The Ti-saturation surface for low-to-medium pressure metapelitic biotites: Implications for geothermometry and Ti-substitution mechanisms

The low-pressure partial-melting behaviour of natural boron-bearing metapelites from the Mt. Stafford area, central Australia

“…Overall, minor and trace element distributions for biotite/muscovite pairs should be systematic over a range of increasing temperatures (Yang and Rivers, 2000) and should correlate to bulk compositions (Guidotti et al, 1977;Dahl et al, 1993;Yang and Rivers, 2000) et al, 1971;Green, 1981;Pichavant et al, 1988;Guidotti & Sassi, 1989;Guidotti et al, 1994;Vidal et al, 2001, Henry et al, 2005, Herman & Spandler, 2008, Auzanneau et al, 2009 and Ti contents in biotite (Dalmeyer, 1974;Patińo-Douce & Beard, 1995;Stevens et al, 1997;Henri & Guidotti, 2002, Auzanneau et al, 2009) can be correlated with metamorphic grade and are interpreted to enhance the thermal stability of these minerals. Ti concentrations in the micas are considered to reach maximum values when buffered by the presence of a Ti-rich phase.…”

Ti-in-biotite geothermometry in non-graphitic, peraluminous metapelites from Crni vrh and Resavski humovi (Central Serbia)

“…Along with the commonly used geothermometer based on Mg-Fe exchange between coexisting garnet and biotite (Ferry & Spear 1978;Perchuk & Lavrenteva 1983;Bhattacharya et al 1992;Holldaway 2000) or the THERMOCALC program (Powell & Holland 2001), the amount of Ti in biotite could also be used to determine the temperature of metamorphism in metapelites (Henry et al 2005). Experimental work on phlogopites has shown that there is a positive correlation between the amount of Ti in biotite and temperature and a negative correlation with pressure (Forbes & Flower 1974;Robert 1976).…”

“…Experimental work on phlogopites has shown that there is a positive correlation between the amount of Ti in biotite and temperature and a negative correlation with pressure (Forbes & Flower 1974;Robert 1976). Henry et al (2005), suggested that geothermometric calculations based on the amount of Ti and Mg/(Mg+ Fe) ratio in biotite can be applied to graphitic peraluminous metapelites that contain rutile and/or ilmenite and have equilibrated at pressures and temperatures of about 400-600 MPa and 480-800 °C, respectively. The authors suggest that this method can produce considerable disagreements with reference temperatures when it is applied to non-graphitic peraluminous metapelites containing Ti-saturated minerals.…”

“…The geothermometer of Henry et al (2005) is most sensitive for Ti contents in the range 0.0-0.3 apfu (atoms per formula unit). Biotites from the micaschists of Crni vrh and Resavski humovi, which have such a range of Ti content and are characterized by different X Mg values 0.65), provide a good basis for discussing the applicability and sensitivity of the Ti-in-biotite geothermometer on non-graphitic peraluminous metapelites.…”

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Abstract:The study discusses the application of the Ti-in-biotite geothermometer of Henry et al (2005) to the example of biotites from non-graphitic peraluminous micaschists of Central Serbia. Three petrographically different micaschists were distinguished on the basis of the following mineral assemblages: CV1 (St-Grt-Bt-Ms-Pg-Pl-Qtz), CV2 (Grt-St-Ky-BtMs-Pl-Qtz) and RH (Grt-St-Bt-Ms-Pl-Qtz).

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