碳酸盐岩中碳酸盐矿物稀土元素分析方法进展

Progress of Analytical Methods of Rare Earth Elements of Carbonate Minerals in Carbonate Rocks

碳酸盐岩中测定碳酸盐矿物的稀土元素主要有酸溶-ICP-MS和LA-ICP-MS方法。酸溶-ICP-MS方法用盐酸、硝酸溶解碳酸盐矿物,但也能溶解部分非碳酸盐矿物,而影响分析结果;用醋酸溶样可避免非碳酸盐矿物的干扰,但可能没有溶样完全,同样影响分析结果。LA-ICP-MS是应用激光对碳酸盐矿物进行原位剥蚀,将蒸发物导入ICP-MS进行分析,对不含粘土等的碳酸盐矿物最有效,由于激光束光斑较大,且碳酸盐岩中普遍含有微小的粘土矿物,可能也存在不确定性。总体而言,酸溶-ICP-MS和LA-ICP-MS获得的稀土元素页岩标准化配分模式及主要参数相似,均可用于沉积环境的示踪。

Solution-ICP-MS and LA-ICP-MS are the most common analytical methods for measuring rare earth elements in carbonate minerals of carbonate rocks.HCl and HNO3 not only can completely dissolve carbonate minerals in carbonate rocks but also dissolve some other minerals,and such will disturb the analytical results.CH3COOH,on the other hand,can avoid interferences from non-carbonate minerals,but probably cannot completely dissolve carbonate minerals in carbonate rocks,and such will also cause bias from the true result.LA-ICP-MS,which uses laser beam to ablate carbonate minerals and directly analyze rare earth elements contents in the evaporation,is an effective method for analyzing carbonate mineral crystals in carbonate rocks.But this method may also be questionable since the diameter of the laser beam may be too large to avoid tiny clay minerals in carbonate minerals.In summary,the results obtained by solution-ICP-MS and LA-ICP-MS on the shale-normalized REE patterns and their main parameters of carbonate minerals in carbonate rocks are comparable,and both methods can be used to trace the sedimentary environment.