摘要
Monazites from low-pressure pelitic granulite of the Jingshan Group in the Jiaobei terrane were dated by the electron microprobe method. Three stages of metamor- phic age at 1720±15 Ma, 1687±16 Ma and 1568±15 Ma were yielded by constructing age mapping for zoned mona- zites and PbO-ThO2* isochron diagram for unzoned mona- zites, respectively. The first age was interpreted as the age of an early amphibolite-facies metamorphism, the second age as the peak granulite-facies, and the last age as uplifting of the granulite unit. These ages are the first geochronologic data for the low-pressure pelitic granulites in the Jingshan Group, and thus are of important significance when discussing the tectono-metamorphic evolution of the Jiaobei terrane.
Monazites from low-pressure pelitic granulite of the Jingshan Group In theJiaobei terrene were dated by the electron microprobe method. Three stages of metamor-phic age at1720 + 15 Ma, 1687 + 16 Ma and 1568 + 15 Ma were yielded by constructing age mapping for zonedmonazites and PbO-ThO_2 isochron diagram for unzoned monazites, respectively. The first age wasinterpreted as the age of an early amphibolite-facles metamorphism, the second age as the peakgranulite-facies, and the last age as uplifting of the granulite unit. These ages are the firstgeochronologie data for the low-pressure pelitic granulites in the Jingshan Group, and thus are ofimportant significance when discussing the tectono-metamorphic evolution of the Jiaobei terrane.
基金
This work was supported by the National Natural Science Foundation of China(Grant Nos.40402008,40372032 and 40420120135)
TRAPOYT of MOE of China
China Postdoctoral Science Foundation.
关键词
电子微探针
独居石
泥质岩
麻粒岩
变质作用
low pressure
pelitic granulite
electron microprobe
rnonazite Th-Pb dating
multi-stage metamorphism
