A924 Goldschmidt Conference Abstracts 2008
Injection of short-lived and stable Use of LC-IRMS for the direct nuclides from a “faint” supernova determination of stable Carbon into the early solar system isotope ratios in river waters
S. TACHIBANA K. TAGAMI* AND S. UCHIDA Department of Earth and Planetary Science, University of Natl. Inst. Radiol. Sci., 4-9-1 Anagawa, Chiba 263-8555, Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan Japan (*correspondence: [email protected]) ([email protected]) Simple Application of LC-IRMS The estimated initial abundance of 60Fe in the solar system Recently methods using liquid chromatography isotope (e.g. Tachibana et al. [1]), which is produced efficiently only ratio mass spectrometry (LC-IRMS) have become available by stellar nucleosynthesis, implies that stellar nucleosynthesis for the determination of stable carbon isotope ratios (δ13C) of prior to or shortly after the birth of the solar system organic carbon in aqueous solutions [1, 2]. It would be contributed to the inventory of the solar-system short-lived interesting if we could use the method to ascertain the origin radionuclides. A faint mixing-fallback supernova, where the of C in river waters. In this study, therefore, we applied the inner region of the exploding star experienced mixing, some method to determine the chemical species of C in Japanese fraction of mixed materials is ejected, and the rest undergoes river waters, and then applied a non-column separation fallback onto the core, reproduces the abundance pattern of method for total δ13C measurement. We used a LC IsoLink hyper metal-poor stars [2]. We recently proposed that a single interface, which couples a Surveyor HPLC to a continuous- faint mixing-fall back supernova could be a source of 26Al, flow Delta V Advantage IRMS (Thermo Fisher Scientific Co). 41Ca, 53Mn, and 60Fe in the solar system [3, 4]. We evaluate here injection of stable isotopes of C, N, and Results and Discussion O from a nearby mixing-fallback supernova to the solar All values of DOC were less than 0.1 mg L-1 in 41 rivers 2- - system materials. Possible changes of C, N, O isotopes due to (410 samples). Inorganic C, i.e., CO2, CO3 , and HCO3 , injection from a faint mixing-fallback SN with a dilution thought to be the major C forms in these river waters, but, factor of 10-4-10-3 would be a few tens ‰ for δ13C, <100‰ for unfortunately, they cannot be separated by the HPLC-IRMS δ14N, and < a few hundreds ‰ for δ17O and δ18O. Possible system. Using the non-column separation method, total changes of oxygen isotopes would not be large enough to soluble C content in the river waters and δ13C values were explain a difference in O isotopic compositions between pre- measured. Figure 1 shows the histogram of total δ13C in river solar silicates and solar system materials. However, if SN waters. The mean value was -9.6‰ which is close to materials were injected into a proto-solar disk (e.g. Takigawa atmospheric δ13C of about -7‰. There were some rivers et al. [4]), effects of injection of C, N, O isotopes in solar which showed relatively low δ13C values; possible geological system materials are not negligibly small, and there might be sources will be discussed. differences in the abundances of those isotopes between the Sun and solar system materials, as suggested by [5].
[1] Tachibana et al. (2006) ApJ 639, L87 [2] Iwamoto et al. (2005) Science 309, 451. [3] Takigawa et al. (2007) LPS XXXVIII, #1720. [4] Takigawa et al. (2008, submitted) ApJ. [5] Ouellett et al. (2005) in Chondrites & the Protoplanetary Disk, eds. A. N. Krot et al., 527. [6] Gounelle & Meibom (2007) ApJ. 664, L123.
Figure 1: Histogram of δ13C in Japanese river waters.
[1] Krummen et al. (2004) Rapid Commun. Mass Spectrom. 18, 2260-2266. [2] Heuer et al. (2006) Limnol. Oceanogr. Methods 4, 346-357. Goldschmidt Conference Abstracts 2008 A925
Mineralogical evidence of advanced Mineralogical and petrological argillic alteration, Ghaleh Dar Area, studies of the igneous-evaporite rocks in the Central Iranian Magmatic Belt within salt domes, high Zagros, Iran 1 1 2 B. TAGHIPOUR , M.A. MACKIZADEH , A. KASSON , S. TAGHIPOUR, M.A. MACKIZADEH AND B. TAGHIPOUR 3 1 A. DELEGADO HUERTAS AND S. TAGHIPOUR Geology Department, Isfahan University, Iran 1Department of Geology, Isfahan University, Isfahan, Iran ([email protected]) ([email protected]) 2Cornell Isotope Laboratory, Cornell University, Ithaca, NY Kaj-Rostam Abad, Dashtak and Do Ab salt domes are USA located around Ardal and Farsoun village. This area is situated 3Estacin Experimental del Zaidn (CSIC) in High Zagros (Chaharmahal and Bakhtiary province). The study area is composed of lower Cambrian The Eocene volcanics and pyroclastics from the Ghaleh volcanosedimentary complex including basalt, basaltic Dar area (part of the Cenozoic magmatic belt of Central Iran) andesite, andesite, trachyte, pyroclastics, evaporite rocks and have undergone extensive hydrothermal alteration. Major Precambrian sedimentary units. alteration zones are showing inclusions of, propylite, quartz The igneous rocks out cropped are volcanic and sub sericite, advanced argillic and silicified zones. Ghaleh Dar volcanic. These rocks have complex mineralogical alunites are mainly porcelaneous and their compositions show composition. Those minerals have crystallized in magmatic a solid solution between alunite and jarosite. The following stage (plagioclase, clinopyroxene, apatite and kersutite), mineral assemblages are distinguished in alteration zones: metasomatism (actinolite, biotite, quartz, sphene, calcite and epidote) and vein mineralization (actinolite, albite, quartz, Alunite-jarosite + quartz + sericite + alkali feldspars + calcite, garnet, chlorite and epidote). Petrographical study chlorite ± turquoise ± barite ± iron oxides. shows that microlitic-porphyric, intersertal and amygdaloidal textures in these rocks. Chlorite, epidote and actinolite are There are many alunite and jaroste occurrences, mainly as common in basaltic rocks. Extensional stress may be caused veinlets, in parts of the advanced argillic zone. the formation of apatite and gypsum. Olivine without reaction Alunite δ18O and δ2H values fall in range -1.76 to 8.81‰ margins, apatite, needle kaersutite and clinopyroxene with and -52.86 to -129.26‰ respectively. On the basis of field, sector twining and zoning point to the alkaline nature of the mineralogical evidence and results from light element stable rocks. isotope data (δ18O, δ2H and δ34S), the Ghaleh Dar alunitization We have done some EPMA on clinopyroxexne, is derived from the supergene origin. hornblende, garnet, asbest amphibole, epidote and palgiocalse. EMPA results show titaneaugite-diposide, kaersutite, actinolite, andradite-grossular, pistachite and albite are main minerals in these rocks. The high content of TiO2 center in hornblende and clinopyroxene has shown the alkaline nature of magmatism which occurred within plate rift environment. Hydrothermal phase enriched in Na2O, Fe2O3, H2O, CO2 and CaO has caused epidote, calcite and actinolite. On the basis of XRF analyses the chemical composition of these rocks are basalt to trachyte. According to the geochemical diagrams the nature of magma is transitional. By the clinopyroxene geochemical and geothermometry data, this mineral is formed in the 1220ºC and intermediate to low in pressure. Not only the vein chlorite temperature is 350ºC-510ºC but also the asbest amphibole and andradite are stabeled in 300ºC-520ºC and 0.5-2 K bar in pressure. On the fluid inclusion study of vein quartz the salinity of hydrothermal fluid is high. The values of 18O/16O isotopic data have shown that the veins of quartz have originated from sedimentary-evaporate fluids. A926 Goldschmidt Conference Abstracts 2008
Characterization of binding sites of Methanogenesis at 122°C renews the metal ions at bacterial cell surface by upper temperature limit for life and REE distribution patterns and the stable carbon isotopic EXAFS analysis fractionation of microbial 1 1 2 Y. TAKAHASHI *, M. YAMAMOTO , T. OZAKI AND methanogenesis 3 D. FORTIN K. TAKAI 1Department of Earth and Planetary Systems Science, Subground Animalcule Retrieval (SUGAR) Program, Japan Hiroshima University, Hiroshima 739-8526, Japan Agency for Marine-Earth Science and Technology (*correspondence: [email protected]) (JAMSTEC), Yokosuka 237-0061, Japan 2Advanced Science Research Center, JAERI, Tokai, Japan ([email protected]) 3Department of Earth Sciences, University of Ottawa, ON,
K1N 6N5, Canada ([email protected]) Microbial methanogenesis in the deep-sea is a key process
in the carbon cycle of Earth. It contributes to the CH pool Interactions with bacteria can affect the migration of metal 4 (free gas and methane hydrate) in deep-sea sediments, which ions in natural waters through sorption and precipitation at the is a potential energy source and alternative to petroleum as bacterial cell surface. In order to understand metal ion well as a strong greenhouse gas with a potential for rapid reactions with bacterial cell surfaces, it is essential to release. Hyperthermophilic methanogens are important characterize the binding sites. Among various metal ions, rare primary producers in the hot ecosystem represented by the earth elements (REE) are unique due to the systematic deep-sea hydrothermal areas and may represent the most decrease of their ionic radii with the atomic number. Previous ancient type of life flourishing in the early Earth. REE sorption studies with various bacterial strains [1, 2] Nevertheless, the biogeochemical function and impact of showed an anomalous enrichment of heavy REE (HREE) to methanogens in deep sea and deep subseafloor are poorly bacterial cell surfaces, which was likely related to the type understood, in part because it is difficult to replicate the high binding site, since REE solid-water distribution patterns temperatures and hydrostatic pressures in the laboratory. Here, reflect the chemical characteristics of the adsorbents’ binding we report a new technique for cultivation of sites. chemolithoautotrophs including methanogens under high The comparison of REE distribution patterns between hydrostatic pressures. Using this technique, growth, survival water and bacteria to those between water and model and methane production of a newly isolated, compounds simulating bacterial binding sites (such as hyperthermophilic methanogen Methanopyrus kandleri strain carboxymethyl cellulose, cellulose phosphate, alkylphosphate, 116 was characterized under high temperatures and peptidoglycan, and phospholipid) indicated that the HREE hydrostatic pressures. Elevated hydrostatic pressure extended enrichment was caused by the binding to multidentate the temperature maxium for growth from 116°C at 0.4 MPa to phosphate (phosphoryl) sites, while lighter REE were bound to 122°C at 20 MPa, which exceeds the previously reported phosphate (phosphoryl) sites with lesser coordination number. upper temperature limit for life of 121°C. In addition, The results from the REE patterns were complemented by piezophilic growth significantly affected stable carbon isotope EXAFS analysis at L -edges of various REE, such as Nd, Sm, III fractionation of methanogenesis from CO . Under the Gd,, Tb, Ho, Er, Yb, and Lu. Heavier REE (Yb and Lu) onto 2 conventional growth conditions, the isotope fractionation of bacteria and peptidoglycan exhibited similar structures to methanogenesis by M. kandleri strain 116 was similar to those complexed to alkylphosphate which forms multidentate values (ε = -30 ‰ to -25 ‰), previously reported for other phosphate complexes to REE. On the other hand, lighter REE hydrogenotrophic methanogens. However, under high (Nd and Sm) onto bacteria and peptidoglycan had similar hydrostatic pressures of 40 MPa, the isotope fractionation structures to those sorbed on celluose phosphate. The coherent effect became much smaller (ε = -20 ‰ to >-15 ‰), and the results of REE patterns and EXAFS show that two different kinetic isotope effect at 122°C was -13.1 ‰, which is the phosphate sites are responsible for the sorption of REE, or smallest effect ever reported. This observation will clarify the other metal ions, onto bacteria. source of deep-sea methane as well as the ecophysiological
and biogeochemical functions of methanogens and other [1] Takahashi et al. (2005) Chem. Geol. 219, 53-67. chemolithoautrophs in deep-sea environments. [2] Taksahashi et al. (2007) Chem. Geol. 244, 569-583. Goldschmidt Conference Abstracts 2008 A927
W isotopic composition Application of NMR to characterize and concentration of Intact Polar Lipids in deep biosphere 1 2 2 1 oceanic island basalts Y. TAKANO , F. INAGAKI , Y. MORONO , N.O. OGAWA , 1 1 1 1 1 2 H. KITAZATO AND N. OHKOUCHI A. TAKAMASA , Y.V. SAHOO , S. NAKAI , T. HANYU , 2 2 H. KAWABATA AND Y. TATSUMI 1Institute for Research on Earth Evolution (IFREE), Japan Agency for Marine-Earth Science and Technology 1Earthquake Research Institute, The University of Tokyo (JAMSTEC) ([email protected]) ([email protected], [email protected], 2Kochi Institute for Core Sample Research, Japan Agency for [email protected]) Marine-Earth Science and Technology (JAMSTEC) 2Institute for Frontier Research on Earth Evolution, Japan
Marine Science and Technology Center Intact polar lipids (IPLs) are attractive analytical targets in ([email protected], [email protected], deep biosphere study, because they are taxonomically more [email protected]) specific than their apolar derivatives and avoid signals from
prokaryotes that primarily build their membranes with ether- To understand W behavior during magmatic bound lipids such as archaea and some bacteria (e.g. Sturt et differentiation and to detect the evidence of core-mantle al. 2004 [1]). Appling chromatographic separation by high- interaction using W isotopic tracer, the W abundances and performance liquid chromatography (HPLC), Rutters et al. [2] isotope compositions were analyzed for oceanic island basalts developed a normal-phase chromatography procedure from (OIB) from French Polynesia, Samoa, St. Helena and Hawaii. that primarily separates lipid mixtures according to the polar Global seismic tomography suggests that plume sources of headgroups. Futhermore, HPLC/ESI-MSn is potentially useful French Polynesia and Samoa may originated from the core- for identifying novel biomarkers for biogeochemistry and mantle boundary. An additional reason for analyzing OIB in microbial ecology by exploiting the taxonomic information French Polynesia and St. Helena is that some of them are encoded in intact membrane molecules from prokaryotes. classified into HIMU (high time integrated 238U/204Pb or high However, so far lack of authentic standards prevented µ)OIB, which was considered to tap the mantle source with identification of chemical structure of whole molecules and minor contributions of recycled sediments with high W polar headgroups in IPLs analogs, and determination of abundance. Core-mantle interaction has been discussed for the absolute concentrations because response factors of different samples from Hawaiian island using Os, Tl and W isotope IPLs in LC/MS could vary significantly. On the purpose of ratio and Fe/Mn ratio from 1990’s [1-5]. We have also worked overcoming such difficulties, here we propose a usage of on Hawaiian samples. Nuclear Magnetic Resonance (NMR) spectroscopy together We will present the data of tungsten isotope ratio and with LC/MS technique in the quantification and structual concentration of OIBs and discuss the core-mantle interaction assignment of IPLs. In this presentation, we will report using our data. preliminary results of sub-seafloor core samples collected by
shakedown cruise of drilling vessel Chikyu (CK06-06) at [1] Brandon et al. (1998) Science 280(5369), 1570-1573. offshore of Shimokita Peninsula, Western Pacific Ocean. [2] Collerson et al. (2002) Geochimica et Cosmochimica Acta
66, (15A) A148. [3] Scherstén et al. (2004) Nature 427, 234- [1] Sturt et al. (2004) Rapid Communications in Mass 237. [4] Humayun et al. (2004) Science 306, 91-94. [5] Baker Spectrometry 18(6), 617-628. [2] Rutters et al. (2002) Journal & Jensen (2004) Earth & Planetary Science Letters 220(3-4), of Microbiological Methods 48(2-3), 149-160. 277-286. A928 Goldschmidt Conference Abstracts 2008
Distributions of Rare Earth Elements Experimental study on the in Japanese estuaries mechanism of metasomatism in the
H. TAKATA*, T. AONO, K. TAGAMI AND S. UCHIDA system between Scheelite↔Ferberite 1 1 2 National Institute of Radiological Sciences, Chiba 263-8555, I. TAMURA *, N. SHIKAZONO AND M. NAKATA Japan (*correspondence: [email protected]) 1Department of Applied Chemistry, Faculty of Science and
Technology, Keio University, 3-14-1 Hiyosi, Kohoku-ku, Introduction and Methods Yokohama 223-8522, Japan Direct determination using ICP-MS for rare earth elements (*correspondence: [email protected], (REEs) in seawater, which are presumably present at less than [email protected]) the detection limit, is a difficult analytical task in the presence 2Department of Astronomy and Earth Science, Tokyo Gakugei of seawater matrix. A simple and rapid method to separate and University, 4-1-1 Nukui-kitamachi, Koganei, Tokyo, 184- concentrate REEs in seawater was developed using a new 0015, Japan ([email protected]) chelating resin, NOBIAS chelate-PA1, which is a polyamino- polycarboxylic acid type resin. The resin was then used in an Experiments on metasomatism were carried out in the investigation of the geochemical behaviors of REEs in tungstates (scheelite and ferberite) - aqueous solutions Japanese estuaries which are reported here. (Fe[NH ] [SO ] and CaCl ) system. We changed duration 4 2 4 2 2 (1 to 2016 hours), concentration of aqueous solution (0.01 to Results and Discussion 1.0 mol/l) and temperature (130 to 170 °C). The starting The REEs were recovered at more than 90% for a pH materials were powdered sample (100 µm) and chipped ranging between 5 and 6 in spiked seawater samples which sample (1.5×2.0×3.0 mm). were diluted in a salinity value ranged from 0 to 34. Total The peaks of ferberite and scheelite were detected from procedural blanks for REEs for the present study were lower reacted samples by X-Ray diffraction analysis in the scheelite than 0.1 ppt. It was concluded that the chelating resin can be - Fe[NH ] [SO ] and ferberite - CaCl aqueous solution applied for the preconcentration of REEs in estuarine water 4 2 4 2 2 system, respectively. The metasomatism is easy to proceed as samples. the concentration of the reaction solution is higher and the The determined REE concentrations in the natural water reaction temperature is higher. It is considered that the samples indicated geochemical properties in the Japanese reaction rate occurring in initial stage was high due to the wide estuaries. These concentrations increased rapidly at low contact area between solution and unreacted material and the salinity (~1). Such a trend has been observed in some rivers presence of fine particles on the surface of starting material [1, 2]. The increase in REEs concentrations was attributed to which rapidly dissolved. The replacement textures were the salt-induced desorption from resuspended particles in river observed by SEM and reflected light microscope. SEM waters [3]. The concentrations of the REEs were constant at observation shows the euhedral crystal of scheelite formed in high salinity (>20) near the mouth of the rivers, indicating the the ferberite - CaCl aqueous solution system due to slow removal of REEs during mixing in the estuary at a salinity 2 growing of the crystal. value less than 20, as has been reported in other estuaries [2]. Ferberite crystals grow toward the inside of starting The REE concentrations slightly decreased with distance from material (scheelite) accompanying a lot of pores in the the mouth of the rivers. scheelite - Fe[NH ] [SO ] aqueous solution system, since This work has been partially supported by the Agency for 4 2 4 2 molar volume of ferberite (40.40 cm3) is smaller than that of Natural Resources and Energy, the Ministry of Economy, scheelite (47.05 cm3). The tendency in the thickness variation Trade and Industry (METI), Japan. of chipped sample with time could not be recognized in the
metasomatism from scheelite to ferberite. The replacement [1] Nozaki et al. (2000) GCA 64, 3975–3982. [2] Nozaki et al. texture is classified into the pseudomorphic replacement GCA 64, 3983–3994. [3] Elderfield et al. (1990) GCA 54, texture [1-3]. On the contrary, small amount of scheelite was 971–991. precipitated on the surface of starting material (ferberite) in the ferberite - CaCl2 aqueous solution system. The size of the sample increases with time so that the replacement texture grows not only toward the inside of samples but also on the surface of starting material. The texture is categorized into rim replacement texture.
