黑龙江省东部绥滨坳陷下白垩统泥岩稀土元素地球化学特征

REE geochemical characteristics of the Lower Cretaceous mudstone in Suibin Depression of eastern Heilongjiang Province

通过对滨参1井下白垩统泥岩的取样分析,认为黑龙江省东部绥滨坳陷下白垩统泥岩的稀土元素具如下地球化学特征:(1)各组泥岩的稀土元素球粒陨石标准化配分模式都表现出轻稀土相对于重稀土明显富集和具有明显负Eu异常的特点,但∑REE、∑LREE/∑HREE、LaN/YbN、LaN/SmN、GdN/YbN、Eu/Eu*、Ce/Ce*和(La/Yb)UCC等参数则显示出明显的不同,反映了泥岩形成时的物源有差别。滴道组和城子河组的物源可能主要为绥滨坳陷南部桦南隆起地区的花岗岩、东南部宝清地区的沉积岩和东部东三江盆地的沉积岩;穆棱组和东山组物源可能主要为绥滨坳陷东南部宝清地区的沉积岩和东部东三江盆地的沉积岩。在穆棱组和东山组沉积期,还可能有来自下地壳或幔源的深部物质加入,导致物源发生了很大的变化。(2)Ce/Ce*和Ceanom指数显示绥滨坳陷早白垩世各组泥岩的古环境均为还原环境,对油气生成十分有利。(3)绥滨坳陷早白垩世为大陆边缘环境,其构造演化过程为活动—稳定—活动。

Based on analyses of the sampled mudstone of Well Bincan 1, the REE geochemical characteristics of the Lower Cretaceous mudstone of Suibin Depression in eastern Heilongjiang Province are described. The results indicate： （1） The LREE content obviously enriches compared with the HREE content and with negative Eu anomalies shown in the chondrite aerolite standard pattern of the mudstone. However, the parameters such as the ∑REE content, ∑LREE/∑HREE, LaN/YbN, LaN/SmN, GdN/YbN, Eu/Eu^＊ , Ce/Ce^＊ and （La/Yb）ucc ratios are quite different, which reflects the mudstone is from different provenance. The provenance for the Didao and Chengzihe Formations may be the granites in the Huanan Uplift south to the Suibin Depression, the sedimentary rocks in Baoqing area southeast to the depression and the sedimenlar？ rocks in the Dongeanjiang Basin east to it. The provenance of the Muleng and Dongshan Formations may be the sedimentary rocks in Baoqing area soulheast to the Suibin Depression and in the Dongsanjiang Basin east to it. During the deposition of the Muleng and Dongshan Formations, some materials may be from the deep lower crust and the mantle and leads to the great change of provenance. （2） The Ce/Ce^＊ and Ceanom indexes indicate that the palaeoenvironment of the Early Cretaceous mudstone in the Suibin Depression was a reduction environment and is profitable for the oil and gas formation. （3） In the Early Cretaceous, the Suibin Depression was a continental margin selling, with a tectonic evolution from .active setting, through stable setting to active selling.