Mathematics – Logic
Scientific paper
Jul 1989
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989gecoa..53.1621f&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 53, Issue 7, pp.1621-1631
Mathematics
Logic
7
Scientific paper
The kinetics of oxygen and strontium diffusion in natural fluorapatite (Durango, Mexico) have been measured under hydrothermal conditions using an ion microprobe. Diffusion coefficients were obtained at temperatures from 550 to 1200°C for oxygen, and 650 to 1200°C for strontium. All experiments were run at 1000 bars (100 MPa) water pressure except those designed to measure the water pressure dependence, which were at 200 to 2000 bars. The Arrhenius relations obtained for diffusion parallel to the c axis at 1000 bars water pressure are: Element D 0 (cm 2 /sec) Q (kcal/mol) T (°C) Oxygen 9·10 -5 49 ± 3 550-1200 Strontium 2·10 -11 25 ± 4 650-1000 Strontium 1· 10 5 120 ± 22 1100-1200. The diffusion coefficient for oxygen transport parallel to the c axis is approximately three orders of magnitude greater than that perpendicular to the c axis over the temperature range of the experiments. No anisotropy was observed for strontium diffusion in apatite. An increase in water pressure from 200 to 2000 bars yields an increase in D of approximately a factor of three for oxygen diffusion parallel to the c axis at 800°C. The Arrhenius relation for strontium diffusion in the temperature range 1100 to 1200°C is in good agreement with the et al . (1985) data for dry 1 atm experiments at 1050 to 1250°C. Strontium diffusion coefficients obtained in the temperature range 650 to 1000°C yield significantly greater D values than predicted by extrapolation of the high-temperature Arrhenius relation. The new data show that closure temperatures calculated for strontium diffusion in apatite are significantly lower than the hightemperature studies would predict. Thus, apatite crystals would remain open to strontium diffusional exchange well below the solidus temperature of most igneous rocks. This could result in higher 87 Sr / 86 Sr values in the apatite than the whole-rock initial value. Measurable enrichment in 87 Sr / 86 Sr values in apatite could also be produced by a later thermal disturbance at moderate geologic temperatures and durations.
Farver John R.
Giletti Bruno J.
No associations
LandOfFree
Oxygen and strontium diffusion kinetics in apatite and potential applications to thermal history determinations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Oxygen and strontium diffusion kinetics in apatite and potential applications to thermal history determinations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Oxygen and strontium diffusion kinetics in apatite and potential applications to thermal history determinations will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1704617