肥东群变质岩石学、年代学分析及变形时限的探讨  

Analysis of metamorphic petrology and geochronology for Feidong Group and its discussion on the deformation period

作　　者：石永红[1] 王娟[1] 张忠宝[1] 赵俊先[1] 聂峰[1] 曹晟[1] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009

出　　处：《岩石学报》2016年第4期1067-1086,共20页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41272073);国家科技重大专项(2011ZX05008-001-31)联合资助

摘　　要：长期以来,对于承载郯庐断裂全演化过程的肥东群的变质岩石学和年代学的研究一直较为薄弱,诸多的研究主要关注于构造地质学、地球化学及变形时限方面。本文通过对肥东群不同类型岩石的岩相学、热力学和年代学研究,详实地探究了肥东群的变质条件和时限,并充分讨论了肥东群的两期韧性变形时限。研究显示,肥东群普遍经历了角闪岩相的变质,温压条件大致为T=550-650℃和P=0.5-0.9GPa。同时,依据5个二长花岗片麻岩、1个变形花岗岩（167.2±4.6Ma）和1个花岗闪长斑岩岩脉的年龄（130±5Ma）的锆石年龄和前人的年龄数据分析,认为早期的变形以一组倾向南东的面理和线理为代表,其形成的时限可能在133-167Ma时间段。而晚期的变形以一组宽约3-5m NE向的陡倾糜棱岩带为特征,其变形时限可能在122-133Ma。For a long time,the investigation on the petrology and geochronology for Feidong Group（ FDG）,which documents the evolution of the Tan-Lu fault,is very limited. A lot of research focused on the structure,geochemistry and deformation geochronology for the FDG. In this contribution,according to the study of petrology,thermodynamics and geochronology for various types of rocks of the FDG,the metamorphic conditions and date of the FDG have been analyzed in detail,and two deformed periods have been defined for the FDG. The study reveals that the FDG had underwent amphibole metamorphism T = 550 - 650℃ and P = 0. 5 - 0. 9GPa. By the analysis of LA-ICP-MS,five two-feldspar granitic gneisses from the FDG give complex age range from 413 Ma to 2498 Ma with various origin. Meanwhile,the zircon U-Pb ages of 167. 2 ± 4. 6Ma from the deformed granite and 130 ± 5Ma from prophyro grainitic diorite have been confirmed. Combined structural investigation,dating with previous study,two deformation period for the FDG has been distinguished：（ 1） the early deformation with a SE dipping foliation and lineation has been conjectured in the 133 - 167 Ma,and（ 2）the later deformation cropping out as a 3 - 5m width of the NE-direction steep mylonitic zone has been defined in the 122 - 133 Ma.

关 键 词：郯庐断裂 肥东群 P-T评价 变形时限 

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