摘要
东濮凹陷是渤海湾地区一个典型的盐湖盆地,其古近系沙河街组发育多套盐岩.通过对古近系锶、硫、氧同位素组成特征的研究,讨论了古近系盐类沉积的成因及当时的古环境.研究表明:(1)东濮凹陷古近系的盐岩为陆相成因而并非来源于海水的侵入,其湖水锶同位素的主要控制因素为高87Sr/86Sr(0.720±0.005)的壳源硅铝质岩石;(2)东濮凹陷古近系盐岩中的δ34S((28～33)×10-3)普遍偏高且大于现代海相蒸发盐中的δ34S(20×10-3),表明盐类形成时的沉积环境对硫酸盐是封闭的,而对H2S是开放的;(3)锶和氧的同位素变化特征表明:东濮凹陷在由Es4上段向Es3上段过渡时气候较为湿润,降雨量逐渐增大,导致δ18O的降低和87Sr/86Sr值的升高;而由Es3上段向Es1段过渡时,气候骤然变得干旱,导致降雨量减小,蒸发量增大.
Dongpu depression is a typical saline lake basin in the Bohai Bay region. Many sets of halites have been deposited in the Shahejie Formation of Paleogene, The genesis of halites and the paleoenvironment are considered, based on the study of strontium, sulfur and oxygen isotopic composition characteristics of the Paleogene halites. The research results are as follows: (1) The halites of Paleogene of Dongpu depression were formed form continental lake water and not from the invasion of sea water. The composition of strontium isotopes was mainly controlled by the silicon-aluminum rock with a higher value of 87Sr/86Sr(0.720±0.005); (2) The value of δ34((28-33) × 10-3) of Paleogene halites of Dongpu depression was higher than that of the marine evaporate (20×10-3), which indicates that the sedimentary environment was closed to sulfate and open to sulfurated hydrogen; (3) The variation of strontium and oxygen isotope compositions show that from the upper Es4 to the upper Es3 member, the paleoclimate was humid in the Dongpu depression, and rainfall gradually increased, which resulted in a decrease of δ18O and increase of 87Sr/86Sr; and from the upper Es3 to the Es1 member the paleoclimate became abruptly dry, which resulted in a decrease in rainfall and rapid evaporation.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
2005年第4期430-436,共7页
Earth Science-Journal of China University of Geosciences
基金
横向合作项目:"东濮凹陷盆地发育特征及其油气成藏机制研究".
