华北地块南缘中段中生代花岗质岩石的~(40)Ar-~(39)Ar年代学研究

对华北地块南缘4个中生代花岗质岩体中的角闪石和黑云母进行了40Ar-39Ar定年研究。结果表明,陕西黑山村岩体黑云母花岗闪长岩中黑云母的40Ar-39Ar坪年龄为126. 6±0. 3Ma,河南马家湾岩体细粒黑云母花岗闪长岩中黑云母的40Ar-39Ar坪年龄为126. 6±0. 2Ma,河南洛宁南八百坡岩体黑云母二长花岗岩中角闪石的40Ar-39Ar坪年龄为128. 3±0. 3Ma,山西蚕坊岩体花岗闪长岩中角闪石的40Ar-39Ar坪年龄为129. 2±0. 2Ma。上述结果显示华北地块南缘中生代的岩浆活动主要发生在早白垩世。该期岩浆的产生应与中国东部早白垩世的伸展环境相联系。

CHRONOLOGY OF MESOZOIC GRANITOIDS IN THE SOUTHERN MARGIN OF THE NORTH CHINA BLOCK: EVIDENCE FROM 40Ar- 39Ar DATING OF HORNBLENDE AND BIOTITE

The ()~(40)Ar-~(39)Ar dating of hornblende and biotite from four granitoid intrusives in the southern margin of the North China Block (NCB) was made in the paper. The results indicate that the ()~(40)Ar-~(39)Ar plateau ages of biotites in Bi-granodiorites from Heishancun intrusive of Shanxi province and from Majiawan intrusive of Henan province are 126.61±0.25Ma and 126.64±0.21 Ma, respectively, and that the ()~(40)Ar-~(39)Ar plateau ages of hornblendes in Bi-monzogranite from Babaipo of Henan province and in granodiorite from Canfang of Shanxi province are 128.27±(0.29) Ma and 129.17±0.20 Ma, respectively. It is suggested that the Mesozoic magmatism in the southern margin of the NCB should mainly take place in Early Cretaceous, and the early Cretaceous magmatism be related with the extensional environment in eastern China.