The role of metamorphism

The effect of metamorphism on the distribution of Hg in and about sulphide deposits remains controversial. Ozerova et al. (1975) described the Hg content of massive sulphide deposits in the Pacific and Ural provinces of Russia in relation to the type and environment of deposition of the ores and the post-ore metamorphism. In the Urals, deposits in rocks of prehnite-pumpellyite facies contain between 1000 and 100,000 ppb Hg, those in rocks of greenschist facies contain about 1000 ppb and those in amphibolite-grade rocks contain about 100 ppb Hg. They concluded that during metamorphism, sulphides lose their Hg as a vapour phase, which may travel some distance from the deposit. 

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Harlov D. E., Newton R. C., Hansen E. C., and Janardhan A. S. (1997) Oxide and sulfide minerals in highly oxidized, Rb-depleted, Archaean granulites of the Shevaroy HiUs massif. South India oxidation states and the role of metamorphic fluids. J. Metamorph. Geol. 15, 701-717. 

M. J. Bickle, The role of metamorphic decarbonation reactions in returning strontium to the silicate sediment mass. Nature 367, pp. 699-704 (1994). 

The names of van t Hoff, Arrhenius, Ostwald, and Nernst dot the pages of Van Hise s work and with good reason. His understanding of the effects of temperature and pressure on chemical reactions and of the roles of water and ionic equilibria in metamorphic processes was derived largely from his reading of the work of these physical chemists. "The handling of the problems of rock alteration with fairly satisfactory results," he later wrote, "was possible because of the rise of physical chemistry. 

Kitchen NE, Valley JW (1995) Carbon isotope thermometry in marbles of the Adirondack Mountains, New York. J metamorphic Geol 13 577-594 Kiyosu Y, Krouse HR (1990) The role of organic acid in the abiogenic reduction of sulfate and the sulfur isotope effect. Geochem J 24 21-27... 

Because of its simple chemical composition, the role of kaolinite in clay mineral assemblages is peripheral to or a limiting case for chemiographic representation of clay mineral systems which contain free silica forms as a compositional pole. Most often during epi-metamorphism kaolinite is incorporated into other phases due to a displacement of the bulk... 

Vanderhaeghe O, Teyssier C, Wysoczanski R (1999) Structural and geochronological constraints on the role of partial melting during the formation of the Shuswap metamorphic core complex at the latitude of the Thor-Odin Dome, British Columbia. Can J Earth Sci 36 917—943... 

Hirata, K. Y. and Hadfield, M. G., The role of choline in metamorphic induction of Phestilla (Gastropoda, Nudibranchia), Comp. Biochem. Physiol., 84C, 15, 1986. 

As a result, a physicochemical model for the formation of the BIF is proposed which is consistent with modern ideas on the evolution of sedimentation and volcanism and of the atmosphere, hydrosphere, and biosphere in the Precambrian. This model, which proposes a mainly volcanic source for the iron and silica and a biochemical and chemical mechanism of deposition, is the most likely but not the only possible one. Other versions, or different interpretations, are not ruled out, but it is perfectly obvious that in any genetic postulates, the specific physicochemical data must be taken into account. It is also quite understandable that in a work which is a first attempt at physicochemical analysis of the entire geological cycle— source of the material transport deposition diagenesis metamorphism—not all the problems have been worked out in sufficient detail and not all the evidence is conclusive far from it. Further investigations in this direction are needed, including not only determination of the role of the individual parameters in ore formation, but also direct experimental modeling of the process. 

Bingen B., Demaiffe D., and Hertogen J. (1996) Redistribution of rare earth elements, thorium, and uranium over accessory minerals in the course of amphibolite to granulite facies metamorphism the role of apatite and monazite in orthogneisses from southwestern Norway. Geochim. Cosmochim. Acta 60, 1341—1354. 

Brady J. B. (1988) The role of volatiles in the thermal history of metamorphic terranes. J. Petrol. 29, 1187-1213. 

Chamberlain C. P. and Rumble D. (1988) Thermal anomalies in a regional metamorphic terrane an isotopic study of the role of fluids. J. Petrol 29, 1215-1232. 

Etheridge M. A., Wall V. J., and Vernon R. H. (1983) The role of the fluid phase during regional metamorphism and deformation. J. Metamorph. Geol. 1, 205-226. 

Ridley J. and Thompson A. B. (1986) The role of mineral kinetics in the development of metamorphic microtextures. In Fluid—Rock Interactions during Metamorphism (eds. J. V. Walther and B. J. Wood). Springer, New York, pp. 154-193. 

Rubie D. C. (1998) Disequilibrium during metamorphism the role of nucleation kinetics. In What Drives Metamorphism and Metamorphic Reactions Special Publications, 138 (eds. P. J. Treloar and P. J. O Brien). Geological Society, London, pp. 199-214. 

Walther J. V. (1990) Fluid dynamics during progressive regional metamorphism. In The Role of Fluids in Crustal Processes (Geophysics Study Committee, Commission on Geosciences, Environment, and Resources, National Research Council). National Academy Press, Washington, DC, pp. 64-71. 

Wada H., Ando T., and Suzuki M. (1998) The role of the grain boundary at chemical and isotopic fronts in marble during contact metamorphism. Contrib. Mineral. Petrol. 132, 309-320. 

Yang P. and Rivers T. (2001) Chromium and manganese zoning in pelitic garnet and kyanite spiral, overprint, and oscillatory ( ) zoning patterns and the role of growth rate. J. Metamorph. Geol. 19, 455—474. 

DeYoreo J. J., Lux D. R., and Guidotti C. V. (1989) The role of crustal anatexis and magma migration in the in the thermal evolution of regions of thickened crust. In Evolution of Metamorphic Belts, Special Publications 43 (eds. J. S. Daly, R. A. Cliff, and B. W. D. Yardley). Geological Society of London, London, England, pp. 187 -202. 

Matthews A, Beckirtsale RD, Ditrham JJ (1979) Oxygen isotope fiactiorration between rattle and water and geothermometiy of metamorphic eclogites. Mineral Mag 43 406-413 McCormell JDC (1995) The role of water in oxygen isotope exchange in qirartz. Earth Planet Sci Letters 136 97-107... 

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