD), but bacterial disproportionation of ES has not previously been inferred in acidic environments. Pore water profiles were collected seasonally within a coal-mine waste deposit, Minnehaha, in Southwest Indiana that has been abandoned for over 30 years. Geochemical characterization and modeling were used to assess how the interactions between the sulfur and iron cycle are affected by seasonally dynamic hydrologic conditions. Pore waters were collected seasonally and concentrations of Fe-species and sulfur isotopic compositions of sulfate were determined. Additionally, a sediment core was collected and used for sequential extraction and isotopic characterization of solid-phase sulfur species including elemental sulfur (δ34Ses), pyrite (δ34Spy), acid-volatile sulfides, water-soluble sulfates, and acid-soluble sulfates. The dominant disulfide phase was found to be pyrite through x-ray diffraction of an additional sediment core. Sulfur isotope fractionations between δ34Spy and δ34Ses (Δ34Ses-py) of up to -33% are inferred to indicate bacterial disproportionation of ES in the presence of a non-limiting sulfide 'scrub' Fe(III). The initial isotopic composition, following formation from pyrite oxidation, is inferred from δ34Spy, found to be ≈ 8.75% at the study site. Although ES has previously been found to accumulate in acidic Fe(III)-rich pore waters, ES is typically assumed to account for less than 1% of the oxidized sulfur pool and measurements of the ES isotopic composition are often neglected during field studies of acid AMD. The pore waters at Minnehaha were seasonally suboxic with sharp transitions from Fe(III)- to Fe(II)- dominated conditions near the phreatic surface. It is hypothesized that the sulfide product of ES disproportionation, fractionated by up to -8.6%, is immediately re-oxidized to ES near the redox gradient via reaction with Fe(III). Sulfide re

  6. Comparison of Different Methods for Determination of Pyrite Oxidation Rate in Wate Rock Pile at Mine Doyon, Quebec, Canada (United States)

    Sracek, O.; Nicholson, R.; Gélinas, P.; Lefebvre, R.


    Mine Doyon is a gold mine located close to Noranda, Québec, Canada. The South waste rock pile contains mostly highly friable sericite schists with pyrite content up to 7 wt percent. Oxidation of pyrite resulted in the production of acid mine drainage with pH values of about 2.0, and sulfate concentrations in pore water above 200 g/L. The waste rock material is characterized by high permeability allowing thermally driven convective supply of oxygen at temperatures reaching up to 67oC close to the slopes of the pile. Several methods for the determination of pyrite oxidation rate (POR) in waste rock have been compared and evaluated. Methods based on data collected in situ such as the interpretation of oxygen concentration profiles in waste rock pile and pyrite concentrations in solid phase were compared with the oxygen consumption method (OCM) in the laboratory. Analytical 1-D solution based on oxygen and temperature profiles in the pile was used for preliminary determination of POR. Analytical modeling results were used as an input for 2-D numerical model using TOUGH AMD. POR values based on pyrite mass balance (PMB) in solid phase were also calculated, assuming that average pyrite content in the deep, almost non-oxidized zone of the pile represents pre-oxidation conditions. Calculations were performed for prismatic columns with 1 m2 base. An approach based on dissolved sulfate mass balance was not used because of the lack of data from early stage of the pile and the non-conservative behavior of sulfate (precipitation of gypsum and jarosite in the pile). Finally, the oxygen consumption method (OCM) in the laboratory was based on oxygen concentration decline in headspace of closed chamber, where samples of waste rock sprinkled by water were located. Both fresh samples from mining operation and partially weathered samples collected in the pile were used. A range of POR values (mol(O2).kg-1.s-1) were obtained from the various methods. At Site 6 on the slope of the pile

  7. Multiple sulfur isotope constraints on sulfate-driven anaerobic oxidation of methane: Evidence from authigenic pyrite in seepage areas of the South China Sea (United States)

    Lin, Zhiyong; Sun, Xiaoming; Strauss, Harald; Lu, Yang; Gong, Junli; Xu, Li; Lu, Hongfeng; Teichert, Barbara M. A.; Peckmann, Jörn


    Multiple sulfur isotope signatures and secondary ion mass spectroscopy (SIMS) sulfur isotope compositions of pyrite from two seafloor sites (DH-CL11 and HD109) in seepage areas of the South China Sea were measured in order to study isotope effects of sulfate-driven anaerobic oxidation of methane (SO4-AOM). The multiple sulfur isotopes of pyrite reveal variable ranges for both sites (δ34S: between -44.1‰ and -2.9‰ for DH-CL11 and between -43.8‰ and -1.6‰ for HD109; Δ33S: between 0.02‰ and 0.17‰ for DH-CL11 and between -0.03‰ and 0.14‰ for HD109). SIMS analysis reveals an extreme variability of δ34S values (between -50.3‰ and -2.7‰ in DH-CL11; between -50.1 and 52.4‰ in HD109) for three types of pyrite: (1) framboids, (2) zoned aggregates with radial overgrowth surrounding a framboidal core, and (3) euhedral pyrite crystals. The synchronous changes of geochemical proxies (sulfate and methane concentrations, δ34Ssulfate and δ18Osulfate, δ34Spyrite, and pyrite content) at the sulfate-methane transition zone (SMTZ) at site DH-CL11 are interpreted to be induced by SO4-AOM under steady state conditions. In contrast, pyrite content and δ34S value fluctuations throughout core HD109 suggest that the sediment at this site was affected by multiple pyritization events during diagenesis. Multiple sulfur isotope signatures of early diagenetic pyrite (i.e., with low and high δ34S values, the latter above 315 cmbsf in DH-CL11; above 70 cmbsf in HD109) in the upper sediment column suggest that organoclastic sulfate reduction (OSR) and sulfur disproportionation generated the observed isotopic signatures. In contrast to the early diagenetic 34S depleted framboids, the higher SIMS δ34S values of overgrowth and euhedral crystals suggest a late diagenetic 34S enriched pool of dissolved sulfide derived from SO4-AOM at the current and paleo-SMTZs. Interestingly, pyrite resulting from SO4-AOM in the SMTZ at site DH-CL11 reveals a distinct pattern with higher

  8. The role of dissolved molecular oxygen in abiotic pyrite oxidation under acid pH conditions - Experiments with {sup 18}O-enriched molecular oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Heidel, Claudia, E-mail: [Institute of Mineralogy, TU Bergakademie Freiberg, Brennhausgasse 14, 09599 Freiberg (Germany); Tichomirowa, Marion [Institute of Mineralogy, TU Bergakademie Freiberg, Brennhausgasse 14, 09599 Freiberg (Germany)


