江南造山带东段皖南地区印支事件地质表象

Geological Phenomena of Indosinian Event in Southern Anhui,Eastern Jiangnan Orogenic Belt

长期以来,由于缺乏最直接的年代学证据,江南造山带东段皖浙赣相邻区印支构造事件形成的构造变形并没有引起重视。通过1∶5万区域地质调查资料阅读和野外实地观察,阐述了皖南地区若干印支构造事件的相关证据。在安徽休宁流塘一带共识别出三期明显的构造变形形迹,其中第一期上三叠统与下三叠统之间的角度不整合是印支期(中三叠世)构造事件的响应;兰田残留向斜中发育的NE向断层形成于印支期,具有先走滑后滑覆的特点;东坑口石英斑岩(年龄为245.2 Ma)暗示印支运动初期皖南地区曾出现过局部拉张;三阳断裂中绢云母40Ar-39Ar年龄((230.5±2.3)Ma)表明晋宁期断裂受到印支运动的叠加。基于上述发现,初步探讨了皖南地区印支运动的演化规律,为深入了解皖南地区甚至皖浙赣相邻区印支期构造演化提供重要依据。

The Indosinian structural features in the adjacent regions of Anhui （Wan）, Zhejiang （Zhe） and Jiangxi （Gan） in eastern Jiangnan Orogen were largely ignored due to the lack of directly structural age data. Based on regional geological information at scale of 1 ： 50,000 and field observation on southern Anhui, this study found and concluded some new evidences of Indosinian tectonic events in southern Anhui. Three-period distinct structural features have been identified in Liutang area of Xiuning in Anhui, and among which the angular unconformity between the Upper Triassic and the Lower Triassic belongs to the Indosinian event. The NE-trending fault developed in Lantian relict synelinal basin was formed during Indosinian, which experienced a process from slipping to collapse. The age of Triassic Dongkengkou quartz porphyry is about 245.2 Ma, impl- ying that the Early Indosinian event had caused a partial extension. In addition, the age of sericites in Sanyang- fault is （230.5 ＋ 2. 3 ） Ma （ 40 Ar39 Ar）, indicating that the Jinningian fault had been affected by Indosinian movement. Upon these findings, vided important implications for Wan-Zhe-Gan adjacent areas. this study discussed the evolution process of Indosinian movement, and pro- understanding the Indosinian tectonic events of southern Anhui, even those of