以王场背斜古近系潜江组三段4亚段第10韵律层(Eq34-10韵律)和潜江组四段0亚段第5韵律层(Eq40中-5韵律)钻井岩心为主要研究对象,通过全岩X射线衍射(XRD)和电感耦合等离子体质谱仪(ICP-MS)实验分析,对潜江凹陷不同韵律层的物源属性与沉积环境开展研究.研究表明,这两套韵律层的矿物组成特征、稀土元素含量及配分特征具有明显的差异:Eq34-10韵律的硅酸盐矿物主要以黏土矿物和石英为主,Eq40中-5韵律的硅酸盐矿物主要以斜长石、黏土矿物和石英为主,两者的稀土元素含量与硅酸盐矿物含量均呈正相关,Eq34-10韵律的碎屑岩类稀土元素分馏程度大于碳酸盐岩类,而Eq40中-5韵律的碎屑岩类稀土元素分馏程度与碳酸盐岩类相似,指示这两套地层的母源物质存在差异,或者Eq34-10韵律沉积时期气候相对更为温暖湿润、风蚀作用更强,这两套地层的沉积水体均为还原环境,而Eq34-10韵律沉积时期湖泊水体可能更深,更有利于有机质的堆积与保存,由此推断Eq34-10韵律更具有勘探潜力.

Taking the drilling cores of the 10th rhythmite of Eq34 Submember(Eq34-10 rhythmite) and 5th rhythmite of middle Eq40 Submember(Eq40-5 rhythmite) of Qianjiang Formation in Wangchang anticline as main research object, the provenance properties and sedimentary environment of different rhythmite in Qianjiang Depression were studied through the analysing of XRD and ICP-MS. The results show that there are obvious differences in mineral composition, REE content and distribution between the two rhythmites. Clay minerals and quartz are the main silicate minerals in Eq34-10 rhythms, while plagioclase, clay minerals and quartz are the main silicate minerals in Eq40-5 rhythmite. The contents of REE and silicate minerals of the two sets were positively correlated. The REE fractionation degree of clastic rock in Eq34-10 rhythmite is higher than that of carbonate rocks, while that of clastic rock in Eq40-5 rhythmite is similar to that of carbonate rocks. It is indicated that the provenance of these two rhythmites is different, or the climate is relatively warmer, humid and wind erosion is stronger in the depositional period of Eq34-10 rhythmite. The sedimentary water of these two sets of strata are in reductive environment, and the lake water may be deeper during the deposition period of Eq34-10 rhythmite, which is more conducive to the accumulation and preservation of organic matter. Therefore, it is inferred that Eq34-10 rhythmite has more exploration potential.