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近20年来,激光原位测定技术已广泛应用于锆石、斜锆石、钙钛锆石、异性石等Hf含量较高矿物的Hf同位素测定上,但对于Hf含量较低(通常<100ppm)矿物的Hf同位素激光原位测定,无论是技术研发还是实际应用,均开展得较少.本文利用配有193nm激光的Neptune多接收等离子体质谱(MC-ICP-MS),在原位模式下对金红石进行了Hf同位素测定实验.首先,对国内U-Pb年龄参考金红石JDX进行了一系列Hf同位素测定实验,确认其Hf同位素组成在空间上极为均匀,溶液测定结果显示,JDX的176Hf/177Hf比值为(0.281795±0.000015)(2SD,n=33),~(176)Lu/~(177)Hf比值为(0.000018±0.000004)(2SD,n=17).以JDX作为Hf同位素测定的内部标准,对目前金红石微区U-Pb年龄其他标准参考物质R10、Sugluk-4和PCA-S207进行了176Hf/177Hf比值测定,其结果与文献报道值一致.因此,对于低Hf含量(~50ppm)的金红石,激光原位多接收等离子体质谱(LA-MC-ICP-MS)可以获得可靠的176Hf/177Hf比值,同时也表明本文所采用的分析方法是合适的.运用上述建立的方法,对华北克拉通西部孔兹岩带中不同地区超高温麻粒岩的金红石和锆石进行了Hf同位素测定,结果表明该麻粒岩的变质演化历史比以前认为的要复杂得多.
In the recent 20 years, in situ laser in situ measurement has been widely used in the determination of Hf isotopes of higher Hf minerals such as zircon, orthoclase zircon, zirconolite, and heterosexual Hf isotopes. However, for Hf isotopes with low Hf content (usually <100ppm) Hf isotope laser in-situ determination of minerals, both in technical research and development or practical application, are carried out less.In this paper, with a 193 nm laser Neptune multi-receiver plasma mass spectrometry (MC-ICP-MS), in situ mode Rutile Hf isotope determination experiment.Firstly, a series of Hf isotope determination experiments were conducted on the domestic U-Pb age rutile JDX to confirm that the Hf isotopic composition of the rutile JDX is extremely spatially homogeneous. The results of the solution determination showed that the JDH 176Hf / 177Hf ratio (2SD, n = 33), and the ratio of ~ (176) Lu / ~ (177) Hf was (0.000018 ± 0.000004) (2SD, n = 17) with JDSD as the internal standard for Hf isotope determination The results of the 176Hf / 177Hf ratio determination of the other standard reference materials R10, Sugluk-4 and PCA-S207 at the U-Pb age of the rutile micro-region are consistent with those reported in the literature Therefore, for rutile with low Hf content (~ 50ppm) , Laser in situ multiple-absorption plasma mass spectrometry (LA-MC-ICP-MS) And a reliable 176Hf / 177Hf ratio, and also shows that the analysis method adopted in this paper is suitable.Using the above method, the rutile and zircons of ultrahigh temperature granulite in different areas of North China craton Hf isotopic measurements were performed and the results show that the metamorphic evolution history of the granulite is much more complicated than previously thought.