Effects of tides and weather on the sedimentation of iron-oxyhydroxides in a shallow-marine hydrothermal environment at Nagahama Bay, Satsuma Iwo-Jima Island, Kagoshima, southwest Japan
Effects of tides and weather on the sedimentation of iron-oxyhydroxides in a shallow-marine hydrothermal environment at Nagahama Bay, Satsuma Iwo-Jima Island, Kagoshima, southwest Japan
复制标题
潮汐和天气对日本西南部鹿儿岛萨摩硫磺岛长滨湾浅海热液环境中羟基氧化铁沉积的影响
DOI：
10.1111/j.1440-1738.2012.00808.x
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
K. E.
中科院分区：
文献类型：
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作者：
Kiyokawa;S.;Ninomiya;T.;Oguri;K.;Ito;T.;Ikehara;M.;Nagata;T.;and Yamaguchi;K. E.
日本西南部萨摩硫磺岛的长滨湾是研究浅海低温热液活动沉积氧化铁的绝佳地点。它的渔港有一个狭窄的入口，限制了海湾和公海之间的海水交换，允许海底积累含铁物质（铁氧氢氧化物）的细颗粒沉淀物。渔港通常充满橙色至棕色的富铁水，并沉积1.5米厚的富铁沉积物。为了阐明海湾富铁沉淀物的运动和沉积过程，我们对整个潮汐周期的浊度进行了连续分析，并对地表水进行了监测。结果表明：涨潮时海水清澈，退潮时海水颜色浑浊。小潮是弱潮流条件下铁氧氢氧化物沉积的最佳条件。风暴和暴雨也会影响铁氢氧化物的沉淀。风暴波扰动了底部沉积物，导致浑浊度增加和铁氧氢氧化物的快速再沉积，并具有向上细化的顺序。大雨将原本积聚在附近沙滩上的铁氧氢氧化物带到了海湾。我们的发现为浅海热液环境中富铁沉积物积累的最佳条件提供了信息。
Nagahama Bay of Satsuma Iwo‐Jima Island, southwest Japan, is an excellent place for studying sedimentation of iron‐oxyhydroxides by shallow‐marine low‐temperature hydrothermal activity. Its fishing port has a narrow entrance that limits exchange of seawater between the bay and open ocean, allowing the accumulation of fine‐grained precipitates of iron‐bearing materials (Fe‐oxyhydroxides) on the seafloor. The fishing port is usually filled with orange‐ to brown‐colored Fe‐rich water, and deposits >1.5 m thick Fe‐rich sediments. To elucidate the movement and depositional processes of the Fe‐rich precipitates in the bay, we conducted continuous profiling of turbidity throughout the tidal cycle and monitoring of surface water. The results showed that clear seawater entered the bay during the rising tide, and turbid colored water flowed into the ocean during the ebb tide. Neap tide was found to be an optimal condition for sedimentation of Fe‐oxyhydroxides due to weak tidal currents. Storms and heavy rains were also found to have influenced precipitation of Fe‐oxyhydroxides. Storm waves disturbed the bottom sediments, resulting in increased turbidity and rapid re‐deposition of Fe‐oxyhydroxides with an upward‐fining sequence. Heavy rain carried Fe‐oxyhydroxides originally accumulated in nearby beach sands to the bay. Our findings provide information on optimal conditions for the accumulation of Fe‐rich sediments in shallow‐marine hydrothermal settings.