地质学报2017，Vol.91Issue(2)：453-464,12.
藏北羌塘上侏罗统—下白垩统胜利河油页岩单体烃碳同位素研究
Compound-Specific Carbon Isotopic Compositions of the Upper Jurassic-Lower Cretaceous Shenglihe Oil Shales in the Qiangtang Basin, Northern Xizang
摘要
Abstract
The Upper Jurassic-Lower Cretaceous Shenglihe oil shales are located in about 30-kilometer-long NWW-SEE-trending the transitional belt between north Qiangtang basin and central uplift belt.Abundant biomarkers,including n-alkanes,isoprenoid,steranes,terpanes and aromatics,have been detected by GC-MS from the oil shales.The n-alkanes of marine oil shale samples show a dominance of low carbon molecular components (∑C21-/∑C22+ ranges from 0.78 to 3.43 with an average of 1.57) with highest peaks of nC17 or nC19.OEP values of the n-alkanes show no odd-even carbon dominance of 0.77 ～ 1.12 (averaging 0.95).Pr/Ph ratios range from 0.33 to 1.28 (averaging 0.71) with most Pr/Ph less than 1.0,showing a weak a weak phytane dominance.The terpanes distribution abundances of oil shale samples are pentacyclic terpanes ＞ tricyclic terpanes＞ tetracyclic terpanes.he steranes presents an asymmetric V-shaped distribution with C27-steranes ＞C28-steranes ＞ C29-steranes.All these characteristics indicate organic matters in marine oil shale are of algae and bacterial origin.The carbon isotopic δ13C compositions of n-alkanes range from-29.89‰ to-23.73‰ with an average of-26.99‰ and show an horizontal distribution with slight decline.The δ13C of pristine and phytane of isoprenoid hydrocarbon range from -30.72‰ to-24.57‰ with an average of-28.39‰ and range from-29.87‰ to-27.24‰ with an average of-28.52‰ respectively.The n-alkanes are enriched in δ13C by 0.02‰-3.66‰ and 0.37‰ -3.69‰ related to pristine and phytane respectively.The unconventional abnormally positive δ13C of n-alkanes maybe caused by blooming of dinofragellates or colonial green algae (Botryococus) during that period.Microscopic observation reveals two types of organic matters:type Ⅱ1 (humic mud) and type Ⅱ2 (sapropelic-humic).Vitrinite reflectances of kerogen range from 0.37％ to 0.9％ with an average of 0.55％,indicating that organic matter of oil shale underwent a stage of immature to low maturation.Thermolysis peak temperature,sporo-pollen colour index,maturity parameter of n-alkanes biomarker and alkylphenanthrene parameter of aromatics also confirmed that the organic matter of oil shale was at the stage of immature to low maturation.关键词
油页岩/单体烃碳同位素/成熟度/羌塘盆地Key words
oil shale/compound-specific carbon isotopic compositions/maturity/Qiangtang basin引用本文复制引用
李忠雄,何江林,谢尚克..藏北羌塘上侏罗统—下白垩统胜利河油页岩单体烃碳同位素研究[J].地质学报,2017,91(2):453-464,12.基金项目
本文为国家油气专项“青藏高原油气资源战略选区调查与评价”(编号XQ-2004-06)资助成果. （编号XQ-2004-06）
