中沙群岛近海表层沉积物中的火山灰及其对构造环境的响应

鄢全树; 石学法; 刘季花; 陈代庚

中沙群岛近海表层沉积物中的火山灰及其对构造环境的响应

1 海洋沉积与环境地质国家海洋局重点实验室, 国家海洋局第一海洋研究所, 青岛 266061;
2 中国科学院海洋研究所, 青岛 266071

基金项目:

科技基础性工作和社会公益研究专项项目(2003DIB3J114)和青岛市科技将才专项计划项目(05-2-JC-79)

详细信息

作者简介:
鄢全树(1976-),男,博士生,从事海洋地质学和岩石学研究,E-mail:yanquanshu@163.com

中图分类号: P736.4
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- 文章访问数: 1528
- HTML全文浏览量: 106
- PDF下载量: 14
出版历程
- 收稿日期: 2007-02-07
- 修回日期: 2007-04-15

CHARACTERISTICS OF VOLCANIC ASH IN SURFACE SEDIMENTS AROUND ZHONGSHA ISLANDS: RESPONSE TO TECTONIC SETTING IN THE NORTH MARGIN OF THE SOUTH CHINA SEA

1 Key Laboratory of Marine Sedimentology and Environment Geology, State Oceanic Administration, Qingdao 266061, China;
2 Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China

摘要

摘要: 南海中沙近海表层沉积物的轻组分(粒径为63~125 μm)中主要包括有褐色火山玻璃、无色火山玻璃以及火山渣等3种火山灰类型。在硅碱图(TAS)及Al₂O₃、FeO^*、MgO、CaO、Na₂O、K₂O对SiO₂的变化趋势图中可以判断,本区可能存在双峰式火山活动,褐色火山玻璃代表中-基性端元,而无色火山玻璃代表酸性端元。无色火山玻璃与褐色火山玻璃具有共同的岩浆源区,结晶分异可能是源区岩浆演化的主要方式。这种双峰式火山活动暗示火山活动源区处于大陆拉张减薄环境,支持西沙海槽是一个正在活化的伸展大地构造现象这一观点,同时肯定基于地球物理学和岩石学研究资料所提出的海南地幔柱的存在。
- 火山玻璃 /
- 双峰式火山活动 /
- 伸展环境 /
- 南海北缘
Abstract: Volcanic ash in surface sediments around Zhongsha Islands of the South China Sea mainly include three kinds of volcanogenic detritus:that is, brown volcanic glass, colorless volcanic glass and volcanic scoria. TAS diagram for these three kinds of volcanogenic detritus, combined with variation diagram for Al₂O₃,FeO^*,MgO,CaO,Na₂O,K₂O vs SiO₂, shows that there may exist bimodal volcanic activity in the north margin of the South China Sea, brown volcanic glass and colorless volcanic glass represent basic end member and acidic end member respectively, and crystallization differentiation is the main process for magma evolution. The bimodal volcanic activity implies that the source of volcanic activity lay in continental extensional setting, supports that Xisha trench is a phenomenon for ongoing or activating extensional geodynamic setting, and affirms that there exists Hainan plume based on geophysical and petrologic data.
- brown volcanic glass /
- colorless volcanic glass /
- bimodal volcanic activity /
- extensional setting

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参考文献(45)

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