宁芜盆地凹山铁矿含矿玢岩LA-ICP-MS锆石U-Pb定年及其地质意义

凹山铁矿是宁芜火山盆地内重要的玢岩矿床之一.为进一步厘定该矿床的成矿年龄,分析其成矿动力学背景,本文对凹山铁矿含矿辉石闪长玢岩和磁铁矿样品进行了详细的稀土元素地球化学分析,并对辉石闪长玢岩样品进行了LA-ICP-MS锆石U-Pb年龄测定.测年结果显示凹山铁矿成矿母岩的形成时代为127.6±4.4 Ma,属早白垩世,该年龄可代表凹山铁矿床的成矿年龄.成矿岩浆源自于地幔或下地壳玄武岩；盆地岩石圈减薄诱发地幔成矿物质进入地壳,成矿时代对应岩石圈减薄的高峰期.

Zircon U-Pb dating of the ore-bearing porphyrites and its geological significance for the Washan iron deposit,Nanjing-Wuhu Basin

The Washan iron deposit is one of the most important porphyrite deposits in the Nanjing-Wuhu Basin. In order to further confine the mineralization age and analyze the geodynamic settings of the Washan iron deposit, this paper analyzed the REE geochemistry of the rocks related to ore-bearing pyroxene dioritic porphyrites and magnetites in this deposit, and the age of the ore-bearing pyroxene dioritic porphyrites was obtained through LA-ICP-MS precise determination of the zircon U-Pb age. The dating result indicated that the ore-forming rocks of the Washan iron deposit yielded an age of 127.64-4.4Ma, belonging to early Cretaceous and representing the mineralization age of the Washan iron deposit. It is considered that the ore-forming magmas were originated from the mantle or lower crust basalt. The lithospheric thinning could be induced by the ore-forming materials of the mantle coming to the crust, the ore-forming age were the peak of the lithospheric thinning.