Mapping vent to distal-apron hot spring paleo-flow pathways using siliceous sinter architecture

Abstract

Environmentally significant textural components of sinters from New Zealand and the U.S.A. were examined using X-ray powder diffraction, petrographic microscopy, scanning electron microscopy, and 14C accelerated mass spectroscopy (AMS). Sinter samples from five New Zealand sites; Waiotapu, Orakei Korako, Wairakei, Tahunataara, Broken Hill, and two USA sites; Opal Mound, Utah, and Steamboat Springs, Nevada, revealed, textures are preserved in pristine condition in sinters of varying silica phases and ages. The distinctive macro-textures that relate to temperature-pH gradients and the hydrodynamics of hot spring environments enabled the identification of paleo-hot spring settings. Sinter textures observed include: (1) low-temperature biotic textures; (2) mid-temperature biotic textures; (3) high-temperature abiotic textures; and (4) flow-rate indicative textures. Mapping the paleo-hydrology of extinct hot spring locations based on sinter architecture established the location of historic high- versus low-temperature hot spring flow paths. This information is particularly useful in the early phases of geothermal exploration, especially for hidden geothermal systems and epithermal mineralization, where establishing the location of hot up-flow zones and high temperature discharge vents is favorable. Sinter textural mapping combined with AMS 14C dating provides a spatial and temporal context of discharging reservoir fluid, enables the tracking of alkali chloride fluid flow to the surface, establishes hot spring migration pathways, and contributes to the development of a geothermal hydrologic model.