Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica
Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica
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DOI：
10.1016/j.gca.2014.04.003
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发表时间：
2014-07-15
影响因子：
5
通讯作者：
Mills, Rachel A.
中科院分区：
文献类型：
--
作者：
Aquilina, Alfred;Homoky, William B.;Mills, Rachel A.
短沉积物芯收集类似的1100米水深的钩脊，在中央盆地的布兰斯菲尔德海峡，南极洲的海底火山建筑物的顶部，以评估铁和锰供应的水柱。低温热液流体平流通过这些沉积物，在某些地方，地下H2S的浓度足够高，以支持丰富的Sclerolinum sp.，一种寄生共生的硫营养细菌的地下管虫。水柱是完全好氧的，并且在所有位置处的氧渗透深度为2-5立方英尺/平方英尺。孔隙水Fe和Mn含量在地下铁质带内较高（最大值）。565 μ mol Fe L-1，>3-7 cmbsf）--比在附近同等水深的背景地点测得的值高14 - 18倍。孔隙沃茨的扩散和平流为表层沉积物提供了大量的Fe和Mn。连续提取的沉积物表明，有一个显着的丰富的一套反应，自生铁矿物在上0-5厘米的沉积物在一个网站的特点是在海底风化壳。在仅具有少量自生矿物表面富集的地点，我们推断沉积物中孔隙水Fe和Mn的渗漏导致底部沃茨水中总溶解Fe和Mn的富集。一个Eh传感器安装在一个拖曳包映射一个独特的Eh签名以上的取芯网站，这是分散在几公里的深度钩岭。我们推测，铁和锰从沉积物中流出的主要机制是由丰富的Sclerolinum sp.沿着在这种动态火山环境中沉积物的物理混合和再悬浮所产生的阶段性增强。我们建议，钩岭沉积物是一个重要的来源，铁和锰的中央盆地的深层沃茨在布兰斯菲尔德海峡，在那里的浓度是持续的底栖通量，和铁是稳定的水柱中的胶体相或配体结合的溶解物种。夹带到德雷克海峡，从而南极绕极流的水质量可以提供一个重要的金属源，这HNLC南大洋地区，如果混合和上涌发生之前，这种金属池去除到底层沉积物。沉积物覆盖的火山脊是常见的裂谷边缘，并可能发挥以前被忽视的作用，在全球铁循环。(C)2014爱思唯尔有限公司版权所有。
Short sediment cores were collected from similar to 1100 m water depth at the top of Hook Ridge, a submarine volcanic edifice in the Central Basin of the Bransfield Strait, Antarctica, to assess Fe and Mn supply to the water column. Low-temperature hydrothermal fluids advect through these sediments and, in places, subsurface H2S is present at high enough concentrations to support abundant Sclerolinum sp., an infaunal tubeworm that hosts symbiotic thiotrophic bacteria. The water column is fully oxic, and oxygen penetration depths at all sites are 2-5 cmbsf. Pore water Fe and Mn content is high within the subsurface ferruginous zone (max. 565 mu mol Fe L-1, >3-7 cmbsf)-14-18 times higher than values measured at a nearby, background site of equivalent water depth. Diffusion and advection of pore waters supply significant Fe and Mn to the surface sediment. Sequential extraction of the sediment demonstrates that there is a significant enrichment in a suite of reactive, authigenic Fe minerals in the upper 0-5 cm of sediment at one site characterised by weathered crusts at the seafloor. At a site with only minor authigenic mineral surface enrichment we infer that leakage of pore water Fe and Mn from the sediment leads to enriched total dissolvable Fe and Mn in bottom waters. An Eh sensor mounted on a towed package mapped a distinct Eh signature above this coring site which is dispersed over several km at the depth of Hook Ridge. We hypothesise that the main mechanism for Fe and Mn efflux from the sediment is breach of the surface oxic layer by the abundant Sclerolinum sp., along with episodic enhancements by physical mixing and resuspension of sediment in this dynamic volcanic environment. We propose that Hook Ridge sediments are an important source of Fe and Mn to the deep waters of the Central Basin in the Bransfield Strait, where concentrations are sustained by the benthic flux, and Fe is stabilised in the water column as either colloidal phases or ligand-bound dissolved species. Entrainment of this water mass into the Drake Passage and thereby the Antarctic Circumpolar Current could provide a significant metal source to this HNLC region of the Southern Ocean if mixing and upwelling occurs before removal of this metal pool to underlying sediments. Sediment-covered volcanic ridges are common within rifted margins and may play a previously overlooked role in the global Fe cycle. (C) 2014 Elsevier Ltd. All rights reserved.