| 伊豆-小笠原前弧地区Hahajima海山蛇纹石化橄榄岩岩石学和地球化学研究 |
| |
| 引用本文： | 吴拓宇,田丽艳,高金尉,董彦辉.伊豆-小笠原前弧地区Hahajima海山蛇纹石化橄榄岩岩石学和地球化学研究[J].海洋学报(英文版),2019,38(11):99-110. |
| |
| 作者姓名： | 吴拓宇 田丽艳 高金尉 董彦辉 |
| |
| 作者单位： | 北京迈勤能源技术服务有限公司, 北京, 100004, 中国,中国科学院深海科学与工程研究所, 三亚, 572000, 中国;青岛海洋科学与技术国家实验室, 海洋地质过程与功能实验室, 青岛, 266237, 中国,中国科学院深海科学与工程研究所, 三亚, 572000, 中国;青岛海洋科学与技术国家实验室, 海洋地质过程与功能实验室, 青岛, 266237, 中国,国家海洋局第二海洋研究所, 海底科学重点实验室, 杭州, 310012, 中国 |
| |
| 基金项目： | The National Natural Science Foundation of China under contract Nos 41506047, 41876044 and 91858214; the Chinese Academy of Sciences’ Strategic Priority Research Program Grant under contract Nos XDB06030103 and XDB06030204. |
| |
| 摘 要： | Serpentinites, which contain up to 13 wt% of water, are important reservoirs for chemical recycling in subduction zones. In the past two decades, forearc mantle serpentinites were identified in different locations around the world. Here, we present petrology and whole rock chemistry of ultramafic and mafic rocks dredged from the Hahajima Seamount, which is located 24–40 km west to the junction of the Izu-Bonin Trench and the Mariana Trench. Nearly all the collected samples are extensively hydrated, and olivine grains in ultramafic rocks are replaced by serpentine minerals, with only one sample preserving remaining trace of orthopyroxene. Our new results show that the Hahajima serpentinized peridotite samples are all MgO-rich(～42 wt%), but have low contents in Al_2O_3, CaO, rare earth and high field strength elements, which is consistent with the overall depleted character of their mantle protoliths. Model calculations indicate that these Hahajima peridotite samples were derived from 10%–25% partial melting of the presumed fertile mantle source, which is generally lower than those of peridotites from Torishima Forearc Seamount, Conical Seamount and South Chamorro Seamount(mostly25%). All the serpentinites from these four forearc seamounts show strong enrichment in fluid-mobile and lithophile elements(Li, Sr, Pb and U). In details, Hahajima Seamount serpentinites do not have obvious enrichment in Cs and Rb, and display remarkably high abundances of U. These observations indicate that the serpentinization of Hahajima peridotites occurred by addition of seawater or low temperature seawater-derived hydrothermal fluid, without or with little contribution from slab-derived fluids. The geochemical signature of serpentinites from Hahajima Seamount could be interpreted as the result of the combination of extensive partial melting and subsequent percolation of seawater through the mantle wedge.
|
| 关 键 词： | Hahajima海山 蛇纹石化橄榄岩 伊豆-小笠原-马里亚纳前弧海山 流体活动元素 |
| 收稿时间： | 2018/11/7 0:00:00 |
Petrology and geochemistry of serpentinized peridotites from Hahajima Seamount in Izu-Bonin forearc region |
| |
| Wu Tuoyu,Tian Liyan,Gao Jinwei and Dong Yanhui.Petrology and geochemistry of serpentinized peridotites from Hahajima Seamount in Izu-Bonin forearc region[J].Acta Oceanologica Sinica,2019,38(11):99-110. |
| |
| Authors: | Wu Tuoyu Tian Liyan Gao Jinwei and Dong Yanhui |
| |
| Institution: | 1.Beijing Maiqin Nengyuan Jishu Fuwu Co. Ltd, Beijing 100004, China2.Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China;Laboratory for Marine Geology, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China3.Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China |
| |
| Abstract: | Serpentinites, which contain up to 13 wt% of water, are important reservoirs for chemical recycling in subduction zones. In the past two decades, forearc mantle serpentinites were identified in different locations around the world. Here, we present petrology and whole rock chemistry of ultramafic and mafic rocks dredged from the Hahajima Seamount, which is located 24–40 km west to the junction of the Izu-Bonin Trench and the Mariana Trench. Nearly all the collected samples are extensively hydrated, and olivine grains in ultramafic rocks are replaced by serpentine minerals, with only one sample preserving remaining trace of orthopyroxene. Our new results show that the Hahajima serpentinized peridotite samples are all MgO-rich (~42 wt%), but have low contents in Al2O3, CaO, rare earth and high field strength elements, which is consistent with the overall depleted character of their mantle protoliths. Model calculations indicate that these Hahajima peridotite samples were derived from 10%–25% partial melting of the presumed fertile mantle source, which is generally lower than those of peridotites from Torishima Forearc Seamount, Conical Seamount and South Chamorro Seamount (mostly >25%). All the serpentinites from these four forearc seamounts show strong enrichment in fluid-mobile and lithophile elements (Li, Sr, Pb and U). In details, Hahajima Seamount serpentinites do not have obvious enrichment in Cs and Rb, and display remarkably high abundances of U. These observations indicate that the serpentinization of Hahajima peridotites occurred by addition of seawater or low temperature seawater-derived hydrothermal fluid, without or with little contribution from slab-derived fluids. The geochemical signature of serpentinites from Hahajima Seamount could be interpreted as the result of the combination of extensive partial melting and subsequent percolation of seawater through the mantle wedge. |
| |
| Keywords: | Hahajima Seamount|serpentinized peridotites|IBM forearc seamounts|fluid-mobile elements |
| 本文献已被 CNKI 等数据库收录！ |
| 点击此处可从《海洋学报(英文版)》浏览原始摘要信息 |
| 点击此处可从《海洋学报(英文版)》下载免费的PDF全文 |
|
