Carbonatation of diatomites and diagenetic limestones/dolomites in freshwater and marine environments (Miocene of Tresjuncos, Cuenca and Níjar, Almería). An example of CO2 sequestration in Nature
[EN] Carbonate (calcite and dolomite) pseudomorphs after diatoms were identified from marine (Messinian, Níjar section) and freshwater (Turolian, Tresjuncos section) diatomites. The mineralogical and petrological study has allowed to know the replacement of opal-A by calcite or dolomite, and the con...
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2020 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/233369 |
| Acceso en línea: | http://hdl.handle.net/10261/233369 |
| Access Level: | acceso abierto |
| Palabra clave: | Carbonatation Diatomites Opal-A Pseudomorphism Diagenesis |
| Sumario: | [EN] Carbonate (calcite and dolomite) pseudomorphs after diatoms were identified from marine (Messinian, Níjar section) and freshwater (Turolian, Tresjuncos section) diatomites. The mineralogical and petrological study has allowed to know the replacement of opal-A by calcite or dolomite, and the consequent formation of diagenetic limestones/dolostones, deducing the factors that favor this replacement in both environments. The data obtained are relevant to the research about the use of diatomites for the capture and storage of carbon dioxide through carbonation. A pseudomorphic carbonatation process of the frustules occurred by a direct replacement of the opal-A and a cementation of the microporosity. Opal-A was replaced by calcite or dolomite via a coupled dissolution-precipitation process. The organization of the opal A microspheres inside the frustules could determine the organization of multi-ion complexes / nanoparticles of amorphous carbonates that would later recrystallize to calcite or dolomite crystals. The carbonation of the lacustrine diatomites was favored by the great amount of biota (amphibians, crustaceans, insects, plants…etc.) included in them. In this environment, the sulphate-reduction processes during the degradation of the organic matter generated CO2, which along with pH and salinity changes, facilitated the replacements. It is possible that the carbonatation of the frustules was coeval to the calcite or dolomite precipitation during the fossilization of the biota, and therefore, early diagenetic in origin. The nodules and opaline lenticular beds formation triggered the carbonation process of the marine diatomites because CO2 and Ca are released from the dissolution of biocalcarenites/biocalcitutites included in the diatomites. Small pH variations around 9, and the presence of sulfates, would facilitate the replacement of the valves, during the burial diagenesis. |
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