江西冷水坑矿区构造-岩浆活动的年代学约束

Geochronology of igneous rocks and nappe structures in Lengshuikeng deposit, Jiangxi Province, China

江西省冷水坑矿区火成岩-构造演化一直缺少系统的年代学制约。作者运用LA-ICP-MS锆石U-Pb和40Ar/39Ar测年技术,对冷水坑矿区两套火山岩地层(打鼓顶组和鹅湖岭组)、含矿花岗斑岩和主推覆断层F2进行了年代学测试,结果表明,打鼓顶组流纹质含角砾熔结凝灰岩形成于160.8±1.9Ma,鹅湖岭组含角砾熔结凝灰岩则具有间歇性和多期喷发特点,其最初活动时间为159Ma,而主体形成于146.6±2.2Ma;矿区含矿花岗斑岩与打鼓顶组、鹅湖岭组几乎同期形成,年龄介于163.6±2.1Ma～154.3±3.0Ma之间;研究区构造活动起始时间不晚于加里东期,推覆断层F2中保留有40Ar/39Ar年龄为398.5±2.6Ma的构造活动痕迹,中生代重新复活,导致震旦系叠覆于鹅湖岭组之上,年龄晚于146.6Ma,可能对含矿斑岩体起破坏作用。

Abstract LA-ICP-MS and 40Ar/39 Ar isotopic analysis were carried out to constrain the ages of volcanic rock （Daguding Formation and Ehuling Formation）, granite porphyry and nappe structure in the Lengshuikeng deposit, Jiangxi Province. The Daguding Formation was formed during the Late Jurassic with U-Pb age of 160. 8±1.9Ma. The Ehuling Formation was formed in an intermittent and multi- period magmatic activity, which began at 159Ma and reached its climax at 146. 6 ± 2. 2Ma. The zircons from granite porphyry in Lengshuikeng yield U-Pb ages ranging from 163.6± 2. 1 to 154. 3 ± 3. OMa. The nappe structure F2 firstly activated during Caledonian with a 4~Ar/39Ar age of 398.5± 2. 6Ma, and reactivated after 146. 6Ma, leading to the superimposition of Sinian System upon Ehuling Formation and broken the granite porphyry in Lengshuikeng deposit.