    Research highlights: {yields} A small amount of molecular oxygen is permanently incorporated into sulfate during pyrite oxidation. {yields} Molecular oxygen may be incorporated into sulfate by sulfite oxidation and tetrathionate oxidation. {yields} Molecular oxygen is incorporated into water molecules during its cathodic reduction. {yields} Molecular oxygen mainly accepts electrons from pyrite and minor from dissolved and adsorbed ferrous iron. - Abstract: Several O isotope studies have shown that SO{sub 4}{sup 2-} produced from aqueous pyrite oxidation mainly contains water-derived O and minor atmospherically-derived O{sub 2}. However, the incorporation of O{sub 2} into SO{sub 4}{sup 2-} has been shown to decrease continuously during pyrite oxidation experiments. Hence, it remains uncertain if (and how) O{sub 2} is permanently incorporated into SO{sub 4}{sup 2-} during pyrite oxidation. Abiotic aerobic batch pyrite oxidation experiments in aqueous solutions were performed under acid pH conditions. After 151 days, {sup 18}O-enriched O{sub 2} was injected into the headspace of the reaction vessels. Increasing {delta}{sup 18}O{sub SO{sub 4}} values with increasing injection volume of {sup 18}O-enriched O{sub 2} indicated the permanent incorporation of about 9% O{sub 2} into the produced SO{sub 4}{sup 2-} during pyrite oxidation from 151 to 201 days. Molecular oxygen may be incorporated into SO{sub 4}{sup 2-} by oxidation of the S intermediate species sulfite (and maybe tetrathionate) into SO{sub 4}{sup 2-}. However, only 4% of the O{sub 2} consumed during the experiments was incorporated into SO{sub 4}{sup 2-}. Slightly increased {delta}{sup 18}O{sub H{sub 2}O} values from experiments with the largest injection of {sup 18}O-enriched O{sub 2} indicated the incorporation of O{sub 2} into water molecules which may proceed during the cathodic reduction of O{sub 2}. Thus, O{sub 2} was an important electron acceptor under aerobic acid conditions. The observed {epsilon

  9. Subsurface mapping in the Iberian Pyrite Belt using seismic reflection profiling and potential-field data (United States)

    Carvalho, João; Inverno, Carlos; Matos, João Xavier; Rosa, Carlos; Granado, Isabel; Branch, Tim; Represas, Patrícia; Carabaneanu, Livia; Matias, Luís; Sousa, Pedro


    The Iberian Pyrite Belt (IPB) hosts world-class massive sulphide deposits, such as Neves-Corvo in Portugal and Rio Tinto in Spain. In Portugal, the Palaeozoic Volcanic-Sedimentary Complex (VSC) hosts these ore deposits, extending from the Grândola-Alcácer region to the Spanish border with a NW-SE to WNW-ESE trend. In the study area, between the Neves-Corvo mine region and Alcoutim (close to the Spanish border), the VSC outcrops only in a small horst near Alcoutim. Sparse exploration drill-hole data indicate that the depth to the top of the VSC varies from several 100 m to about 1 km beneath the Mértola Formation Flysch cover. Mapping of the VSC to the SE of Neves-Corvo mine is an important exploration goal and motivated the acquisition of six 2D seismic reflection profiles with a total length of approximately 82 km in order to map the hidden extension of the VSC. The data, providing information deeper than 10 km at some locations, were integrated in a 3D software environment along with potential-field, geological and drill-hole data to form a 3D structural framework model. Seismic data show strong reflections that represent several long Variscan thrust planes that smoothly dip to the NNE. Outcropping and previously unknown Late Variscan near-vertical faults were also mapped. Our data strongly suggest that the structural framework of Neves-Corvo extends south-eastwards to Alcoutim. Furthermore, the VSC top is located at depths that show the existence within the IPB of new areas with good potential to develop exploration projects envisaging the discovery of massive sulphide deposits of the Neves-Corvo type.

  10. Subsurface mapping in the Iberian Pyrite Belt using seismic reflection profiling and potential-field data (United States)

    Carvalho, João; Inverno, Carlos; Matos, João Xavier; Rosa, Carlos; Granado, Isabel; Branch, Tim; Represas, Patrícia; Carabaneanu, Livia; Matias, Luís; Sousa, Pedro


    The Iberian Pyrite Belt (IPB) hosts world-class massive sulphide deposits, such as Neves-Corvo in Portugal and Rio Tinto in Spain. In Portugal, the Palaeozoic Volcanic-Sedimentary Complex (VSC) hosts these ore deposits, extending from the Grândola-Alcácer region to the Spanish border with a NW-SE to WNW-ESE trend. In the study area, between the Neves-Corvo mine region and Alcoutim (close to the Spanish border), the VSC outcrops only in a small horst near Alcoutim. Sparse exploration drill-hole data indicate that the depth to the top of the VSC varies from several 100 m to about 1 km beneath the Mértola Formation Flysch cover. Mapping of the VSC to the SE of Neves-Corvo mine is an important exploration goal and motivated the acquisition of six 2D seismic reflection profiles with a total length of approximately 82 km in order to map the hidden extension of the VSC. The data, providing information deeper than 10 km at some locations, were integrated in a 3D software environment along with potential-field, geological and drill-hole data to form a 3D structural framework model. Seismic data show strong reflections that represent several long Variscan thrust planes that smoothly dip to the NNE. Outcropping and previously unknown Late Variscan near-vertical faults were also mapped. Our data strongly suggest that the structural framework of Neves-Corvo extends south-eastwards to Alcoutim. Furthermore, the VSC top is located at depths that show the existence within the IPB of new areas with good potential to develop exploration projects envisaging the discovery of massive sulphide deposits of the Neves-Corvo type.

  11. Aerobic bacterial pyrite oxidation and acid rock drainage during the Great Oxidation Event. (United States)

    Konhauser, Kurt O; Lalonde, Stefan V; Planavsky, Noah J; Pecoits, Ernesto; Lyons, Timothy W; Mojzsis, Stephen J; Rouxel, Olivier J; Barley, Mark E; Rosìere, Carlos; Fralick, Phillip W; Kump, Lee R; Bekker, Andrey


    The enrichment of redox-sensitive trace metals in ancient marine sedimentary rocks has been used to determine the timing of the oxidation of the Earth's land surface. Chromium (Cr) is among the emerging proxies for tracking the effects of atmospheric oxygenation on continental weathering; this is because its supply to the oceans is dominated by terrestrial processes that can be recorded in the Cr isotope composition of Precambrian iron formations. However, the factors controlling past and present seawater Cr isotope composition are poorly understood. Here we provide an independent and complementary record of marine Cr supply, in the form of Cr concentrations and authigenic enrichment in iron-rich sedimentary rocks. Our data suggest that Cr was largely immobile on land until around 2.48 Gyr ago, but within the 160 Myr that followed--and synchronous with independent evidence for oxygenation associated with the Great Oxidation Event (see, for example, refs 4-6)--marked excursions in Cr content and Cr/Ti ratios indicate that Cr was solubilized at a scale unrivalled in history. As Cr isotope fractionations at that time were muted, Cr must have been mobilized predominantly in reduced, Cr(III), form. We demonstrate that only the oxidation of an abundant and previously stable crustal pyrite reservoir by aerobic-respiring, chemolithoautotrophic bacteria could have generated the degree of acidity required to solubilize Cr(III) from ultramafic source rocks and residual soils. This profound shift in weathering regimes beginning at 2.48 Gyr ago constitutes the earliest known geochemical evidence for acidophilic aerobes and the resulting acid rock drainage, and accounts for independent evidence of an increased supply of dissolved sulphate and sulphide-hosted trace elements to the oceans around that time. Our model adds to amassing evidence that the Archaean-Palaeoproterozoic boundary was marked by a substantial shift in terrestrial geochemistry and biology.

