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The geotherm of the lithosphere beneath Qilin, SE China: a re-appraisal and implications for P–T estimation of Fe-rich pyroxenites
Authors:Yigang Xu  Chuanyong Lin  Lanbin Shi
Institution:

a Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Wushan, Guangzhou, China

b Institute of Geology, State Seismological Bureau, 100029 Beijing, China

Abstract:The Qilin geotherm established by Xu et al. Xu, X.S., O'Reilly, S.Y., Zhou, X.M. and Griffin, W.L., 1996. A xenolith-derived geotherm and the crust-mantle boundary at Qilin, southeastern China. Lithos, 38: 41–62.] using the Ellis and Green Ellis D.J. and Green D.H., 1979. An experimental study of the effect of Ca upon garnet-clinopyroxene Fe-Mg exchange equilibria. Contrib. Mineral. Petrol., 71: 13–22]/Wood Wood B.J., 1974. Solubility of alumina in orthopyroxene coexisting with garnet. Contrib. Mineral. Petrol. 46: 1-15] combination is in need of revision on the basis of re-evaluation of geothermobarometers, comparison of calculated pressures and temperatures with experimentally determined phase relationships and geological/geophysical data. The invalid assumption that all iron is present as Fe2+ in minerals, and the thermal destruction of equilibrium Fe–Mg exchange between clinopyroxene and garnet that may have resulted from heating of the Qilin xenoliths by the host magma resulted in unrealistically high temperatures estimated by the Ellis and Green's thermometer. An important implication arising from this study is that care must be taken when applying thermobarometers to Fe-rich pyroxenites for the purpose of geotherm construction and a comprehensive analysis is often required.
Keywords:Geotherm  Thermobarometry  Garnet pyroxenite  Lithosphere  Qilin  SE China
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