Goldschmidt 2012 Conference Abstracts North American ice sheet dynamics A strain-heating model for the seismic controlled by obliquity (41 ka) during low-velocity zone along the Main the early Pleistocene Himalaya Thrust
1,2* 1 3 2,4 1* 2 B.D.A. NAAFS , J. HEFTER , G. ACTON , G.H. HAUG , A. PETER I. NABELEK AND JOHN L. NABELEK 2,4 5 1 MARTÍNEZ-GARCIA , R. PANCOST , AND R. STEIN 1 Dept. of Geological Sciences, University of Missouri, Columbia, 1Alfred Wegener Institute for Polar and Marine Research, MO 65211, USA, [email protected] (* presenting author) Department of Marine Geology and Paleontology, D-27568 2 College of Oceanic and Atmospheric Sciences, Oregon State Bremerhaven, Germany, [email protected] (* Presenting University, Corvallis, OR 97331, USA, [email protected] author) 2Leibniz Center for Earth Surface and Climate Studies, Institute for Seismic low-velocity zone along the MHT Geosciences, Potsdam University, D-14476 Potsdam, Germany Recent Hi-CLIMB seismic experiment, using an 800 km long, 3Department of Geology, University of California, CA 95616 Davis, densely spaced seismic array across Nepal and southern Tibet, has USA revealed a narrow low-velocity zone along the Main Himalaya Thrust 4Geological Institute, ETH Zürich, 8092 Zürich, Switzerland [1]. The zone extends approximately from the 28.5°N latitude, 5Organic Geochemistry Unit, Bristol Biogeochemistry Research dipping to ~40 km depth at the latitude of the Yarlung Tsangpo Centre, School of Chemistry, University of Bristol, BS8 1TS Suture (YTS), and then continues horizontally beneath the Lhasa Bristol, United Kingdom Block to approximately 32°N latitude. Nabelek et al. [1] interpreted this deep low-velocity zone to be the result of increased ductility During the Pleistocene, large continental ice sheets and partial melting. The narrowness of the low-velocity zone along episodically apperead in the Northern Hemisphere, covering large most of the length of the MHT requires a mechanism by which the parts of Europe and North America. Besides the results based on partial melting is localized. Strain heating along the ductile portion benthic oxygen isotope records, which predominantly represent of the MHT provides such a mechanism. variations in global ice volume, little is know about the timing of and astronomical control on the advances and retreats of the continental Parameters of numerical model ice sheets in the Northern Hemisphere during the late Pliocene and Development of the partially molten zone was modeled early Pleistocene (3-2 million years (Ma) ago). numericaly following [2]. The model domain is 600x140, 1 km grid. Here we therefore present the first orbitally-resolved records The initial conditions are steady-state with subduction of the Indian of terrestrial higher plant leaf wax input to the North Atlantic lithosphere beneath the Himalayas and Tibet at 3 cm/y. Temperature covering the last 3.5 Ma, based on the accumulation of long-chain n- is 25°C at the surface and 1300°C at the bottom of the lithosphere. alkanes and n-alkanl-1-ols at IODP Site U1313 [1]. These lipids are Radiogenic heat production (Ah) in the Indian crust was constrained 2 a major component of dust, even in remote ocean areas, and have a by the average 70 mW/m surface heat flux of the stable northern 3 predominantly aeolian origin in distal marine sediments. Our results Indian crust. Ah in the upper plate was assumed to be 2 μW/m 3 demonstrate that around 2.7 Ma, coinciding with the intensification throughout and in the mantle 0.01 μW/m . Subduction of the Indian of the Northern Hemisphere glaciation (NHG), the aeolian input of lithosphere at 3 cm/y keeps the crust above the MHT refrigerated. terrestrial material to the North Atlantic increased drastically. Since The model accounts for temperature-dependent thermal diffusivity then, during every glacial the aeolian input of higher plant material [2, 3] and power-law temperature dependence of the shear strength was up to 30 times higher than during interglacials. We argue that (τ) of quartz [4]. Strain heating in the ductile regime is given by τ·ε, the increased aeolian input at Site U1313 during glacials is where ε is the strain rate. Strain rate in a 3 km wide shear zone is -13 –1 3 predominantly related to the episodic appearance of continental ice 3·10 s . Heat production at this strain rate is ~100 μW/m at 3 sheets in North America and the associated strengthening of 550°C and ~10 μW/m at 750°C [2]. glaciogenic dust sources. The records thus reflect the timing of the advances and retreats of the North American ice sheets. Evolutional Model results spectral analyses of the n-alkane records were therefore used to Strain heating was assumed to occur along the length of the determine the dominant astronomical forcing in North American ice MHT, but only within the ductile regime. With subduction only, sheet advances over the last 3.5 Ma. These results demonstrate that shearing produces a narrow, partially molten zone that extends from during the early Pleistocene North American ice sheet dynamics below the Himalayas to the northern end of the model domain. The responded predominantly to variations in obliquity (41 ka), which partially molten zone is underlain by an inverted temperature argues against previous suggestions of precession-related variations gradient. The ductile regime extends further to the south along the in Northern Hemisphere ice sheets during the early Pleistocene [2]. MHT, in accord with observations [1]. Thus, the calculations demonstrate the feasibility of producing the observed low-velocity, [1] Naafs et al. (2012) Earth Plan. Sci. Lett. 317-318, 8-9. [2] partially-molten zone along the MHT in the deep crust. Raymo et al. (2006) Science 313, 492-495 [1] Nabelek, J.L. et al. (2009) Science 325, 1371-1374. [2] Nabelek, P.I. et al. (2010) J Geophys Res 115, B12417. [3] Whittington et al. (2009) Nature 458, 319–321. [4] Rutter, E.H. & Brodie, K.H. (2004) J Struct Geol. 26, 2011– 2023.
Mineralogical Magazine | www.minersoc.org 2151 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts
Depleted Mantle as the Source of SO2 emissions and their role in Gold in Archean Alkaline Magmatic- eruptive activity at Fuego Volcano, Hydrothermal Systems Guatemala
1* 1 1 OLIVIER NADEAU , ROSS STEVENSON , MICHEL JÉBRAK 1, 2* 1 PATRICIA A. NADEAU , GREGORY P.WAITE , AND JOSÉ L. 1 1, 3 UQAM-Géotop, Département des Sciences de la Terre et de PALMA
l’Atmosphère , [email protected] (* presenting author) 1 Michigan Technological University, Department of Geological and
Field relations, trace element and isotopic compositions and isotope Mining Engineering and Sciences, Houghton, MI, USA, dating suggest that 2.6 to 2.7 Ga. old gold-bearing syenites, [email protected] (*presenting author) lamprophyres (sensu stricto) and carbonatites of the Abitibi 2Now at: American Museum of Natural History, Department of greenstone belt are genetically related. Their chondrite-normalized Earth and Planetary Science, New York, NY, USA REE signatures are very similar and a survey of isotope data in the 3 87 86 Now at: Center for Geohazards Studies, University at Buffalo, literature reveals εNd and Sr/ Sr values that are consistent with a depleted mantle source. Preliminary results from syenites and Buffalo, NY, USA lamprophyres of the Duquesne gold mine indicate that they have similar REE patterns in addition to both mantle and crustal isotopic Magmatic volatiles have an important role in many aspects of compositions. volcanism, from magma generation to initiation of seismic phenomena to influence on eruption style. It follows that many models of volcanism and volcanogenic phenomena rely on behavior of such volatiles. UV cameras offer enhanced temporal resolution
over previous SO2 emission rate measurement techniques and also offer a synoptic view of plumes and degassing behavior. Integrated UV camera and seismic measurements recorded in January 2008 and January 2009 at Fuego volcano, Guatemala, provide new insight into the system’s shallow conduit processes. In 2008, an inter-explosion period was marked by pseudo-cyclic
patterns of SO2 emission rate. Comparison of the data with band- pass-filtered seismic data indicates that the onsets of increases in
SO2 emission rate are accompanied by very long period (VLP) seismic events. Larger amplitude VLPs are associated with larger
pulses of SO2 and shorter preceding inter-event times. Other VLPs associated with explosions at Fuego have been linked to pressurization at the intersection of two cracks [1], but the non- Figure 1: ɛNd values for 2.6 to 2.7 Ga. lamprophyres, syenites and explosive nature of these VLPs may indicate a different source carbonatites of the Abitibi greenstone belt. The three lithologies process. display similar, mantle values, although the lamprophyres show UV camera data in 2009 reveal patterns of SO emission rate some crustal alteration. 2 relative to explosions and low-frequency seismic tremor that These results allow us to shed light on the petrogenesis of these indicate tremor and degassing share a common source process. rocks and their relationship to the gold deposits. Lamprophyres are Progressive decreases in emission rate appear to represent quenched, volatile-rich, mafic porphyric rocks that interact very inhibition of gas loss from magma as a result of rheological little with the crust as they rise from the mantle. Syenites also stiffening in the upper conduit. Measurements of emission rate from appear to be derived from a depleted mantle source that has two closely-spaced vents, made possible by 2-dimension nature of interacted very little with the crust during their evolution. We camera data, help constrain this model. propose that the syenites were produced by fractional crystallization of lamprophyre magmas in the crust. In this model, gold could have Eruptive activity at Fuego appeared superficially similar in been carried from the mantle to its site of deposition in shallow January 2008 and 2009, with a passive gas plume and sporadic, ash- level syenitic porphyries via a mantle-derived, carbothermal fluid. rich explosions. Gas emission data obtained via UV camera, in This model also finds support in the coexistence of carbonic-fluid- combination with seismic data, enabled elucidation of different saturated, hybrid silicocarbonatites of Abitibi and most late-Archean eruptive processes driven by the movement and escape of volatiles. gold deposits. [1] Lyons and Waite (2011) Journal of Geophysical Research 116, B09303.
Mineralogical Magazine | www.minersoc.org 2152 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Alteration and isotopic vectoring at Magnetite - An indicator mineral for the syenite-hosted Young-Davidson hydrothermal ore deposits PATRICK NADOLL1*, JEFFREY L. MAUK2, RICHARD LEVEILLE3, gold deposit, Matachewan, Ontario 1 1 LOUISE FISHER , ROBERT HOUGH 1* 2 1 3 2 N. NADERI , R. MARTIN , R. LINNEN , J. ZHANG , S. LIN 1CSIRO, 26 Dick Perry Ave, Kensington, 6151 Perth, WA, Australia 1 AND N.R. BANERJEE 2University of Auckland, New Zealand 3 1University of Western Ontario, Department of Earth Sciences, Freeport McMoRan, Phoenix, United States London, Ontario, Canada, [email protected] (*presenting author) 2 Magnetite and other Fe-Ti –oxides have been recognized as University of Waterloo, Earth and Environmental Sciences, potential indicator minerals for exploration purposes since the 1980s. Waterloo, Canada 3 However, only recent studies have presented data that illustrate University of Hong Kong, Earth Sciences, Hong Kong, China characteristic variations among magnetites of hydrothermal origin The Young Davidson mine is a syenite-hosted orogenic gold and describe distinct compositional signatures that can discriminate deposit at the western end of the Cadillac-Larder-Lake deformation specific geologic settings such as hydrothermal ore deposits. The zone in the southern Abitibi greenstone belt, Canada. The earliest major controls for the geochemistry of hydrothermal magnetite are lithology/fluid composition, T, fO /fS and re-equilibration processes. stage of veining (V1) consists of folded and boudinaged quartz- 2 2 Exploratory data analysis has established the following upper ankerite veins. V2 is comprised of folded quartz-pyrite veinlets and threshold concentrations for hydrothermal magnetite from Ag-Pb-Zn disseminated sulphides and V3 consists of en echelon or planar quartz-carbonate veins with sulphide minerals. The major phase of veins, porphyry Cu-Mo, and skarn deposits (Table 1). The most important overall discriminators for the minor and trace element Au mineralization is associated with V2 veins. Gold occurs as geochemistry of hydrothermal magnetite are Mg, Al, Ti, V, Co, Mn, inclusions in V2 pyrite, along quartz-carbonate grain boundaries in Zn, and Ga. Nickel and Cr, which can have significant concentrations V3 veins and as inclusions in disseminated pyrite in zones of intense potassic-hematite alteration. in igneous magnetite, are not commonly present at levels above their Contouring of whole rock drillcore data indicate that Au is respective detection limits. Hydrothermal magnetite is typically depleted in Ti compared to igneous magnetite. Aluminum and V correlated with K2O, S and Ba, consistent with the result of core logging, which established an association of Au with intense display a similar trend although the overlap between hydrothermal potassic-hematite alteration, quartz veining, pyritization and and igneous magnetite is more pronounced for these elements. Depleted Ti and V concentrations in combination with enriched Mg decreased magnetic susceptibility. Increases of K2O (2 to 9 wt%) and Ba (600 to 3800 ppm) and a decrease of whole rock δ18O values contents up to wt% values are in particular characteristic for (11.4 to 9.2 ‰) is observed for some of the mineralized zones. Thus hydrothermal magnetite from magnesian skarn. Manganese potassic alteration and whole rock δ18O contours show promise as concentrations vary significantly among hydrothermal and igneous vectors to Au mineralization likely associated with high temperature magnetites but concentrations are commonly lesser in hydrothermal magmatic fluids. magnetite with values up to several 1000 ppm. Cobalt, Zn, and Ga are Bulk rock XRD analysis supports the idea of different alteration enriched in hydrothermal magnetite from skarn compared to other zones extending from shallower to deeper parts of the deposit. In hydrothermal magnetite. In addition to minor and trace element shallower parts, ankerite abundance increases and that of calcite concentrations, the occurrence, abundance and composition of decreases towards the zone of mineralization. In deeper parts, this inclusions in magnetite is a potential tool to discriminate magnetite distribution pattern is reversed. In terms of oxide minerals, shallow sample populations and fingerprint mineral deposits. Minor and trace mineralization is dominated by hematite (the concentrations of elements that are commonly associated with micro- or nano- rutile and barite are also high enough to be identified in XRD inclusions in magnetite include Ca + REEs (apatite and carbonates), patterns). In the deeper zones of mineralization hematite abundance Si (silicates), Cu (Cu-sulfides), Nb (rutile). Copper can be decreases and magnetite abundance increases towards the particularly indicative for mineralized zones where magnetite is mineralized zones. closely associated with Cu-sulfides such as chalcopyrite or chalcocite. Temperatures calculated from mineral pair oxygen isotope Tabl e 1: Upper threshold concentrations in ppm for n-number of thermometry indicate the fluids ranged from approximately 330° to hydrothermal magnetites from a range of geological settings. 460°C.Calculated V3 vein fluid compositions range from 6.4 to 11.9 ‰ and V1 from 6.6 to 7.4 ‰. In the deeper zones Au Ag-Pb-Zn Porphyry Mg-skarn Skarn mineralization is correlated to high K2O alteration, high sulphur n 30 126 17 57 18 concentrations and low δ O values, which indicate magmatic fluid Mg 740 490 25810 8780 involvement. However, in shallower zones gold mineralization is Al 900 3180 2730 11330 consistent with high δ18O values, which is interpreted that the fluids were at lower temperatures and/or dominated by metamorphic fluids Ti 4160 10500 20 8820 reflecting a separate and possibly later mineralizing event. We V 170 1460 20 14190 conclude that there are multiple stages of Au mineralization at Co 10 40 5 320 18 Young-Davidson and that δ O whole rock values, potassic alteration Mn 1220 1880 1600 2900 and sulphur concentrations can be used as vectors for mineralization Zn 110 280 260 5470 within different alteration zones. Ga 10 60 30 600
Mineralogical Magazine | www.minersoc.org 2153 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Hf isotope evidence for a transition in Oxygen isotopic exchange reaction the geodynamics of continental growth between silicate melt and ambient gas 1 2 after 3.2 Ga HIROKO NAGAHARA * AND KAZUHITO OZAWA
T. NÆRAA1,2, A. SCHERSTÉN3, M.T. ROSING2, A.I.S. KEMP4, J.E. 1The University of Tokyo, Department of Earth and Planetary HOFFMANN5,6, T.F. KOKFELT1, M. WHITEHOUSE7. Science, Tokyo, Japan, [email protected] (* presenting author) 1Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 2 The University of Tokyo, Department of Earth and Planetary 10, 1350 København K, Denmark Science, Tokyo, Japan, [email protected] 2) Nordic Center for Early Earth Evolution, Copenhagen University, Øster
Voldgade 3-5, 1350 København K., Denmark Oxygen Isotopic Variation of Planetary Materials 3) Department of Geology, Lund University, Sölvegatan 12, 223 62 Lund, Chondrite, nonchondritic meteorites, and planets show wide Sweden variations of oxygen isotopic compositions, which incude mass- 4) School of Earth and Environmental Sciences, James Cook University, dependent and mass-independent fractionations. Mass-independent Townsville 4811 Australia oxygen isotopic fractionation has been one of the most extensively 5) Steinmann Institut für Geologie, Mineralogie, Paläontologie. Rheinische studied subjects of meteorite study, whereas mass-dependent Wilhelms-Universität, Poppelsdorfer Schloss, 53115 Bonn, Germany isotopic fractionation has not been paid attentions. It is, however, 6) Geologisch-Mineralogisches Institut, Universität zu Köln, Zülpicher Str. contorlled by physics, and is potentially an excellent indicator for 49a, Köln, Germany environments. Here, we quantitatively study the role of isotopic exchange reaction between silicate melt and gas, and evaluate mixing 7) Swedish Museum of Natural History, Box 50007, SE-104 05 lines on the oxygen three isotope plot. Stockholm, Sweden Method We have developed a kinetic condensation model that assumes Earth’s lithosphere likely experienced an evolution toward the modern totally molten silicate melt sphere cooling from an above liquidus plate tectonic regime, due to secular changes in mantle temperature. temperature in a closed or open system, which has a composition of Gradually declining growth rates of the continental crust through time has the solar abundance except for hydrogen. The model includes three been suggested, and recent estimates suggest that ≥70% of the present free parameters; cooling rate of the system, initial oxygen continental crustal reservoir was extracted by the end of the Archaean [1]. abundance in gas relative to metallic elements, and oxygen isotpopic Patterns of crustal growth and reworking in rocks younger than 3.0 billion exchange efficiency. The model consists of the Hertz-Knudsen years (Ga) are thought to reflect the assembly and breakup of equation that describes condensation/evaporation flux and isotopic supercontinents by Wilson Cycle processes and mark an important change exchange reactions. in lithosphere dynamics. It has been argued that subduction settings and Results We found that isotopic exchange reactions play a critical role in crustal growth by arc accretion go back to 3.8 Ga in southern West evolution of condensing silicate melt: silicate melt gets highly Greenland [2-4]. We present in-situ zircon U/Pb, Hf and O isotope data mass-fractionated composition if isotopic exchange does not work, from basement rocks in southern West Greenland across the time-period which results in deviation of a straight mixing line but in formation where modern style tectonic regimes might have started. Our data show of a fractionation trend with a slope of 1/2 on a oxygen three isotope that pronounced differences in the εHf-time patterns occurred, implying plot. An isotopic exchange reaction greatly suppresses mass- changing source rock characteristics. The observations suggest that 3.9-3.5 dependent isotopic fractionation, which is tends to form a straight Ga rocks differentiated from a ≥3.9 Ga initially chondritic to slightly mixing line. The effect of fractionation is more conspicuous when depleted mafic proto-crust. In contrast, rocks formed after 3.2 Ga register the relative abundance of oxygen in the ambient gas against silicate the first additions of juvenile depleted material since 3.9 Ga. Crustal melt is small. The degree also depends on isotopic exchange growth after 3.2 Ga is characterised by upward εHf shifts and correlate in efficiency, but it is not dependent on cooling rate of the system. If the oxygen isotopic exchange efficiency does not change largely, age with regional meta-volcanic supracrustal belts, stabilised felsic crust the degree of deviation from a straight mixing line corresponds to are characterised by downward εHf excursions, a pattern that compare the melt/gas ratio in a planetary environment or dust/gas ratio in a with Phanerozoic accretionary orogens [5,6]. The isotope data reveal a protoplanetary disk environment. transition from a crustal evolutionary signature unlike that of modern Discussions subduction-related orogens that didn’t seem to generate or stabilise The calculation results show that the straight mixing lines juvenile zircon-bearing crust, to an isotope-time pattern after 3.2 Ga that is observed in various chondritic components such as CAIs and compatible with arc accretionary processes and plate tectonics. chondrules are explained by condensation in the presence of oxygen in the ambient gas by more than two orders of magnitude than the [1] Belousova et al., (2010) Lithos, 119, 457–466. [2] Komiya et al., J. metallic elements. Otherwise, the mixing lines should be curved Geol. 107, 515-554 [3] Nutman et al., (2009) Precam. Res. 172, 212–233 18O-rich side. The average O/M ratio (M: metallic [4] Furnes et al. (2007) Science 315, 1704-1707. [5] Kemp et al., (2009) elements) of the solar abundance is ~100, which suggests that CAIs Earth Planet. Sci. Let. 284, 455–466 [6] DeCelles et al., (2009) Nature and chondrules that show straight mixing lines were formed in an Geoscience 2, 251-257 oxygen enriched environment than the average solar abundance. The model is further applied to the Earth-moon system, where homogenization of oxygen isotopic composition is easy at the stage of magma ocean.