  12. Yeast diversity in the extreme acidic environments of the Iberian Pyrite Belt. (United States)

    Gadanho, Mário; Libkind, Diego; Sampaio, José Paulo


    In the Iberian Pyrite Belt (IPB), acid rock drainage gives rise to aquatic habitats with low pH and high concentrations of heavy metals, a situation that causes important environmental problems. We investigated the occurrence and diversity of yeasts in two localities of the IPB: São Domingos (Portugal) and Rio Tinto (Spain). Yeast isolation was performed on conventional culture media (MYP), acidified (pH 3) media (MYP3), and on media prepared with water from the study sites (MYPw). The main goal of the study was to determine the structure of the yeast community; a combination of molecular methods was used for accurate species identifications. Our results showed that the largest fraction of the yeast community was recovered on MYPw rather than on MYP and MYP3. Twenty-seven yeast species were detected, 48% of which might represent undescribed taxa. Among these, an undescribed species of the genus Cryptococcus required low pH for growth, a property that has not been observed before in yeasts. The communities of S. Domingos and R. Tinto showed a considerable resemblance, and eight yeast species were simultaneously found in both localities. Taking into consideration the physicochemical parameters studied, we propose a hierarchic organization of the yeast community in terms of high-, intermediate-, or low-stress conditions of the environment. According to this ranking, the acidophile yeast Cryptococcus sp. 5 is considered the most tolerant species, followed by Cryptococcus sp. 3 and Lecytophora sp. Species occurring in situations of intermediate environmental stress were Candida fluviatilis, Rhodosporidium toruloides, Williopsis californica, and three unidentified yeasts belonging to Rhodotorula and Cryptococcus.

  13. Magnetic pyrite cinder as an efficient heterogeneous ozonation catalyst and synergetic effect of deposited Ce. (United States)

    Wu, Deli; Liu, Ying; He, Hongping; Zhang, Yalei


    Heterogeneous catalytic ozonation was emerged to be a promising alternative in the mineralization of various persistent organic pollutants in recent decades. Magnetic pyrite cinder (PyC), which was employed as the catalyst in our investigation, was further deposited by Ce (Ce-PyC) to enhance its catalytic activity in the degradation of aqueous reactive black 5 (RB5). The results showed that additional 17.39%, 42.12% mineralization efficiency was obtained by O3/PyC, O3/Ce-PyC, respectively, in the degradation of RB5 compared to that of O3 alone under identical experimental condition. The reaction mechanism involved the enhanced mineralization of aqueous RB5 at the catalyst-solution interface via hydroxyl radicals produced by the reaction between O3 and catalyst surface. Besides surface hydroxyl, surface Ce(Ⅲ) was crucial for Ce-PyC in the enhanced generation of hydroxyl radicals. More surprisingly, it was found that both PyC and Ce-PyC could exert quite stable catalytic activity in a wide pH range from 3 to 10, which was supposed to be combined with inherently comprised various metal oxide, such as Fe2O3, Fe3O4, MnO2 and CuO. Ozone utilization evaluation demonstrated that PyC and Ce-PyC facilitated effective ozone decomposition, as ozone utilization efficiency (mgTOC/mgO3) of O3/PyC and O3/Ce-PyC increased 64.0%, 155.0%, respectively, compared to that of O3 alone. This investigation provided an effective alternative in the resource utilization of PyC, which was traditionally characterized as a waste material.

  14. Scanning ion imaging - a potent tool in SIMS U -Pb zircon geochronology (United States)

    Whitehouse, M. J.; Fedo, C.; Kusiak, M.; Nemchin, A.


    The application of high spatial resolution (BSE) characterisation, has revolutionised geochronology over the past 25 years, re-vealing complexities of crustal evolution from zoned zircons. In addition to ge-ochronology, such studies now commonly form the basis of broader investigations using O- and Hf- isotopes and trace elements obtained from the same growth zone as age, circumventing ambiguities commonly present in bulk-rock isotope studies. The choice of analytical beam diameter is often made to maximise the precision of data obtained from a given area of analysis within an identifiable growth zone. In cases where zircons yield poorly constrained internal structures in SEM, high spatial resolution spot analyses may yield uninterpretable and/or meaningless mixed ages by inadvertent sampling across regions with real age differences. Scanning ion imaging (SII) has the potential to generate accurate and precise geochrono-logical data with a spatial resolution down to ca. 2 μm, much higher than that of a normal spot analysis. SII acquisition utilises a rastered primary beam to image an area of the sample with a spatial resolution dependent on the selected primary beam diameter. On the Cameca ims1270/80 instruments, the primary beam scanning is coupled with the dynamic transfer optical system (DTOS) which deflects the secondary ions back on to the ion optical axis of the instrument regardless of where in the raster illuminated area the ions originated. This feature allows retention of a high field magnification (= high transmission) mode and the ability to operate the mass spectrometer at high mass resolution without any compromise in the quality of the peak shape. Secondary ions may be detected either in a sequential (peak hopping) mono-collection mode or simultaneous multicollection mode using low-noise pulse counting electron multipliers. Regardless of the detection mode, data are acquired over sufficient cycles to generate usable counting statistics from selected

  15. Microstructural and geochronology data of the Coacoyulillo-Intzcuinatoyac sector rocks, Guerrero state, Mexico (United States)

    Espejo Bautista, G.; Hernandez, T.; Elías, M.; Solari, L.


