| 劳盆地与马努斯盆地俯冲熔体与流体组分的识别——Sr-Nd-Pb同位素与独立成分分析 |
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| 引用本文： | 伍锡昌,初凤友,王巍,李正刚,陈灵,毕冬伟,王建强.劳盆地与马努斯盆地俯冲熔体与流体组分的识别——Sr-Nd-Pb同位素与独立成分分析[J].吉林大学学报(地球科学版),2019,49(2):414-424. |
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| 作者姓名： | 伍锡昌 初凤友 王巍 李正刚 陈灵 毕冬伟 王建强 |
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| 作者单位： | 国家海洋局海底科学重点实验室/第二海洋研究所, 杭州 310012 |
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| 基金项目： | 国家重点基础研究发展计划（"973"计划）项目（2013CB429705，2013CB429701）；浙江省自然科学基金项目（LQ17D060005，LQ17D060004）；海洋二所基本科研业务专项（JG1605，JG1603，JG1410） |
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| 摘 要： | 为了探讨俯冲沉积物与蚀变洋壳组分对弧后盆地岩浆作用的影响,利用独立成分分析从劳盆地、马努斯盆地,以及太平洋与印度洋共634组Sr-Nd-Pb同位素数据中提取了5个独立成分(IC1—IC5)。其中:IC1与_87Sr/_86Sr、Th/Nb值为负相关关系,表明其能够代表弧下地幔中的俯冲沉积物熔体组分的影响,能够很好地区别弧后盆地与洋中脊;弧后盆地IC5与Ba/Th值为负相关关系,暗示其能够反映弧下地幔中的俯冲蚀变洋壳脱水流体组分的影响;IC5与κ值(1.03Th/U)之间的关系,也说明洋中脊IC5可能与地幔中再循环蚀变洋壳的年龄有关。进而通过对比马努斯和劳盆地岩石中IC1与IC5间的差异,发现马努斯盆地东部裂谷(ER)表现出绝对值更高的IC1负异常以及与劳盆地相似的IC5特征,而马努斯盆地扩张中心与扩张转换带(MSC&ETZ)则表现出类似劳盆地的IC1特征以及更高的IC5正异常特征。两个盆地间的差异表明,ER更多地受到沉积物熔体组分影响,MSC&ETZ更少地受到俯冲洋壳脱水流体组分影响。其中,沉积物熔体组分影响可能与New Britain trench与Tonga trench巨大的沉积物厚度差异有关,而俯冲洋壳脱水流体组分影响可能受到了弧后扩张中心与俯冲带间距离的控制。
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| 关 键 词： | 独立成分分析(ICA) 弧后盆地 SR-ND-PB同位素 蚀变洋壳 俯冲沉积物 劳盆地 马努斯盆地 |
| 收稿时间： | 2018-12-28 |
Recognition of Subduction Melt and Fluid Component in Lau and Manus Basins: Sr-Nd-Pb Isotope Ratios and Independent Component Analysis |
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| Wu Xichang,Chu Fengyou,Wang Wei,Li Zhenggang,Chen Ling,Bi Dongwei,Wang Jianqiang.Recognition of Subduction Melt and Fluid Component in Lau and Manus Basins: Sr-Nd-Pb Isotope Ratios and Independent Component Analysis[J].Journal of Jilin Unviersity:Earth Science Edition,2019,49(2):414-424. |
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| Authors: | Wu Xichang Chu Fengyou Wang Wei Li Zhenggang Chen Ling Bi Dongwei Wang Jianqiang |
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| Institution: | Key Laboratory of Submarine Geoscience/Second Institute of Oceanography, State Oceanic Administration(SOA), Hangzhou 310012, China |
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| Abstract: | The effects of subducted sediments and altered oceanic crust (AOC) on back-arc magmatism were studied using independent component analysis on multi-isotope dataset. Sr-Nd-Pb isotope data of magmatic rocks from Lau and Manus basins, as well as the Pacific and Indian oceanic ridges, were analyzed, and five independent components (ICs) were identified. The negative correlation between IC1 and 87Sr/86Sr and Th/Nb suggests that the IC1 represents the influence of hydrous melt derived from subducted sediments on the sub-arc mantle, and can be used to distinguish back-arc basin from mid-ocean ridge settings. The negative correlation between IC5 and Ba/Th suggests that IC5 may reflect the influence of aqueous fluid derived from the AOC on the sub-arc mantle. Furthermore, the correlation between IC5 and Th/U indicates that the IC5 values may be related to the age of recycled oceanic crust in the mantle. A comparison between the IC1 and IC5 values of Lau and Manus basins shows that the eastern rift (ER) of Manus basin exhibits similar IC5 but lower IC1 relative to that of Lau basin, whereas the manus spreading center (MSC) and extensional transform zone (ETZ) of Manus basin show similar IC1 but higher IC5 compared with that of Lau basin. These differences suggest that the influences of sediment melts are the strongest in the ER, while AOC fluid exerts similar influence on ER and Lau basin, but much less on MSC and ETZ. We believe that the difference in the degree of sediment melt influence may be associated with variable sediment thickness being subducted into the New Britain and Tonga trenches, while the extent of AOC fluid influence is controlled by the distance of back-arc ridges away from the trench. |
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| Keywords: | independent component analysis back-arc basin Sr-Nd-Pb isotope altered oceanic crust subducted sediment Lau basin Manus basin |
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