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Diffusion of 40Ar in metamorphic hornblende

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Abstract

Isothermal, hydrothermal experiments were performed on two compositionally contrasting hornblendes from amphibolites in order to examine Ar diffusion behavior in metamorphic hornblendes. Ten experiments on sample RF were performed at temperatures of 750°C, 800°C, and 850°C and pressures of 1 kbar using measured grain radii of 158, 101, and 34 μm. Eight experiments on sample 118576 were performed under the same conditions using measured grain radii of 145, 77, and 25 μm. Minor (<5%) alteration was observed in high temperature runs. Diffusion coefficients were calculated from measured radiogenic 40Ar loss following treatment assuming a spherical geometry for the mineral aggregate. Diffusivities calculated for different grain sizes vary by up to an order of magnitude for a given temperature indicating that the effective diffusion radius was less than the measured grain radius. Diffusivities for RF and 118576 calculated for grain radii of 101 and 145 μm, respectively, form a linear array on an Arrhenius diagram with slopes indicating activation energies of ∼ 60 kcal/mol. No correlation between Mg number (100 Mg/(Mg+Fe)) and activation energy was observed. Diffusivities calculated for these experiments are higher than previously reported results from similar experiments performed on hornblendes. A comparison of results for 34 μm splits from these two studies indicates higher apparent diffusivities (by a factor of 5), which probably result from observed phyllosilicate inter-growths (chlorite) and/or exsolution lamellae that partition the metamorphic hornblendes into smaller subdomains. Diffusivities calculated for experiments performed on 65 μm and 34 μm splits of 40Ar/39Ar standard MMhb-1 at 800°C and 1 kbar are consistent with a previously reported activation energy of 65 kcal/mol. Arrhenius parameters which emerge from the empirical model of Fortier and Giletti (1989) agree with experimental results to within analytical uncertainty. Although results of these experiments support previously reported estimates of the activation energy of 40Ar in hornblende (∼60 kcal/mol), phyllosilicate intergrowths and/or microstructures such as exsolution lamellae within the two metamorphic hornblendes result in extremely small diffusion domains, which may lead to lower Ar retentivities and lower closure temperatures. The effective diffusion dimension for 40Ar in hornblende is not likely to be defined by dislocations but rather by some larger structure within the crystal. TEM and SEM studies may provide some insight into the effective diffusion dimension for 40Ar in amphiboles, thereby enabling better estimates of closure temperatures and more precise temperature-time reconstructions.

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References

  • Alexander EC Jr, Mickelson GM, Lanphere MA (1978) MMhb-1: a new 40Ar/39Ar dating standard. US Geol Surv Open-File Rep 78-701:6–8

    Google Scholar 

  • Baldwin SL (1988) Thermochronology of a subduction complex in western Baja California. PhD dissertation, State University of New York at Albany

  • Baldwin SL, Harrison TM (1989) Geochronology of blueschists from west-central Baja California and the timing of uplift in subduction complexes. J Geol 89:149–163

    Google Scholar 

  • Berry RF, McDougall I (1986) Regional metamorphism in East Timor: 40Ar/39Ar and K/Ar evidence from the Aileu Formation. Chem Geol (Isot Geosci Sect) 59:43–58

    Google Scholar 

  • Crank J (1975) The mathematics of diffusion, 2nd edn. Clarendon, Oxford

    Google Scholar 

  • Dodson MH (1973) Closure temperature in cooling geochronological and petrological systems. Contrib Mineral Petrol 40:259–274

    Google Scholar 

  • Dowty E (1980) Crystal-chemical factors affecting the mobility of ions in minerals. Am Mineral 65:174–182

    Google Scholar 

  • Farver JR, Giletti BJ (1985) Oxygen diffusion in amphiboles. Geochim Cosmochim Acta 49:1403–1411

    Google Scholar 

  • Foland KA (1974) 40Ar diffusion in homogeneous orthoclase and an interpretation of Ar diffusion in K-feldspar. Geochim Cosmochim Acta 38:151–166

    Google Scholar 

  • Fortier SM, Giletti BJ (1989) An empirical model for predicting diffusion coefficients in silicate minerals. Science 245:1481–1484

    Google Scholar 

  • Gaber LJ, Foland KA, Corbató CE (1988) On the significance of argon release from biotite and amphibole during 40Ar/39Ar vacuum heating. Geochim Cosmochim Acta 52:2457–2465

    Google Scholar 

  • Gerling EK, Kol'tsova TV, Petrov BV, Zul'fikarova ZK (1965) On the suitability of amphiboles for age determination by the K−Ar method. Geochem Int 2:148–154

    Google Scholar 

  • Giletti BJ (1974) Diffusion related to geochronology. In: Hofmann AW, Giletti BJ, Yoder HS Jr, Yund RA (eds) Geochemical transport and kinetics. Carnegie Institution Washington, DC, publication 634, pp 107–115

  • Gittos MF, Lorimer GW, Champness PE (1974) Precipitation (exsolution) in an amphibole (the hornblende-grunerite system). J Mater Sci 9:184–192

    Google Scholar 

  • Hanson GN, Gast PW (1967) Kinetic studies in contact metamorphic zones. Geochim Cosmochim Acta 31:1119–1153

    Google Scholar 

  • Harrison TM (1980) Thermal histories from the 40Ar age spectrum method. PhD dissertation, Australian National University

