地学前缘 ›› 2009, Vol. 16 ›› Issue (2): 21-51.

• 论文 • 上一篇    下一篇

中国东部燕山期大规模岩浆活动与岩石圈减薄:与大火成岩省的关系

张旗 金惟俊 李承东 王元龙   

  1. 1中国科学院 地质与地球物理研究所, 北京 100029
    2中国地质调查局 天津地质矿产研究所, 天津 300170
  • 出版日期:2009-03-02 发布日期:2009-03-02
  • 作者简介:张旗(1937—),男,研究员,岩石学和地球化学专业。 Email: zq1937@sina.com
  • 基金资助:

    国家自然科学基金重大研究计划项目(90714011)

Yanshanian largescale magmatism and lithosphere thinning in Eastern China: Relation to large igneous province.

  1. 1Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
    2Tianjin Institute of Geology and Mineral Resources, China Geology Survey, Tianjin 300170, China
  • Online:2009-03-02 Published:2009-03-02

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摘要：

论述了大规模岩浆活动与岩石圈减薄的关系,指出软流圈地幔与地壳直接接触时,即岩石圈最大减薄时(岩石圈地幔厚度为0),岩石圈厚度等于地壳厚度。中国东部岩石圈最大减薄的时间在燕山期,在这之前和之后,岩石圈是厚的。讨论了中国东部大规模岩浆活动与板块俯冲的关系,认为中国东部燕山期岩浆活动与太平洋板块没有关系:中国东部不属于环太平洋构造带,不是安第斯型活动陆缘,中生代玄武岩不具有岛弧玄武岩的特征,从中酸性岩浆岩得不出岛弧的结论,从三叠纪开始的古太平洋板块扩张方向的演变也不支持板块向西俯冲的认识。认为中国东部燕山期大规模岩浆活动可能与超级地幔柱的活动有关,是一种新的大火成岩省类型。文中将大火成岩省分为两类:一类为B型大火成岩省,部分熔融发生在岩石圈底部,以发育玄武岩为特征;另一类为G型大火成岩省,部分熔融发生在下地壳底部,以发育大规模花岗质岩浆为特征。根据中国东部大规模岩浆活动的时空分布分出5个大火成岩省:鄂霍茨克(大兴安岭北端)、张广才岭—小兴安岭、华北—大兴安岭、华南和东部沿海大火成岩省。认为岩石圈减薄可以产生多种效应,是地壳演化的最重要的动力学因素,但唯独与地壳浅部的伸展事件无关。还评论了流行的岩石圈减薄的见解,认为流行的见解将岩石圈减薄定位在新生代(岩石圈厚80~120 km)是似是而非的,不是科学的命题。

关键词: 岩石圈减薄;大规模岩浆活动;超级地幔柱;大火成岩省;燕山期;中国东部

Abstract:

In this article, we expound the relationship between the largescale magmatism and lithosphere thinning, and suggest that the lithosphere thickness is equal to the crust thickness when the asthenospheric mantle contacts the crust directly, namely, the lithosphere being the thinnest (the thickness of lithospheric mantle is equal to 0). The lithosphere in the Eastern China is thick except in the Yanshanian. We have discussed the relationship between the largescale magmatism and the plate subduction in Eastern China, and pointed out that there are no relations between the magma activity and the ancient Pacific Ocean plate in  Eastern China during the Yanshanian. This conclusion is based on the following considerations. (1)  Eastern China does not belong to the CircumPacific Ocean tectonics belt, and is not the Andeantype active continental margin. (2) The basalts are not of the island arc basalt characteristic in the Mesozoic era, and the acid magma activity can not induce an island arc settings. (3) The expanding direction of the ancient Pacific Ocean plate during the Triassic period does not support the view of the plate subduction westwards either. The super mantle plume may have caused the largescale magmatism during the Yanshanian in  Eastern China, and may have been a new type of the large igneous province (LIP). We divided the large igneous province into two types: One is the Btype LIP, which is partially melted in the lithosphere bottom and characterized by the development of basalt. Another is the Gtype LIP, which is partially melted in the crust bottom and characterized by the development of largescale granitoid magma. Five large igneous provinces have been differentiated according to the spacetime distribution of the largescale magmatism in Eastern China. They are the Okhotsk LIP (in the north part of Da Hinggan Mountain), the Zhangguangcai MountainXiao Hinggan Mountains LIP, the North ChinaDa Hinggan Mountain LIP, the South China LIP and the Coast of East China. The lithosphere thinning can cause many effects, and is the most important geodynamics of the crust evolution, and may have had no relation with the crust extension during the Yanshanian. We have reviewed the popular opinions on lithosphere thinning, and consider that the popular opinion of lithosphere thinning, which limits the timing of the lithosphere thinning in the Cenozoic era (lithosphere thickness 80120 km), is a paradox, not a scientific proposal.

Key words: lithosphere thinning; largescale magmatism; super mantle plume; large igneous province; Yanshanian; Eastern China

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