The Upper Cambrian dolostones in the Tarim Basin are interpreted to be intensely altered by hydrothermal fluids during the burial diagenesis, and the saddle dolomite filled in fractures is commonly considered as hydrothermal origin. In this study, the saddle dolomite samples from drillhole SNP1 and the Quruqtagh area are sampled, and C-O-Sr isotopic compositions and in-situ trace elemental analyses are employed to check their origin. Replaced dolomites with finely crystal size and coarsely crystal size (RD1 and RD2, respectively), and saddle dolomite cements filled in vugs and fractures (VSD and FSD, respectively) are identified in the Well SNP1. Stylolites crosscut RD1 and RD2 dolomites. KZ-SD is the saddle dolomite in hydrothermal dolostone geobodies in the Quruqtagh area, and shows coarsely crystal size up to 1 cm and wavy extinctions. RD1, RD2 and FSD dolomites show similar δ¹³C_VPDB values of − 1.99 to − 0.73‰, and similar ⁸⁷Sr/⁸⁶Sr ratios of 0.70868–0.70905. RD1 and RD2 dolomites show δ¹⁸O_VPDB values of − 8.74 to − 5.29‰ and of − 10.22 to − 9.20‰, respectively. The δ¹⁸O_VPDB values of FSD range from − 10.94 to − 10.16‰. RD2, VSD and FSD dolomites show Fe concentrations of 154.76–464.65 ppm, Mn concentrations of 15.74–55.93 ppm and REE concentrations of 1.29–4.61 ppm. The REEY profiles of RD2, VSD and FSD dolomites are characterized by flat to convex patterns with slightly MREE enrichment, and no Ce, Eu and Y anomalies. KZ-SD dolomite shows Fe concentrations of 1081.55–1206.35 ppm, Mn concentrations of 427.25–474.38 ppm and REE concentrations of 12.97–23.64 ppm. The C–O–Sr isotopic compositions and REEY features of RD2, FSD and VSD indicate that saddle dolomites filled in vugs and fractures in the Well SNP1 are formed from redistribution of precursor dolostones, and indicate that RD2 may formed by recrystallization during burial diagenesis.

塔里木盆地上寒武统白云岩被解释为在埋藏成岩过程中受到热液流体的强烈蚀变，裂缝中充填的鞍状白云岩通常被认为是热液成因。本研究对钻孔 SNP1 和 Quruqtagh 地区的鞍状白云岩样品进行取样，并采用 CO-Sr 同位素组成和原位微量元素分析来检查其来源。在 SNP1 井中识别出具有细晶体尺寸和粗晶体尺寸的替换白云岩（分别为 RD1 和 RD2），以及充填在孔洞和裂缝中的鞍状白云岩胶结物（分别为 VSD 和 FSD）。柱状石横切 RD1 和 RD2 白云岩。KZ-SD 是 Quruqtagh 地区热液白云岩地质体中的鞍状白云岩，晶体尺寸粗达 1 cm，呈波浪状消光。RD1,¹³ C _VPDB值为 - 1.99 至 - 0.73‰，类似的⁸⁷ Sr/ ⁸⁶ Sr 比率为 0.70868-0.70905。RD1 和 RD2 白云岩的 δ ¹⁸ O _VPDB值分别为 - 8.74 至 - 5.29‰ 和 - 10.22 至 - 9.20‰。δ ¹⁸ O _VPDBFSD 的值范围从 - 10.94 到 - 10.16‰。RD2、VSD 和 FSD 白云岩的 Fe 浓度为 154.76–464.65 ppm，Mn 浓度为 15.74–55.93 ppm，REE 浓度为 1.29–4.61 ppm。RD2、VSD和FSD白云岩的REEY剖面特征为平坦到凸形，MREE略微富集，没有Ce、Eu和Y异常。KZ-SD 白云石显示 Fe 浓度为 1081.55–1206.35 ppm，Mn 浓度为 427.25–474.38 ppm，REE 浓度为 12.97–23.64 ppm。RD2、FSD和VSD的C-O-Sr同位素组成和REEY特征表明，SNP1井孔洞和裂缝中充填的鞍状白云岩是由前驱白云岩重新分布形成的，表明RD2可能是在埋藏成岩作用过程中再结晶形成的。