宁芜地区凹山和太山铁矿床中磷灰石Sr同位素特征及意义

Sr Isotope of Apatites from the Washan and Taishan Iron Deposits in the Nanjing-Wuhu Area and Its Implications

太山铁(磷)矿床和凹山铁矿床中磷灰石^(87)Sr/^(86)Sr值介于0.7071～0.7073,同辉长闪长(玢)岩、龙王山组粗安岩和大王山组安山岩Sr同位素初始比(0.7040～0.7077)基本接近。说明磷灰石由壳幔同熔型中基性岩浆不混溶和分异作用所形成,而磷灰石中熔融包裹体和气液二相包裹体共存表明,磷灰石由矿浆—热液过渡性流体充填、交代作用所形成。

Two types of inclusions are recognized in the apatites from the Washan and Taishan iron deposits, melt inclusions and gas-liquid inclusions. The geology and geochemistry of the Nanjing-Wuhu iron deposits indicate that the apatites from the Washan and Taishan iron deposits are formed by the filling and metasomatism of magma-hydrothermal transitional fluids. The volcanic and subvolcanic rocks yield initial 87Sr/86Sr values ranging from 0. 7040 to 0. 7077. The apatites have a narrow range of 87Sr/86Sr values from 0. 7071 to 0. 7073, similar to those of the volcanic and subvolcanic rocks, indicating that the apatites are formed by liquid immiscibility and differentiation of intermediate and basic magmas. These intermediate and basic magmas have been interpreted to have originated from the mixing of juvenile mantle and old crustal materials.