Hostname: page-component-cd9895bd7-gvvz8 Total loading time: 0 Render date: 2024-12-23T18:32:51.520Z Has data issue: false hasContentIssue false
  • English
  • Français

Thermal and kinetic constraints on the tectonic applications of thermobarometry

Published online by Cambridge University Press:  05 July 2018

Peter D. Crowley
Peter D. Crowley*
Affiliation:
Department of Geology, Amherst College, Amherst, MA 01002, U.S.A. and Geologisches Institut, ETH-Zentrum, CH-8092 Zürich, Switzerland
Get access Rights & Permissions [Opens in a new window]

Abstract

Metamorphic petrology, and in particular quantitative thermobarometry, offer the possibility of identifying faults in metamorphic terrains by the metamorphic and/or thermobarometric breaks that occur across them. Furthermore, the sense of the thermobarometric break (e.g. warmer, deeper rocks on top of colder, shallower ones) and its magnitude could be useful tools for determining the sense and magnitude of the fault. The sensitivity of thermobarometry to tectonic variables such as fault throw and uplift rate, has been tested by a series of one-dimensional numerical re-equilibration models for both thrust and normal faults. In each of these models, the post-tectonic re-equilibration of a model garnet-biotite geothermometer is simulated by coupling one-dimensional numerical thermal and garnet diffusion models. After cooling and uplift, a thermobarometric temperature was calculated by using a near-rim garnet composition (5–10 µm from the rim) calculated by the re-equilibration model and biotite from the model matrix. The models varied the thermal structure of the model orogen prior to faulting, the depth of the fault, the structural throw of the fault, and the uplift rate following faulting.

All models produced zoned garnet porphyroblasts that recorded P-T conditions that were different from those at the time of fault motion. Most of the models produced thermobarometric breaks that were in the same sense as the temperature break at the time of fault motion. Normal faults produced a normal thermobarometric gradient with higher temperatures recorded below the fault than above it. Many, but not all of the thrust models produced a thermobarometric inversion near the fault, with higher temperatures locally recorded above the fault than below it. However, the magnitude of thermobarometric break correlated poorly with the fault throw. Most models developed thermobarometric breaks that were much smaller than the breaks that existed at the time of fault motion. The size of the thermobarometric break was commonly of the same magnitude as would be generated from microprobe analytical error. The models suggest that for metamorphic rocks whose thermal peak does not exceed a narrowly defined closure temperature, thermobarometry faithfully recorded the P-T conditions of the metamorphic peak. The closure temperature increases slightly with increasing uplift rate, but overall is rather insensitive to the uplift rate or other tectonic variables. For rocks whose thermal peaks is above the closure temperature, however, the model thermobarometer recorded a temperature that was very close to the closure temperature.

Keywords

thermobarometryfaultsmetamorphic petrologygarnet-biotite geothermometer
Type
Research Article
Information
Mineralogical Magazine , Volume 55 , Issue 378 , March 1991 , pp. 57 - 69
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1991