    The south of Mexico is constituted by many conjugated geological events with volcanic, sedimentary, tectonic, plutonic and metamorphic sequences. The exposed evidences establish the pieces of a complex puzzle which were analyzed in this study for geochronological and structural purposes in context with the observed field relationships. According to Campa and Coney (1983), Mexico is constituted by sixteen tectonostratigraphic terranes, which are distinguished by their basement petrology, although they can superficially share an identical geological record. The study area is located in a triple point where the Xolapa, Guerrero and Mixteca terranes converge and covers the adjacent areas to the Intzcuinatoyac and Coacoyulillo villages, southwest of the city of Chilpancingo in the Guerrero state. This study was performed in a region which is integrated by geological events covered by ductile-fragile regional deformation of great magnitude, consisting of mylonitic rocks and less than 60 to 132 Ma magmatic events, associated with a subduction scenario. The analyzed magmatic events are geographically distributed along the El Zapote and El Reparo rivers and can be classified into three different magmatic pulses, determined by field relations and geochronological data. However, the age of the deformations and deformational events were constrained by two or more magmatic and / or tectonic events. The oldest magmatism is represented by felsic intrusive rocks, which were later affected by ductile deformation, developing mylonitic textures. The deformed intrusive forms part of a mylonitic sector associated to a tectonic contact between the Xolapa, Mixteca and Guerrero terranes. This mylonitic sector can be correlated with other mylonitic areas within the state of Guerrero due to its ductile structural features and its geochronology, such as La Venta and the Ocotito areas. The mylonitic areas of Guerrero form a belt that may be associated with the Chacalapa fault in the state of

  16. Relationship between LIBS Ablation and Pit Volume for Geologic Samples: Applications for in situ Absolute Geochronology (United States)

    Devismes, D.; Cohen, Barbara A.


    In planetary sciences, in situ absolute geochronology is a scientific and engineering challenge. Currently, the age of the Martian surface can only be determined by crater density counting. However this method has significant uncertainties and needs to be calibrated with absolute ages. We are developing an instrument to acquire in situ absolute geochronology based on the K-Ar method. The protocol is based on the laser ablation of a rock by hundreds of laser pulses. Laser Induced Breakdown Spectroscopy (LIBS) gives the potassium content of the ablated material and a mass spectrometer (quadrupole or ion trap) measures the quantity of 40Ar released. In order to accurately measure the quantity of released 40Ar in cases where Ar is an atmospheric constituent (e.g., Mars), the sample is first put into a chamber under high vacuum. The 40Arquantity, the concentration of K and the estimation of the ablated mass are the parameters needed to give the age of the rocks. The main uncertainties with this method are directly linked to the measures of the mass (typically some µg) and of the concentration of K by LIBS (up to 10%). Because the ablated mass is small compared to the mass of the sample, and because material is redeposited onto the sample after ablation, it is not possible to directly measure the ablated mass. Our current protocol measures the ablated volume and estimates the sample density to calculate ablated mass. The precision and accuracy of this method may be improved by using knowledge of the sample's geologic properties to predict its response to laser ablation, i.e., understanding whether natural samples have a predictable relationship between laser energy deposited and resultant ablation volume. In contrast to most previous studies of laser ablation, theoretical equations are not highly applicable. The reasons are numerous, but the most important are: a) geologic rocks are complex, polymineralic materials; b) the conditions of ablation are unusual (for example

  17. In Situ Potassium-Argon Geochronology Using Fluxed Fusion and a Double Spike (United States)

    Hurowitz, Joel A.; Hecht, Michael H.; Zimmerman, Wayne F.; Neidholdt, Evan L.; Sinha, Mahadeva P.; Sturhahn, Wolfgang; Coleman, Max; McCleese, Daniel J.; Farley, Kenneth A.; Eiler, John M.; Rossman, George R.; Waltenberg, Kathryn


    A document highlights an Li-based fluxing agent that enables sample fusion and quantitative Ar-release at relatively low temperatures (900-1,000 C), readily achievable with current flight resistance furnace designs. A solid, double spike containing known quantities of Ar-39 and K-41 was developed that, when added in known amounts to a sample, enables the extraction of a Ar-40/K-40 ratio for age estimation without a sample mass measurement. The use of a combination of a flux and a double spike as a means of solving the mechanical hurdles to an in situ K-Ar geochronology measurement has never been proposed before. This methodology and instrument design would provide a capability for assessing the ages of rocks and minerals on the surfaces of planets and other rocky terrestrial bodies in the solar system.

  18. Preliminary K/Ar geochronology of the Crater Basalt volcanic field (CBVF, northern Patagonia

    Directory of Open Access Journals (Sweden)

    Z. Pécskay


    Full Text Available The Crater Basalt volcanic field is one of the Quaternary intraplate basaltic fields in northern Patagonia. A systematic geological, volcanological and geochronological study of CBVF indicates a multistage history of eruptions of basaltic volcanoes. K/Ar dating, using whole rock samples shows that the measured analytical ages are fully consistent with the available stratigraphic control. The radiometric ages fall into three distinct, internally consistent age groups, which give evidence that there were at least three major episodes of volcanic activity, at about 1.0 Ma, 0.6 Ma and 0.3 Ma ago. The age differences appear to be just significant, even although less than 10 % radiogenic argon was found in the isotope analysis of whole rock samples.

  19. Promise and Pitfalls of Lu/Hf-Sm/Nd Garnet Geochronology (United States)

    King, R. L.; Vervoort, J. D.; Kohn, M. J.; Zirakparvar, N. A.; Hart, G. L.; Corrie, S. L.; Cheng, H.


    Our ability to routinely measure Lu-Hf and Sm-Nd isotopes in garnet allows broad new applications in geochronology, petrology, and tectonics. However, applications of these data can be limited by challenges in interpreting the petrologic record and preparing garnets for analysis. Here, we examine petrologic and chemical pitfalls encountered in garnet geochronology. Petrologic factors influencing trace element compositions in garnet include reactions that modify REE availability and partitioning (1,2), kinetically limited transfer of REEs to garnet (3), and bulk compositional heterogeneities (4). Interpreting the effects of these processes on Sm/Nd and Lu/Hf ages requires characterizing REE zonation prior to isotope analysis and age interpretation. Because garnet fractions are traditionally picked from crushed samples without regard to intracrystalline origins or chemistries, isochrons will represent mixtures derived to varying degrees from all periods of garnet growth. While measured zoning might generally indicate what garnet portion dominates the Lu/Hf or Sm/Nd budget, traditional mineral separation will rarely realize the chronologic potential afforded by high precision Hf and Nd isotope measurements. The potential use of alternative techniques, such as microsampling, necessitates selective digestion and/or leaching to eliminate inclusions within garnet. For Sm/Nd geochronology, H2SO4 leaching removes LREE-rich phosphates (e.g. apatite), but not silicates (e.g. epidote), precluding Sm-Nd dating of some rocks. For Lu/Hf geochronology, ubiquitous zircon microinclusions (c. 1 μm) can significantly disrupt age determinations. Microinclusions cannot be detected optically or separated physically, requiring selective chemical digestion. If complete digestion methods, such as bomb digestion, are used for garnet fractions, then "common Hf" from zircon will be contained in final solutions. These mixed analyses are of dubious utility and will fall into one of two

  20. Mercury flux to estuarine sediments, derived from Pb-210 and Cs-137 geochronologies (Guaratuba Bay, Brazil)

    Energy Technology Data Exchange (ETDEWEB)

