A series of tectonic activities induced by the subduction of the Palaeo‐Asian Ocean (PAO) in the Palaeozoic have been recorded in the North China Craton (NCC). Sedimentary strata provide some precious records to reconstruct the basin evolution in the NCC. In this study, we carried out detrital zircon LA‐ICP‐MS U–Pb dating, sandstone modal analysis, bulk‐rock major, and trace elemental measurements for the Sunjiagou and Liujiagou formations in the eastern Ordos Basin to trace the material source. The results show that the sedimentary rocks were mostly sourced from active continental margins. The detrital zircon ages of the Sunjiagou and Liujiagou formations spread from >3,000 to 250 Ma with peaks of main age populations at 2,508, 1,890, 430, and 270 Ma. Based on the age comparison and the southward palaeocurrents, we consider that the source material of these sedimentary rocks comes from the northern margin of the NCC. This in turn indicates that the amalgamation of the PAO and the NCC should have finished at least by the end of the Late Permian.

《地球科学》(ISSN 1000-2383;CN42-1874/P) (原刊名《地球科学——中国地质大学学报》ISSN 1000-2383;CN42-1233/P)，创刊于1957年，是由教育部主管、中国地质大学主办的综合性地学学术理论期刊，月刊，2015年改名为《地球科学》,她以反映中国地质大学教学与科研最新的、高水平的基础地质、应用地质、资源与环境地质及地学工程技术研究成果为主要任务。

The Northeast China Block is a major component of the Central Asian Orogenic Belt, and its tectonic evolution has attracted much research attention. Ordovician strata are important in reconstructing the tectonic evolution of the Northeast China Block. This paper presents the results of sedimentological, zircon U–Pb, and geochemical analyses of sandstones of the Luohe Formation in the Wunuer area, Northern Great Xing’an Range, Northeast China. Lithological data, sedimentary structures, and grain-size analysis indicate that the Luohe Formation was deposited in a shallow marine environment. Detrital zircon U–Pb dating yields age peaks of 463, 504, 783, 826, 973, and 1882 Ma for sandstones from the Luohe Formation. The youngest zircon grain age of 451 ± 6 Ma represents the maximum depositional age of the Luohe Formation. The peak age at 463 Ma is consistent with the timing of post-collisional magmatism and the formation of the Duobaoshan island arc, while the peak at 504 Ma is consistent with the timing of magmatic activity related to the collision between the Erguna and Xing’an blocks. The peaks at 788, 826, 973, and 1882 Ma correspond to magmatism in the Erguna block, these ages indicate that the sandstones of the Luohe Formation were derived mainly from the Erguna block. Sandstone modal compositional analysis indicates that the provenance of the Luohe Formation was mainly a magmatic arc. The geochemical compositions of the sandstones suggest that the source rocks have continental island arc signatures. Based on the depositional age, sedimentary environment, provenance, and regional geology, it is concluded that the Luohe Formation was deposited in a back-arc basin setting during the formation of the Duobaoshan island arc–basin system in response to subduction of the Paleo-Asian oceanic plate.

东北陆块群是中亚造山带的主要构造单元，关于其前寒武纪古老基底属性的判别、古生代构造单元划分及增生造山演化过程一直是地质学家研究热点。兴安增生地体被认为是东北陆块群的重要组成部分，由于其前寒武纪沉积-岩浆记录的大量缺失，使得奥陶纪沉积-岩浆事件成为研究其构造演化的关键。本文对出露于兴安增生地体奥陶系的多宝山组进行了碎屑锆石LA-ICP-MS U-Pb定年、锆石Hf同位素及地球化学分析，旨在准确限定多宝山组的沉积时限，揭示其沉积环境及物源区性质。研究结果表明，来自大扬气镇南、花朵山南部及伊尔施西北部三个地区的多宝山组变质砂岩的最年轻锆石年龄分别为481±5Ma（D9088）、462±5Ma（296NJ-1）and 473±11Ma（HDG06），类似于其对应加权平均年龄482±3Ma（n=12）、475±6Ma（n=10）和483±8Ma（n=7），由此限定多宝山组的沉积下限为早-中奥陶世。其中 < 1.0Ga样品数量最多的锆石年龄为462~520Ma，峰值年龄为516Ma、497Ma和482Ma；次者在790~980Ma，该年龄区间出现969Ma、830Ma、788Ma、760Ma等峰值；>1.0Ga的具有较弱的峰值（1321~2410Ma），主要为1882Ma和2410Ma两个峰值，以上所有峰值与额尔古纳地块内部同期岩浆岩体完全吻合，说明所研究样品的物源区主要来自额尔古纳地块。对比分析不同区域多宝山组碎屑锆石Hf同位素特征，发现自东向西越靠近额尔古纳地块，多宝山组碎屑锆石ε_Hf（t）值越小，二阶段模式年龄t_DM2越老，暗示物源区基底古老物质逐渐增多。结合奥陶系砂岩的地球化学特征，我们推测这种变化趋势可能反映了由活动大陆边缘向额尔古纳地块内部过渡的构造环境。