安徽北部郯庐断裂两侧基底岩石年龄及对郯庐断裂初始开启时间的限定  

The initial time of the Tan-Lu wrench fault: In the view of geochronological data of the basement rocks, northern Anhui Province

作　　者：聂峰[1] 石永红[1] 张忠宝[1] 王娟[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：《科学通报》2015年第24期2315-2326,1-7,共12页Chinese Science Bulletin

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

摘　　要：华北克拉通东南缘的蚌埠隆起结晶基底的初始陆壳形成时限及其演化过程的标定,以及郯庐断裂的初始启动时间一直为人们所关注,存在较多的争议.为此,本文对安徽北部郯庐断裂两侧的蚌埠隆起和池河魏岗山的花岗片麻岩、斜长角闪岩展开了细致的锆石U-Pb定年分析,估算了变质作用的温度与压力条件.分析样品总计4个,其中样品WS055-1（钠长花岗片麻岩）、WS055-3（斜长角闪岩）和WS021-1（花岗片麻岩）来自蚌埠隆起区,普遍经历了中-高级变质作用;样品FD019-1（花岗片麻岩）来自张八岭群西侧的池河地区.锆石U-Pb定年显示,样品WS021-1中17颗岩浆锆石的加权平均年龄为2886±28 Ma,代表了初始陆壳的形成时限;样品WS055-1中锆石均为变质锆石,记录了3组变质年龄2440±28 Ma（21颗）,2163±55 Ma（1颗）和1944±89 Ma（1颗）;样品WS055-3仅具有1组变质锆石年龄2481±18 Ma（23颗）.样品FD019-1中的锆石具有明显的核、幔和边结构,分别显示了3组年龄：271～667 Ma（10个点）、228±3 Ma（17个点）和211±2 Ma（23个点）.结合前人的研究资料分析,可以确定前3个样品明显归属于华北克拉通,样品FD019-1源于扬子板块上的大别造山带,据此可以限定郯庐断裂（安徽段）西界的主断裂为朱顶-石门山断裂,并确证了郯庐断裂的初始启动时间应于晚侏罗世.另外,对蚌埠隆起的3个样品的锆石年龄研究,不仅揭示了蚌埠隆起目前最为古老的、中太古代晚期的初始陆壳（2.89 Ga）的存在,同时也反映了该隆起所记录的地质过程与华北克拉通的演化具有很好的统一性.As the most conspicuous structure of Eastern China, the Tan-Lu fault arouses the most controversies on its initial time of the sinistral strike-slip movement. In the northern Anhui Province, the Bengbu uplift, which consists of basement rocks of the North China Craton, is situated to the west of the Tan-Lu fault, and the Weigang granitic gneiss is located to the east. Three samples were analyzed by in situ zircon U-Pb dating and P-T calculation from the Bengbu uplift： WS055-1（albite granitic gneiss）, WS055-3（amphibolite） and WS021-1（granitic gneiss）. All of them have experienced medium-high grade metamorphism with the P-T condition about 0.53±0.01 GPa and 742±5°C. LA-ICP-MS U-Pb zircon dating results suggest a main crystallization age at Late Mesoarchean to Paleoproterozoic. New geochronological data from zircons of the basement rocks can be preliminarily divided into four groups around（1） 2886±28 Ma,（2） 22481±18 Ma to 2440±28 Ma,（3） 2163±55 Ma, and（4） 1944±89 Ma, respectively. The oldest age indicates the presence of the oldest juvenile crustal materials at the late Mesoarchean（2.89 Ga）. These age groups correspond well to the tectonic events of the North China Craton. One granitic gneiss（FD019-1） was collected from the west of the Zhangbaling group. Zircons of the Sample FD019-1 have structure of core-mantle-rim, which yield ages at 667–271 Ma for core, 228±3 Ma for mantle, and 211±2 Ma for rim, respectively. According to the regional tectonic framework, FD019-1 can be considered as derived from the Qinling-Dabie-Sulu orogenic belt along the northern margin of the Yangtze Block. Hence, as the boundary between the North China Craton and the Yangtze Block, the western boundary of the Tan-Lu fault in northern Anhui Province is the Zhuding-Shimenshan fault. Combined with previous work, the initial time of the Tan-Lu wrench fault is also discussed.

关 键 词：郯庐断裂西界 初始启动时间 蚌埠隆起 初始地壳 

分 类 号：P548[天文地球—构造地质学]