东昆仑山清水泉镁铁质——超镁铁质岩的地球化学特征

Geochemical characteristics of the Qingshuiquan mafic-ultramafic rocks, East Kunlun

东昆仑清水泉地区发育一套镁铁质—超镁铁质岩块组合,玄武岩Ti2O含量平均为2.11%,∑LREE/∑HREE=4.64～7.58,(La/Lu)N平均值7.05,稀土配分曲线平缓右倾,δEu平均值1.08;玄武岩大离子亲石元素(K、Rb、Ba、Th)富集,Sr相对亏损,高场强元素(Nb、Ta、Zr、Hf、Yb)为负异常,Th/Ta平均值51.03,(La/Nb)N=1.44～4.25,Zr/Nb=14.53～17.71,Zr/Y=4.68～6.79,Th/Yb、Ta/Yb和Ce/Yb平均值分别为6.50、0.20和23.61。这些特征显示大陆拉斑玄武岩的特征,不是蛇绿岩组成单元。

A suite of mafic-ultramafic rocks occurs in the Qingshuiquan area, East Kunlun. The content of Ti2O is 2.11%, the ratio of ∑LREE/∑HREE is 4.64-7.58 and the ratio of (La/Lu)N averages 7.05. The smooth REE patterns are inclined to the right. The Eu anomaly is not pronounced with an average of 1.08. The basalt is characterized by relative enrichment of LILE (K, Rb, Ba and Th) and relative depletion of Sr, negative HFSE (Nb, Ta, Zr, Hf and Yb) anomalies, the average Th/Ta=51.03, (La/Nb)N=1.44-4.25, Zr/Nb=14.53-17.71 and Zr/Y=4.68-6.79, and the average Th/Yb, Ta/Yb and Ce/Yb are 6.50, 0.20 and 23.61 separately. All of above characteristics show that the Qingshuiquan basalt is continent tholeiite, rather than a component unit of ophiolites.