Mineralogical Magazine | www.minersoc.org 2154 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Separation of Mo, W and HFSEs Characterizing the cessation of arc- from rock samples for the study of normal mid-crust extrusion, NW isotope anomalies in meteorites Nepal Himalaya
1* 1 YUICHIRO NAGAI , TETSUYA YOKOYAMA AND RICHARD J. CARL NAGY 1*, LAURENT GODIN 1, JOHN COTTLE 2 AND BORJA 2 WALKER 1 ANTOLÍN 1 Dept. of Earth and Planetary Sciences, Tokyo Institute of 1 Queen’s University, Department of Geological Sciences and Technology, Tokyo, Japan. (* [email protected]) Geological Engineering, Kingston, Canada, 2 Dept. of Geology, Univ. of Maryland, College Park, MD, USA [email protected] (* presenting author)
2 University of California, Department of Earth Sciences, Santa Recent innovations in mass spectrometry have enabled Barbara, USA detection of small isotope anomalies in some heavy elements
present in a variety of meteorites. To make highly-precise and “accurate“ isotope analysis, chemical separation of the target The metamorphic and anatectic core of the Himalaya, the Greater element from various types of meteorites must be developed from Himalayan Sequence (GHS), has been hypothesized to represent the following standpoints: 1) Achieve of nearly 100% recovery to exhumed mid-crustal material via a channel flow model [1 and avoid mass fractionation during chemical separation. 2) Complete references therein]. Characterizing the cessation of this lateral mid- removal of unwanted elements that can interfere with isotope crustal extrusion is integral in providing a comprehensive analysis. 3) Maintain high sample/blank ratios. 4) Simultaneously understanding of mid-crustal flow during orogenesis. separate as many elements as possible from a single sample. The last Field mapping, structural and microstructural analysis, point is important not only to preserve precious meteorites, but also geochronology, and thermochronology confirm the existence of the for performing multi-elemental isotope analysis on heterogeneous Gurla-Mandhata-Humla fault, an orogen-oblique strike-slip dominated samples. In this study, we have developed a chemical separation fault in the High Himalaya of northwestern Nepal. Detailed across- method for Mo, W and HFSEs (High Field Strength Elements; e.g., strike transects reveal shallow-dipping mylonitic foliations and Zr, Hf) from meteorite samples, all of which are intriguing elements strongly-developed shallow plunging mineral stretching lineations for the study of isotope anomalies in the early solar system. We also interpreted to represent the terminal stages of arc-normal directed show our prelimiary analysis of Mo isotope compositions in bulk extrusion of mid-crustal material, and onset of orogenic extension [2]. chondrites and their acid leachates. Furthermore, late-stage deformation along this fault system overprints The separation method consists of a two-stage column the GHS and its upper bounding fault, thus confirming a cessation of chemistry using anion exchange resin (BioRad AG1X8). We have and transition from extruding GHS to subsequent arc-parallel evaluated the performance of our technique by using a synthesized deformation. A study of this fault system therefore provides multi-element solution and some terrestrial rock samples documentation of the final stages of arc-normal directed extrusion of decomposed by HF. A quadrupole-type ICP-MS (ThermoFisher X mid-crustal material. SERIES II at Tokyo Tech.) was used to determine the elution profile, The shear zone is characterized at upper structural levels by well- as well as the recovery yield of Mo during the column chemistry. developed type-1 cross-girdle quartz c-axis fabrics and symmetric a- Molybdenum isotopes were analyzed by N-TIMS (TRITON-plus at axis fabrics, indicating plane strain conditions. C-axis fabrics transition Tokyo Tech). to type-2 cross girdles at ~ 1.2 km below the fault, suggesting an In the first column, HFSE, W and Mo were successively eluted ostensible contribution of constrictional strain at depth. This deviation by 9M HCl-0.05M HF, 9M HCl-1M HF, and 6M HNO3-3M HF, towards constriction is consistent with measured quartz a-axes, which respectively. Unwanted elements in the Mo fraction (Zn, Nb and show a progression towards upright cleft girdle patterns at similar trace Ru) were further separated in the second column. The column depths. Quartz c-axis opening angles and quartz and feldspar size and total amount of acids were dramatically reduced compared recrystallization mechanisms show a progressive increase in to previous techniques. The Mo recovery was 94.5 ± 2.9 % in the deformation temperatures from ~ 350°C along the zone of maximum first column and 101.3 ± 5.0 % in the second column. By applying strain, to upwards of ~ 630°C at depths greater than ~ 5.5 km below this technique, we have determined Mo isotope compositions in bulk the fault. Abundant asymmetrical fabric elements and conjugate shear samples of Murchison (CM2) and Allende (CV3), as well as their bands in conjunction with a calculated mean kinematic vorticity acid leachates. The Mo isotope anomalies in bulk Murchison and a number of 0.60 (c. 58% pure shear) attest to an important contribution leachate indicate deficits of s-process Mo isotopes, consistent with of pure shear. U-Th-Pb in situ monazite geochronology, U-Pb zircon previous studies [1, 2]. In contrast, anomalies observed in bulk geochronology, and 40Ar/ 39Ar muscovite thermochronology reveal Allende and its leachates are enigmatic, which may require a crystallization, decompression melting, and cooling within ≤ 7 Myr. reassessment of the isotopic compositions of end-member These data indicate that the final stages of the extruding mid-crust components calculated by current nucleosynthetic theories. are characterized by a particularly high vertical gradient in deformation temperatures, deviations from plane strain at depths, and a significant [1] Burkhardt et al. (2011a) EPSL 312, 390-400. [2] Burkhardt et al. contribution of pure shear. Furthermore, chronological data suggest (2011b) LPSC 42, #2592. that cooling and cessation of arc-normal extrusion of the mid-crust occurred within a geologically confined period.
[1] Godin et al. (2006) Geol. Soc. Spec. Publ. 268, 1-23. [2] Murphy & Copeland (2005) Tectonics. 24. TC4012, doi:10.1029/2004TC001659.
Mineralogical Magazine | www.minersoc.org 2155 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Phase relations in meta-komatiites Transport of uranyl and arsenate in during dehydration melting the presence of SiO2, Al2O3, TiO2 and 1* 2 1 NAIR,R. CHACKO, T. VERWIMP, J. FeOOH
1* 1 1Department of Geoscience, University of Calgary, Canada T2K SREEJESH NAIR , BRODER J MERKEL 1N4(*[email protected]) 1 Department of Hydrogeology, Technische Universität 2Department of Earth and Atmospheric Sciences, University of Bergakademie Freiberg, Gustav-Zeuner Str.12, 09599 Alberta, Canada T6G 2E3 Freiberg, Germany
[email protected] (* presenting author) Komatiitic-basalts and komatiites are relatively abundant in the [email protected] volcanic record of Archean cratons compared to Phanerozoic
terranes. It has been suggested that these rocks may have Uranium is a naturally occurring radioactive and chemically constituted the Archean oceanic crust. It is important to understand toxic metal, which is widespread in nature. Reactive transport of the role these rocks would have played in the transformation of U(VI) with various ligands and different minerals has been studied oceanic crust during purported processes like slab melting, eclogite extensively. Arsenic is analogous to phosphate and is a well-known formation etc. Whereas metamorphic phase relations of mid-ocean contaminant to the environment. Uranyl-arsenate complex formation ridge (MORB) type basalts have been widely studied in the past, at near-neutral to alkaline pH conditions was proved by XAS and there is a paucity of knowledge on the phase relations of komatiitic – XANES [1]. They reported the formation of UO2AsO4 , analogous to basalts and komatiites. – UO2PO4 . However, little information is available about the We report results of preliminary dehydration melting migration of U(VI) and As(V) in systems containing both elements. experiments (1000°C, 7-20 kbar) on a natural amphibolite of The changes in sorption behaviour of U(VI) and As(V) in columns komatiitic composition with starting composition in wt.% oxides : containing bentonite [2] and iron-coated sand [3] were reported. SiO 48.26, TiO 0.50, Al O 7.19, Fe O 13.31, MnO 0.23, MgO 2 2 2 3 2 3 Since As(V) co-exists with U(VI) in several mining areas, it is 18.66, CaO 8.49, Na O 0.51, K O 0.05 (1). The experiments were 2 2 important to understand the species behaviour to implement proper conducted on a piston cylinder apparatus for a duration of 2-7 days remediation procedures. Less or no information is available about using procedures outlined in (2). the transportation of U(VI) and As(V) in the presence of SiO2,
Al 2O3, TiO2 and FeOOH, which are very common in natural Experiment P (kbar) T ( oC) Phases Present environments. Hence column experiments were carried out for 7IG006 7 1000 Ol,Cpx, (Opx), Melt uranium (0.5 μM/L), arsenate (0.5 μM/L) and both uranium and 7IG005 10 1000 Ol,Cpx, Opx, Melt arsenic containing solutions (0.5:0.5 μM/L) with SiO2 (10 g), Al2O3 7IG004 12.5 1000 Ol,Cpx, Opx, Melt (10 g), TiO2 (0.5 g) and FeOOH (0.1 g) at pH 6.5. Transport 7IG001 15 1000 Grt, Cpx, Opx, Melt,(Amph) behaviour of U(VI) and As(V) through SiO2 packed columns are 7IG003 15 1000 Grt, Cpx, Opx, Melt,[Amph] identical for solutions containing either U(VI) or As(V) separately, 7IG002 17.5 1000 Grt, Cpx, Opx, Melt or both together. Almost identical transport behaviour was observed
7IG007 20 1000 Grt, Cpx, Opx, Melt for TiO2 column also. In the presence of equimolar U(VI) and As(V) Tabl e 1: Experimental conditions and phase relations. Abbreviations a substantial increase in As(V) mobility and slight decrease in U(VI)
after (3). (), [] indicate minor and trace proportions, respectively. migration through Al2O3 was observed. When Al2O3 is replaced by Phase relations (Table 1) indicate a melt residue dominated by FeOOH, a significant change in the pattern of mobility was shown ol, opx and cpx at P <15 kbar and grt, opx and cpx at P ≥ 15 kbar. for As(V) and minor changes for U(VI). The changes in transport The incoming of garnet is at a significantly higher pressure than in behaviour of both elements can be attributed to the competitive MORB compositions (~10 kbar). Our results present interesting sorption between uranyl and arsenate species or due to the formation comparisons with recent crystallization experiments on a komatiite of the above mentioned uranyl-arsenate species. Further bulk composition at similar P-T conditions (4). This earlier study investigations are recommended in order to understand the reported Ol coexisting with grt at P >14 kbar and no olivine at P<14 migration of contaminants in the environment and to implement kbar. A melt phase was not reported at 1000°C and 10-18 kbar in proper measures in the remediation process. these earlier experiments, but is ubiquitous in our experiments. A first order implication of the new results is that if Archean oceanic [1] Gezahegne et al.(2009) Geochimica Et Cosmochimica Acta 73, crust were komatiitic, crustal thickness >45 km is required to A430-A430. [2] Bachmaf et al.(2009) Geochimica Et Cosmochimica Acta 73, A stabilize garnet in the melt residue. This is important to consider in 67-A67. Archean geodynamic models like crustal delamination that invoke [3] Schulze & Merkel (2011) The New Uranium Mining Boom: density inversions resulting from stabilization of garnet bearing Challenge and Lessons Learned, 573-578 assemblages in the mafic lower-crust.
[1] Furnes et al. (2007) Science.315, 1704-1707.[2] Nair and Chacko (2002) J. of Petrol.43, 2121-2142. [3] Kretz (1983) Am. Mineral. 68, 277-279.[4] Foley et al. (2003) Nature 421, 249-252.
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elements during the adsorption on PRITAM NASIPURI1*, HOLGER STUNITZ1, LUCA MENEGON1, iron and manganese oxides AND ALFONS BERGER 2 1 1* 1, 2 Departmnent of Geology, University of Tromsø, Norway, RYOICHI NAKADA , YOSHIO TAKAHASHI , AND MASAHARU 1, 2 [email protected] (* presenting author), TANIMIZU [email protected], [email protected] 1 Hiroshima University, Higashi-Hiroshima, Hiroshima, ryo- 2 University of Copenhagen, Denmark, [email protected] [email protected] 2 Japan Agency for Marine-Earth Science and Technology Introduction (JAMSTEC), Nankoku, Kochi Weakening of lower crustal rocks due to fluid infiltration and metamorphism is responsible for the development of ductile shear zones. In this contribution, we describe the mechanism of formation Recent development of analytical instruments, especially of ductile shear zones in a granulite facies gabbro, followed by fabric multiple collector (MC) ICP-MS, has enabled us to discuss the formation during retrogression after eclogite facies metamorphism in mass-dependent isotopic fractionation of heavy elements. Although rocks from Flakstadøy, Lofoten, Norway [1]. several rules controlling the isotopic fractionation has have been Results suggested, it is still insufficient to discuss which chemical Several mm to cm wide ductile shear zones are observed within
properties are the most important factor to evaluate bond stiffness in the leuco-gabbro. Pl0, Ol0 and Opx0 form the cumulus igneous
the equilibrium isotopic fractionation. This study, therefore, exhibits texture. Opx1 and Grt1 corona around Pl0 and Ol0 indicate granulite
the results of stable isotopic fractionation of rare earth element facies metamorphism (M1). Alternate bands of mafic (Opx0+ Omp +
(REE) during the adsorption experiment to discuss the cause of the GrtI/II) and felsic (Pl + Amp + Spl) layers characterize the shear zone.
isotopic fractionation among REE. The Opx0 porphyroclasts are mantled by recrystallized OpxII grains Lanthanum, Ce, Nd, and Sm chloride solutions with various (20-30 mm) and show asymmetrical σ-porphyroclast indicative of
concentrations were respectively added to both synthesized sinistral sense of shear (D1). Static overgrowth of Omp ± GrtII around
ferrihydrite and G-MnO2 suspensions. In all the systems, pH was Opx0/II is the peak pressure metamorphic stage (M2A). Subsequently,
adjusted to 5.00 (±0.05) and shaken for 6 hours before the filtration. Cpx - Pl symplectite (M2B) form at the outer rim the Omp.
