Experimental investigation of pyrite formation under conditions approximating those found in anoxic marine sediments /
Experiments were performed utilizing the silica gel technique
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742745201&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Experiments were performed utilizing the silica gel technique to synthesize pyrite crystals in four different chemical systems, at room temperature (- 23 IC), for periods of up to 24 months. These systems were: FeS(I-x)(mackinawite) + So(s) + S2-(aq), Fe3S4(greigite) + S2-(aq), FeOOH(Fe (hydr)oxide) + S2-(aq) and Fe2+(aq) + S42-(aq). Iron (hydr)oxides include goethite, ferrihydrite, lepidocrocite, hematite, akaganite and magnetite. The effect of organic matter on sulfidation of goethite was also investigated. Solid reactants were dispersed in silica gel that was overlain by sodium sulfide solutions. These solutions covered a wide range of pH and yS2- values. Reaction products were sampled periodically and analyzed by XRD and SEM/EDS. Six different iron (hydr)oxides show similar sulfidation behavior. Their reaction rates and products are dependent on pH and ES2- concentration. The rate of pyrite formation strongly depends on the nature of solid reactant and solution chemistry (pH and .ZS2- concentration). Pyritization of mackinawite with elemental sulfur is a very slow process, whereas pyrite formation is substantially faster in the presence of greigite, and the transformation of greigite to pyrite is accelerated with increasing yS2- and decreasing pH. Organic matter enhances the sulfidation rate of iron (hydr)oxides but significantly inhibits pyrite formation. Experimental results from this study suggest that the pyritization of metastable iron sulfide minerals follows a dissolution-precipitation pathway, and mass transport probably plays an important role in sedimentary pyrite formation. SEM observations indicate that the morphology of pyrite crystals formed at room temperature is primarily controlled by the degree of supersaturation in the solution from which pyrite is precipitated. At increased supersaturations, pyrite morphology changes from cube to octahedron then to spherulite. 'The influence of other parameters, such as pH, relative abundance of Fe2+ and dissolved zero-valance sulfur, were found not to be of major significance. |
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| Item Description: | Vita. "Major Subject: Oceanography". |
| Physical Description: | xi, 105 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |