| 西南印度洋中脊表层沉积物中存在热液组分的地球化学证据 |
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| 引用本文： | 李正刚,初凤友,金路,李小虎,董彦辉,陈灵,朱继浩.西南印度洋中脊表层沉积物中存在热液组分的地球化学证据[J].海洋学报(英文版),2016,35(2):101-108. |
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| 作者姓名： | 李正刚 初凤友 金路 李小虎 董彦辉 陈灵 朱继浩 |
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| 作者单位： | 国家海洋局第二海洋研究所, 杭州 310012;浙江大学地球科学系 杭州 310027,国家海洋局第二海洋研究所, 杭州 310012;浙江大学地球科学系 杭州 310027,国家海洋局第二海洋研究所, 杭州 310012;浙江大学地球科学系 杭州 310027,国家海洋局第二海洋研究所, 杭州 310012,国家海洋局第二海洋研究所, 杭州 310012,国家海洋局第二海洋研究所, 杭州 310012;浙江大学地球科学系 杭州 310027,国家海洋局第二海洋研究所, 杭州 310012 |
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| 摘 要： | Hydrothermal materials in deep-sea sediments provide a robust tracer to the localized hydrothermal activity at mid-ocean ridges. Major, trace and rare earth element(REE) data for surface sediments collected from the ultraslow spreading Southwest Indian Ridge are presented to examine the existence of hydrothermal component.Biogenic carbonate oozes dominate all the sediment samples, with CaO content varying from 85.5% to 89.9% on a volatile-free basis. The leaching residue of bulk sediments by ~5% HCl is compositionally comparable to the Upper Continental Crust(UCC) in SiO_2, Al_2O_3, CaO, MgO, alkali elements(Rb, Cs) and high field strength elements(Nb, Ta, Zr, Hf, Ti). These detritus-hosted elements are inferred to be prominently derived from the Australian continent by means of eolian dust, while the contribution of local volcaniclastics is insignificant. In addition, the residual fraction shows a clear enrichment in Fe, Mn, and Ba compared with the UCC. Combining the positive Eu anomaly of residual fraction which is opposed to the UCC but the characteristic of hydrothermal fluids and associated precipitates occurred at mid-ocean ridges, the incorporation of localized hydrothermal component can be constrained. REE mixing calculations indicate that more than half REE within the residual fraction(~55%–60%) are derived from a hydrothermal component, which is inferred to be resulted from a diffuse fluid mineralization. The low-temperature diffuse flow may be widely distributed along the slow-ultraslow spreading ridges where crustal faults and fissures abound, and probably have a great mineralization potential.
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| 关 键 词： | 深海沉积物 热液组分 低温弥散流 风尘砂 西南印度洋中脊 |
| 收稿时间： | 2014/12/5 0:00:00 |
| 修稿时间： | 2015/3/31 0:00:00 |
Major and trace element composition of surface sediments from the Southwest Indian Ridge: evidence for the incorporation of a hydrothermal component |
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| LI Zhenggang,CHU Fengyou,JIN Lu,LI Xiaohu,DONG Yanhui,CHEN Ling and ZHU Jihao.Major and trace element composition of surface sediments from the Southwest Indian Ridge: evidence for the incorporation of a hydrothermal component[J].Acta Oceanologica Sinica,2016,35(2):101-108. |
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| Authors: | LI Zhenggang CHU Fengyou JIN Lu LI Xiaohu DONG Yanhui CHEN Ling and ZHU Jihao |
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| Institution: | 1.Key Laboratory of Submarine Geoscience, Second Institute of Oceanography, State Oceanic Administration (SOA), Hangzhou 310012, China;Department of Earth Sciences, Zhejiang University, Hangzhou 310027, China2.Key Laboratory of Submarine Geoscience, Second Institute of Oceanography, State Oceanic Administration (SOA), Hangzhou 310012, China |
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| Abstract: | Hydrothermal materials in deep-sea sediments provide a robust tracer to the localized hydrothermal activity at mid-ocean ridges. Major, trace and rare earth element (REE) data for surface sediments collected from the ultraslow spreading Southwest Indian Ridge are presented to examine the existence of hydrothermal component. Biogenic carbonate oozes dominate all the sediment samples, with CaO content varying from 85.5% to 89.9% on a volatile-free basis. The leaching residue of bulk sediments by ~5% HCl is compositionally comparable to the Upper Continental Crust (UCC) in SiO2, Al2O3, CaO, MgO, alkali elements (Rb, Cs) and high field strength elements (Nb, Ta, Zr, Hf, Ti). These detritus-hosted elements are inferred to be prominently derived from the Australian continent by means of eolian dust, while the contribution of local volcaniclastics is insignificant. In addition, the residual fraction shows a clear enrichment in Fe, Mn, and Ba compared with the UCC. Combining the positive Eu anomaly of residual fraction which is opposed to the UCC but the characteristic of hydrothermal fluids and associated precipitates occurred at mid-ocean ridges, the incorporation of localized hydrothermal component can be constrained. REE mixing calculations indicate that more than half REE within the residual fraction (~55%-60%) are derived from a hydrothermal component, which is inferred to be resulted from a diffuse fluid mineralization. The low-temperature diffuse flow may be widely distributed along the slow-ultraslow spreading ridges where crustal faults and fissures abound, and probably have a great mineralization potential. |
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| Keywords: | deep-sea sediments hydrothermal component diffuse fluid eolian dust Southwest Indian Ridge |
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