Stable isotope ratios in both liquid and solid phases were determined Breakdown of Grt I/II to Amph r Pl (An rich) r Spl with opposite
using MC-ICP-MS. REE-Cl3 solutions used in the adsorption shear sense in the Opx0/II defined fabric characterize M3 experiment were employed as standard solutions and the isotope metamorphism.
ratio of each element was expressed in epsilon notation relative to Alternate bands of mafic (Cpx + Pl + Qtz + Grt II – Ol0 - Opx0 -
the average standards, which is shown in the equation as follows: H= Omp) layer (≈M2B)and felsic (Pl+ Amp + Cz – Spl) layer characterize 4 139 138 (Rsample/RST D – 1) u10 , where R was defined as La/ La, the fabric in the retrograde eclogite. Amp and Cz overgrows at the 142 140 145 143 149 147 Ce/ Ce, Nd/ Nd, or Sm/ Sm, respectively. For the solid contact between the mafic and felsic layers (≈ M3). phase, K-edge EXAFS of filtered samples was measured at BL01B1 In the ductile shear zone, chemical similarity and CPO data of
in SPring-8 to obtain the information of the coordination Opx0 and OpxII indicate that Opx0 deformed by cracking (D1) at the
environment. onset of M1-metamorphism. The fine-grained Pl shows a strong CPO
Though accurate determination of La isotope ratio was indicative of inheritance of the CPO from D1 deformation. The CPO difficult due to the large difference in the isotopic abundance of amphibole suggests that amphibole re-orients by rigid body 138 139 between La and La, a broad trend obtained in this study rotation forming aligned (100) planes during post D1 deformation. suggested that the lighter La isotope was selectively partitioned into In the retrograde variety, the CPO data of Cpx from the mixed the solid phase. In Ce system, it is clearly shown that the lighter phase mafic layers is consistent with the (010) [001] dominant slip isotope was partitioned into solid phase, whereas in Nd and Sm system but is interpreted as oriented-growth-fabric during diffusion systems, lighter isotopes remained in the liquid phase, suggesting creep, because the mixed-phase-fabric does not indicate dislocation that physicochemical factors have been changed between Ce and Nd. creep microstructures. CPO data of recrystallized plagioclase in the According to the EXAFS analysis, split first shell (La-O bond) was mono-mineralic felsic layers indicate (010) [100] as dominant slip observed for La-adsorption system, suggesting that the first system during dislocation creep. coordination sphere is distorted in the system. Such distortion was Conclusions also expected for Ce-adsorption system from their EXAFS results. This study indicates that deformation of Opx via cracking (D1) On the other hand, split first shell was not observed for Nd and Sm requires very high differential stress at lower crustal conditions [3] systems. Thus, it is expected that the slight change in coordination during M1 stage. However, in the retrograde eclogite, Omp environment, which can also cause the difference in their hydration breakdown will produce fine-grained Cpx+Pl mixtures [4] and numbers, affects the direction and degrees of mass-dependent promotes diffusion creep accommodated fabric formation. isotope fractionations among REE. [1] Markl & Bucher (1997) Lithos 42, 15-35. [2] Kretz (1983) Am. Min. 68, 277-279. [3] Steltolphel et al. (2006) Geosphere 2, 61-72. [4] Anderson & Mocher (2007) Contrib. Min. Pet. 154, 253-277.
Mineralogical Magazine | www.minersoc.org 2157 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Origin of Magnetite “Lava Flows” at Mudstone pore networks: El Laco Volcano, Chile characterization and flow modeling 1* 2 3 H.R. NASLUND , F.J. HENRIQUEZ , J.O. NYSTRÖM , ALEXIS NAVARRE-SITCHLER1*, KATHERINE MOUZAKIS1, 2 3 3 4 5 GERNOT ROTHER , JASON HEATH , TOM DEWERS , JOHN J.A. NARANJO AND R.D. MATHUR MCCRAY1 1SUNY-Binghamton, Geological Sciences, Naslund@ 1Department of Civil and Environmental Engineering, Colorado Binghamton.edu (*presenting author) School of Mines, Golden CO, USA, [email protected] 2Universidad de Santiago de Chile, [email protected] (*presenting author) 3Swedish Museum of Natural History, [email protected] 2 Oak Ridge National Laboratory, Oak Ridge TN, USA 4SERNAGEOMIN, Santiago, Chile, [email protected] 3 Sandia National Laboratories, Albuquerque NM, USA 5Juniata College, Huntingdon, PA, [email protected]
In geochemically active systems the pore network is arguably Introduction: the most important physical characteristic of a rock because it Iron ore bodies at El Laco volcano have the appearance of dikes, provides pathways for reactive fluid flow and solute transport. The lava flows, scoria, ash, and other pyroclastics and are composed of pore network is defined by an interface that advances and retreats almost pure magnetite. Although an origin as Fe-oxide magmas has with mineral precipitation and dissolution. These geochemical reactions can change important physical rock properties, such as been proposed by many investigators [1], others have suggested an interfacial roughness and area, and pore volume and connectivity, origin as hydrothermal or metasomatic replacement deposits [2, 3]. that in turn influence rates and mechanisms of future geochemical reactions and fluid flow. Despite their importance on geochemical Magnetite Composition: behaviour of rocks, pore networks and their evolution with Excluding samples with obvious minor pyroxene or apatite, geochemical reaction are poorly understood. However, characterizing pore networks is not straightforward due to their dynamic nature and magnetite ore samples are 95 to 97% iron oxide with: 0.6-1.5% features at different length scales (nm to mm). SiO2; 0.01-0.03% TiO2; 0.15-0.69% Al2O3; 0.002-0.039% MnO; Problems associated with the characterization of pore networks 0.09-1.20% MgO; 0.18-1.18% CaO; 0.03-0.38% Na2O; 0.05-0.21% are compounded in fine-grained rocks such as shales and mudstones
K2O; and 0.8-2.5% P2O5. Trace element abundances in the ore that have a high percentage of nm scale pores. However, these rock average: 90 ppm Ba; 96 ppm Co; 26 ppm Cr; 212 ppm Ni; 9 ppm Sc; types are increasingly important due to the role they play in unconventional natural gas production and geologic CO storage. 147 ppm Sr; 793 ppm V; 105 ppm Zn; 5 ppm Zr; and 24 ppm Y. 2 Small angle neutron scattering (SANS) is an ideal tool to study Relative to associated unaltered andesites, the ores are enriched structural heterogeneties in porous materials on nanometer to micron (ores/andesites) in Ni (7.7), P (7.3), V (5.3), Cu (2.6), and Zn (1.6), length scales and compliments other traditional techniques such as and depleted in Cr (0.7), Sc (0.6), Sr (0.3), Ba (0.2), Mn (0.1), Zr sorption, mercury intrusion porosimetry (MIP), or microscopy. (0.03), and Ti (0.02). The ores are enriched in REEs (La 150X and In this study we characterized the nm to mm scale pore network in samples from three different mudstone formations using SANS, Yb 14X chondritic) with steep LREE slopes (La /Sm = 8.1), N N MIP, BET gas adsorption techniques and focused ion beam scanning relatively flat HREE slopes (SmN/YbN = 1.7), middle REE electron microscopy imaging. These formations all serve as seals for
depletions (Sm/Sm* = 0.23), and negative Eu anomalies (Eu/Eu* = containment of CO2 in prospective geologic storage sites. Porosity 0.5). In contrast, associated unaltered andesites have similar and surface area in pores < 700 nm diameter was measured with abundances (La 145X and Yb 12X chondritic) but less steep LREE small angle neutron scattering. According to this data pores < 10 nm radius contribute 20-50% of the total porosity and > 80% of the total (La /Sm = 4.6), steeper HREE (Sm /Yb = 2.7), less middle REE N N N N surface area of these mudstones. The total pore volume determined depletion (Sm/Sm* = 0.39), and less Eu depletion (Eu/Eu* = 0.65). from small angle neutron scattering is higher than porosity Fe isotopes in the ores (G56 = 0.52-0.90‰) are elevated relative to determined from mercury instrusion porosity for most of the samples. fumarolic and vein deposits (G56 = 0.23-0.29‰) or andesites (G56 The discrepancy between these measured porosities may be related to = 0.49‰) at El Laco. In a single ore sample measured, Re = 460 low pore connectivity or the inability of MIP to fully access the pore 187 188 187 188 network due to pressure limitations of the method. A comparison of ppt, Os = 23 ppt, Os/ Osmeasured = 0.52, Re/ Osmeasured = 2, 187 188 cumulative pore fractions determined from SANS and MIP suggests and Os/ Osinitial = 0.51 indicates that there is a large that < 30% of the total porosity is accessible through pore throats < 1 contribution of Os from the continental crust. nm radius. At these length scales Fickian diffusion of solutes and Knudsen diffusion of gas become the dominant transport Conclusions: mechanisms. The high abundance of some relatively immobile elements (V, These data demonstrate the importance of very small pores to the overall pore structure of the mudstones. To really understand pore Ni, Y, and REEs) and the low abundance of other immobile scale processes we need to not only develop a fully realized view of elements (Zr, Ti, Cr, and Sc) is inconsistent with a hydrothermal or what the pore network looks like at multiple length scales but also replacement origin for the ores. G56 Fe in the ores is systematically understand how different techniques provide windows into that view. higher than G56 Fe in hydrothermal magnetite. Immiscibility Results from flow simulation using pore networks created from FIB- between silicate magma and volatile-rich Fe-P-S-O magma, possibly SEM data will be presented. These simulations will help determine the contribution of different types of flow mechanisms and will form initiated by crustal contamination, is compatible with all of the data. the basis for reactive transport models of geochemial processes. Sandia is a multiprogram laboratory operated by Sandia [1] Naslund et al. (2002) Hydrothermal iron-oxide copper-gold & Corporation, a Lockheed Martin Company, for the U.S. DOE under related deposits Vol ume 2, 207-226. [2] Rhodes et al. (1999) Soc. contract DE-ACOC4-94AL85000. of Econ. Geol. Spec. Pub. Vol ume 7, 299-351. [3] Sillitoe & Burrows (2002) Economic Geology Vol ume 97, 1101-1109.
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1 the Nordic Seas - a calibration study ALEXANDRA NAVROTSKY * 1* 1 ALBA NAVARRO RODRIGUEZ , PATRICIA CABEDO SANZ , 1Peter A. Rock Thermochemistry Lab, University of California 1 1 2 SIMON BELT , THOMAS BROWN , JOCHEN KNIES , KATRINE Davis, Davis, CA 95616 USA, [email protected] 3 4 HUSUM , AND JACQUES GIRAUDEAU
1 13f. Physicochemical constraints of the marine carbonate Plymouth University, Plymouth, UK, system: recent insights into the reactivity of carbonate [email protected] (* presenting author) minerals in aqueous solutions 2Geological Survey of Norway, Trondheim, Norway, Solution calorimetric methodology has been applied to [email protected] measuring the energetics of formation and transformation of 3University of Tromsø, Tromsø, Norway, [email protected] amorphous and nanophase carbonates in the CaCO3 - MgCO3 - 4Université Bordeaux, Bordeaux, France, [email protected] FeCO3 system. The data point to several general conclusions, bordeaux.fr summarized here. (1) Amorphous calcium carbonate (ACC) exists in
two forms: a heavily hydrated material initially precipitated from
Abstract strongly oversaturated aqueous solution and a less hydrated form, The work presented here is part of the Changing Arctic and Sub- which is energetically similar whether formed by biomineralization Arctic Environment (CASE) program which is an Initial Training or by thermal dehydration of the initially precipitated phase. Network (ITN) that focuses on biological proxies and their use in Transformation in the sequence hydrated ACC – relatively reconstructing climate change and, in particular, the marine anhydrous ACC – vaterite – aragonite – calcite is energetically environment. One of these proxies is the sea ice diatom biomarker downhill and thus ACC can be a precursor to any of these crystalline IP25 which is a highly branched isoprenoid (HBI) alkene synthesised phases. (2) Amorphous magnesium carbonate (AMC), despite being by some Arctic sea-ice diatoms and has been shown previously to be energetically more metastable than ACC, is more persistent (can be a specific, stable and sensitive proxy measure of Arctic sea ice when detected in underlying sediments [1]. kept for a year rather than a few days before crystallizing under The current study focuses on three key elements: (1) An analytical ambient conditions). This is attributed to the kinetic difficulty of calibration of IP25 isolated from marine sediments and purified removing water of hydration from the environment of Mg2+. using a range of chromatographic methods was conducted in order to (3) Amorphous iron carbonate (AFC) is energetically similar to improve the quantification of this biomarker in sediment extracts AMC but is very susceptible to crystallization and oxidation. The [2]. (2) Analysis of >30 near-surface sediments from the Nordic energetics of the amorphous versus crystalline carbonate phases Seas was carried out to quantify biomarkers previously suggested as indicators of open-water phytoplankton (brassicasterol) [3] and sea- may be controlled by the ionic radius of the cation. (4) The ACC – AMC system shows a striking change in energetic behavior near ice (IP25) conditions [4]. The outcomes of the biomarker analyses were used to make comparisons between proxy data and known sea Ca/Mg = 1. More Mg-rich compositions, though amorphous, appear ice conditions in the study area derived from satellite record over to be heterogeneous and consist of nanoscopic regions of dolomitic the last 20 years. (3) A consideration of possible processes and magnesitic composition. The amorphous material with Ca/Mg = occurring within surface sediments and the implications of these on 1 may be a precursor to dolomite. (5) Measurement of the surface downcore analysis of biomarkers for palaeo-climate energies of calcite, aragonite, and vaterite is currently in progress. reconstructions. These general trends are discussed in the context of carbonate
formation in biological, carbon sequestration, diagenetic, and fresh
[1] Belt et al. (2007) Org. Geochem. 38, 16-27. [2] Belt et al. water and oceanic environments. (2012) Environ Chem Lett DOI 10.1007/s10311-011-0344-0. [3] Müller et al. (2011) EPSL 306, 137-148. [4] Belt et al. (2010) Quaternary Science Reviews, 29 3489-3504.
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1 1* 2 1 2 ALEXANDRA NAVROTSKY * S. NAZZARENI , C. BONADIMAN , P. COMODI , B. FACCINI , P.F. 1 2 3 ZANAZZI , M. COLTORTI , AND G. GIULI 1Peter A. Rock Thermochemistry Lab, University of California Davis, Davis, CA 95616 USA, [email protected] 1 Department Earth Sciences, University of Perugia, Italy [email protected] Keynote Speaker 2Department Earth Sciences, University of Ferrara. Italy Many low temperature aqueous geochemical processes involve 3 Scuola di Scienze e Tecnologia, University of Camerino the precipitation, dissolution, and redox reactions of fine - grained (nanophase) transition metal oxide minerals. Because phases with Spinel-bearing lherzolites and wehrlites from Baker Rocks (Northern different oxidation states have different structures and, often, Victoria Land, Antartica) have pargasitic amphiboles as metasomatic different surface energies, their redox phase boundaries can be phase [1]. We investigated the amphiboles in order to estimate the significantly shited in oxygen fugacity - temperature space at the physico-chemical conditions of their formation and, combined with the nanoscale. We have shown, for example, that FeO (wustite) has no H2O content in coexistent pyroxenes, to estimate the total water budget stability field at the nanoscale, and that the stability field of of this mantle domain. The samples were analysed by Single-Crystal magnetite is expanded relative to both reduction (to iron) and XRD, EMPA, SIMS and XANES to have an accurate crystalchemical oxidation (to hematite) for small particles. A current calorimetric formula and to calculate the fH2 and ultimately the fO2 and aH2O. The study suggests that fayalite has a higher surface energy than the crystalchemical data showed that these amphiboles have similar assemblage magnetite plus quartz, thus shifting the QFM buffer to composition, irrespective of the textural position and lithotype. The high more reducing conditions for nanoparticles. In the manganese equivalent thermal factor and cation off-centering suggest partition of Ti oxides, the phase field of Mn3O4 (hausmannite) is expanded relative at M1 site. The high M3 site distortion and low
[1] Coltorti et al.(2004) Lithos, 75, 115-139. [2] Oberti et al. (2007) Rev. Mineral MSAGS, 67, 125-164171; [3] Lamb & Popp (2009) Am. Mineral, 94, 41-59; [4] Ballhaus et al. (1991) Contrib. Mineral. Petrol,78, 27-40 [5] Bonadiman et. Al. (2009) Eur. J. Min., 21, 637-647
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K. NEGRICH1*, J.L. BAUMEISTER2, E. YARDLEY1, J. MACRAE1, Carpathians 2 1 E.M. HAUSRATH , AND A.A. OLSEN 1* 1 ELENA NEGULESCU AND GAVRIL SĂBĂU 1University of Maine, Orono, USA, [email protected] 1Geological Institute Of Romania, Bucharest, Romania (*presenting author); [email protected]; [email protected] (*presenting author), [email protected] [email protected]; [email protected] 2 University of Nevada, Las Vegas, USA, The Leaota Massif basement comprises several concordant
[email protected]; [email protected] units characterized by internal lithologic and metamorphic contrasts.