[1] Edwards (1960). [2] Bastin (1969). [3] Craig & Vaughan (1981). Goldschmidt Conference Abstracts 2008 A929
Primary andesite melts: New insight H, O, Sr isotopic constraint on from NW Rota-1 volcano evolution of the oilfield brines in the 1,2 3 4 2 Y. TAMURA *, A. SHAW , O. ISHIZUKA , H. SHUKUNO western Qaidam Basin, China 2 AND H. KAWABATA 1,2 1 2 2 2 H. TAN *, W. RAO , B. LI , J. XU AND T. LI 1Earth and Planetary Sciences Department, UCSC, CA 95064 1Research Institute of Science, Hohai University, Xikang Road (*correspondence: [email protected]) 1, Nanjing 210098, Jiangsu, China 2IFREE, JAMSTEC, Yokosuka 237-0061 2Institute of Salt Lakes, Chinese Academy of Sciences, 3WHOI, Woods Hole, MA 02543 Xining, 81008, China 4GSJ/AIST, Tsukuba 305-8567, Japan
Background NW Rota-1 volcano is an active submarine volcano in the During the prospecting and exploration for oil and gas in Southern Seamount Province of the Mariana arc [1]. Using the western Qaidam Basin, China, much oilfield brine was JAMSTEC’s ROV, a total of 42 rock samples were collected discovered in the Tertiary strata, which will likely make up for from the summit region (531-1080 mbsl) and near the base the limited salt lake resources in future [1], but to nowadays, (1474-2260 mbsl) of the volcano. These lavas are medium-K about its origin source and formation are still unclear. Based basalts and andesites with 51.5-58.2 wt% SiO . We note, that 2 on some brine samples collected from petroleum drills, their lavas ranging from 54-57 wt% SiO are conspicuously absent 2 composition of strontium, deuterium and oxygen isotopes and that most lavas tend to cluster at 52 and 57 wt% SiO . In 2 were measured in order to trace their origin, formation and constrast, melt inclusions trapped within olivine grains from resource distribution. the same lavas span a much wider range (48.7 to 56.9 wt%
SiO2) and show a continuous range (i.e., no gaps). Here we Discussion of Results explore why this difference is observed and evaluate whether The oilfield brines show with heavier compositions in melt inclusions record primary andesite melt compositions. δ18O values (from 0.47‰ to 15.89‰) and lighter composition Major element compositions of melt inclusions are based in δD values (from -50‰ to -27‰), which deviate from the on volatile-free compositions, normalized to 100% with total global and Qaidam Basin meteoric water lines and show iron calculated as FeO. Estimated primary magmas of these positive oxygen excursion. 87Sr/86Sr values in oilfield brines melt inclusions range from basalt to magnesian andesite range from 0.711163 to 0.712396. With respect to typical end- (48-55 wt% SiO ) and, interestingly, these compositions are 2 members of the strontium isotopes in lithosphere source similar to compositions of melts formed by partial melting of (average value is 0.720) and mantle source (average value is peridotite under hydrous conditions [2]. Water contents of 0.704), the 87Sr/86Sr ratios are just intervenient between them. melt inclusions range from 1.1 up to 5.8 wt% H O [3] and we 2 Thus it can be proved by H, O and also Sr isotopes that the suggest that compositions could represent primary melts. We oilfield brines origin from two mixing end-members: deep reject the possibility that melt inclusions are simply recording mantle fluid and lithosphere source fluid. Then we conclude differentiation processes since the range in SiO is found over 2 that a large supply source for the brines and the foreground of a relatively narrow range of MgO contents. the brine exploration should be expected. If melt inclusions are recording a wide range of primary melts composition, why do complementary lavas record such a [1] Tan et al. (2007) Journal of Palaeogeography 9(3), 313- restricted range of compositions? One possible explanation is 320. that lavas have experienced late stage differentiation processes, obscuring primary source compositions (e.g. Tamura et al. [4]). Pyroxenes found in lavas show compositional zoning and based on thermometry estimates [5], suggest cool core temperatures 800-900°C, as compared to their rims (1000-1100°C). We suggest that low temperature, water-rich andesite magmas stalled at depth, but were later reheated and remobilized by partial melting within the crust.
[1] Embley et al. (2006) Nature 441, 494-497. [2] Kushiro (1990) J. Geophys. Res. 95, 15929-15939. [3] Shaw (2006) Eos Trans. AGU, 87(52) [4] Tamura et al. (2003) J. Petrol. 44, 2243-2260. [5] Lindsley & Andersen (1983) J. Geophys. Res. 88, 887-906. A930 Goldschmidt Conference Abstracts 2008
Local structures of Y and Ho in Lead isotope systematics of calcite and its relevance to olivine-hosted melt inclusions from Y fractionation from Ho Hawaiian lavas
K. TANAKA*, Y. TAKAHASHI AND H. SHIMIZU R. TANAKA*, P.A. SAKYI, K. KOBAYASHI AND E. NAKAMURA Hiroshima University, Higashi-Hiroshima 739-8526, Japan (*correspondence: [email protected]) The Pheasant Memorial Laboratory, Institute for Study of the Earth’s Interior, Okayama Univ., Misasa, 682-0193, Japan The behavior of Y and Ho in most igneous activities is (*correspondence: [email protected]) very close due to the similarity in their ionic radii, while Y fractionates from Ho in marine systems. In this study, in order We present new data on Pb isotopic compositions of to elucidate Y-Ho fractionation observed in marine systems in olivine-hosted melt inclusions from Kilauea, Mauna Loa and terms of structural chemistry, we examined Ho LIII-edge and Koolau lavas with those previously reported [1]. Only olivine Y K-edge EXAFS study for two partitioning systems, namely, grains that were >1 mm in size, which should have high 1) calcite-aqueous solution (Y-Ho fractionation system) and 2) dislocation densities [2] were selected for melt inclusion strong acid cation exchange resin-aqueous solution (non Y-Ho studies. The Pb isotopic compositions of olivine-hosted melt fractionation system). The results of the EXAFS analysis did inclusions show a systematic increase in 207Pb/206Pb and not show significant differences in interatomic distances to the 208Pb/206Pb in the order Kilauea < Mauna < Koolau Makapuu, most neighboring O atoms between Ho and Y for all the with considerable overlap with each other in general. samples (Table 1). However, several melt inclusions extend beyond their whole- rock field of each volcano or even of whole ranges of all Hawaiian lavas. Since the deformed olivines that crystallized from previous magmas could have been trapped from the conduit wall or magma chamber into the magma, the analyzed Pb isotopic compositions of melt inclusions should carry the signatures of the previous magma(s) in the same volcano from which they crystallized. The evolution of magmas that eventually erupted to form the Kilauea, Mauna Loa and Koolau volcanoes could be explained by the supply of batches of magmas of similar or different chemical and/or isotopic compositions into magma chambers where olivine crystallization, fractionation, deformation and subsequent entrainment occurred. We propose that the batches of magma in the preceding stages of the Kilauea volcano had Kilauea- However, the first shell Ho-O and Y-O distances in the Y- and Loihi-like compositions. Likewise, Mauna Loa volcano Ho doped calcite were shorter than those in the aqua ion. In recorded the exhaustion of Kilauea-/Loihi-like and Loa contrast, the first shell Ho-O and Y-O distances in the Y-Ho components and the initiation of Loa component, which is doped resin were similar to those in the aqua ion. Previous chemically and isotopically different from the previous Loa studies have suggested that lanthanide (Ln) is more covalent component. The Koolau volcano probably recorded the history due to 4f orbital participation in bonding relative to Y. of three batches of magma. Kilauea-like magma dominated Spectroscopic studies on various Ln3+ complexes show that 3+ early Main shield stage, which was followed by low Racah parameters for 4f electron repulsion in Ln ions 207 206 3+ Pb/ Pb MORB-like magmas, and finally the high decrease with an increase in covalency of bonding of Ln 207Pb/206Pb magma typically found in Makapuu-stage lavas. ions with anionic ligands. Therefore, our EXAFS results These evidences suggest that the Hawaiian olivine-phyric suggest that Y-Ho fractionation in partitioning is possibly lavas contains significant amount of earlier-stage olivine attributed to the difference of change in covalency associated grains that crystallized from magma that has different with the ligand exchange between Y and Ho, which we have geochemical characteristics from the host magma. observed as differences in partition coefficients between calcite and aqueous solution. [1] Kobayashi et al. (2004) Chem. Geol. 212, 143-161. [2] Sakyi et al. (2008) GCA, this volume. [1] Tanaka et al. (2008) Chem. Geol. 248, 104-113. Goldschmidt Conference Abstracts 2008 A931
Geochronology and geochemistry of Equilibrium Fe isotope fractionations ore-bearing porphyries in the in solutions
Lamasu and Dabate areas, western M. TANG AND Y. LIU* Tianshan (Northern Xinjiang, China) State Key Laboratory of Ore Deposit Geochemistry, Institute 1,2 1 1 3 of Geochemistry, Chinese Academy of Sciences, Guiyang G.J. TANG , Q. WANG *, Z.H. ZHAO , D.A. WYMAN , 1,2 1,2 550002, China ([email protected]) Z.Q. JIANG AND X.H. JIA
1Key Laboratory of Isotope Geochronology and Urey model or Bigeleisen-Mayer equation based Geochemistry, Guangzhou Institute of Geochemistry, theoretical method has been used to calculate the fractionation Chinese Academy of Sciences, Guangzhou 510640, China factors for almost all possible Fe-Cl, Fe-OH, Fe-NO3 and Fe- (*correspondence: [email protected]) HCO3 species in solution. It includes almost all possible ferric 2Graduate School of Chinese Academy of Sciences, Beijing and ferrous Fe monomer aqueous species, such as Fe3+, Fe2+, III 2+ III + III III - II + II II - 100049, China Fe Cl , Fe Cl2 , Fe Cl3, Fe Cl4 , Fe Cl , Fe Cl2, Fe Cl3 , 3 II 2- III 2+ III + III III - School of Geosciences, Division of Geology and Geophysics, Fe Cl4 , Fe OH , Fe (OH)2 , Fe (OH)3, Fe (OH)4 , III 2- III 3- II + II II - The University of Sydney, NSW 2006, Australia Fe (OH)5 , Fe (OH)6 , Fe OH , Fe (OH)2, Fe (OH)3 , II 2- III 2+ III + II + III 2+ Fe (OH)4 , Fe NO3 , Fe (NO3)2 , Fe NO3 , Fe HCO3 , III + II + II The Lamasu and Dabate porphyry plutons are associated Fe (HCO3)2 , Fe HCO3 and Fe CO3, etc. The super- with copper mineralization located to the north of the Sayram molecule clusters are used to precisely evaluate the solvation Lake, west Tianshan (northern Xinjiang, China). The Lamasu effects. At least 36 water molecules to be used to build the pluton mainly consists of granodiorite, plagiogranite and supermolecules. Up to 6 different conformers for each super- diorite porphyries, but the Dabate pluton principally contains molecule are used to prevent the errors from the diversity of biotite-bearing granite porphyries. The Lamasu porphyries are configurations in solution. The B3LYP/6-311G* level calc-alkaline, and are mainly characterized by high Al2O3 frequencies are then calculated for this study. Liu and Tossell (16.6-16.7 wt.%), Sr (308-444ppm) and Mg# (52-60) values, [1] and Rustad et al. [2] have demonstrated that this but relatively low Y(10.6-16.8 ppm) and Yb (1.21-1.60 ppm) supermolecule method could produce fractionation factors contents, similar to subducted-oceanic crust-derived adakites. with the accuracy equal to experimental results. The Dabate porphyries are geochemically similar to A2-type Many of our results are different from the previous granites, e.g., high SiO2 (75.6-77.6 wt.%), alkalis (Na2O+ studies. For example, we find the fractionation between # 3+ 2+ K2O= 8.27-8.70 wt. %), low CaO (0.28-0.34 wt. %) and Mg Fe (aq) and Fe (aq) in pure water is 3.5±0.2‰ at 22°C and (1.8-10), distinctly negative Eu, Ba and Sr anomalies. Our new 4.0±0.2‰ at 0°C. It is different from the previous studies. Our zircon LA-ICP-MS U-Pb age data suggest that the Lamasu results will largely expand the database of Fe equilibrium adakitic porphyry and the Dabate A-type granite porphyry isotope fractionation factors. were generated at 366.3±1.9Ma and 288.9±2.3 Ma, respectively. We suggest that the Lamasu porphyries may be [1] Liu & Tossell (2005) GCA 69, 3995-4006. [2] Rustad et al. formed in island arc setting, related to Late Devonian (2008) JPC A 112, 542-555. subduction of the North Tianshan Ocean. However, the Dabate porphyries were likely emplaced in a post-collisional setting, related to post-orogenic lithospheric extension during the Early Permian. Taking into account Late-paleozoic tectonics[1] and Carboniferous arc magmatism[2, 3] in the northern Tianshan, we suggest that the Tianshan area was in an arc setting during the Late Devonian-Carboniferous, but evolved into a post- collisional stage in the Early Permian.
This study was jointly supported by the Major State Basic Research Program of People’s Republic of China (No. 2007CB411308) and the NNSFC (Grant No. 40673037).
[1] Xiao et al. (2006) Acta Petrol. Sin. 22(1) 1062-1076. [2] Wang et al. (2006) Acta. Petrol. Sin. 22, 11-30. [3] Wang et al. (2007) Chem. Geol. 236, 42-64. A932 Goldschmidt Conference Abstracts 2008
Structure investigation of Structural investigation of Fe(II) Cr(III)-Fe(III)-oxyhydroxides adsorption on hematite (0001) and 1 1 1,2 Y. TANG *, F.M. MICHEL , J.B. PARISE AND (1102 ) 1 R.J. REEDER 1 1 2 K.S. TANWAR *, S.C. PETITTO , S.K. GHOSE , 2 1 1Department of Geosciences, Center for Environmental P.J. ENG AND T.P. TRAINOR Molecular Science, Stony Brook University, NY 11794, 1Department of Chemistry and Biochemistry, University of USA (*correspondence: [email protected]) Alaska Fairbanks, Fairbanks, AK 99775-6160, USA ([email protected], [email protected], (*correspondence: [email protected]) [email protected]) ([email protected], [email protected]) 2Department of Chemistry, Stony Brook University, NY 2Consortium for Advanced Radiation Sources, University of 11794, USA Chicago, Chicago, IL 60637, USA
([email protected], [email protected]) Chromium is an important anthropogenic contaminant and its transport in the natural environment can be strongly Iron (hydr)oxides play a key role in iron biogeochemical affected by the occurrence of iron minerals. Cr(VI) can by cycling and act as one of the most important natural reduced by iron minerals to Cr(III), which is less toxic and scavengers of numerous contaminants primarily via adsorption mobile. Chromium(III) (oxy)hydroxide and mixed Cr(III)- reactions. Therefore, biological availability and transport of Fe Fe(III)-(oxy)hydroxides are known to have very low and aquatic contaminants is strongly influenced by stability solubilities and therefore are likely to be the fate-controlling and surface reactivity of iron oxides. The adsorption of Fe(II), phase of Cr(III) in natural environments. However, due to a highly soluble and common aquatic species, significantly their X-ray amorphous properties, little is know about their impacts the stability and surface reactivity of ferric actual structure. This study involves synthesis Cr(III)-Fe(III)- (hydr)oxides [1]. However, there is still limited molecular (oxy)hydroxides of different composition, and the use of TG- scale understanding of Fe(II) binding modes and surface DTA, FTIR, HRTEM, X-ray absorption spectroscopy (XAS), reaction pathways. and pair distribution function (PDF) analysis to evaluate their solid solution properties and their structure. The results In this study, the structure of hematite (0001) and (1102 ) provide new information on the speciation of Cr and surfaces are determined after reaction with Fe(II) using remediation methods based on the reduction of Cr(VI) to synchrotron based crystal truncation rod (CTR) X-ray diffraction. The results show surface bound Fe occupies Cr(III). crystallographic lattice sites on both hematite surfaces. TG-DTA results show that the Cr end member has a However, the geometry of adsorbed Fe complexes is different higher water content than the Fe end member, and show two on different surface, which highlights the importance of stages of weight loss probably related to loss of structural surface structure of underlying substrate. On both substrates water and/or hydroxyl groups. For Cr-Fe-(oxy)hydroxides, as the average Fe-O bond lengths of surface bound Fe are Cr content decreases, the temperature for dehydration characteristic of Fe(III). These observed Fe-O bond lengths decreases and the temperature for dehydroxylation increases. provide indirect evidence of oxidation of Fe(II) after Weight loss and chemical analysis give a possible chemical adsorption, which is consistent with recent studies indicating formula of Cr(OH)3•3H2O for the Cr end member. Fe(III) oxides are effective oxidants for dissolved ferrous ion Temperature resolved in situ X-ray diffraction study shows [2, 3, 4]. Overall, the structural understanding of incipient that the Cr end member converts to crystalline Cr2O3 at around Fe(II) adsorption on iron oxides will result in an improved 420°C. XAS and PDF analysis show that the Fe end member understanding of how Fe(II) affects structure, stability and is similar to nanocrystalline 2-line ferrihydrite with an average reactivity of iron oxides. particle size of 2 nm, and the Cr end member sizing around 1 nm is likely to be amorphous. Results show these compounds [1] Stumm & Sulzberger (1992) Geochim. Cosmochim. Acta are not simply physical mixtures of the end members because 56, 3233-3257. [2] Kerisit & Rosso (2006) Geochim. Cosmochim. Acta 70, 1888-1903. [3] Silvester et al. (2005) chemical substitution across the whole series was observed. Geochim. Cosmochim. Acta 69, 4801-4815. [4] Williams & Scherer (2004) Environ. Sci. Technol. 38, 4782-4790. Goldschmidt Conference Abstracts 2008 A933
Chemical and isotopic approach on Determining groundwater recharge an algae bloom in the Hongfeng Lake, based on isotope concentration Southwest China varying with pumping process 1 2 1 F.-X. TAO *, L. YIN AND H.-C. PIAO Y.Z. TAO* AND K.J. WANG 1State Key Laboratory of Environmental Geochemistry, School of Civil Engineering, Hefei University of Technology, Institute of Geochemistry, Chinese Academy of Sciences, Hefei 230009, China Guiyang 550002, China (*correspondence: [email protected]) (*correspondence: [email protected]) 2Guiyang Municipal Institute for Environmental Protection, Introduction Guiyang 550002, China ([email protected]) The Hexian iron mine is situated in Anhui province, east China. The iron deposit is distributed along the contact zone The trigger mechanism and normalization of precaution between Middle Triassic carbonate rock and volcanic rocks. indicators for algae bloom in freshwaters remains a challenge The hydrogeological condition of the mineral deposit very to scientific communities. Here, we present a chemical and complexity due to such three groundwater systems as isotopic approach on an algae bloom in the Hongfeng Lake unconfined groundwater in Quaternary porous aquifer, (a man-made drinking-water reservoir), based on a high- confined fissure water in Middle-upper Triassic sandstone, frequency sampling (daily to weekly) during a period from and confined karst water in Middle Triassic carbonate rock. August to December of 2007. The measured parameters Based on isotopic hydrogeology theory, this study focuses on includes: water temperature, pH, dissolved oxygen, the recharge of confined groundwater. chlorophyll α, NH3-N, total N, total P, algae biomass, dissolved inorganic carbon (DIC) content and carbon isotope Sampling and Results composition (δ13C), and C/N ratio of algae biomass. The Our sampling and analysis, combined with the existed particulate organic matter was completely supplied by algae local geological information, can be summarized concisely bloom, as indicated by its low C/N ratio (5.1-7.7). The DIC into the following steps: (1) one background sample of cycles were rapidly driven by the algae bloom. Its content unconfined groundwater was taken from Quaternary porous displayed a highly negative correlation with its δ13C value aquifer; (2)continuous pumping tests were carried out (Fig. 1). At the initial stage of algae bloom, the carbon source respectively in fissure aquifer and karst aquifer, the pumping for algal photosynthesis was atmospheric CO2, but at the time was more than 48 hours; (3) after 10 minutes pumping, remained stages it was provided by the oxidation of organic the background groundwater sample was taken; (4) one water matter. The algae bloom was N-limited, not P-limited. This is sample was taken every hour after 30 minutes pumping and in contrast to the fact that the eutrophication of most one water sample every two hours after 8 hours pumping; freshwater lakes is P-limited. The main factor to control the (5) oxygen and hydrogen stable isotopes in groundwater evolution of algae bloom was water temperature, as it was samples were measured; (6) based on the variations of isotope highly correlated with pH, NH3-N, total N, algae biomass, concentration during each well pumping process and 13 DIC and δ CDIC. combining the isotope concentration in background sample of each aquifer, groundwater recharge sources of each aquifer -4.0 3.5 were analyzed. DIC r = -0.65, p < 0.001 3.0 The results shows that: (1) recharge capability of confined -6.0
(‰) fissure water is poverty, pumping water mainly rely on 2.5 DIC fissure-aquifer dewatering after 4 hours pumping; (2) confined DIC
C -8.0
13 2.0 karst water can get continuous recharge from unconfined δ 13 δ C DIC groundwater during pumping; (3) the hydraulic connection -10.0 1.5 between fissure water and karst water is weak. 1 6 11 16 21 26 31 36 41 46 51 56 61 66 71
Sample No. The study is supported by the National Natural Science Aug. 9 Dec. 24 Foundation of China (40174050) and the Key Project in the National Science & Technology Pillar Program in the Figure 1: The negative correlation between DIC and its δ13C Eleventh Five-year Plan Period (2006BAB01B01). value. A934 Goldschmidt Conference Abstracts 2008
Thermal evolution of plutons in the The alleged carbonatitic-kimberlitic Questa caldera, NM melt continuum: Contrary evidence
1 2 1 M.J. TAPPA , M.J. ZIMMERER AND D.S. COLEMAN from West Greenland 1 2 1 1University of North Carolina-Chapel Hill ([email protected]) S. TAPPE *, A. STEENFELT , L.M. HEAMAN , 3 1 1 2New Mexico Institute of Mining and Geology, Socorro, NM R.L. ROMER , A. SIMONETTI AND K. MUEHLENBACHS
1Department of Earth and Atmospheric Sciences, University New evidence suggests pluton emplacement during of Alberta, Edmonton, Canada caldera complex formation is a dynamic process with multiple (*correspondence: [email protected]) chambers that potentially were emplaced incrementally. 2Geological Survey of Denmark and Greenland Zircon U/Pb and Ar/Ar high-resolution geochronometry from 3Geoforschungszentrum Potsdam, Germany minerals with different closure temperatures were used to determine detailed thermal histories for two subvolcanic Conventional wisdom dictates a genetic relationship plutons, the Cabresto Lake pluton (CL) and the Rio Hondo between carbonatite and kimberlite, and Dalton & Presnall [1] pluton (RH) of the Latir Volcanic Field (LVF), northern New proposed that these magma types may be related by an Mexico. The majority of LVF plutons lie within the rim of the increasing degree of partial melting of carbonated peridotite. mid-Tertiary Questa caldera. Single-crystal laser-fusion They suggested that the Sarfartoq carbonatite complex of sanidine Ar/Ar geochronology of the caldera-associated West Greenland (ca. 600-550 Ma), which comprises dolomitic volcanic sequence was used to understand stratigraphy of units carbonatite sheets and carbonate-rich ultramafic silicate dykes unresolved by field relations, and to correlate volcanic and (aillikites), represents the best natural analogue for their plutonic episodes. experimentally produced primary melt continuum at 6 GPa. Preliminary results indicate two new insights into pluton Major problems arise with this model: (i) new U-Pb ages intrusion in the LVF: 1) A significant change of cooling rates indicate that the ultramafic magmas started to form at least 10 from the nearly syn-caldera (~25 Ma) CL and the post-caldera m.y. earlier than the carbonatite; (ii) Sarfartoq carbonatites (~23 Ma) RH. The extremely fast cooling rate of the CL differ compositionally from the experimentally produced correlates well with the timing of maximum Rio Grande rift primary carbonatite melts. crustal extension, and the resurgent nature of the pluton. The In 2005, a similar carbonatite-aillikite intrusive suite was slow cooling rate of the RH possibly indicates multiple discovered at Tikiusaaq (ca. 165-150 Ma) south of Sarfartoq intrusions to sustain high temperatures (>300°C) sufficient and provides a new test case for the melting continuum enough to eclipse the closure temperature of biotite without hypothesis. Like at Sarfartoq, the Tikiusaaq aillikite dykes exceeding the zircon saturation temperature. Multiple samples predate the carbonatite sheets by ca. 5-10 m.y. Petrological of the RH yield concordant yet differing U/Pb ages outside and geochemical data suggest that aillikite is close to primary analytical uncertainty of 23.0 (± 0.1) and 22.7 (± 0.1) Ma. magma composition, whereas the carbonatite body represents This is consistent with field evidence that suggests the RH is differentiated magma and cumulates. Sr-Nd-Pb isotope an incrementally assembled body. 2) Ar/Ar dating reveals compositions of the Tikiusaaq aillikites and carbonatites oscillations in the composition of precaldera volcanic units overlap and indicate magma origin from a common ranging from calc-alkaline to alkaline before cumulating in the carbonated upper mantle source. However, some carbonatites peralkaline eruption of caldera forming ~500 km3 Amalia Tuff show a pronounced shift towards compositions typical for the (~25.22 Ma). Each volcanic unit provides a snapshot in time Archean crust of West Greenland. This crustal component was of magma chamber composition, and requires multiple most likely attained by fluid exchange during magma chambers to explain the oscillations in the composition of the emplacement. We favour a model in which a proto-aillikite erupted products. The slowed pluton cooling rate and magma is parental to dolomitic carbonatite and suggest that alternating volcanic sequence requires multiple chambers that the differentiation process was mainly controlled by volatile potentially were incrementally emplaced. build-up at crustal pressures. Despite the fact that a primary carbonatitic-kimberlitic melt continuum exists in high-P experiments [1], the geology and petrology of central-complex carbonatite intrusions in West Greenland and elsewhere fail to support this hypothesis.
