發(fā)布時間：2018-08-23 09:43

【摘要】：中國東部中-新生代的構造背景是中國地質(zhì)學界最關注的問題之一。自20世紀70年代板塊構造學說引入中國后,中國地質(zhì)學家普遍接受了太平洋板塊向歐亞板塊俯沖導致中國東部中生代強烈的構造-巖漿活動和相應的成礦作用的觀點,乃至成為被中外學者普遍認知的理論,至今仍然廣泛流傳。但是,本文研究認為問題很多。眾所周知,島弧是以玄武巖出露為主,大陸弧則是以安山巖出露最多,而中國東部玄武巖和安山巖極不發(fā)育。本文按照大數(shù)據(jù)研究思路,對日本和安第斯全部新生代巖漿巖的統(tǒng)計研究表明,上述認識基本上是對的:日本弧主要是玄武巖,其次是安山巖;安第斯弧主要是安山巖,其次是玄武巖;而中國東部(以浙閩地區(qū)為代表),主要是花崗巖,其次是玄武巖,出現(xiàn)雙峰式分布的特征�？磥�,中國東部與日本和安第斯的構造背景完全不同,中國東部沒有俯沖作用的明顯證據(jù)。其次,島弧和大陸弧有明顯的成分和結構分帶,如日本弧,從海溝開始,巖漿活動是從前弧-島弧-后弧-弧后(frant-arc,arc,rear-arc,back-arc)。安第斯弧不如日本弧明顯,從海溝向東到大陸是從弧前雜巖-弧巖漿巖-弧后盆地。中國東部(包括東海大陸架、中國東部沿海)與俯沖有關的結構和成分分帶哪里有?我們的研究集中討論了浙閩地區(qū)400km寬度范圍內(nèi)侏羅紀-白堊紀巖漿巖的分布,從年齡到地球化學(Si O2的變化,Mg O、K2O的變化,年齡的變化等等),基本上見不到有從東到西分帶的趨勢,這種情況如何與板塊俯沖作用聯(lián)系起來呢?島弧巖漿巖主要來源于虧損的地幔、洋殼、深海沉積物,以及由俯沖帶帶來的流體,因此,島弧巖漿巖洋殼的特征非常明顯。大陸弧也來自地幔,但是,巖漿穿過大陸殼,會帶來明顯的陸殼混染的影響,因此安第斯型巖漿巖陸殼的印記比較明顯。大陸巖漿巖如果不考慮俯沖帶的影響,巖漿巖應當來自高熱的軟流圈地幔。如果高熱的軟流圈停滯在巖石圈底部,在那里發(fā)生部分熔融,形成的應當是大陸溢流玄武巖,而中酸性巖漿巖非常少;相反,如果高熱的軟流圈突破巖石圈的阻隔而上升到地殼底部,則會加熱下地殼底部使之發(fā)生部分熔融,形成的則是大量的酸性花崗巖,而玄武巖和安山巖很少。峨眉山是前面的情況,中國東部則是后面的情況。中國東部巖漿巖究竟與日本、安第斯有何異同點?應當是巖石學家研究的首要命題,建議中國的巖石學家和地球化學家不要僅限于中國東部的研究,而將研究的觸角延伸一步,深入細致地研究一下日本和安第斯巖漿巖的情況,再對比中國東部的情況,如此可能會得出新的認識,這樣的認識也許才可能有益于解決中國東部巖漿巖形成背景的問題。
[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.
【作者單位】： 蘭州大學地質(zhì)科學與礦產(chǎn)資源學院 甘肅省西部礦產(chǎn)資源重點實驗室;中國科學院地質(zhì)與地球物理研究所巖石圈演化國家重點實驗室;南京地質(zhì)礦產(chǎn)研究所;中山大學地球科學與工程學院;
【基金】：中央高�；究蒲袠I(yè)務費項目(Lzu-Jbky-2012-128) 中國地質(zhì)調(diào)查局項目(121201011000150012-02)聯(lián)合資助
【分類號】：P542;P588.11

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