Geobarometry for Peridotites: Experiments in Simple and Natural Systems from 6 to 10 GPa

Application of thermodynamic modelling to natural mantle xenoliths: examples of density variations and pressure–temperature evolution of the lithospheric mantle

“…This model shows good agreement with the available experimental data in both Cr-poor and Cr-rich mantle Compositions from LS1 to BN4 were taken from Stern et al (1999) and were normalized to 100 wt% after removing TiO compositions (e.g. Nickel 1986;Webb and Wood 1986;Walter 1998;Brey et al , 1999Brey et al , 2008 and is therefore considered to be more appropriate for an application to a set of natural mantle xenoliths such those from Pali-Aike (bulk Cr# = 0.05-0.30). We would like to caution the reader that the values reported as enthalpies of formation in Table 2 of Klemme et al (2009) and supplementary table of Ziberna et al (2013) are actually free energies of formation and that the Cr-bearing clinopyroxene end-member used in the calculations is CaCr 2 SiO 6 and not MgCr 2 SiO 6 .…”

“…It is important to note, however, that the Al 2 O 3 contents in clinopyroxenes may be slightly overestimated by our model, as they generally show slightly higher values relative to the available phase equilibria experiments at comparable temperatures (e.g. Green and Ringwood 1970;Nickel 1989;Brey et al , 2008. Further development of the model should include a better thermodynamic mixing model and better end-member data for the tschermakite end-members of clinopyroxene solid solution.…”

“…Al 2 O 3 contents in pyroxenes decrease constantly with decreasing temperature and generally increase with decreasing pressure, in accordance with experimental observations (cf. Green and Ringwood 1970;Nickel 1989;Brey et al , 2008. However, the P dependence of Al 2 O 3 in pyroxenes is not linear.…”

Pyroxenites and megacrysts from Vitim picrite-basalts (Russia): Polybaric fractionation of rising melts in the mantle?

“…We have used the method of Nimis and Taylor (2000) for temperatures showing good agreement with the experimental values (Taylor, 1998;Walter, 1998;Yaxley, 2000;Dasgupta et al, 2007;Brey et al, 2008;Foley et al, 2009;etc. ) (Fig.…”

“…The typical BMG clinopyroxenes give two arrays of cooling from 1300 to 1200°C around 2.2 and 2.5 GPa. An inclined PT path continues the trend derived from this cloud, forming two additional (Nimis and Taylor, 2000) for the clinopyroxenes, the solid circles are for data used for calibration in this work (Nimis and Taylor, 2000): (Taylor, 1998;Walter, 1998;Brey and Kohler, 1990; and in addition from Brey et al, 2008), the open circles are for the extended data set (Foley et al, 2009;Walter, 1998 (Ashchepkov and Andre, 2002;Litasov et al, 2000) and worldwide pyroxenites (Frey, 1980;Pearson and Nowell, 2004;Upton et al, 2003;Downes, 2007;Zheng et al, 2009) using polymineral thermobarometry (Brey and Kohler, 1990) (see Appendix A equation set 1) and monomineral methods (Nimis and Taylor, 2000) Nimis and Taylor (2000) thermometer and Ashchepkov (2002) barometer (symbols are as in Fig. 3).…”