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《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]

卷:

第40卷

期数:

2018年第04期

页码:

398-413

栏目:

基础地质与矿产地质

出版日期:

2018-07-15

文章信息/Info

Title:

Geochemical Characteristics of Cenozoic Basalts in Tengchong Block, the Southeastern Margin of Qinghai-Tibet Plateau, China: Constraints on the Nature of Mantle Source

文章编号:

1672-6561(2018)04-0398-16

作者:

姚金; 李双庆; 贺剑峰; 陈福坤

中国科学技术大学 地球和空间科学学院，安徽 合肥 230026

Author(s):

YAO Jin;  LI Shuang-qing;  HE Jian-feng;  CHEN Fu-kun

School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, Anhui, China

关键词:

玄武岩; 橄榄石; 地幔; 辉石岩; 橄榄岩; 俯冲作用; 分离结晶; 腾冲地块

Keywords:

basalt;  olivine;  mantle;  pyroxenite;  peridotite;  subduction;  fractional crystallization;  Tengchong block

分类号:

P588.14+5；P595

DOI:

-

文献标志码:

A

摘要:

腾冲地块位于青藏高原东南缘，是全球特提斯—喜马拉雅构造域东部的重要组成部分，自新生代以来构造活动频繁且岩浆作用强烈，其中广泛发育的新生代玄武岩是研究现今地幔岩石学性质的良好对象。通过研究腾冲地块新生代玄武岩的主、微量元素和Sr-Nd同位素特征，以及其中橄榄石斑晶的地球化学成分，探讨腾冲地块现今地幔源区特征。结果表明：腾冲地块新生代玄武岩富集轻稀土元素和大离子亲石元素，并且富集Th、U、Pb、Zr、Hf，而亏损Sr、Eu，具有高N(⁸⁷Sr)/N(⁸⁶Sr)值(0.705 964~0.706 277)和较低N(¹⁴³Nd)/N(¹⁴⁴Nd)值(0.512 416~0.512 467)，没有受到明显地壳物质的同化混染作用，反映岩浆源区是富集型地幔，其形成过程可能与洋壳俯冲作用有关；橄榄石斑晶晶形较好，具有较低的Fo值、Ni含量以及变化较大的w(FeO)/w(MnO)值，这是受到了早期橄榄石分离结晶和部分熔融的影响；玄武岩的CaO、MgO、FeO含量和w(FeO)/w(MnO)值表现出富硅辉石岩熔体的特征，FC3MS参数为0.84~1.17，指示其地幔源区主要由辉石岩组成，形成可能与洋壳俯冲和硅酸盐熔体交代作用有关。

Abstract:

Tengchong block, located in the southeast margin of Qinghai-Tibet Plateau, is one of the most important parts of the eastern Tethys tectonic belt. Tectonic activities and strong magmatism have widely taken place in Tengchong block since Cenozoic, and the Cenozoic basalts widely developed in Tengchong block are great objects for studying the current mantle. Major, trace elements and Sr-Nd isotopic compositions of Cenozoic basalts in Tengchong block, and the geochemical compositions of olivines in these basalts were studied to explore the source characteristics of the current mantle in Tengchong block. The results show that the Cenozoic basalts in Tengchong block are enriched in LREE, LILE, Th, U, Pb, Zr and Hf, depleted in Sr, Eu, and they have relatively high N(⁸⁷Sr)/N(⁸⁶Sr) (0.705 964-0.706 277) and low N(¹⁴³Nd)/N(¹⁴⁴Nd) (0.512 416-0.512 467) without being significantly assimilated and contaminated during the ascending progress; the magma indicates an enriched mantle, which possibly results from oceanic crust subduction; the olivines have fine crystalline forms and low Fo values, Ni contents and various FeO/MnO ratios, respectively results from the separation and fractional crystallization of olivine in the early stage and the effect of partial melt; the CaO, MgO, FeO contents and FeO/MnO ratios of these basalts all fall into the region of pyroxenite partial melts, and its FC3MS is 0.84-1.17, suggesting that their mantle source is mainly composed of pyroxenite, which may be related to the subduction of oceanic crust and silicate metasomatism.

参考文献/References:

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备注/Memo

备注/Memo:

收稿日期:2018-04-09;修回日期:2018-05-29
基金项目:国家自然科学基金项目(41372072);安徽省自然科学基金项目(1708085MD92)
作者简介:姚 金(1995-),女,山东菏泽人,理学硕士研究生,E-mail:yaojin2015@163.com。
通讯作者:李双庆(1987-),男,河北秦皇岛人,副研究员,理学博士,E-mail:lsq@ustc.edu.cn。

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更新日期/Last Update: 2018-07-27