中国东部中生代岩浆活动与板块俯冲的关系——浙闽与日本弧和安第斯弧的对比及其意义
发布时间：2018-08-23 09:43
【摘要】：中国东部中-新生代的构造背景是中国地质学界最关注的问题之一。自20世纪70年代板块构造学说引入中国后,中国地质学家普遍接受了太平洋板块向欧亚板块俯冲导致中国东部中生代强烈的构造-岩浆活动和相应的成矿作用的观点,乃至成为被中外学者普遍认知的理论,至今仍然广泛流传。但是,本文研究认为问题很多。众所周知,岛弧是以玄武岩出露为主,大陆弧则是以安山岩出露最多,而中国东部玄武岩和安山岩极不发育。本文按照大数据研究思路,对日本和安第斯全部新生代岩浆岩的统计研究表明,上述认识基本上是对的:日本弧主要是玄武岩,其次是安山岩;安第斯弧主要是安山岩,其次是玄武岩;而中国东部(以浙闽地区为代表),主要是花岗岩,其次是玄武岩,出现双峰式分布的特征。看来,中国东部与日本和安第斯的构造背景完全不同,中国东部没有俯冲作用的明显证据。其次,岛弧和大陆弧有明显的成分和结构分带,如日本弧,从海沟开始,岩浆活动是从前弧-岛弧-后弧-弧后(frant-arc,arc,rear-arc,back-arc)。安第斯弧不如日本弧明显,从海沟向东到大陆是从弧前杂岩-弧岩浆岩-弧后盆地。中国东部(包括东海大陆架、中国东部沿海)与俯冲有关的结构和成分分带哪里有?我们的研究集中讨论了浙闽地区400km宽度范围内侏罗纪-白垩纪岩浆岩的分布,从年龄到地球化学(Si O2的变化,Mg O、K2O的变化,年龄的变化等等),基本上见不到有从东到西分带的趋势,这种情况如何与板块俯冲作用联系起来呢?岛弧岩浆岩主要来源于亏损的地幔、洋壳、深海沉积物,以及由俯冲带带来的流体,因此,岛弧岩浆岩洋壳的特征非常明显。大陆弧也来自地幔,但是,岩浆穿过大陆壳,会带来明显的陆壳混染的影响,因此安第斯型岩浆岩陆壳的印记比较明显。大陆岩浆岩如果不考虑俯冲带的影响,岩浆岩应当来自高热的软流圈地幔。如果高热的软流圈停滞在岩石圈底部,在那里发生部分熔融,形成的应当是大陆溢流玄武岩,而中酸性岩浆岩非常少;相反,如果高热的软流圈突破岩石圈的阻隔而上升到地壳底部,则会加热下地壳底部使之发生部分熔融,形成的则是大量的酸性花岗岩,而玄武岩和安山岩很少。峨眉山是前面的情况,中国东部则是后面的情况。中国东部岩浆岩究竟与日本、安第斯有何异同点?应当是岩石学家研究的首要命题,建议中国的岩石学家和地球化学家不要仅限于中国东部的研究,而将研究的触角延伸一步,深入细致地研究一下日本和安第斯岩浆岩的情况,再对比中国东部的情况,如此可能会得出新的认识,这样的认识也许才可能有益于解决中国东部岩浆岩形成背景的问题。
[Abstract]:The tectonic background of Mesozoic-Cenozoic in eastern China is one of the most concerned problems in Chinese geologists. Since the introduction of plate tectonics theory into China in the 1970s, Chinese geologists have generally accepted the view that the Pacific plate subduction to the Eurasian plate led to strong Mesozoic tectonic-magmatic activity and corresponding mineralization in eastern China. Even as a theory widely recognized by Chinese and foreign scholars, it is still widely spread. However, this study thinks that there are many problems. It is well known that basalt is dominant in island arc, andesite is the most exposed in continental arc, and basalt and andesite are not very developed in eastern China. According to the big data research idea, the statistical study of all Cenozoic magmatic rocks in Japan and the Andes shows that the above understanding is basically correct: the Japanese arc is mainly basalt, followed by the andesite, and the Andes arc is mainly andesite. Basalt is followed by basalt, while in eastern China (represented by Zhejiang and Fujian), it is mainly granite, followed by basalt, with bimodal distribution. It appears that the tectonic setting of eastern China is completely different from that of Japan and the Andes, and there is no obvious evidence of subduction in eastern China. Secondly, there are obvious compositional and structural zonation between island arc and continental arc, such as Japanese arc. From trench, magmatic activity is frant-arcarc-back-arc (frant-arcarcar-rearcarcback-arc). Andes arc is less obvious than Japanese arc, from trench to continent is from forearc complex, arc magma to back-arc basin. Where are the subduction-related structures and subduction zones in eastern China (including the continental shelf of the East China Sea and the eastern coast of China)? Our studies have focused on the distribution of Jurassic-Cretaceous magmatic rocks in the 400km width range from age to geochemistry (Sio _ 2) and the variation of mg _ (O) O _ (K _ 2O). Age changes and so on), basically there is no trend from east to west, how is this situation associated with plate subduction? Island arc magmatic rocks are mainly derived from depleted mantle, oceanic crust, deep-sea sediments, and fluids from subduction zones. Therefore, the characteristics of island arc magmatic oceanic crust are very obvious. The continental arc also comes from the mantle, but magma passing through the continental crust has obvious influence of continental crust mixing, so the continental crust of the Andes magmatic rock has obvious imprint. If the continental magmatic rocks do not consider the subduction zone, the magmatic rocks should come from the high-heat asthenospheric mantle. If the high-heat asthenosphere stagnates at the bottom of the lithosphere, where partial melting occurs, it should be continental overflow basalt, while intermediate-acid magma is very few; conversely, If the high-heat asthenosphere breaks through the barrier of the lithosphere and rises to the bottom of the crust, it will heat the bottom of the crust to make it partially melt and form a large amount of acidic granite, while basalt and andesite are rare. Mount Emei is in front, and eastern China is behind. What are the similarities and differences between the magmatic rocks in eastern China and Japan and the Andes? It is suggested that Chinese petrologists and geochemists should not limit their research to the eastern part of China, but extend the tentacles of the study one step further and study the situation of the Japanese and Andean magmatic rocks in depth and detail. By comparing the situation in eastern China, a new understanding may be obtained, which may help to solve the problem of the formation background of magmatic rocks in eastern China.
