Formation of Natural Silicate Hydrates by the Interaction of Alkaline Seepage and Sediments Derived from Serpentinized Ultramafic Rocks at Narra, Palawan, the Philippines
In radioactive waste disposal facilities, low-permeability engineered barrier materials are important for inhibiting radionuclide migration. However, dissolution–precipitation reactions under alkaline conditions change the permeability of engineered barriers. To understand long-term dissolution–prec...
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MDPI AG
2020-08-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/10/8/719 |
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| author | Misato Shimbashi Shingo Yokoyama Yasutaka Watanabe Tsutomu Sato Tsubasa Otake Ryosuke Kikuchi Minoru Yamakawa Naoki Fujii |
| author_facet | Misato Shimbashi Shingo Yokoyama Yasutaka Watanabe Tsutomu Sato Tsubasa Otake Ryosuke Kikuchi Minoru Yamakawa Naoki Fujii |
| author_sort | Misato Shimbashi |
| collection | DOAJ |
| description | In radioactive waste disposal facilities, low-permeability engineered barrier materials are important for inhibiting radionuclide migration. However, dissolution–precipitation reactions under alkaline conditions change the permeability of engineered barriers. To understand long-term dissolution–precipitation reactions under alkaline conditions in chemically complex systems, trenches and drill holes were excavated at Narra in Palawan, where alkaline fluids (pH > 11) have been naturally produced, seeping into clastic sediments derived from serpentinized ultramafic rocks and gabbro of Palawan ophiolite. Interaction between the alkaline seepage and clastic sediments, which have been deposited since 15,000 radiocarbon years before present (<sup>14</sup>C yr BP), led to dissolution of minerals and the precipitation of Si-bearing phases which were divided into two main categories: Fe-Mg-Si infillings and Ca-Si infillings. The former category was composed of iron-magnesium-silicate-hydrate (F-M-S-H) and a nontronite-like mineral and was widely recognized in the clastic sediments. The nontronite-like mineral likely formed by interaction between silicates and alkaline seepage mixed with infiltrated seawater, whereas F-M-S-H formed by the reaction of silicates with alkaline seepage in the absence of seawater infiltration. Ca-Si infillings included 14 Å tobermorite and were precipitated from alkaline seepage combined with the Ca and Si supplied by the dissolution of calcite and silicates in the clastic sediments. |
| first_indexed | 2024-03-10T17:18:22Z |
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| language | English |
| last_indexed | 2024-03-10T17:18:22Z |
| publishDate | 2020-08-01 |
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| record_format | Article |
| series | Minerals |
| spelling | doaj.art-8418e9ab80be417a80123d00b64cb77a2023-11-20T10:25:54ZengMDPI AGMinerals2075-163X2020-08-0110871910.3390/min10080719Formation of Natural Silicate Hydrates by the Interaction of Alkaline Seepage and Sediments Derived from Serpentinized Ultramafic Rocks at Narra, Palawan, the PhilippinesMisato Shimbashi0Shingo Yokoyama1Yasutaka Watanabe2Tsutomu Sato3Tsubasa Otake4Ryosuke Kikuchi5Minoru Yamakawa6Naoki Fujii7Central Research Institute of Electric Power Industry, Chiba 270-1194, JapanCentral Research Institute of Electric Power Industry, Chiba 270-1194, JapanCentral Research Institute of Electric Power Industry, Chiba 270-1194, JapanDivision of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Hokkaido 060-8628, JapanDivision of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Hokkaido 060-8628, JapanDivision of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Hokkaido 060-8628, JapanRadioactive Waste Management Funding and Research Center, Tokyo 104-0052, JapanRadioactive Waste Management Funding and Research Center, Tokyo 104-0052, JapanIn radioactive waste disposal facilities, low-permeability engineered barrier materials are important for inhibiting radionuclide migration. However, dissolution–precipitation reactions under alkaline conditions change the permeability of engineered barriers. To understand long-term dissolution–precipitation reactions under alkaline conditions in chemically complex systems, trenches and drill holes were excavated at Narra in Palawan, where alkaline fluids (pH > 11) have been naturally produced, seeping into clastic sediments derived from serpentinized ultramafic rocks and gabbro of Palawan ophiolite. Interaction between the alkaline seepage and clastic sediments, which have been deposited since 15,000 radiocarbon years before present (<sup>14</sup>C yr BP), led to dissolution of minerals and the precipitation of Si-bearing phases which were divided into two main categories: Fe-Mg-Si infillings and Ca-Si infillings. The former category was composed of iron-magnesium-silicate-hydrate (F-M-S-H) and a nontronite-like mineral and was widely recognized in the clastic sediments. The nontronite-like mineral likely formed by interaction between silicates and alkaline seepage mixed with infiltrated seawater, whereas F-M-S-H formed by the reaction of silicates with alkaline seepage in the absence of seawater infiltration. Ca-Si infillings included 14 Å tobermorite and were precipitated from alkaline seepage combined with the Ca and Si supplied by the dissolution of calcite and silicates in the clastic sediments.https://www.mdpi.com/2075-163X/10/8/719alkaline seepageophiolitesilicate hydratesmectitetobermorite |
| spellingShingle | Misato Shimbashi Shingo Yokoyama Yasutaka Watanabe Tsutomu Sato Tsubasa Otake Ryosuke Kikuchi Minoru Yamakawa Naoki Fujii Formation of Natural Silicate Hydrates by the Interaction of Alkaline Seepage and Sediments Derived from Serpentinized Ultramafic Rocks at Narra, Palawan, the Philippines Minerals alkaline seepage ophiolite silicate hydrate smectite tobermorite |
| title | Formation of Natural Silicate Hydrates by the Interaction of Alkaline Seepage and Sediments Derived from Serpentinized Ultramafic Rocks at Narra, Palawan, the Philippines |
| title_full | Formation of Natural Silicate Hydrates by the Interaction of Alkaline Seepage and Sediments Derived from Serpentinized Ultramafic Rocks at Narra, Palawan, the Philippines |
| title_fullStr | Formation of Natural Silicate Hydrates by the Interaction of Alkaline Seepage and Sediments Derived from Serpentinized Ultramafic Rocks at Narra, Palawan, the Philippines |
| title_full_unstemmed | Formation of Natural Silicate Hydrates by the Interaction of Alkaline Seepage and Sediments Derived from Serpentinized Ultramafic Rocks at Narra, Palawan, the Philippines |
| title_short | Formation of Natural Silicate Hydrates by the Interaction of Alkaline Seepage and Sediments Derived from Serpentinized Ultramafic Rocks at Narra, Palawan, the Philippines |
| title_sort | formation of natural silicate hydrates by the interaction of alkaline seepage and sediments derived from serpentinized ultramafic rocks at narra palawan the philippines |
| topic | alkaline seepage ophiolite silicate hydrate smectite tobermorite |
| url | https://www.mdpi.com/2075-163X/10/8/719 |
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