PY-GC, PY-GC-MS ANALYSES OF SOURCE ROCKS FROM ZHANHUA DEPRESSION AND THEIR GEOCHEMICAL SIGNIFICANCE

The source rocks from the first,third and fourth sections of Shahejie formation of Zhanhua depression have been analyzed by PY-GC and PY-GC-MS in this study and a detective method of multiple ions is employed to determine the triterpanes and triterpenes in the source rocks. The pyro-chromatograms of the source rocks of Zhanhua depression show that the distribution of n-alkane/n-alkene doublets is broad and that the first section and third section of the Shahejie formation have a n-alkane/n-alkene doublet distribution with odd over even preference and higher Pr/Ph ratio. On the contrary,the pyro-chromatogram of the forth section has n-alkane/n-alkene doublet distribution with an even over odd prefeence and lower Pr/Ph ratio. Thus, the fourth section of Shahejie formation is suggested as a saline lake sedimentation with reducing environment and that these indexes, such as n-alkane/n-alkene doublets distribution and Pr/Ph ratio, etc., can be used as the criteria of a sedimentary envirnment. The PY-GC, PY-GC-MS chromatograms of the source rocks of Zhanhua depression show that the insoluble organic matters, such as prist-l-ene/n-C17, C30 Ho-pane, 17β(H(21α(H)/17α(H)21β(H), C₂₇Hopane 17β(H)/17a(H) C₂₇Hopene/C₂₇ 17α(H)Hopane, etc. decrease with increasing maturity of the samples, and that C₃₁ Hopane, 17α(H)21β(H)22S/17α(H)21β(H) 22(R+S)% increase with increasing maturity of the samples/ As a result, they demonstrate that these parameters can be employed to measure the maturity of organic matters in sediment. However, the result of the present study has shown that PY-GC and PY-GC-MS are useful means to evaluate the deposition environment of source rocks and its maturity.