| Title | Dating Thermal Events at Cerro Prieto Using Fission Track Annealing |
|---|---|
| Authors | Sanford, S.J., Elders, W.A. |
| Year | 1981 |
| Conference | DOE-CFE Symposium on Cerro Prieto |
| Keywords | `` |
| Abstract | We have estimated the duration of heating in the Cerro Prieto reservoir by relating the fading of spontaneous fission tracks in detrital apatite to observed temperatures. The rate of fading is a function of both time and temperature. The apparent fission track age of the detrital apatites then, is a function of both their source age and their time-temperature history. Data from laboratory experiments and geologic fading studies were compiled from published sources to produce lines of iso-annealing for apatite in time-temperature space. Fission track ages were calculated for samples from two wells at Cerro Prieto, one with an apparently simple and one with an apparently complex thermal history. Temperatures were estimated by empirical vitrinite reflectance geothermometry, fluid inclusion homogenization and oxygen isotope equilibrium. These estimates were compared with logs of measured borehole temperatures. The temperature in well T-366,. where complete annealing first occurs, was estimated to be between l600and 180°C. Complete annealing at these temperatures requires 104 and 103 years, respectively. Well M-94 has an apparently complex thermal history. Geothermometers in this well indicate temperatures some 50° to 1000c higher than those measured directly in the borehole. Fission tracks are partially preserved in H-94 where paleotemperatures were as high as 2000C and are erased where geothermometers indicate temperatures of 250°C. This implies a thermal event less than 101 years and greater then 100 years in duration. |