鄂尔多斯盆地奥陶系白云岩碳氧同位素分析

ANALYSIS OF CARBON AND OXYGEN ISOTOPE ON THE ORDOVICIAN DOLOSTONES IN THE ORDOS BASIN

刘德良 孙先如 李振生 唐南安 谈迎 刘波

Liu Deliang Sun Xianru Li Zhensheng Tang Nanan Tan Ying Liu Bo

中国科技大学, 地球与空间科学院, 合肥, 230026 2. 安徽地质实验研究所, 合肥, 230001 3. 中国地质科学院, 西安地质矿产研究所, 西安, 710054

School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China 2. Institute of Geological Experiment of Anhui Province, Hefei, Anhui 230001, China 3. Xi'an Institute of Geology and Mineral Resources, Xi'an, Shannxi 710054, China

对鄂尔多斯盆地奥陶系白云岩成因类型与碳氧同位素的关系进行了研究。准同生白云岩碳氧同位素值重,δ13C介于0.639‰~-2.2‰之间,δ18O值介于-0.2‰~-8.668‰,产生于咸化水体;成岩白云岩的δ13C介于0.9‰~-3.2‰,δ18O介于-1.7‰~-7.607‰,产生于高镁咸化水体;深埋白云岩碳氧同位素值轻,δ13C介于0.580‰~-3.7‰,δ18O介于-6.88‰~-9.97‰,形成于温度较高、盐度较低、含镁亦较低的环境。白云岩中的碳酸盐脉δ13C集中在-1.00‰~-5.66‰,而灰岩中碳酸盐脉δ13C集中在-1.30‰~-8.65‰;碳酸盐脉氧同位素值较轻且变化较小,δ18O介于-10.66‰~-18.91‰,Z峰值集中在100和110,表明碳酸盐脉形成受到淡水淋滤。

In order to know the formation surroundings of the Ordovician dolostone that is Lower Paleozoic reservoir of natural gas in the Ordos Basin,the relationship between its genetic type and carbon and oxygen isotope is studied.Carbon and oxygen isotope of penecontemporaneous dolostone is heavy,whose δ13C value varies from 0.639‰ to -2.2‰ and δ18O value does from -0.2‰ to -8.668‰.The penecontemporaneous dolomite rock forms in saline water body.δ13C value of diagenetic dolostone varies from 0.9‰ to -3.2‰ and δ18O does from -1.7‰ to -7.067‰.The diagenetic dolostone froms in high-magnesian saline water body.Carbon and oxygen isotope of immerged dolostone is light,whose δ13C value varies from 0.580‰ to -3.7‰ and δ18O value does from -6.88‰ to -9.97‰.The formation surrounding of immerged dolostone is higher temperature,lower salinity and lower-magnesium.δ13C value of carbonate vein in dolostone most is from -1.00‰ to -5.66‰,while that in limestone most is from -1.30‰ to -8.65‰.Oxygen isotope of carbonate vein is lighter with narrow ranges,whose value varies from -10.66‰ to -18.91‰,and its Z value most is 100 and 110.Those indicate there was fresh-water leaching during formation of carbonate vein.

国家自然科学基金(40472074);国家重点基础研究规划项目(2001CB209133)

https://doi.org/10.11781/sysydz200602155