摘要
华北陆台北缘近千公里的麻粒岩带不是同为太古宙的一个带，其西的晋蒙高级地体以含有孔兹岩系而有别于其东的冀东地体。若以中下地壳出露的孔兹岩系划界，其东、西两块地体的界限大致在赤城－阜平一线。本文只讨论了孔兹岩系时代问题。根据孔兹岩系①富含大理岩（太古缺大理岩）；②所含石墨为生物成因；③地球化学特征与显生宙的而不与太古宙的沉积岩相似；④与下伏太古宙麻粒岩套为两大构造层；⑤与冀东太古宙麻粒岩的ＰＴ轨迹不同；⑥仅有早元古代的同位素年龄；⑦区域地质构造讨论；⑧中元古代的不变质辉绿岩墙群所限定；⑨晋蒙地体不变质盖层为寒武、奥陶系，而不同于冀东地体为中元古的长城、蓟县系等，结论认为不但孔兹岩系的变质期为早元古代，而且原岩时代也为早元古代。
The E W trending granulite belt over one thousand kilometers long, located in the northern part of North China craton is not considered as the same Archean one.Taking the join line from Chicheng to Fuping as the boundary,Perhaps it can be divided into two segments. The western segment (Jin Meng terrain) with khondalite series is different from the eastern one (Jidong terrain).There has been a debate on the age of the khondalite in Jin Meng terrain,Archean vs Early Proterozoic. In this paper, not only metamorphic age but also protolith age of the khondalite are considered as Early Proterozoic, based on the following disscusions: 1) numerous marble in the khondalite is not one of the characteristics of the Archean terrain; 2) graphite of the Khondalite is derived from organisms,not from the mantle; 3) geochemical ratios of the khondalite are similar to those of Phanerozoic craton terrigenous sediments, not to those of Archean;4) the contact between the khondalite and the underlying Archean granulite complex is always a high strain zone, indicating not successive; 5) the clockwise P T trajectory of the khondalite differs from that of the granulite that contains both clockwise and counterclockwise ones; 6) the khondalite only yields zircon ages of～1800Ma,but the granulite complex yields zircon ages both of 1800Ma± and 2500Ma±; 7) evidence of regional geology;8) the unmetamorphosed cover in Archean Jidong terrain is Middle Proterozoic Changcheng and Jixian Systems, whereas the cover in Jin Meng terrain is Cambrian system;and 9) unmetamorphosed diabase dyke swarm with NWN trend yields K Ar ages of 1200～1400Ma.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
1997年第3期289-302,共14页
Acta Petrologica Sinica
基金
国家自然科学基金
关键词
地体
孔兹岩
时代
变质岩系
Jin Meng (Shanxi Nei Mongol) high grade terrain
Khondalite
Age
