摘要
佛子岭群为北淮阳变质单元的重要组成部分,其位于大别碰撞造山带最北缘,处于扬子和华北板块的结合部位,构造位置极为关键。长期以来,佛子岭群一直被视为扬子板块北缘沉积产物,并以加积楔形式产出。然而,随着年代学和构造地质学的研究的深入,对其构造归属和形成动力学机制产生了差异性认识,究其原因主要是对佛子岭群变质属性缺乏准确的判定所致。为此,本研究对佛子岭群展开了详细的野外观测和区域变质岩石学研究,以及岩相学、热力学和年代学分析。研究表明佛子岭群构成较为复杂,主体由细粒的云母石英片岩、石英云母片岩和石榴云母片岩构成。主期变质PT条件评价显示,其温压范围为610~620℃和0. 9~1. 0GPa,普遍经历了中-高压角闪岩相变质,并非为"浅"变质产物,并卷入了较深层次的俯冲-折返过程。锆石U-Pb年代学研究表明,佛子岭群年龄跨度较大,范围为3101±48Ma^413±9Ma,可分为5组年龄,年龄峰值分别为2537Ma、1567Ma、940Ma、749Ma和440Ma,显示了华北和扬子板块混合物源特征,最年轻的年龄峰值暗示其形成于早古生代晚期。
The Foziling Group( FZG) is an important component of the Beihuaiyang metamorphic unit in the northernmost margin of the Dabie collisional orogenic belt,and is located in the crucial position between the Yangtze and North China plates. For a long time,the FZG has been regarded as the sedimentary product of the northern margin of the Yangtze Plate as an accretionary wedge. However,the disputes on the tectonic attribute and dynamic formation mechanism of the FZG are incessancy due to the different viewpoints from studies of its geochronology and structural geology. The reason for this situation lies on the lack of the accurate appraise for the metamorphic attribution of the FZG. In this study,detailed fieldworks and regional metamorphic investigations on the FZG,together with abundant analysis of its metamorphic petrology,thermodynamic characteristics and geochronological dating have been carried out.The result indicates that the FZG is mainly lithologically composed of fine-grained mica-quartz schists,quartz-mica schists and garnetmica schists. The estimates of the main metamorphic P-T conditions of the FZG show that it has metamorphosed in a middle-high pressure amphibolite facies with a P-T range of 610 ~ 620℃ and 0. 9 ~ 1. 0 GPa,respectively,and it should not be the‘lower’-grade metamorphic unit. which demonstrates that the FZG might be involved into the process of subduction and exhumation in the deeper level. On the basis of zircon U-Pb dating,a large age range of 3101 ± 48 Ma ~ 413 ± 9 Ma has been gained for the FZG,which can be divided into 5 groups with the peak age values of 2537 Ma,1567 Ma,940 Ma,749 Ma and 440 Ma,respectively. These peak ages imply that the FZG has a mixture source from North China and Yangtze plates,and the youngest peak age suggests that the FZG has been formed in late Early Paleozoic.
作者
赵俊先
石永红
唐虎
李秋立
侯振辉
周甜
ZHAO JunXian;SHI YongHong;TANG Hu;LI QiuLi;HOU ZhenHui;ZHOU Tian(College of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China;Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China;University of Science and Technology of China, Hefei 230009, China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第7期2219-2236,共18页
Acta Petrologica Sinica
基金
国家自然科学基金项目(4161016)资助
