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高校地质学报 ›› 2024, Vol. 30 ›› Issue (04): 397-408.DOI: 10.16108/j.issn1006-7493.2023038

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柴北缘西段嗷唠山地区三叠系碎屑锆石U-Pb 年代学特征及其地质意义

王 波1,2,吴志雄1,2,胡俊杰3,4,5*,马立成3,4,5,马寅生3,4,5,施 辉3,4,5   

  1. 1. 中国石油青海油田分公司勘探开发研究院,敦煌 736202; 2. 青海省高原咸化湖盆油气地质重点实验室,敦煌 736202; 3. 中国地质科学院地质力学研究所,北京 100081; 4. 自然资源部古地磁与古构造重建重点实验室,北京 100081; 5. 中国地质调查局油气地质力学重点实验室,北京 100081
  • 出版日期:2024-08-20 发布日期:2024-08-20

Detrital Zircon U-Pb Geochronology and Geological Significance of the Triassic Strata from Aolaoshan Area, in the West Section of North#br# Qaidam Basin

WANG Bo1,2, WU Zhixiong1,2,HU Junjie3,4,5*,MA Licheng3,4,5,MA Yinsheng3,4,5,SHI Hui3,4,5   

  1. 1. Research Institution of Exploration and Development, PetroChina Qinghai Oilfield Company, Dunhuang 736202, China;
    2. Plateau Saline Lacustrine Basin Oil-Gas Geology Key Laboratory of Qinghai Province, Dunhuang 736202, China;
    3. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China; 4. Key Laboratory of Paleomagnetism and Tectonic Reconstruction, Ministry of Natural Resource, Beijing 100081, China;
    5. Key Laboratory of Petroleum Geomechanics, China Geological Survey, Beijing 100081, China
  • Online:2024-08-20 Published:2024-08-20

摘要: 柴达木盆地三叠纪有无沉积过程及其后期演化等关键地质问题一直存有争议。文章针对柴北缘西段嗷唠山三叠系沉积岩进行了系统的碎屑锆石年代学研究,结合岩石组合分析和区域地层对比,尝试为理清柴北缘三叠纪地层框架提供依据。根据嗷唠山Tb段下部碎屑锆石中获得年轻锆石年龄平均值248 Ma,结合前人从下伏Ta段中获得的古生物资料,可以将嗷唠山三叠系的形成时代限定在早—中三叠世。文章所采集的嗷唠山样品碎屑锆石年龄谱系可分为5组,分布在(243~260 Ma)、(414~538 Ma)、(678~857 Ma)、(1064~1642 Ma)和(1700~2836 Ma),其主要物源分别对应于柴北缘地区分布的印支期岩浆岩、上泥盆统再旋回物质、柴北缘超高压变质带、柳河群以及达肯达坂群。研究区与柴北缘东段怀头他拉地区三叠系具有相同的沉积特征,并且在岩性组合及碎屑锆石年龄谱系上明显区别于周缘祁连和西秦岭三叠纪地层分区,暗示柴北缘地区在三叠纪曾经发育一系列连续或断续分布的沉积地层。早三叠世,受宗务隆洋向南俯冲影响,柴北缘地区开始快速隆升,先期的多套沉积地层与结晶基底被迅速剥蚀,在近源断陷处形成了冲/洪积相为主的沉积地层。中三叠世,周缘构造带的活动强度总体趋于稳定,柴北缘地区处于浅海陆棚-台地相沉积体系,发育厚层灰岩为主的沉积。至晚三叠世,伴随东昆仑—柴达木地体强烈的陆陆碰撞,柴达木盆地整体被迅速抬升,盆地内弱固结的三叠系被大面积剥蚀,部分向东搬运至共和盆地,仅在部分洼陷得以保存。

关键词: 柴达木盆地, 嗷唠山, 三叠系, 碎屑锆石U-Pb年代学, 物源

Abstract: A dispute whether there was Triassic sedimentation or not in Qaidam Basin and its later evolution are continuous as yet. Via systematic analysis of detrital zircon geochronometry, rock assemblages and regional stratigraphic correlation on the Triassic
strata from Aolaoshan area, in the west section of north Qaidam Basin, this study aiming at providing evidence for the Triassic stratigraphic framework in the northern margin of Qaidam. The average age of young zircons in the lower part of Tb Triassic Formation is 248 Ma. Considering paleontological data from the underlying Ta strata, the deposition time limit of the Aolaoshan Triassic deposits was Early to Middle Triassic. The detrital zircon U-Pb ages were between 243-260 Ma, 414-538 Ma, 678-857 Ma, 1064-1642 Ma and 1700-2836 Ma. Respectively, indicating that the sedimentary materials may derived from Indosinian magmatic rocks, Upper Devonian recycle material, North Qaidam tectonic belt, Shaliuhe Group and Dakendaban Group. The study area has the same sedimentary characteristics as the Triassic in the Huaitousala area, and they both are markedly different from the Triassic stratigraphic division in Qilian and West Qinling areas. It is suggested that a series of continuous or intermittent sedimentary strata were developed in the northern margin of the Qaidam Basin during the Triassic period. In the early Triassic, influenced by the subduction of the Zongmurong Ocean to the south, the northern margin of the Qaidam Basin began to uplift rapidly. Several sets of sedimentary strata and crystalline basement in the early period were rapidly denudated, and the sedimentary strata dominated by alluvial and alluvial facies were formed near the source fault depression. In the Middle Triassic, the activity intensity of the peripheral tectonic belt tended to be stable on the whole, and the northern margin of the Qaidam basin was in the shallow sea shelf platform sedimentary system with thick-bedded limestone as the main deposits. Until the late Triassic, with the strong continental collision between East Kunlun and Qaidam terrane, the whole Qaidam Basin was rapidly uplifted, and the weakly consolidated Triassic in the basin was large-scale denudated. Some of the weakly consolidated Triassic in the basin was transported eastward to Gonghe Basin, and only part of the depressions were preserved. 

Key words: Qaidam Basin, Aolaoshan area, Triassic strata, detrital zircon U-Pb geochronology, provenance

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