浙江诸暨地区陈蔡群加里东期变质年龄的确认及其地质意义

陈蔡群是浙东南地区重要的岩石单位之一,一直被认为是华夏地块变质基底的重要组成部分,20世纪众多地质学家对其开展过研究工作。选取浙江省诸暨市孝四地区的陈蔡群为研究对象,对其开展了详细的LA-ICP-MS同位素定年工作。锆石CL图像和微量元素特征显示其锆石均为变质锆石,17个分析点获得206Pb/238U年龄加权平均值435Ma±4Ma,属于加里东期,此年龄代表了诸暨地区陈蔡群的主变质年龄。结合华南已报道的高精度加里东期年龄纪录,探讨了华南加里东运动发生的时限和运动性质。研究结果表明,华南加里东运动主要发生于420～445Ma之间,435Ma为其一个峰值。

The confirmation of the age of Caledonian Chencai Group in Zhu jiarea of Zhejiang Province and its geological significance.

Chencai Group is one of the most important lithostratigraphic units in southeastern Zhejiang Province, which has been con- sidered as the major component of the metamorphic basement of Cathaysia block. In the last century, many geologists carried out their research work on this group. This paper selected Chencai Group in Xiaosi District of Zhuji City in Zhejiang Province as the study object and carried out in detail the LA-ICP-MS dating work. Zircon CL images and trace element characteristics indicate that the zircons are of metamorphic type, and the weighted average value of~6Pb/Z~U age obtained fi＇om 17 analytical points is 435___4Ma, sug- gesting Caledonian. This paper holds that this age represents the main regional metamorphic age of Chencai Group in Zhuji area. In combination with high-precision age record of Caledonian period already reported by previous researchers, the authors investigated the time limit and nature of the Caledonian Movement in South China. The result shows that the Caledonian Movement in South China occurred mainly in the period between 420-445Ma, with 435Ma as the peak.