中国软玉的稀土元素地球化学特征及影响因素研究

Study on Geochemical Characteristics and Influencing Factors of Rare Earth Elements in Chinese Nephrite

为研究中国软玉的稀土元素地球化学特征及影响因素,对中国主要产地软玉进行了稀土元素测定,结合前人的研究数据,从轻稀土、中稀土和重稀土分异程度的差异,说明不同产地软玉稀土元素的分配模式特征及差异;并与侵入岩和围岩的稀土元素分配模式进行对比,解释影响软玉稀土元素含量及分配特征的主要因素。结果表明:不同产地软玉的稀土总量ΣREE为1.78～48.19μg/g(均值为15.14μg/g),LREE/HREE为1.69～12.58(均值为7.46)。球粒陨石标准化分配曲线由明显右倾至较为平坦,稀土元素浓度标准归一化的单元素比值(La/Sm)_N、(Sm/Ho)_N和(Gd/Lu)_N出现明显区别,元素异常系数δ_(Eu)和δ_(Ce)由明显负异常至正异常。研究表明,不同产地软玉的轻稀土、中稀土和重稀土分异程度并不相同,具有产地特征。热液的pH值、围岩、成矿环境的氧逸度是影响软玉稀土元素分配模式的主要因素。

In order to study the geochemical characteristics and influencing factors of rare earth elements in Chinese nephrite,the rare earth elements of nephrite from main producing areas in China were determined.Combined with previous research data, the differences in the degree of differentiation of light rare earth elements, medium rare earth elements and heavy rare earth elements in nephrite from different producing areas showed the distribution pattern characteristics and differences of rare earth elements in nephrite from different producing areas.The distribution patterns of rare earth elements in intrusive rocks and surrounding rocks were compared to explain the main factors influencing the content and distribution characteristics of rare earth elements in nephrite.The results show that the different amount of rare earth origin nephrite ΣREE is 1.78~48.19 μg/g(average 15.14 μg/g), LREE/HREE is 1.69~12.58(average 7.46).The standardized distribution curve of chondromites shifted from obvious right to relatively flat.Normalized single element ratio of rare earth element concentration of(La/Sm)N,(Sm/Ho)N and(Gd/Lu)N are significantly different,Elemental anomaly coefficient of δEu andδCe from obvious negative abnormal to positive abnormal.The research shows thatthe light rare earth, medium rare earth and heavy rare earth of nephrite from different producing areas have different differentiation degree, and having local characteristics.The pH value of hydrothermal solution,oxygen fugacity of surrounding rock and metallogenic environment are the main factors affecting the distribution pattern of rare earth elements in nephrite.