Major and trace element composition of surface sediments from the Southwest Indian Ridge：evidence for the incorporation of a hydrothermal component

• Published in: Acta oceanologica Sinica 2016-02, Vol.35 (2), p.101-108
• Main Authors: Li, Zhenggang, Chu, Fengyou, Jin, Lu, Li, Xiaohu, Dong, Yanhui, Chen, Ling, Zhu, Jihao
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Atmospheric particulates; Calcium oxide; Carbonates; Climatology; Continental crust; Deep sea; Deep water; Detritus; Earth and Environmental Science; Earth Sciences; Ecology; Engineering Fluid Dynamics; Environmental Chemistry; Eolian dust; Fault lines; Field strength; Fluids; Hydrothermal activity; Leaching; Low temperature; Manganese; Marine; Marine & Freshwater Sciences; Mid-ocean ridges; Mineralization; Oceanography; Oozes; Precipitates; Rare earth elements; Ridges; Sediment; Sediment samplers; Sediment samples; Sediments; Silica; Silicon dioxide; Spreading centres; Trace elements; Tracers; Zirconium; 海洋学; 海洋组织; 海洋观测; 海洋调查
• ISSN: 0253-505X; 1869-1099
• DOI: 10.1007/s13131-015-0678-8

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.