Eclogite and metagabbronorite lenses, hosted in a semipelitic Biological processes, specifically mediated by microbial matrix, appear sandwiched between two units of pelitic/meta- communities, are closely tied to mineral weathering. Serpentinites, igneous composition. for example, exert strong controls on the biota that develop on them. The eclogite lenses are chemically zoned, as best exemplified The bulk chemistry of serpentinite rocks is high in Mg and trace by the Bughiţa Albeştilor (BA) occurrence, displaying several well- elements and low in nutrients such as Ca, K, P, and N. This causes defined concentric zones, from fine-grained massive phengite-free an extreme and stressful environment for plants and microbes, that domains that grade outwards into phengite-rich zones. The mineral has been extensively studied by ecologists [1]. However, the role that assemblage of the phengite-free domain is garnet + omphacite + serpentine biota play in development of serpentine soils has not been amphibole + zoisite + quartz + rutile. The phengite-rich zone examined. In order to address this question, we have observed preserved a low-variance mineral assemblage of garnet - omphacite - biogeochemical weathering of serpentinite in the field, and we are phengite - paragonite - amphibole - kyanite - clinozoisite - quartz – conducting laboratory studies to examine how iron-oxidizing bacteria rutile. Mg-rich staurolite (X = 0.29 – 0.40) was rarely identified and oxalic acid influence weathering rates of serpentine minerals. Mg in kyanite porphyroblasts. Whole-rock compositions approach N- Field samples from the Trinity Ultramafic Complex in the MORB to E-MORB, the latter ones also displaying HFSE-depletion. Klamath Mountains, California were analyzed by biological activity The macro- and the microscopic features of these zones, reaction tests (BARTTM) to test for the presence of iron-related together with their trace elements patterns that resemble N-MORB bacteria. The BARTTM indicators tested positive for iron-related except the LILE (Rb, Ba, K, U) enrichment in the rind (fig. 1, 2), bacteria in both rock and soil cores, [2] suggesting that biological support the interpretation of the phengite-rich domains as a impacts on Fe cycling may be important. However, future work is metasomatic rind of the phengite-free inner part, ensuing interaction needed to compare lizardite dissoltuion in the presence and absence with subduction-zone fluids. of Fe-oxidizing bacteria. 100 Lab experiments were performed to test the effect of oxalic acid Rind 10 on lizardite dissolution. Oxalic acid is an exudate from many soil Inner part 1 fungi, and is an important ligand that binds to metals in the 0.1 surrounding soil. We found that oxalate in concentrations of 50 mMol Pb Rb Ba K U Nb La Ce Sr Sm Zr Eu Ti Gd Tb Dy Y Ho Er Tm Y b Lu
enhanced lizardite weathering by a factor of six [3]. Figure 1: N-MORB-normalized [1] trace elements abundance of We also plan to complete similar lab experiments with iron- the inner part and its metasomatised rind of the BA-eclogites oxidizing bacteria. We hypothesize that iron-oxidizing bacteria
enhance lizardite dissolution, contributing to early serpentinite 100 Ba weathering in deep profiles. Crushed lizardite grains will be reacted K Rind/Inner part Rb in batch solutions with Acidithiobacillus ferrooxidans; a species 10 U Nb La Ce Sm Zr Eu Y common in acid mine drainage [4], Ferritrophicum radicicola; a 1 Ti Gd Tb Pb Dy Ho Er Tm Yb Lu neutrophilic species isolated from a wetland rhizosphere, and in 0.1 Sr
abiotic solutions [5]. Experiments will be conducted at a range of pH Figure 2: Chemical variation between the inner part and its values, but constrained by the survival needs of each species. metasomatised rind of the BA-eclogites Aliquots of solution will be extracted and analyzed for Mg, Si, Fe, Al, Ni, Cr, Cu, Co, and Ti using ICP-MS. Magnesium and silicon The geochemical features of the eclogite and metagabbronorite release rates will be used to calculate dissolution rates of lizardite in knockers, especially the distinctive LILE enrichment, document both biotic and abiotic experiments. Iron-oxide precipitates will be subduction-zone metamorphism of normal and SSZ ocean floor analyzed with SEM-EDS. Measured dissolution rates in the presence remnants enclosed in a subduction mélange. The LILE- of microorganisms will be compared to abiotic dissolution rates, and metasomatism of the semipelitic matrix rocks themselves, used in reactive transport modeling of the field area. demonstrated by high Ba contents of K-white micas [2], also support [1] Kazakou et al. (2008) Biological Reviews 83, 495-508. [2] this interpretation. Baumeister et al., in prep. [3] Yardley, E. (2012) M.S. Thesis. [4] Santelli et al. (2001) Chemical Geology 180, 99-115. [5] Weiss et al. [1] Sun, McDonough (1989) Geol.Soc.Special Publications 42, (2007) Geomicrobiology Journal 24, 559-570. 313-345. [2] Negulescu, Săbău (1999) An. Univ. Bucureşti XLVIII,55-58.
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Micas and columbite-tantalite from Using a surface precipitation some Portuguese granitic aplite- approach to model the pegmatites continuum between Hg
1* 2 2 A.M.R. NEIVA , P.B. SILVA , AND J.M.F. RAMOS adsorption and precipitation 1University of Coimbra, Geosciences Centre Earth Sciences, onto Bacillus subtilis Portugal, [email protected] (* presenting author) * 2National Laboratory of Energy and Geology, S. Mamede de Infesta, RYAN M. NELL , JENNIFER E.S. Portugal, [email protected]; [email protected] SZYMANOWSKI, JEREMY B. FEIN
University of Notre Dame, Civil Engineering and Geological Different micas occur in granitic beryl-columbite-phosphate Sciences, Notre Dame, IN 46556 (*presenting author, subtype aplite-pegmatite veins and sills from the Sabugal area. [email protected]) Subhedral lithian muscovite surrounds relics and penetrates along cleavages of primary muscovite, showing sharp contacts. The lithian The effect of bacterial cell wall adsorption on the muscovite containing higher Fe2+, Li and F contents replaces precipitation of mineral phases in supersaturated systems is not well constrained experimentally, although there is primary muscovite. Radial lithian muscovite from aplite presents 2+ circumstantial evidence for enhanced precipitation in these lighter areas (richer in Fe , Li and F) surrounding and penetrating systems with the presence of bacteria. Surface complexation VI IV VI darker areas (richer in Al , Al + Al and OH) in BSE images and modeling has been applied successfully to model the showing sharp contacts, suggesting that the former areas replace the adsorption of a wide range of aqueous metal cations onto latter areas. Primary muscovite and lithian muscovite from aplite and bacterial cell walls. Surface precipitation theory represents an extension of surface complexation modeling that can bridge aplite-pegmatite have higher Fe2+, Li, Rb and F contents and lower the continuum between adsorption and precipitation. Mg content than primary muscovite from the parent granite and However, only a small number of studies have examined the define a trend in the Li-Mg diagram. Very rare lepidolite from effect of bacteria on mineral precipitation reactions in well- aplite-pegmatite surrounds lithian muscovite. In aplite-pegmatite, controlled experiments, so testing and calibration of the zinnwaldite penetrates along cleavages and partially surrounds lithian surface precipitation modeling approach is limited for bacterial systems. In this study, we measured the extent of muscovite, suggesting that the former replaces the latter. Locally Hg(II) removal from solution, in the presence and absence of zinnwaldite and lithian muscovite seem to show different non-metabolizing cells of Bacillus subtilis in both sulfide- orientations. All contacts are sharp. Rare polylithionite partially free and sulfide-bearing systems under a range of surrounds lithian muscovite from aplite. The rim has higher Si, Li, concentrations from undersaturation to supersaturation with Rb and F contents and lower AlIV + AlVI and OH contents than the respect to solid phase HgO and HgS, respectively. Initial Hg molalities ranged from 10-5 to 10-2 m at pH 4.5; ionic strength core. The compositions of the micas studied are well distinguished was buffered by conducting the experiments in 0.01 M in Li-R3+ + Ti-R2+ and AlIV + AlVI versus Fe + Mg diagrams. The NaClO4, and the wet mass of bacteria used in each biotic lithium micas resulted from the accumulation of F and Li in experiment was held constant at 5 g/L. Sulfide-free derivative silicate liquids. Primary muscovite is texturally and experiments were conducted aerobically with a two-hour chemically identified. Lithium micas have higher Li, F contents and equilibration period. Sulfide experiments were conducted with varying concentrations of Na-sulfide under anaerobic lower Al VI, AlIV + AlVI and OH contents than primary muscovite. conditions. Samples from both types of experiments were Columbite-tantalite from granitic aplite-pegmatites veins and filtered and analyzed for aqueous Hg by a Hydra II AF sills from the Sabugal area occurs associated with K-feldspar, albite, Mercury Analyzer following the ASTM International quartz, muscovite and beryl. Columbite-(Fe) is more abundant than standard test method for mercury in water. columbite-(Mn) and tantalite-(Fe) is rare. Individual crystals of The biotic systems exhibited enhanced Hg(II) removal columbite-(Fe) are complexely zoned, showing alternating light BSE relative to the abiotic controls in undersaturated conditions, contrast zones high in W, Ta, Sn and F and dark BSE contrast zones likely due to Hg(II) adsorption onto cell wall functional high in Nb and Ti. Other complexely zoned crystals have col-(Mn) groups. However, under the highest Hg concentrations containing higher Nb, Mn contents, and lower Ta, Fe contents and studied in the sulfide-free system, the bacteria inhibit Ta/(Ta+Nb) value than col-(Fe). A zoned columbite-(Fe) crystal precipitation, maintaining high concentrations of Hg in solution. We use surface precipitation modeling to account shows the lighter zones containing higher Ta, Fe contents and for the range of Hg removal that we observed in the sulfide- Ta/(Ta+Nb) value and lower Nb content than the darker zones. In this bearing system, yielding equilibrium constants that can crystal, a partial thin rim of tantalite-(Fe) is the richest in Ta, Sn, Ti, quantitatively account for Hg adsorption and precipitation Sc, Fe and Mg contents and Ta/(Ta+Nb) value and the poorest in W, with a single set of parameters. This approach offers promise Nb and Mn contents. Columbite-tantalite is a primary phase. Crystals for modeling the fate and distribution of aqueous metals in geologic systems with a wide range of saturation state are complexely zoned, showing sharp contacts between zones, with conditions. exchange of Nb↔Ta and Fe↔Mn, suggesting that magmatic fluxes may have played a role, but diffusive reequilibration was not very important. The increasing content of fluxing elements like Li, F. B and P increase the solubility of columbite-(Mn). This type of zoning may be due to disequilibrium conditions.
Mineralogical Magazine | www.minersoc.org 2162 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Microstructures in lunar zircon: key Metal speciation and dynamics of to interpretation of U-Pb ages carrier phases in a boreal forested
1* 1 catchment under transient chemical ALEXANDER A. NEMCHIN , MARION L. GRANGE , NICHOLAS 1 1 conditions E. TIMMS AND ROBERT T. PIDGEON
1Curtin University, Perth, Australia, [email protected] 1* 2 ELISABETH NEUBAUER , STEPHAN KÖHLER , FRANK V.D. 1 3 1 The interpretation of internal microstructures has become an KAMMER , HJALMAR LAUDON AND THILO HOFMANN integral part of geochronological studies using the U-Pb system in 1University of Vienna, Department of Environmental Geosciences, zircon from terrestrial samples. However, U-Pb analysis of lunar Vienna, Austria, [email protected], zircon was abandoned in late 80s and only recently resumed and [email protected] (*presenting author) combined with imaging utilising different methods available to 2SLU, Department of Aquatic Sciences and Assessment, Uppsala, reveal internal microstructures in these grains. Extensive study of Sweden lunar zircons during the last few years resulted in accumulation of 3SLU, Department of Forest Ecology and Management, Umeå, data sufficient to build a preliminary classification of their internal Sweden structures. This classification is essential for the correct interpretation of U-Pb ages. It is particularly important because The formation and fate of natural aquatic colloids was majority of lunar zircons occur as abraded, broken fragments in the investigated in a boreal catchment (68 km2) with transient pH matrix of the breccias, with no evidence of their origin or history. conditions (pH 3.8-6.4) and diverse landcover types (wetland, forest Also, increasingly, we are finding zircon grains with complex U-Pb and sediment dominated). We examined the influence of colloids on age patterns, which makes interpretation difficult. The only way of metal speciation, i.e. iron, aluminum, arsenic, manganese, and rare addressing these issues is studying the textures and structures in earth elements (REE). lunar zircons and cross correlating this information with the observed Flow-Field Flow Fractionation [1], membrane filtration (0.2 pattern of U-Pb ages determined by ion microprobe analyses. μm), cation exchange column separation [2], ultrafiltration (1 kDa) Lunar zircons are classified according to: (i) textural and scanning electron microscopy were used to characterize relationships between zircon and surrounding minerals in the colloids and to quantify colloid-metal associations. breccias, (ii) the internal microstructures of the zircon grains and (iii) In the small headwater catchments, complexation with natural in-situ analyses of Th-U-Pb isotopic systems with ion microprobe. organic matter (NOM) was dominating the speciation of iron, Both igneous (primary) and impact (secondary) features can be aluminum, manganese and REEs. 50-70% of the total arsenic was identified in lunar zircon. associated with NOM, and substantial concentrations were present Primary zircons occur as part of a cogenetic mineral assemblage as dissolved species. Along the natural pH gradient we observed a (lithic clast) or as individual mineral clasts and are unzoned, or have gradual increase of iron in form of iron-oxy(hydr)oxide particles sector zoning or rarely oscillatory zoning. U-Pb ages of zircons (50 nm up to several hundred nm). Despite this increase, REEs were exhibiting these microstructures determine the timing of magmatic still associated to colloidal NOM, while up to 30% of arsenic and crystallisation. manganese adsorbed or co-precipitated with the iron particles. Secondary microstructures include locally recrystallised Chemical equilibrium modelling confirmed that complexation domains, localised amorphization, crystal-plastic deformation, planar of REEs to NOM was stronger than the sorption of REEs to iron- deformation features and fractures, and are associated with impact oxy(hydr)oxides. The concentration of iron minerals can only be metamorphism. The first two types often yield internally consistent, explained by a stronger than expected Fe-NOM complexation. The concordant U-Pb ages that date impact events. The absolute ages of complexation constant would then be higher than in the data base of other secondary microstructures cannot be determined. Nevertheless, Minteq [3]. it is possible to define their relative timing from the relationships We quantified fluxes from all sub-catchments and used with other microstructures. In addition, regular occurence of these landscape type analysis for the estimation of metal export. Mass features (e.g. planar deformation features are found in lunar zircon balances indicate that there is no loss of iron and trace elements along {001}, {110}, and {112}, typically with 0.1-25 μm spacing during the transport through the catchment, despite the formation of and {112} commonly contain micro-twin lamellae with 65° / <110> relatively large iron-oxy(hydr)oxides particles. An additional source misorientation relationships, while dislocation creep commonly of iron, manganese, and sulphate through groundwater influx forms deformation bands parallel to {100} planes) can be explained accounts for the observed total export from the catchment. Our in terms of elastic anisotropy of zircon and used to predict conditions study implies that the trace metals mobilized from the different experienced by different zircon grains during the impacts. upstream sites behave mainly conservative despite shifts in Planar deformation features, crystal-plastic deformation and speciation. Mass balance calculation does allow for the micro-fractures can provide channels for Pb diffusion and their quantification of the relative contribution of the different landscape identification can explain some instances of partial resetting of the elements for total metal flux. U-Pb isotopic system. Consequently their identification in a zircon grain should prompt a careful examination of the U-Pb ages obtained [1] Neubauer et al. (2011) J. Chromatogr., A. 1218, 6763-6773. [2] in this grain and their significance. Hruska et al. (1996) Water Resour. Res. 32, 2841-2851. [3] Sjöstedt et al. (2010) Environ. Sci. Technol. 44, 8587-8593.
Mineralogical Magazine | www.minersoc.org 2163 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts
Interfacial Fe(II)-Fe(III) electron Paired 87Sr/86Sr - δ88/86Sr values in transfer and atom exchange in Paleozoic conodonts
smectites: effect of smectite LEONID NEYMARK*, WAYNE PREMO, AND POUL EMSBO properties US Geological Survey, Denver, Colorado, USA [email protected] 1* 1 ANKE NEUMANN AND MICHELLE M. SCHERER (* presenting author), [email protected], [email protected].
1 Department of Civil and Environmental Engineering, The University The isotopic composition of Sr (87Sr/86Sr) is widely used as a of Iowa, Iowa City, USA, [email protected] (* tracer in paleooceanographic, paleoclimatologic, paleotectonic, and presenting author) stratigraphic investigations. Until recently, the stable Sr-isotopic ratio (88Sr/86Sr) was assumed to be constant and was used for Heterogeneous reactions between aqueous Fe(II) and Fe(III) internal normalization to correct for instrumental mass oxides have extensively been studied, leading to a new conceptual fractionation, thus masking any natural mass-dependent Sr-isotopic framework which includes electron transfer between aqueous Fe(II) fractionation. Newly developed MC-ICPMS and Double Spike (DS) and structural Fe(III), bulk electron conduction, and Fe(II)-Fe(III) TIMS methods, however, document measurable Sr isotope atom exchange [1]. A recent study showed that interfacial electron fractionation in natural systems. transfer between aqueous Fe(II) and structural Fe(III) also occurred We present the first DS TIMS δ88/86Sr (‰) data (δ88/86Sr = in one clay mineral [2]. Whether this observation can be generalized 88 86 88 86 ( Sr/ Srsample/ Sr/ SrNBS-987-1)×1000) for fossil biogenic marine for all clay minerals and whether similar processes as observed for phosphates (conodonts). The 84Sr-87Sr DS preparation and data the heterogeneous redox reaction in Fe(III) oxides are also crucial reduction followed recommendations in [1]. Our DS was calibrated for clay mineral redox reactions is unclear. against NIST SRM-987 assuming 88Sr/86Sr = 8.375209 to give Studies on chemical reduction of structural Fe in smectites δ88/86Sr = 0.002 ± 0.024 ‰ (2SD). External reproducibility was showed that the type of reductant as well as smectite structural evaluated using USGS Sr isotope standard EN-1 (a carbonate shell of properties determined the extent of Fe reduction and the resulting a giant clam Tridacna collected live from the floor of the Enewetak structural Fe(II) entities. Thus, we investigated well-characterized lagoon, Marshall Islands), which yielded δ88/86Sr = +0.262 ± 0.032 smectites differing in structural Fe content, location of structural Fe ‰ (2SD) and NRC Canada sea-water trace element reference (octahedral vs. tetrahedral), and location of excess charge material NASS-6, which yielded δ88/86Sr = +0.371 ± 0.026 ‰ (2SD). (octahedral vs. tetrahedral) for their reaction with aqueous Fe(II), a Paired 87Sr/86Sr - δ88/86Sr values were measured in 30 Paleozoic reductant abundant in natural anaerobic environments. conodont samples from different stratigraphic horizons (Middle Stable isotope specific Mössbauer spectroscopy was used to Ordovician to Middle Mississippian). The samples were screened determine the extent of reduction of structural Fe in smectites after for diagenetic alteration so that only conodonts with Color 56 exposure to aqueous Fe(II), which is invisible in Mössbauer Alteration Index CAI≤ 3.0 were analyzed. The δ88/86Sr values in these 57 spectra. Experiments with aqueous Fe(II) enriched in Fe were samples vary from slightly positive to significantly negative (up to – carried out to determine the exchange of stable Fe isotopes between 1.05 ‰). This range is significantly broader than the variability aqueous Fe(II) and structural Fe(III) in smectites. Different pools of observed in Paleozoic marine brachiopods [2] but is similar to the Fe(II) and Fe(III) were investigated by sequential extraction range in human tooth enamel and bone [3]. The reasons for this procedures and solid reaction products were characterized with X- variability in conodonts are not well understood, but likely reflect ray diffraction and electron-based microscopic methods. changes in seawater composition and/or biogenic fractionation of Sr isotopes. The range in δ88/86Sr also causes 87Sr/86Sr values based on DS measurements to deviate appreciably from 87Sr/86Sr values determined using conventional mass-fractionation corrections. Our results indicate that the study of conodont δ88/86Sr values has the potential for better constraining the marine Sr cycle and its relation to secular changes in marine chemical and biologic systems.
