中文摘要：

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，δ^13C介于0．639‰-2．2‰之间，δ^18O值介于-0．2‰～-8．668‰，产生于成化水体；成岩白云岩的δ^13C介于0．9‰～0．2‰.δ^18O介于-1．7‰～-7．607‰，产生于高镁成化水体；深埋白云岩碳氧同位素值轻。δ^13C介于．580‰--3．7‰，δ^18O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δ^13C集中在-1．00‰～-5．66‰，而灰岩中碳酸盐脉δ＆13C集中在-1．30‰～-8．65‰；碳酸盐脉氧同位素值较轻且变化较小．δ^18O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。

英文摘要：

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 δ^13C value varies from 0. 639‰ to -2.2‰ and δ^18O value does from -0.2‰ to -8. 668‰. The penecontemporaneous dolomite rock forms in saline water body. δ^13C value of diagenetic dolostone varies from 0.9‰ to - 3.2‰ and δ^18O 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 δ^13C value varies from 0. 580‰ to -3.7‰ and δ^18O value does from -6.88‰ to -9.97‰. The formation surrounding of immerged dolostone is higher temperature, lower salinity and lower-magnesium. δ^13C 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.