本文選題：鄂爾多斯盆地 + 火山凝灰?guī)r�。� 參考：《地質(zhì)論評》2017年05期

【摘要】：鄂爾多斯盆地西緣北段奧陶紀(jì)剖面中出露有火山凝灰?guī)r夾層,它們是火山噴發(fā)的凝灰物質(zhì)沉積的產(chǎn)物,其研究對于鄂爾多斯盆地奧陶紀(jì)年代地層格架的厘定和構(gòu)造背景的確定有重要意義。本文報道了鄂爾多斯盆地西緣北段烏海地區(qū)哈圖克溝剖面烏拉力克組頂部火山凝灰?guī)r的鋯石U-Pb年齡和Hf同位素特征。鋯石LA-ICPMS U-Pb年齡為454.9±3.4Ma,SHRIMP U-Pb年齡為456.4±4.2Ma,結(jié)合古生物地層學(xué),將烏拉力克組的沉積時代厘定為中奧陶世達(dá)瑞威爾階晚期—晚奧陶世桑比階。鋯石原位微區(qū)Hf同位素εHf(t)=+4.02~+10.98,n(176Hf)/n(177Hf)值變化范圍為0.282 619~0.282 963之間,二階段模式年齡變化范圍為729~1178Ma。根據(jù)凝灰?guī)r與研究區(qū)周緣造山帶的鋯石U-Pb年齡及Hf同位素特征對比判斷火山凝灰?guī)r物質(zhì)應(yīng)主要來自于其西南方向的北祁連造山帶和/或北秦嶺造山帶。鄂爾多斯盆地西緣和南緣廣泛分布的火山凝灰?guī)r具有一致的就位時間和物源,表明盆地西緣和南緣都受到了中—晚奧陶世北祁連和/或北秦嶺洋殼俯沖引起的火山弧噴發(fā)的影響。
[Abstract]:Volcanic tuff intercalation appeared in the Ordovician section of the northern section of the western margin of the Ordos Basin. The study is of great significance for the determination of the Ordovician chronostratigraphic framework and the determination of the tectonic background in the Ordos Basin. The zircon U-Pb age and HF isotopic characteristics of volcanic tuff at the top of the Ulalik formation in the northern section of the western margin of the Ordos Basin are reported in this paper. The U-Pb age of zircon LA-ICPMS U-Pb is 454.9 鹵3.4 Ma-SHRIMP U-Pb age of 456.4 鹵4.2 Ma. combined with paleostratigraphy, the sedimentary age of the Ulalik formation is determined to be the late stage of the Ordovician stage and the late Ordovician stage to the late Ordovician stage. The zircon in-situ HF isotope 蔚 HF (t) = 4.02 ~ 10.98 Hf (176HF) / n (177Hf) varies from 0.282 to 0.282,963, and the two-stage model age range is 72991178 Ma.The zircon in-situ microregion 蔚 HF (t) = 4.02 ~ 10.98 Hf (176HF) / n (177Hf) varies from 0.282 to 0.282,963. According to the zircon U-Pb age and HF isotopic characteristics of the tuff and the marginal orogenic belt of the study area, it is concluded that the volcanic tuff material is mainly from the North Qilian orogenic belt and / or the North Qinling orogenic belt in the southwest direction of the tuff. The volcanic tuff widely distributed in the western and southern margin of the Ordos Basin has a consistent emplacement time and provenance. It is shown that both the western margin and the southern margin of the basin are affected by the volcanic arc eruption caused by the subduction of the North Qilian and / or the North Qinling oceanic crust in the Middle and late Ordovician.
【作者單位】： 中國地質(zhì)科學(xué)院礦產(chǎn)資源研究所國土資源部鹽湖資源與環(huán)境重點實驗室;
【基金】：國家重大基礎(chǔ)研究計劃(973)項目(編號:2011CB403001) 中國地質(zhì)調(diào)查局地調(diào)工作項目(編號:1212011085516)的成果~~
【分類號】：P534.42;P597

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