山西义兴寨岩体和车厂-北台岩体的变质程度及变质作用K-Ar定年  

Metamorphic pressure-temperature conditions and K-Ar geochronology of the Yixingzhai and Chechang-Beitai plutons, Shanxi Province

作　　者：孟洁[1] 彭涛[1] 张继军 吴春明[1] 

机构地区：[1]中国科学院大学地球科学学院,北京100049 [2]陕西省地质调查中心,陕西西安710068

出　　处：《岩石矿物学杂志》2015年第6期991-1004,共14页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金资助项目(41225007)

摘　　要：义兴寨岩体和车厂-北台岩体位于华北克拉通中部造山带中段,均被变质辉绿岩墙穿切,分别出露于山西省恒山南麓和五台山北麓。义兴寨岩体出露的岩石类型呈现渐变过渡的特征,主要为花岗闪长片麻岩、石英闪长片麻岩和闪长片麻岩;变质高峰期温压条件达到710~760℃/0.65~0.75 GPa,记录的降温降压条件为560~690℃/0.46GPa;变质高峰期为高角闪岩相,属于中压变质相系;变质角闪石K-Ar定年表明义兴寨岩体变质时代为1.84~1.82Ga。车厂-北台岩体主要由二云母花岗片麻岩构成,变质高峰期温压条件达到550~690℃/0.92~1.14 GPa;变质高峰期为中角闪岩相,属于中压变质相系顶部;变质黑云母K-Ar定年表明车厂-北台岩体变质时代为1.80 Ga。这两个岩体变质时代与华北克拉通中部造山带普遍记录的1.96~1.80 Ga之间的变质事件一致,说明它们同样卷入了华北中部造山带早元古代末期的造山过程。Exposed in the middle segment of the Palaeoproterozoic Trans-North China Orogen, the Yixingzhai pluton on the southern slope of the Hengshan Mountain and the Chechang-Beitai pluton on the northern slope of the Wutai Mountain experienced amphibolite facies metamorphism and were cut by metamorphosed diabase dykes The Yixingzhai pluton consists of transitional granodioritic gneiss, quartz dioritic gneiss and dioritic gneiss. Its metamorphic peak p-T conditions are estimated to be of 710-760℃/0.65--0.75 GPa and the retro- grade metamorphism occurred at 560--690℃/--0.46 GPa. The metamorphic peak is ascribed to typical middle p-T facies series. K-At dating of metamorphic hornblende suggests that the metamorphic peak occurred at about 1.84--1.82 Ga. The Chechang-Beitai pIuton consists of biotite-muscovite granitic gneiss and the metamorphic peak p-T conditions are estimated to be of 550--690℃/0.92--1.14 GPa, belonging to the top middle p/T fa- cies seies. K-Ar dating of metamorphic biotite implies that the metamorphic peak occurred at about 1.80 Ga. Geochronologic research indicates that these two plutons were involved in the late Palaeoproterozoic orogenic event of Trans-North China Orogen deciphered at about 1.96--1.80 Ca.

关 键 词：义兴寨岩体 车厂-北台岩体 温度-压力条件 K-Ar定年 华北中部造山带 

分 类 号：P588.345[天文地球—岩石学] P597.3[天文地球—地质学]