Shortwave infrared (SWIR) spectroscopy can be applied directly to analyze the mineral chemistry of raw or geologic materials. It provides diagnostic spectral characteristics of the chemical composition of minerals, information that is invaluable for the identification and quality control of such materials. The present study aims to investigate the potential of SWIR spectroscopy as an alternative quality control technique for the mineral chemistry analysis of Portland cement-grade limestone. We used the spectroscopic (wavelength position and depth of absorption feature) and geochemical characteristics of limestone samples to estimate the abundance and composition of carbonate and clay minerals on rock surfaces. The depth of the carbonate (CO₃) and Al-OH absorption features are linearly correlated with the contents of CaO and Al₂O₃ in the samples, respectively, as determined by portable X-ray fluorescence (PXRF) measurements. Variations in the wavelength position of CO₃ and Al-OH absorption features are related to changes in the chemical compositions of the samples. The results showed that the dark gray and light gray limestone samples are better suited for manufacturing Portland cement clinker than the dolomitic limestone samples. This finding is based on the CaO, MgO, Al₂O₃, and SiO₂ concentrations and compositions. The results indicate that SWIR spectroscopy is an appropriate approach for the chemical quality control of cement raw materials.

The presence of hydrocarbon seeps at the surface is indirect evidence of the presence of mature source rocks within a geological system at depth. Chemical changes in the environment of surface rocks caused by hydrocarbon seeps cause mineralogical alterations. To determine the nature of the alterations and the influences of lithology and type of seep, rock samples were collected from altered and unaltered evaporite and marly limestone formations in the Dezful embayment, southwest Iran. Reflectance spectroscopy, bulk rock/wet chemical analyses, and sulfur, carbon, and oxygen isotopic analyses were used to delineate surficial alterations and relate alterations to hydrocarbons seeping from underlying reservoirs. In addition, the boosted regression trees (BRT) method was used to predict the presence of alterations from spectral indices. Comparisons of geochemical data and spectral data of altered evaporites and altered marly limestones showed that the minerals within alteration facies have distinctive spectral, chemical, and isotopic signatures. Gas-induced alterations were characterized by the formation of gypsum and native sulfur and depletion in S34. The released H2S in natural gas reacted with gypsum in the evaporite sediments and calcite in the marly limestone formations, which led to precipitation of secondary gypsum and native sulfur. Oil-induced alterations were characterized by formation of secondary calcite and depletion in C13. The oxidation of seeping oil and reactions between this oil and host rocks caused precipitation of secondary calcite within both formations. The combination of fieldwork data and spectral-geochemical data showed a connection exists between surficial alterations and underlying petroleum reservoirs, which can be used in exploration campaigns.