  • Harrison TM (1981) Diffusion of 40Ar/39Ar in hornblende. Contrib Mineral Petrol 78:324–331

    Google Scholar 

  • Harrison TM, Duncan I, McDougall I (1985) Diffusion of 40Ar in biotite: temperature, pressure and compositional effects. Geochim Cosmochim Acta 49:2461–2468

    Google Scholar 

  • Harrison TM, Fitz Gerald JD (1986) Exsolution in hornblende and its consequences for 40Ar/39Ar age spectra and closure temperature. Geochim Cosmochim Acta 50:247–253

    Google Scholar 

  • Harrison TM, McDougall I (1980) Investigations of an intrusive contact, northwest Nelson, New Zealand. I. Thermal, chronological and isotopic constraints. Geochim Cosmochim Acta 44:1985–2003

    Google Scholar 

  • Hart SR (1964) The petrology and isotopic-mineral age relations of a contact zone in the Front Range, Colorado. J Geol 72:493–525

    Google Scholar 

  • Heizler MT, Harrison TM (1988) Multiple-trapped argon components revealed by 40Ar/39Ar isochron analysis. Geochim Cosmochim Acta 52:1295–1303

    Google Scholar 

  • Huneke JC, Smith SP (1976) The realities of recoil: 39Ar recoil out of small grains and anomalous patterns in 39Ar/40Ar dating. Geochim Cosmochim Acta Supplement 7 (Proc of Seventh Lunar Sci Conf):1987–2008

    Google Scholar 

  • Leake BE, Elias EM, Farrow CM (1988) The relationship of argon retentivity and chemical composition of hornblende. Geochim Cosmochim Acta 52:2165

    Google Scholar 

  • Lippolt HJ, Weigel E (1987) 4He diffusion in 40Ar-retentive minerals. Geochim Cosmochim Acta 52:1449–1458

    Google Scholar 

  • Lovera OM, Richter FM, Harrison TM (1989) The 40Ar/39Ar thermochronometry for slowly cooled samples having a distribution of diffusion domain sizes. J Geophys Res 94:17917–17936

    Google Scholar 

  • McDougall I, Harrison TM (1988) Geochronology and Thermochronology by the 40Ar/39Ar method. Oxford University Press, Oxford

    Google Scholar 

  • Mussett AE (1969) Diffusion measurements and the potassium-argon method of dating. Geophys JR Astron Soc 18:257–303

    Google Scholar 

  • O'Nions RK, Smith DGW, Baadsgaard H, Morton RD (1969) Influence of chemical composition on argon retentivity in metamorphic calcic amphiboles from south Norway. Earth Planet Sci Lett 5:339–345

    Google Scholar 

  • Onstott TC, Peacock MW (1987) Argon retentivity of hornblende: a field experiment in a slowly cooled metamorphic terrane. Geochim Cosmochim Acta 51:2891–2903

    Google Scholar 

  • Samson SD, Alexander EC Jr (1987) Calibration of the interlaboratory 40Ar/39Ar dating standard MMhb-1. Chem Geol (Isotope Geoscience Section) 66:27–34

    Google Scholar 

  • Thomas G, Goringe MJ (1979) Transmission electron microscopy of materials. Wiley Interscience, New York

    Google Scholar 

  • Tighe NJ (1976) Experimental techniques. In: Wenk HR (ed) Electron microscopy in mineralogy. Springer, Berlin Heidelberg New York, pp 144–171

    Google Scholar 

  • Turner G (1968) The distribution of potassium and argon in chondrites. In: Ahrens LH (ed) Origin and distribution of the elements. Pergamon, London, pp 387–398

    Google Scholar 

  • Turner G (1971) 40Ar/39Ar ages from the Lunar Maria. Earth Planet Sci Lett 11:169–191

    Google Scholar 

  • Turner G, Huneke JC, Podosek FA, Wasserburg GJ (1971) 40Ar/39Ar ages and cosmic ray exposure age of Apollo 14 samples. Earth Planet Sci Lett 12:19–35

    Google Scholar 

  • Yund RA, Quigley J, Tullis J (1989) The effect of dislocations on bulk diffusion in feldspars during metamorphism. J Metamorph Geol 7:337–341

    Google Scholar 

Download references

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Author notes

  1. Suzanne L. Baldwin

    Present address: Research School of Earth Sciences, The Australian National University, GPO Box 4, 2601, Canberra, A.C.T.

  2. T. Mark Harrison

    Present address: Department of Earth & Space Sciences, University of California, 90024, Los Angeles, CA, USA

Authors and Affiliations

  1. Department of Geological Sciences, State University of New York at Albany, 12222, Albany, NY, USA

    Suzanne L. Baldwin & T. Mark Harrison

  2. Research School of Earth Sciences, The Australian National University, GPO Box 4, 2601, Canberra, A.C.T., Australia

    John D. Fitz Gerald

Authors
  1. Suzanne L. Baldwin
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  2. T. Mark Harrison
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  3. John D. Fitz Gerald
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Baldwin, S.L., Harrison, T.M. & Gerald, J.D.F. Diffusion of 40Ar in metamorphic hornblende. Contr. Mineral. and Petrol. 105, 691–703 (1990). https://doi.org/10.1007/BF00306534

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  • DOI: https://doi.org/10.1007/BF00306534

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