Physical and chemical controls on carbonate precipitation in surficial hot springs and subterranean cold springs
Rimmed-pool deposits in surficial hot springs at Yellowstone National Park, WY, and cold springs in Fogelpole Cave, IL, are compared to determine physical and chemical parameters controls on carbonate precipitation. Macroscale (> 0.5mm) morphology and depositional patterns of carbonate precipitation in these hot and cold springs are independent of water temperature and calcite saturation states. Conversely, microscale (< 0.5mm) crystal shape, mineralogy and chemistry directly reflect the dramatically different physical, chemical and biological environmental conditions in the hot and cold springs. Both Yellowstone and Fogelpole spring waters precipitate hemispherical carbonate ponds in a terrace pattern. Yellowstone carbonates, called the travertine terraced ponds, precipitate at rates of 0.4 - 0.8 mm/day from 38°C spring water that is about 48 times supersaturated with respect to calcite (Qcaicite = 48). Fogelpole carbonates, called speleothem rimmed pools, precipitate from l6°C water with Qcalcite = 2. The much higher Qcalcite values at Yellowstone are probably related to very high concentrations of calcite precipitation inhibitors, SO4 and Mg2+. Plane light and cathodoluminescence petrographic analyses established very different paragenetic sequences for the two deposits. ESEM analysis indicates that the travertines are composed of a greater variety of crystal fabrics and have more euhedral forms than the speleothems. Size histograms show that a size invariance may exist in the water depths and step lengths of the travertine ponds. Precipitation in both systems is driven mainly by CO2 degassing and not evaporation. Differences in equilibrium and observed 813C values of calcite suggest microbial respiration may influence carbonate precipitation.
Carbonate precipitation, Surficial hot springs, Subterranean cold springs, Physical controls, Chemical controls
University of Illinois - Urbana-Champaign
Networked Digital Library of Theses and Dissertations
University of Illinois at Urbana-Champaign