[1] Dalton & Presnall (1998) J.Petrol. 39, 1953-1964. Goldschmidt Conference Abstracts 2008 A935
Alkaline and carbonatite intrusives Inverse carbon isotopic trend in help to unravel the temporal hydrocarbons from hydrothermal evolution of a cratonic rift in the fluids of Socorro Island, Mexico 1 2 North Atlantic region YURI TARAN * AND EDITH CIENFUEGOS S. TAPPE 1Instituto de Geofisica, UNAM, Mexico D.F., 04510, Mexico (*correspondence: [email protected]) Department of Earth and Atmospheric Sciences, University of 2Instituto de Geologia, UNAM, Mexico D.F.,04510, Mexico Alberta, Edmonton, Canada ([email protected])
Socorro Island, the biggest of the Revillagigedo The Labrador Sea is a small ocean basin in the North Archipelago, is a part of the Mathematician Ridge, a former Atlantic realm that cuts through the Archean cratonic EPR after a jump ~ 3Ma to its present location. Fumarolic lithosphere of Labrador and Greenland. While the onset of steam (96ºC) of Everman volcano at the island is enriched in sea-floor spreading has been determined at ca. 60 Ma [1], the H and CH (10 and 3.5 vol% in dry gas) with 3He/4He = preceding rifting stages are poorly constrained mainly due to 2 4 7.6Ra, H /H O ≈ 100, CO /H ≈ 8; H /CH ≈3 and the inaccessibility of the offshore sedimentary basins and the 2 2 2 2 2 4 650
[1] Chalmers & Laursen (1995) Marine & Petroleum Geology 12, 205-217. [2] Tappe et al. (2007) EPSL 256, 433-454. A936 Goldschmidt Conference Abstracts 2008
Whole-rock geochemistry and Sr-Nd Making continental crust: isotopic evidences for sources and The sanukitoid connection
processes of granulite formation in YOSHIYUKI TATSUMI Ribeira Belt, Brazil Institute for Research on Earth Evolution (IFREE), Japan 1 2 2 Agency for Marine-Earth Science and Technology C. TASSINARI , T. BENTO DOS SANTOS *, J. MUNHÁ 2 (JAMSTEC), Yokosuka 237-0061, Japan AND P. FONSECA ([email protected]) 1Instituto de Geociências, Universidade de São Paulo, Brazil 2Centro/Departamento de Geologia, Universidade de Lisboa, The average continental crust possesses intermediate Portugal (*correspondence: [email protected]) compositions that typify arc magmatism and as a result it is believed to have been created at ancient convergent plate Elemental and Sr-Nd isotopes data on migmatites, boundaries. One possible mechanism for intermediate granulites and orthogneisses obtained from the central part of continental crust formation is the direct production of Ribeira Belt (SE Brazil) shows that they are LILE-enriched andesitic melts in the upper mantle. Sanukitoids, which weakly peraluminous granodiorites. Harker trends for TiO2, characterize the Setouchi volcanic belt, SW Japan, include t t Al2O3, Fe2O3 , MgO, P2O5, Sr, Zr, Hf, Th, U, REE , unusually high-Mg andesites (HMA). They were generated by LREE/HREE and La/Lu, as well as incompatible element slab melting and subsequent melt-mantle interactions under trends of Th-Hf-La suggest that these rocks represent a co- unusual tectonic settings such as where warm lithosphere genetic sequence. Similar REE patterns and juxtaposed subducts into hot upper mantle. Such conditions would have 575 87 86 isotopic values of εNd = -5.4 to -7.3 and Sr/ Sr575 = 0.706 existed in the Archean. Hydrous HMA magmas are likely to to 0.711 for granulites, orthogneisses and migmatites is have solidified within the crust to form HMA plutons, which consistent with hypothesis that these rocks evolved from a were then remelted to produce differentiated sanukitoids. relatively homogeneous and enriched common crustal (meta- At present generation and differentiation of HMA magmas sedimentary) protolith. Results suggest that partial melting of may have been taking place in the Izu-Bonin-Mariana arc- meta-sediments formed migmatites and associated granitoid trench system (IBM), because (1) HMA (boninite) magmatism bodies, whereas long-term crustal slow cooling promoted characterizes the initial stages of the IBM evolution and further dehydration (re-melting) that led to development of (2) the IBM middle crust exhibits Vp (6.0-6.5 km/s) identical widespread granulites [1]. to that of the bulk continental crust. Vp estimates for plutonic Sm-Nd TDM ages span from 2.0 to 1.5 Ga is consistent rocks with HMA compositions support this; especially, the with Paleo- and Mesoproterozoic contributions to the observed Vp of the middle crust, which forms the present sedimentary pile that was metamorphosed during the assembly forearc crust and is likely to be created during the early stage of Gondwana. TDM ages and paleogeographic proximity of the arc evolution, is best explained by the lithology of suggest that the São Francisco and West Congo Cratons are HMA pluton. However tonalitic composition for middle-crust- the most probable sources for these protoliths. Sm-Nd model forming rocks cannot be ruled out, especially for the presently ages and inherited zircon SHRIMP dating [2] concordance active volcanic arc, suggesting an alternative possibility that reveals that the protoliths were part of a juvenile crust formed the continental crust has been created by differentiation of 2.0 to 1.5 Ga ago, whereas the absence of Pan-African TDM mantle-derived basaltic magmas. ages suggests zircon sedimentary reworking with U-Pb isotopic homogenization of older zircons. This means that during Pan-African times no significant new crust was added, which, combined with the new geochemical model for granulite formation in the studied area, contradicts poli- orogenic scenarios formerly proposed for the evolution of Ribeira Belt.
[1] Bento dos Santos et al. (2007) Geochimica et Cosmochimica Acta 71, 15, Sup. 1, A79. [2] Valladares et al. (in press) Gondwana Research 2007. Goldschmidt Conference Abstracts 2008 A937
Calc-alkalic vs. tholeiitic revisited: C-isotope exchange experiments A radical view of andesite genesis between DIC and TCE 1 1 1 1 2 1 Y. TATSUMI *, T. TAKAHASHI , Y. HIRAHARA , H. TAUBALD *, C. SCHÜTH AND M. LINK 1 1 2 3 T. MIYAZAKI , Q. CHANG , J.-I. KIMURA , M. BAN 1 4 University of Tübingen, Institute of Geosciences, Wilhelmstr. AND A. SAKAYORI 56, D-72074 Tübingen, Germany 1IFREE, JAMSTEC, Yokosuka 223-0061, Japan (* correspondence: [email protected]) 2 (*correspondence: [email protected]) Technical University of Darmstadt, Inst. Appl. Geoscience, ([email protected], [email protected], Schnittspahnstr. 9, D-64287 Darmstadt, Germany [email protected], [email protected]) 2Shimane University, Shimane 690-8504, Japan Introduction ([email protected]) Isotope fractionation of organic carbon during degradation 3Yamagata University, Yamagata 990-8560, Japan of contaminants is an important tool to quantify natural ([email protected]) attenuation [1], but the role of coexisting inorganic carbon 4Kanazawa University, Kanazawa 920-1192, Japan (DIC) in this process has been regarded to be neglegible. ([email protected]) Recent studies [2], however, did not corroborate this theory and made it evident that the behaviour of C isotopes between Two distinctive differentiation trends, tholeiitic (TH) and TCE and DIC should further be studied. We report new data calc-alkalic (CA), are recognized in subduction zone magmas. from triplicate sets of exchange experiments in sealed vessels, 13 TH and CA andesites to dacites often coexist in close temporal using conventional TCE, Na2CO3 and NaHCO3 as well as C and spatial proximity. The genetic relation between these two labelled Na2CO3 and NaHCO3 in solution with concentrations types of andesitic magmas should be solved for better ranging from 0.1 to 10 mmol/l, temperatures from 20 to 60°C understanding the andesite genesis. and experiment time from 10 – 100 days. Blank sample sets Sr-isotope micro-analyses, using a combined were performed accordingly. micromilling/TIMS and an in situ LA-MC-ICPMS, were conducted on plagioclase phenocrysts from CA and tholeiitic Results TH andesites from the Quaternary Zao Volcano in the NE Experiments performed at 20°C showed no enrichment of 13 Japan arc. 87Sr/86Sr of plagioclase occurring in TH rocks is C in TCE, even for highest DIC/TCE ratios, and 100 days constant at 0.70428±0.00005 and show little correlation with experiment time. A decrease in TCE concentration over the An-content, whereas that for CA rocks varies from experiment time could be observed, but due to experimental 0.70337 to 0.70418 and shows more complex characteristics. setup not be quantified. GC-IRMS measurements could not 13 The observation that high-An plagioclase embedded in the identify any degradation product of TCE and δ CPDB values most mafic CA basaltic andesites exhibits the lowest 87Sr/86Sr for residual TCE ranged, within analytical uncertainty, should be stressed. These results may not be consistent with a between -23±2‰. At 60°C similar results were obtained, with general consensus that the major mechanisms of TH and CA two exceptions: both data sets using Na2CO3 and andesite production are fractional crystallization of a mantle- concentrations of 10mmol/l showed significant C-isotopic derived TH basaltic magma and mixing between TH basaltic enrichment of TCE after 30 days with final δ-values of -7‰ and crust-derived felsic magmas, respectively. Instead, two after 100 days. The amount of enrichment correlates with the isotopically distinct basaltic magmas could form beneath the DIC/TCE ratio and surprisingly this effect can be observed for 13 volcano, one for the TH series produced by anatexis of the C-enriched but also for natural Na2CO3 solutions. pre-existing, hence more radiogenic mafic lower crust, and other for the CA series by partial melting of less radiogenic Discussion mantle wedge peridotite. A mantle-derived CA basaltic The data suggest that at normal groundwater temperatures magma will mix with crust-derived TH melts to form CA there is no C-isotope exchange between DIC and TCE. We 13 andesites. attribute the observed shift of δ C values in natural and enriched Na2CO3 solutions to hydrolysis of TCE, triggered by high pH values of 11,4 in the10mmol/l Na2CO3 solutions and by elevated temperatures of 60°C.
[1] Prommer et al. (2007) doi,10.1016/j.jconhyd.2007.11.003. [2] Taubald & Schüth (2004) GCA, 68, 11S, A459. A938 Goldschmidt Conference Abstracts 2008
Behavior of rock-forming minerals Oxygen exchange in Olivine
1 2 3 under simulated and actual S. TAYLOR , Y. GUAN AND G. MATRAJT lung conditions 1USACRREL, 72 Lyme Road, Hanover NH 03755 2 ([email protected]) ANNE TAUNTON, MICKEY GUNTER AND SCOTT WOOD 2Geol. & Planet. Sci, Caltech Pasadena, CA 91125 Department of Geological Sciences, University of Idaho, ([email protected]) 83844-3022 ([email protected], 3Dept. of Astronomy, University of Washington, Seattle WA [email protected], [email protected]) 98105 ([email protected])
Theoretical and experimental data suggest that secondary Micrometeorites, 30µm to 2mm extraterrestrial particles, minerals form in the lung. Reaction-path modeling for various are heated to varying degrees entering the Earth’s atmosphere. rock forming minerals under physiologic conditions in a lung- Heating, melting and volatilization can change their chemical fluid simulant gives dissolution times for these minerals as: and isotopic composition; mass dependant isotopic calcite < chrysotile < anorthite < K-feldspar < talc < fractionation is seen in severely heated micrometeorites [1]. muscovite = kaolinite = albite = quartz. For each mineral We are interested in determining whether oxygen isotopic reaction, hydroxylapatite and other secondary minerals were exchange during atmospheric entry could also alter a predicted to precipitate. Batch experiments using lung-fluid micrometeorite’s oxygen isotopic composition. stimulant and a brucite/chrysotile mineral mixture confirm that To determine if a heated minerals exchanges oxygen with hydroxylapatite forms during reactions in simulated lung-fluid the atmosphere we heated grains of an olivine standard while other minerals dissolve. SEM analysis of human lung (174-1) for 30 s, 1min. and 2 min. at 1450°C. The tests were tissue also confirms the formation of calcium phosphates in done at atmospheric pressure and the olivine grains introduced human lung tissue. Pleural plaques from 11 baboons involved into a muffle furnace in a quartz tube. The heated olivines, and in an inhalation study were examined using SEM, EDS, and some unheated ones, were then mounted in epoxy, sectioned powder XRD. XRD analysis revealed apatite in pleural and 18O and 16O were measured from the rim to the core of the plaques of six baboons. SEM-EDS analysis found small grains using the Cameca ims 7f-Geo at CalTech. quantities of apatite in three additional baboons. XRD analysis Our results show no difference between the heated identified calcite in two baboons and talc in baboons exposed (δ18O =4.8 ± 0.6‰, n=25) and unheated grains or between the to high doses of glass fibers, chrysotile, and grunerite. XRD centers (δ18O =4.8‰) and the rims (δ18O =5.0‰) of the heated analysis detected 2:1 expandable clays in baboons exposed to olivines within measurement error (δ18O =0.7‰). The olivine high levels of glass fibers, chrysotile, grunerite and riebeckite. which was originally light green became orange and then dark XRD also detected amphiboles in baboons exposed to high brown with increased heating time. These particles did not levels of grunerite and riebeckite. SEM-EDS analysis revealed melt, the melting point for forsteritic olivines ~1890°C is Mg-rich silicates in a control baboon and one baboon exposed higher than our maximum furnace temperature, but their color to low doses of chrysotile. Asbestos bodies were detected in change suggests that magnetites formed near the surface from baboons exposed to high levels of grunerite and chrysotile. iron in the olivine. Iron-rich silicate fibers without coatings were identified in the Next we plan to analyze single mineral olivine baboon exposed to high levels of riebeckite using SEM-EDS. micrometeorites that show heating effects at their periphery Because minerals other than those to which the baboons were (Fig. 1). We expect micrometeorites that exchanged oxygen exposed were detected in many of the baboons, the hypothesis with the atmosphere to have an oxygen isotopic composition that secondary minerals may form from primary mineral approaching δ18O = 23.5‰, the atmospheric value [2]. dissolution in the lung should be considered when addressing the health effects of minerals.
[1]Alexander et al. (2002) Geochim et Cosmochem Acta 66, 173-183. [2] Thiemens et al. (1995) Science 270, 969–972. Goldschmidt Conference Abstracts 2008 A939
Surface Nd isotopic distribution in Extent of Indian MORB mantle the South Pacific Ocean domain during the Cretaceous: 1 1 1 HIFOFUMI TAZOE , HIROMI SATO , HISAO NAGAI , Geochemistry of basement rocks in 2 2 HAJIME OBATA AND TOSHITAKA GAMO Luzon, Philippines 1 College of Humanities and Sciences, Nihon University, 1 1 1 M.L.G. TEJADA , C.A. BELZA , C.A. ARCILLA , Tokyo, Japan ([email protected]) 1 1 2 M.I.R BALANGUE-TARRIELA , R. RODOLFO AND Ocean Research Institute, the University of Tokyo 2 P.R. CASTILLO
Nd isotopic distribution in surface waters was controlled 1NIGS, University of the Philippines, Diliman, Quezon City, by surrounding terrestrial sources, lateral transportation and Philippines ([email protected]) mixing water masses. In the North Pacific Ocean, Nd isotopic 2Scripps Institution of Oceanography, University of compositions reflect weathering of island arcs around the California, San Diego, La Jolla, San Diego, USA circum-Pacific and show more radiogenic than those in the Atlantic and the Indian Ocean. In the South Pacific Ocean, We examined Cretaceous and Eocene groups of basalts however, Nd isotopes in seawater and their sources have not and peridotites from ophiolitic complexes in Luzon, been investigated yet. The New Guinea Island and Philippines and found out that they possess Nd, Pb, and Sr neighboring volcanic island were expected as mantle-derived isotope compositions similar to those of Indian Ocean mid- sources in the South Pacific Ocean. On the other hand, ocean ridge basalts (MORB). Each group is isotopically unradiogenic Nd (εNd < -9) in the Southern Ocean could distinct from Pacific MORB and the younger group contribute as continental-derived sources. additionally has stronger subduction-influenced chemical We examined Nd isotopic distribution and its sources in signature. The Indian MORB-type isotopic signature in these surface waters of the South Pacific and the Southern Ocean. rocks is shared by the Philippine plate basin lavas [1] and Seawater samples were collected by MnO2 impregnated fiber Philippine arc volcanics [2], believed to have been imported on the transects along 170ºW and 155ºE. These transect lines from their previous southern location within the modern-day were set to observe from the Southern Ocean to the equatorial region of DUPAL anomaly [1, 2]. Recent detailed Pacific Ocean. paleomagnetic data [3] suggest substantial northward According to Nd isotopic distribution in the South Pacific movement from equatorial latitudes of both the Cretaceous and the Southern Ocean, oceanic regions were divided into the and Eocene rock groups, corroborating the interpretation that most radiogenic Coral Sea (-1.6 < εNd < +0.4), Tropical South Luzon formed part of the oceanic basement of the Philippine Pacific Ocean (-3.6 < εNd < -1.6), unradiogenic Southern Sea Plate (PSP) [3, 4]. Our results suggest that both the PSP Ocean (εNd ≈ -9) and the middle latitude region (-8.2 < εNd and the Cretaceous basement rocks of Luzon originated from < -0.9). Each division corresponds to a major water mass in the same mantle source and, if true, imply that: (a) the Indian surface water. In the Tropical region, εNd values in the Coral MORB-type mantle component may have been present in the Sea were more radiogenic than those along the 170ºW. sub-Philippine mantle since the Cretaceous and (b) the Indian Inflows to the Coral Sea from the South Equatorial Current MORB mantle domain may have extended as far north as the showed the feature of mantle-derived Nd in the western South equatorial latitudes since the Cretaceous. Pacific Ocean. Heterogeneous εNd distribution in the Coral Sea probably suggested various mantle-derived Nd sources not [1] Hickey-Vargas (1991) Earth Planet. Sci. Lett. 107, 290- only the New Guinea Island but also other volcanic islands 304. [2] Castillo (1996) Geology 24, 271-274. [3] Queano et such as Bismarck Islands and Solomon Islands. In the Polar al. (2007) J. Geophys. Res. 112, doi,10.1029/2006JB004506. Frontal Zone and Antarctic Zone of the Southern Ocean, Nd [4] Pubellier et al. (2003) Tectonophysics 363, 181-199. isotopic compositions were unradiogenic and homogenous distribution between 54º S and 67.5ºS. Although surface salinity abruptly changed (33.8 - 34.7) at the Suantarctic Front (48º–51ºS), εNd values gradually increase from poleward of the Subantarctic Front (52ºS, εNd = -8.2) to 25ºS (εNd = -0.9). This gradient resulted in the mixing of the water mass having radiogenic Nd from the Coral and Tasman Sea with unradiogenic Southern Ocean. A940 Goldschmidt Conference Abstracts 2008
Mineralogical and geochemical Silica deposition on cells in characteristics of volcanic rocks from environmentally defined Eskişehir, Northwest Anatolia, experimental solutions 1 2 2 Turkey: Preliminary results A.C. TENESCH , M. DIETRICH , S.L. CADY , 1 1 1 1 2 C.E. BLANK AND N.W. HINMAN S. TELSIZ *, A.TEMEL AND A. GOURGAUD 1Geosciences Department, University of Montana, Missoula, 1Hacettepe University, Department of Geological Engineering, MT 59812 06800, Beytepe-Ankara, Turkey 2Department of Geology, Portland State University, Portland, (*correspondence: [email protected]) OR 97201 ([email protected])
2Université Blaise Pascal, OPGC, Laboratoire CNRS Ancient microfossils that display the highest “Magmas et Volcans” 5 rue Kessler-63038, Clermont- morphological fidelity are preserved in siliceous sedimentary Ferrand Cedex, France rocks. Experimental solutions based on silica speciation in ([email protected]) Yellowstone hot springs were used to constrain the
geochemical conditions that favour microfossil formation; Eskişehir volcanic field in the Northwest Anatolia, mainly experimental silicification conditions matched natural solution comprised of lavas and pyroclastics, has been characterized by in that the dominant species was aqueous silica as opposed to alkaline composition. The lavas range in composition from deprotonated or polymerized forms of silica. Experimental basanite through trachybasalt and basaltic trachyandesite to solutions that contained Bacillus subtilis were sequestered trachyandesite. The pyroclastic rocks observed as pyroclastic from a common solution reservoir in cellulose dialysis bags. fall and flow (ignimbrites) deposits, and they are rhyolitic in Reservoir solutions contained between 0 and 400 mg/L SiO composition. Based on mineralogical studies, lavas consist of 2 with or without dissolved Fe or Al. A statistical comparison of olivine (Fo ), clinopyroxene, plagioclase, amphibole, 72-86 the length-to-width aspect ratio of cells in the controls orthoclase, amphibole, biotite minerals, and oxides (without silica or metals) and cells in the experiments with (Ti-magnetite). The basanites, different from the other lava different concentrations of silica (no metals) showed that the types, have nefeline normative. Normally zoned morphology of treated uncollapsed cells changed throughout clinopyroxene minerals are named as augite-diopside the experiment. Cell morphology also differed for experiments (Wo ) based on Moritomo [1] classification. Plagioclase 37-45 with silica and either iron or aluminum. In spite of the osmotic minerals are labradorite-bitovnite (An to An ) in 50 80 differences expected for treated and untreated solutions, we composition. Variation diagrams of SiO with major and trace 2 found that cells remained intact for the duration of the elements are consistent with fractional crystallization process. experiments with low silica concentrations (no metals). The Eskişehir lavas and ignimbrites are characterized by However, to retain cell shapes for the duration of experiments enrichment in LILE and LREE, relative to HFSE, and HRE with higher silica concentrations required the addition of Al elements. They show slight negative Nb, Ta, and Ti anomalies and Fe. Silica accumulation on cells was observed for all which are characteristics of the subduction and/or crustal treated solutions, and differed when iron and aluminum were contamination related suites. Differently, the basanites with present, which suggests that silica accumulated differently on OIB-like trace element patterns, and high Nb/La>1, high cells in the presence of metals than in their absence. Nb/U~40 ratios, they can be evolved from a mantle source that have no subduction and crustal contamination effects.
