松辽盆地北部地层水同位素特征及其地质意义

盆地流体是沉积盆地中非常活跃的因子，盆地流体的水文地球化学特征主要是受控于流体-岩石相互作用。本文以松辽盆地北部为研究对象，基于地层水的水文地球化学特征、锶-氢-氧同位素数据分析，初步探讨了水-岩反应与锶-氢-氧同位素的关系。这一研究对于丰富同位素示踪、水-岩相互作用等基础理论具有重要研究意义。分析表明，位于盆地西部地区地层水明显受到古大气降水的影响，中央凹陷地区δ18O正偏移可能是由水岩作用加强引起的。地层水为大气水与原生沉积水的混合，较轻的δD值反映出原始沉积水属陆相沉积水。地层水的87Sr/86Sr值略低而Sr2+含量又较高，是高87Sr/86Sr值流体端元与低87Sr/86Sr值流体端元的混合，即地表来源水与深部水的混合，也更多地受到高Sr2+含量低87Sr/86Sr值的火山-地热水等幔源深部水的补给。

Isotopic Characteristics of Formation Waters in the North of Songliao Basin and Its Geological Significances

The basin fluid is the very active factor in the sedimentary basins.The hydrogeochemistry is mainly controlled by fluid rock interaction.The source and genesis of the formation water are very complex.It is difficult to determine the genesis and source just according to the general component ions concentration and the interrelationship of ions.In this case,it is necessary to combine the trace elements and isotopic components to explain the genesis and source of the formation water.Applying isotopic chemistry method to research the formation water,in order to find the source,carry out the intensity of water-rock interaction,trace fluid flow direction,and compute the paleotemperature,age and residence time of the basin fluid.Based on hydrogeochemical characters of formation water and analysis of Sr-D-O isotope data,this article researches on the northern area of Songliao Basin,discusses the relationship of water-rock interaction and Sr-D-O isotope.It is of great theoretical significance for the isotope tracers in the enrichment of water-rock interaction.The result of the hydrogen-oxygen isotope testing suggests that formation water in the western area is evidently influenced by the ancient precipitation,and the positive excursion of the δ18O in the central depression is probably caused by the strengthing of water-rock interaction.The formation water is a mixture of meteoric water and primary sedimentary water,the slight value of the δD reflects the original sediment belongs to the continent depositional water.In the groundwater,the concentration of Sr2+ increases with TDS,Sr comes from the dissolution of rock dissolved by groundwater.The groundwater from Quantou Group(K2q) and Yingcheng Group(K1yc) has same character as the continent depositional water.Meanwhile,the groundwater from Qingkoushan Group shows the character of the sea depositional water obviously.The groundwater from Quantou Group and Yingcheng Group shows the character of the continent depositional water obviously.The distribution range of 87Sr/86Sr values from different formation water is concentrated,and has homologue.In all salt rocks,except those from Quantou Group,the distribution range of 87Sr/86Sr values from different formation rock is also concentrated,and has the same type of source.The salt rocks from Quantou Group are from distinct source and the higher value of 87Sr/86Sr should be inflected by the silicon-aluminium rock from the crust source.The 87Sr/86Sr value of formation water is slightly lower but the concentration of Sr2+ is higher,the formation water is a mixture of high 87Sr/86Sr value fluid end member and low 87Sr/86Sr value fluid end member-a mixture of surface source water and deep formation water,which is also obtained from mantle deep water like high Sr2+ value and low 87Sr/86Sr value volcanic geothermal water.