【摘要】：南海及其圍區(qū)新生代巖漿活動具有相似的特征,根據(jù)與南海擴張時間(32~15.5 Ma)的先后關系,將巖漿活動分為三期:擴張前(32 Ma)、擴張期(32~15.5 Ma)和停止擴張后(15.5 Ma)。從巖相學特征可知:擴張前的巖石以三水盆地雙峰式巖漿巖組合為代表;根據(jù)最新的IODP 349航次的鉆孔樣品資料,南海海盆擴張期巖漿巖為典型的MORB,而少量的陸緣巖石資料顯示,該期巖漿巖為堿性玄武巖;停止擴張后巖漿活動可分為兩期,早期以大陸-大洋中脊過渡型拉斑玄武巖為主,晚期以堿性玄武巖為主。除了擴張期南海海盆的MORB,整個新生代的巖漿巖地球化學特征大體一致,與OIB相似,顯示地幔源區(qū)具有不均一性,由一個DMM和一個EM端元組成,且?guī)r石均表現(xiàn)出明顯的Dupal異常特征。對于富集端元的性質和來源、Dupal異常的成因、海南地幔柱是否存在等問題目前存在較大爭議。具OIB特征的巖漿除來自地幔柱作用外,地幔交代作用也是重要的產生機制。本文認為碳酸鹽流體對地幔源區(qū)的交代作用可能在南海地區(qū)新生代巖漿活動中扮演了重要的角色。另外,巖漿巖成巖過程的研究也不夠全面深入,這些都是在今后的研究工作中需要關注的地方,有待后來進一步的研究。
[Abstract]:The Cenozoic magmatic activities in the South China Sea and its environs have similar characteristics. According to the relationship between the magmatic activity and the spreading time of the South China Sea (32 ~ 15.5 Ma), magmatic activity is divided into three periods: before expansion (32 Ma),). Expansion period (32 鹵15. 5 Ma) and after cessation of expansion (15. 5 Ma).) From the petrographic characteristics, it can be concluded that the pre-expansion rocks were represented by the bimodal magmatic assemblage in Sanshui basin; According to the latest drilling sample data of IODP 349 voyage, the extensional magmatic rocks in the South China Sea basin are typical MORB, and a small amount of continental margin rock data show that the magmatic rocks in this period are alkaline basalt. The magmatic activity after stopping the spreading can be divided into two stages: the early stage is continental-oceanic ridge transitional tholeiite and the late stage is alkaline basalt. Except for the extensional South China Sea basin, the geochemical characteristics of the entire Cenozoic magmatic rocks of MORB, in the expansionary South China Sea basin are generally consistent, similar to those of OIB, indicating that the mantle source region is heterogeneous and consists of a DMM and a EM end member. And the rocks show obvious Dupal anomaly characteristics. The origin of the Dupal anomaly and the existence of the mantle plume in Hainan are controversial. In addition to mantle plume, mantle metasomatism is also an important mechanism of OIB magma. It is suggested that the metasomatism of carbonate fluid to mantle source may play an important role in the Cenozoic magmatism in the South China Sea. In addition, the study of diagenetic process of magmatic rock is not comprehensive and thorough, which should be paid attention to in the future research work, and need to be further studied later.
【作者單位】： 中國科學院南海海洋研究所中國科學院邊緣海與大洋地質重點實驗室;中國科學院大學;中山大學海洋科學學院;
【基金】：同位素地球化學國家重點實驗室(中國科學院廣州地球化學研究所)項目(SKLIG-KF-14-08) 廣東省自然科學基金項目(2015A030313836)
【分類號】：P736.1

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