| 华北克拉通新元古界长龙山组石英砂岩物源组成及其古地理意义 |
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| 引用本文：孟中玙,孙立新,任邦方,田健,李伟桐,刘威,仝云霄.2026.华北克拉通新元古界长龙山组石英砂岩物源组成及其古地理意义[J].地球学报,47(4):703-714. |
| DOI：10.3975/cagsb.2026.030111 |
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| 基金项目:本文由国家自然科学基金项目(编号: 42302125)、中国地质调查局地质调查项目(编号: DD20242607; DD20240027; DD20221727-03)和深地国家科技重大专项“深地大数据共享管理与数字深地系统”项目(编号: 2024ZD1001200; 2024ZD1001206)联合资助。 |
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| 中文摘要:长龙山组是华北克拉通燕辽裂谷盆地新元古代青白口系(Qingbaikou System)的重要地层单元, 被认为是罗迪尼亚(Rodinia)超大陆裂解后最早期的沉积。然而, 其详细的物源组成在燕辽裂谷盆地内部是否存在显著的空间变化尚不清楚。本次工作对涿鹿和兴隆地区长龙山组石英砂岩开展了岩相分析, 碎屑锆石U-Pb定年和Hf同位素分析研究工作, 揭示长龙山组石英砂岩的物源组成及其蕴含的构造古地理意义。石英砂岩呈中-厚层产出, 分选较好, 发育板状交错层理、大型槽状交错层理和大型波痕等沉积构造, 指示水动力较强的前滨沉积环境。碎屑锆石存在两个明显的年龄区间, 一个是新太古代晚期—古元古代早期(2 582~2 422 Ma; 峰值为~2.5 Ga), εHf(t)值在?3.4 ~ +5.5之间, 对应的地壳模式年龄为2.7~3.2 Ga; 另一个是古元古代(2 016~ 1 725 Ma; 峰值为~1.8 Ga), 锆石的εHf(t)值在?17.0 ~ ?7.4之间, 对应的地壳模式年龄为3.0~3.6 Ga。这两个年龄峰值是华北克拉通前寒武纪两次重要地质事件的产物, ~2.5 Ga的锆石对应陆壳生长和初始克拉通化的记录; ~1.8 Ga的锆石与华北克拉通东部和西部碰撞拼合形成统一结晶基底事件的时间相吻合, 对应哥伦比亚(Columbia)超大陆聚合事件。燕辽裂谷盆地内部长龙山组物源组成呈现显著的空间分异, 表明长龙山组沉积时期, 燕辽裂谷盆地可能并非一个统一的沉积盆地, 而是受古地理格局控制、具有多个相对独立物源供给系统的沉积单元。这一认识为理解华北克拉通在Rodinia超大陆裂解初期的差异响应提供了新视角。 |
| 中文关键词:长龙山组 物源 华北克拉通 燕辽裂谷盆地 新元古界 古地理 |
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| Provenance of the Quartzose Sandstones in the Changlongshan Formation (Neoproterozoic) of the North China Craton and Its Paleogeographic Implications |
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| Abstract:The Changlongshan Formation is an important stratigraphic unit of the Qingbaikou System (Neoproterozoic) within the Yan–Liao Rift Basin of the North China Craton, considered to be the earliest sedimentary record following the breakup of the Rodinia supercontinent. However, it remains unclear as to whether there are any substantial spatial differences in the detailed provenance composition of the Yan–Liao Rift Basin. In this study, we performed lithofacies analysis, detrital zircon U-Pb dating, and Hf isotopic analysis of quartzose sandstones from the Changlongshan Formation in the Zhuolu and Xinglong areas to elucidate their provenance composition and tectonic-paleogeographic implications. The quartzose sandstones were found to be medium-thick bedded and moderately/well sorted. The sedimentary structures include tabular cross-bedding, large-scale trough cross-bedding, and wave ripples, indicative of a high-energy foreshore depositional environment. The detrital zircons are characterized by two distinct age clusters: (1) Late Neoarchean to Early Paleoproterozoic (2 582–2 422 Ma; peak at ~2.5 Ga), with εHf(t) values ranging from –3.4 to +5.5, and corresponding crustal model ages of 2.7–3.2 Ga; and (2) Paleoproterozoic (2 016–1 725 Ma; peak at ~1.8 Ga), with εHf(t) values between –17.0 and –7.4, and crustal model ages of 3.0–3.6 Ga. These two age peaks are primarily inherited products of the two major tectonic–thermal events that occurred during the Precambrian era of the North China Craton. The ~2.5 Ga detrital zircons provide a record of crustal growth and initial cratonization, whereas the ~1.8 Ga detrital zircons coincide with the collision and amalgamation of the eastern and western blocks of the North China Craton, forming a unified crystalline basement that corresponds to the assembly of the Columbia supercontinent. The age spectra of the detrital zircons of the Changlongshan Formation are characterized by substantial spatial variations across the Yan–Liao Rift Basin, thus indicating that during the depositional period of the Changlongshan Formation, rather than being a unified sedimentary basin, the Yanliao Rift Basin may have comprised multiple relatively independent sedimentary units with distinct source-to-sink systems controlled by the paleogeographic framework. These findings will provide a new perspective for comprehending the differential response of the North China Craton during the initial stages of the breakup of the Rodinia supercontinent. |
| keywords:Changlongshan Formation provenance North China Craton Yan–Liao Rift Basin Neoproterozoic paleogeography |
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