Mineral Composition and Environmental Importance of Fe–Mn Nodules in Soils in Karst Areas of Guangxi, China

Wenbing Ji, Yuanyuan Lu, Caiyi Zhao, Xiaoyu Zhang, Heng Wang, Zhewei Hu, Tao Yu, Yubo Wen, Rongrong Ying () and Zhongfang Yang ()
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Wenbing Ji: Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing 210042, China
Yuanyuan Lu: Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing 210042, China
Caiyi Zhao: Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing 210042, China
Xiaoyu Zhang: Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing 210042, China
Heng Wang: Hefei East New Center Construction Management Office, Hefei 230071, China
Zhewei Hu: Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing 210042, China
Tao Yu: School of Science, China University of Geosciences, Beijing 100083, China
Yubo Wen: School of Geographical Science, Nantong University, Nantong 226000, China
Rongrong Ying: Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing 210042, China
Zhongfang Yang: School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China

Sustainability, 2022, vol. 14, issue 19, 1-10

Abstract: The mineral composition of Fe–Mn nodules (FMNs) is closely related to the environment in which FMNs are formed. The formation mechanism of FMNs has consistently been one of the major topics in related research. In this study, the mineral composition of FMNs in soils derived from carbonate rocks in typical karst areas with high geochemical background in Guangxi, Southwest China, was investigated. The results showed that Fe 2 O 3 (30.06%), SiO 2 (19.72%), Al 2 O 3 (17.93%), TiO 2 (0.96%), P 2 O 5 (0.78%), and MnO 2 (0.64%) were the main elemental composition, while four alkaline oxides K 2 O, Na 2 O, CaO, and MgO were less than 0.5% in soil FMNs. In addition, 10 mineral types were identified in soil FMNs in the study area, namely quartz, goethite, clinochlore, illite, kaolinite, boehmite, albite, microcline, lithiophorite, and hematite. There were no obvious differences in the mineral composition of soil FMNs in the study area compared with those observed in non-karst areas worldwide. The formation process of FMNs can be determined based on the surrounding environment that affects the soil mineral composition. The results suggested a relatively complex formation mechanism of soil FMNs. Moreover, both primary and secondary minerals were found in soil FMNs. However, some minerals can exist stably under normal redox conditions, while the other part of minerals can be easily weathered and dissolved, indicating a relatively high formation rate of soil FMNs and a relatively stable internal environment.

Keywords: Fe–Mn nodules; karst area; mineral composition; formation mechanism; Guangxi (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2022
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