[1] Morimoto (1989) Can. Mineral 27, 143-156. Goldschmidt Conference Abstracts 2008 A941
Interface induced crystallization of Unravelling complex magmatic carbonate polymorphs processes using amphibole: 1 2 3 3 H. HENRY TENG , YU LIN , JUNFENG JI AND JUN CHEN A case study from El Misti, Peru 1 2 2 1Department of Chemistry, The George Washington F.J. TEPLEY III *, S.L. DE SILVA AND G. SALAS University, Washington, DC 20052 1College of Oceanic and Atmospheric Sciences, Oregon State 2Department of Geological & Environ. Sci., Stanford University, Corvallis, OR 97331-5503 USA University, Stanford, CA 94305 (*correspondence: [email protected]) 3Department of Earth Sciences, Nanjing University, Nanjing, 2Department of Geosciences, Oregon State University, Jiangsu, 210093, PRC Corvallis, OR 97331-5506 USA
([email protected], Carbonate polymorphs occur widely in geological and [email protected]) biological environments. A number of external factors, particularly the presence of organic and biological molecules The prominent role of amphibole in arc magmatic systems and templates, are known to be able to effectively direct the has gained renewed focus of late. We report on a study of the crystallization of specific carbonate polymorphs. Here, we 2000 BP eruption of El Misti in Peru in which juvenile blocks conducted crystallization experiments to explore whether reveal heterogeneous crystal populations. Plagioclase crystals minerals through the presence of surface functional groups can suggest multiple populations and generations of antecrysts and selectively induce the crystallization of carbonate polymorphs. phenocrysts. Amphiboles appear to be more restricted and Three types of minerals, simple oxide, framework represent two distinct populations of phenocrysts implicating aluminosilicate, and phyllosilicate, were used in this study. the intimate mingling of two magmas; an amphibole- Experimental results demonstrate that minerals indeed have plagioclase rhyolite and amphibole-plagioclase andesite. the ability to influence carbonate polymorphic formation. For Amphiboles in the rhyolites are dominantly pargasitic, with simple metal oxides, it appears that their polymorphic rare ferro-edinites. They contain relatively low AlIV ~1.8, have selectivity is related to the minerals’ surface charge Mg#’s of <70, and are rimmed by reaction products. conditions. Specifically, negatively charged surfaces favor the Amphiboles in the andesite are also dominantly pargasitic and formation of non-calcite polymorphs while zero or positive broadly similar to those in the rhyolites, however some cores charges are more selective for calcite. The charge-polymorph have lower AlIV ~1.7, but higher Mg#’s of 74-75. All crystals relationship is supported by the results of phyllosilicate in the andesite are euhedral and slightly zoned, but do not experiments, but does not fit to interpret the behavior of contain reaction rims. These characteristics present a silicon oxides. Whereas the presence of permanent structural conundrum; broadly similar amphiboles are found in charges on phyllosilicates may have facilitated the equilibrium with two liquids of quite different composition crystallization of non-calcite polymorphs, calcite is the that were erupted simultaneously after the two magmas dominant polymorph in silicon oxide experiments despite the mingled, yet only the amphiboles in the rhyolite show reaction negatively charged substrate surfaces. The discrepancy may be rims. We will present new results of trace element analyses of related to the more significant dissolution of SiO at alkaline 2 amphibole cores and rims using laser ablation ICP-MS conditions under which carbonate crystallization take place, as techniques that will address the origin of the two populations suggested by the observations on K-feldspar that show of amphiboles and the petrogenesis of the system. amorphous SiO2 coating induces preferential formation of calcite. A942 Goldschmidt Conference Abstracts 2008
Historical ore processing in Idrija: Evolution of the Southern Ethiopian Case study of a unique mercury Rift System: Constrained from waste disposal site geochronological and geochemical 1 1 2 T. TERŠIČ *, M. GOSAR AND H. BIESTER data of mafic lavas of Amaro and 1Geological survey of Slovenia, 1000 Ljubljana, Slovenia Yabello areas (*correspondence: [email protected]) D.B. TESFAYE*, R. TANAKA AND E. NAKAMURA ([email protected]) 2Technical University Braunschweig, 38106 Braunschweig, The Pheasant Memorial Laboratory, Institute for Study of the Germany ([email protected]) Earth’s Interior, Okayama Univ., Misasa, 682-0193, Japan (*correspondence: [email protected]) The production of mercury in Idrija started in 1492. In the first decade of mercury mining in Idrija the ore was roasted in We present new K-Ar age and comprehensive piles. After that the ore was roasted for 150 years, until 1652, geochemical dataset for mafic lavas of Amaro and Yabello in earthen vessels at various sites in the woods around Idrija. areas from southern Ethiopia, where the earliest manifestation Up to now 21 localities of ancient roasting sites have been of basaltic volcanism in the East African Rift System (EARS) established on the neighbouring hills and in more distant is recognized. Based on the K-Ar data, basaltic lavas in localities [1]. southern Ethiopia can be classified into five stages: Stage-1 Roasting of ore in piles and in earthen vessels gave a very tholeiitic and transitional basalts at 28-39 Ma, Stage-2 basalts poor yield and resulted in considerable losses. Because of the to basaltic trachyandesites at 11-17 Ma, Stage-3 basanites at high temperatures usually a third of earthen vessels cracked 7-8 Ma, Stage-4 tholeiitic basalts at 3-4 Ma, and Stage-5 during burning and mercury escaped from the vessels. Large basanites and alkaline basalts at <1 Ma. The thickness of quantities of broken pottery (up to 2 m) can be found at the Stage-1 tholeiitic and transitional basalts increases towards the localities of old roasting sites. The concentrations of Hg at NW-SE trending Mesozoic graben system of northwest Kenya those places are, of course, very high (up to 7,474 mg/kg). The to the south-west Ethiopia, suggesting they were formed by determined mercury contents in soils at old roasting sites are extension in this graben system. Most of these tholeiitic and very high, and they surpass all hitherto described localities at transitional lavas show distinctively low εHf and εNd and high Idrija and in its surroundings [2-4]. 87Sr/86Sr values and low Ce/Pb and high Ba/Nb ratios which Pšenk is one of the larger localities of roasting vessels possibly can show the affect of crustal contamination fragments. The investigated soil profile Pšenk contains at top a associated with thick crust prior to the initiation of the EARS. 45 cm thick humic layer with 4,000 to 5,000 mg/kg Hg. The cessation of the NW-SE rift activity was followed by Deeper mercury contents decrease to around 100 mg/kg Hg. northward and southward rift propagations, forming Stage-2 The calculations result in an estimated amount of 1.4 t Hg still and -3 lavas respectively. The Stage-2 alkaline lavas have present at the Pšenk locality. The Hg-thermo-desorption characteristically radiogenic Pb isotopic signature than the curves [5] indicate the presence of mercury in the form of Stage-3 basanites. The continuation of the southward rift cinnabar and that of mercury bound to organic matter. The propagation resulted in the formation of Stage-4 tholeiitic amount of the non-cinnabar fraction is important since it is basalts which have less radiogenic Pb and high εHf and potentially bioavailable and results are needed for further risk 87Sr/86Sr compositions similar to the least contaminated Stage- assessment studies. A detailed geochemical survey is being 1 tholeiitic basalts. It was followed by Stage-5 alkaline basalts carried out to evaluate the extent of the pollution at old and basanites in the northern and southern part, respectively roasting sites and to determine the changes in mercury along active border faults. Consequently, the southern speciation and transport through centuries. Ethiopian volcanic province can be interpreted as the intersection of three rift systems. The petrological and [1] Gosar & Čar (2006) Geologija 49(1) 91. [2] Biester et al. geochemical characteristics of mafic lavas in these rift systems (2000) Environ. Sci. Technol. 34(16) 3330. [3] Gosar et al. had been controlled by variable degree of partial melting of (2006) Sci. Total. Environ. 369(1/3) 150. [4] Kocman et al. heterogeneous asthenospheric mantle associated with (2004) J. Environ. Monit. 6, 696. [5] Biester & Scholz (1997) fluctuation of extension in each rift system. Environ. Sci. Technol. 31, 233-239. Goldschmidt Conference Abstracts 2008 A943
Characterization of atmospheric dust Evolution of Arsenic mineralogy in the Gulf of Aqaba through sulfide oxidation at the Ketza 1 1,2 3 NADYA TEUTSCH *, YEALA SHAKED , URI DAYAN , River mine, Yukon, Canada 1 4 1 BOAZ LAZAR , MORDECHAI STEIN AND YIGAL EREL Y. THIBAULT* AND D. PAKTUNC 1Institute of Earth Sciences, the Hebrew University of CANMET, 555 Booth Street, Ottawa, ON, K1A 0G1, Canada Jerusalem (*correspondence: [email protected]) (*correspondence: [email protected]) ([email protected]) 2The Inter-University Institute for Marine Sciences Laboratory The evolution of As-bearing minerals during sulfide in Eilat ([email protected]) oxidation was characterized in detail using samples from drill 3Department of Geography, the Hebrew University of cores and outcrops at the Ketza River mine. Jerusalem ([email protected]) Pristine gold-bearing sulfide samples consist mainly of 4The Geological Survey of Israel ([email protected]) arsenopyrite, pyrite and pyrrhotite. Arsenopyrite is the main
As-bearing phase. Pyrite contains less than 300 ppmw As. It has been extensively documented that atmospheric dust Observations from partially oxidized rocks reveal that is a major source of nutrients to the open sea and major pyrrhotite is the least stable sulfide typically replaced by a oceanic gyres. However, the contribution of airborne material mixture of FeS and iron oxyhydroxide followed by pyrite that to the nutrient budget of coastal marine environments was 2 oxidizes mainly to iron oxyhydroxide. Adsorbed arsenic usually neglected because their supply from continental content of the iron oxyhydroxide in these partially oxidized surface runoff was considered adequate. The Red Sea is a sea samples is typically low (< 2 wt%), confirming that most of located in an extremely arid region with virtually no runoff the arsenic is still retained in the pristine arsenopyrite. input, and therefore provides an ideal site to investigate the However, when pyrite oxidation occurs in contact with role of airborne dust in nutrient budget. The major objective of chlorite, there is localized formation of a Fe-aluminosilicate this study is to quantify the role of atmospheric dust in the phase showing a strong affinity for As with contents up to 6 nutrient balance of the oligotrophic waters of the Gulf of wt%. This crystalline phase has a well-defined chemistry with Aqaba (northern Red Sea). This quantification is needed for equal molar amounts of arsenic and phopshorous suggesting the estimates of the sources of "new" production during that both may occupy specific structural sites. summer stratification in this marine environment. In contrast to the iron sulfides, destabilization of Weekly samples of suspended dust have been collected arsenopyrite is late and associated with a major oxidizing continuously for more than two years in the northwestern event, most likely in an acidic environment, that redistributed corner of the Gulf of Aqaba, on the pier of the Interuniversity most of the arsenic in large continuous scorodite aggregates. Institute for Marine Sciences, Eilat, Israel. After collection, When in contact with muscovite-rich areas, numerous small samples underwent sequential dissolution in order to dissolve crystals of jarosite with As content up to about 5.5 wt% are first water-soluble salts, then carbonates and oxides, and formed locally within scorodite. In some instances, small finally Al-silicates. Dust load vary seasonally from low values crystals of Bi arsenate (BiAsO ) are also observed. Complex in the late summer to higher values in the fall, and highest 4 assemblages of iron oxyhydroxides (goethite, lepidocrocite, values in the early spring. The mineral fraction in the dust is amorphous) in oxidized rocks contain up to 10 wt% of As. composed mostly of carbonates, Al-silicates (mostly clays), Characterization of an auriferous oxidized ore sample and quartz. Occasionally the dust samples contained elevated illustrates that the scorodite aggregates can be progressively concentrations of anthropogenically-emitted metals (e.g., Pb, destabilized during percolation, through pores, of fluids with Cu, Zn) which could be attributed to sources from both Israel higher pH buffered by the dissolution of the carbonates from and Jordan. Elemental ratios of the dust indicate seasonal and the limestone wallrock. Going towards a pore, scorodite synoptic-control on the sources of the dust which in turn progressively breaks down to amorphous Ca-Fe arsenates. determine the solubility of the dust. The dust loads (the Finally, rosettes of fibrous arseniosiderite and, locally, chemical composition multiplied by the calculated euhedral crystals of pharmacosiderite are lining the pores. depositional flux) points on its potential role in providing Detailed textural, chemical, and structural characteristics nutrients during the summer to the oligotrophic waters of the of these different As-bearing phases and the implications for gulf. their relative stabilities will be presented. Analogies with the mineralogy observed in tailings from the old mine operation will also be discussed. A944 Goldschmidt Conference Abstracts 2008
Multiple sediment contributions in The timings of sea level change the southern Lesser Antilles arc during the last glacial cycle, from
M.F. THIRLWALL U/Th dating of submerged corals: Earth Sciences, Royal Holloway Univ. London, Egham TW20 Results from IODP expedition 310 0EX, UK ([email protected]) “Tahiti sea level”
1 1 Lavas from the southern Lesser Antilles have long been ALEXANDER L. THOMAS *, GIDEON M. HENDERSON , 2 3 recognized to have a large sediment isotopic and chemical PIERRE DESCHAMPS , YUSUKE YOKOYAMA , 2,4 2 signature, in part incorporated within the arc crust, based on EDOUARD BARD , BRUNO HAMELIN , 2 2 AFC relationships and elevated δ18O [1]. New Hf and double NICOLAS DURAND AND GILBERT CAMOIN spike Pb isotope data show that the most isotopically depleted 1Department of Earth Science, Parks Road, Oxford, OX1 3PR, lavas in St Vincent and Grenada have Hf-Nd isotopic 87 86 United Kingdom (*correspondence: [email protected]) signatures similar to Atlantic E-MORB but elevated Sr/ Sr, 2 207 204 208 204 Europôle Méditerranéen de l’Arbois, CEREGE, UMR CNRS Pb/ Pb and Pb/ Pb. These are also the most magnesian 6635, BP 80, F-13545 Aix-en-Provence Cedex 4, France in their respective sample groupings, have mantle-like δ18Ocpx 3Department of Earth and Planetary Sciences, Graduate and thus probably have not undergone major interaction with 208 School of Science, University of Tokyo, Tokyo 113-0033, the arc crust. Crustal contamination reduces ∆ Pb, Hf and Nd Japan isotope ratios. In Grenada, this isotopic signature is present in 4Chaire d’évolution du climat et de l’océan, Collège de C-series lavas having Nd/Hf and Nd/Zr 2-3x MORB ratios and France, Europôle Méditerranéen de l’Arbois, F-13545 Ce/Pb>25. Coupled with MORB-like Zr contents, the low Aix-en-Provence Cedex 4 Nd/Zr would usually be taken to imply preferential LREE addition to the magma sources, while the high Ce/Pb ratios U-Th dating of Pre-Last Glacial Maximum (LGM) corals, ought to imply no sediment contribution to the magma source. drilled during IODP Expedition 310 “Tahiti sea level”, has In contrast, isotopically similar samples in St Vincent have provided new data about the timing and magnitude of sea level normal mantle Nd/Zr and low Ce/Pb (~9). The elevated 207 204 208 204 prior to the last deglaciation. Drilling during Expedition 310 Pb/ Pb and Pb/ Pb cannot realistically be derived from recovered 632 m of core (at 57.5% conventional recovery) anywhere other than subducted sediment. In Grenada C-series from 37 drill holes. Of these 37 holes 28 penetrated material sources, the absence of accompanying low Ce/Pb would beneath the postglacial reef sequence. In contrast to previous suggest that the sediment had been depleted in Pb prior to onshore drilling [1], the pre-LGM material recovered during contributing to these magma sources, perhaps through shallow 310 has provided fossil corals that have not suffered volatile release. Strongly elevated Nd/Zr and E-MORB-like significant alteration. Much of the Pre-LGM material Hf-Nd isotope ratios imply that LREE are transported into the recovered is aragonitic (40% of pre-LGM corals screened by source by a fluid largely derived from the subducting basaltic 234 XRD have <1% calcite), and gives δ Ui close to modern crust. A residual HFSE-bearing phase is rendered unlikely by 234 seawater (85% of pre-LGM corals, <150 ka, have δ Ui normal mantle Nb/Zr and Ti/Zr. between 138 and 150). Primitive M-series lavas from Grenada have been divided The slow subsidence of Tahiti, and the depths of the holes into low- and high-La/Yb groups with respectively lower and drilled during Expedition 310 has led to the recovery of Pre- higher source sediment contributions. Both have high Nd/Zr LGM material that is representative of sea level lowstands. and Nd/Hf ratios, ~1.5x and ~2x primitive mantle for the low- Thus, results from Tahiti provide a useful complement to and high-La/Yb groups respectively, and the latter are offset to existing records of sea level from corals which are typically higher 176Hf/177Hf for a given 143Nd/144Nd. In contrast, St 143 144 176 177 biased towards highstands. Vincent lavas have higher Nd/ Nd, lower Hf/ Hf and Pristine pre-LGM samples provide constraints on three normal mantle Nd/Zr. This suggests that sediment addition to periods – MIS3; MIS6; and the start of the penultimate the source is accomplished via a high LREE/Zr component, deglacial. MIS 3 samples support evidence for rapid change in either fluid or a melt in equilibrium with residual sediment sealevel during this period. Corals recovered from marine zircon. isotope stage 6 constrain the magnitude of the deglacial sea level rise at the penultimate deglacial. The timing of start of [1] Thirlwall et al. (1996) GCA 60, 4785-4810. this deglacial is constrained by a series of corals that suggest a reef drowning event ~90m below sea level.
