胶莱盆地止凤庄组、红土崖组微量元素地球化学特征及古环境分析

Geochemical characteristics and paleoenvironmental analysis of trace elements of Zhifengzhuang and Hongtuya formations in Jiaolai basin

微量元素对沉积环境变化具有较高的敏感度,微量元素分析是研究沉积环境的有效方法。胶莱盆地止凤庄组和红土崖组分别属莱阳群和王氏群,多以砂岩和砂砾岩为主,见泥岩夹层。通过实测剖面和现场取样,采用ICP-MS测定样品的微量元素,根据微量元素、比值等地球化学指标,探讨止凤庄组、红土崖组的沉积环境。Sr/Ba、Rb/K值及剖面地质特征表明止凤庄组、红土崖组具河流沉积特征;止凤庄组与红土崖组样品的Sr/Cu分别为10.05~23.32和5.50~9.82,表明止凤庄组形成于干热气候,红土崖组形成于温暖湿润气候;止凤庄组与红土崖组的V/Cr分别为0.32~2.23和0.39~2.14,Ni/Co分别为2.97~4.91和2.22~6.71,U/Th分别为0.11~0.14和0.13~0.14,δU分别为0.51~0.60和0.55~0.60,V/(V+Ni)分别为0.42~0.69和0.49~0.59,均表明止凤庄组、红土崖组形成于氧化环境,与其红色主色调特征相一致。

The trace elements of sedimentary rocks have high sensitivity to hydrological changes of sedimentary environment and are often used as an effective method to study sedimentary environment.Zhifengzhuang and Hongtuya formations in Jiaolai basin belong to Laiyang group and Wangshi group respectively,which are mainly composed of sandstone and glutenite with mudstone interlayers.The profile in the study area was measured and the field sampling was conducted.Then ICP-MS was used to determine the trace elements.Based on the geochemical indicators such as the content and ratio of trace elements,the palaeoenvironment of Zhifengzhuang and Hongtuya formations were investigated.The Sr/Ba and Rb/K values and the geological features of profiles indicate that the strata of both Zhifengzhuang and Hongtuya formations shows fluvial sedimentary characteristics.The Sr/Cu values of Zhifengzhuang and Hongtuya formations are 10.05~23.32 and 5.50~9.82 respectively,indicating that Zhifengzhuang formation formed in a dry and hot climate while Hongtuya formation formed in a warm and humid climate.The V/Cr values of the two formations are 0.32~2.23 and 0.39~2.14 respectively,and the Ni/Co values are 2.97~4.91 and 2.22~6.71 respectively.The U/Th values are 0.11~0.14 and 0.13~0.14 respectively,theδU values are 0.51~0.60 and 0.55~0.60 respectively.The V/(V+Ni)values are 0.42~0.69 and 0.49~0.59 respectively.These values indicate that the strata of both Zhifengzhuang and Hongtuya formations formed in the oxidation environment,were consistent with the major red color of the target layer.