ISSN:
1525-1314
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Geosciences
Notes:
A detailed high-pressure experimental study of two mafic xenoliths, in which coexisting garnet and clinopyroxene (± plagioclase, spinel and olivine) were crystallized over a P–T range of 10–30 kbar and 950–1200°C, has revealed significant differences in temperatures from those estimated for coexisting garnets and clinopyroxenes using the Ellis & Green Fe–Mg exchange thermometer. The results show perfect matching at 30 kbar, 1150–1200°C, but increasing deviation at lower pressure and lower temperature, with the Ellis & Green calibration reaching a ΔT (overestimate) of c. 145°C at 10–12 kbar and 950°C. The grossular content of the garnet increases from c. 21 mol.% at 10 kbar to 26–31 mol.% at 30 kbar. These results confirm other recent experimental studies that show that the pressure correction, and possibly to a lesser extent the correction for grossular content, applied by Ellis & Green, are not appropriate for lower pressure conditions, and give estimated temperatures that are significantly high when applied to granulitic terranes formed at c. 10 kbar. The new reconnaissance results allow a graphical interpolation of a garnet–clinopyroxene geothermometer based on the Fe–Mg exchange reaction which should be applicable to assemblages formed under lower crustal conditions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1525-1314.1991.tb00528.x