【作者单位】： 兰州大学地质科学与矿产资源学院 甘肃省西部矿产资源重点实验室;中国科学院地质与地球物理研究所岩石圈演化国家重点实验室;南京地质矿产研究所;中山大学地球科学与工程学院;
【基金】：中央高校基本科研业务费项目(Lzu-Jbky-2012-128) 中国地质调查局项目(121201011000150012-02)联合资助
【分类号】：P542;P588.11
[Abstract]:The tectonic background of Mesozoic-Cenozoic in eastern China is one of the most concerned problems in Chinese geologists. Since the introduction of plate tectonics theory into China in the 1970s, Chinese geologists have generally accepted the view that the Pacific plate subduction to the Eurasian plate led to strong Mesozoic tectonic-magmatic activity and corresponding mineralization in eastern China. Even as a theory widely recognized by Chinese and foreign scholars, it is still widely spread. However, this study thinks that there are many problems. It is well known that basalt is dominant in island arc, andesite is the most exposed in continental arc, and basalt and andesite are not very developed in eastern China. According to the big data research idea, the statistical study of all Cenozoic magmatic rocks in Japan and the Andes shows that the above understanding is basically correct: the Japanese arc is mainly basalt, followed by the andesite, and the Andes arc is mainly andesite. Basalt is followed by basalt, while in eastern China (represented by Zhejiang and Fujian), it is mainly granite, followed by basalt, with bimodal distribution. It appears that the tectonic setting of eastern China is completely different from that of Japan and the Andes, and there is no obvious evidence of subduction in eastern China. Secondly, there are obvious compositional and structural zonation between island arc and continental arc, such as Japanese arc. From trench, magmatic activity is frant-arcarc-back-arc (frant-arcarcar-rearcarcback-arc). Andes arc is less obvious than Japanese arc, from trench to continent is from forearc complex, arc magma to back-arc basin. Where are the subduction-related structures and subduction zones in eastern China (including the continental shelf of the East China Sea and the eastern coast of China)? Our studies have focused on the distribution of Jurassic-Cretaceous magmatic rocks in the 400km width range from age to geochemistry (Sio _ 2) and the variation of mg _ (O) O _ (K _ 2O). Age changes and so on), basically there is no trend from east to west, how is this situation associated with plate subduction? Island arc magmatic rocks are mainly derived from depleted mantle, oceanic crust, deep-sea sediments, and fluids from subduction zones. Therefore, the characteristics of island arc magmatic oceanic crust are very obvious. The continental arc also comes from the mantle, but magma passing through the continental crust has obvious influence of continental crust mixing, so the continental crust of the Andes magmatic rock has obvious imprint. If the continental magmatic rocks do not consider the subduction zone, the magmatic rocks should come from the high-heat asthenospheric mantle. If the high-heat asthenosphere stagnates at the bottom of the lithosphere, where partial melting occurs, it should be continental overflow basalt, while intermediate-acid magma is very few; conversely, If the high-heat asthenosphere breaks through the barrier of the lithosphere and rises to the bottom of the crust, it will heat the bottom of the crust to make it partially melt and form a large amount of acidic granite, while basalt and andesite are rare. Mount Emei is in front, and eastern China is behind. What are the similarities and differences between the magmatic rocks in eastern China and Japan and the Andes? It is suggested that Chinese petrologists and geochemists should not limit their research to the eastern part of China, but extend the tentacles of the study one step further and study the situation of the Japanese and Andean magmatic rocks in depth and detail. By comparing the situation in eastern China, a new understanding may be obtained, which may help to solve the problem of the formation background of magmatic rocks in eastern China.
【作者单位】： 兰州大学地质科学与矿产资源学院 甘肃省西部矿产资源重点实验室;中国科学院地质与地球物理研究所岩石圈演化国家重点实验室;南京地质矿产研究所;中山大学地球科学与工程学院;
【基金】：中央高校基本科研业务费项目(Lzu-Jbky-2012-128) 中国地质调查局项目(121201011000150012-02)联合资助
【分类号】：P542;P588.11
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