The deep water in the ridge segment between 10°18’S and 10°57’S of northern Central Indian Ridge was surveyed with CTD and AUV for seafloor hydrothermal activities. During the survey, 25 CTD hydrocasts were made, and seawater samples were collected for analyses of chemical tracers like dissolved manganese (DMn). In the rift valley between 10°40’S and 10°57’S, consistent backscatter anomalies (up to 0.013 ΔNTU) were found in deep water, indicating excess of suspended particulate at the depth between 3050 and 3500 m. The seawater samples from this turbid layer was characterized with high concentration of dissolved manganese (maximum DMn = 39 nmol/L) and excess helium-3 (maximum δ 3 He = 17.1%) and thus confirmed the possible hydrothermal activities in that area. The distribution of turbidity and DMn in deep water apparently suggests that there could be active vent(s) located close to the eastern wall (10°47.5’S; 66°38.6’E) of the valley, near southern end of the ridge segment. The physiochemical characters of the plume suggest the source fluid might have originated from reactions involving both mafic and ultramafic rocks, and its nature is comparable to other plumes in the Indian Ocean.

中文翻译：

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中印度洋脊 10°47'S 附近深水柱浊度升高和溶解锰：热液活动研究

利用CTD和AUV对中印度海脊北部10°18'S和10°57'S之间的海脊段深水进行了海底热液活动调查。在调查过程中，进行了 25 次 CTD 水力浇注，并收集了海水样品以分析溶解锰 (DMn) 等化学示踪剂。在 10°40'S 和 10°57'S 之间的裂谷中，在深水中发现了一致的反向散射异常（高达 0.013 ΔNTU），表明在 3050 和 3500 m 之间的深度处悬浮颗粒过多。来自该混浊层的海水样品具有高浓度溶解锰（最大 DMn = 39 nmol/L）和过量氦 3（最大 δ 3 He = 17.1%）的特征，因此证实了该地区可能存在热液活动。深水中浊度和 DMn 的分布显然表明，在靠近山脊段南端的山谷东壁（10°47.5'S；66°38.6'E）附近可能存在活动喷口. 羽流的理化特征表明，源流体可能来源于基性岩和超基性岩的反应，其性质与印度洋的其他羽流相当。