[1] Rudge et al. (2009) Chemical Geology 265, 420-431. [2] Vollstaedt et al. (2011) Geophysical Research Abstracts 13, EGU2011-7257 [3] Knudson et al. (2010) J. Archaeol. Sci. 9, 2352-2364.
[1] Gorski & Scherer (2011) Aquatic Redox Chemistry, 1071, 315- 343, [2] Schaefer, Gorski & Scherer (2011) Environ. Sci. Technol. 45, 540-545.
Mineralogical Magazine | www.minersoc.org 2164 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Using PLFA to constrain microbial Identifying the arsenic source in distribution related to S-cycling in oil- glacial aquifer sediments, west- sands composite tailings during central Minnesota, USA 1 2 reclamation SARAH L. NICHOLAS *, BRANDY M. TONER , MELINDA L. 3 4 1 1 2 ERICKSON , ALAN R. KNAEBLE NGONADI, N.* , ZIOLKOWSKI, L.A. , PENNER, T. , 1 1 Land and Atmospheric Sciences Graduate Program, Department of SLATER, G.F. Soil, Water, and Climate, University of Minnesota, Saint Paul, 1 McMaster University, Hamilton, Canada [email protected] MN, USA (*presenting author) [email protected] 2 Syncrude Environmental Research, Edmonton, Canada 2Department of Soil, Water, and Climate, University of Minnesota, Saint Paul, MN, USA [email protected] Understanding the extent and nature of biogeochemical cycling 3United States Geological Survey Minnesota Water Science Center, by microbial communities is a critical component of predicting and Mounds View, Minnesota USA [email protected] 4Minnesota Geological Survey, Minneapolis, Minnesota USA managing their impact within systems. This study is applying [email protected] phospholipid fatty acid (PLFA) analysis to investigate the microbial communities associated with reclamation of composite tailings X-ray absorption spectroscopy (XAS) and sequential extractions were used to identify and quantify different arsenic (As) recently initiated at Syncrude’s Mildred Lake site. PLFA species present in glacial aquifer materials from west-central concentrations and distributions were determined within the sand Minnesota, USA. Sample locations were chosen based on proximity to domestic drinking water wells with As concentrations exceeding cap that separates the fen reclamation from the CT below, as well as the 10μgL-1 maximum contaminant level for drinking water in the in the CT itself. The goal was to determine how cell densities and United States. Glacial sediments were collected from rotary-sonic drill cores (25-100m depth). microbial community parameters varied between the CT and the sand Sequential extractions were used to quantify arsenic species cap, and to determine the relatively importance of these concentrations. Total (all species) arsenic concentrations of the glacial aquifer sediments are not unusually high, however the communities to biogeochemical cycling of sulphur, particularly H S 2 concentration of labile species of arsenic are unusually high. Here generation. the labile species are defined operationally as those liberated by - -3 anion exchange with Cl and PO4 . Labile As concentrations in many samples are near or above the crustal average of about 1-1.8mg Results from sand cap samples show cell densities in the 10^7 kg-1 for all forms of solid-phase arsenic. range based on generic conversion factors, not unexpected for X-ray absorption spectroscopy of the samples shows that arsenic is present in three oxidation states: As5+, As3+, and As1- to 2-. oligotrophic conditions. The presence of branched PLFA, Non-uniform distribution of oxidized arsenic may explain the spatial particularly iso and anteiso C15:0 are indicative of the presence of heterogeneity of high As wells in the area. Arsenic-bearing sulfide minerals in the Cretaceous shale sulphate reducing organisms in the sand cap. Such organisms have fragments found in these glacial sediments are frequently also been enriched from these samples. Analysis of CT samples in hypothesized to be the source of arsenic in drinking water in west- central Minnesota. Our data suggest that the solid-phase arsenic on-going and will be compared to these surface samples to sources in water are likely to be the more labile, oxidized species determine whether microbial cycling rates are expected to be lower found in unusual abundance in these samples. Most As-bearing or higher within the CT which has a highly distinct geochemistry to sulfide minerals would be expected to be chemically refractory in the reduced groundwater of the area. the sand cap, including the presence of abundant sulphate, used in flocculation of tailings.
The results of these studies will yield insight into the cycling that may be carried out by these communities. They also provide the foundational understanding for on-going isotopic studies of microbial carbon sources and cycling.
Mineralogical Magazine | www.minersoc.org 2165 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Geomicrobiological and Geochemical Bulk redox status or redox Study on Pockmarks in the SW microenvironments: Which is more Barents Sea important for controlling trace 1* 1 2 JULIA NICKEL , KAI MANGELSDORF , JENS KALLMEYER , element transport? 1 3 ROLANDO DI PRIMIO , AND DANIEL STODDART 1* 1 PETER S. NICO , CHARULEKA VARADHARAJAN , HARRY R. 1 1 1 1 Helmholtz Centre Potsdam GFZ German Research Centre for BELLER , RUYANG HAN , LI YANG , EOIN L. BRODIE, MARK 1 CONRAD, MARKUS BILL, AARON J. SLOWEY , WILLIAM Geosciences, Telegrafenberg D-14473 Potsdam, Germany, 1 MOSES [email protected] (* presenting author) 1Lawrence Berkeley National Laboratory, Berkeley, CA, USA 2 University of Potsdam, Karl-Liebknecht-Strasse 24, Haus 27, D- [email protected] (* presenting author) 14476 Potsdam, Germany [email protected] 3 Lundin Petroleum Norway, Strandveien 50D, 1366 Lysaker, [email protected] Norway [email protected] [email protected]
[email protected] Introduction [email protected] Widespread areas of the seabed in the southwestern Barents Sea are [email protected] dominated by pockmarks, being manifestations of hydrocarbon venting and are, therefore, of considerable interest as possible indi- [email protected] cators for deeper hydrocarbon reservoirs. Concomitantly, they form [email protected] specific habitats for microbial communities. These pockmarks and the associated microbial ecosystems are in the focus of the current The redox form of trace elements is frequently the major study using biogeochemical and microbiological approaches. control on the tansport of those elements within soil and sediment During two research cruises in 2009 and 2011, funded by the Swe- systems. However, what controls the transformation from one dish oil company Lundin, about 42 surface sediment cores of up to 2.5 m length were selected. For comparison cores were taken inside redox form to another is much more debatable. Clearly the and outside of the pockmark structures. dominant or bulk redox condition of a sytem has an important impact on the chemical form of the trace metals therein. However, rarely Results and Conclusion can trace metal behavior be simply predicted by bulk redox The analysis of methane within the pockmarks reveals only marginal measurements. The current presentation will focus on recent work amounts of gas, indicating that nowadays the pockmarks system is studying the bioreduction of Cr(VI) to Cr(III) under differing more or less inactive. Also microbial activity is astonishingly low in - dominant terminal electron acceptor (TEA) conditions (i.e. NO3 , the entire sampling area as indicated by low sulfate reduction rates. native Fe(III)-containing minerals, and SO 2-) and the subsequent Processes like anaerobic oxidation of methane (AOM) can be ex- 4 cluded for this depth interval since methane concentration and net remobilization of that Cr via reoxidation. sulfate consumption are very low. For the bioreduction phase of the experiment, advective flow Different biomarkers have been analyzed being indicators for fossil laboratory columns packed with Hanford 100H aquifer sediments hydrocarbons (e.g. n-alkanes, hopanoids and steranes), or past mi- were subject to oxygen-free, synthetic groundwater containing crobial populations (glycerol dialkyl glycerol tetraethers (GDGTs)). Cr(VI) and lactate in the presence of different electron acceptors Biomarker profiles do not show significant differences between (NO -, native Fe(III)-containing minerals, and SO 2-). Chromate pockmark and reference sites, inferring that fluid flow through the 3 4 removal was observed under all conditions to varying degrees. The present pockmarks is currently not taking place. However, in the deeper core section an increase for hydrocarbons and microbial nitrate-treated columns, all of which exhibited denitrifying markers is detectable which might indicate the transition to the conditions, as well as in some of the sulfate-amended columns in interval of paleo-seepage. which fermentative conditions were dominant, showed the most The results show that the observed pockmarks are rather relicts of rapid removal of Cr(VI). After approximately one year, selected paleo-seepage than indicators for active fluid flow. Their formation replicates of the nitrate-amended and sulfate-amended (one is most likely related to paleo-events of decaying gas hydrates in- fermenting, one not) conditions were removed from the glovebox duced by the pressure release from the melting ice shield during last deglaciation (approx. 13ka B.P.). [1] and presented with oxygen and nitrate containing, lactate- and Microorganisms, which are involved in the methane cycle, show a chromate-free synthetic ground water in order to promote oxidative characteristic light carbon isotopic composition (δ13C). [2] remobilization of Cr. Currently, the δ13C values of GDGTs from top and bottom part of Interestingly, the solid-state form of Cr at the end of the the sample cores are investigated to unravel a possible correlation of bioreduction phase of the experiment appeared to be relatively the biomarker increase to paleo-seepage. independent of the dominant TEA present. However, in the Furthermore, a piece of a carbonate crust, sampled from an active reoxidation phase of the experiment, the rate and degree of Cr seep in the Norwegian Sea is being analyzed to compare its biomarker composition to our previously investigated samples. remobilization was strongly influenced by the bulk redox condition history of the system. These results present an interesting contrast [1] Nickel et al. (2012) Marine Geology, in press. between those behaviors controlled by local conditions and those [2] Aloisi et al. (2002) Earth and Planetary Science Letters, controlled by bulk conditions. 203(1), 195-203.
Mineralogical Magazine | www.minersoc.org 2166 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Contrasting on- and off-axis melt Weathering in the Rhizosphere delivery: a Sr and Nd isotopic study of Analyzed with Transmission the Moho transition zone of the Oman Electron Microscopy 1 2,3 1 S.M. NIEDZIELA *, A. DOHNALKOVA , K.A. GREENBERG , ophiolite 2 1 3 B.W. AREY , Z. BALOGH-BRUNSTAD , Z. SHI , AND C. K. 3 KELLER 1 2 1 MARIE NICOLLE *, DELPHINE BOSCH , LAURIE REISBERG , 1 1 1 Hartwick College, Oneonta, NY, 13820 USA (*correspondence: DAVID JOUSSELIN AND AURORE STEPHANT [email protected]) 1Université de Lorraine, CRPG-CNRS, Vandoeuvre les Nancy, 2Environmental Molecular Sciences Laboratory, Pacific Northwest France, [email protected] (* presenting author) National Laboratory, Richland, WA, USA 2Université Montpellier 2, Géosciences Montpellier, Montpellier, 3School of the Environment, Washington State University, Pullman, France WA, USA
Recent tomographic images from the East Pacific Rise [1] Introduction and Methods indicate that nearly 50% of the melt is delivered off-axis It is generally accepted that bacteria and mycorrhizal fungi instead of beneath the ridge axis. The consequences of this enhance mineral weathering and nutrient translocation to their host process can be studied on land in the Oman ophiolite, where plants. The role of biofilm in rhizosphere (root zone), on the other structural mapping has shown the existence of both on- and hand, is not well known and poorly characterized. The goal of our off-axis melt delivery systems [2]. Off-axis diapirs impinge study was to examine the mineral-fungus-biofilm interface under directly on hydrothermally-altered lithosphere and may be conditions of calcium and potassium limitation, using transmission contaminated by this material. Petrologically, off-axis melt electron microscopy. We hypothesized that tree-fungus-bacteria delivery results in the development of an unusually thick Moho association increases biofilm formation under calcium and potassium Transition Zone (MTZ) composed largely of clinopyroxenite, limitation, and enhances mineral weathering that will be indicated by whereas on-axis MTZ contains troctolite and gabbro lenses. distinct depletion profiles of elements under fungal and biofilm cover We are analyzing the Sr and Nd isotopic compositions of [1]. pyroxenites, gabbros, diorites, and dunites, from an on-axis Red pine (Pinus resinosa Ait.) trees were grown in leach tubes (Maqsad) and an off-axis (Mansah) diapir in the Semail massif filled with quartz sand amended with 0.5 wt% biotite and 1 wt% anorthite. Half of the trees were inoculated with Suillus tomentosus of the Oman ophiolite to explore the geochemical and a group of forest soil bacteria, and the other half were left consequences of these contrasting settings. Leached and without microbial inoculation. Additional columns without any unleached whole rocks, as well as clinopyroxene (cpx) biology served as controls. Calcium and potassium were supplied in separates are being studied, to allow us to investigate both irrigation water at 0, 10, 30 and 100% of rates for healthy tree magmatic and later hydrothermal processes. Initial Nd isotopic growth. A subset of the columns were destructively sampled after compositions from unleached whole rock powders are three months. Whole mount transmission electron microscopy comparable for the two diapirs (HNd = 8.5-9.2 on-axis; HNd = (TEM) grids were prepared from root-system wash solutions used to 5.6-10.3 off-axis), although off-axis rocks display a larger collect the rhizospheric microbial community. Anorthite and biotite range of variation. In contrast, whole rock Sr isotopic ratios grains were also collected from the rhizosphere to prepare thin differ markedly, with on-axis samples displaying a limited sections using focused ion beam – scanning electron microscopy range of enriched MORB-like compositions (87Sr/86Sr = (FIB-SEM). Thin sections of the 0% treatment and a control were 0.703010 - 0.703438) whereas off-axis samples have more analyzed with high resolution TEM coupled with energy dispersive radiogenic and highly heterogeneous compositions (87Sr/86Sr = x-ray spectoscopy to test our hypothesis. Multiple chemical profiles 0.703277 - 0.706192). We attribute this difference to the were analyzed on the FIB sections under the fungal cover of anorthite presence of a magma chamber above the on-axis diapir, which and biofilm cover of biotite. protects the MTZ from the effects of hydrothermal circulation. Separated cpx and leached whole rocks from off-axis Results and Discussion pyroxenites have less radiogenic compositions (87Sr/86Sr = Whole mount TEM shows that the 0% treatment has the greatest 0.703218 - 0.703576) than the corresponding unleached whole species diversity, but all treatments have one or two types of bacteria. rocks. Nevertheless, several of these samples have 87Sr/86Sr The overall bacterial population by number is the largest in the 100% ratios that approach the upper limit of the Indian MORB field. treatment. Fungal hyphae are only oberserved with SEM. On the In outcrop, a mixing zone is observed between pyroxenites anorthite FIB sections, a slight decrease of Ca is seen under the and crustal gabbros in the MTZ overlying the off-axis diapir. fungus compared to the control. The same slight depletion is seen Samples from this mixing zone have more radiogenic cpx for K, Mg and Fe in biotite under biofilm cover, compared to the compositions than samples collected further from the Moho, control. However, these chemical profile differences between suggesting magmatic contamination of the pyroxenites by treatments and controls are not significant after 3 months reaction incorporation of hydrated material rich in seawater-derived Sr. time. Further work after 6, 9 and 12 months is planned to further
[1] Toomey et al. (2007) Nature 446, 409-414. [2] Jousselin and explore our hypothesis. Nicolas (2000) Marine Geophysical Researches 21, 243-257 [1] Bonneville et al. (2011) Geochim. Cosmochim. Acta 75, 6988- 7005.
