CONSTRAINING THE ORIGIN OF CALCITE IN THE VEINS HOSTED IN LOCKATONG AND PASSAIC FORMATIONS USING C-O STABLE ISOTOPES AND FLUID INCLUSIONS: IMPLICATION TO FLUID MIGRATION IN THE NEWARK BASIN

The calcite veins hosted in the Lockatong and Passaic formations of the Newark basin have been investigated to constrain the genesis of these calcites. The oxygen isotope values of calcite samples in both Lockatong and Passaic formations are narrow and similar (average ~ +24.4 ‰ _SMOW). This isotopic composition reflects an isotopic exchange between heavy oxygen of lacustrine carbonates and oxygen of formational waters with long residence time. These calcite samples have an average carbon isotope composition of -3.4 ‰ _SMOW indicative of a mixture between the isotopically light organic matter-derived carbon and an isotopically heavy carbon from formational and evolved meteoric waters. Fluid inclusions reveal that the fluid responsible for the precipitation of calcite was hot (>152 °C) and moderately saline (~10.5 wt% NaCl equiv.) This fluid reflects a mixture between formational waters and evolved meteoric waters. The latter descended to deeper lithostratigraphic units during the Late Triassic extensional tectonic activity. Once geothermally heated, these topographically-driven meteoric waters migrated laterally along the Stockton aquifer. Dilatational pump seismically induced-mechanism together with compaction expelled these waters during the Late Triassic extensional tectonic activity. Subsequently, these fluids mixed and interacted with local formational waters leading to the precipitation of calcite in fractures hosted in the Lockatong and Passaic formations.