Carbonates of the Salitre Formation, Irecê Basin, Brazil, have been the focus of extensive stratigraphic and structural studies for several decades. Besides hosting phosphorites deposits, these rocks are analogues to fractured and certified oil reservoirs, such as those of the Cretaceous pre-salt oil system offshore Brazil. The present study presents an integration of X-Ray Diffraction (XRD), Quantitative Evaluation of Minerals by Scanning Electron Microscopy (QEMScan), Optical Petrography, Cathodoluminescence (CL), and Charge Contrast Imaging (CCI) data that allows a high-resolution characterization of the mineralogy within the carbonate units. In addition, we also present carbon and oxygen stable isotope data to identify possible origins of the associated fluids. The mineral characterization revealed that calcite (50–70%), quartz (20–30%) and dolomite (10–20%) are the main post-sedimentary mineral phases found in veins, vesicle structures and cement of the carbonate units. The mineral phases of veins were formed by the interaction with hydrothermal fluids, which had an important role in the dissolution, karstification, and remobilization of carbonate units. Isotopic analysis shows that δ13C and δ18O are more negative in veins and vesicles when compared to host rock, indicating that there is no effective isotopic exchange between the host rock and the filled structures and that these structures were filled with hydrothermal fluids from an external source.

几十年来，巴西 Irecê 盆地 Salitre 组的碳酸盐岩一直是广泛的地层和构造研究的重点。除了拥有磷矿矿床外，这些岩石还类似于裂隙和经过认证的油藏，例如巴西近海白垩纪盐下石油系统的油藏。本研究综合了 X 射线衍射 (XRD)、扫描电子显微镜 (QEMScan)、光学岩相学、阴极发光 (CL) 和电荷对比成像 (CCI) 数据，可进行高分辨率表征碳酸盐单元内的矿物学。此外，我们还提供了碳和氧稳定同位素数据，以确定相关流体的可能来源。矿物特征表明方解石 (50–70%)、石英 (20-30%) 和白云石 (10-20%) 是在碳酸盐单元的脉、囊泡结构和胶结物中发现的主要沉积后矿物相。脉的矿物相是通过与热液相互作用形成的，对碳酸盐单元的溶解、岩溶和再迁移具有重要作用。同位素分析表明，与母岩相比，脉和囊泡中的 δ13C 和 δ18O 更负，表明母岩和填充结构之间没有有效的同位素交换，这些结构充满了来自外部的热液流体。对碳酸盐岩单元的溶解、岩溶和再迁移具有重要作用。同位素分析表明，与母岩相比，脉和囊泡中的 δ13C 和 δ18O 更负，表明母岩和填充结构之间没有有效的同位素交换，这些结构充满了来自外部的热液流体。对碳酸盐岩单元的溶解、岩溶和再迁移具有重要作用。同位素分析表明，与母岩相比，脉和囊泡中的 δ13C 和 δ18O 更负，表明母岩和填充结构之间没有有效的同位素交换，这些结构充满了来自外部的热液流体。