胶东昌邑地区新太古代石英岩的锆石U-Pb年代学和Hf同位素特征及其地质意义

发布时间：2018-06-12 05:17

本文选题：石英岩 + 碎屑锆石　；参考：《岩石学报》2017年09期

【摘要】：基底古老地层的研究可以为探索地球早期陆壳形成与演化历史提供重要支持,胶东地区是华北克拉通变质基底重要的出露区之一,在胶北地体的西缘有一套高成熟度的古老石英岩-山阳村石英岩,前人将其划归古元古代粉子山群的小宋组,但缺乏明确的年代学限定。本文对山阳村石英岩的碎屑锆石进行U-Pb年代学和Hf同位素分析,获得年龄谱的最大峰值为2501±16Ma,且是最小峰值年龄。与古元古的粉子山群和中元古的芝罘群的碎屑锆石年龄谱均不同。综合年龄谱特征、野外产状以及岩石组合,本文认为山阳村石英岩是新太古代的岩石建造,建议为其单独建立新太古代岩石地层单位。结合本次研究及前人工作本文认为应将原粉子山群小宋组划到太古代归属胶东岩群。山阳村石英岩中,~2.5Ga锆石Hf同位素εHf(t)0且从下方靠近亏损地幔演化线并在~2.7Ga地壳演化线附近分布,显示其原岩来自~2.7Ga新生地壳的重熔;ca.2.7~3.0Ga的锆石Hf同位素εHf(t)0且在~3.1Ga地壳演化线附近,意味着其母岩的源区为~3.1Ga的新生地壳,且在ca.2.7~3.0Ga发生了持续的地壳再熔融;3.0Ga碎屑锆石的Hf同位素εHf(t)0,源区岩石形成于更古老陆壳物质的再循环。已知的胶北地块3.0Ga锆石的Hf同位素特征暗示华北克拉通在4.1Ga前就存在地壳,而且在~4.1Ga发生了重熔。
[Abstract]:The study of the ancient basement strata can provide important support for the exploration of the formation and evolution history of the early continental crust. The Jiaodong area is one of the important outcrop areas of the North China Craton metamorphic basement. In the western margin of Jiaobei terrane, there is a set of ancient quartzite with high maturity-Shanyangcun quartzite, which was classified as Xiaosong formation of Gu Yuan ancient fangzishan group, but lack of definite chronological limitation. U-Pb geochronology and HF isotopic analysis have been performed on the detrital zircons from the quartz quartzite in Shanyangcun. The maximum peak value of the age spectrum is 2501 卤16 Ma and the minimum peak age is obtained. The zircon age spectra of the clastic zircon are different from those of the Gu Yuan group and the Middle Proterozoic Zhifu group. Based on the characteristics of age spectrum, field occurrence and rock assemblage, it is considered that the quartz rock in Shanyangcun is a NeoArchean rock formation, and it is suggested that the NeoArchean lithostratigraphic unit be established alone. Combined with this study and previous work, it is considered that the Xiaosong formation of the Yuanfanzishan Group should be assigned to the Jiaodong Rock Group in Archean. The zircon HF isotope 蔚 Hft0 of 2.5 Ga zircon from Shanyangcun quartzite and its distribution near the depleted mantle evolution line and near the 2.7Ga crustal evolution line indicate that the source rocks originated from the remelted ca.2.7 ~ 3.0Ga zircon HF isotope 蔚 Hft0 and near the 3.1Ga crustal evolution line. It means that the source area of the source rock is the new crust of 3.1Ga, and the continuous crustal remelting occurs in the ca.2.7 ~ 3.0Ga, and the HF isotope 蔚 Hfft0 of the zircon of the 3.0Ga clastic zircon occurs. The source rocks are formed in the recirculation of the older continental crust material. The known HF isotopic characteristics of 3.0 Ga zircon from the Jiaobei block suggest that the North China Craton existed before 4.1 Ga and remelted at 4.1 Ga.
【作者单位】：中国地质调查局天津地质调查中心(天津地质矿产研究所);西北大学大陆动力学国家重点实验室;
【基金】：国家自然科学青年基金项目(41602200) 国家重点研发计划项目(2016YFC0600107-6) 中国地质调查局地质调查项目(121201006000150009、12120114034201) 大陆构造与动力学国家重点实验室开放基金(K201510)联合资助
【分类号】：P588.341;P597

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