Ti-in-biotite (TIB) geothermometer of Henry et al. (2005) is based on
the Ti-saturation surface of near-isobaric natural biotite data for peraluminous metapelites equilibrated at 4-6 kbar.
This surface is evaluated in terms of temperature (T) vs.
XMg vs. Ti,
and is solved specifically for
T = ([ln(Ti) - a - c(XMg)3]/b)0.333
where T is temperature in șC, Ti is the apfu normalized to 22 oxygens, XMg is Mg/(Mg+Fe), and the a, b and c parameters are given below.
This expression is valid in the range XMg = 0.275 -1.0, Ti = 0.04 - 0.6 apfu and T = 480-800 șC. Due to isotherm spacing, temperatures are more uncertain at low temperatures (< 600 șC) than at high temperatures. Based on the standard deviations of the temperatures in our calibrated data set from the saturation surface, the uncertainty of the Ti-in-biotite geothermometer is estimated to be ±24șC at lower temperatures (< 600 șC), improving to ±12 șC at high temperature (> 700 șC).
To apply the TIB geothermometer expression in the strictest sense, the following criteria should be met:
An added feature of the systematics of the Ti-in-biotite is that it can also serve as a very sensitive monitor of local equilibrium and disequilibrium in a rock (see right hand panel of image at top).
Darrell Henry publications related to TIB geothermometry and Ti substitutions in biotite
Henry, D. J., Guidotti, C. V. and Thomson, J. A. (2005) The Ti-saturation surface for low-to-medium pressure metapelitic biotite: Implications for Geothermometry and Ti-substitution Mechanisms. American Mineralogist, 90, 316-328. (pdf of article)
Henry, D.J. and Guidotti, C.V. (2004) Ground truthing biotite in peraluminous and metaluminous metamorphic rocks. Geological Society of America Abstracts with Program, 36. (abstract)
Henry, D.J. and Guidotti, C.V. (2004) Ti substitution mechanisms in biotite: Perspectives from a biotite Ti-saturation surface. Abstracts of the Goldschmidt Conference.
Henry, D. J. and Guidotti, C. V. (2002) Ti in biotite from metapelitic rocks: Temperature effects, crystallochemical controls and petrologic applications. American Mineralogist, 87, 375-382. (pdf of article)
Henry, D. J. and Guidotti, C. V. (2000) Ti in biotite from metapelitic from metapelitic rocks: some petrologic applications. Geological Society of America Abstracts with Program, 32, A53.
LaGrange, A., Henry, D. J. and Guidotti, C. V. (1992) Ti in biotite from graphite-bearing metapelites of NW Maine: interrelationship of crystal chemistry, mineral assemblage and temperature. Transactions of the American Geophysical Union, 73, 326.
Guidotti, C. V., Cheney, J. T. and
Henry, D. J. (1988) Compositional variation of biotite as a function of
metamorphic reactions and mineral assemblage in the pelitic schists of
western Maine: American Journal of Science-Wones Memorial Volume, v. 288A,
is the Campanile
Charities Professor of Geology and
Geophysics at Louisiana State University whose research specialty is metamorphic
petrology. Further details of his professional background are included in an accompanying
vita or faculty profile.
This page was last updated on 04/17/06.