Due to the lack of paleomagnetic data and paleoclimatic records, the paleocontinental belonging of the Yidun terrane in northeastern Tibet plateau is debated. In this paper, we use the distribution of the Emeishan large igneous province (ELIP) to put the issue to rest. The ELIP is the product of mantle plume activity, which took place at 260 ± 3 Ma in the western margin of the Yangtze craton. The Yangtze craton is the northern part of the South China paleocontinental block. Our new discovery of four mafic dikes in the Yidun terrane with ages and chemistry like the ELIP strongly supports a new interpretation that this terrane was an integral part of the Yangtze craton during the ELIP magmatic event. Baddeleyites from these mafic dikes yield the U–Pb ages of 257.1 ± 4.8, 259.8 ± 8.5, 260.2 ± 4.5 and 261.5 ± 6.8 Ma for each of these dikes, which are similar to the zircon U-Pb ages of the mafic–ultramafic intrusions of the ELIP within the Yangtze craton. The Yidun mafic dikes and some high-Ti basalts of the ELIP within the Yangtze craton have similar Sr-Nd isotope compositions and mantle-normalized incompatible trace element distribution patterns, indicating similar mantle source compositions. Mixing calculation using Sr-Nd isotope compositions shows that the parental magmas for the Yidun mafic dikes experienced only 2–3 % crustal contamination. Partial melting modelling shows that the primary magmas for the Yidun mafic dikes were produced by 5–6 % mantle partial melting at the depths > 85 km below surface, consistent with mantle plume-related magmatism in a continental setting. The Yidun terrane is a new exploration frontier for magmatic Fe-Ti-V oxide deposits that are present elsewhere in the ELIP.

中文翻译：

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峨眉山大型火成岩省藏东北部高原镁铁质岩脉的发现对古大陆重建和矿产勘探的意义


由于缺乏古地磁资料和古气候记录，藏东北部高原义墩地层的古大陆归属存在争议。在本文中，我们利用峨眉山大火成岩省 （ELIP） 的分布来解决这个问题。ELIP 是地幔羽流活动的产物，发生在长江克拉通西缘 260 ± 3 马。长江克拉通是华南古大陆块的北部。我们在义墩地层中新发现的四个镁铁质岩脉，其年龄和化学性质都像 ELIP 一样，有力地支持了一个新的解释，即该地层在 ELIP 岩浆事件期间是长江克拉通的组成部分。这些镁铁质岩脉的 Baddeleyite 的 U-Pb 年龄分别为 257.1 ± 4.8、259.8 ± 8.5、260.2 ± 4.5 和 261.5 ± 6.8 马，这与长江克拉通内 ELIP 的镁铁质-超基铁质侵入体的锆石 U-Pb 年龄相似。长江克拉通内义墩镁铁质岩脉和ELIP的一些高Ti玄武岩具有相似的Sr-Nd同位素组成和地幔归一化不相容微量元素分布模式，表明相似的地幔源组成。使用 Sr-Nd 同位素成分的混合计算表明，义墩镁铁质岩脉的母岩浆仅经历了 2-3% 的地壳污染。部分熔化模型显示，义墩镁铁质岩脉的原生岩浆是在地表以下 85 公里的深度 > 由 5-6% 的地幔部分熔化产生的，这与大陆环境中与地幔羽流相关的岩浆作用一致。Yidun 地层是 EILIP 其他地方存在的岩浆 Fe-Ti-V 氧化物矿床的新勘探前沿。