Comparative Analysis of Testing Methods for the Determination of Calcite in Carbonate Rocks (Limestones) from the Mensanguime River, Morona Santiago, Ecuador

Abstract

Outcrops of interbedded limestones and calcareous shales of the Napo Formation (Cretaceous) exposed along the Mensanguime River pose an analytical challenge for accurately quantifying their carbonate content. This study compares seven laboratory methods, calcination, direct and indirect titration, acid washing, wavelength‑dispersive X‑ray fluorescence (WD‑XRF), atomic absorption spectrometry (AA), and inductively coupled plasma optical emission spectrometry (ICP‑OES), and uses X‑ray diffraction (XRD) to confirm the carbonate mineralogy. Statistical tests (Shapiro–Wilk) showed that the results follow a normal distribution. The findings underscore the need to consider the uncertainty sources specific to each technique, as well as their technical and economic feasibility, when selecting the optimal protocol for characterizing carbonates in complex geological matrices.