Particle geochemistry in the Rainbow hydrothermal plume, Mid-Atlantic Ridge
Particle geochemistry in the Rainbow hydrothermal plume, Mid-Atlantic Ridge
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DOI：
10.1016/s0016-7037(03)00498-8
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发表时间：
2004-02-01
影响因子：
5
通讯作者：
German, CR
中科院分区：
文献类型：
--
作者：
Edmonds, HN;German, CR
我们报道了18个大体积(500-1500 L)的颗粒物质现场过滤样品的分析，这些样品来自大西洋中部海脊上最大的热液羽流，位于北纬36°14‘的超镁铁质赋存的彩虹热液田之上，测得颗粒铁浓度为614 nm。颗粒状氢氧化铁的高浓度源于喷口流体极高的铁浓度(接近24 mm)和Fe/HZS比值(接近24)，并由于羽流物质与周围沿轴向流动的平流而持续到距离喷口至少10公里的地方。九对泵中的两对似乎拦截了热液羽流的浮力部分或非常年轻的部分。这些样品的特征是异常高的镁、铀和亲磷元素，而低浓度的锰、钙、钒、Y和稀土元素(REE)(与中性漂浮的烟柱样品相比)。在中性浮力羽流中，元素分布与以前观察到的行为基本一致：优先去除亲胆碱元素，氧阴离子(P、V和U)的保守行为，以及Y和REE的持续清除。鉴于彩虹和其他研究地点在流体化学方面的潜在差异，这种一致性尤其重要。亲胆素优先按Cd>；Zn>；Co>；Cu的顺序从羽流中去除。中性浮力羽流的磷/铁和钒/铁比率与周围海水中溶解的磷酸盐浓度的全球趋势是一致的。然而，将浮力和中性浮力羽流比率与彩虹羽流下面的热液沉积物的数据进行比较(Cave等人，2002年)表明，虽然P/Fe比率确实是恒定的，但V/Fe比率从早期羽流颗粒到沉积物逐渐增加。稀土在浮力和中性浮力羽流中的分布似乎与水柱扩散过程中的连续清除过程最为一致。版权所有(C)2004爱思唯尔有限公司
We report the analysis of 18 large volume (500-1500 L) in situ filtered samples of particulate material from the largest hydrothermal plume on the Mid-Atlantic Ridge, overlying the ultramafic-hosted Rainbow hydrothermal field at 36degrees 14'N. Measured particulate iron concentrations reach 614 nM. High concentrations of particulate Fe oxyhydroxides result from the extremely high Fe concentration (similar to24 mM) and Fe/HZS ratio (similar to24) of the vent fluids, and persist to at least 10 km away from the vent site due to the advection of plume material with the ambient along-axis flow. Two of the nine pairs of pump deployments appear to have intercepted the buoyant or otherwise very young portion of the hydrothermal plume. These samples are characterized by anomalously (compared to neutrally buoyant plume samples) high concentrations of Mg, U, and chalcophile elements, and low concentrations of Mn, Ca, V, Y, and the rare earth elements (REE). Within the neutrally buoyant plume, elemental distributions are largely consistent with previously observed behaviors: preferential removal of chalcophile elements, conservative behavior of oxyanions (P, V, and U), and continuous scavenging of Y and the REE. This consistency is particularly significant in light of the underlying differences in fluid chemistry between Rainbow and other studied sites. Chalcophile elements are preferentially removed from the plume in the order Cd>Zn>Co>Cu. Phosphorus/iron and vanadium/iron ratios for the neutrally buoyant plume are consistent with global trends with respect to the concentration of dissolved phosphate in ambient seawater. Comparison of buoyant and neutrally buoyant plume ratios with data from hydrothermal sediments underlying the Rainbow plume (Cave et al., 2002) indicates, however, that while P/Fe ratios are indeed constant V/Fe ratios increase progressively from early stage plume particles to sediments. REE distributions in the buoyant and neutrally buoyant plume appear most consistent with a continuous scavenging process during dispersion through the water column. Copyright (C) 2004 Elsevier Ltd