Mineralogical Magazine | www.minersoc.org 2167 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Thermodynamic feedbacks in kinetic The geochemical behavior of thallium trace metal-calcite solid solution in mantle-derived basalts 1* 2 1 formation NIELSEN, S.G. , LEE, C.T.A. , SHIMIZU, N. 1 1* 1,2 WHOI, Dept. of Geology and Geophysics, 266 Woods Hole Rd, LAURA C. NIELSEN , DONALD DEPAOLO , JAMES J. 3 02543 Woods Hole, MA, USA, [email protected] DEYOREO 2Department of Earth Science, MS-126, Rice University, 6100 Main 1University of California-Berkeley, Berkeley, CA, USA, St., Houston, TX 77005, USA [email protected] (* presenting author) 2Center for Isotope Geochiemistry, Lawrence Berkeley National Thallium (Tl) isotopes are a new stable isotope system that Laboratory, Berkeley, CA, USA shows great potential as a tracer in igneous systems [1, 2]. One of 3The Molecular Foundry, Lawrence Berkeley National Laboratory, the main difficulties when doing any geochemical study of Tl is the Berkeley, CA, USA scarcity of knowledge about the general behavior of this element in various environments. This problem stems from the fact that Calcite precipitated from natural terrestrial fluids typically historically Earth scientists have rarely analyzed Tl. The physical and incorporates trace to mole percent amounts of impurities. The chemical properties of Tl allows for the possibility that it can act in resulting solid solutions have solubilities different from the pure four different ways, depending on the geodynamic setting: 1) phase. To understand the relationships between trace element Chalcophile, 2) Lithophile, 3) Fluid mobile, 4) Volatile. concentration and the environment of calcite precipitation, it is The few studies that have investigated Tl behavior in igneous necessary to know how thermodynamic controls on solid solution systems present somewhat conflicting evidence. McGoldrick et al. composition also affect mineral precipitation kinetics. These two [3] concluded that sulfur imparts a strong control on Tl factors together determine the solid solution composition. To concentrations in mid ocean ridge basalts (MORB), which contrasts evaluate the feedbacks between thermodynamics and kinetics we the general behavior of Tl in more evolved igneous systems, where developed a microscopic model of ion-kink attachment-detachment Tl appears to follow the alkali metals [2]. The more recent studies rates which predicts the inhibition and incorporation behaviour of present more reliable data produced with inductively coupled mass impurities, and its relationship to solution composition. spectrometers (ICP-MS), but the number of data points is either For solution supersaturations typical of biomineralizing fluids limited or lack some key complimentary geochemical data that in seawater and of most natural surface waters, ion attachment and might help reveal the processes that control the transport of Tl from detachment occur primarily at kink sites along step edges on the the mantle to the Earth’s surface [1, 2, 4, 5]. calcite surface. The net ion attachment rate is controlled by the To obtain a more complete understanding of Tl in primitive density of compatible kink sites (i.e. a carbonate site for a calcium igneous systems we will present Tl concentration data for a number ion) and by the kinetic barrier for ion attachment, which is thought to of MORB glasses, back arc lavas and melt inclusions. These data are reflect ion and kink desolvation kinetics. Ion detachment from kink complemented by concentrations of alkali metals, water, Cl and S, sites occurs when the solid-solid bonds between the ion and the which will enable us to identify if Tl changes its geochemical adjacent lattice sites are broken. Lattice strain induced by affinity in different geologic settings. incorporation of poorly fitting trace elements will speed ion detachment kinetics. Ion attachment kinetics are primarily governed [1] Nielsen, S.G., et al., Earth Planet. Sci. Lett., 2007. 264: p. 332- by solution properties, whereas ion detachment is controlled by 345. bond energetics of calcite. At equilibrium, ion attachment and [2] Nielsen, S.G., et al., Nature, 2006. 439: p. 314-317. detachment rates are equal, so the detachment frequency can be [3] McGoldrick, P.J., R.R. Keays, and B.B. Scott, Geochim. calculated from the equilibrium ion activities, which in turn are Cosmochim. Acta., 1979. 43: p. 1303-1311. dependent on the composition of the calcite. Ultimately, with some [4] Jochum, K.P. and S.P. Verma, Chem. Geol., 1996. 130: p. 289- assumptions about the form of the kinetic rate laws, we can derive a 299. model that simultaneously accounts for the trace element [5] Noll, P.D., et al., Geochim. Cosmochim. Acta., 1996. 60: p. incorporation and its effects on calcite growth rates. 587-611. Our results indicate that step velocities of strontian calcites vary non-linearly with aqueous Sr concentration due to the effect of lattice strain on Ca detachment kinetics. The growth rate of Mg- bearing calcite with increasing aqueous Mg, on the other hand, is inhibited primarily by kink blocking, and Mg incorporation is typically controlled by the relative rates of Ca and Mg desolvation. This suggests that the Mg isotopic composition may similarly be controlled by dehydration kinetics. This model can be used to constrain the composition of fluid from which a given calcite precipitated.
Mineralogical Magazine | www.minersoc.org 2168 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts U–Pb isotopic systematics on shock- Rapid reductions in North Atlantic metamorphosed baddeleyite Deep Water during the last
1,2,3 interglacial period and their TAKAFUMI NIIHARA * relationship to Greenland ice sheet 1Center for Lunar Science and Exploration, Lunar and Planetary variability Institute, Houston, Texas 77058, USA. [email protected] (* 1* 2 3 ULYSSES NINNEMANN , EIRIK GALAASEN , NIL IRVALI , presenting author) 4 5 6 HELGA KLEIVEN , YAIR ROSENTHAL , CATHERINE KISSEL 2Antarctic Meteorite Research Center, National Institute of Polar 1 Research, Japan University of Bergen and Uni Bjerknes Centre, Norway, 3Dept. of Polar Science, SOKENDAI, Japan [email protected] (* presenting author) 2University of Bergen, Norway, [email protected] The issue of the duration of Martian magmatic activity is one 3Uni Bjerknes Centre and University of Bergen, Norway, the controversial debates recently [e.g. 1]. The young radiometric [email protected] ages of ~180 Ma for shergottites, a class of Martian meteorites, 4 University of Bergen and Uni Bjerknes Centre, Norway, reflect the timing of crystallization from a magma or rather later events related to shock metamorphism or fluid infiltration. [email protected] 5Rutgers University, USA, [email protected] Baddeleyite (ZrO2) occurs as an accessory mineral in Martian meteorite and is useful for U–Pb isotopic analyses as well as zircon 6 Laboratoire des Sciences du Climat et de l'Environnement/IPSL, (ZrSiO4) [e.g. 2-4]. Martian meteorites contain varied shock effects; France, [email protected] however, there are no available data on the effect of high- pressure/temperateure lead or uranium diffusivities in baddeleyite. One uncertainty in future climate and CO2 projections involves To examine whether the U–Pb isotopic systems of baddeleyite are changes in the Atlantic meridional overturning circulation (AMOC) easily reset by shock metamorphism, our group have undertaken and its response to climate change. Models and proxy data suggest shock-recovery and annealing experiments using a propellant gun at NIMS and a vertical gas-mixing furnace and at Univ. of Tokyo, that AMOC is vigorous under interglacial climate conditions with respectively [5]. minor changes on millennial timescales. Yet, with the exception of High-shock pressure slightly caused damages on baddeleyite the notable changes associated with the 8.4 kyr BP flood outburst, crystal structures. The brightness of Cathode Luminescence little is known about the stability or thresholds of deep ocean emission increased with the shock pressure of up to 57 GPa. circulation on shorter timescales. Here we use deep-sea sediment Annealed sample did not show any detectable change from pre- cores to assess the response of North Atlantic Deep Water annealing sample (shocked at 47 GPa sample). In addition, Raman −1 (NADW), the main constituent of the deep limb of AMOC, to peak shifts of 2-4 cm from unshocked baddeleyite were observed associate with shock pressures. Those peak shifts were reported on source region warming, Greenland ice sheet (GIS) melting, and high pressure static experiments [6]. However, there is no evidence ocean freshening. on phase transformation from baddeleyite to high-pressure and We present new high-resolution (~20 yr/sample) foraminiferal temperature phases [5]. G13C and G18O records of near surface and bottom water properties Lead loss from baddeleyite was not observed for the spanning MIS 5e from a core site on the Eirik Drift south of experimentally shocked samples. In addition, the U–Pb and 206Pb– Greenland (MD03-2664). The site lies at 3440m, just below the 207Pb ages of shocked and heated baddeleyites are indistinguishable from those of unshocked baddeleyite within errors except minor main axis of the sediment-laden Western Boundary Undercurrent lead loss from the baddeleyite shocked at 57 GPa and heated 1 h at and is optimally situated for recording changes in newly formed 1300 oC. Although duration of peak shock-pressure and grain size of NADW. In addition, we use ice rafted detritus (IRD) and baddeleyite are different from the nature of shock events, our foraminifera-based surface property proxies (G18O, MAT-SST’s, experimental results suggest that it is hard to completely reset U–Pb Mg/Ca) to assess changes in the GIS and Arctic to North Atlantic isotopic systematics of baddeleyite by shock metamorphism. freshwater transport. In some terrestrial crater, occurrences of some baddeleyite 13 grains are explained as breakdown products from zircon to Bottom water G C values gradually increase through MIS 5e. baddeleyite and silica (ZrSiO4ÆZrO2+SiO2) by shock effects. The Superimposed on this trend are large-amplitude (>1‰) reductions in baddeleyite grains in RBT 04261, shergottites, do not associate with bottom water G13C, similar in scale to those observed during the 8.4 zircon or silica materials and no signature of Raman peak shift; it kyr BP event. These G13C decreases last a few centuries before imply that grains are not breakdown products from zircon and not recovering to background values. Using an array of records spanning affected by shock pressure so much. Three large grains (~10 μm) are the abyssal Atlantic we show that the magnitude and spatial geometry found for isotopic analyses, two grains occurred with ilmenite and one grain found in melt pocket. U–Pb age of ~200 Ma was obtained of the deep water anomalies is consistent with an expansion of from these grains although the grain sizes are still slightly smaller southern source deep water as the influence of NADW waned—a than primary ion beam of SHRIMP, and may imply the magmatic geometry analogous to deep ocean changes during the 8.4 kyr BP activity on Mars [4]. event and to millennial scale events of the last glaciation. Surface water proxies and IRD content suggest that these NADW changes [1] Bouvier et al. (2005) Earth. Planet. Sci. Lett. 240, 221–233. occur during a period of rapid GIS retreat and surface water [2] Herd et al. (2007) Lunar Planet. Sci.38, Abstract 1664. freshening. Taken together, our results demonstrate that “8.4kyr- [3] Misawa and Yamaguchi (2007) Meteorit. Planet. Sci. 42, A108. [4] Niihara (2011) Jour. Geophis. Res. 116, E12008 style” deep ocean property changes occurred at a time when North [5] Niihara et al. (2012) submitted for EPSL. Atlantic climate was similar to that projected for our future. [6] Bouvier et al. (2002) Jour. Nucl. Material. 300, 118–126.
Mineralogical Magazine | www.minersoc.org 2169 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Deformation experiments of mantle Formation condition of mono- materials at the conditions of deep hydrocalcite from Ca-Mg-CO3 Earth interior solutions 1* 1* 2 YU NISHIHARA RISA NISHIYAMA , TAKASHI MUNEMOTO , AND KEISUKE 1 FUKUSHI 1Ehime Universtiy, Senior Research Fellow Center and Geodynamics Research Center, [email protected] 1 Kanazawa University, Ishikawa, Japan, [email protected] (* presenting author) Introduction 2 The University of Tokyo, Tokyo, Japan, Knowledge on rheology of mantle materials is indispensable in understanding thermal evolution and material transport in the Earth. Monohydrocalcite (CaCO3·H2O: MHC) is rare mineral in Since rheological properties strongly depend on temperature and geological settings. MHC has been most frequently found in the recent sediment in saline lakes [1]. It also was found from the pressure, it is critacally important to conduct deformation calcareous sinter of cold spring of Shiowakka, Hokkaido, Japan [2]. experiments at P-T conditions corresponding to the deep mantle for A lot of kinds of calcium carbonate minerals, including calcite, accurate understanding of Earth’s interior. Recently, quantitative vaterite, ikaite and MHC, were also occurred in Shiowakka. MHC rheological measurements at relatively high pressures (up to 10–20 occurred in only summer season and frequently associated with GPa) and high temperatures (up to 1000–2000 K) are possible by green algae. In order to understand the preferential formation of using large-volume presses in conjunction with synchrotron MHC with green algae, we conducted synthesis experiments of radiation. In this presentation, our recent results on rhelogy under carbonate minerals from various concentrations of Ca, Mg and CO3 to clarify the formation condition of MHC. Earth’s deep mantle conditions determined by deformation The mixing solutions containing CaCl2 and MgCl2 was prepared experiments using deformation-DIA appratus are discussed. in the reaction vessels, and Na2CO3 solution was added to 50mL of Mechanical property of fine-grained forsterite the mixing solutions. The initial concentrations of Ca, Mg and CO3 In order to understand mechanical behavior in grain-size- in the solutions were 0.025~0.1M, 0~0.05M and 0.03~0.1M, seisitive creep in the deep upper mantle condition, deformation respectively. Immediately after Na2CO3 solutions were added to the experiments on dry fine-grained (grain size of ~1 Pm) forsterite solution, the whitish suspensions were formed in the reaction were performed at P = 3–5 GPa, T = 1473–1573 K and strain rate of vessels. The syntheses experiments were conducted in closed polycarbonate vessels at 25 °C, and the resulting suspension was 9 × 10–6–2 × 10–4 s–1 [1]. The stress-strain rate data together with constantly stirred and aged with mix-rotor for 24 h. After the aging data at 0.1–300 MPa by Tasaka et al. (unpublished data) were time, the suspensions were filtered. The solids were analyzed by X- analyzed using a flow law equation for diffusion creep (n = 1, p = 2) ray diffraction and examined by scanning electron microscope. The and dislocation creep accommodated grain-boundary sliding (GBS, n filtrates were analyzed for the concentration of CO3 by alkalinity = 3.5, p = 2). Based on the analysis, the activation volume both for titration. The Ca, Mg and Na concentrations of filtrates were measured by high-performance liquid chromatography. diffusion creep (V*dif) and GBS (V*GBS) of olivine was determined to 3 Four mineral assemblages were obtained from all of the be ~8 cm /mol. Calculation based on the present results implies that experimental conditions from the XRD results. They are mixture of typical mantle deformation conditions are close to the mechanism vaterite and calcite, mixture of aragonite and calcite, MHC and boundary between the diffusion creep and the GBS. amorphous material. Based on the observations, the formation Mechanical property of wadsleyite conditions of MHC can be summarized that the initial Mg Uniaxial deformation experiments on wadsleyite were carried concentration is more than 0.01 M and the CO3/Ca ratio of the out at P = 14–16 GPa and T = 1500–1700 K with strain rates of initial solutions are more than 1. The IAP of the reacted solutions –5 –1 with MHC formations were greatly higher than anhydrus calcium 3.4–15 × 10 s [2]. Results suggest that flow strength of 2+ 2- carbonates. The activity of Ca is lower than that of CO3 when wadsleyite is more sensitive to water content than that of olivine. 2+ 2- MHC was formed. Furthermore, the activities of Mg and CO3 in Lattice preferred orientation (LPO) of olivine the solution after MHC and amorphous material formation were The effects of hydrogen and pressure on LPO of olivine were almost equilibrium with respect to nesquehonite. By integrating the investigated through simple-shear deformation experiments under formation conditions of MHC from both initial solution and reacted asthenospheric upper mantle conditions (P = 2.1−5.2 GPa, T = solution, we considered that MHC formation requires simultaneous 1490−1830 K) [3,4]. Formation of the A-type olivine fabric formation of magnesium carbonate (nesquehonite), i.e., the 2- developed by the (010)[100] slip system was observed under water- concentration of CO3 in the solution must be high enough to produce both MHC and magnesium carbonate. depleted (C < 650 H/106Si in olivine), while B-type fabrics by the OH In Shiowakka, the pH increase by photosynthesis of green algae. (010)[001] slip system (or B-typre like fabric) were predominantly 2- The local concentration of CO3 near the green algae must increase 6 2- - formed under water-rich conditions (>1000 H/10 Si). The water- drastically. Inclease of the cintribution of CO3 to HCO3 enables to induced olivine LPO transition from A-type to B-type (-like) fabric the formation magnesium carbonate even spontaneously with MHC results in flow-parallel and flow-perpendicular shear wave splitting formation. Thus, the MHC is selectively formed in summer season under water-depleted and water-rich conditions, respectively. associated with green algae.
[1] Nishihara et al. (2011) Abstract MR11A-2170 presented at 2011 [1] Fukushi et al. (2011) Sci. Technol. Adv. Mater, 12, 064702. Fall Meeting, AGU. [2] Kawazoe et al. (2011) A. Mineral.96, 1665- [2] Ito (1993) Ganko, 88, 485-491. 1672. [3] Ohuchi et al. (2011) Earth Planet. Sci. Lett. 304, 55-63. [4] Ohuchi et al. (2011) Earth Planet. Sci. Lett. 317-318, 111-119.
