| Abstract: | The S isotope composition of pyrite in Cretaceous shales from the Western Interior of North America is related to organic C abundance, kerogen type and Fe availability. Both calcareous and noncalcareous rocks show a correlation between S and C, but noncalcareous rocks are relatively enriched in S with a higher S C ratio. This higher ratio probably shows that pyrite formation was Fe limited in the calcareous rocks. Organic-carbon-rich noncalcareous shales accumulated slowly beneath anoxic bottom waters. The anoxic bottom waters allowed hydrogen-rich organic matter to be preserved. Such shales have a narrow range of 34S-depleted sulfide and have Fe S ratios like stoichiometric pyrite, suggesting that pyrite formation in organic-rich shales was also limited by Fe availability. Conversely, organic-poor shales commonly accumulated at comparatively high rates, contain hydrogen-poor and refractory organic matter, and have a wide range of pyrite-S isotopic compositions. These organic-poor shales contain post-sulfidic authigenic minerals such as siderite and have excess reactive Fe rather than pyrite stoichiometry. Evidently Fe played a large role in early diagenesis and determined the course of post-sulfidic diagenesis. Fe availability was, however, mainly controlled by provenance, by the rates of sediment accumulation, and by the oxygen content of the depositional environment. ?? 1987. |
| Genre: | Article |
| ProdID: | 70014108 |
| Citation Author: | Gautier, D. L. |
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| Citation End Page: | 303 |
| Citation Issue: | 3-4 |
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| Citation Language: | English |
| Citation Larger Work Title: | Chemical Geology: Isotope Geoscience Section |
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| Citation Number Of Pages: | 11 |
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| Citation Search Results Text: | Isotopic composition of pyrite: Relationship to organic matter type and iron availability in some North American cretaceous shales; 1987; Article; Journal; Chemical Geology: Isotope Geoscience Section; Gautier, D. L. |
| Citation Start Page: | 293 |
| Citation Volume: | 65 |
| Citation Year: | 1987 |
| Type: | citation/reference |
| Text: | Isotopic composition of pyrite: Relationship to organic matter type and iron availability in some North American cretaceous shales; 1987; Article; Journal; Chemical Geology: Isotope Geoscience Section; Gautier, D. L. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Thu, 1 Jan 1987 00:00 -0600 |
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