济阳拗陷第三纪玄武岩的氧同位素

研究了山东刘阳拗陷29个第三纪玄武岩样品的氧同位素组成。结果表明，这些玄武岩的全岩氧同位素组成变化明显，δ^18○值为6．3‰－12．2‰。其中，蚀变轻微的晚第三纪玄武岩的δ^18○值为6．3‰－7．9‰，与正常大陆玄武岩的值（5．0‰－7．4‰）相似；而蚀变明显的早第三纪玄武岩的δ^18○值为6．3‰－12．2‰，并且90％以上样品的δ^18○值都大于7．5‰。结合岩石学与岩石化学研究，是第三纪玄武岩δ^18○值不同程度升高是由低温雨水热液蚀变（碳酸盐化）作用造成的。

Study on Oxygen Isotopic Compositions of Tertiary Basalts in Jiyang Depressional Basin, Shandong Province

Oxygen isotopic compositions of 29 Tertiary basalt samples from the Jiyang depressional basin are reported in this paper. The δ18O values of these basalts mostly range from 6.3‰ to 12.2‰. The Late Tertiary basalts with weak alteration haveδ18O values of 6.3‰0～7.9‰, which are similar to those of Late Tertiary basalts from central and eastern Shandong and are essentially in the range of normal continental basalts. However, the Early Tertiary basalts with evident alteration haveδ18O values of 6.7‰～12.2‰, more than 90% samples of which have δ18O values greater than 7.5‰. The obvious change ofδ18O values for Early Tertiary basalts not only occurs in the samples of different stratigraphic units, such as Shasan Member(Es3), Shasi Member (Es4)and Kongdian Formation(Ek), but also in the samples of the S31TIe stratigraphic unit collected from the same drill hole. Combined with the petrological and petrochemical data, it is clear that the increase ofδ18O values for the Early Tertiary basalts in different degrees was mainly caused by meteoric-hydrothermal alteration (carbonatization) at a lower temperature.