[1] Bard et al. (1996) Nature 282, 241-244. Goldschmidt Conference Abstracts 2008 A945
Sulfide-bearing diamonds: Is there a common drive for the The exception, not the rule negative excursion of organic Carbon 1,2 2 3 E. THOMASSOT , P. CARTIGNY AND J.W. HARRIS and the attenuated mass- 1McGill University, Montréal, Canada independent-Sulfur at 2.7 Ga? ([email protected]) 1,2 1 3 2 CHRISTOPHE. THOMAZO *, M. ADER , J. FARQUHAR Institut de Physique du Globe de Paris, France 2 AND P. PHILIPPOT ([email protected]) 3University of Glasgow, UK ([email protected]) 1Laboratoire de géochimie des isotopes stables, Institut de Physique du Globe de Paris, place Jussieu, 75251 Paris, The paradox between the low sulfide content of mantle Cedex 05, France xenoliths (about 300 ppmS) and the overabundance of sulfide (*correspondence: [email protected]) minerals entrapped in diamonds (70% of inclusions) points to 2Laboratoire Géobiosphère actuelle et primitive, Institut de a possible genetic link between these two minerals. Physique du Globe de Paris, France Traditionally, sulfide-bearing diamonds are thought to have an 3Department of Geology, University of Maryland, College equivalent origin to other gem diamonds. Geochemical Park, Maryland, USA measurements from sulfide-bearing diamonds including dating using the Re-Os chronometer have been used to constrain the In order to bring further insights into the prevailing history of whole suites of diamonds (assuming that all gem environmental conditions during the δ13C negative Fortescue diamonds would be comparable). Excursion attributed to an increase in methanotrophic In order to test this assumption, we have undertaken a biomass, we carried out a detailed carbon (12C, 13C) and detailed geochemical study of 113 sulfide-bearing diamonds multiple sulfur (32S, 33S, 34S, 36S) isotopic study through the recovered from 3 different diamondiferous pipes from the entire pristine core drilled from the slightly metamorphosed Kaapvaal craton, Jwaneng (Botswana), Kimberley Pool and 2.7 Ga Tumbiana Formation. 13 Koffiefontein (South Africa). We measured the N-content and Organic δ CPDB values vary markedly at meter scale and aggregation state of 134 diamond chips, by IR spectroscopy. display a bimodal distribution with two maxima at -43 and Each fragment has then been characterized with respect to -34‰. This isotopic record, together with petrological and their C- and N-isotopic compositions. other geochimical proxies, cannot be explained by secondary Sulfide bearing diamonds are N-richer (800 at.ppm in processes such as diagenesis or metamorphism but likely average) than other silicate-bearing diamonds from the same reflects variable contributions of 13C-depleted methanotrophic mine, yet the nitrogen aggregation state, which reflects the biomass to the organic matter. Sedimentary pyrites display efficiency of diffusion through the crystal, is limited to a Mass-Independent-Fractionation of sulfur isotopes (MIF-S) 33 maximum of only 12% of Type IaB). The diamonds also with ∆ SCDT anomalies ranging between -0.24 and 1.64‰ display a narrow range of δ13C (from -8.4 to -3.1 ‰, st. (average 0.46‰) and show a linear relationship between 33 36 36 33 dev. 1.5‰, excluding a single extreme value at -18.7 ‰). ∆ Spy and ∆ Spy with a ∆ S/∆ S ratio ~ -1.5, similar to that Associated δ15N values range from -13.6 to 8.3 ‰, have a of most Mesoarchean rocks and probably related to changes in normal distribution and a median value of -5‰. atmospheric composition (e.g. CH4/CO2 ratio). Recognition of The C- and N-isotopic compositions of sulfide-bearing positive correlation between the 12C-enrichment of organic diamonds are typical for a mantle reservoir and, a priori, their matter and MIF-S suggests a genetic link between the δ13C carbon source does not differ from those of other diamonds. negative excursion and the observed increasing MIF-S The narrow range of δ13C values, however, is surprising and fractionation of Late Archean rocks. unexpected being characteristic of a rapid crystallization We propose that different types of metabolisms operating history, which is consistent with the high N-contents. More under various redox conditions were present in the Tumbiana tellingly the low aggregation state is only compatible with a paleo-environment and we suggest that the δ13C negative low temperature crystallization (T < 1000 °C). Fortescue Excursion would reflect biotic methane assimilation We conclude that sulfide-bearing diamonds represent a which leds to a conjoint decrease in atmospheric methane distinct diamond population that formed rapidly in a relatively concentration and transient increase in MIF-S fractionation low temperature environment. Consequently, conclusions before the Great Oxidation Event. based on these specific diamonds (e.g. Re/Os ages) may not apply to other diamonds, even from the same mines. A946 Goldschmidt Conference Abstracts 2008
Evolution of soil Iron mineral Dykes and slabs in the mantle: composition as a function of Model sources for the adakite clan 1 2 climate-driven Fe loss D.J. THORKELSON , K. BREITSPRECHER AND 3 1 2 R.B. ICKERT AARON THOMPSON *, DENIS G. RANCOURT , 3 4 OLIVER CHADWICK AND JON CHOROVER 1Dept. of Earth Sciences, Simon Fraser University, Burnaby, B.C., V5A 1S6, Canada ([email protected]) 1Department of Crop and Soil Science, University of Georgia, 2Dept. of Earth and Ocean Sciences, University of British Athens, GA (*correspondence: [email protected]) Columbia, Vancouver, B.C., V6T 2B4, Canada 2Department of Physics, University of Ottawa, Ottawa, ON ([email protected]) 3Geography Department, University of California, Santa 3Research School of Earth Sciences, Australian National Barbara, CA University, Canberra ACT 0200 Australia 4Department of Soil, Water and Environmental Science, ([email protected]) University of Arizona, Tucson, AZ
Melting of mafic rock in the mantle environment to We measured soil iron mineral composition as a function produce melts of intermediate composition are explored with of pedogenic Fe loss in surface (10 – 20 cm) and subsurface two hypotheses: (1) melting of young subducted oceanic crust, (50 – 70 cm) basaltic soil horizons from the Island of Maui and (2) melting of arc-generated dykes in the lithospheric along a climate gradient (MCG) ranging from 2.2 – 4.2 m mantle. The melting of subducted crust is evaluated by mean annual precipitation (MAP). All soil forming factors examining conditions of dehydration and partial melting of except climate were conserved. Solid phase Fe mineralogical mafic rock, and transferring key reaction curves onto gridded composition was assessed using room temperature (RT, 22°C) maps of the down-going slab. Petrologic zones on the slab and liquid helium temperature (LHeT, 4.2 K) 57Fe Mössbauer range from broad regions of prograde metamorphism to more spectroscopy (MBS). Analysis of the MBS spectra resolved restricted areas involving partial melting and restite formation. four main mineral components: hematite, ferric-organic Melting will be concentrated in areas of extremely young crust complexes, ferrous iron, and a goethite component that could adjacent to slab windows, where the slab is thinnest and be further sub-divided into three approximate size components hottest. Nearest the slab window and closest to the trench, (< 3 nm, 3 -12 nm, and > 12 nm). Increasing MAP from 2.8 to melts will have the composition of non-adakitic dacite, and the 4.2 m resulted in a decrease of 57Fe Mössbauer-assigned soil restite will be garnet-free. Farther from the slab window, and goethite fraction coincident with an increase in ferrous and at greater depths, melting of the subducted crust will produce organically bound-Fe components, while the hematite fraction adakitic magma, leaving a garnetiferous restite. Reaction of showed little climatic effect. The MCG has a documented slab-derived melts with overlying mantle of the asthenosphere decrease in both mean annual Eh values and Fe with or lithosphere will modify the magma, resulting in liquid increasing rainfall, thus yielding an upland soil gradient where compositions with more magnesia and less silica. Although progressive Fe removal is very likely dominated by reductive this model is feasible, the second hypothesis, involving dissolution. Despite this, ferric oxides persist even at 4.2 m melting of dykes in the lithospheric mantle, provides an MAP, suggesting re-oxidation events are a common feature of attractive alternative. This hypothesis requires a previous these ecosystems. Interestingly, the total goethite fraction event of magmatism and emplacement of mafic dykes into the exhibits a strong inverse-correlation (R2=0.88) with Fe isotope mantle lithosphere. Where such lithosphere is reheated, the values (δ56Fe, measured previously [1]) for both surface and dykes undergo partial fusion and leave behind garntiferous sub-surface horizons. This suggests the mechanisms governing restite. The resulting felsic melts react with the ambient Fe loss and Fe retention are linked to a greater degree than lithospheric peridotite to produce more magnesian magmas. often appreciated. Dykes of subduction-generated basalt, with enrichments in
hydrous magmatophile elements relative to those in typical [1] Thompson et al. (2007) Chem. Geol. 238(1-2), 72-83. ocean floor basalt, may be preferable sources for the generation of the adakite and magnesian andesite. Heating of the lithosphere could involve upwelling asthenosphere in a range of tectonic environments including plumes, slab windows and extending crust. Goldschmidt Conference Abstracts 2008 A947
Ages of carbonatite and syenite from Ca isotope ratios in the largest rivers the Mianning-Dechang REE belt in in the world: Implications for the the eastern Indo-Asian collision zone, global Ca budget and weathering SW China and their geological processes 1,2 2 significance EDWARD T. TIPPER , JÉRÔME GAILLARDET , 3 2 1,2 3 1,2 ALBERT GALY AND PASCALE LOUVAT SHIHONG TIAN , ZENGQIAN HOU , TIPING DING , 1 3 1 ZHUSEN YANG , ZHIMING YANG , ZHONGXIN YUAN , 1IGMR, ETH Zurich, Clausiusstrasse 25, NW 8092 Zürich, 4 1 4 YULING XIE , YINGCHAO LIU AND ZHENG LI Switzerland ([email protected]) 2IPGP-Université Paris 7, Paris, France 1Institute of Mineral Resources, CAGS, Beijing 100037, 3Dept of Earth Sciences, University of Cambridge, UK P.R. China ([email protected])
2Key Laboratory on Isotope Geology, Ministry of Land and The oceanic Ca budget is balanced between the inputs of Resources, Beijing 100037, P.R. China Ca (mainly riverine) and the outputs of Ca (biogenic 3Institute of Geology, CAGS, Beijing 100037, P.R. China carbonate). Initial measurements of Ca isotope ratios in 4Civil & Environmental Engineering School, Beijing several large rivers and marine carbonates (e.g. [1]) led these University of Science and Technology, Beijing 100083 workers to conclude that the modern oceanic Ca isotope
budget was in steady state. However, marine records of Ca Himalayan magmatic activity in southwestern China forms a semi-continuous potassic igneous province in the isotope ratios show small but significant variations, implying eastern Indo-Asian collision zone, a high topographic relief that the oceanic Ca budget must deviate from steady state over area bounded by a series of Cenozoic strike-slip faults. The long time-scales, due to effects related either to the inputs or western Sichuan carbonatites (WSC) are associated with outputs of Ca from the oceans. Recent measurements of Ca contemporaneous syenites, and form a 270-km long belt of isotope ratios in Himalayan rivers and soil profiles (e.g. [3, 4]) Cenozoic carbonatite-alkalic complexes in the EIACZ. Unlike have revealed that Ca isotope ratios are fractionated during the most known carbonatite plutons within plates, generated by weathering process. In particular solute Ca from small rivers anorogenic processes (e.g. rifting), the WSC occur in a draining limestone were shown to have a different 44Ca/42Ca continental collision zone, formed by the Indo-Asian ratio (expressed as δ44/42Ca) than the Ca in the limestone they continental collision since the Paleocene period. were draining. Given that at a global scale, 67% of riverine Ca From north section to south section (see Fig. 1), the is derived from carbonate weathering, this small offset could analytical results are as follows: at Maoniuping, K-Ar dating have significant implications for the δ44/42Ca of large rivers on the bulk-rock and igneous minerals yields an age of and the oceanic Ca balance. 31.7±0.7 Ma for carbonatite, and an age of 40.8±0.7 Ma for To resolve whether this discrepancy in Ca isotope ratios syenites. At Muluozhai, the K-feldspar separates from the 40 39 between limestone and river water was significant at a global syenite yielded a Ar/ Ar plateau age of 31.2 ± 0.56 Ma. At 44/42 Lizhuang, the K-feldspar separates from the syenite yielded a scale, we have measured δ Ca in 22 of the largest rivers in 40Ar/39Ar plateau age of 27.1 Ma. At Dalucao, SHRIMP the world. These include samples from different water stages, dating on the zircons of the carbonatite and syenite yields an and a time-series for the Salween and Irrawaddy Rivers. 44/42 age of 12.99 ± 0.94 Ma and 14.53 ± 0.31 Ma, respectively. δ Ca in the largest rivers in the world is remarkably 44/42 homogeneous, with a flux weighted mean δ Ca of 0.39‰ relative to SRM915a. The implications of the homogeneity of the data, given the apparent fractionations observed in weathering systems at small spatial scales will be discussed. The implications for the global Ca cycle will also be considered.
[1] Schmitt et al. (2003) EPSL 213, 503–518. [2] Ewing et al. (2008) GCA 72, 1096-1110. [3] Tipper et al. (2008) GCA 72, 1057-1075.
In summary, formation ages decrease systematically from north to south, and their age sequence can be plausibly explained by assuming that a region of melting in the south plate moved north along the Yalongjiang fault relative to the left plate.
This work was supported by grants (Contract No. 40603012, 40425014, 2002CG412610, 13-7-5, 40573035 and KL05-9). A948 Goldschmidt Conference Abstracts 2008
Bridging the ‘gap’ between U(VI) uptake by laboratory dissolution and calcium silicate hydrates 1 1 2 2 natural chemical weathering J. TITS *, N. MACE , G. GEIPEL , M. EILZER 1 AND E. WIELAND D. TISSERAND AND R. HELLMANN 1Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland 1Environmental Geochemistry Group. LGIT/CNRS UMR (*correspondence: [email protected]) C5559, BP 53X, 38041 Grenoble Cedex 9, France 2Forschungszentrum Dresden-Rossendorf, D-01314 Dresden, ([email protected], Germany [email protected])
The uptake of U(VI) by calcium silicate hydrate (C-S-H) Mineral surfaces play a primordial role in controlling the phases has been investigated using batch sorption experiments transfer of matter and energy between minerals and the and time-resolved laser fluorescence spectroscopy (TRLFS). surrounding environment. In order to understand the C-S-H phases are secondary minerals formed by the mechanisms of chemical weathering reactions, both in the interaction of hyperalkaline groundwater escaping from a laboratory and in the field, we are carrying out nanoscale cementitious nuclear waste repository, with Si-containing host investigations of altered layers that develop on silicate mineral rocks. surfaces. Specifically, we are investigating the chemical and The U(VI) uptake by C-S-H phases with varying physical evolution of fluid-mineral interfaces at the molecular composition was investigated in a series of batch sorption level using various analytical techniques, in particular high experiments in the pH range of 10.0 to 13.3. The distribution resolution and energy filtered TEM. A series of silicate of 233U(VI) between solid and liquid phase was determined by minerals (orthoclase, albite, labradorite, anorthite, radiochemical analysis. The U(VI) uptake was shown to be wollastonite, diopside, pyrope garnet, olivine) have been very strong as illustrated by distribution ratios (R values) altered in the laboratory at acid pH conditions. In addition, one d ranging between 103 L kg-1 and 105 L kg-1. Sorption isotherms sample of naturally weathered K-feldspar was investigated. In measured on C-S-H phases with different C:S ratios at all cases, the mineral surfaces developed a near-surface altered different pH’s all exhibit a non-linear behavior suggesting the layer that is chemically and structurally distinct from the presence of multiple U(VI) sorbed species. Increasing the pH unaltered mineral. The structural and chemical interfaces from 10.5 to 13.3 by the addition of NaOH or KOH, results in between the altered layers and the corresponding minerals are a significant decrease of the U(VI) sorption. always spatially coincident and extremely sharp. The chemical TRLFS data showed the presence of several different depth profiles, which are measured directly in cross section on U(VI) solid species. Resolution of overlapping luminescence FIB-prepared electron transparent ultrathinsections, are very spectra was accomplished by using an iterative target factor sharp (chemical gradients on the order of 5-10 nm) and analysis approach. Luminescence spectra of the U(VI) sorbed therefore were most likely not created by a diffusional species at low U(VI) loadings were characterized by process. This finding suggests that altered surface layers luminescence emission maxima between 500 nm and 520 nm represent the precipitation of a new secondary phase. This and four to five vibronic components typical for luminescence hypothesis stands at odds with the commonly accepted emission of the linear [O=U=O]2+ structure of the uranyl ‘leached layer’ theory based on surface altered layers created group. At higher loadings an increasing contribution of species by preferential leaching and interdiffusion. Most importantly, with an emission maximum at 540 nm appeared in the our preliminary results suggest that the intrinsic dissolution luminescence spectra suggesting the presence of uranate-type process is the same for laboratory and natural weathering species. The vibronic spacings of the emission spectra were processes. found to vary between 660 cm-1 and 790 cm-1. From this information it was possible to estimate values of the U-O bond length of the axial oxygens of the sorbed uranyl species. Comparison of the luminescence spectra of the U(VI) sorbed species with spectra obtained from well-known U(VI) reference compounds provided further information on the coordination environment of the sorbed U(VI) species. Goldschmidt Conference Abstracts 2008 A949
Kinetics and mechanisms of Non-relationship between slab silica nanoparticle formation melting and high-Mg andesite from
D.J. TOBLER*, L.G. BENNING AND S. SHAW northwestern Kyushu, SW Japan Earth and Biosphere Institute, University of Leeds, Leeds, S. TOKESHI, K. KOBAYASHI AND E. NAKAMURA LS29JT, UK (*correspondence: [email protected]) The Pheasant Memorial Laboratory for Geochemistry and
Cosmochemistry, Institute for Study of the Earth’s Silica polymerisation and the subsequent formation of Interior, Okayama University at Misasa, Tottori, Japan silica nanoparticles occur in many modern terrestrial ([email protected]) environments (e.g. brines, hot springs, deep reservoirs). They also played an important role in ancient geological settings Major and trace elements, and Sr-Nd-Hf-Pb isotopic and are believed to have been crucial to the formation of compositions of mafic volcanic rocks from the northwestern silica-rich deposits that were recently observed on Mars. In the Kyushu, SW Japan, provide insight into the nature of mantle literature, most studies aiming at elucidating the reaction wedge and reflect the magmatic evolution linked with active mechanisms and rates of silica polymerisation are based on the continental margin. The simultaneous occurrence of time-dependent depletion of monosilicic acid in the chemically diverse magma composition, from alkali basalt polymerizing solution. However, little to no quantitative or through tholeiitic basalt to high-Mg andesite, characterizes the time-resolved data on the size of the growing nanoparticles northwestern Kyushu magmatism, ranging age from ca. 10 to within the solution is available. 5 Ma. Majority of volcanic rocks consists of the tholeiitic Here we present results from an in situ time-resolved basalts, in contrast, the alkali basalts and the high-Mg study that provided quantitative information on the initial andesites are minor. The alkali basalts have trace element steps of silica polymerisation and silica nanoparticle formation pattern similar to oceanic island basalt (OIB). The OIB-like from both inorganic and organic solutions. The experiments pattern shifts progressively to typical island-arc lava pattern, were carried out in near neutral pH (7 – 8) solutions with silica marketable depletions of HFSE, with increasing degree of concentrations ranging form 640 – 1600 ppm SiO and ionic 2 silica-saturations from the alkali basalt to the high-Mg strengths (IS) of 0.02 – 0.22 M. These ranges were chosen as andesite. Recently, a seismic tomographic study suggested they represent those most often found in natural geothermal young Shikoku basin lithosphere has been present around 300 systems. Furthermore, the presence of specific organics km depth beneath the northern Kyushu [1]. However, (50 - 300 ppm of either glucose, glutamic acid or xanthan advocated process of interaction between mantle wedge and gum, representing microbial cell wall functional groups) on partial melts derived from subducting sediment and altered the nucleation and growth process was also examined. oceanic crust [e.g. 2, 3], cannot explain the observed The formation of silica nanoparticles (i.e. change in particle geochemical variations. The magmatism seems to be closely size over time) was followed using synchrotron-based Small liked with active back-arc basin, Okinawa Trough, because the Angle X-ray Scattering (SAXS) and conventional Dynamic northwestern Kyushu has been located at an extension of Light Scattering (DLS) combined with conventional or cryo- northern edge of the Okinawa Trough and its early rifting high-resolution scanning and transmission electron stage [4] (9-6 Ma) coincided approximately with the initiation microscopy (SEM/-HR-cryo-TEM). The polymerization of the voluminous magmatism in the northwestern Kyushu. reactions were induced either by neutralizing a high pH The extensional tectonic environment might have led to solution (from pH 12 to 7) or by rapid cooling of a intense thinning and detachment of continental lithosphere by supersaturated hot silica solution (from 230ºC to below asthenospheric upwelling. The additional upwelling would 100ºC). The data was used to derive a kinetic model which trigger greater degree of partial melting to form the tholeiitic shows a 3 stage growth process for silica nanoparticles: (1) melts and subsequent varying degree of interactions with nucleation of critical nuclei (2 nm in size, regardless of [SiO ] 2 metasomatized lithospheric mantle having notably depleted in or IS), (2) particle growth (surface-controlled, following 1st Sr-Nd-Hf isotopic compositions, which would result in order reaction kinetics) and (3) particle coarsening and producing the simultaneous occurrence of chemical diversity. aggregation via Ostwald ripening. Variations related to the different experimental variables (i.e. [SiO ], IS or organics) on 2 [1] Abdelwahed & Zhao (2007) Phys. Earth Planet. Inter. the kinetic pathways and mechanisms of polymerization will 162, 32-52. [2] Tatsumi & Hanyu (2003) Geochem. Geophys. be discussed. Geosyst. 4(9) doi, 10. 1029/2003GC000530. [3] Tatsumi (2006) Annu. Rev. Earth Planet. Sci. 34, 467-499. [4] Letouzey & Kimura (1985) Mar. Pet. Geol. 2, 111-130. A950 Goldschmidt Conference Abstracts 2008