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Anderson, D. E. and Olimpio, J. C. (1977) Progressive homogenization of metamorphic garnets, south Morar, Scotland: evidence for volume diffusion. Can. MineraL, 15, 205–16.Google Scholar
Barker, A. J. and Anderson, M. W. (1989) The Caledonian structural metamorphic evolution of south Trom, Norway. In Evolution of Metamorphic Belts (Daly, J. S., Cliff, R. A., and Yardley, B. W. D., eds.), Geo. Soc. Lond. Spec. Publ., 43, 385–9.Google Scholar
Buck, W. R., Martinez, F., Steckler, M. S., and Cochran, J. R. (1988) The thermal consequences of lithospheric extension: Pure and simple. Tectonics, 7, 213–34.CrossRefGoogle Scholar
Carlson, W. D. (1989) The significance of intergranular diffusion to the mechanics and kinetics of porphyroblast crystallization. Contrib. Mineral. Petrol., 103, 1–24.CrossRefGoogle Scholar
Connolly, J. A. A. and Thompson, A. B. (1989) Fluid and enthalpy production during regional metamorphism. Ibid., 102, 347–56.Google Scholar
Crank, J. (1975) The Mathematics of Diffusion. (2nd ed.), Clarendon Press, Oxford.Google Scholar
Crowley, P. D. (1988) The metamorphic break across postmetamorphic thrust faults: an unreliable indicator of structural throw. Geology, 16, 469.2.3.CO;2>CrossRefGoogle Scholar
Crowley, P. D. (1990) Metamorphism with the (Çokkul synform: evidence for detachment faulting within the metamorphic infrastructure of the Norwegian Caledonides (67°30′). metamorph. Geol. in press.Google Scholar
Crowley, P. D. and Spear, F. S. (1987) The P-T Evolution of the Middle Krli Nappe Complex, Scandinavian Caledonides (68 N) and its Tectonic Implications, Contrib. Mineral. PetroL, 95, 512–22.CrossRefGoogle Scholar
Cygan, R. T. and Lasaga, A. (1985) Self diffusion of magnesium in garnet at 750° to 900° Am. J. Sci., 285, 328–50.CrossRefGoogle Scholar
Davy, Ph. and Gillet, P. (1986) The stacking of thrust sheets in collisional zones and its thermal consequences. Tectonics, 5, 913–30.CrossRefGoogle Scholar
Dodson, M. (1973) Closure temperature in cooling geochronological and petrological systems. Contrib. Mineral. Petrol., 40, 259–74.CrossRefGoogle Scholar
Elphick, S. C., Ganguly, J., and Loomis, T. P. (1985) Experimental determinations of cation diffusivity in aluminosilicate garnet I: Experimental methods and interdiffusion data. Ibid., 90, 33–44.Google Scholar
England, P. C. and Richardson, S. W. (1977) The influence of erosion upon mineral facies of rocks from different metamorphic environments. J. Geol. Soc. Lond., 134, 210–3.CrossRefGoogle Scholar
England, P. C. and Thompson, A. B. (1984) Pressure-temperature- time paths of regional metamorphism I: Heat transfer during the evolution of regions of thickened crust. J. Petrol., 25, 894–928.CrossRefGoogle Scholar
Essene, E. J. (1989) The current status of thermobarometry in metamorphic rocks. In Evolution of Metamorphic Belts (Daly, J. S., Cliff, R. A., and Yardley, B. W. D., eds.) Geol. Soc. Lond. Spec. Publ., 43, 1–44.Google Scholar
Ferry, J. M. and Spear, F. S. (1978) Experimental calibration of the partitioning of Fe and Mg between garnet and biotite. Contrib. Mineral. Petrol., 66, 113–7.CrossRefGoogle Scholar
Finley, C. A. and Kerr, A. (1987) Evidence for differences in the growth rates among garnets in peletic schists from northern Sutherland, Scotland. Mineral. Mag., 51, 569–76.CrossRefGoogle Scholar
Fisher, G. W. (1978) Rate laws in metamorphism. Geoehim. Cosmoehim. Acta, 42, 1035–50.CrossRefGoogle Scholar
Freer, R. (1981) Diffusion in silicate minerals and glasses: a data digest and guide to the literature. Contrib. Mineral. Petrol., 76, 440–54.CrossRefGoogle Scholar
Hodges, K. V. and Crowley, P. D. (1985) Error Estimation in Empirical Geothermometry and Geobarometry for Pelitic Systems. Am. Mineral., 70, 702–9.Google Scholar
Hodges, K. V. and McKenna, L. W. (1987) Realistic propagation of uncertainty in geologic thermobarometry. Ibid., 72, 673–82.Google Scholar
Hodges, K. V. and Royden, L. (1984) Geologic thermobarometry of retrograded rocks: an indication of the uplift trajectory of a portion of the northern Scandinavian Caledonides. J. Geophys. Res., 89, 7077–90.CrossRefGoogle Scholar
Koziol, A. M. and Newton, R. C. (1988) Recalibration of the anorthite breakdown reaction and improvement of the plagioclase-garnet–A12SiO5-quartz geobarometer. Am. Mineral., 73, 316–23.Google Scholar
Lasaga, A. C. (1983) Geospeedometry: An extension of geothermometry. In Kinetics and Equilibrium in Mineral Reactions (Saxena, S. K., ed.), 81–114, Springer-Verlag, New York.CrossRefGoogle Scholar
Lasaga, A. C. (1986) Metamorphic reaction rate laws and the development of isograds. Mineral. Mag., 50, 359–73.CrossRefGoogle Scholar
Lasaga, A. C., Richardson, S. M. and Holland, H. D. (1977) The mathematics of cation diffusion and exchange between silicate minerals during retrograde metamorphism. In Energetics of Geological Processes (Saxena, S. K. and Bhattachanji, , eds.) 353–88. Springer-Verlag, New York.CrossRefGoogle Scholar
Loomis, T. P. (1982) Numerical simulations of the disequilibrium growth of garnet in chlorite-bearing aluminous pelitic rocks. Can. Mineral., 20, 411–23.Google Scholar
Mancktelow, N. (1985) The Simplon Line: a major displacement zone in the western Lepontine Alps. Eclogae geol. Helv., 78, 73–96.Google Scholar
Rice, A. H. N., Begins, R. E., Robunson, D., and Roberts, D. (1989) Thrust related metamorphic inversions in the Caledonides of north Norway. In Evolution of Metamorphic Belts (Daly, J. S., Cliff, R. A., and Yardley, B. W. D., eds.), Geol. Soc. London. spec. Publ., 43, 413–21.Google Scholar
Ruppel, C., Royden, L., and Hodges, K. V. (1988) Thermal models of extensional tectonics: Applications to pressure-temperature-time histories of metamorphic rocks. Tectonics, 7, 947–57.CrossRefGoogle Scholar
Steltenpohl, M. G. and Bartley, J. M. (1987) Thermobarometric profile through the Caledonian nappe stack of Western Ofoten, North Norway. Contrib. Mineral. Petrol., 96, 93–103.CrossRefGoogle Scholar
Thompson, A. B. and England, P. C. (1984) Pressure-temperature-time paths of regional metamorphism II: Their inference and interpretation using mineral assemblages in metamorphic rocks. J. Petrol., 25, 894–928.CrossRefGoogle Scholar
Walther, J. V. and Wood, B. J. (1984) Rate and mechanism in prograde metamorphism. Contrib. Mineral. Petrol., 88, 246–59.CrossRefGoogle Scholar