摘要
熊店榴辉岩产于大别山西部苏家河构造混杂岩带内,是典型的高压—超高压中温榴辉岩。作者应用岩相学结合阴极发光和扫描电镜方法,较系统地研究了榴辉岩中锆石在岩石中的赋存状态、内部结构及表面特征。锆石主要产于石榴子石等变质矿物内,与主晶界面清晰,具有多晶面等变质锆石特有形貌特征,内部均匀或发育变质生长结构,从而说明它们是变质作用的产物。SHRIMP分析表明,锆石^(206)Pb/^(238)U年龄为335～424Ma,有放射性成因铅丢失现象,因此可以推断424±5Ma代表高压变质事件的最小年龄。结合已有的Sm-Nd全岩和内部等时线、冻蓝闪石^(40)Ar-^(39)Ar及单颗粒锆石U-Pb和^(207)Pb/^(206)Pb年龄资料综合分析,熊店榴辉岩的峰变质年龄应限于424～480Ma之间。这一研究进一步说明大别山存在加里东期榴辉岩。
The Xiongdian eclogite at Luoshan County, Henan Province, occurs in the Sujiahe tectonic melange in the western Dabie Mountains. Zircons from the rock occur in garnet and other metamorphic minerals with clear sharp boundaries and exhibit textures growing under metamorphic conditions. They are multifaceted under the scanning electron microscope, thus indicating their growth in a solid medium. SHRIMP analyses give 206Pb/238U ages ranging from 335 - 424 Ma for the zircons, showing a certain degree of radiogenic lead loss; so the age of 424±5 Ma reflects the minimum age of the metamorphic zircons. From the above data Combined with the previous Sm-Nd, 40Ar-39Ar,U-Pb and 207Pb/206Pb data, it is suggested that the peak metamorphism of the Xiongdian eclogite is between 424-480 Ma. The present study confirms that there do exist a Caledonian HP-UHP metamorphic event in the western part of the Dabie orogenic belt.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2000年第3期259-264,共6页
Acta Geologica Sinica
基金
原地质矿产部重大基础项目(编号9501102)
国土资源部同位素地质开放实验室
中国博士后基金项目
