Dating thermal events at Cerro Prieto using fission-track annealing

Conference · Thu Jan 01 00:00:00 EST 1981

OSTI ID:5961317

Sanford, S J; Elders, W A

The duration of heating in the Cerro Prieto reservoir was estimated 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 160 and 180{sup 0}C. Complete annealing at these temperatures requires 10{sup 4} and 10{sup 3} years, respectively. Well M-94 has an apparently complex thermal history. Geothermometers in this well indicate temperatures some 50 to 100{sup 0}C higher than those measured directly in the borehole. Fission tracks are partially preserved in M-94 where paleotemperatures were as high as 200{sup 0}C and are erased where geothermometers indicate temperatures of 250{sup 0}C. This implies a thermal event less than 10{sup 1} years and greater than 10{sup 0} years in duration.

• Research Organization: California Univ., Riverside (USA). Inst. of Geophysics and Planetary Physics
• DOE Contract Number: AT03-80SF11458
• OSTI ID: 5961317
• Report Number(s): CONF-810399-4; ON: DE82001979
• Resource Relation: Conference: 3. symposium on the Cerro Prieto geothermal field in Baja California, Mexico, San Francisco, CA, USA, Mar 1981
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
CERRO PRIETO GEOTHERMAL FIELD
GEOTHERMAL WELLS
AGE ESTIMATION
ANNEALING
BOREHOLES
FISSION TRACKS
GEOLOGY
GEOTHERMOMETRY
SANDSTONES
WELL TEMPERATURE
CAVITIES
GEOTHERMAL FIELDS
HEAT TREATMENTS
PARTICLE TRACKS
RESERVOIR TEMPERATURE
ROCKS
SEDIMENTARY ROCKS
WELLS
Geothermal Legacy
150202* - Geology & Hydrology of Geothermal Systems- Non-USA- (-1989)