地质科技通报2025，Vol.44Issue(5)：65-81,17.DOI:10.19509/j.cnki.dzkq.tb20240696
黄骅坳陷歧口主凹区东营组砂岩物源方向与沉积模式:来自碎屑锆石U-Pb年代学的制约
Source area and sedimentary model of the sandstone in the Third Member of Dongying Formation in main concave,Qikou Sag,Huanghua Depression:Constraints from detrital zircons U-Pb dating
摘要
Abstract
[Objective]The Qikou Sag,a significant hydrocarbon-bearing sub-basin within the Bohai Bay Basin of eastern China,has recently witnessed a critical exploration breakthrough.Well HT1,drilled in the main trough,encountered a sandstone reservoir within the Third Member of the Dongying Formation(Ed3)and achieved commercial oil flow.However,the precise provenance and spatial distribution of this Ed3 sandstone remain enigmatic.Identifying the sediment source is fundamental to constructing a reliable"source-to-sink"system,which is crucial for predicting the distribution of high-quality reservoirs.This study aims to definitively determine the provenance of the Ed3 sandstone through detrital zircon U-Pb geochronology and establish a robust sedimentary model to guide exploration.[Methods]To address the provenance question,this study employed laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS)U-Pb dating on detrital zircons extracted from the Ed3 sandstone.Zircon is an ideal mineral for provenance analysis due to its high physical and chemical stability,allowing it to survive multiple cycles of erosion and transport while preserving its primary crystallization age.Thus,the age spectrum of detrital zircons in a sedimentary rock serves as a unique fingerprint that can be compared to the age signatures of potential source areas,enabling a direct link between the sediment and its origin.[Results]The U-Pb dating results from the Ed3 sandstone revealed a characteristic age distribution pattern.The detrital zircon ages cluster into four primary intervals:2 600-2 300 Ma(Neoarchean to Paleoproterozoic),1 680-2 000 Ma(Paleoproterozoic),300-240 Ma(Permian),and a remarkably dominant peak between 160-100 Ma(Jurassic to Cretaceous).The overwhelming abundance of zircons in the 160-100 Ma range immediately pointed towards a significant contribution from a source region with intense Mesozoic magmatic activity.The zircon age signature of the Cangxian uplift was examined.Its age spectrum is characterized by a strong peak at 300-240 Ma and a relative lack of Mesozoic zircons,presenting a clear mismatch with the Ed3 sandstone signature and effectively ruling it out as the primary source.In contrast,the Yanshan orogenic belt to the north is a complex tectonic zone with a prolonged magmatic history spanning from the Archean to the Mesozoic.Critically,it is renowned for widespread Jurassic-Cretaceous(Yanshanian)magmatism,with a pronounced age peak precisely between 160 and 100 Ma.The striking similarity between the Ed3 zircon age pattern and the magmatic record of the Yanshan belt provides compelling evidence that the latter served as the principal provenance for the sandstone.Previous studies indicate that the Yanshan orogenic belt experienced significant Cenozoic uplift,coeval with the deposition of the Ed3,creating a well-defined mountain-basin system.Several major paleo-rivers,such as the ancient Yongding River,ancient Chaobai River,and ancient Luan River,are interpreted to have acted as efficient sediment conduits.These rivers eroded the Mesozoic granitic rocks of the Yanshan belt and transported the detritus southward over long distances into the Qikou Sag.[Conclusions]This study successfully resolves the provenance of the Ed3 sandstone in the main trough of the Qikou Sag.Detrital zircon U-Pb geochronology unequivocally identifies the northern Yanshan orogenic belt as the primary source,excluding the nearby Cangxian uplift.The construction of the"remote source,channelized transport,deep-trough deposition"model has profound implications for exploration.It validates the existence of high-quality sandstone reservoirs in the deep troughs formed by long-distance transport systems.Consequently,future exploration efforts should prioritize mapping the paleo-drainage pathways that funneled sediments from the Yanshan belt into the main trough of the Qikou Sag.This model significantly reduces exploration risk in the deep plays of the depression and provides a valuable analog for searching for similar subtle reservoirs in other continental rift basins worldwide.关键词
碎屑锆石/U-Pb定年/歧口凹陷/沉积模式/物源Key words
detrital zircon/U-Pb age dating/Qikou Sag/sedimentation model/source分类
天文与地球科学引用本文复制引用
李长海,杨帆,董晓伟,石倩茹,官全胜,张佼杨,朱华汇,张明振,董越崎,付东立..黄骅坳陷歧口主凹区东营组砂岩物源方向与沉积模式:来自碎屑锆石U-Pb年代学的制约[J].地质科技通报,2025,44(5):65-81,17.基金项目
国家科技重大专项"渤海湾超级盆地油气富集规律与新领域勘探关键技术"(2024ZD1400100) （2024ZD1400100）
中国石油大港油田公司博士后项目"歧口凹陷断砂耦合形成机制与控藏规律研究"(博057) （博057）
