Characterizing Hot Spring Connectivity Using Aqueous Geochemistry in the River Group Springs, Yellowstone NP, Wyoming

Abstract:

Abstract

We analyzed the aqueous geochemical components of 11 springs in the River Group, Yellowstone National Park, Wyoming. For the springs sampled, we found pHs ranging from a low of ∼4.8 to a high of ∼9.6; TDS (as inferred from electrical conductivity measurements) was roughly correlated to pH, with the lowest pH spring being the most dilute (373 µS) and the highest pH spring having the second highest conductivity (1384 µS). In combination with a shallow ground temperature survey and visual observations of the relative water levels in the springs, the spring chemistries support a conceptual model of fracture-controlled fluid flow in which individual springs demonstrate a surprising level of flowpath isolation. We hypothesize that variations in flowpath permeability lead to steam-heating of low-pH springs, while nearby circumneutral springs are heated by upwelling liquid hydrothermal fluids, high in chlorid and other dissolved components. If our hypothesis is correct, it implies that vaporand liquid-dominated zones of Model III hydrothermal systems can coexist in close proximity, resulting in a complex surface expression of acid-sulfate and chloride-rich circum-neutral springs.