LECTURES ON GEOCHEMICAL !N1 ERPRETATION OF ...

- 25 -Quartz Geothe~ometerEquation Applicable in the Temperature Range 20 330· CA silica (quartz) geothermometer equation given by Fournier and Potter(1982b) that is useful through the temperature range 20- 330·C at the vaporpressure of the solution is(7)where Cl through Cs are constants given in Table 1. Table 2 givescalculated quartz solubilities in liquid water and steam at the vaporpressure of the solution in lO·C temperature intervals up to the criticalpoint. When there has been no steam separation, silica geothermometertemperatures can be obtained graphically from Figure 2 or computed fromequation (1) up to 330·C. Hote, however. that Figure 2 and equati on (7)apply only to dilute solutions . High salinity of the solvent will have aminor effect on the solubility of quartz at temperatures below about 300°Cand a major effect at higher temperatures (discussed later).TABLE 1. Const ants used in equations in the text .Ai Bi Ci DiEquation (9) Equation (10) Equation (1) Equation (8)1. 4.1884 x 10 2 2.035 x 10 3 -4.2198 x 10 1 - 3.5532 x 1002. 1.0286 x 10 1 - 5.0499 x 100 2.8831 x 10- 1 1.4600 x 10- 13. - 5.0920 x 10- 2 5.7399 x 10- 2 - 3.6686 x 10- 4 - 4.9270 x 10- 44. 2.6309 x 10- 4 - 3.0426 x 10-4 3.1665 x 10-7 1. 2305 x 10-65 . - 6.9303 x 10- 1 7.9095 x 10- 7 7.7034 x 10 1 - 4.9421 x 10-106 . 7.4566 x 10- 10 - 8.6968 x 10-107. - 1. 2098 x 10 3 1.3424 x 10 38 . 1.1990 x 10 1 -1.3298 x 10 19 . - 3.5376 x 10 2 3 . 9629 x 10 2