Lead Isotopic Compositions of the Kohistan-Ladakh Terrane in NW Himalayan Syntax, Pakistan and their Tracer Significance
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摘要: 作为西北喜马拉雅构造结的重要组成部分,科希斯坦-拉达克地体的Pb同位素组成具有混合Pb的特征.笔者在前人研究的基础上重新分析了Pb同位素组成特征,并计算了H-H单阶段演化模式年龄,以及μ、ω、Th/U、Δβ、Δγ值等重要参数.分析表明,Pb主要来源于壳幔混合物质,但也混入了部分亚洲大陆地壳物质,其类型相当于受岩浆控制的俯冲带Pb同位素组成.通过研究,发现Pb同位素比值具有DUPAL异常特征,推测异常Pb可能来源于亚洲大陆边缘,这可作为研究本区岩浆作用及演化的重要基础资料.
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关键词:
- 西北喜马拉雅构造结 /
- 科希斯坦-拉达克地体 /
- Pb同位素 /
- 巴基斯坦
Abstract: Served as an important part of northwest Himalayan syntax, the Kohistan-Ladakh terrane is characterized by the mixed source in the lead isotopic compositions. On the basis of previous studies, the lead isotopic compositions of the Kohistan-Ladakh terrane have been re-analyzed, and their H-H single-stage evolution model ages as well as characteristic parameters (such as, μ values, ω values, Th/U ratios, Δβ values and Δγ values) are calculated in this paper. The study results show that, the lead is mainly derived from the crust-mantle mixing substances, mixed with some crustal materials from Asian continent, and their types are similar to the subducted lead compositions that controlled by magmatism. The results indicated that their lead isotopic compositions displayed the DUPAL abnormal characteristics. Thus, it is speculated that the anomalous lead may come from Asian continent margin, which can serve as basic reference for studying magmatism and evolution in this area.-
Keywords:
- NW Himalayan Syntax /
- Kohistan-Ladakh terrane /
- lead isotope /
- Pakistan
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