【摘要】 综合地震资料解释、岩石矿物学观察以及地球化学分析结果,认为四川盆地中部中二叠统栖霞组、茅口组白云岩为构造热液白云石化成因,具有以下典型特征:①白云岩单层厚度较大,多呈透镜状产出,横向连续性差,钻遇井附近多伴有走滑断裂发育,白云岩层段在对应的地震剖面上见"下凹"反射特征;②基质白云岩多呈中-粗晶,其缝洞中见具有波状消光特征的填隙鞍状白云石,并发育大量的角砾岩,角砾岩间充填白色的白云石,形成斑马构造;③基质白云岩与填隙鞍状白云石的均一温度较白云石化作用时地层的温度要高5℃以上,分别为105.8～159.6℃及113.2～138.6℃,同时二者还具有偏负的氧同位素特征(-7.64‰～-7.95‰)以及高87Sr/86Sr值(0.708 369～0.709 684)。构造热液白云岩的发育和分布受走滑断裂控制,若与上覆致密灰岩地层有机配置,可以形成良好的岩性圈闭。更多还原

【Abstract】 Integrated with seismic profile interpretations,Petro-mineralogic observations and geochemical analyses,the present paper proposed that dolomites in the Middle Permian Qixia Formation-Maokou Formation of the central Sichuan Basin are of a structure-controlled hydrothermal origin.The characterization of the dolomites showed that:1) they are relatively thicker in a single layer,commonly in lenticular form,poor in lateral continuity,sometimes accompanied with developed strike-slip faults and having a "concave-down" reflection in seismic sections corresponding to dolomite intervals concerned;2) matrix dolomites composed mainly of meso-or macro-crystalline grains have the saddle-shaped dolomite with undulatory extinction stuffed in their fractures and vugs,where a large amount of breccias with white dolomites filled between them develops,forming zebralike fabrics;and 3) homogenization temperatures of matrix and interstitial saddle-shaped dolomites are commonly 5℃ higher than those of strata during dolomitization,ranging between 105.8~159.6℃ and 113.2~138.6℃,respectively.In addition,they show lighter oxygen isotopes(-7.64‰~-7.95‰) and higher 87Sr/86Sr ratios(0.708 369~0.709 684).The development and distribution of structure-controlled hydrothermal dolomites are dominated by strike-slip faults.There would be a good lithologic reservoir if hydrothermal dolomites combine well with overlying tight limestones.更多还原