GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 92-9
Presentation Time: 10:25 AM


KIM, Jihyun1, NOYES, Chandler1, DELL'ORO, Ambria1, TYNE, Rebecca2, FERGUSON, Grant3, PERSON, Mark4, MA, Lin5, LU, Zheng-Tian6, JIANG, Wei6, YANG, Guo-Min6, BALLENTINE, Chris2, REINERS, Peter7 and MCINTOSH, Jennifer1, (1)Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ 85721, (2)Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, United Kingdom, (3)Department of Civil, Geological and Environmental Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada, (4)Department of Earth & Environmental Science, New Mexico Tech, 801 Leroy Place, Socorro, NM 87801, (5)Department of Geological Sciences, University of Texas at El Paso, 500 W. University Ave, El Paso, TX 79968, (6)Department of Engineering and Applied Physics, University of Science and Technology of China, Hefei, Anhui 230027, China, (7)Department of Geosciences, University of Arizona, 1040 E. 4th St, Tucson, AZ 85721

The Paradox Basin in the Colorado Plateau has diverse manifestations of paleofluid flow, including widespread sandstone bleaching and ore mineralization, salt tectonics, and abundant hydrocarbon, CO2 and He reservoirs. Forty-six fluid samples were collected in 2018 to evaluate the hydrochemical distribution and sources of remnant fluids as an indicator of the long-term evolution of paleofluids in the Paradox Basin. Surface waters and shallow groundwater in Paradox and Sinbad salt valleys contain Na-Cl type brines from meteoric water dissolution of halite and anhydrite. Strontium and S isotopic signatures of the Na-Cl type brines confirm that dissolution of evaporites is the dominant source of solutes. Holocene to Pleistocene age shallow groundwater from Cretaceous Burro Canyon and Jurassic Navajo formations in the Paradox Valley are Na-Ca-HCO3 type dilute meteoric waters with elevated U concentrations and S and Sr isotope values indicative of interaction with sulfides and carbonates. Stable isotope values of δ18O and δD and Cl/Br ratios of Ca-Cl brines in the Pennsylvanian Honaker Trail Formation indicate the formation waters likely originated from partially-evaporated seawater, which interacted with radiogenic minerals in Permian-age arkosic redbeds and sulfides, based on Sr and S isotopes, respectively. Desert Creek and Cane Creek members of the Pennsylvanian Paradox Formation contain the most saline Ca-Cl type formation waters with chemical and isotopic signatures indicative of paleo-evaporated seawater associated with deposition of the potash evaporite minerals. Basinal brines in underlying Mississippian and Devonian formations are derived from paleo-evaporated seawater diluted by meteoric water and influenced by dissolution of halite from the Paradox Formation. Radio-krypton (81Kr) and noble gases are being analyzed to further constrain the residence time of basinal fluids.