The role of Group V and VI Elements Metasomatic processes recorded in in metamorphic polymetallic melts: fibrous diamonds 1 1 2 Parallels with magmatic sulfide E.L. TOMLINSON *, W. MÜLLER , R.W. HINTON , 3 3 O. KLEIN-BENDAVID , D.G. PEARSON systems 4 AND J.W. HARRIS A.G. TOMKINS 1Department of Earth Sciences, Royal Holloway University of School of Geosciences, Monash University, Melbourne, VIC London, Egham, Surrey, UK 3800, Australia (*correspondence: [email protected]) 2School of Geosciences, University of Edinburgh, West Mains Research into polymetallic melt formation during high Road, Edinburgh, UK temperature metamorphism of ore deposits has revealed that 3Department of Earth Sciences, Durham University, South four different melt types can develop: (1) sulfide melts Road, Durham, UK dominated by Pb, Fe, Cu, Zn and S; (2) sulfosalt melts 4Division of Earth sciences, University of Glasgow, Lilybank involving Au, Ag, Pb, Tl, Hg, Cu and Fe complexed with Gardens, Glasgow, UK Sb-S, As-S and/or Bi-S; (3) intermetallic melts developed between alloys of Au, Ag, Hg, As, Sb and Bi; and (4) telluride Fibrous diamonds containing both fluid and single-phase melts involving Au, Ag and Pb complexed with Te. The silicate inclusions provide a unique insight into metasomatic sulfide melts are comparatively unimportant for mobilizing processes operating during diamond growth. Fluid-rich gold, as they crystallize at high temperatures and appear to be diamonds from the Panda kimberlite (Northwest Territories, incapable of dissolving >100 ppm Au. In contrast, As-, Sb- Canada) contain peridotite-suite silicate inclusions and and/or Bi-bearing sulfosalt or intermetallic melts, can contain H2O-carbonate fluid inclusions. The fluid is highly enriched in >50% gold, and persist to T < 300ºC. In some deposits, trace elements and has a steep negative REE pattern. The Sr Au-rich telluride melt is associated with accumulations of isotope composition of fluids from different diamonds is sulfosalt melt, and some compositions are molten below highly variable (0.7049 to 0.7084). This range of values 400ºC. A concept-testing experiment, run at 850ºC and 5 kbar extends to more radiogenic compositions than typical and involving a Au, As and Bi-rich starting composition, convecting mantle and indicates a role for a fluid from a long- produced coexisting Fe-Cu sulfide and Au-As-Bi-bearing term enriched source, whereas fibrous diamonds are usually sulfosalt melts. This result indicates that sulfide-sulfosalt through to originate from the MORB-source mantle. immiscibility can develop during sulfide melt fractionation Peridotitic clinopyroxene and garnet inclusions have high provided that high enough concentrations of the V-VI Cr contents (>7 wt% and >1.8 wt% Cr2O3 respectively) and elements are reached, and also that Au partitions strongly into olivine has high Ni (3550 ppm), indicating that the silicates the sulfosalt melt. These observations can be applied to have undergone depletion by melt extraction; the high Cr and understanding controls on PGE distribution in magmatic Ni contents are not consistent with precipitation directly from sulfide systems since Au, Pt and Pd behave similarly in this the carbonate fluid. Therefore the silicate inclusions pre- setting. Because V-VI elements have low melting points, they existed the influx of H2O-carbonate. However, the silicate will become concentrated in sulfide magma by crystallisation inclusions have enriched trace element signatures (similar to of MSS and ISS, although they will remain dissolved until those seen in inclusions in octahedral diamonds), recording saturation is reached. The correlation between the V-VI metasomatism by the co-existing fluid. Texturally, the silicate elements and PGE in magmatic sulfide deposits suggests that inclusions are extremely small (<5 to 15 µm) and highly PGE may remain bound to these elements, in particular As, Bi, abundant. The diamond samples are also zoned with respect to Sb and Te, within the sulfide melt, thereby allowing the PGE silicate inclusions e.g. garnet present towards the core, and to also become concentrated during crystal fractionation. clinopyroxene towards the rim. This suggests that a process of Since most V-VI element-bearing minerals found in these fractional re-crystallisation may have been operating during deposits, including many PGMs, have melting points below metasomatism. the crystallisation temperatures of MSS and ISS, it may be inevitable that PGE-rich sulfosalt melts will eventually exsolve. If a connected melt network remains, density differences may drive gravitational segregation of sulfosalt melt, allowing formation of PGE-enriched zones. Goldschmidt Conference Abstracts 2008 A951
Geochemistry and Sr-Nd isotopic Sea-floor weathering of hydrothermal systematics of Archaean and chimney sulfides at the East Pacific Neoproterozoic charnockites from the Rise 9°N: Chemical speciation and Southern Granulite Terrain, South isotopic signature of Iron using X-ray India: Magma genesis and tectonics absorption spectroscopy and laser- 1 1 J.K. TOMSON , Y.J. BHASKAR RAO *, ablation MC-ICP-MS 1 2 T. VIJAYA KUMAR AND A.K.CHOUDHARY 1 2 BRANDY M. TONER , OLIVER ROUXEL , 3 4 1National Geophysical Research Institute, Hyderabad, India CARA M. SANTELLI AND KATRINA J. EDWARDS (*correspondence: [email protected]) 1Department of Soil, Water, and Climate, University of 2Institute Instrumentation Centre, IIT-Roorkee, India Minnesota – Twin Cities, St. Paul, MN 55108
([email protected]) The Southern Granulite Terrain (SGT), South India 2Department of Marine Chemistry and Geochemistry, Woods presents a mosaic of Archaean and Neoproterozoic regional Hole Oceanographic Institution, Woods Hole, MA, 02543 granulite terrains with peak-metamorphism dated at ~2.5 Ga ([email protected]) and ~0.55 Ga respectively. The temporally distinct terrains lie 3Department of Engineering, Harvard University, Cambridge, across a crustal-scale shear zone system, well known as the MA, 02138 ([email protected]) Palghat-Cauvery Shear Zone. In recent Gondwana 4Department of Biological Sciences, University of Southern supercontinent models, the Neoproterozoic granulite terrains California, Los Angeles, CA 90089 ([email protected]) of the SGT are part of an extensive zone of reworked ancient crust within the Pan-African (0.75-0.55 Ga) East African A new laser-ablation MC-ICP-MS analytical method was Orogen. Charnockitic ortho-gneisses are widespread in both used with spatially-resolved elemental and mineralogical data the Archaean and Neoproterozoic terrains and provide a rare (synchrotron-radiation XRF, XRD, and XAS) to provide opportunity to evaluate magma genesis in contrasting tectonic constraints on: (1) the complex interactions between regimes. hydrothermal fluids, seawater, and sulfide minerals over a Based on a new data set of major-trace element wide range of temperature and redox conditions, and (2) compositions and Sr-Nd isotopic systematics of 130 potential biosignatures of Fe-oxidizing and Fe-S-reducing charnockite samples, we infer contrasting source compositions bacteria in chimney environments at the East Pacific Rise 9°N. and genetic environments for the protoliths of the Archaean Iron mineralogy, chemical speciation, and isotopic ratios were and Proterozoic charnockites. The former show near- determined for several inactive chimneys and massive sulfides chondritic εNd and initial-87Sr/86Sr at ca. 2.5 Ga. Their rare 0 with contrasted extents of seafloor weathering. We collected earth element and other incompatible trace element two-dimensional elemental maps – Fe, K, S, and Si – at the distributions are suggestive of derivation of the Archaean micron scale within chimney cross-sections. With the XRF magmas by hydrous partial melting of amphibolitic crust with maps as a guide, we examined the mineral structure (XAS and residual garnet and hornblende. Their source could be either XRD) and Fe isotopic signature (laser ablation MC-ICP-MS) dominated by a mantle component produced by subduction of Fe oxide and sulfide minerals. Fe oxide minerals were process during the latest Archaean, with variable extent of essentially present: (1) as coatings on sulfide minerals, and incorporation of mid-Archaean (upto 3.5 Ga) crustal (2) in close association with Si-rich materials. XAS results components or may have involved an Archaean granulitic reveal the presence of a suite of Fe oxide minerals lower crust typically with low-initial 87Sr/86Sr. On the representing a continuum of crystallinity from less ordered contrary, the sources of Proterozoic charnockites involved than ferrihydrite to well crystallized goethite. We interpret the greater recycling of older (upto 3.2 Ga) crustal components. Fe-isotope signatures of goethite and ferrihydrite as reflecting Modeled at ca. 1.8 Ga, 0.8 Ga and 0.55 Ga, the genesis of the different Fe oxidizing environments related to: (1) direct Proterozoic charnockites is consistent with significant oxidation from Fe from pyrite in massive sulfide under intracrustal melting processes within a thickened crust. In a oxygenated seawater conditions, yielding δ57Fe values similar restricted segment of the Neoproterozoic domain there is also to those of pyrite and (2) Fe oxidation from late stage Fe-Si- evidence for charnockites derived from juvenile protoliths rich hydrothermal fluids in chimney environments, yielding with affinities to syn-collisional or arc magmas. A review of variable δ57Fe values, both lower and higher than δ57Fe values correlation between the South Indian and Sri Lankan high- of associated pyrite. grade terrains is also considered. A952 Goldschmidt Conference Abstracts 2008
Kinetics of pyrite oxidation and An experimental approach to clay denitrification mineral formation on Mars 1 2 3 C. TORRENTÓ AND J. CAMA N.J. TOSCA *, R.E. MILLIKEN AND M.B. WYATT Institute of Earth Sciences ‘‘Jaume Almera’’, CSIC. 1Dept. of Organismic & Evolutionary Biology, Harvard Barcelona, Spain ([email protected]) University, 26 Oxford St., Cambridge, MA 02138 (*correspondence: [email protected]) Torrentó et al. (2007) showed that nitrate attenuation, 2Jet Propulsion Laboratory, Pasadena, CA 91001 denitrification, mediated by pyrite oxidation is enhanced by 3Dept. of Geological Sciences, Brown University, Providence, bacterial activity. However, this process (or part of it) may be RI 02912 controlled abiologically. The overall reactions describing the process of denitrification-pyrite-oxidation are In this study, a laboratory-based approach is taken to - + 2- 2+ delineate the chemical boundaries of clay formation on Mars. 14 NO3 + 5 FeS2 + 4 H → 7 N2 + 10 SO4 + 5 Fe + 2H2O Ageing/co-precipitation experiments are conducted with - 2+ + 3+ NO3 + 5 Fe + 6 H → ½ N2 + 5 Fe + 3 H2O synthetic basaltic weathering solutions at oxic and anoxic conditions and at varying pH (3-9). where denitrification occurs via oxidation of pyrite and Fe(II) Under oxic conditions, there is a sharp pH boundary and pyrite oxidation is enhanced by the presence of Fe(III). between Fe-sulfate/oxide precipitation and clay mineral The present contribution aims at studying the kinetics of (saponite/nontronite) formation which is controlled by the pyrite oxidation and nitrate reduction under anoxic conditions. solubility of a Fe2+-bearing “clay precursor” phase. Under The process is investigated at different pH and nitrate content anoxic conditions, this pH boundary is removed and a by means of long-term flow-through experiments at O partial 2 spectrum of X-ray amorphous Fe-bearing silicate phases is pressure of 0.003 atm, pH range of 4.5 to 7.5, and NO - 3 formed from pH 4-9. The co-precipitation of Fe2+ with other concentration from 0.1 to 1.7 mmol L-1. cations in the anoxic system is initiated by Al hydrolysis, with Results show that as pyrite oxidizes nitrate reduces. At pH controlling the crystallization kinetics of low NO - concentration (0.1 or 0.4 mmol L-1) nitrate reduction 3 saponite/nontronite clay minerals from X-ray amorphous Fe2+- is more effective, lasting longer than at high nitrate bearing precursor phases. Our results indicate that the concentration (1.3 or 1.7 mmol L-1). In the experiments in formation of Fe2+- or Fe3+-bearing smectites at the Martian which nitrate reduction clearly takes place, two stages can be surface through basaltic weathering may only have occurred distinguished. First, nitrate is reduced to a mixture between under initially reducing conditions. nitrite and nitrogen gas, and secondly, nitrate is reduced only In all experiments, X-ray amorphous phases are initially to nitrite. Thereafter, nitrate reduction halts (Fig. 1). 2+ 3+ produced, either as Fe /SiO2 (clay precursors) or Fe /SiO2- bearing phases. The latter do not transform into clays. These phases represent an important sink for SiO2(aq) in Martian geochemical systems and provide a link between acid-sulfate and clay mineral precipitation regimes. In addition, despite thermodynamic supersaturation, carbonate mineral formation in these experiments appears to be inhibited by the formation of X-ray amorphous SiO2-bearing phases, which control both cation concentrations and solution pH. The visible-near infrared and thermal infrared spectroscopic properties of these materials are being examined in detail and will enable such phases to be identified if they exist at the Martian surface. To infer paleo-environmental conditions needed to produce specific clay assemblages observed on Mars, the experiments described above are compared to new basalt alteration experiments focusing on oxic and anoxic conditions as well as additional factors that control solution neutralization Figure 1: Variation of input and output nitrate concentration time. and output nitrite concentration with time. It is observed that nitrate reduction is pH independent and the nitrate-reduction rate is 10-10.62 (±0.31) mol s-1. The pyrite dissolution rate at the studied conditions equals 10-12.54 (±0.14) mol m-2 s-1.
[1] Torrentó et al. (2007) Goldschmidt Confer. GCA 71, A1032. Goldschmidt Conference Abstracts 2008 A953
H2CO3(s): A new candidate for Hafnium-Tungsten chronometry of CO2 capture and sequestration the eucrite parent body JOHN A. TOSSELL M. TOUBOUL*, T. KLEINE, S. ACIEGO AND B. BOURDON Dept. of Chemistry and Biochemistry, University of Institute of Isotope Geochemistry and Mineral Resources, Maryland, College Park, MD 20742 ([email protected]) ETH Zurich (*correspondence: [email protected])
To reduce the magnitude of anthropogenic global climate There is a debate about the timescales of accretion and change it will be necessary to remove CO2(g) from the differentiation of the eucrite parent body (EPB). Based on Al- effluent streams of power plants (and possibly directly from Mg systematics, some have argued that the EPB accreted the atmosphere as well) and to then sequester it as either a within less than ~1.5 Ma [1], whereas others, based on Sr condensed phase or in solutions and/or compounds produced isotope evidence, stated that accretion must have been later by chemical reaction. A major difficulty in achieving this goal than ~3 Ma [2]. To better constrain the chronology of the 182 182 arises from the very weak acidity of CO2(g), causing it to react EPB, we applied the extinct Hf- W system combined with only incompletely with weak bases, forming complexes which precise Hf, U, and W concentration measurements to a readily decompose at high temperatures. Reaction with strong comprehensive set of eucrites, including both basaltic and, for bases yields more stable complexes but strong bases are more the first time, cumulate lithologies. costly and massive amounts of chemical products would still Our new data reveal that in contrast to an earlier report [3], need to be sequestered. When gas-phase CO2 reacts with the the Hf-W data for eucrites do not define an isochron but, at weak base water, or when bicarbonate reacts with acid, an least in part, reflect contamination of some samples with W unstable product “H2CO3” can initially be formed. Although having a terrestrial isotopic composition. If the samples that the monomeric form of this compound is highly unstable, its are clearly contaminated are excluded from the regression, no oligomers are much more stable due to H-bonding, with free statistically meaningful isochron is obtained for the basaltic 182 energies (per H2CO3 unit) for the larger oligomers eucrites. These have ε W values between ~20 and ~30 and approaching that for the gas-phase combination of CO2 and Hf/W ratio ranging from 20 to 35. The measured Hf/W of the H2O. Although it is still thermodynamically slightly unstable, basaltic eucrites are similar to their source Hf/W, which are a oligomeric or solid form of H2CO3 may well be kinetically calculated based on their measured U/W ratios. This is stable, particularly in the absence of H2O. This indicates that it consistent with the Nd-Hf isotope systematics of eucrites that may be possible to capture gas-phase CO2 directly, using only suggest derivation as large degree melts from a source with cheap and abundant H2O, and to store it in the form of a solid chondritic abundances of refractory lithophile elements [4]. or an oligomer. These conclusions are based on quantum Therefore, the Hf-W systematics of basaltic eucrites might computations which faithfully reproduce the structures and reflect that of their sources, such that core formation ages can - stabilities of H2CO3 oligomers and HCO3 dimers. Methods for be estimated. The two-stage model ages for the individual producing and characterizing H2CO3 oligomers to establish samples range from ∼1 Ma up to ∼4 Ma after CAI formation their stability are discussed. and are consistent with the ~4566.5 Ma age obtained from the 53Mn-53Cr whole rock isochron (recalculated from [5] relative to angrite D'Orbigny) and with Mg isotope evidence for differentiation of the EPB at ∼3 Ma after CAI formation. Cumulate eucrites, in spite of having highly variable Hf/W ratios, are characterized by constant ε182W values of ∼18, indicating that their different Hf/W ratios were established later than ~60 Ma after CAI formation, probably related to the presence of ilmenite in the cumulate eucrite source. This and the >60 Ma age is consistent with results from 147Sm-143Nd and 176Lu-177Hf whole-rock isochrons corresponding to an age of ~100 Ma after CAI formation [4].
[1] Bizzarro et al. (2005) ApJ 632, L41-L44. [2] Halliday & Porcelli (2001) EPSL 192, 545-559. [3] Quitté et al. (2000) EPSL 184, 83-94. [4] Blichert-Toft et al. (2002) EPSL 204, 167-181. [5] Lugmair & Shukolyukov (1998) GCA 62, 2863- 2886. A954 Goldschmidt Conference Abstracts 2008
Comparative chemical versus isotopic Experimental calibration of zircon- dating of monazites quartz oxygen isotope fractionation 1 1 2 3 1 2 1 R. TRACY *, C. LOEHN , P. DAHL , M. HAMILTON , D. TRAIL *, I.N. BINDEMAN AND E.B. WATSON 4 4 4 F. MAZDAB , J. ALEINIKOFF , J. WOODEN 1 5 Department of Earth & Environmental Sciences, Rensselaer AND B. MILLER Polytechnic Institute, Troy, NY 12180, USA 1Geosciences, Virginia Tech, Blacksburg, VA 24061 (*correspondence: [email protected]) (*correspondence: [email protected]) 2Department of Geological Sciences, University of Oregon, 2Geology, Kent State Univ., Kent OH 44242 Eugene, OR, 97403, USA 3Univ. of Toronto, Toronto ON, Canada M5S 3B1 4USGS/Stanford SHRIMP Lab, Stanford CA 94305 Zircon is a common accessory phase occurring in many 5Texas A&M Univ., College Station TX 77843 crustal rocks, and is often found with quartz. The δ18O values of both minerals have been used to understand petrogenesis, Background and to constrain the provenance of grains no longer associated Monazites are widely used for U-Pb dating of igneous and with their host rocks. In order to explore these minerals metamorphic rocks and events. Monazite (mnz) U-Th-Pb further, we report the first direct experimental characterization dating that does not require isotopic data has recently been of oxygen isotope equilibrium fractionation. successfully utilized to characterize metamorphic events. In Experiments (700-950°C; 10-20 kbar; 50-600 hrs.) were this “chemical” dating method, high-precision electron designed so that both phases would crystallize in chemical microprobe analyses with a significant spatial-resolution communication, but would be easily separable for isotope advantage over isotopic methods have been used to date in situ analysis. Zircon and quartz fractions were cleaned, and zones in partially recrystallized mnz grains that record timing oxygen isotope analyses were performed on a Finnigan MAT of partial recrystallization events. This technique can produce 253 mass spectrometer by reacting zircon and quartz with a relatively complete picture of multiple tectono-thermal BrF5 using a 25W CO2 laser line. Thus far, our data suggest an events in a metamorphic terrane or be used to decipher A-value which is in better agreement with empirical results [1] xenocryst-magmatic overgrowth relations in granitic plutons. than with the indirect experimental calibration derived from The chemical method, however, remains controver-sial and in zircon-water fractionation experiments [2]. this presentation we report direct comparative results of in situ A robust calibration would provide a new tool for mineral isotopic (SIMS, SHRIMP), bulk isotopic (ID-TIMS), and thermometry, and would have direct application to chemical (EMP) dating of the same mnz grains in rocks characterizing oxygen equilibrium/disequilibrium processes in ranging from 2850 to about 300 Ma. We present analysis of petrological systems. In addition, because zircon is resistant to uncertainties in chemical dating, including analytical errors chemical alteration and physical breakdown during and effects of common-lead correction. weathering, it is often used to constrain protolith origin(s). Our data provide an indirect means to determine δ18O quartz Results values of the host rock – an important characterizing feature – Case studies include (1) Archean and Paleoproterozoic provided zircon crystallization temperatures [3] and δ18O mnz from the Tobacco Root Mountains, MT, (2) Mesopro- zircon values are determined, and can be assumed not to have terozoic mnz from a shear zone in NC, (3) Devonian mnz been compromised by post-crystallization diffusive exchange. from granite, VT, and (4) Mississippian mnz from pegmatite, The above methodology could also be applied to quartz MA. In each case, dates are comparable within uncertainty, inclusions in zircon which may be inaccessible to isotope except where isotopic ages reflect mixing of two age zones. analysis because of size, or altered by subsequent overprinting.
