富钴结壳关键元素赋存状态与富集机理

    Cobalt-rich crust obtains high contents of key elements from seawater: element absorption and distribution

    • 摘要: 富钴结壳是大洋低温海水中的溶解元素在海山边坡沉淀形成的壳状铁锰矿产,广泛分布于全球海山、海底高原斜坡之上,储量巨大。铁锰结壳高度富集Co、Ni、Pt、REE、Te等元素,达到海水丰度的105~1010倍,是未来新能源、高新技术元素的重要来源,具有极大的潜在经济价值。前人通过淋滤实验、吸附实验、现代海洋观测方法、海水化学分析、高分辨率精细矿物学研究等方法对富钴结壳中元素的赋存状态和富集机理进行了广泛而深入的研究。研究结果表明,富钴结壳主要由含铁水羟锰矿和铁氢氧化物组成,在海山附近的海洋化学过程中,含铁水羟锰矿和铁氢氧化物胶体分别优先吸附Co、Ni、Pt、REE和Cu、Pb、Te、REE等元素,表面氧化/置换作用造成了含铁水羟锰矿中Co、Pt、Ni、Ce及铁氢氧化物中Te、Ce的持续积累。富钴结壳极其缓慢的生长速率(1~10 mm/Ma)、超高孔隙度(60%)、极大的体表面积(300 m2/g)都促进了结壳中关键元素的超常富集。对富钴结壳关键元素富集机理的理解是富钴结壳古海洋反演研究的基础,海域富钴结壳地球化学差异的控制因素需要进一步研究,这些关键科学问题的理解有助于富钴结壳资源的勘探工作。

       

      Abstract: Cobalt-rich crust is formed from precipitation of dissolved elements in low temperature seawater on the slope of seamounts.It is widely distributed on the slope of seamounts and undersea plateau in the oceans, with huge reserves.Ferromanganese crusts have high contents of Co, Ni, Pt, REE, Te, which reach 105-1010 times of the seawater.They are important sources of new energy and high-tech elements in the future and have great potential economic value.The former researchers have focused on the association and enrichment mechanism of the elements in the cobalt-rich crust, with the help of step leaching, absorption experiment, modern ocean observation, water chemistry, high resolution of fine mineralogy.It reveals that cobalt-rich crusts are mainly composed of ferruginous vernadite and amorphous Iron hydroxide.In the process of marine chemistry near seamounts, ferrugvnous vernadite colloid and iron hydroxide colloid preferentially adsorb Co, Ni, Pt, REE and Cu, Pb, Te, REE, respectively.Surface oxidation/lattice replacement result in the continuous accumulation of Co, Pt, Ni, Ce in ferrugvnous Vernadite and Te, Ce in iron hydroxide.The extremely slow growth rate (1~10 mm/Ma), ultra-high porosity (60%) and large surface area (300 m2/g) of cobalt-rich crusts all promote the high enrichment of key elements in the crusts.The trace elements enrichment mechanism of the cobalt-rich crust is key to paleo-oceanography inversion.On the other way, the factors controlling the geochemical differences of cobalt-rich crust in the ocean need further study, understanding which will contribute to the exploration of cobalt-rich crust resources.

       

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