C-O Isotopes in Carbonates as an Exploration Tool for Pb-Zn MVT Deposits in Saudi Arabia: A Case Study on the Mydian Terrane

Abstract Mississippi Valey Type (MVT) deposits are significant sources of lead and zinc, hosted in dolostone and limestone within platform carbonate sequences. These deposits are characterized by a lack of magmatic source, deriving metals from basinal brines. Carbonate-hosted ore deposits present exploration challenges due to limited mineralogical alteration halos. However, stable carbon and oxygen (C-O) isotopes in surrounding carbonates can reveal extensive alteration zones, potentially spanning for long distances, serving as indicators of ore body proximity. Studies have shown a connection between MVT deposits and petroleum systems, with some Pb-Zn deposits coexisting with oil and gas reservoirs, suggesting a genetic link between mineralization processes and hydrocarbon accumulation. This study explores the application of C-O isotope data as a mineral exploration tool within the geological framework of Saudi Arabia. The research focused on Miocene carbonates in the Mydian Terrane, which was chosen because they are similar in age to the Jabal Dhaylan deposit, the only recognized MVT deposit in Saudi Arabia. It's important to note that MVT deposits typically occur in clusters or belts, often containing multiple deposits. The methodology involved fieldwork, sampling, thin sections, multiple geochemical analyses using stable isotope mass spectrometry to obtain δ13C and δ18O values, QEMSCAN, XRD, and XRF. The main results from C-O isotope data reveal δ18O values ranging from -0.481‰ to -12.093‰ (VPDB) and δ13C values from -5.069‰ to 0.673‰ (VPDB), with some samples showing significant isotopic depletion compared to typical marine carbonate diagenesis. This initial research explores the relationship between C-O isotope variations in carbonate rocks and the potential presence of economically important deposits. The presence of hydrothermal dolomite could indicate proximity to an MVT deposit or hydrothermal diagenetic influence. The sampling needs to be improved, and complementary geochemical analysis to constrain the temperature of this fluid. The results may improve the identification of potential new Pb-Zn-Cu mineralization sites.