[1] Valley et al. (2003) Geochim. Cosmochim. Acta. 67, 3257- 3266. [2] Krylov et al. (2002) European Journal of Mineralogy 14, 849-853. [3] Watson et al. (2006) Contrib. Mineral. Petrol. 151, 413-433. Goldschmidt Conference Abstracts 2008 A955
Thermochronologic “hearing” of the The noble gas composition of roots of Caledonian Mountains of the the Earth’s mantle
Central Asian fold belt: Are they M. TRIELOFF parts of a single orogen? Mineralogisches Institut Universität Heidelberg, Heidelberg, 1 1 1 Germany ([email protected]) A.V. TRAVIN , D.S. YUDIN , A.G. VLADIMIROV , 1 1 N.I. VOLKOVA , S.V. KHROMYKH , 2 2 Defining the noble gas isotopic state of the terrestrial A.S. MEKHONOSHIN AND T.B. KOLOTILINA mantle is of primary importance to elucidate origin, evolution 1Institute of Geology and Mineralogy SB RAS, Novosibirsk, and geodynamics of the Earth [1]. Important advances have Russia ([email protected]) been achieved in the last decade: It was recognized that the 2Institute of Geochemistry SB RAS, Irkutsk, Russia Earth acquired solar wind gases (He, Ne-B) by solar ([email protected]) corpuscular radiation [1-5], implying major accretion after protoplanetary disk dissipation. Nonradiogenic isotopes of Ar, The Central Asian fold belt incorporates rock units derived Kr, Xe have rather atmosphere-like composition [2, 6-8], from a variety of geodynamic settings, evolved the Paleo- except for a minor solar or planetary Xe component [8], Asian Ocean (PAO). One of the key events in the history of raising the possibility of substantial recycling into the mantle. the PAO was at the Late Cambrian − Ordovitian. At the Mantle plumes are now well characterized: Hawaii [2], western framing of the Siberian Craton this time is marked by Iceland [2, 9], Réunion [5], or the fossil Kola plume [10]. collision of island arcs and microcontinents, ridge subduction Moreover, the composition of the subcontinental lithospheric and closure of interarc, backarc basins. As a result the mantle was determined for several localities using peridotitic formation of large scale orogenic belts of different rocks [4, 11-14]. It appears that important processes are the configuration have been suggested. We assume that belonging local occurrence and mixing of variably fractionated different of different accretion-collision structures to single large-scale mantle components [4-6, 11-16], occasionally influenced by orogen can be clarified on the base of reconstruction of their more or less fractionated atmospheric and crustal components, tectonothermal history. possibly related to subduction and fluid transport in the lower We consider radiogenic isotope geochronology data on crust and uppermost mantle [13-17]. A precondition to trace Caledonian Olkhonskaya and Western Sangilen (Tuva) these processes is studies advancing our knowledge of accretion-collision structures and compare them with crystal/melt/gas partitioning [18-20]. published data on Slyudyansky crystalline complex, Derba terrain, Bayankhongor Ophiolite Zone (Mongolia). [1] Ozima & Podosek (2002) Noble gas geochemistry. The thermal histories of similar duration (~ 100 Ma) for [2] Trieloff et al. (2000) Science 288, 1036-1038. all five accretion-collision structures are reconstructed. The [3] Ballentine et al. (2005) Nature 433, 33. [4] Buikin et al. coincidence of the age of at least four successive stages in (2005) Earth Planet. Sci. Lett. 230, 143-162. [5] Hopp & their tectonothermal histories is observed. It seems to be Trieloff (2005) Earth Planet. Sci. Lett. 240, 573-588. convincing to assume that studied accretion-collision [6] Trieloff & Kunz (2005) Phys. Earth Planet. Int. 148, 13- structures have been parts of the single large-scale orogenic 38. [7] Kunz et al. (1998) Science 280, 877-880 [8] Holland & belt formed at the scene of Vendian − Early Paleozoic island Ballentine (2006) Nature 441, 186-191. [9] Stuart et al. (2003) arc system which bordered the Siberian Craton. Nature 424, 57-59. [10] Marty et al. (1998) Earth Plan. Sci. Lett. 164, 179-192. [11] Matsumoto et al. (1997) Nature 388, This work is carried out with financial support of the 162-164. [12] Hopp et al. (2004) Earth Planet. Sci. Lett. 219, Russian Fund of Fundamental Researches, grants 06-05- 61-76. [13] Hopp et al. (2007) Chem. Geol. 240, 36-53. 65052, 07-05-00980, 08-05-00204, 08-05-00733. [14] Hopp et al. (2007) Earth Plan. Sci. Lett. 261, 635-648. [15] Kurz et al. (2005) Earth Plan. Sci. Lett. 232, 125-142. [16] Harrison et al. (2003) Geochem. Geophys. Geosys. 4, 1023. [17] Schwarz et al. (2005) Contr. Min. Petr. 149, 675- 684. [18] Brooker (2003) Nature 423, 738-741. [19] Heber et al. (2007) Geochim. Cosmochim. Acta 71, 1041-1061. [20] Moreira & Sarda (2000) Earth Plan. Sci. Lett. 176, 375- 386. A956 Goldschmidt Conference Abstracts 2008
Origin of Ti isotope heterogeneity in ‘Clumped isotope’ thermometery in the protoplanetary disk foraminifera 1 1 1 1,2 2 2 A. TRINQUIER , M. BIZZARRO , D. ULFBECK , A. TRIPATI *, N. THIAGARAJAN AND J. EILER 2 2 3 T. ELLIOTT , C.D. COATH , R.A. MENDYBAEV , 1 3 4 Department of Earth Sciences, University of Cambridge, F.M. RICHTER AND A.N. KROT Cambridge, UK CB2 3EQ 1Geological Museum, University of Copenhagen, Denmark (*correspondence: [email protected]) 2Bristol Isotope Group, University of Bristol, UK 2Geological and Planetary Sciences Division, California 3Department of Geophysical Sciences, University of Chicago, Institute of Technology, Pasadena, CA 91125 USA ([email protected], [email protected], 4HIGP, University of Hawaii at Manoa, USA [email protected])
Isotopic anomalies of nucleosynthetic origin in meteorites Accurate constraints on past ocean temperature and provide a record of the stellar sources that contributed material composition are critical for documenting climate change and to the solar system’s parental molecular cloud. These resolving its causes. Most inorganic and organic geochemical heterogeneities are commonly interpreted as reflecting paleothermometers are fundamentally underconstrained inefficient thermal processing of presolar dust. Owing to its because they reflect seawater composition as well as refractory nature, Ti is ideally suited to track the nature and temperature. In addition, some of the most frequently used extent of nucleosynthetic variability in early-formed solids. thermometers — 18O/16O and Mg/Ca ratios in biogenic Here, we report high-precision Ti isotope measurements of carbonate — deviate from inorganic calibrations and can various meteorites obtained by MC-ICPMS. exhibit species-specific temperature dependencies. These Except for enstatite chondrites and lunar meteorites, all offsets or ‘vital effects’ are poorly understood and lend an bulk meteorites and meteoritic components display correlated unquantifiable source of uncertainty to reconstructions of past anomalies in 50Ti and 46Ti, when using the 49Ti/47Ti ratio to temperature. Here we report ‘clumped isotope’ [1] internally correct for instrumental mass bias. Carbonaceous measurements of benthic and planktic foraminifera from chondrites (CC) exhibit excesses in 50,46Ti, while ordinary sediment core-tops showing that the proportion of 13C-18O chondrites (OC), most achondrite meteorites and CC bonds in calcite and aragonite shells exhibits the same chondrules record deficits. Fine- and coarse-grained CAIs, and temperature dependence as inorganic calcite. The ‘clumping’ AOAs identically display the most extreme 50,46Ti of heavy isotopes into bonds with each other is independent of enrichments. Stepwise leaching of bulk CCs using acids of the isotopic composition of the water in which the mineral increasing strengths reveal 46Ti-50Ti excesses/deficits that precipitated, and thus avoids the ambiguity intrinsic to some resonate with previously published 54Cr variations for the other thermometers. These observations suggest the clumped same meteorites. isotope thermometer can yield accurate determinations of past Our results suggest that the carrier of the anomalous 46,50Ti seawater temperature, even when applied to the remains of and, by extension, 54Cr is a non-refractory presolar silicate that extinct taxa. The lack of discernable ‘vital effects’ in originated in AGB stars. This component is most enriched in foraminifera and other forms of biogenic calcite and aragonite the CAI-forming reservoir, but depleted in the accretion [1-4] indicates that these organisms precipitate calcium regions of differentiated planetesimals, OCs and the terrestrial carbonate in isotopic equilibrium with the dissolved inorganic planets. High-temperature experiments under vacuum carbon (DIC) pool from which they calcify. The lack of conditions of CC matrices show that thermal processing at difference between calcite and aragonite may indicate that the temperatures ~1000°C can result in the loss of the 46,50Ti-54Cr ‘clumping’ of these heavy isotopes into bonds with each other carrier by sublimation. This suggests that nucleosynthetic reflects the thermodynamically-controlled exchange of stable variability in solar system objects may not reflect primordial isotopes amongst DIC species in water, rather than similar heterogeneity, but instead selective thermal processing of their exchange equilibria within the solid precipitates [5]. precursor material in the protoplanetary disk. [1] Eiler (2007) EPSL 262, 309-327. [2] Ghosh et al. (2006) Geochim. Cosmochim. Acta 70, 1439-1456. [3] Came et al. (2007) Nature 449, 198-201. [4] Ghosh et al. (2007) Geochim. Cosmochim. Acta 71, 2736-2744. [5] Schauble et al. (2006) Geochim. Cosmochim. Acta 70, 1439-1456. Goldschmidt Conference Abstracts 2008 A957
Origin of diagenetic fluids in the In situ conodont thermometry: SE Mexican oil fields Did cooler oceans trigger the Great 1 1 2 3 J. TRITLLA , G. LEVRESSE , D. BANKS , J. PIRONON , Ordovician Biodiversification Event? 3 1 J. BOURDET AND A. CARRILLO-CHÁVEZ 1,2 1 JULIE TROTTER *, IAN WILLIAMS , 3 4 1Prog. Geofluidos, CGEO-UNAM, 76230, Querétaro, Mexico CHRISTOPHER BARNES , CHRISTOPHE LÉCUYER 1 2School of Earth and Environment, Univ. of Leeds, Leeds, UK AND ROBERT NICOLL 3Nancy-Univ. CNRS-CREGU, Vandoeuvre-les-Nancy, France 1Research School of Earth Sciences, The Australian National
University, 0200, Canberra, Australia Several world-class oil fields are located inland and 2CSIRO Petroleum, North Ryde, NSW, Australia offshore the Gulf of Mexico, SE Mexico. The host carbonates (*correspondence:[email protected]) had a complex diagenetic history, including pervasive 3School of Earth and Ocean Sciences, University of Victoria, dolomitization, fragile and hydraulic fracturing and breccia Victoria, B.C., Canada V8W 2Y2.-AL formation, several generations of cement, anhydrite injection 4Laboratoire CNRS UMR 5125, Université Claude Bernard and late hydrocarbon impregnation. Dolomitization and Lyon 1, F-69622 Villeurbanne, France related cements are controlled by major structures and primary sedimentary textures. Mesozoic tectonics were characterized The Great Ordovician Biodiversification Event saw the by passive margin development and early salt mobilization; greatest evolutionary radiations of life in Earth’s history with the Tertiary, post-Chixchulub tectonic history is marked by the sudden explosion of marine bio-originations increasing complex tectonics, due to an ocean-continent oblique family and genus numbers x3-4 fold. During this event, the collision, the formation of a Tertiary foreland basin and very marine Cambrian Evolutionary Fauna was replaced by more active salt and clay diapirism. Several researchers link the salt complex Palaeozoic and Modern Evolutionary Faunas, diapirism to the mobilization and upflow of dolomitizing establishing the blueprint for today’s marine lineages. fluids, and a heat increase causing organic matter maturation A plausible cause for this event is now apparent – here we and oil expulsion. show that ‘global’ biodiversity patterns are strongly coupled to A fluid inclusions study of diagenetic cements (dolomite global climate change. Previously, Supergreenhouse and calcite) samples taken from oil wells throughout the conditions were thought to have prevailed during the mesozoic sedimentary sequence was undertaken. Fluid Ordovician, with unrealistically hot ocean temperatures inclusions were classified as two-phase brine-bearing (L -V), AQ (50–70°C), or that seawater δ18O was markedly different from two-phase oil-bearing (L -V); and poly-phase (L -L -V- HC AQ HC today. We present a new δ18O palaeoclimate record derived S). The petroleum inclusions belong to the “black oil” family, from conodont bioapatite analysed in situ using the while the majority of aqueous inclusions are methane-depleted SHRIMP II ion microprobe. Early Ordovician to Silurian with salinities between 8 and 18 wt% eq. NaCl and no conodonts from tropical Gondwana and Laurentia give evidence of hypersaline brines. Halogen data obtained from internally consistent results within individual specimens, both dolomite cement and late-calcite plot very close and populations, and across geographically disparate sites thereby parallel to the seawater evaporation trend in a Na/Br vs Cl/Br recording a global temporal trend. Three climatic regimes are diagram, past the point of halite precipitation, clustering evident in the Ordovician which coincide with known around the point of epsomite-sylvite precipitation. This biodiversity patterns. Early Ordovician oceans cooled steadily excludes the involvement of secondary brines from the (~40–30˚C) over ~25 million years as pelagic clades emerged. dissolution of salt diapirs. The salinities of the fluids are too From the Mid to Late Ordovician, temperatures stabilised at low for this degree of seawater evaporation, indicating the modern equatorial values (~28–32°C) providing evaporite-related fluids probably mixed with dilute, seawater- unprecedented opportunities for marine groups to diversify like fluids during diagenesis. and fully exploit the available ecospace. A rapid Late
Ordovician fall in temperatures led to widespread extinctions We acknowledge PEMEX-PEP and, specially. Ing. A. during the Hirnantian glaciation, with modern equatorial Escalera, for their invaluable help while doing this research. temperatures restored by the Early Silurian. This new climate record with constant δ18O seawater composition shows that fundamental step-changes in Ordovician biodiversity patterns are closely linked to global temperature changes. A958 Goldschmidt Conference Abstracts 2008
Textures of progressive garnet Modelin Phosphorus cycling and growth recorded in Ti-rich Carbon burial during Cretaceous metagabbros from the southern oceanic anoxic events
Tongbai Mountains, central China I. TSANDEV*, C.P. SLOMP, P. KRAAL 1 2 3 AND P. VAN CAPPELLEN CHIN-HO TSAI *, HANWEN ZHOU , YOSHIYUKI IIZUKA 4 AND RACHEL J. BEANE Utrecht University, Utrecht, Netherlands (*correspondence: [email protected]) 1Institute of Earth Sciences, National Hualien University of
Education, Hualien 970, Taiwan ([email protected]) During the warm humid world of the Cretaceous, there 2Faculty of Earth Sciences, China University of Geosciences were episodes of oxygen depletion in the deep ocean (Wuhan), PR China associated with enhanced organic carbon burial in sediments 3Institute of Earth Sciences, Academia Sinica, Nankang, (black shales). In this study, we use a box model of the Taipei 115, Taiwan oceanic phosphorus (P), organic carbon and oxygen cycles to 4Geology Department, Bowdoin College, USA test the hypothesis that enhanced delivery of phosphorus from the continents can trigger deep ocean oxygen depletion A suite of garnet-bearing Ti-rich metagabbros crops out in (anoxia) and black shale formation under Cretaceous ocean the southern Tongbai Mountains, in which one of the largest conditions. rutile ore deposits in China is located. Field occurrence shows We find that, for the Cretaceous ocean, with large that the garnet-bearing metabasites were derived from continental shelves, slow oceanic overturning and high sea gabbroic plutons with internal compositional variation. Major surface temperatures, oceanic anoxic events (OAEs) can be mineral constituents are garnet, amphibole, and rutile. Rutile is triggered by enhanced P supply from land and that the system remarkably abundant and relatively large compared to those in is particularly sensitive to oceanic mixing conditions. In this most metabasites. Minor, accessory, or secondary minerals scenario, the deep sea becomes completely anoxic, while the include paragonite, albite, chlorite, titanite, epidote, shelves attain only partial anoxia. Sedimentary burial differs clinozoisite, quartz, ilmenite, pyrite, apatite, carbonate, and between the shelves and open ocean: while organic carbon zircon. In some relatively more felsic samples, albite and burial is enhanced in both regions, deep sea reactive P burial paragonite are the major phases. Foliations, if existing, are decreases dramatically under anoxia, but not on the shelves, mainly defined by paragonite and epidote. Whole-rock XRF where oxygen depletion is only partial. data show high TiO content, up to 4.2 wt %. Petrographic 2 Furthermore, our model results suggest that OAEs can be features show at least three textural types of garnet: (1) sustained by P recycling from sediments under low oxygen aggregated porphyroblasts (Type I), commonly forming a conditions. We find that, to terminate the anoxic event, a atoll-like chain which surrounds rutile, green amphibole, and feedback from accumulating atmospheric oxygen is required. quartz; (2) relatively more euhedral but individual This atmospheric oxygen cycle needs to be further modulated porphyroblasts (Type II), mainly in more felsic samples; and by land processes such as forest fires and oxidative (3) fine-grained, optically-anisotropic neoblasts (Type III) in weathering. Our model findings are corroborated by C and P strange dendritic alignment, with high-angle connecting with burial data from the geological record for OAE-2 (~94 Myrs the Type I garnet chain and pointing inwards. Type II garnet BP). porphyroblasts seem to have been grown from coalescence of Through a sensitivity analysis we identified two necessary smaller precursors. Some Type III garnet grains contain criteria for OAEs: low mixing of surface and deep waters elongated ilmenite rods. Element mapping analysis on Type I (poor ocean ventilation) and enhanced sedimentary P with EPMA shows weak zoning. In general, Type I is rich in recycling under low oxygen conditions. When these criteria almandine (62-77 mol %) and grossular (11-26 %). An EBSD are met, ocean anoxia is a robust result to a mild increase of study has been performed on three samples from this suite. continental supply of nutrients, under a wide range of Preliminary results show that, crystallographically, Type I environmental conditions. chain-like garnets are randomly oriented. There are significant grain boundaries between Type I and Type III garnets, indicating separate nucleation of the latter. The different garnet textures represent different stages of metamorphic recrystallization or reaction. Goldschmidt Conference Abstracts 2008 A959
Low δ57Fe values record the onset of Geochemical mapping in Kobe area, Palaeoproterozoic bacterial southwest Japan: Elemental manganese reduction behaviors and controlling factors 1 2 1 HARILAOS TSIKOS *, ALAN MATTHEWS , JOHN MOORE M. TSUBOI*, K. IMAMURA, Y. KAGAWA, M. OKABE, 2 1 AND YIGAL EREL K. OKAUCHI , S. OSAKI, H. SHIBATA, M. TANAKA, Y. TOGO AND H. YAMAMURA 1Department of Geology, Rhodes University, South Africa (*corresponding author: [email protected]) Department of Chemistry, School of Science and Technology, 2Institute of Earth Sciences, Hebrew University, Jerusalem Kwansei Gakuin University, Sanda, Hyogo, 669-1337, Japan Iron and manganese share similar biogeochemical (*correspondence: [email protected]) properties in modern near-surface environments, whereas Archaean and Palaeoproterozoic banded iron formations (BIF) Environmental assessment of the Kobe area, Kinki district, are generally devoid of Mn. We present an Fe-isotope study of southwest Japan has been made using geochemical mapping the transition from BIF to Mn-rich deposition in the Hotazel of stream sediments. The area consists mainly of the Formation, a unique inter-layered sequence of BIF and Cretaceous granitoids; Cretaceous volcanic clasts of the Arima Mn-rich sediment in the uppermost part of the Group; sandstone, mudstone, chert, limestone and basalts of Palaeoproterozoic (2.7-2.4 Ga) Transvaal Supergroup of South the Jurassic accretionary complex of the Tamba belt; Africa. Virtually unmetamorphosed and unaltered portions of sandstone, conglomerate, mudstone and tuffs of the Miocene the Hotazel sequence consist of chert-magnetite-ankerite- Kobe Group; and Pliocene to Pleistocene sand, gravel and calcite-Fe silicate BIF that is cyclically intercalated with three clays of the Osaka Group. Some of the closed silver and manganiferous lutite layers dominated by Mn carbonate- copper mines are in the southeastern part of the study area. braunite-hematite. The host BIF has an average bulk δ57Fe Stream sediments were collected using an 80-mesh (IRMM) of –1.70 ± 0.80‰, and in areas where low- (180 µm) sieve in wet condition at each sampling site after the temperature hydrothermal carbonate leaching and oxidation method of Tanaka et al. [1]. A total of 322 stream sediments are evident, it gives a comparable range of δ57Fe values (–1.98 over an approximately 2000 km2 in the Kobe area were ± 0.58‰). Lithological units transitional to the manganese analyzed for 25 elements including Al, As, Ba, Ca, Co, Cr, layers (‘hematite lutites’), as well as the Mn lutites Cu, Fe, K, Mg, Mn, Na, Nb, Ni, P, Pb, Rb, Si, Sr, Th, Ti, V, themselves, give low δ57Fe values of –3.00 ± 0.31‰. These Y, Zn, Zr with X-ray fluorescence spectrometry (XRF) and are the lowest δ57Fe values recorded in early Precambrian loss-on-ignition. Distributions of the major elements including hematite-rich sedimentary rocks. δ57Fe values of the BIF are Si, K, Na, Ca, Mg, Ti, Fe, Mn, Al, P are controlled by the lower than magnetite-siderite-bearing BIF of the older chemical composition of the country rocks. The concentration Kuruman and Griquatown Formations of the Transvaal of Zr is high (270 ppm ~ 4930 ppm) in sediments of the Sanda Supergroup [1]. basin area because of the zircon sedimentation. Heavy metals Following Johnson et al. [1], we interpret the δ57Fe data including As, Cu, Ni, Pb, Zn give higher concentration spots for the Hotazel BIF to reflect fractionation effects driven by in downstream regions of the closed mines. dissimilatory bacterial Fe reduction (DIR) in an isotopically Combining these geochemical map analyses and surface evolved Fe(II) reservoir. The presence of low δ57Fe hematite geology, the distribution patterns of the elements are mainly in the Mn-rich layers, in conjunction with the co-abundance of controlled by three factors: i) wide-areal regional elemental low δ13C, Fe-poor manganiferous carbonates (δ13C(PDB): - distribution powered by surface geology, ii) local distribution 12.5 to -8‰ [2]) suggests that during intervals of increased affected by sedimentation of the heavy minerals in the basin, Mn precipitation, DIR was curtailed in favour of bacterial Mn and iii) spot deposition of ore minerals nearby the local mines. reduction for the first time on that scale in Earth’s history. The hematite in these sediments would chemically represent the [1] Tanaka et al. (1994) J. Earth Planet. Sci. Nagoya Univ. 41, original Fe(III) precipitate and its isotope composition would 1-31. approximate that of the dissolved Fe(II) pool, assuming that no fractionation effects accompanied aqueous Fe(II) oxidation.