    Sanders, Christian J. [Departamento de Geoquimica, Universidade Federal Fluminense, 24020-007 Niteroi-RJ (Brazil)]. E-mail; Santos, Isaac R. [Department of Oceanography, Florida State University, Tallahassee, FL, 32306 (United States); Silva-Filho, Emmanoel V. [Departamento de Geoquimica, Universidade Federal Fluminense, 24020-007 Niteroi-RJ (Brazil); Patchineelam, Sambasiva R. [Departamento de Geoquimica, Universidade Federal Fluminense, 24020-007 Niteroi-RJ (Brazil)


    A sediment core from Guaratuba Bay was used to indicate possible Hg modifications to this coastal environment brought about by growing agricultural activity. Sedimentation rates were estimated to be 6.1 mm/year and 5.2 mm/year through {sup 21}Pb and {sup 137}Cs geochronologies, respectively. Mercury concentrations and organic matter ratios in the surface layers are greater than in the older sediments, supporting the hypothesis of anthropogenic enrichment. Results show that the Hg flux has raised more than twofold during the second half of the 20th century. These results point to the need for further studies to substantiate the hypothesis of anthropogenic enrichment and to quantify point sources of Hg to this estuary.

  1. Immobilization of toxic elements in mine residues derived from mining activities in the Iberian Pyrite Belt (SW Spain): Laboratory experiments

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Lopez, R.; Nieto, J.M.; de Almodovar, G.R. [University of Huelva, Huelva (Spain). Dept. of Geology


    In the mining environments of the Iberian Pyrite Belt (IPB), the oxidation of sulphide wastes generates acid drainage with high concentrations of SO{sub 4}, metals and metalloids (Acid Mine Drainage, AMD). These acid and extremely contaminated discharges are drained by the fluvial courses of the Huelva province (SW Spain) which deliver high concentrations of potentially toxic elements into the Gulf of Cadiz. In this work, the oxidation process of mine tailings in the IPB, the generation of AMD and the potential use of coal combustion fly ash as a possible alkaline treatment for neutralization of and metal removal from AMD, was studied in non-saturated column experiments. The laboratory column tests were conducted on a mine residue (71.6 wt% pyrite) with artificial rainfall or irrigation. A non-saturated column filled solely with the pyrite residue leached solutions with an acid pH (approx. 2) and high concentrations of SO{sub 4} and metals. These leachates have the same composition as typical AMD, and the oxidation process can be compared with the natural oxidation of mine tailings in the IPB. However, the application of fly ash to the same amount of mine residue in another two non-saturated columns significantly increased the pH and decreased the SO{sub 4} and metal concentrations in the leaching solutions. The improvement in the quality of leachates by fly ash addition in the laboratory was so effective that the leachate reached the pre-potability requirements of water for human consumption under EU regulations. The extrapolation of these experiments to the field is a promising solution for the decontamination of the fluvial courses of the IPB, and therefore, the decrease of pollutant loads discharging to the Gulf of Cadiz.

  2. A remediation strategy based on active phytoremediation followed by natural attenuation in a soil contaminated by pyrite waste

    Energy Technology Data Exchange (ETDEWEB)

    Clemente, Rafael [Department of Soil and Water Conservation and Organic Waste Management, Centro de Edafologia y Biologia Aplicada del Segura, CSIC, Campus Universitario de Espinardo, Apartado 164, 30100 Espinardo, Murcia (Spain)]. E-mail:; Almela, Concepcion [Instituto de Agroquimica y Tecnologia de Alimentos, CSIC, Apartado 73, 46100 Burjassot, Valencia (Spain); Bernal, M. Pilar [Department of Soil and Water Conservation and Organic Waste Management, Centro de Edafologia y Biologia Aplicada del Segura, CSIC, Campus Universitario de Espinardo, Apartado 164, 30100 Espinardo, Murcia (Spain)


    Phytoremediation of metal-polluted soils can be promoted by the proper use of soil amendments and agricultural practices. A 4-year phytoremediation programme was applied to a site affected by the toxic spill of pyrite residue at Aznalcollar (Spain) in 1998, contaminated with heavy metals (Zn, Cu, Pb, Cd) and arsenic. This consisted of active phytoremediation, using organic amendments (cow manure and compost) and lime and growing two successive crops of Brassica juncea (L.) Czern., followed by natural attenuation without further intervention. Changes in soil pH, extractable metal and As concentrations, organic carbon content and microbial biomass was evaluated. The initial oxidation of metal sulphides from pyrite residues released soluble metals and reduced soil pH to extremely acidic values (mean 4.1, range 2.0-7.0). The addition of lime (up to 64 t ha{sup -1}) increased soil pH to adequate values for plant growth, resulting in a significant decrease in DTPA-extractable metal concentrations in all plots. Natural attenuation phase showed also a decrease in extractable metals. Organic treatments increased the soil total organic carbon, which led to higher values of microbial biomass (11.6, 15.2 and 14.9 g kg{sup -1} TOC and 123, 170 and 275 {mu}g g{sup -1} biomass-C in control, compost and manure plots, respectively). Active phytoremediation followed by natural attenuation, was effective for remediation of this pyrite-polluted soil. - The addition of lime and organic amendments decreased heavy metal solubility and promoted Natural attenuation of a recently-contaminated soil.

  3. Effect of Surface Oxidation on Interfacial Water Structure at a Pyrite (100) Surface as Studied by Molecular Dynamics Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Jiaqi; Miller, Jan D.; Dang, Liem X.; Wick, Collin D.


    In the first part of this paper, a Scanning Electron Microscopy and contact angle study of a pyrite surface (100) is reported describing the relationship between surface oxidation and the hydrophilic surface state. In addition to these experimental results, the following simulated surface states were examined using Molecular Dynamics Simulation (MDS): fresh unoxidized (100) surface; polysulfide at the (100) surface; elemental sulfur at the (100) surface. Crystal structures for the polysulfide and elemental sulfur at the (100) surface were simulated using Density Functional Theory (DFT) quantum chemical calculations. The well known oxidation mechanism which involves formation of a metal deficient layer was also described with DFT. Our MDS results of the behavior of interfacial water at the fresh and oxidized pyrite (100) surfaces without/with the presence of ferric hydroxide include simulated contact angles, number density distribution for water, water dipole orientation, water residence time, and hydrogen-bonding considerations. The significance of the formation of ferric hydroxide islands in accounting for the corresponding hydrophilic surface state is revealed not only from experimental contact angle measurements but also from simulated contact angle measurements using MDS. The hydrophilic surface state developed at oxidized pyrite surfaces has been described by MDS, on which basis the surface state is explained based on interfacial water structure. The Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences (BES), of the DOE funded work performed by Liem X. Dang. Battelle operates the Pacific Northwest National Laboratory for DOE. The calculations were carried out using computer resources provided by BES.

