摘要
水泉沟杂岩体的δ１８Ｏ‰值除个别样品高于１０‰或低于５．５‰外，大多数在５．５‰～１０．０‰之间。其三组铅同位素比值明显高于本区太古界桑干群变质岩，并位于上地幔和下地壳铅增长线之间。利用ＲｂＳｒ等时线求得锶同位素初始值为０．７０６１８±０．０００１４，利用Ｆａｕｒｅ［１］提出的二元混合锶模型求得岩浆源区由约６４％的上地幔组分和约３６％的地壳组分组成。通过对其Ｏ、Ｐｂ和Ｓｒ同位素综合分析后得出，岩浆起源于上地幔的顶部和下地壳底部的过渡带。
The results presened in this paper shows that most δ 18 O‰ values of the Shuiquangou complex range within 5.5 and 10.0, except those of the a few samples are beyond the range of 10.0 to 5.5. The low δ 18 O‰ value (2.9‰) of biotite-pyroxene diorite implies that the meteoric water may play a role in the magmatic evolution. Their lead isotopic values are much higher than those of the Archean metamorphic rocks of the Sanggan group in this area, and located between the two lead growth curves of upper mantle and lower crust. The inital 87 Sr/ 86 Sr value by the Rb Sr isochron is 0.706 18±0.000 14, showing a mixing sources of the mantle and the crust. Based on model of the mixed strontium of two members by Faure (1986), the author concluded that the source materials consist of about 64% mantle materials and 36% crustal materials. According to the comprehensive analyses for their O, Pb and Sr isotopic compositions, the author believes that the source region should be the location between the top of upper mantle and the bottom of lower crust.
基金
国家自然科学基金
