贵州威宁鱼坝稀土含矿岩系的锆石U-Pb年龄

Zircon U-Pb Age of Yuba Rare Earth-bearing Rock Series in Weining,Guizhou

黔西北地区晚二叠世稀土矿产于峨眉山玄武岩与上伏宣威组假整合面附近,在威宁地区稀土矿分为上、下两层,下含矿层为浅灰白色高岭石粘土岩,上含矿层为浅灰色高岭石粘土岩与铝质高岭石粘土岩,含矿岩系厚度在区域上变化较大,在威宁鱼坝剖面含矿岩系完整且厚度较大。在含矿岩系底部凝灰质粘土岩中取样测得锆石U-Pb平均年龄为254.11 Ma±0.98 Ma,含矿岩系顶部熔结凝灰岩锆石U-Pb年龄为252.0 Ma±0.82 Ma(谐和年龄)和251.9 Ma±1.86 Ma(平均年龄)。证实黔西北晚二叠世稀土含矿岩系下矿层产于峨眉山玄武岩第三段上部、上矿层产于宣威组下段,整个稀土含矿岩系形成时间约为2 Ma。

In the northwest Guizhou,the rare earth deposit in late Permian is found near the disconformity surface of Emeishan basalt and upper Xuanwei formation,the rare earth deposit in Weining area is divided into upper and lower two layers,the lower layer is light gray white Kaolinite clay rock,the upper layer is light gray kaolinite clay rock and aluminous kaolinite clay rock,the thickness of the ore-bearing rock series has big change in this area.The ore-beaing rock series is complete and the thickness is big in the profile of Yuba,Weining.It taken samples in tuffaceous clay rock which in the bottom of ore-bearing rock series,the tested average zircon U-Pb age is 254.11 Ma±0.98 Ma,the zircon U-Pb age of welded tuff in the top ore-bearing rock series is 252.0 Ma±0.82 Ma(concordant age)和251.9 Ma±1.86 Ma(average age).it’s proved that the lower layer of rare earth ore-bearing rock series of late Permian in northwest Guizhou occur in the upper 3 rd section of Emeishan basalt,the upper layer occur in the lower Xuanwei formation,the formation age of the whole rare earth ore-bearing rock series is about 2 Ma,