GEOCHEMICAL VARIATION AND PETROGENETIC PROCESSES OF CALIENTE VOLCANIC UNITS

The Caliente Volcanic Complex (CVC) in southwestern Utah and southeastern Nevada has a plethora of pyroclastic flow and fall units. The CVC is part of the Basin and Range Province and is approximately 200 km in diameter and erupted material at least 3 km in thickness. The five units of interest are the Isom-Needle Range (part of the Indian Peaks caldera), Lower Bauers Tuff, Middle Bauers Tuff, Harmony Hills Flow and the Leach Canyon Flow. These flows are important because of the areal extent and uncertain origin of some flows in the area. The area sampled was along Utah Route 56 approximately 20 km west of Cedar City. The exact location of the different unit’s origins and their flow paths are uncertain. Although they are all likely from the same complex, the exact relationship between the eruptive units is unclear, particularly given the large size of the volcanic complex. Therefore, understanding the potential petrogenetic relationships between these eruptive units is extremely important. In particular, this study aims at understanding the magmatic source of these five eruptive units and the role of magma mixing within and potentially between these individual units. One efficient way of investigating these questions is through the geochemical study of melt inclusions in crystals and the chemical zonation of those crystals as well. Volatile concentrations of the melt inclusions was determined using Raman spectroscopy and laser ablation-inductively coupled plasma mass spectrometry was used to determine the overall geochemistry. The chemical composition and zonation of the phenocrysts was determined using the electron microprobe.