Mineralogical Magazine | www.minersoc.org 2170 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Preliminary Pb and Pb isotopes from Isotopic Variability of the Ninetyeast the US GEOTRACES North Atlantic Ridge Implications for its Mantle Transect Sources 1* 2 1 1 ABIGAIL E. NOBLE , YOLANDA ECHEGOYEN-SANZ , AND ED INÊS G. NOBRE SILVA *, DOMINIQUE WEIS , JAMES S. 3 1 2 2 BOYLE SCOATES , MALCOLM S. PRINGLE AND FRED A. FREY 1Massachusetts Institute of Technology, Cambridge, USA 1Pacific Centre for Isotopic and Geochemical Research, Earth & [email protected] (* presenting author) Ocean Sciences, Univ. of British Columbia, Vancouver, BC 2Universidad de Zaragoza, Zaragoza, Spain, V6T 1Z4, Canada, [email protected] (* presenting author) [email protected] 2EAPS, MIT, Cambridge MA 02139 USA. 3 Massachusetts Institute of Technology, Cambridge, USA, [email protected] The ~5000 km long north-south oriented Ninetyeast Ridge in the eastern Indian Ocean Basin represents the age progressive, ~80 This study presents preliminary Pb and Pb isotope data from the to ~40 Ma products of the 120 Ma old Kerguelen mantle plume. US GEOTRACES North Atlantic Transect which was sampled during Basaltic basement samples recovered during DSDP and ODP drilling two cruises that took place during the Fall of 2011 and 2012. campaigns are however scarce and debate concerning the nature and Almost all of the Pb found in the modern ocean is derived from number of components in the mantle source of the Ninetyeast Ridge anthropogenic sources, and the North Atlantic has received persists. Dredging during a National Science Foundation-funded significant Pb inputs from the United States and Europe due to emissions from leaded gasoline and high temperature industrial 2007 cruise recovered basaltic basement from 21 locations along processes. During the past three decades, Pb fluxes to the North ~3200 km of the ridge. New high-precision isotopic compositions Atlantic have decreased following the phasing out of leaded gasoline by MC-ICP-MS (Pb, Hf, and Nd) and TIMS (Sr) were obtained on 59 in the United States and Europe. Following the concentrations and basaltic samples from 21 dredges. Sample choice was based on the isotope ratios of Pb in this basin over time reveals the temporal lowest degree of alteration (lowest LOI), high Mg#, and variable evolution of Pb in this highly- affected basin. This cruise included a trace element ratios (e.g., Zr/Nb, Y/Nb, La/Sm). Altogether these re-occupation of the Bermuda Atlantic Time Series station (BATS) samples cover a greater range of Pb-Sr-Nd-Hf isotopic that was one of 8 occupations since 1979 for Pb and one of 6 for Pb compositions and wider within-site isotopic variability than that isotopes at approximately 5-year intervals,. Two stations in the covered by the drilled samples recovered during ODP Leg 121, and Eastern North Atlantic were previously occupied in 1989, 1999, and are generally intermediate between those of the volcanic products of the data from this expedition provide some comparison of the the Kerguelen and Amsterdam-St. Paul mantle plumes. This attests temporal evolution of Pb in this region. The Pb isotope signatures to a compositionally heterogeneous mantle source, and at least reflect the relative importance of inputs from the United States and Europe as leaded gasoline was phased out faster in the United States three, possibly four, distinct source components with relatively relative to Europe. This is observed in a surface trend towards enriched and depleted signatures are required to explain the slightly lower 206Pb / 207Pb ratios in the last decade. Pb observed isotopic variability along the Ninetyeast Ridge. Mixing concentrations decrease with time in the upper water column with shallow level Indian MORB does not account for the lower (<2000m) with higher concentrations observed in mid-latitude 87Sr/86Sr and higher Nd and Hf isotopic ratios of basalts from some northern stations decreasing southward at the eastern end of the of the dredges (i.e., 87Sr/86Sr 0.70369-0.70428, 143Nd/144Nd > basin. Concentrations and isotopes converge in deep waters with 0.51300 and 176Hf/177Hf > 0.28322 for 5 samples from 2 dredges). longer residence times. Further results from the section will be These depleted signatures are instead consistent with the presence presented as data become available. of a previously depleted, garnet-enriched component intrinsic to
their deep mantle source that had been identified based on
incompatible trace element abundances alone. Together with other
Indian Ocean island basalts of typical EM-1-like compositions, the Pb-Hf-Sr-Nd isotopic compositions of the Ninetyeast Ridge basalts are consistent with provenance from a deep mantle source that has incorporated a mixture of recycled sediments and lower continental crust together with altered oceanic crust. This supports a deep origin for the EM-1-like Dupal signatures encountered in ocean island basalts.
Mineralogical Magazine | www.minersoc.org 2171 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Boron incorporation in synthetic As, Sb, Mo, V, W, and Se oxyanions calcite and aragonite revealed by B in Yellowstone’s thermal waters 11 1* 2 isotopes and B MAS NMR D. KIRK NORDSTROM AND R. BLAINE MCCLESKEY
1* 2 1 JOHANNA NOIREAUX , VASSILEIOS MAVROMATIS , JEROME US Geological Survey, Boulder, USA, [email protected] (* presenting 1 2 1 GAILLARDET , JACQUES SCHOTT , PASCALE LOUVAT AND author) 3 2 VALERIE MONTOUILLOUT US Geological Survey, Boulder, USA
1 Laboratoire de Géochimie et Cosmochimie, Institut de Physique du Concentrations of As, Sb, Mo, V, W, and Se have been determined in Globe de Paris, Paris, France, [email protected] (* presenting hundreds of water samples from thermal features in Yellowstone author) National Park and from the Firehole and Gibbon River systems. 2Geosciences Environnement Toulouse, Université Paul Sabatier, Analytical methods include ICP-AES, ICP-MS, HGAAS, and Toulouse, France, [email protected] GFAAS. Selenium is consistently less than 1 ȝJ/HYHU\ZKHUH9LV RIWHQEHORZGHWHFWLRQXSWRȝJ/0RRFFXUVXSWRȝJ/6E 3CNRS-CEMHTI, Orléans, France, valerie.montouillout@cnrs- XSWRȝJ/DQG$VXSWRȝJ/ Concentrations of W are orleans.fr limited but generally similar to or a bit higher than those of Sb and Mo. Arsenic concentrations are typically 0.5 to 3 mg/L but they are Boron isotopes measurements in marine carbonates are used as a highest in Norris Geyser Basin waters, especially in the western part proxy of the paleo-pH of the oceans. The reliability of these pH of the basin. This area seems to have accumulated arsenic through reconstructions lies in our understanding of the mechanisms of boron precipitation of considerable orpiment and realgar at low pH at or incorporation in carbonates. The paleo-pH calculations are based on just below the ground surface. One pair of springs demonstrate the assumption that one of the two boron species in solution (borate - remarkable mixing between two end-member compositions, a near B(OH)4 ) is preferentially incorporated in calcium carbonates [1],[2]. neutral pH high-As and high-Cl water and a low-As, low-Cl acid Experiments show that there is a shift between expected and 11 water. This range of composition can explain the variable water measured boron isotopic ratios (δ B) at a given pH, which is compositions for many waters occurring in Norris Basin. Most attributed to the specifics of boron incorporation in biological waters exhibit a linear relation of As concentrations relative to Cl organisms ("vital effect"). concentrations suggesting that arsenic is largely conservative and In order to better understand the mechanisms of boron tends to stay with the aqueous fluid during boiling and dilution. incorporation in carbonates and by comparison, the modifications More surprising, arsenic concentrations are not attenuated during 20- induced by vital effects, we carried out inorganic precipitation experiments of calcite and aragonite in NaCl solutions of wide- 30 miles of river drainage. The Gibbon River maintains more than ranging pH values and at temperatures of 25°C and 5°C. Boron 100 ȝJ/ dissolved As and the Firehole River increases to more than isotopic compositions of the carbonates were then measured by MC- 400 ȝJ/ in the lower reaches. The most likely hypothesis is that the ICP-MS and the proportions of trigonal and tetragonal B by 11B MAS high silica concentrations in the thermal waters precipitate in the NMR. river and coat the river bed sediments, decreasing its sorption Our results confirm that the boron isotopic ratio of the carbonates capacity. There is also very little Fe in the overflows. is dependent upon the growth solution pH, but also upon crystal type A complicating factor for speciation of As, Sb, Mo, and W is the and temperature. In calcite, both NMR and boron isotopic formation of thio-complexes which have been explored for As and Sb composition show that boron incorporation is not consistent with the but not for Mo and W. Such complexes may help to explain their - single incorporation of the aqueous borate species B(OH)4 . mobility under reducing conditions. Moreover, the NMR measurements show that the proportion of Concentrations of Sb and Mo tend to track with As, with the trigonal boron (BO3) in calcite is higher than what is inferred from highest concentrations occurring with the highest Cl concentrations the isotopic signal by assuming that both boron aqueous species are but there is much more scatter in the data. For the Gibbon and incorporated in the carbonate. In aragonite, BO3 is present in smaller Firehole Rivers, Sb and Mo concentration profiles are strikingly proportions depending on pH and both NMR measurements and δ11B similar showing no attenuation. One anomaly occurs in the Gibbon are in good agreement with the hypothesis of the preferential River profile. A substantial inflow of Mo enters from Terrace Spring incorporation of the borate species in calcium carbonates . just before the convergence of the Gibbon with the Firehole. These trace elements are indicative of the deep geothermal reservoir [1] Hemming and Hanson (1992) Geochim et Cosmochim Acta 56, composition and not greatly affected during transport to the surface. 537-543. [2] Vengosh et al. (1991) Geochim et Cosmochim Acta 55, Concentrations of V behave very differently from the other 2901-2910. oxyanions; they are below 10 ȝJ/ for nearly all Cl concentrations above 200 mg/L. Higher concentrations are only found in acid waters of low Cl concentration, regardless of temperature. These results suggest that V is dominantly derived from acid weathering of near surface rocks. Furthermore, V is the element in this group that forms a cation under reduced conditions which also helps to explain its higher concentration in acidic waters. Both similar and dissimilar trends in these trace elements can be demonstrated. The biggest dissimilarity is the lack of any correlation for V with the other elements. The other elements generally behave similarly with the exception of some local anomalies. When thermal overflows enter river systems there is little to no attenuation likely because of continual silica precipitation and the lack of hydrated iron oxides.
Mineralogical Magazine | www.minersoc.org 2172 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Natural pyrite weathering rate in a Geochemical signatures of IOCG small catchment compared with mineralization and alteration in till mined catchments and lab rates 1* 2 1* PHILIPPE X. NORMANDEAU , ISABELLE MCMARTIN , JEANNE D. KIRK NORDSTROM 1 2 PAQUETTE , LOUISE CORRIVEAU AND JEAN-FRANÇOIS 1 3 US Geological Survey, Boulder, USA, [email protected] (* presenting MONTREAUIL author) 1Dept. of Earth and Planetary Sciences, McGill University, As part of the USGS background study of the Questa mine in Montreal, Quebec, Canada [email protected] northern New Mexico, a small catchment (Straight Creek) of about (*presenting author), [email protected] 2.67 km2, was studied to determine the hydrogeochemical processes 2Geological Survey of Canada, Natural Resources Canada, Ottawa, that naturally generate acidic, metal-rich surface waters and Ontario, Canada, [email protected], groundwaters. The predominant reaction is pyrite oxidation because [email protected] there is excess pyrite (2-10 wt.%) in quartz-sericite alteration. A 3INRS-ETE, Québec, Canada, [email protected] mass–balance calculation was performed reacting pure water to the
median composition of 14 water analyses from 2000-2003 with median pH of 2.98 and median sulfate concentration of 2,030 mg/L. Introduction The most likely mass–balance model consistent with mineralogical As part of Canada’s Geomapping for Energy and Minerals analyses, assuming that rates are unaffected by solid/solution ratio or (GEM) Program, an applied Quaternary research activity under the by evaporation, indicates oxidative dissolution of 8.66 mmol IOCG-Great Bear Project was undertaken in the Great Bear pyrite/kgH O. When combined with a median discharge of 37.85 2 magmatic zone (Northwest Territories, Canada) to provide a L/min measured simultaneously, the weathering rate was 5.46 mmol practical guide for geochemical and indicator mineral exploration pyrite/h. This value is larger than batch abiotic laboratory rates, targeting iron oxide copper-gold (IOCG) and affiliated deposits in about 0.01 mmol/h for Fe(III) oxidation with pH close to 2, or glaciated terrain. Detailed till sampling (n=111) was completed in microbial laboratory rates, about 0.22 mmol/h based on an interlab comparison. Evaporation effects or a “pooling effect” might be the the vicinity of the NICO Au- Co-Bi-Cu magnetite-group IOCG main sources of discrepancy between apparent field rates based on deposit as well as the Sue-Dianne Cu-Ag-Au magnetite- to hematite- mass balances and laboratory rates. Similar calculations for effluent group IOCG deposit, and near showings hosted within other IOCG- water at the Leviathan Mine, CA (pH = 1.8) result in an apparent type alteration systems in the GBmz. Samples were collected up-ice, pyrite weathering rate of 40 mmol/h, 200 times higher than expected proximal to, and down-ice from mineralization, hydrothermally- from laboratory rates; this result could be explained by the extremely altered host rocks and least-altered bedrock. Extensive fine-grained pyrite that occurs there as well as evaporation effects. Calculations for Iron Mountain, CA a massive sulphide copper lihogeochemical data set (n=1243) was available within the IOCG- deposit that has been extensively mined and exposed to air and Great Bear Project. water, result in an apparent pyrite weathering rate of 17,100 mol/h, five orders of magnitude higher than laboratory rates. At Iron Results and conclusion Mountain pyrite weathering has produced enormous amounts of Lithogeochemical signatures of mineralization and/or alteration efflorescent salts that periodically dissolve and reprecipitate in the are reflected in the till matrix (K, Na, Ca, Mg, Ti, Cu, Ba, Cr, Co, Th, underground workings. When the mass–balance is modified in terms of dissolving soluble salts, removal of some iron as goethite is Bi, Mo, U, As) despite variable degrees of post-glacial weathering required and the weathering rate becomes 24,800 moles soluble and textural differences. Possible IOCG deposit pathfinder elements sulfates/h. in till (<2 and/or <63 μm fraction) include Cu, Mo, Bi and Co Regardless of how mass–balances are calculated, the field rate (enrichments), as well as Ti (depletion). However, given the high for pyrite oxidation is much faster than the laboratory rate suggesting variability of IOCG and affiliated mineralization, a multivariate that evaporation, pooling, or possibly surface areas, strongly statistical approach was also applied to see if their associated, and influence these calculations for most mined sites. The pyrite weathering rate might be a guide to whether the mechanism is more characteristic, alteration types left a clear signal. A principal dominated by pyrite weathering or by precipitation/dissolution of component analysis (PCA) was performed on combined data sets of soluble salts. Another conclusion dictated by the mass balance is that till geochemistry and lithogeochemistry. This innovative approach large amounts of iron and silica must precipitate. This conclusion is helps to isolate the role of hydrothermal processes from surface also supported by the saturation indices having reached saturation for processes such as glacial communition and post glacial weathering silica in many of these waters. in the internal variability of the till geochemistry. Results so far show: 1) grouping of till samples by the first 3 principal components, based on their related IOCG showings; 2) discrimination between anomalous till samples based on multi- enrichments of alteration related elements (K, Ca, Na), and 3) potential to identify the type of bedrock IOCG alteration in overlying till samples.
Mineralogical Magazine | www.minersoc.org 2173 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Understanding biogeochemical Conservative behavior of Uranium vs. mechanisms for heavy metal removal salinity in sea ice and brine
1 *, 2 3 in SuDS CHRISTELLE NOT KRISTINA BROWN , BASSAM GHALEB 4 1* 2 3 AND CLAUDE HILLAIRE-MARCEL M. J. NORRIS , H. L. HAYNES , C. C. DOREA , 1 1 I.D. PULFORD , AND V.R. PHOENIX 1GEOTOP-UQAM, Montréal, Canada and AORI-Tokyo University, Kashiwa, Japan, [email protected] (* presenting 1University of Glasgow College of Science and Engineering, author) Glasgow, Scotland G12 8QQ (* [email protected]) 2University of British Columbia, Department of Earth and Ocean 2Heriot-Watt University Institute for Infrastructure & Environment, Sciences, Vancouver, Canada, [email protected] Edinburgh, Scotland EH14 4AS 3GEOTOP-UQAM, Montréal, Canada, [email protected] 3Université Laval Département de génie civil et génie des eaux, 4GEOTOP-UQAM, Montréal, Canada, hillaire- Québec, QC, Canada G1V 0A6 [email protected]
With urbanization on the rise, there has become a growing need
for sustainable approaches to cope with increased pollutant load and Since studies by Ku et al [1] and Chen et al [2], it is widely reduced land available for stormwater infiltration. A type of accepted that uranium (U) behaves conservatively with respect to Sustainable urban Drainage System (SuDS) of particular interest is a salinity (S) in seawater over the salinty range of 30 to 36. However, filter drain, which utilizes gravel media to filter and treat road runoff in low salinity environments, such as estuaries, its behavior seems laden with pollutants. While the simple concept is known to remove more variable. Freezing in the Arctic Ocean provides a natural suspended solids and heavy metals typical in road runoff, the design mechanism to concentrate dissovled seawater constituants into high of such systems is based on limited scientific input. This study aims salinitity brine through the formation of sea ice, and reintroduce low to characterize the biogeochemical mechanisms responsible for salinity water to the surface through melt. pollutant removal, specifically heavy metals, to help improve design Here we compare U concentration and isotopic composition and efficiency in SuDS systems. from samples of low-salinity sea ice, underlying surface seawater, While metal immobilization in filter drains may be biologically and high salinity brine, covering a salinity range of 0 to 135. Based mediated and a subject of future research, initial experimentation on these samples, we found that U behaves conservatively across a explored removal processes by the gravel itself and with the addition wide salinity range, producing a U-S relationship slightly different of a mineral amendment. Enhancing heavy metal removal with an than the one described in previous studies [1] (Figure 1). The iron oxide coating has been explored due to the the vast literature isotopic ratio 234U/238U from melted sea ice, under-ice seawater, evidence of iron oxide minerals sequestering metals [1]. Kinetic and sea ice brine samples were not statisically different from mean batch and flow-through column experiments demonstrated that an ocean values, within our statistical uncertainties. iron oxide coated gravel removed similar concentrations of zinc to a
locally sourced uncoated microgabbro gravel. Since coated gravel
also buffered solution pH away from neutral, it was concluded that
the difficult, costly coating process would not be suitable for use in
an environmental setting.
Specifically, kinetic batch experiments showed typical
adsorption curves and removal rates of zinc by uncoated
microgabbro at 80% removal up to 8 hours and nearly 100% after 48
hours. Whereas other types of gravel such as dolomite, sandstone
and granite removed between 10-50% less zinc overall than
microgabbro. Scanning electron microscope (SEM) images of
microgabbro show a rough, high surface area and mineral
components of microgabbro have the ability to weather to clay
minerals, which also have a high affinity for heavy metals. Further
experimentation has proven the weathered surface in fact accelerates Figure 1: U-Salinity relationship in sea ice, surface sea water, and zinc immobilization by about 20% compared to an unweathered brine samples [3]. surface.
