CONSTRAINING THE ORIGIN AND EVOLUTION OF FLUIDS ON THE EAST KAIBAB MONOCLINE USING THE ISOTOPE GEOCHEMISTRY OF CARBONATES
Thermogravimetric analysis reveals that the samples’ carbonate concentrations range from 0.8 to 13.9% of the total sample mass. XRD analysis indicates that minerals in the EKM carbonates are primarily calcite and dolomite. Carbonate minerals precipitate in isotopic equilibrium with the water in which they form, and δ18Ocarbonate can therefore be used to determine δ18Ofluid during precipitation if a temperature is assumed. The δ18Ocarbonate values from EKM show a range of –20.6 to +0.9‰ (VPDB), indicating that minerals along the EKM precipitated from a combination of different fluid sources, different temperatures, or a combination of both. Individual carbonate crystals range from –0.6 to –13.3‰; bulk analyses of deformation band carbonates range from –20.3 to –1.5‰; whole-rock carbonates in undeformed matrices range from –17.7 to +0.9‰; and matrix values range from –19.0 to –11.0‰. Matrix values show the least variation (8.0‰), and deformation bands show the largest (18.8‰). δ13Ccarbonate values range from –7.7 to +2.6‰ (VPDB). These results indicate that carbonate minerals in the EKM likely precipitated from a range of sources and at different temperatures. Sr isotope analysis will further constrain the source and composition of paleo-fluids from which the carbonate minerals precipitated.