RARE EARTH ELEMENTS AND STABLE ISOTOPES IN VEIN-FILLING CARBONATE CEMENTS FROM THE ORDOVICIAN VININI TYPE-SECTION IN CENTRAL NEVADA: INDICATORS OF DIAGENESIS

Rare earth element (REE) and oxygen isotope signatures in the Ordovician Vinini Formation type-section in central Nevada are being used to test the hypothesis that water-rock interaction in the type-section was limited to diagenetic fluids of meteoric origin. This research is significant because constraining the source of diagenetic fluids may help refine models of paleofluid flow in Nevada’s Great Basin. Determining the origin of paleofluids is relevant to petroleum and mineral exploration.

The objective of this research is to observe REE changes across vein-filling carbonate cements to determine whether discrete cement layers represent individual fluid events. Rare earth elements are used as the chemical indicator because they are non-reactive and their signature can help determine fluid provenance. Oxygen isotopes are used to determine the temperature of the parent fluid(s) that precipitated the vein-filling cements.

Rare earth elements will be determined using electron microprobe (EMP) and laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS). Oxygen isotopes will be analyzed using isotope mass spectrometry (MS). It is anticipated, based on tectonic history, petrographic and geochemical analyses, that the characteristics of these vein-filling cements will indicate a meteoric origin for the parent fluid(s).