Geochemical Trends of CaO and MgO in Marine Carbonates: Insights from XRF Analysis

Abstract

Abstract The analysis of calcium oxide (CaO) and magnesium oxide (MgO) concentrations in marine carbonates using X-ray fluorescence (XRF) offers important new perspectives on depositional settings and diagenetic processes. The geochemical patterns of CaO and MgO in limestones and dolostones were investigated using XRF spectrometry to determine the primary depositional settings and establish linkages between the oxide ratios and sedimentological features. XRF tests reveal a negative connection between CaO and MgO values, implying dolomitization over time from stratigraphic and geographical changes in samples obtained from a marine sedimentary basin in Southeast Sulawesi, Indonesia. Dolomitized samples exhibit lower CaO values (30.0–42.5%), and rising MgO concentrations (4.5–15.5%), whereas limestone samples show high CaO concentrations (45.0–54.5%). Stratigraphic changes in the CaO-MgO ratios indicate either limited dolomitization in lower units, suggestive of open sea deposition, or elevated dolomitization in higher intervals, presumably arising from Mg-rich diagenetic fluids. Analyzing CaO-MgO ratios concerning other oxides (SiO₂, Al₂O₃) helps to better understand depositional habitats; larger Ca/Mg ratios imply shallow marine settings and lower ratios indicate confined environments with major siliciclastic input. Utilizing stratigraphic and facies analyses combined with XRF-derived geochemical proxies, knowledge of carbonate deposition and subsequent post-depositional processes is enhanced, thus underscoring the interaction between main marine deposition and secondary diagenetic modification in the control of CaO-MgO distribution within carbonate successions.

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