Hydrochemical Control Factors Of Travertine Precipitation And Simulation Of Travertine Formation Of The Wang 4 Well In Tianjin

Travertine means all non-marine carbonate precipitate in or near terrestrial springs, rivers, lakes and caves. Almost all travertines consist of the two principal polymorphs of calcium carbonate, calcite and aragonite. The thermogene travertine special morphology includes mound, cone, column, ridge and wall. This paper collected 16 hot springs or wells'data in 12 areas with travertine at home and abroad, and 7 hot springs or wells'data without travertine, compared the dew point of geological features and hydrochemical characteristics, tried to summarize hydrochemical conditions of water which precipitate travertine.We selected the Wang 4 well in Tianjin, Wenluo hot springs in Guangxi, Jifei hot springs in Yunnan, Hebi hot wells in Henan, Pamukkale hot springs in Turkey, Mammoth hot springs in US, Rongma hot springs, Giwa hot springs, Zhare hot springs, Dagejia geysers, Kawu hot springs, and Chabu hot springs in Tibet. Hot springs without travertine include Baimiao hot springs, Chicheng hot springs, Huailai Warm Springs in Hebei, Wang 2 well and Wang 3 well in Tianjin, Wenquanzhen hot springs in Yunnan, Licun hot springs in Guangxi.We analized temperature, pH, TDS, contents of Mg²⁺, Na⁺, K⁺, SO₄^2-, Cl^-, F^-, H₂SiO₃, Ca²⁺, HCO₃^-, Mg/Ca, and carbon-13 of these springs. Using PHREEQC.2 we analyzed saturation index of calcite and aragonite, partial pressure of carbon dioxide (Pco₂), complex ion composition of carbon, calcium. We found that the thermal groundwater with following characters tend to precipitate travertine: neutral or acidic water, Pco₂ greater than 9%, Na·Ca-HCO₃ type water, CO₂, HCO₃^- and Ca²⁺ dominant in complex ion components. In addition, the water flow rapidly out of Wangsi well, promoted the formation of travertine.Taking the Wangsi well at Zhouliangzhuang town of Baodi District in Tingjn for example, we analyszed hydrochemical changes of the travertine precipitation, and used PHREEQC.2 simulate the deposition process to quantify the precipitation of minerals and gas. There are 4 simplest models, reflecting while the well water contacted with air during rushing through the pool wall, the carbon dioxide escaped, aragonite, calcite, dolomite and siderite precipitated, a small amount of Hematite, goethite precipitated. Due to low contents of other cationic elements in travertine samples, they may be incorporated into the crystal lattice or trapped as inclusions.