Garnet chemistry

Novak G. A. and Colville A. (1975). A linear regression analysis of garnet chemistries versus cell parameters (abstract). Geol Soc. Amer. S. W. Section Meeting, Los Angeles, 7 359. 

D. W. Hopkins, Physical Chemistry and Metal Extraction,). Garnet-Miller Ltd., London, 1954. 

S. Geller, Crystal Chemistry of the Garnets, Zeit. Kristallographie, 125,1 (1967). 

Table 5.18 Chemistry and terminology of main components of the garnet phase.

Armbruster T. and Geiger C. A. (1993). Andradite crystal chemistry Dynamic X-site disorder and structural strain in silicate garnets. Eur. J. Min., 5 59-71. 

Armbruster T., Geiger C. A., and Lager G. A. (1992). Single-crystal X-ray structure study of synthetic pyrope ahnandine garnets at 100 and 293 K. Amer. Mineral, 77 512-521. Atkins P. W. (1978). Physical Chemistry. Oxford Oxford University Press. 

Novak G. A. and Gibbs G. V. (1971). The crystal chemistry of silicate garnets. Amer. Mineral, 56 791-825. 

Schwartz K. B. and Burns R. G. (1978). Mossbauer spetroscopy and crystal chemistry of natural Fe-Ti garnets. Tram. Amer. Geophys. Union, 59 395-396. 

Garnet Kin-Lic Chan Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301 USA... 

Amthauer, G. (1976) Crystal chemistry and colour of chrome-bearing garnets. Neues Jahrb. Mineral. Abh., 126,158—86. 

Evans, B. J. Sergent Jr, E. W. (1975) 57NGR of Fe phases in magnetic cassiterites . I. Crystal chemistry of dodecahedral Fe2+ in pyralspite garnets. Contrb. Mineral. Petrol, 53, 183-94. 

Huggins, F. E., Virgo, D. Huckenholtz, H. G. (1977) Titanium-containing silicate garnets, n. The crystal chemistry of melanites and schorlomites. Amer. Mineral., 62,646-65. 

Several other anhydrous calcium aluminosilicates are known, including grossular or garnet (C3AS3), which is a high-pressure phase, various dehydration products of zeolites, and various products formed metastably by crystallization from melts or glasses. Most are too acid in composition to be of clear relevance to cement chemistry, but some of the devitrification products, especially those with compositions near to CA and structures similar to those of nepheline (Na3KAl4Si40i6) or kalsilite (KAlSiOj (Y4), are of possible interest in relation to the formation of calcium aluminate cements. 

While all spinel-lherzolite facies suites show remarkably similar compositional trends as a function of depletion, some garnet peridotite xenoliths in kimberlites and lamproites from ancient cratonic lithospheric keels show signih-cantly different trends (e.g., see Boyd, 1989 Chapters 2.05 and 2.08). Most of these xenoliths are extremely depleted extrapolation of the trends back to the PM MgO of 36.7% gives similar concentrations of Si02, EeO AI2O3, and CaO to the spinel Iherzolites (O Neill and Palme, 1998) the difference in their chemistry is due to a different style of melt extraction, and not a difference in original mantle composition. 

Orthopyroxene Clinopyroxene Spinel Garnet Plagioclase Amphibole Mica Thermobarometry Bulk Rock Chemistry... 

Cr-poor variety widespread, locally abundant (e.g.. Monastery). Garnets, clino- and orthopyroxenes, phlogopite and ihnenite most common, zircon and olivine rarer. Debatable whether phlogopite and olivine are members of Cr-poor suite. Wide range in chemistry but Cr-poor, Fe-Ti-rich relative to type I (low-Z) peridotite minerals. Mineral chemistry and estimated equilibration P/Ts overlap those of type V (high-Z) Iherzolites. Some Slave craton Cr-poor megacrysts show mineral chemistry links to type II megacrystalline pyroxenite xenoliths. See review of Schulze (1987). 

P-type inclusions high-Cr, low Ca garnet, Cr-diopside, Fo-rich olivine, orthopyroxene, chromite, wustite, Ni-rich sulfide, have restricted, high Mg, high Ni chemistry. Equilibration temperatures 900-1,100 °C. 

MacGregor I. D. and Carter J. L. (1970) The chemistry of clinopyroxenes and garnets of eclogite and peridotite xenohths from the Roberts Victor Mine, South Africa. Phys. Earth Planet. Int. 3, 391—397. 

---