The Xilin Group, composed of Chenming, Laodaomiaogou, Qianshan and Wuxingzhen formations, is one of the early Paleozoic terranes in the eastern Songliao Massif and mainly consists of thick layered fine clastic and carbonate rocks. This paper presents LA–ICP–MS zircon U–Pb geochronology data of the Laodaomiaogou and Qianshan formations, and further constrains their provenance and the early Paleozoic tectonic evolution of the Songliao Massif on the eastern Central Asian Orogenic Belt. Most of the zircons from the Laodaomiaogou and Qianshan formations show magmatic oscillatory zoning and high Th/U ratios (0.26–2.41). Zircon U–Pb dating results indicate that the detrital zircons from the silty mudstone of the Laodaomiaogou Formation yielded 634 Ma, 775 Ma, 820 Ma, 880 Ma and 927 Ma peak ages, as well as multi-episodic Archean to Paleo- and Meso-proterozoic ages (1405–643 Ma), implying its deposition time is less than ∼634 Ma. Further combining with the occurrence of the early Cambrian fossils, the Laodaomiaogou Formation was deposited during the late stage of the early Cambrian (∼514 Ma). The zircons from the K-bentonite of the Qianshan Formation showed four peak ages of 444 Ma, 471 Ma, 489 Ma and 518 Ma and the youngest age peak of 444±4 Ma (n = 6) indicate that the Qianshan Formation was deposited during the Late Ordovician. In addition, the peak ages of detrital zircons in the silty mudstone of the Qianshan Formation are 472 Ma and 498 Ma, as well as two other concordant points with ²⁰⁷Pb/²⁰⁶Pb apparent ages of 1824 Ma and 1985 Ma. The dating results in this paper, together with published data, indicate the absence of the Pan-African magmatic events in the Songliao Massif before the initial deposition of the Xilin Group, compared with those distributed widely in the Jiamusi Massif. Taken together, we concluded that the depositional provenance of the Laodaomiaogou and Qianshan formations was derived from the Songliao Massif. Furthermore, the characteristics of the detrital zircon age composition and rock association indicate that the Laodaomiaogou Formation formed in a passive continental margin environment in contrast to the Qianshan Formation which formed in an active continental margin environment. The above results also imply that the Songliao and Jiamusi massifs might have not yet collided before the Late Ordovician.

中文翻译：

---

锡林群碎屑锆石U-Pb年代学：对松辽地块早古生代构造演化的制约

锡林群由晨鸣组、老道庙沟组、千山组和五星镇组组成，是松辽地块东部早古生代地体之一，主要由厚层状细碎屑岩和碳酸盐岩组成。本文提出了老道庙沟组和千山组的LA-ICP-MS锆石U-Pb年代学资料，进一步确定了它们的物源和中亚造山带东部松辽地块早古生代构造演化。老道庙沟组和千山组的大部分锆石显示出岩浆振荡分带和高Th/U比值（0.26-2.41）。锆石U-Pb定年结果表明，老道庙沟组粉砂质泥岩碎屑锆石的峰龄分别为634 Ma、775 Ma、820 Ma、880 Ma和927 Ma，以及多幕太古代到古和中元古代（1405-643 Ma），这意味着其沉积时间小于~634 Ma。进一步结合早寒武世化石的产状，老道庙沟组沉积于早寒武世晚期（~514 Ma）。千山组钾膨润土锆石显示出444 Ma、471 Ma、489 Ma和518 Ma的四个峰龄，年龄最小的峰为444±4 Ma（n=6），表明千山组沉积于晚奥陶世。此外，千山组粉砂质泥岩中碎屑锆石的峰值年龄分别为472 Ma和498 Ma，以及另外两个与 老道庙沟组沉积于早寒武世晚期（～514 Ma）。千山组钾膨润土锆石显示出444 Ma、471 Ma、489 Ma和518 Ma的四个峰龄，年龄最小的峰为444±4 Ma（n = 6），表明千山组沉积于晚奥陶世。此外，千山组粉砂质泥岩中碎屑锆石的峰值年龄分别为472 Ma和498 Ma，以及另外两个与 老道庙沟组沉积于早寒武世晚期（～514 Ma）。千山组钾膨润土锆石显示出444 Ma、471 Ma、489 Ma和518 Ma的四个峰龄，年龄最小的峰为444±4 Ma（n=6），表明千山组沉积于晚奥陶世。此外，千山组粉砂质泥岩中碎屑锆石的峰值年龄分别为472 Ma和498 Ma，以及另外两个与²⁰⁷铅/ ²⁰⁶Pb 表观年龄为 1824 Ma 和 1985 Ma。本文的测年结果和已发表的资料表明，与佳木斯地块的广泛分布相比，松辽地块在锡林群初始沉积之前没有泛非岩浆事件。综上所述，我们得出结论，老道庙沟组和千山组的沉积物源来自松辽地块。此外，碎屑锆石年龄组成和岩石组合特征表明，老道庙沟组形成于被动大陆边缘环境，而千山组形成于活跃大陆边缘环境。上述结果也暗示松辽和佳木斯地块可能在晚奥陶世之前尚未发生碰撞。