  4. 硫铁矿烧渣的熟化及机理%Maturation of pyrite cinders and its mechanism

    Institute of Scientific and Technical Information of China (English)

    郑雅杰; 陈白珍; 龚竹青; 陈文汨


    研究了熟化法回收硫铁矿浇渣中的铁及其反应机 理。 将硫铁矿烧渣与硫酸混合后, 经过熟化处理可使烧渣中铁的回收率达到90%以上。 熟 化温度为100~300  ℃、 熟化时间1~2  h、 硫酸用量为理论用量的1.0~ 1.2倍以及硫酸浓度为65 %~85%时, 铁回收率较高。 表面电镜(SEM)实验表明熟化后烧渣变成晶状颗粒, X射线衍 射证实熟化烧渣中有FeH(SO4)2*4H2O生成。%The maturation of pyrite cinders for recovering iron and its mechanism were studied. The rate of iron recovery of pyrite cinder s is up to 90 % by maturation treatment after pyrite cinders mixing with sulfur acid. Higher rat e of iron recovery can be obtained when maturation temperature is 100~300  ℃, maturation time 1~2  h, sulfur acid 1~1.2 times of th eoretical quality and concentration of sulfur acid 65%~85%. SEM demonstrated t hat the globula r cinders become crystal grains after maturation. XRD analysis proved t hat FeH(SO4)2*4H2O is produced after maturation.

  5. Sedimentary pyrite δ34S differs from porewater sulfide in Santa Barbara Basin: Proposed role of organic sulfur (United States)

    Raven, Morgan Reed; Sessions, Alex L.; Fischer, Woodward W.; Adkins, Jess F.


    Santa Barbara Basin sediments host a complex network of abiotic and metabolic chemical reactions that knit together the carbon, sulfur, and iron cycles. From a 2.1-m sediment core collected in the center of the basin, we present high-resolution profiles of the concentrations and isotopic compositions of all the major species in this system: sulfate, sulfide (∑H2S), elemental sulfur (S0), pyrite, extractable organic sulfur (OS), proto-kerogen S, total organic and dissolved inorganic carbon, and total and reducible iron. Below 10 cm depth, the core is characterized by low apparent sulfate reduction rates (biogeochemical cycles and redox structure in sedimentary paleoenvironments.

  6. Contribution of Cistus ladanifer L. andCistus salvifolius L. for environmentla rehabilitation of mine areas from iberian pyrite belt


    Santos, Erika; Ferreira, Mara; Abreu, Maria Manuela


    The aim of this study was to evaluate the potential of combined use of Cistus ladanifer and Cistus salviifolius for environmental rehabilitation of abandoned mine areas from Iberian Pyrite Belt. Soils from São Domingos mine area are heterogeneous, due to different characteristics of the original materials, and showed high total concentrations of trace elements (1940- 3030 mg As kg-1; 210-237 mg Cu kg-1; 5280-9210 mg Pb kg-1). Available fractions of trace elements presented, in gen...

  7. Chalcopyrite dissolution: Scanning photoelectron microscopy examination of the evolution of sulfur species with and without added iron or pyrite (United States)

    Li, Yubiao; Qian, Gujie; Brown, Paul L.; Gerson, Andrea R.


    Dissolution and oxidation of sulfide minerals play key roles in both acid and metalliferous rock drainage and supergene enrichment. Surface speciation heterogeneity, critical to understanding mechanisms of mineral sulfide dissolution, has to date largely not been considered. To this end synchrotron scanning photoelectron microscopy (SPEM) was employed to examine freshly fractured and partially dissolved chalcopyrite (CuFeS2) surfaces (pH 1.0 HClO4 solution, redox potential 650 mV relative to a standard hydrogen electrode, 75 °C). S2- (bulk), S22- and Sn2- were found to be present on all samples at varying concentrations. Oxidation was observed to take place heterogeneously at the sub-micron scale. As compared to chalcopyrite partially dissolved for 5 days, extended dissolution to 10 days did not show appreciably enhanced oxidation of surface species; however surface roughness increased markedly due to the growth/overlap of oxidised sulfur species. On addition of 4 mM iron both S0 and SO42- were observed but not SO32-, indicating that the greater Fe3+ activity/concentration promotes heterogeneous sulfur oxidation. On contact of pyrite (FeS2) with chalcopyrite, significantly greater chalcopyrite surface oxidation was observed than for the other systems examined, with S0, SO32- and SO42- being identified heterogeneously across the surface. It is proposed that chalcopyrite oxidative dissolution is enhanced by increasing its cathodic area, e.g. contacting with pyrite, while increased Fe3+ activity/concentration also contributes to increased dissolution rates. The high degree of surface heterogeneity of these surface products indicates that these surfaces are not passivated by their formation. These results suggest that chalcopyrite dissolution will be accelerated when in contact with pyrite at solution redox potential intermediate between the rest potentials of chalcopyrite and pyrite (560 mV and 660 mV, respectively) and/or iron rich acidic waters with resulting

  8. Study of magnetic properties of nano-powders prepared by pyrite -> troilite transformation via high energy milling

    DEFF Research Database (Denmark)

    Balaz, P.; Alacova, A.; Godocikova, E.;


    the formation of troilite FeS together with residual Fe metal after relatively short milling times. The kinetic studies performed by Mossbauer spectrometry and VSM magnetometry enabled us to follow the progress of nanocrystalline magnetic phase formation in more details. It was shown that the pyrite......The preparation of nanocrystalline troilite by high-energy milling of FeS2 sulphide with elemental Fe acting as reducing element is reported. X-ray difractometry was used in order to determine the presence of different phases in investigated samples. This technique allowed us to identify......-->troilite transformation is almost finished already after 25 minutes of high-energy milling....

  9. Soil pollution by oxidation of tailings from toxic spill of a pyrite mine

    Energy Technology Data Exchange (ETDEWEB)

    Simon, M.; Martin, F.; Ortiz, I.; Garcia, I.; Fernandez, J.; Fernandez, E.; Dorronsoro, C.; Aguilar, J. [Dpto. de Edafologia y Quimica Agricola, Facultad de Ciencias, Universidad de Granada, 18071 Granada (Spain)


