[1]梅盛旺.2018.海南岛新生代玄武质熔岩源区中再循环物质及其 年龄的限定: 来自Hf-Sr-Nd-Pb同位素的制约.大地构造与成矿学,优先出版:001-16.doi:10.16539/j.ddgzyckx.2019.03.013
 MEI Shengwang,and REN Zhongyuan.2018.Recycled Material and its Age in Mantle Source of Cenozoic Basaltic Lavas in Hainan Island: Evidence from Hf-Sr-Nd-Pb Isotopic Compositions.Geotectonica et Metallogenia,优先出版:001-16.doi:10.16539/j.ddgzyckx.2019.03.013
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海南岛新生代玄武质熔岩源区中再循环物质及其 年龄的限定: 来自Hf-Sr-Nd-Pb同位素的制约
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《大地构造与成矿学》[ISSN:ISSN 1001-1552/CN:CN 44-1595/P]

卷:
期数:
2018年优先出版
页码:
001-16
栏目:
出版日期:
2019-12-30

文章信息/Info

Title:
Recycled Material and its Age in Mantle Source of Cenozoic Basaltic Lavas in Hainan Island: Evidence from Hf-Sr-Nd-Pb Isotopic Compositions
作者:
梅盛旺1 2 任钟元1
(1.中国科学院 广州地球化学研究所, 同位素地球化学国家重点实验室, 广东 广州510640; 2.中国科学院 大学, 北京100049)
Author(s):
MEI Shengwang1 2 and REN Zhongyuan1
(1. State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, Guangdong, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China)
关键词:
新生代玄武质熔岩 再循环洋壳 再循环沉积物 海南岛
Keywords:
Cenozoic basaltic lavas recycled oceanic crust recycled sediment Hainan Island
DOI:
10.16539/j.ddgzyckx.2019.03.013
文献标志码:
A
摘要:
再循环洋壳和沉积物在壳?循环过程中扮演着重要的角色。前人研究指出板片俯冲与海南地幔柱形成具有重要的联系, 然而地幔柱源区中是否存在再循环沉积物仍然不得而知。本文将首次报导海南岛新生代玄武质熔岩的Hf同位素, 并将新的Sr-Nd-Pb同位素与前人数据相结合, 限定再循环物质的组成及其年龄。与同位素地幔趋势(mantle array)相比, 给定εNd时, 海南岛玄武质熔岩的εHf值更低; 而且Eu/Eu>1、Sr/Sr>1, 它们与Al2O3、MgO都不存在相关性, 说明Eu和Sr的正异常是继承了源区的特征, 指示源区中存在再循环洋壳物质的参与。海南岛玄武质熔岩的Ce/Pb与εNd、εHf呈正相关关系, Nd/Pb与87Sr/86Sr呈负相关关系, 它们都指向了沉积物端元。根据εHf-εNd模型和Pb同位素演化模型, 推断源区中再循环洋壳和沉积物相对年轻, 其年龄应小于1.0 Ga。这些再循环洋壳和沉积物将进入深部地幔, 并与地幔中的橄榄岩反应形成二阶段辉石岩, 随着海南地幔柱不断上升而发生熔融, 最终熔体喷发至地表形成海南岛玄武质熔岩。
Abstract:
Recycling of oceanic crust and sediments into mantle plays an important role in the chemical evolution of the Earth’s crust-mantle system. Previous studies suggested potential dynamic linkages between the plate subduction and Hainan plume generation, so recycled materials have great effects on mantle source of the Hainan basaltic lavas. However, whether there exist recycled sediments in source is still unknown. In this paper, we report, for the first time, the Hf isotope data of the Cenozoic basaltic lavas in Hainan Island, and combine the new Sr, Nd, and Pb isotope data together with the previous data to constrain the composition and age of the recycled materials. Compared with the Mantle Array, εHf values of Hainan lavas are lower relative to given εNd. Moreover, the lavas have the characteristics of Eu/Eu> 1 and Sr/Sr> 1, but neither of them has correlation with Al2O3 and MgO, indicating that the positive anomalies of Eu and Sr are the characteristics of the source. These serval lines of evidence suggest that recycled oceanic crust plays a significant role in mantle source. The Ce/Pb ratios of Hainan lavas are positively correlated with εNd and εHf, and Nd/Pb ratios are negatively correlated with 87Sr/86Sr, pointing to the subducted oceanic sediments end member. According to the evolution model of the εHf-εNd and Pb isotopes, we conclude that the recycled oceanic crust and sediments in the source region are relatively young, and its age should be less than 1.0 Ga. The high-density eclogite derived from a mixture of recycled oceanic crust and sediments drives the material to sink into the lower mantle and even as deep on the core–mantle boundary, reacting with the ambient peridotite to produce the solid pyroxenite in the rising plume. With Hainan plume rising, the pyroxenite bodies melt continually to generate magma for the Hainan basalts.
更新日期/Last Update: 2019-06-24