摘要
根据近年来积累的文献资料及研究讨论指出:①大别造山带镁铁质—超镁铁质岩石可分成两大类,一类以任家湾、童家冲、祝家铺、道士冲、青山、沙河等辉石辉长岩类为代表,它们具有相同的特征和成岩年龄,可能与华北、华南地块聚敛碰撞产生的岛弧或大陆岩浆岩有关;另一类以铙钹寨、大化坪、碧溪岭和毛屋岩体为代表,虽然它们的成岩年龄均在前寒武纪,但却有着不同的成岩时代和成岩环境。②大别造山带榴辉岩等多属异地来源,具有不同的成岩年龄和复杂的原岩特点,它们是在变质杂岩的主体形成期(197～246Ma)混杂在一起的。③从榴辉岩等超高压岩石俯冲深度的估算方法观之,“成岩深度的构造校正测算”法更为合理,吕古贤等(1998)经构造校正测算获得了大别造山带柯石英榴辉岩的形成深度为32.05～32.11km,并提出该柯石英榴辉岩是在这一地壳深处(或稍深一些)受强烈构造作用而形成的,这一认识有可能为大别造山带的构造格局和演化历史的研究开辟新的途径和方法。
On the bases of recent researches and recent references, this paper mainly discusses the origin and evolution of mafic-ultramafic rocks and eclogites occurring in high pressure-ultrahigh pressure metamorphic belt, Dabie orogen. Systematic studies of petrology and geochemistry indicate that the mafic-ultramafic rocks in this region can be divided into two types. The mafic-ultra-mafkites of the first type, with similar geological characteristics and Sm-Nd age, are represented by Zhujiapu, Renjiawan and Tongjiachong gabbro intrusions in the northern Dabie erogenic belt, which are possibly associated with basaltic magmas from the island arc or continental mantle e-volved from the collision between the North China and Yangtze blocks. On the contrary, those of the second type with different rock-forming ages and environments are almost of the Precam-brian, derived from either continental mantle slices such as Naobozhai harzburgites or the differentiation of basaltic magmas in layered intrusions such as the Maowu and Bixiling peridotites. E-clogites in the Dabie HP-UHP metamorphic belt are not dominantly originated from their country rocks but produced from complicated protoliths with various isotopic ages. However, the fact that their metamorphic ages are concentrated in the Indosinian (197~246 Ma) suggests that all these eclogites experienced the same tectonic event of subduction-collision between the North China and Yangtze blocks. The evaluated formation depths (32. 05 - 32. 11 km) of coesite-bearing eclogites presented by Lu et al. (1998), we believe, are more reasonable than previous data of over 100 km in interpreting the exhumation of HP-UHP metamorphic rocks.
出处
《地质论评》
CAS
CSCD
北大核心
1999年第6期584-595,共12页
Geological Review
基金
国家自然科学基金(编号:49794043)
国土资源部壳幔开放重点实验室资助
关键词
超镁铁质岩石
成岩年龄
榴辉岩
镁铁质岩
造山带
mafic-ultramafic rocks
eclogites
HP-UHP metamorphism
protoliths,- rock-forming ages
exhumation
Dabie orogenic belt