    On the 25th April 1998, toxic water and tailings from a pyrite mine of Aznalcollar (southern Spain) spilled into the Agrio and Guadiamar River Basin affecting some 40 km{sup 2}. In five sectors throughout the basin, we monitored the physical and chemical properties of the tailings as well as the degree of pollution in the soils on four different sampling dates: 5 May, 20 May, 4 June and 22 July 1998. The characteristics of the tailings deposited on the soils are shown to be related to distance from the spill. The oxidation rate of the tailings and the solubilization of the pollutant elements were more pronounced in the middle and lower sectors of the basin, where the particle size was finer, the sulfur content higher and the bulk density less. The increases in water-soluble sulfates, Zn, Cd and Cu were very rapid (the highest values being reached 25 days after the spill) and intense (reaching 45% of the total Cu, 65% of the total Zn and Cd). Meanwhile, the increases in water-soluble As, Bi, Sb, Pb and Tl were far lower (ranging between 0.002% of the total Tl and 2.5% of the total As) and less rapid in the case of As, Bi and Pb (the highest values for these elements being reached 40 days after the spill). These soluble elements infiltrated the soils with the rainwater, swiftly augmenting the soil pollution. Twenty-five days after the spill, when the rainfall ranged between 45 and 63 mm, the first 10-cm of the soils in the middle and lower sectors of the basin exceeded the maximum concentration permitted for agricultural soils in Zn, Cu and Tl. At 40 days after the spill, when the rainfall ranged between 60 and 89 mm, all the soils reached or exceeded the maximum permitted concentrations for As and Tl. Nevertheless, the pollutants tended to concentrate in the first 10 cm of the soils without seriously contaminating either the subsoil or the groundwaters. Consequently, a rapid removal of the tailings and the ploughing of the first 25-30 cm of the soils would be urgent

  10. First-principles investigation of the electronic states at perovskite and pyrite hetero-interfaces

    KAUST Repository

    Nazir, Safdar


    Oxide heterostructures are attracting huge interest in recent years due to the special functionalities of quasi two-dimensional quantum gases. In this thesis, the electronic states at the interface between perovskite oxides and pyrite compounds have been studied by first-principles calculations based on density functional theory. Optimization of the atomic positions are taken into account, which is considered very important at interfaces, as observed in the case of LaAlO3/SrTiO3. The creation of metallic states at the interfaces thus is explained in terms of charge transfer between the transition metal and oxygen atoms near the interface. It is observed that with typical thicknesses of at least 10-12 °A the gases still extend considerably in the third dimension, which essentially determines the magnitude of quantum mechanical effects. To overcome this problem, we propose incorporation of highly electronegative cations (such as Ag) in the oxides. A fundamental interest is also the thermodynamic stability of the interfaces due to the possibility of atomic intermixing in the interface region. Therefore, different cation intermixed configurations are taken into account for the interfaces aiming at the energetically stable state. The effect of O vacancies is also discussed for both polar and non-polar heterostructures. The interface metallicity is enhanced for the polar system with the creation of O vacancies, while the clean interface at the non-polar heterostructure exhibits an insulating state and becomes metallic in presence of O vacancy. The O vacancy formation energies are calculated and explained in terms of the increasing electronegativity and effective volume of A the side cation. Along with these, the electronic and magnetic properties of an interface between the ferromagnetic metal CoS2 and the non-magnetic semiconductor FeS2 is investigated. We find that this contact shows a metallic character. The CoS2 stays quasi half metallic at the interface, while the

  11. Simulation of pyrite oxidation in fresh mine tailings under near-neutral conditions. (United States)

    Alakangas, Lena; Lundberg, Angela; Nason, Peter


    Sulphidic residual products from ore processing may produce acid rock drainage, when exposed to oxygen and water. Predictions of the magnitude of ARD and sulphide oxidation rates are of great importance in mine planning because they can be used to minimize or eliminate ARD and the associated economic and environmental costs. To address the lack of field data of sulphide oxidation rate in fresh sulphide-rich tailings under near-neutral conditions, determination and simulation of the rate was performed in pilot-scale at Kristineberg, northern Sweden. The quality of the drainage water was monitored, along with oxygen and carbon dioxide concentrations. The chemical composition of the solid tailings was also determined. The field data were compared to predictions from simulations of pyrite oxidation using a 1-D numerical model. The simulations' estimates of the amount of Fe and S released over a seven year period (52 kg and 178 kg, respectively) were in reasonably good agreement with those obtained by analysing the tailings (34 kg and 155 kg, respectively). The discrepancy is probably due to the formation of secondary precipitates such as iron hydroxides and gypsum; which are not accounted for in the model. The observed mass transport of Fe and S (0.05 and 1.0 kg per year, respectively) was much lower than expected on the basis of the simulations and the core data. Neutralization reactions involving carbonates in the tailings result in a near-neutral pH at all depths except at the oxidation front (pH < 5), indicating that the dissolution of carbonates was too slow for the acid to be neutralized, which instead neutralized deeper down in the tailings. This was also indicated by the reduced abundance of solid Ca at greater depths and the high levels of carbon dioxide both of which are consistent with the dissolution of carbonates. It could be concluded that the near-neutral pH in the tailings has no decreasing effect on the rate of sulphide oxidation, but does reduce the

  12. An experimental study on the geochemical behavior of highly siderophile elements (HSE) and metalloids (As, Se, Sb, Te, Bi) in a mss-iss-pyrite system at 650 °C: A possible magmatic origin for Co-HSE-bearing pyrite and the role of metalloid-rich phases in the fractionation of HSE (United States)

    Cafagna, Fabio; Jugo, Pedro J.


    Pyrite, the most abundant sulfide in the Earth's crust, is an accessory mineral in several magmatic sulfide deposits. Although most pyrite is hydrothermal, previous experimental studies have shown that pyrite can also have a primary magmatic origin, by exsolving from monosulfide solid solution (mss) during cooling of a sulfide melt, if sulfur fugacity is sufficiently high. Pyrite from some localities has significant amounts of Co, and complex zonation in some low-melting-point chalcophile elements (LMCE), such as As, Se, Sb, Te, Bi (henceforth referred to as metalloids) and some platinum-group elements (PGE: Ru, Rh, Pd, Os, Ir, Pt). However, the origin of such pyrite and the causes of zonation are not clear. Because the distribution of some of these elements is heterogeneous and seems to be developed in concentric zones, the zonation has been interpreted to represent growth stages, some of them secondary and caused partly by hydrothermal fluids. Better constraints on the origin of Co-PGE-bearing pyrite could help unravel the geochemical processes affecting the sulfide assemblages in which it is found; thus, an experimental study was undertaken to characterize pyrite formation in magmatic sulfide environments and its relationship with metalloids and highly siderophile elements (HSE: PGE, Re, Au). Natural pyrrhotite, chalcopyrite, pentlandite and elemental S were mixed and doped with approximately 50 ppm of each HSE. A mixture of metalloids was added at 0.2 wt.% or 3 wt.% to aliquots of sulfide mixtures. Starting materials were sealed in evacuated silica tubes and fused at 1200 °C. The temperature was subsequently reduced to 750 °C (at 60 °C/h), then to 650 °C (at 0.5 °C/h) to produce relatively large euhedral pyrite crystals, then quenched. The experiments were analyzed using reflected light, SEM, EPMA and LA-ICP-MS. Experimental products contained euhedral pyrite, mss, intermediate solid solution (iss) and metalloid-rich phases, interpreted as quench product

  13. X-ray absorption near the edge structure and x-ray photoelectron spectroscopy studies on pyrite prepared by thermally sulfurizing iron films

    Institute of Scientific and Technical Information of China (English)

    Zhang Hui; Liu Ying-Shu; Wang Bao-Yi; Wei Long; Kui Re-Xi; Qian Hai-Jie


    This paper reports how pyrite films were prepared by thermal sulfurization of magnetron sputtered iron films and characterized by x-ray absorption near edge structure spectra and x-ray photoelectron spectroscopy on a 4B9B beam line at the Beijing Synchrotron Radiation Facility. The band gap of the pyrite agrees well with the optical band gap obtained by a spectrophotometer. The octahedral symmetry of pyrite leads to the splitting of the d orbit into t2g and eg levels. The high spin and low spin states were analysed through the difference of electron exchange interaction and the orbital crystal field. Only when the crystal field splitting is higher than 1.5 eV, the two weak peaks above the white lines can appear, and this was approved by experiments in the present work.