[1] Johnson et al. (2008) GCA 72, 151-169. [2] Tsikos et al. (2003) Econ. Geol. 98, 1449-1462. A960 Goldschmidt Conference Abstracts 2008
Geochemical study of chromian Quadruple Sulfur isotope analysis of spinel bearing alkaline Matsue Basalt ~2.9 Ga Pongola Supergroup 1 2 1 3 in the Shimane Prefecture, S. TSURUOKA , Y. UENO , T. KOMIYA , N. YOSHIDA 1 southwest Japan arc AND S. MARUYAMA 1Department of Earth & Planetary Sciences, Tokyo Institute of T. TSUBOTA* AND I. MATSUMOTO Technology, Japan ([email protected]) Department of Education, Shimane University, Matsue, Japan 2Global Edge Institute, Tokyo Institute of Technology, Japan (*correspondence: [email protected]) 3Department of Environmental Science and Technology, Tokyo Institute of Technology, Japan Introduction Matsue city is located in Japan Sea coast side of southwest Sulfur Mass-Independent-Fractionation (MIF) is observed Japan arc. There are many alkaline basic-intermediate lavas only in geological records older than 2.0 Ga, but not in that we called “Matsue Basalts” in Matsue city area. The younger strata (e.g. [1]). This unique MIF signature is known activity of the Matsue Basalt is about 10 Ma ago. Matsue to be caused by photochemical reactions of sulfurous gas, and basalt basically consists of 6 basic lavas and some of its thus suggests oxygen-poor atmosphere (i.e. weak UV pyrocrastic deposit (sandstone and tuff) [1, 2]. The purpose of shielding) before 2.0 Ga. However, recent investigations this study is clarifying geochemical characteristics of Matsue demonstrated that no large MIF has been observed in a period basalt. We here report the Bulk chemical composition, from 3.0 to 2.8 Ga [2, 3]. This implies a possibility that the Mineral assemblage and mineral chemistry of Matsue Basalt. oxygen content of the atmosphere may have increased This is first report of systematic chemical study about Matsue tentatively at around 2.9 Ga [2, 3]. Alternatively, Farquhar Basalt. And we found chromian spinels in the many rock et al. [4] interpreted that presence of “weak” MIF at 2.9 Ga do samples. not imply oxygen rise, but change of atmospheric chemistry. In order to evaluate these scenarios, it is essential to extend Results and Discussion multiple sulfur isotope data for geologically and According to our result of bulk rock chemical petrographically well-characterized 3.0 to 2.8 Ga sedimentary compositions, Matsue Basalt is divided into 6 groups, which rocks. Here, we report quadruple sulfur isotope analysis of consist of 3 basalt groups (Chausuyama, Hanamagari and wide range of lithotypes (conglomerate, sandstone, siltstone, Agenogi groups), 2 basaltic andesite groups (Tsuda and dolomitic sandstone, arenaceous dolostone and stromatolitic Rakuzan groups) and 1 andesite group (Toukodai group). dolostone) occurring in 2985-2837 Ma Nsuse and Mozaan However it was clarified that it was chemically the same Groups, South Africa. The ∆33S values of sulfides of Mozaan feature as Tsuda and Rakuzan groups among Matsue Basalt. Group and Nsuze Group are from -0.41 to 0.13‰ and –0.11 to That is, Matsue Basalt chemically consists of 5 groups. 0.35‰ respectively. Examining ∆33S/∆36S relationships, it Chausuyama and Agenogi basalts show particularly with was found that 5 samples of Mozaan Group and 7 of Nsuze respect to their low FeO*/MgO ratios and high Cr content. Group show small but clear MIF signature. Furthermore, And these two basalts have chromian spinels in and around isotope ratios of Nsuze and Mozaan sulfides exhibit two olivine grains. mutually distinctive areas in a plot of ∆33S-vs-∆36S Chromian spinels from Chausuyama and Agenogi basalts irrespective to their lithological variety, suggesting temporal have Cr# (Cr/(Cr+Al) atomic ratio) of 0.16-0.40, and olivines (not geographical) change of chemistry responsible for these from these basalts have Fo of 88-76. Arai [3, 4] proposed that MIF. Our results do not conflict with “the oxygen poor -5 Fo-Cr# relations depend on the tectonic setting, due to atmosphere (pO2<10 PAL) model”. It is plausible that the differing melting conditions (pressure, temprature and water sulfate concentration of 3.0-2.8 Ga seawater was low enough vapor conditions). That is Chausuyama and Agenogi basalts of to remain MIF signatures. However, the ∆33S and ∆36S values Matsue Basalt derived from the relativery depleated lerzolitic of sulfides in carbonate of Nsuze Group are very similar to mantle. those of modern sulfate aerosols [5]. This implies Nsuze stage may represent a period of low but relatively rising atmospheric -5 [1] Miyajima et al. (1972) Mem. Fac. Lit. & Sci., shimane oxygen (pO2>10 PAL). Univ., Nat. sci. 5, 131-138. [2] Tsubota et al. (2007) Annual meeting of Japan Soc. of Earth Sci. Edu, Abstract Vol. 46-47. [1] Farquhar & Wing (2003) [2] Ohmoto et al. (2006) [3] Ono [3] Arai (1987) N. Jb. Miner. Mh., 347-354. [4] Arai (1994) et al. (2006a) [4] Farquhar et al. (2007) [5] Romeo & J. Volcanol. Geotherm. Res. 59, 279-294. Thiemens (2003) Goldschmidt Conference Abstracts 2008 A961
Rapid generation of felsic magmas at Distributions of organic compounds ~ 370 Ma in the New Zealand sector in Dongsheng sedimentary Uranium of the Gondwana margin ore deposits, China 1 2 1 1,2 1,2 ANDY TULLOCH * AND JAHANDAR RAMEZANI JINCAI TUO , MINGFENG ZHANG AND WANYUN MA 1 1GNS Science, Private Bag 1930, Dunedin, New Zealand Key Laboratory of Gas Geochemistry, Chinese Academy of (*correspondence [email protected]) Sciences, Lanzhou, 730000, China ([email protected]) 2 2Earth, Atmospheric and Planetary Sciences, MIT, MA 02139, Graduate University of the Chinese Academy of Sciences, USA ([email protected]) Beijing, 100039, China
Determination of crustal growth rates in continental Organic matter (OM) associated with the Dongsheng margin arcs requires high-precision geochronology combined sedimentary uranium ore deposits was characterized by Rock- with realistic estimates for magma volume and the proportion Eval, gas chromatography-mass spectrometry and stable of recycled crust. carbon isotope analysis. The OM in all of the analyzed Paleozoic magmatism in New Zealand is dominated by the samples is Type III with Ro less than 0.6%, indicating that the Karamea Suite S-type granite-granodiorite-tonalite plutons OM associated with these uranium ore deposits can be which form much of the Karamea Batholith. New high classified as a poor hydrocarbon source potential for oil and precision, single zircon, U-Pb ID-TIMS dates for Karamea gas. n-Alkanes in the organic-rich strata are characterized by a plutons suggest that this ~3300 km2 suite was emplaced in a higher relative abundance of high-molecular-weight (HMW) ≤ 2 Ma magmatic burst between 368.27 ± 0.11 Ma and homologues and are dominated by C25, C27 or C29 with distinct 370.10 ± 0.17 Ma (internal 2σ errors). Estimating the odd-to-even carbon number predominances from C23 to C29. thickness of the batholith at 10-15 km, these data indicate a On the contrary, in the sandstone/siltstone samples, the n- flux rate of 83 to 124 km3/km arc/Ma, an order of magnitude alkanes have a higher relative abundance of medium- greater than some estimates for long-term continental margin molecular-weight homologues and are dominated by C22 with arc averages (e.g. [1, 2]). no or only slight odd-to-even carbon number predominances Significant involvement of Early Paleozoic from C23 to C29. Methyl alkanoates in the sandstone/siltstone metasedimentary crust in magma generation is indicated by Sr, extracts range from C14 to C30, maximizing at C16, with a Nd, and O isotopic compositions, as well as inherited zircon. strong even carbon number predominance, but in the organic- Minor volumes of coeval HiSY (Sr/Y>40; TTG-like or rich layers the HMW homologues are higher, maximizing at adakitic) plutons probably reflect partial melting of a mafic C24, C26 or C28, also with an even predominance above C22. crustal component. However, the rapidity of lower crustal n-Alkanes in the sandstone/siltstone sequence are significantly 13 melting also necessitates thermal involvement of significant depleted in C relative to n-alkanes in most of the organic- volumes of juvenile mantle. An intra-arc or back-arc rich strata. Diasterenes, ββ-hopanes and hopenes are present in extensional setting, involving rapid influx of asthenospheric nearly all the organic-rich sediments but in the magmas into the lower crust by slab roll-back or foundering, sandstone/siltstone samples they occur as the geologically appears likely. We will attempt to reconcile the apparent high mature isomers. The distribution patterns of the branched magmatic flux and inferred mantle involvement with the high alkylbenzenes also show significant differences in different proportion of recycled crust. kinds of samples. The differences in organic compound Given the indicated high thermal flux into the lower crust, distributions between the uranium-hosted sandstone and no- it is probable that the upper crust was also affected by high uranium organic-rich strata indicate that the organic matter in heat flow and hydrothermal alteration. Thus, the Karamea the organic-rich strata did not have an important or direct role event may have led to at least some of the Paleozoic in the precipitation of uranium ore in the sandstone. But an Au-mineralisation in western New Zealand. indirect role cannot be excluded, because OM alteration can create and maintain a reducing environment favorable for [1] Ducea (2001) GSA Today 11, 4-10. [2] Francis & preconcentration of U and subsequent precipitation of uranium Hawkesworth (1994) Geological Society of London 151, 845- minerals. 854. The project was supported by China 973 National Key Research and Development Program (Grant Number: 2003CB214606) and the China National Natural Science Foundation (Grant Number: 40773052). A962 Goldschmidt Conference Abstracts 2008
Genesis of high-Mg andesites at Seasonal and interannual changes in White Island, New Zealand Ca and Mg of dripping waters in
SIMON TURNER AND BERNARD WOOD Kaite Cave (Spain) 1 1 2 GEMOC, Department of Earth and Planetary Sciences, M.J. TURRERO , A. GARRALÓN , J. MARTÍN-CHIVELET , 1 1 3 Macquarie University, Sydney, NSW 2109, Australia P. GÓMEZ , L.SÁNCHEZ AND A.I. ORTEGA ([email protected], [email protected]) 1CIEMAT, Dpto. de Medioambiente, 28040 Madrid, Spain
([email protected], [email protected], On White Island, New Zealand, the intensified period of [email protected], [email protected]) strombolian-volcanian and phreatomagmatic explosive 2UCM, Dpto. Estratigrafía, Fac. Cc. Geológicas, 2840 Madrid, activity that commenced in March 1977 led to eruption of Spain ([email protected]) unusually primitive, high-Mg andesites. These are Fo 80-93 3UBU, Dpto. Historia y Geografía, Fac. Humanidades, 09001 olivine-saturated rocks that have MgO contents up to 10% Burgos, Spain ([email protected]) (Mg# = 65-71) and SiO2 of 56-58%. They have incompatible trace element characteristics that are typical of arc rocks. Kaite, a karstic cave of N Spain, features key advantages 87Sr/86Sr, 143Nd/144Nd and 176Hf/177Hf ratios (0.7049-0.7053, to establish a linkage between calcite precipitation and 0.51282-0.51266 and 0.28301-0.28298, respectively) are environmental variations. The site is characterized by a stable consistent with subducted sediment addition and/or crustal cave climate: the temperature is 10.40 ± 0.02 ºC and reflects input but there is no clear correlation of either isotope ratio the mean annual temperature outside the cave, the relative with MgO. The rocks have modest (3-10%) 238U excesses at humidity exceeds always 99 % and there are not significant air low (230Th/232Th) ratios (0.697 to 0.722). 226Ra-230Th currents. Two points with low and moderate-rapid drip rate disequilibria is also restricted but, unusually, includes both (KT-WL and KT-WR, respectively) were selected for the 226Ra excesses and deficits with (226Ra/230Th) = 0.94-1.07. study. (210Pb/226Ra) ranges from 0.98 to 1.52 requiring gas o Calcium concentration ranges from 0.82 to 2.17 mmol/L accumulation that may increase over time and with decreasing in KT-WL and from 2.17 to 3.57 mmol/L in KT-WR, with a MgO. Sr/Y and Tb/Yb ratios are both low and relatively declining concentration trend from 2002 to present in both invariant at 8 and 0.3, respectively, and along with the 238U sites. There is a cyclic pattern related to seasons, very excesses preclude an origin in which residual garnet was discernible in KT-WL and more erratic in KT-WR. Each intra- involved. The occurrence of some 226Ra deficits suggests the annual cycle has a [Ca2+] maximum peak during the summer, presence of residual amphibole during partial melting for when precipitation is lower and temperature is higher. some samples. Rapid magma ascent (to preserve the 226Ra In addition there are inter-annual variations of calcium disequilibria) limits the amount of possible melt – wall rock concentration, which present a similar pattern in the two interaction that might reduce source-derived Tb/Yb ratios and points monitored. In both cases there is an initial trend of in the mantle or raise 87Sr/86Sr in the crust. The White Island decreasing from the beginning of the monitoring program to high-Mg andesites did not form by partial melting of eclogite end-2005, which changes to a slight increase in 2006-2007. in the subducting Pacific plate. Their primitive, olivine- The trend of decreasing of calcium concentration through the saturated compositions suggest that their source was years correlates with the net decreasing of rainfall in the area peridotitic and experimental data suggest that melting at low from the beginning of the monitoring program and with an temperatures at 0.5-1.5 GPa and in the presence of elevated increasing in the temperature, especially that of colder alkalis can reconcile the high SiO and MgO of the rocks. 2 seasons. [Ca2+] does not correlate with [Mg2+] (r = 0.12 in KT- These conditions appear to be favoured by the location WL and r = 0.14 in KT-WR), reflecting that drip water should beneath continental, rather than oceanic lithosphere. not be affected by a dilution process when precipitation increases. Therefore, in response to the rainfall decrease, the inter-annual signal shows a progressive decrease in calcite growth. Relationships between Ca and Mg, Sr and Ba suggest prior calcite precipitation, which is considered a long-term (years) water-rock interaction process as a consequence of the prolonged dryness situation.
This is a contribution to projects CGL2004-01866/BTE and CGL2007-60618-BTE, and research grants PR-2007-0111 and PR-2007-0197 (MEC Spain). Goldschmidt Conference Abstracts 2008 A963
Isotope fingerprinting of the first Paleodrainage reconstruction using Tertiary land mammal from Pb isotopes in K-feldspar sand Scandinavia grains: Examples from the 1 2 THOMAS TÜTKEN * AND THOMAS MÖRS NW European Triassic 1 1 1 1Steinmann Institut für Geologie, Mineralogie und S. TYRRELL *, P.D.W. HAUGHTON , J.S. DALY , 2 2 3 Paläontologie, University Bonn, Poppelsdorfer Schloss, K. SOUDERS , P. SYLVESTER AND A. KRONZ 53115 Bonn, Germany 1UCD School of Geological Sciences, UCD, Belfield, Dublin (*correspondence: [email protected]) 4, Ireland (*correspondence: [email protected]) 2Swedish Museum of Natural History, Box 50007, 104 05 2Department of Earth Sciences, Memorial Univ., St. John's, Stockholm, Sweden ([email protected]) NL A1C 5S7, P.O. Box 4200, Canada
3Geochemisches Institut, Universität Göttingen, A Miocene gomphothere tooth (Fig 1a), embedded in a Goldschmidtstr. 1, 37077 Göttingen, Germany reworked sandstone pebble (Fig. 1b), was found in an oser deposit southwest of Stockholm, Sweden. This molar is the The Pb isotopic composition of detrital K-feldspar is a first find of a Tertiary land mammal in Scandinavia. powerful means of constraining sandstone provenance. It has been shown that K-feldspar retains the Pb signature of its source despite erosion, transport and diagenesis. The continental crust exhibits broad (100s km) variations in Pb isotopes and thus potential sourcelands can be characterised on a scale appropriate to that of major drainage systems. Electron microprobe analysis and imaging (BSE and CL) of detrital grains means that heterogeneities (e.g. inclusions, alteration) can be avoided during in situ LA-MC-ICPMS analysis. Furthermore, as K-feldspar is a common and likely first cycle component of sandstones, the technique provides a means of tracking grains directly back to their source. In this way, the method can constrain palaeodrainage pathways and Isotope compositions of tooth enamel are related to that of lengthscales, with consequent application to palaeogeographic the ingested food or water during its mineralization and reconstructions. depend on the climate, vegetation, and bedrock geology. To The K-feldspar Pb isotope technique is being used to determine where in Sweden the gomphothere lived and investigate regional sediment dispersal in the northern fossilized, the isotope composition (C, O, Sr, Nd) of the tooth Pangaean supercontinental interior, specifically focussed on and the embedding sediment were analyzed. Isotopic sand-rich Triassic successions from NW European signatures of the tooth will be compared to those of Miocene sedimentary basins. These sandstones, which locally form gomphothere teeth from central Europe as well as to bones of important hydrocarbon reservoirs, represent large-scale and extant moose from different areas of Sweden with different ephemeral fluvial systems. Large-scale northward-flowing bedrocks. rivers supplied detritus into the Paris and North Sea basins and The enamel of the Swedish gomphothere tooth has a onshore UK from the Variscan Uplands in central Europe. By 87 86 Sr/ Sr ratio of 0.71592 typical for old crustal rocks and contrast, new Pb data from the NE Atlantic peripheral basins more radiogenic than those of Miocene gomphothere teeth indicate that the Variscan Uplands exerted no discernable from continental Europe (0.70650 to 0.71063, n = 17). Intra- influence on the developing drainage system in these areas. 18 tooth enamel δ OCO3 values display two seasonal cycles Previously unrecognised Triassic drainage pathways have 13 (mean 22.4±0.7‰ VSMOW, n = 12). Enamel δ C values been identified, and the important role played by uplifted suggest a Lower Miocene age of the tooth. U/Pb isotope Archean and Proterozoic basement blocks in controlling analysis of detrital zircons from the embedding sediment is in Triassic drainage evolution is highlighted. progress to determine the age of the source rocks. This multi-isotope provenance approach proves the existence of Tertiary terrestrial sediments with mammal fauna in Scandinavia, eroded during Pleistocene glaciations.