Molecular and carbon isotopic compositions of gas inclusions of deep carbonate rocks in the Tarim Basin

作     者：Paul Farrimond 

作者机构：Fossil Fuels and Environmental Geochemistry Drummond Building University of Newcastle upon Tyne Newcastle upon Tyne NE17RU UK 

出 版 物：《Science China Earth Sciences》 (中国科学（地球科学英文版）)

年 卷 期：2004年第47卷第5期

页      面：445-452页

核心收录：

学科分类：0709[理学-地质学] 070901[理学-矿物学、岩石学、矿床学] 07[理学] 

基　　金：the Important Direction Projects of Knowledge Innovation in Resource and Environment Field, the Chinese Academy of Sciences(KZCX2-111) 'Light of the West' Project of the Chinese Academy of Sciences 

主　　题：Tarim Basin, deep carbonate rock, gas inclusion component, carbon isotope. 

摘      要：Gaseous components of gas inclusions in deep carbonate rocks (5700 m) from the Tacan 1 well were analyzed by online mass spectrometry by means of either the stepwise heat-ing technique or vacuum electromagnetism crushing. The carbon isotopic compositions of gases released by vacuum electromagnetism crushing were also measured. Although the molecular compositions of gas inclusions show differences between the two methods, the overall charac-teristics are that gas inclusions mainly contain CO2, whilst hydrocarbon gases, such as CH4, C2H6 and C3H8, are less abundant. The content of CO is higher in the stepwise heating experi-ment than that in the method of vacuum electromagnetism crushing, and there are only minor amounts of N2, H2 and O2 in gas inclusions. Methane d 13C values of gas inclusions in Lower Ordovician and Upper Cambrian rocks (from 5713.7 to 6422 m; -52—63) are similar to those of bacterial methane, but their chemical compositions do not exhibit the dry character in comparison with biogenic gases. These characteristics of deep gas inclusions may be related to the migration fractionation. Some deep natural gases with light carbon isotopic characteristics in the Tazhong Uplift may have a similar origin. The d 13C1 values of gas inclusions in Lower Cam-brian rocks (7117—7124 m) are heavier (-39), consistent with highly mature natural gases. Carbon isotopic compositions of CO2 in the gas inclusions of deep carbonate rocks are similar (from -4 to 13) to those of deep natural gases, indicating predominantly an inorganic origin.