郯庐断裂(安徽段)两侧肥东群与霍邱群特征性岩石对比研究

Comparison study of typical rocks separated from Feidong Group and Huoqiu Group in the Tan-Lu Fault zone(Anhui segment)

郯庐断裂带（安徽段）内部物质组成十分复杂,现有研究认为郯庐内部以扬子板块为主体,对于是否存在西侧华北板块物质混入尚不清楚。为此本文选取了3个特征性样品展开了细致的岩相学研究、温压估算以及锆石U-Pb定年分析,分别为：霍邱群样品WS069-1（磁铁石榴角闪岩）以及样品WS070-1（石榴黑云母片岩）;肥东群样品TF003-1（石榴黑云母片岩）。研究发现,霍邱群磁铁石榴角闪岩与肥东群磁铁石榴角闪岩的矿物组合及矿物主量元素特征基本一致。针对霍邱群石榴黑云母片岩与肥东群石榴黑云母片岩的峰期变质条件评价也相互匹配。本文在霍邱群仅发现了-3.2Ga、3.0Ga、2.80Ga、2.74Ga等四组反映源区结晶时代的碎屑锆石年龄,但结合前人对霍邱群和五河群的研究可以认为霍邱群的峰期变质年龄应为2.44Ga,这与肥东群磁铁石榴角闪岩和石榴黑云母片岩的峰期变质年龄2.47-2.41Ga吻合。因此肥东群和霍邱群相同特征性岩石磁铁石榴角闪岩从岩相学、变质P-T条件及变质时代等方面皆具可比性,从而推测肥东群磁铁石榴角闪岩和石榴黑云母片岩构造透镜体应为因郯庐断裂左旋走滑作用而卷入肥东群中的霍邱群岩片。

At present,the Tan-Lu Fault Zone（ Anhui segment） is considered to be entirely made up by internal material of Yangtze Plate. In order to verify whether a small amount of material of the Tan-Lu Fault zone（ Anhui segment） is derived from the North China Craton,This study have selected 3 samples,TF003-1（ garnet biotite schist） from Feidong Group,WS069-1（ magnet garnet amphibole） and WS070-1（ garnet biotite schist） from Huoqiu Group,to conducting the study on petrographic,in situ zircon U-Pb dating and P-T condition estimation. This study showed that the mineral assemblages and the major element characteristics of WS069-1（ magnet garnet amphibole） from Huoqiu Group are similar with Feidong Group. And the estimation results of P-T conditions of sample WS070-1 from Huoqiu Group also is accord with the Sample TF003-1 from the Feidong Group. This study obtained four groups ages of detrital zircon（ 3. 2Ga,3. 0Ga,2. 80 Ga,2. 74Ga）,which represented the forming times of the source. Combined with the study of Huoqiu Group and Wuhe Group,the study supposed the peak metamorphism time of Huoqiu Group should be at 2. 44 Ga,matched to the peak metamorphism time（ 2. 47 - 2. 41Ga） of the magnet garnet amphibole and garnet biotite schist from Feidong Group. Thus the magnet garnet amphibole from Feidong Group could concordance with the Huoqiu Group about the mineral assemblage,metamorphism characteristics and its forming time. So the magnet garnet amphibole form Feidong Group should belong to the Huoqiu Group had suffered the sinistral strike-slip of Tan-Lu Fault zone.