The SuDS Manual, which is used in construction and design of
new SuDS systems, indicates that filter drain material should be a [1] Ku et al (1977) Deep-sea Res. 24, 1005-1017. [2] Chen et al locally sourced graded stone/rock [2]. While this implies that the (1986) Earth Planet. Sci. Lett. 80, 241-251. [3] Not et al (2012) geology of the type of rock utilized in such systems does not affect Marine Chem. 130-131, 33-39. pollutant removal mechanisms, kinetic batch experiments of different rock types indicates otherwise.
[1] Benjamin et al. (1996) Wat. Res 30, 2609-2620. [2] Woods- Ballard et al. (2007) The SuDS Manual 241-249.
Mineralogical Magazine | www.minersoc.org 2174 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Nitrogen mobility in freshwater peat Development of a process-based 1* 1 MARTIN NOVAK , IVANA JACKOVA , FRANTISEK chemical weathering model with 1 1 BUZEK , LUCIE ERBANOVA AND MARKETA 1 consideration of the effective surface STEPANOVA area 1 Czech Geological Survey, Prague, Czech Republic, 1* 1,2 [email protected] (* presenting author), TAICHI NOZU AND EIICHI TAJIKA [email protected], [email protected], 1The University of Tokyo, Earth and Planetary Science, [email protected], [email protected] [email protected] (* presenting author)
2The University of Tokyo, Complexity Science and Engineering, Peatlands cover less than 5 % of the Earth's land surface, yet [email protected] they store as much as 15 % of the world's soil N, and 30 % of the 210 world's soil C. Vile et al. [1] have recently reported that Pb dated Feedback mechanism between climate and chemical weathering peat in pristine high-latitude bogs contains 20 times more N than is one of the most important aspects of the Earth system. Despite a could be explained by inputs of atmospheric N. Vile et al. [1] have significant number of studies for understanding the rate of chemical suggested that the "excess" N in peat is a result of in-situ N2 fixation weathering quantitatively by observational, experimental, and from cyanobacteria, a process that has been largely overlooked. It is numerical methods, the global chemical weathering rate has not been unclear whether in N-polluted areas, where N is not a limiting estimated straightforwardly owing to a significant discrepancy nutrient, the symbiosis between Sphagnum and N-fixing between field and laboratory studies. The discrepancy may be microorganisms is lost. Still, it appears that a major gap in the global explained as a sum effect of several phenomena such as increase in biogeochemical cycling of N has been identified. surface roughness with time and difference in reaction affinities Here we report a field experiment that might provide an insight between natural and experimental conditions [1]. into the retention of atmogenic N in peat. We hypothesized that We are developing a process-based chemical weathering model vertical N profiles in peat do not directly reflect historical trends in to study behaviours of the geochemical cycle system in response to N deposition and that N is mobile after its burial in peat. We changes in modern- and palaeo-environment. This model is similar selected two Central European peat bogs, differing in present-day to “WITCH” model [2], but the originality of our approach lies on atmospheric N inputs by a factor of 2, and collected 10 peat cores integration of simple soil physics (i.e. heat and moisture transport) per site. Trends in N deposition since the beginning of the Industrial and consideration of soil biological activity in the weathering model. Revolution have been extremely well documented in the area [2]. The model has been applied to different small (< 10 km2) watersheds The more polluted site VJ exhibited a clear-cut N concentration such as Strengbach in France and Lac Clair in Canada to verify the peak in layers dating from 1950. The less polluted site CB showed a model to reproduce major ion concentrations of modern streams. We N concentration minimum in layers dating from 1940. In actual fact, introduced a free parameter which represents a ratio of field-scale the atmospheric N input increased smoothly until 1980, and dropped weathering rate to mineralogical dissolution rate to fit the results to thereafter [2]. We suggest that N in peat profiles does not record the observational data. Sensitivity analyses show that riverine ionic past N deposition levels. We conducted an 18-month reciprocal peat concentrations of base cations are well reproduced from the model transplant experiment between VJ and CB, using 5 cores as only by tuning this parameter alone. We interpret that this parameter transplants and 5 cores as controls per site. At the end of the may represent the erosional effect which, in turn, controls the age of experiment, at both sites, bulk N to a depth of 10 cm changed its the weathering environment. That is, the time dependency of silicate 15 δ N value by 3 per mil, converging to that of the host site. Again, weathering [1] can explain the difference in this parameter. The the bulk N isotope change indicated a measurable degree of N obtained parameter is also comparable with the ratio of the effective mobility in peat. surface area to the BET surface area estimated in previous studies. Our results imply that the chemical weathering process can be modelled by considering the difference in the effective surface area [1] Vile et al. (2011) Proceedings of AGU Annual Meeting, San controlled by lithology and erosion. Francisco, December 2011. [2] Kopacek et al. (2011) Global Biogeochem. Cycles 25, GB2017. [1] White & Brantley (2003) Chem. Geol. 202, 479-506. [2] Goddéris et al. (2006) Geochim. Cosmochim. Acta 70, 1128-1147.
Mineralogical Magazine | www.minersoc.org 2175 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts
The unique biogeochemical signature Zooming on Heinrich layers H2 of the marine diazotroph to H0 through geochemical and Trichodesmium 1* 2 3 sedimentological analysis of a JOCHEN NUESTER , STEFAN VOGT , MATT NEWILLE , ADAM 4 5 KUSTKA , BENJAMIN S. TWINING core raised off Hudson Strait 1 1 1Bigelow Laboratory for Ocean Sciences, W. Boothbay Harbor, ME, LAURENCE NUTTIN AND CLAUDE HILLAIRE-MARCEL USA, [email protected] (*presenting author) 2 X-ray Science Division, Advanced Photon Source, Argonne 1GEOTOP-UQAM, Montréal, Canada, [email protected] National Laboratory, Argonne, IL, USA, [email protected] 3Center for Advanced Radiation Sources, The University of Chicago, The ~ 9 m-long core (HU08-029-004; 2674 m water- Argonne, IL, USA, [email protected] 4Rutgers University – Newark, Earth and Environmental Sciences, depth; 61°27'N, 58°2'W) was raised from the lower slope of Newark, NJ, USA, [email protected] the Labrador Sea, approximately 100 nm off the Hudson 5Bigelow Laboratory for Ocean Sciences, W. Boothbay Harbor, ME, Strait shelf edge. It provides a high resolution record of USA, [email protected] recent detrital carbonate sedimentary pulses through Hudson Strait assigned to "Heinrich events" H2, H1, H0, thus the Trichodesmium is a globally important nitrogen-fixing, filamentous means to constrain the age and depositional mechanism of cyanobacterium. In the present study, we collected Trichodesmium the corresponding "Heinrich layers" at near proximity of colonies from the Sargasso Sea and investigated their elemental sediment source. Some special attention is given to signature. Element concentrations and spatial distributions in depositional mechanisms of fine glacial flour reworked by colonies were compared using inductively coupled plasma mass meltwater vs ice-rafted debris (IRD). Analysis includes, at ~ spectrometry (ICPMS), CHN analysis, and synchrotron x-ray 10 cm-intervals, uranium and thorium series measurements fluorescence (SXRF) mapping. Trichodesmium’s cellular (238U, 234U, 230Th and 232Th), at 4 cm intervals, semi- stoichiometry of 647C:111N:1P deviated significantly from the quantitative analyses of mineralogical assemblages (XRD), canonical Redfield ratio and illustrates the P-limiting condition at inorganic and organic carbon (Cinorg., Corg.) contents and the time of sampling. Additionally, ICPMS and SXRF analysis Corg./N data, coarse fraction abundance (>106 μm), which we confirmed that the metallome of Trichodesmium is enriched in V, associate with IRD, CAT-scan images; nine layers provided Fe and Ni in comparison to other phytoplankton. Surprisingly, V was enough Neogloboquadrina pachyderma (l) shells for 14C the most abundant metal in Trichodesmium, and the V quota was up measurements. Calibrated 14C ages indicate a mean to 4-fold higher than the corresponding Fe quota. Furthermore, sedimentation rate of ~ 27 cm/ka, Heinrich-layers included, SXRF mapping revealed the presence of V and Fe hotspots. These and of ~ 25 cm/ka when they are assigned a duration from hotspots typically spanned over several contiguous cells. The spatial literature data then excluded from the sediment inventory distribution of Ni differed from V and Fe and was enriched in (i.e., "background" sedimentation rate). 230Th-excesses 230 transverse walls between attached cells. As hotspots of V, Fe, or Ni ( Thxs) over supported fraction are estimated following were spatially decoupled from each other, we conclude that external Veiga-Pires & Hillaire-Marcel (1999). Preliminary results adsorption of aerosol particles on Trichodesmium trichomes did not show that the Heinrich layers contain up to 60% fine detrital 230 contribute to the elevated element quotas. Fe hotspots were found in carbonates (mostly calcite) and are highlighted by low Thxs only ca. 10% of analysed trichome sections, and Fe enrichment in (nearly 0 dpm/g) indicating an extremely fast depositional contiguous cells may be linked to diazocytes as zones of nitrogen mechanism of the fine fraction. Coarse fraction peaks fixation in Trichodesmium. In contrast, genomic analyses indicated highlight intense IRD on both sides of the fine detrital that V is not directly associated with nitrogenase in Trichodesmium. carbonate layer, i.e., from the very beginning until a "late" H- V maybe used in V-dependent haloperoxidases to protect the oxygen event phase. They likely correlate with the H-layers as 230 susceptible nitrogen fixing enzyme nitrogenase from reactive observed in more distal North Atlantic sites. Thxs oxygen species (ROS) such as hydrogen peroxide, but genomic inventories and background sedimentation rate calculated as 230 evidence for such an enzymatic role of V is also currently lacking. above, suggest much higher Holocene Thxs fluxes at the The presence of Ni in transverse walls is in agreement with genomic study site, in comparision to late glacial fluxes, resulting 230 evidence for the presence of Ni-superoxide dismutase and/or NiFe from Thxs-advection by an enhanced Western Boundary hydrogenase. Both Ni-containing enzymes are beneficial for Undercurrent. nitrogen fixation by either inactivation of the ROS species superoxide or the catalyzation of hydrogen, respectively. We [1] Hesse et al. (2004), Geology, 32, 449-452. conclude that the enrichment of these metals is directly or indirectly [2] Rashid et al. (2003a), Earth and Planetary Science Letters, 208, 319-336. linked to nitrogen fixation in Trichodesmium. [3] Veiga-Pires et al. (1999), Paleoceanography, 14(2), 187- 199.
Mineralogical Magazine | www.minersoc.org 2176 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts
Potential dissolution of sandstone in Use of vegetation, soil, and radiometric the presence of supercritical CO2- survey to locate areas of concealed H S-H O: An experimental and uranium mineralization at the Jacques 2 2 Lake area, Labrador. geochemical modelling approach Praise Nyade1*, Derek Wilton1, Henry Longerich1, Gary 1* 1 CHIJIOKE NWANKWOR , MERCEDES MAROTO-VALER , DAVID Thompson2, Paul McNeill3 1 2 2 LARGE , KEITH BATEMAN AND CHRIS ROCHELLE 1Department of Earth Sciences, Memorial University, St John’s, NL, 1University of Nottingham, Nottingham, NG7 2RD United Kingdom, A1B3X5, Canada, [email protected] (* presenting author) 2 [email protected] (*presenting author) College of North Atlantic, Burin Campus, Burin Bay Arm A0E1G0,
2British Geological Survey, Nicker Hill, Keyworth Nottinghamshire, Canada, [email protected] 3 NG12 5GG United Kingdom Auroral Energy Limited, St John’s, NL, A1C6H6, Canada, [email protected] Introduction The high monetary and energy costs associated with the Abstract We applied biogeochemical analysis of black spruce twigs, bark, production of pure CO2, for storage has necessitated the need for and Labrador tea shoots with soil geochemistry, and an air-borne consideration of waste stream with some impurities (e.g. H2S, SOx, magnetic and radiometric survey to delineate areas of uranium NOx). However, little knowledge exists on the geochemical impact of these gas mixtures when injected into geological formations for the enrichment at the Jacques Lake prospect of the Central Mineral Belt, Labrador, Canada. This area is overlain by thick layers of glacial till long term geological storage of CO2. We report results from initial and peat which effectively obscure the direct observation of experiments that have been conducted with pure CO2 as base cases with which to compare subsequent experiments involving impurities. mineralized outcrops and accompanying alteration haloes. The The experiments investigated the reaction of Permo-Triassic topography is rugged with dense coniferous forest cover, lacks access sandstones (the on-shore equivalent of a North Sea reservoir rock) roads, and is characterized by long and extreme winter weather conditions with very high precipitation. Biogeochemical signatures with brine in the presence of supercritical CO2. Experiments were conducted over 3-6 months using 0.5 M NaCl solution at 70°C and from black spruce twigs show elevated concentrations of U and pathfinder elements Be, Ag, Pb, and Sb over mineralized areas. A 200 bar pressure, conditions typical of many potential CO2 geologic storage sites. Modelling of the experimental systems was also carried PCA plot of the data discriminated the bedrock mineralization with out using PHREEQC. Figure 1 below shows the schematic content of good anomaly contrast for uranium and related pathfinder elements pressure vessel used for laboratory batch experiments. (Be, Ag, Sb, V and Pb). Bark samples of black spruce generally showed weak to moderate anomaly contrasts. Labrador Tea leaves and stems defined very low anomalies or none at all; and possibly attributable to the shallow root system of the shrub. There is metal enrichment and an expression of the bedrock mineralization in the B- horizon soil. The distribution of U, Sb, Cu, Pb and to a less extent V in the soil exhibit anomalous signatures that may reflect a primary mineralized halo associated with the Jacque’s Lake U prospect. Uranium concentrations (mixed acid digest) in soil ranged from 0.01 – 867 ppm. Areas of anomalous U concentration in B-horizon soils coincide with the airborne magnetic and radiometric and black spruce twig uranium anomalies that defined the Jacque’s Lake deposit.
Figure 1: Schematic of pressure vessel
Results and Conclusions Increasing concentrations of Mg, Ca and K were observed in the experiments over time. Mineralogical analyses and mass balance calculations for reacted and un-reacted rock samples, indicate that increases of Mg and Ca may be explained by dissolution of carbonate minerals such as calcite and dolomite, possibly followed by slight dissolution or ion-exchange with clay minerals. K concentrations are possibly governed by dissolution of trace halide minerals. In non- reactive ‘control’ experiments representing only the fluid-rock
system equilibration using N2 gas as the pressurising fluid, concentrations of the same elements were much lower. PHREEQC modelling utilised rates of mineral dissolution and precipitation from the literature. Longer-term trends in observed solution chemistry could be modelled, if some assumptions about reactive surface areas were made. However, the model could not account for observed decreases in concentration of dissolved elements such as Al and Fe. Work is in progress to account for these changes and will be presented at the conference. Preliminary results
from on-going experiments involving fluid-rock-CO2 reaction in the presence of impurities (particularly H2S) will also be presented.
Mineralogical Magazine | www.minersoc.org 2177 Downloaded from http://pubs.geoscienceworld.org/minmag/article-pdf/76/6/2151/2920063/gsminmag.76.6.14-N.pdf by guest on 02 October 2021 Goldschmidt 2012 Conference Abstracts Iron L- and M- edges of iron containing minerals measured by x- ray Raman scattering 1* 1 ALEXANDER NYROW , CHRISTIAN STERNEMANN , MAX 2 1 1 WILKE , KOLJA MENDE , CHRISTOPH SAHLE , LAURA 3 4 5 SIMONELLI , ROBERT GORDON , NOZOMU HIRAOKA , 1 1 6 FLORIAN WIELAND , METIN TOLAN AND JOHN TSE 1Technische Universitaet Dortmund, Germany, alexander.nyrow@tu- dortmund.de 2Deutsches GeoForschungsZentrum, Potsdam, Germany 3European Synchrotron Radiation Facility, Grenoble Cedex, France 4PNC-SRF, Department of Physics, Simon Fraser University, Burnaby, Canada 5National Synchrotron Radiation Research Center, Taiwan 6University of Saskatchewan, Saskatoon, Canada
Concerning the composition of the Earth’s core and mantle, iron is one of the most interesting elements for applications in geosciences. Investigation of its electronic structure is essential to understand the origin of physical properties of different iron containing minerals existing in the Earth’s interior. E.g. Fe2+/Fe3+ ratios, the spin state as well as the oxygen fugacity can vary significantly at relevant conditions, i.e. pressures up to 1 Mbar and temperatures up to 3000°C [1-2]. Thus, experimental determination of such parameters in situ is crucial to understand the thermodynamic properties of these minerals [3].
X-ray Raman scattering (XRS) provides a possibility to measure electronic excitations by inelastic x-ray scattering which yields similar information like measurement of x-ray absorption edges by x-ray absorption spectroscopy (XAFS) or electron energy loss spectroscopy (EELS) [4]. Because XRS is an energy loss technique and the energy of the incident radiation does not depend on the binding energy of an atom, in contrast to XAFS and EELS, measurments of absorption edges of low Z elements in soft x-ray regime are possible using hard x-rays which allows measurements even in highly absorbing sample environments like diamond anvil cells with resistive or laser heating.
In this study, Fe L2/3 and M2/3-edges of different iron oxides and iron containing minerals measured by x-ray Raman scattering are presented in comparison with XAFS and EELS results. Furthermore,
the momentum transfer dependency of the Fe M2/3-edge is discussed. Possible applications in geosciences are pressure induced electronic transitions in iron containing minerals.
[1] Narygina, Kantor, McCammon (2010) Physics and Chemistry of Minerals 37, 407. [2] Speziale, Milner, Lee, Clark et al. (2005) Proced. Nat. Acad. Sci. 102 17918. [3] Wilke, Farges, Petit, Brown and Martin (2001) Amer. Mineral Soc.86, 714 [4] Schülke (2007) Electron Dynamics by Inelastic X-ray Scattering (Oxford University Press).
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