  14. Isolation and characterization of a novel Acidithiobacillus ferrivorans strain from the Chilean Altiplano: attachment and biofilm formation on pyrite at low temperature. (United States)

    Barahona, Sergio; Dorador, Cristina; Zhang, Ruiyong; Aguilar, Pablo; Sand, Wolfgang; Vera, Mario; Remonsellez, Francisco


    Microorganisms are used to aid the extraction of valuable metals from low-grade sulfide ores in mines worldwide, but relatively little is known about this process in cold environments. This study comprises a preliminary analysis of the bacterial diversity of the polyextremophilic acid River Aroma located in the Chilean Altiplano, and revealed that Betaproteobacteria was the most dominant bacterial group (Gallionella-like and Thiobacillus-like). Taxa characteristic of leaching environments, such Acidithiobacillus and Leptospirillum, were detected at low abundances. Also, bacteria not associated with extremely acidic, metal-rich environments were found. After enrichment in iron- and sulfur-oxidizing media, we isolated and identified a novel psychrotolerant Acidithiobacillus ferrivorans strain ACH. This strain can grow using ferrous iron, sulfur, thiosulfate, tetrathionate and pyrite, as energy sources. Optimal growth was observed in the presence of pyrite, where cultures reached a cell number of 6.5 · 10(7) cells mL(-1). Planktonic cells grown with pyrite showed the presence of extracellular polymeric substances (10 °C and 28 °C), and a high density of cells attached to pyrite grains were observed at 10 °C by electron microscopy. The attachment of cells to pyrite coupons and the presence of capsular polysaccharides were visualized by using epifluorescence microscopy, through nucleic acid and lectin staining with Syto(®)9 and TRITC-Con A, respectively. Interestingly, we observed high cell adhesion including the formation of microcolonies within 21 days of incubation at 4 °C, which was correlated with a clear induction of capsular polysaccharides production. Our data suggests that attachment to pyrite is not temperature-dependent in At. ferrivorans ACH. The results of this study highlight the potential of this novel psychrotolerant strain in oxidation and attachment to minerals under low-temperature conditions.

  15. Effect of capping ligands on the optical properties and electronic energies of iron pyrite FeS{sub 2} nanocrystals and solid thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhai, Guangmei, E-mail: [Key Laboratory of Interface Science and Engineering in Advanced Materials of Ministry of Education of the People' s Republic of China, Research Centre of Advanced Materials Science and Technology of Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China); Jiangsu Key Laboratory for Solar Cell Materials and Technology, Changzhou University, Changzhou, Jiangsu 213164 (China); State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054 (China); Xie, Rongwei; Wang, Heng; Zhang, Jitao; Yang, Yongzhen; Wang, Hua; Li, Xuemin [Key Laboratory of Interface Science and Engineering in Advanced Materials of Ministry of Education of the People' s Republic of China, Research Centre of Advanced Materials Science and Technology of Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China); Liu, Xuguang [Key Laboratory of Interface Science and Engineering in Advanced Materials of Ministry of Education of the People' s Republic of China, Research Centre of Advanced Materials Science and Technology of Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China); College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China); Xu, Bingshe [Key Laboratory of Interface Science and Engineering in Advanced Materials of Ministry of Education of the People' s Republic of China, Research Centre of Advanced Materials Science and Technology of Taiyuan University of Technology, Taiyuan, Shanxi 030024 (China)


    In this work, the optical and electronic properties of iron pyrite FeS{sub 2} nanocrystals and solid thin films with various capping ligands were systematically investigated by UV–Vis–NIR absorption spectroscopy, cyclic voltammetry and current density–voltage characteristic measurements. The iron pyrite nanocrystals with various ligands have an indirect band gap of around 1.05 eV and broad absorption spanning into the near-infrared region, exhibiting favorable optical properties for their photovoltaic applications. The electron affinities and ionization potentials of FeS{sub 2} nanocrystals determined through cyclic voltammetry measurements show strong ligand dependence. An energy level shift of up to 190 meV was obtained among the pyrite nanocrystals capped with the ligands employed in this work. The iron pyrite nanocrystal films capped with iodide and 1,2-ethanedithiol exhibit the largest band edge energy shift and conductivity, respectively. Our results not only provide several useful optical and electronic parameters of pyrite nanocrystals for their further use in optoelectronic devices as active layers and/or infrared optical absorption materials, but also highlight the relationship between their surface chemistry and electronic energies. - Highlights: • The energy levels of FeS{sub 2} nanocrystals with various ligands were determined via electrochemical measurements. • The energy levels of FeS{sub 2} nanocrystals showed strong ligand-dependence. • An energy level shift of up to 190 meV was obtained for the pyrite nanocrystals studied in the work. • The conductivities of FeS{sub 2} nanocrystals with different ligands were obtained by current density–voltage measurements.

  16. Assisted phytoremediation of mixed metal(loid)-polluted pyrite waste: effects of foliar and substrate IBA application on fodder radish. (United States)

    Vamerali, Teofilo; Bandiera, Marianna; Hartley, William; Carletti, Paolo; Mosca, Giuliano


    Exogenous application of plant-growth promoting substances may potentially improve phytoremediation of metal-polluted substrates by increasing shoot and root growth. In a pot-based study, fodder radish (Raphanus sativus L. var. oleiformis Pers.) was grown in As-Zn-Cu-Co-Pb-contaminated pyrite waste, and treated with indolebutyric acid (IBA) either by foliar spraying (10 mgL(-1)), or by direct application of IBA to the substrate (0.1 and 1 mgkg(-1)) in association, or not, with foliar spraying. With the exception of foliar spraying, IBA reduced above-ground biomass, whilst direct application of IBA to the substrate surface reduced root biomass (-59%). Trace element concentrations were generally increased, but removals (mg per plant) greatly reduced with IBA application, together with greater metal leaching from the substrate. It is concluded that, in our case, IBA had a negative effect on plant growth and phytoextraction of trace elements, possibly due to unsuitable root indoleacetic acid concentration followi