摘要
山东和辽宁金伯利岩的稀土元素球粒陨石标准化曲线均向右倾斜,(La/Yb)N比值为22.7—357.9,LREE/HREE比值12.4—61.3,为轻稀土富集型。含金刚石较富的金伯利岩∑REE变化范围较小,多集中在300—600ppm之间;贫(无)矿金伯利岩∑REE变化范围较大,大多数为低于300ppm或高于600ppm。所以金伯利岩∑REE在寻找金刚石中可以作为重要的参考数据。金伯利岩深源捕虏体的REE含量低,如山东金伯利岩捕虏体∑REE237.6ppm,河北和辽宁的榴辉岩分别为55.2ppm和73.3ppm,山东的纯橄岩捕虏体∑REE最低,仅10.6ppm。
All of the chondrite-normalized REE patterns of kimberlites from Shandong and Liaoning, incline to the right, the (La/Yb)_N ratios changed from 22.7 to 357.9 and the LREE/HREE ratios from 12.4 to 61.3, belonging to LREE-rich type (Fig. 1 and 2). This characteristic may be related with the LREE's strong alkalinity and easily getting into the alkaline kimberlite.
Moreover, the above kimberlites show the following REE geochemical characteristics: the (La/Sm)_N ratios changed from 3.8 to 11. 5, the (Gd/Yb)_N ratios from 4.1 to 18.6. The δEu values changed from 0.75 to 1.22, but most of them are between 0.80 to 0.99.
The ΣREE ranges of diamond-rich kimberlites are smaller: between 300 and 600 ppm, for instance, ranging from 361.6 to 544.7 ppm in Shengli No. 1 pipe, Shandong province; from 378.4 to 511.9 ppm in No. 50, 51, 42 and 30 pipes, Liaoning province. The ΣREE ranges of diamond-poor or -free kimberlites are larger, and the ΣREE contents are either less than 300 ppm or more than 600 ppm (Table 2). Therefore ΣREE of kimberlite is an important parameter in diamond exploration.
The ΣREE contents of xenoliths in kimberlites are: kimberlite xenolith 237.6 ppm, eclogite 55.2 to 73.3 ppm, dunite 10.6 ppm, they are all much lower than those of diamond-rich kimberlites (Table 1). The REE patterns for kimberlites are apparently different from those of eclogite and dunite xenoliths (Fig.4).
出处
《岩石矿物学杂志》
CAS
CSCD
1990年第4期300-308,共9页
Acta Petrologica et Mineralogica
