Geothermal metamorphism

Bird, D.K. and Helgeson, H.C. (1981) Chemical interaction of aqueous solution with epidote-feldspar mineral assemblages in geologic systems II, Equilibrium constraints in metamorphic/geothermal processes. Am. J. Set, 281, 576-614. 

Cavaretta, G., Gianelli, G. and Puxeddu, M. (1980) Hydrothermal metamorphism in the Larderello geothermal field. Geothermics, 9, 297-314. 

The relevance of the remarks on sulfur content is that, for reasons explained above, it is usually a valid index of the salinity of the environments of deposition. It was remarked earlier that the Eastern and Interior provinces have experienced different temperature/pressure/time histories. It should be added that coals of the Rocky Mountain, Pacific and Alaskan provinces most probably experienced yet further sets of conditions of metamorphism a locally increased geothermal gradient that produced relatively high temperatures at relatively low depths of burial and hence at relatively low pressures of overburden. 

White, D. E., Anderson, E. T. Grubbs, D. K. 1963. Geothermal brine well Mile deep drill hole may tap ore-bearing magmatic water and rocks undergoing metamorphism. Science, 139, 919-922. 

No significant differences have been established between heulandite and laumontite in sedimentary formations in the zones of deep epigenesis (initial metamorphism), on the one hand, and the same minerals in hydro-thermal deposits, on the other. Apparently, this will require more factual data. Nevertheless, the distribution of these zeolites and the associations of clay minerals permit a distinction between the zeolite facies of regional epigenesis-metamorphism and the zeolite mineralization in geothermal areas (recent hydrothermal systems). 

Manning C. E. and Ingebritsen S. E. (1999) Permeability of the continental crust imphcations of geothermal data and metamorphic systems. Rev. Geophys. 37, 127—150. 

According to Manning and Ingebritsen (2001), geothermal and metamorphic fluid-flux data show that permeability (k, m ) decreases with depth (z, km) in the continental cmst according to the equation... 

Implications of geothermal data and metamorphic systems Reviews of Geophysics, v. 37, p. 127-150. 

Muffler, L.J. and White, D.E., 1969. Active metamorphism of Upper Cenozoic sediments in the Salton Sea geothermal field and the Salton Trough, southeastern California. Geol. Soc. Am. Bull., 80 157—182. 

As products of hydrothermal metamorphism in geothermal fields, such as Wairakei (10, 42), Pauzhetsk (39), and Onikobe (38). In these, a generalized downward sequence with increasing temperature is mordenite with or without analcime, rare heulandite, laumontite, wairakite, less hydrous phases. 

---