苏北盆地古近系阜三段物源特征及其形成的构造背景分析

Provenance characteristics and tectonic setting analysis of the 3^(rd) Member of the Paleogene Funing Formation, Subei Basin

综合碎屑组分、砾石成分、稀土元素、砂岩含量分布和砂砾岩分布特征的分析,并借鉴前人的研究成果,可以得出,苏北盆地古近系阜三段的物源区主要有6个。(Ⅰ,Ⅱ)建湖隆起分别向南北两侧供源:向南为金湖东部凹陷、高邮北部凹陷和海安凹陷供源,母岩成分主要为中酸性火成岩、石英岩和花岗岩;向北为盐城凹陷供源,母岩成分主要为中酸性火成岩、石英岩、基性火成岩和花岗岩,与建湖隆起南侧相比,存在基性火成岩的混入。(Ⅲ)张八岭隆起向东为金湖西部凹陷供源,母岩成分主要为中酸性火成岩和石英岩,与建湖隆起南侧母岩相比,缺少花岗岩成分。(Ⅳ)苏南隆起向北为高邮南部凹陷供源,母岩成分主要为碳酸盐岩和中酸性火成岩,与高邮北部凹陷母岩成分有差异,存在大量碳酸盐岩成分的混入。(Ⅴ)滨海隆起向南为阜宁凹陷供源,据调研,母岩主要为中深变质岩和古生界沉积岩。(Ⅵ)据调研,鲁苏隆起东段为涟北凹陷供源,主要为浅变质酸性火成岩。结合Bhatia稀土元素特征参数对比和Dickinson构造背景判别图解,认为源区构造背景属于与大陆岛弧相关的活动大陆边缘和再旋回造山带。

Based on the analyses of debris component,gravel composition,rare earth element,sandstone content distribution and glutenite distribution characteristics,and drawing on the previous research results,it can be concluded that there are six main provenance areas in the 3 rd Member of the Funing Formation,Subei Basin.The south and north sides of the Jianhu Uplift(areas Ⅰ,Ⅱ) provide sources,respectively,southward to the Eastern Jinhu,Northern Gaoyou and Hai’an Sags,with the parent rocks including mainly medium-acidic igneous rock,quartzite and granite,and northward to the Yancheng Sag,with the addition of basic igneous rock to the parent rocks from area Ⅰ.The Zhangbaling Uplift(area Ⅲ) provides source eastward to the Western Jinhu Sag,with the main parent rock types almost identical to that of area Ⅰ but without granite.The Sunan Uplift(area Ⅳ) provides source northward to the Southern Gaoyou Sag,supplying mainly carbonate and medium-acidic igneous rocks as the parent rocks that are very different from the parent rocks(supplied from area Ⅰ) in the Northern Garyou Sag by the presence of large amount of carbonate rocks.According to the literature reports,the Binhai Uplift(area Ⅴ) provides source southward to the Funing Sag,with medium-deep metamorphic rocks and Paleozoic sedimentary rocks as the parent rocks;while the eastern section of the Lusu Uplift(area Ⅵ) provides sources to the Lianbei Sag,with the parent rock mainly including metamorphic acidic igneous rock of the basement.Combined with the Bhatia REE characteristic parameters and Dicknson tectonic discrimination diagrams,it is considered that the tectonic settings of the source areas are mainly active continental margins associated with continental island arc and recycled orogenic belt.