银额盆地北部杭乌拉地区下二叠统双堡塘组沉积相及地质意义

Sedimentary Facies and Geological Significance of the Lower Permian Shuangputang Formation in the Hangwula Area, Northern Yin’e Basin

摘要: 银额盆地晚古生代盆地构造属性长期存在裂谷盆地、残余洋盆和弧后盆地等不同认识，制约了区域沉积演化及上古生界油气勘探研究。本文以银额盆地北部杭乌拉地区下二叠统双堡塘组为研究对象，采用野外实测、岩相分析及砂岩QFL物源判别等方法，对其沉积相特征、沉积环境及构造背景进行了研究。结果表明：双堡塘组发育无障壁陆源碎屑海岸和浅海碳酸盐台地两大沉积体系，其中无障壁陆源碎屑海岸相包括过渡带、临滨和前滨亚相，碳酸盐台地相包括台缘滩、开阔台地和局限台地亚相。砂岩QFL物源判别结果显示，样品主要落入火山弧及再旋回造山带物源区，反映物源来自活动大陆边缘。综合沉积相特征、QFL物源判别结果及区域岩浆活动、锆石年代和构造演化资料分析，认为杭乌拉地区早二叠世为活动大陆边缘背景下的弧后盆地环境，该认识主要适用于杭乌拉地区，其区域适用性仍需进一步验证。其中，前滨与临滨砂岩、台缘滩生屑灰岩具有较好的储集潜力，过渡带及局限台地细粒暗色沉积可作为有效烃源岩和区域性盖层，该结果可为杭乌拉地区及银额盆地北部上古生界油气勘探提供沉积学参考。

Abstract: The tectonic nature of the Late Paleozoic Yin’e Basin has long been debated, with various interpretations including rift basin, remnant oceanic basin, and back-arc basin, which have hindered studies on regional sedimentary evolution and Upper Paleozoic hydrocarbon exploration. This paper focuses on the Lower Permian Shuangputang Formation in the Hangwula area of the northern Yin’e Basin. Through field measurements, lithofacies analysis, and sandstone QFL provenance discrimination, we investigate the sedimentary facies characteristics, depositional environments, and tectonic setting. The results indicate that the Shuangputang Formation comprises two major depositional systems: a barrier-free terrigenous clastic coast and a shallow-marine carbonate platform. The barrier-free terrigenous clastic coast includes transitional, shoreface, and foreshore subfacies, while the carbonate platform consists of platform-margin bank, open platform, and restricted platform subfacies. QFL provenance discrimination shows that the samples mainly fall into the fields of volcanic arc and recycled orogenic belt provenances, suggesting derivation from an active continental margin. Integrating sedimentary facies, QFL data, regional magmatism, zircon geochronology, and tectonic evolution, we propose that the Hangwula area was deposited in a back-arc basin setting on an active continental margin during the Early Permian. This interpretation is primarily applicable to the Hangwula area and requires further verification for regional extension. Among these, the foreshore and shoreface sandstones, as well as the platform-margin bioclastic limestones, exhibit good reservoir potential, while the fine-grained dark deposits of the transitional zone and restricted platform may serve as effective source rocks and regional seals. These results provide sedimentological references for hydrocarbon exploration in the Upper Paleozoic of the Hangwula area and the northern Yin’e Basin.