Element mobilization and redistribution under extreme tropical weathering of basalts from the Hainan Island, South China | |
Ke Jiang; Hua-Wen Qi; Rui-Zhong Hu | |
2018 | |
发表期刊 | Journal of Asian Earth Sciences |
卷号 | 158页码:80-102 |
摘要 | Chemical weathering of rocks has substantial influence on the global geochemical cycle. In this paper, the geochemical profile of a well-developed basalt weathering profile (> 15 m thick, including soil, saprolite, semiweathered rock and fresh basalt) on the Island of Hainan (South China) was presented. The soil and saprolite samples from this profile are characterized by high Al2O3 and Fe2O3 concentrations (up to 32.3% and 28.5%, respectively). The mineral assemblage is dominated by kaolinite, Fe-oxides/-hydroxides and gibbsite (or boehmite), indicating extensive desilicate and ferrallitic weathering. The acidic and organic-rich environment in the soil horizon may have promoted elemental remobilization and leaching. The strongest SiO2 depletion and Al2O3 enrichment at about 2.4 m deep indicate that the main kaolinite hydrolysis and gibbsite formation occurred near the soil-saprolite interface. The mild Sr reconcentration at about 3.9 m and 7.1 m deep may be attributed to secondary carbonate precipitation. Mn-oxides/-hydroxides precipitated at 6.1 m deep, accompanied by the strongest enrichment of Ba and Co. Uranium is mildly enriched in the middle part (about 7.1 m and 9.1 m deep) of the weathering profile, and the enrichment may have been caused by the decomposition of uranyl carbonates or the accumulation of zircon. Immobile element (i.e., Zr, Hf, Nb, Ta, Th and Ti) distributions at different depths are mainly controlled by secondary Fe-oxides/-hydroxides, and follow the stability sequence of Nb ≈ Ta ≈ Th > Zr ≈ Hf > Ti. The limited thickness (∼15 cm) of the semi-weathered basalt horizon at the rock-regolith interface (15.28 m deep) suggests that plagioclase and pyroxene are readily altered to kaolinite, smectite and Fe-oxides under tropical climate. The marked enrichment of transitional metals (such as Cu, Zn, Ni, and Sc) along the rock-regolith interface may have associated mainly with increasing pH values, as well as the dissolution of primary apatite and formation of secondary phosphates. Our findings highlight the importance of secondary phosphates in the redistribution of transition metals, and in the possible Mg, Cu, and Ni isotopic fractionation under extreme weathering of basalt in tropic climate. |
关键词 | Chemical Weathering basalt secondary Minerals hainan Island (South China) |
收录类别 | SCI |
语种 | 英语 |
文献类型 | 期刊论文 |
条目标识符 | http://ir.gyig.ac.cn/handle/42920512-1/8704 |
专题 | 矿床地球化学国家重点实验室 |
通讯作者 | Hua-Wen Qi |
作者单位 | 1.State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China 2.University of Chinese Academy of Sciences, Beijing 100049, China |
推荐引用方式 GB/T 7714 | Ke Jiang,Hua-Wen Qi,Rui-Zhong Hu. Element mobilization and redistribution under extreme tropical weathering of basalts from the Hainan Island, South China[J]. Journal of Asian Earth Sciences,2018,158:80-102. |
APA | Ke Jiang,Hua-Wen Qi,&Rui-Zhong Hu.(2018).Element mobilization and redistribution under extreme tropical weathering of basalts from the Hainan Island, South China.Journal of Asian Earth Sciences,158,80-102. |
MLA | Ke Jiang,et al."Element mobilization and redistribution under extreme tropical weathering of basalts from the Hainan Island, South China".Journal of Asian Earth Sciences 158(2018):80-102. |
条目包含的文件 | 下载所有文件 | |||||
文件名称/大小 | 文献类型 | 版本类型 | 开放类型 | 使用许可 | ||
Element mobilization(3896KB) | 期刊论文 | 作者接受稿 | 开放获取 | CC BY-NC-SA | 浏览 下载 |
除非特别说明,本系统中所有内容都受版权保护,并保留所有权利。
修改评论