CAJ | 학술논문

通过主微量元素、稀土元素及碳、氧、锶同位素特征分析，系统研究鄂尔多斯盆地靖边气田西侧奥陶系马家沟组马五段中组合白云岩地球化学特征及成因。样品分析结果表明：中组合白云岩MgO和CaO含量呈负相关性，Mg/Ca值总体较高；总体具有高Fe、较高Mn和低Sr、Na含量特征，部分白云岩Fe、Mn含量相对较低，Na含量相对较高；稀土元素含量总体很低，且具相似稀土元素配分模式，轻稀土元素富集，重稀土元素亏损，具明显 Eu 负异常和弱 Ce负异常；δ13C值与同期海水值一致，多数白云岩δ18O值较同期海水值偏负；少数87Sr/86Sr值与同期海水值接近，多数显著偏正。结合区域地质背景及上述特征，认为马五段中组合白云岩很可能主要为渗透回流白云石化成因，同时在后期广泛叠加了埋藏白云石化作用。靖西东部地区为有利储集层发育区且可向东大范围拓展。图11表3参35
통과주미량원소、희토원소급탄、양、송동위소특정분석，계통연구악이다사분지정변기전서측오도계마가구조마오단중조합백운암지구화학특정급성인。양품분석결과표명：중조합백운암MgO화CaO함량정부상관성，Mg/Ca치총체교고；총체구유고Fe、교고Mn화저Sr、Na함량특정，부분백운암Fe、Mn함량상대교저，Na함량상대교고；희토원소함량총체흔저，차구상사희토원소배분모식，경희토원소부집，중희토원소우손，구명현 Eu 부이상화약 Ce부이상；δ13C치여동기해수치일치，다수백운암δ18O치교동기해수치편부；소수87Sr/86Sr치여동기해수치접근，다수현저편정。결합구역지질배경급상술특정，인위마오단중조합백운암흔가능주요위삼투회류백운석화성인，동시재후기엄범첩가료매장백운석화작용。정서동부지구위유리저집층발육구차가향동대범위탁전。도11표3삼35
The trace elements, rare earth elements (REE), carbon and oxygen isotopic compositions and strontium isotopes were analyzed to study systematically the geochemical characteristics and origin of the middle assemblage dolomites from the Ordovician Majiagou Formation Member 5 in the Jingxi area (the west of Jingbian Gas Field). The analytical results of samples demonstrate that the MgO and CaO contents of the middle assemblage dolomite are negatively correlated, and the Mg/Ca values are high;the dolomites are characterized by high Fe content, relatively high Mn content and low Sr and Na content, while part dolomites have low Fe and Mn content but high Na content; the dolomites have very low REE content and similar REE distribution patterns, which are generally characterized by enrichment of light REE, losses of heavy REE, obviously negative anomaly of Eu and weak negative anomaly of Ce;The δ13C values of dolomites are consistent with those of the coeval seawater, while most of the δ18O values of dolomites are more negative than those of the coeval seawater; most of the 87Sr/86Sr values of dolomites are significantly higher than those of the coeval seawater while only a few are close to those of the coeval seawater. Combined with the geological setting and geochemical characteristics of the middle assemblage dolomites, the middle assemblage dolomites of the Majiagou Member 5 are probably the origin of seepage reflux dolomitization, and were superimposed by burial dolomitization during the burial period. The eastern part of the Jingxi area is favorable reservoir development area, the favorable area can extend eastward.