Earth and Planetary Sciences ETDs

Publication Date

Fall 11-15-2023

Abstract

Roosevelt Hot Springs is an actively producing hydrothermal system that has been extensively studied by field, geophysical and geochemical techniques since the 1970’s. Roosevelt Hot Springs sits at the western base of the Mineral Mountains in Utah, an area that has formed because of many volcanic, thermal and structural events since the late Oligocene. The work in this manuscript is the first of its kind to incorporate measurements of spring-based CO2 fluxes with diffuse measurements to quantify the total CO2 Flux in tons per day of a Basin and Range and Colorado Plateau Transition Zone-hosted hydrothermal system. Using carbon isotope analyses and reviewing other geochemical studies done, this work explores the sources of carbonates which supply the reservoir of Roosevelt Hot Springs, hydrothermal system. In addition, the work in this manuscript quantifies the total Heat Flux in MW by the heat transfer mechanisms of conduction and convection. Finally, TOUGH3 thermophysical modeling is used to calculate how long the Roosevelt Hot Springs system will degas all the gaseous and aqueous CO2 in the reservoir based on different gas saturation at depth.

The total CO2 and Heat flux of Roosevelt Hot Springs hydrothermal system is ~5.6 tCO2 per day and 28 MW, respectively. The CO2 flux from Roosevelt Hot Springs is within range of volcano-hosted systems, but alone does not constrain how much CO2 is degassed from other geologically similar hydrothermal systems. The contribution of CO2 from springs makes up less than 4.5-5% or ~ 0.27 tCO2 per day of the total CO2 from Roosevelt Hot Springs. The spring contribution of 4.5-5% from springs shows that diffusely degassed CO2 is the major contributor of CO2 to the atmosphere from hydrothermal systems. A total Heat flux of 28 MW was calculated for conduction and convection which is comparable to the reported energy capacity of Blundell Power Plant which taps the Roosevelt Hot Springs reservoir.

Carbon isotopes analyses resulted in δ 13C values of ~ -7.75 ‰ to – 9.65 ‰. These values alone are inconclusive to the absolute source of carbonates in the reservoir but suggest a mixture between lighter organic carbonates and heavier mantle-sourced carbonates. A thermal gradient of ~148 °C/km was calculated by TOUGH3 thermophysical modeling software. The calculated thermal gradient is higher than an average crustal and granitic thermal gradient of 25 °C/km and 40 °C/km, respectively but less than the maximum measured thermal gradients of 500 °C/km found throughout Utah. The amount of time it would take to degas aqueous and gaseous CO2 from the Roosevelt Hot Springs reservoir is 1,935 years, 3,023 years and 4,111 years at gas saturations of 20%, 50% and 80% respectively. Based on the age of the hydrothermal system, the amount of CO2 present in the Roosevelt Hot Springs reservoir is not enough to sustain the system since it has been estimated to be formed. Based on carbon isotope analyses and the results of TOUGH3 modeling, it is likely that the mantle is supplying some degree of carbonate to the systems, sustaining current degassing rate of 0.06 kgCO2/s.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Tobias Fischer

Second Committee Member

Scott Nowicki

Third Committee Member

Karl Karlstrom

Language

English

Keywords

Hydrothermal, Gas, Heat, Reservoir characteristics, modeling, instrumentation

Document Type

Thesis

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