Use of fission track dates as constraints on the tectonic evolution of the Rio Grande rift. [Abstract only]
Apatite fission track dates have been determined for Precambrian and Tertiary granitic rocks collected from four ranges on the eastern margin of the Rio Grande rift. The ages at lower elevation in these areas are, in general, younger than those at higher elevation because of cooling as uplift occurs. Thus apparent uplift rates can be calculated from this relation between elevation and age, assuming that the geothermal gradient remained constant during uplift and erosion. Age dates on samples from the Wheeler Peak area north of Taos and the Sandia Mountains near Albuquerque indicate that the rocks at the higher elevations in these areas cooled to approx. 105/sup 0/C 30 to 35 Ma ago. The dates suggest that Precambrian rocks in the Wheeler Peak area were heated by a thermal event related to the Questa Caldera. Dates for the Tertiary intrusions in this area imply that uplift at an apparent rate of 0.1 mm/a has occurred since the intrusions cooled (20 Ma). The uplift of Sandia block, which does not seem to be directly associated with igneous activity, occurred at an average rate of .055 mm/a. Dates from the Organ batholith in southern New Mexico do not show a clear relation with elevation. The fission track dates (16 to 36 Ma) are consistent with shallow emplacement and subsequent rapid uplift of the batholith followed by formation of small geothermal systems sometime later in the Tertiary. In contrast to the other three areas where Tertiary tectonic activity affects the ages, dates from the Sangre de Cristo Mountains east of Sante Fe are related to Laramide uplift about 65 to 70 Ma ago. The apparent uplift rate is 0.072 mm/a. The data on the rate and timing of uplift imply that the heat sources that have caused the Tertiary tectonic and igneous features observed in the rift are not continuous along the rift's length, but are localized phenomena.
- Research Organization:
- Southern Methodist Univ., Dallas, TX
- OSTI ID:
- 6177045
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 15:5
- Country of Publication:
- United States
- Language:
- English
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