重庆铜梁地区富锂绿豆岩地球化学特征

Geochemical characteristics of lithium-rich mung bean rocks in Tongliang County, Chongqing

近年来美国和智利等国家新发现了大量赋存在粘土岩中的锂资源,该类锂资源主要是由火山灰蚀变而成。火山灰沉积水解形成的绿豆岩,广泛分布于我国西南地区,其是否存在锂的富集现象值得研究。笔者对重庆铜梁地区绿豆岩开展了调查研究,通过X射线荧光光谱仪和等离子质谱仪分析,发现绿豆岩中钾的平均含量为8.77%,锂的含量可达663×10^(-6),相当于0.14%的Li_2O含量,远高于固体、露采盐类矿的边界品位0.06%;稀土元素总量可以达到500×10^(-6),接近离子吸附型矿的边界品位。X射线衍射分析显示绿豆岩主要含有石英、长石和粘土矿物,其中粘土的主要成分为伊蒙混层和少量伊利石。伊蒙混层含量占比高的样品较占比低的样品Li的含量偏高。结合粘土及锂的物理化学特性,推断绿豆岩中的Li呈离子形态被粘土矿物吸附。如果这些锂资源能够被综合利用,势必将会产生巨大的经济效益。

Abundant lithium-rich clay rocks are explored in the USA, Chili and some other countries. This kind of clay rocks is mainly altered from volcanic ash. The mung bean rocks are hydrolyzed from the sedimentary volcanic ash and are widely distributed in southwest China. To find out whether the mung bean rocks are rich in lithium, the authors studied the mung bean rocks in Tongliang, Chongqing. The test of X-ray fluorescence spectrometer and ICP-MASS shows that the lithium is relatively rich. The content of lithium is 663 × 10^（-6）(Li_2O 0. 14%） much higher than the cutoff grade of solid and open mining salt mine(0. 06%）. The total amount of rare earth can reach 500× 10^（-6）, close to the cutoff grade of ion-absorbing type rare earth ore. The result of X-ray diffraction analysis shows that the major ingredients include quartz, feldspar and clay minerals comprising illite and montmorillonite mixed layer and a little illite. The Li concentration of two samples whose clay minerals are pure illite and montmorillonite mixed layer is higher than that of the other samples. Combined with the characteristics of clay rocks and lithium,the authors infer that the lithium exist in ion state and is absorbed by the clay rocks. If the lithium can be comprehensively used, the value of the mung bean rocks will be enhanced greatly.