| GUO Kun,ZHAI Shikui,YU Zenghui,ZENG Zhigang,WANG Xiaoyuan,YIN Xuebo. 2018. Geochemical characteristics of major and trace elements in the Okinawa Trough basaltic glass. Acta Oceanologica Sinica, 37(2):14－24 |
| Geochemical characteristics of major and trace elements in the Okinawa Trough basaltic glass |
| 冲绳海槽玄武岩玻璃主量、微量元素地球化学特征 |
| Received:January 05, 2017 Revised:February 24, 2011 |
| DOI：10.1007/s13131-017-1075-2 |
| Key words:Okinawa Trough basaltic glass geochemistry magmatic evolution subducted component |
| 中文关键词: 冲绳海槽 玄武岩玻璃 地球化学 岩浆演化 俯冲组分 |
| 基金项目:The National Basic Research Program of China under contract No. 2013CB429702; the open fund project supported by the Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology under contract No. MGQNLM-KF201707; the National Natural Science Foundation of China under contract Nos 41476044, 41325021 and 41306053; the Special Fund for the Taishan Scholar Program of Shandong Province under contract No. ts201511061; the AoShan Talents Program supported by Qingdao National Laboratory for Marine Science and Technology under contract No. 2015ASTP-0S17; the Innovative Talent Promotion Program under contract No. 2012RA2191; the Science and Technology Development Program of Shandong Province under contract No. 2013GRC31502. |
| Author Name | Affiliation | E-mail | | GUO Kun | Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China
Key Laboratory of Submarine Geosciences and Prospection of Ministry of Education, Ocean University of China, Qingdao 266100, China | | | ZHAI Shikui | Key Laboratory of Submarine Geosciences and Prospection of Ministry of Education, Ocean University of China, Qingdao 266100, China | zhai2000@ouc.edu.cn | | YU Zenghui | Key Laboratory of Submarine Geosciences and Prospection of Ministry of Education, Ocean University of China, Qingdao 266100, China | | | ZENG Zhigang | Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China | | | WANG Xiaoyuan | Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China | | | YIN Xuebo | Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China | |
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| Abstract: |
| The Okinawa Trough (OT) is a back-arc basin at an initial spreading stage that is under the influence of subduction of the Philippine Sea Plate. In this study, we analyzed the geochemical compositions of basaltic glass in the OT and discussed the effects of different magmatic sources, evolution, and subducted components in basalts. Our results showed that the middle and southern regions of the OT exhibit characteristics consistent with an iron-rich tholeiite series. Trace element proportions conform to the typical spider diagram pattern characteristic of back-arc basin basalts, rich in large ion lithophile elements (LILEs) including Rb, Ba, Pb, U, and Th, while depleted in high field-strength elements (HFSEs) including Nb, Ta, Zr, Hf, and Ti. The distribution of rare earth elements (REEs) is also consistent with enrichment by right-leaning light rare earth elements (LREEs). The addition of enriched mantle type I (EMI) materials as well as mantle heterogeneity may have led to variable degrees of enrichment in different regions. The magma source of the middle trough has undergone crystallization towards pyroxene, while development of plagioclase was restricted partly, and the crystallization of spinel and olivine ceased altogether. At the same time, crystallization of the southern OT magma source was dominated by olivine and including the formation of plagioclase, pyroxene, and magnetite (or titanomagnetite). Finally, the results of this study showed that 90% Th, 95% Ba in the southern basalt, 50%-70% Th and 70%-90% Ba in the middle basalt originated from subducted component. Different subducted component influence may be due to different subduction zone structural feature. |
| 中文摘要: |
| 冲绳海槽是一个处于弧后盆地扩张早期阶段、正在受菲律宾海板块俯冲作用影响的弧后盆地。本文分析了冲绳海槽玄武岩玻璃的地球化学组成，研究了玄武岩岩浆源区的性质、岩浆演化及俯冲组分的影响等。结果表明：（1）冲绳海槽中部和南部玄武岩都表现出Fe富集的拉斑玄武岩系列的特征。微量元素表现出大离子亲石元素Rb、Ba、Pb以及U、Th富集，高场强元素Nb、Ta、Zr、Hf和Ti亏损的典型弧后盆地玄武岩微量元素蛛网图模式。稀土元素表现出右倾LREE富集型的特点。（2）海槽岩浆源区为N-MORB型地幔，中部岩浆源区比南部更富集，EMI型地幔物质的加入、地幔不均一性可能造成海槽不同区域不同富集程度的原因。（3）海槽中部岩浆源区经历了以辉石为主的结晶演化，斜长石的结晶受到了抑制，尖晶石和橄榄石已经停止了结晶。而南部岩浆源区经历了以橄榄石为主的结晶，还包括斜长石、辉石、磁铁矿（钛磁铁矿）的结晶。（4）南部玄武岩中90%的Th和95%的Ba来自于俯冲组分，中部玄武岩来自俯冲组分的Th和Ba分别为50%~70%和70%~90%。不同俯冲组分的影响，可能是因为海槽不同区段不同的俯冲带结构。 |
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