对新桥岩体形成时代的讨论

ON THE AGE OF THE XINQIAO MASSIF

摘要: 对福建大田新桥岩体形成时代问题,目前尚存在着不同的认识。本文根据该岩体同位素年龄成果,锆石矿物学特点,区域地质背景的综合分析,认为该岩体的主要形成时代,应属于加里东期产物。

Abstract: The Xinqiao massif in Datian, Fujian, occurs as a batholith in the middle part of the Zhenghe-Dapu deep fracture belt. This massif consists mainly of typical remoulded granite resulting from metamorphism, metasomatism and partial melting. But divergent views exist as to its age. Some people consider it to be of Hercynian age, while others consider it to be early Yanshanian in age. According to a comprehensive analysis of the isotopic age determination, zircon mineralogy and region geoloical setting of the massif, it may be considered that the 410 Ma zircon U-Pb age is the age of crystallization of zircon when the protolith was reconstituted into granite by means of metamorphism and metasomatism or partial melting. Therefore the age of the massif should be Caledonian, but the possibility of the local existence of a Hercynian massif and its influence is not ruled out.