Effect of hydrochemical ion pair CaCO30 on the deposition of travertine
from the Heinitang hot springs in Yunnan of China
Abstract
The Heinitang hot spring is located in the western Yunnan of China and
lies in the Tibet-Yunnan geothermal zone and the Tengchong Block. The
hot water is of HCO3-Ca•Na type and the F concentration is relatively
high (ranging from 3.8 to 5 mg/L). Fossil travertine mounds and cones
and new travertine are found at the spring vents. Hydrochemical analyses
indicate that the primary factor affecting the deposition of travertine
is the concentration of ion pair CaCO30 in the Heinitang hot springs.
The Heinitang hot spring shows a positive correlation between the
concentration of CaCO30 and the saturation index with respect to
aragonite, calcite and dolomite. They are not linearly related, but have
an exponential relationship. When the aragonite, calcite and dolomite
are in the state of dissolved equilibrium, the corresponding
concentrations of CaCO30 are 0.01 mmol/L, 0.008 mmol/L and 0.012 mmol/L,
respectively, indicating that the precipitation of travertine can occur
when the concentration of CaCO30 is higher than 0.008 mmol/L. In
addition, the concentrations of CaCO30 in the Heinitang hot springs
decrease gradually with the deposition of travertine. The precipitation
of travertine cannot occur when the concentration of CaCO30 decreases to
lower than 0.008 mmol/L.