| YANG Baoju,ZENG Zhigang,WANG Xiaoyuan. 2015. Characteristics of Sr, Nd and Pb isotopic compositions of hydrothermal Si-Fe-Mn-oxyhydroxides at the PACMANUS hydrothermal field, Eastern Manus Basin. Acta Oceanologica Sinica, 34(8):27－34 |
| Characteristics of Sr, Nd and Pb isotopic compositions of hydrothermal Si-Fe-Mn-oxyhydroxides at the PACMANUS hydrothermal field, Eastern Manus Basin |
| 东马努斯海盆PACMANUS热液区Si-Fe-Mn-羟基氧化物的Sr、Nd、Pb同位素特征 |
| Received:July 11, 2014 Revised:November 05, 2014 |
| DOI：10.1007/s13131-015-0706-8 |
| Key words:Si-Fe-Mn-oxyhydroxides PACMANUS hydrothermal field Sr-Nd-Pb isotopes |
| 中文关键词: Si-Fe-Mn-羟基氧化物 PACMANUS热液区 Sr-Nd-Pb同位素 |
| 基金项目:The National Key Basic Research Program of China under contract No. 2013CB429700; the National Special Fund for the 12th Five Year Plan of COMRA under contract No. DY125-12-R-05; the Strategic Priority Research Program of the Chinese Academy of Sciences under contract No. XDA11030302; the National Special Fund for the 12th Five Year Plan of COMRA under contract Nos DY125-12-R-02 and DY125-11-R-05; the National Natural Science Foundation of China under contract Nos 41325021, 40830849 and 40976027; Shandong Province Natural Science Foundation of China for Distinguished Young Scholars under contract No. JQ200913. |
| Author Name | Affiliation | E-mail | | YANG Baoju | Seafloor Hydrothermal Activity Laboratory of the Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
University of Chinese Academy of Sciences, Beijing 100049, China | | | ZENG Zhigang | Seafloor Hydrothermal Activity Laboratory of the Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China | zgzeng@qdio.ac.cn | | WANG Xiaoyuan | Seafloor Hydrothermal Activity Laboratory of the Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China | |
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| Abstract: |
| Si-Fe-Mn-oxyhydroxides dredged at the PACMANUS (Papua New Guinea-Australia-Canada-Manus) hydrothermal field, Eastern Manus Basin, have 87Sr/86Sr=0.708 079-0.708 581; εNd=5.149 833-6.534 826; 208Pb/204Pb=38.245-38.440; 207Pb/204Pb=15.503-15.560; 206Pb/204Pb=18.682-18.783. 87Sr/86Sr isotope ratios are relatively homogeneous and close to the value of the surrounding seawater (0.709 16). The content of Sr in the samples contributed by seawater was estimated to be 76.7%-83.1% of total amount. The mixing temperature of hydrothermal fluids and seawater were ranging from 53.2℃ to 72.2℃ and the hydrothermal activities were unstable when the samples precipitated. The εNd values of all the samples are positive, which differ from the values of ferromanganese nodules (crusts) with hydrogenic origin. Nd was mainly derived from substrate rocks leached by hydrothermal circulation and preserved the hydrothermal signature. Pb isotopic compositions of most samples show minor variability except Sample #9-2 that has relatively high values of Pb isotopes. The Pb may be derived from the Eastern Manus Basin rocks leached by the hydrothermal fluid. The slightly lower 208Pb/204Pb and 207Pb/204Pb values of the samples indicated that the hydrothermal circulation in PACMANUS was not entire and sufficient, or that hydrothermal circulation had transient changes in the past. Si-Fe-Mn-oxyhydroxides in the samples preserved the heterogeneities of local rocks. |
| 中文摘要: |
| 在东马努斯海盆PACMANUS(巴布亚新几内亚-澳大利亚-加拿大-马努斯)热液区拖网获取的Si-Fe-Mn-羟基氧化物Sr、Nd、Pb同位素的变化范围为:87Sr/86Sr = 0.708079-0.708581;εNd = 5.149833-6.534826;208Pb/204Pb = 38.245-38.440;207Pb/204Pb = 15.503-15.560;206Pb/204Pb = 18.682-18.783.样品的87Sr/86Sr比值变化范围相对均一,接近周围海水的87Sr/86Sr比值(0.70916).海水对样品贡献的Sr含量占总量的76.7%-83.1%.热液流体与海水的混合温度在53.2℃到72.2℃之间,温度变化范围较大说明热液活动不稳定.所有样品的εNd值均为正值,与水成成因的铁锰结核(结壳)明显不同.样品中的Nd主要来自热液活动对基底岩石的淋滤,并保留了热液活动的信息.样品的Pb同位素变化范围较小.除了样品#9-2具有相对较高的Pb同位素组成外,大部分样品的Pb同位素组成变化范围较小.其中大部分样品的208Pb/204Pb和207Pb/204Pb比值与东马努斯海盆岩石、岩浆,PACMANUS硫化物的值类似,暗示样品的Pb来自热液流体对东马努斯海盆基底岩石的淋滤.另外,样品的208Pb/204Pb和207Pb/204Pb比值稍微偏低,说明热液流体在基底岩石中的循环过程并不充分,或者热液活动在过去出现了间歇性的暂停,Si-Fe-Mn-羟基氧化物保存了基底岩石的不均一性. |
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