Rare earth element geochemistry of hydrothermal deposits from the active TAG Mound, 26°N Mid-Atlantic Ridge
Rare earth element geochemistry of hydrothermal deposits from the active TAG Mound, 26°N Mid-Atlantic Ridge
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DOI：
10.1016/0016-7037(95)00224-n
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发表时间：
1995-09
影响因子：
5
通讯作者：
R. Mills;H. Elderfield
中科院分区：
文献类型：
--
作者：
R. Mills;H. Elderfield
对活动TAG热液丘不同相态的稀土元素地球化学进行了研究，并与矿物学和流体化学进行了对比。丘状沉积物包括黑色和白色烟囱、块状硬石膏/硫化物混合物、氧化物和赭石。所有阶段，除了黑烟烟囱硬石膏，表现出积极的Eu异常时，球粒陨石稀土元素值归一化。稀土元素取代成硫化物和硫酸盐相出现强烈的影响，除了Eu的所有稀土元素的结晶控制。TAG丘内的硬石膏沉淀是丘循环过程中去除REE的主要机制，推断从白色烟囱排出的每kg流体中沉淀0.15-0.35 g硬石膏。氧化物从土堆分为三个不同的类别与不同的稀土元素模式：氧化物轮辋硫化物，氯铜矿轴承氧化物，富硅铁氧化物和赭石。氧化物边缘相含有硫化物和海水衍生的稀土元素，而含氯铜矿的氧化物和赭石材料没有表现出海水的签名，这表明沉淀，或蚀变，改性热液流体。
The rare earth element (REE) geochemistry of various phases from the active TAG hydrothermal mound has been examined and related to their mineralogy and fluid chemistry. The mound deposits range from black and white smoker chimneys, massive anhydrite/sulphide mixtures, oxides, and ochres. All phases, except black smoker chimney anhydrite, demonstrate a positive Eu anomaly when normalised to chondrite REE values. REE substitution into sulphide and sulphate phases appears to be strongly influenced by crystallographic control for all REE other than Eu. Precipitation of anhydrite within the TAG mound is the major mechanism for removal of REE during mound circulation and 0.15-0.35 g anhydrite is inferred to precipitate from every kg of fluid venting from the white smoker chimneys. Oxides from the mound fall into three different categories with distinct REE patterns: oxide rims on sulphides, atacamite-bearing oxides, and silica-rich Fe-oxides and ochres. The oxide rim phases contain sulphide and seawater derived REEs whereas the atacamite-bearing oxides and the ochreous material exhibit no seawater signature which suggests precipitation from, or alteration by, a modified hydrothermal fluid.