A kind of particular rock type "leopard limestone" is widely distributed over Middle Permian Qixia Formation in the Northwest of Sichuan Basin. Based on the lithologic characteristics and micro-area and multi-parameter experimental analysis of samples taken from outcrops and drilling cores, the authors study the characteristics and genesis of the leopard limestone. The authors think that the leopard limestone consists of porphyritic dolomite and host bioclastic limestone. The genesis of the leopard limestone is generally because of uneven dolomization. The special pattern of the leopard limestone could be connected with the exposure in late Qixia period. After exposure, the bioclastic limestone suffered karstification and the formed fracture-cavity system controlled the distributed pattern. The "leopard limestone" could be caused by the dolomization fluid from bottom to top, because at the end of the migration pathway, porphyritic dolomite was formed by metasomasis. Dolomization happened after consolidation diagenesis, the buried depth was shallow, and the origin fluid of dolomization could have something to do with hydrothermal fluids.%四川盆地西北部中二叠统栖霞组之上广泛分布着一套特殊的岩石类型——“豹斑灰岩”.以钻井岩心及露头剖面样品的镜下岩石学特征为基础,以微区多参数实验分析数据为依据,对川西北地区栖霞组的豹斑灰岩进行了研究.结果表明,豹斑灰岩由白云岩斑块加宿主生屑灰岩所构成；豹斑灰岩是由于白云石化不均匀引起的；豹斑的形态与栖霞晚期发生的暴露有关,生屑灰岩暴露地表后遭受溶蚀作用,所形成的缝洞系统控制了豹斑灰岩的分布形态.“豹斑灰岩”的成因是由于白云石化流体自下而上运移,在向上运移通道末端形成以交代作用为主的斑块状白云石,其形成时期应为成岩之后的浅埋藏时期,且白云石化流体可能与热液有着一定的关系.
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