Paragenesis

Several sub-classification.s of epithermal preciou.s-metal deposits have been proposed mineralogy, host-rock composition and elemental association (Lindgren, 1928), gold-silver ratios of metal weights (Ferguson, 1929 Nolan, 1933), mineral paragenesis (Nishiwaki et al., 1971), and production ratios of metals (Heald-Wetlaufer et al., 1983). 

Kamilli, R.J. and Ohmoto, H. (1977) Paragenesis, zoning, fluid inclusion, and isotope studies of the Finlandia vein, Colqui district, central Peru. Econ. Geol., 72, 950—982. 

Lee, M.S., Takenouchi, S. and Imai, H. (1974) Occurrence and paragenesis of the Cu-Fe-Sn-S minerals, with reference to stannite, stannoidite and mawsonite. J. Mineral. Soc. Japan, 11, Spec. Issue 2, 155-164 (in Japanese). 

Matsukuma, T. and Yui, S. (1979) Occurrence and paragenesis of bomite-rich Kuroko ores containing Ge, Sn-bearing mineral from the No. 11 ore depositions of the Shakanai mine, Akita Prefecture, Japan. Report of the Research Institute of Underground Resources, Mining College, Akita U., No. 45, pp. 91-104 (in Japanese). 

Sato, Takeo (1969) An estimation for physicochemical environments of formation of the Kuroko deposits based on their mineral paragenesis, Koshogakunote (Note on Economic Geology), 7, 1-16 (in Japanese). 

Fig. 2.45. Hypothetical mineral paragenesis for a sulfide-sulfate-silica chimney. Approximate temperature ranges for different minerals are based on direct measurements of vent fluid temperatures and analyses of fluid inclusions in real chimneys (Hannington et al., 1995).

Graham, V.M., Bluth, G.J. and Ohmoto, H. (1988) Sulfide-sulfate chimneys on the East Pacific Rise 11° and 13°N latitudes. Part I mineralogy and paragenesis. Can. Mineral, 26, 487-504. 

Depending upon lithologic and structural relationship with host rocks, mineralogy, attendant alteration, paragenesis and spatial and temporal constraints, the uranium resources of the world can be assigned to the 15 main categories of uranium ore deposits. They have been shown numerically numbered in sequence in the order of their approximate economic significance in Table 1.18. At present, only 7 can be said to be economically important (see Table 1.19) and these account for more than 95% of the world resources of ura-... 

Morse, J. W. and W. H. Casey, 1988, Ostwald processes and mineral paragenesis in sediments. American Journal of Science 288, 537-560. 

As shown in figure 4.5B, extrinsic disorder (nonstoichiometry) may vary considerably, as a function of solid paragenesis, between the low Pq stability limit defined by equilibrium... 

Pyroxenes (as feldspars) occupy a position that is chemically central in the realm of rock compositions (Robinson, 1982). They are therefore found ubiquitously and virtually in any kind of paragenesis developing in the P-T-Xconditions typical of earth s mantle and crust. Table 5.31 hsts the main occurrences. 

At low P, the Fe2Si205 component is extrinsically unstable with respect to a-quartz plus fayalite paragenesis ... 

Fet us now consider an initial composition C2. We are within the two spinodal points on the Gibbs free energy coherent curve G decomposition takes place spontaneously throughout the entire phase, with modulated compositional fluctuations whose amphtudes increase as the process advances. We always obtain pigeonite plus diopside, although theoretically the orthopyroxene plus diopside paragenesis, also in this case, corresponds to the minimum energy of the system. 

Table 5.44 Compositions (in weight %) of some natural amphiboles (from Deer et al., 1983) (1) = anthophyllite from a serpentinite (2) gedrite from a gedrite-kyanite-garnet paragenesis (3) cummingtonite from a oligoclase-biotite schist (4) common hornblende from a tonalite (5) pargasite from a metamorphic limestone (6) basaltic hornblende from a lathe (7) glaucophane from a glaucophane schist. ...

Figure 5.71A shows univariant equilibrium curves for various molar amounts of ferrous component in the orthopyroxene mixture. The P-T field is split into two domains, corresponding to the structural state of the coexisting quartz (a and j3 polymorphs, respectively). If the temperature is known, the composition of phases furnishes a precise estimate of the P of equilibrium for this paragenesis. Equation 5.277 is calibrated only for the most ferriferous terms, and the geobarometer is applicable only to Fe-rich rocks such as charnockites and fayalite-bearing granitoids. 

Detailed speciation calculations for the fluid coupled with mineralogical investigation of the solid paragenesis generally allow a sufficiently precise estimate of the T of equilibrium. As figure 8.30A shows, the chemistry of the fluid is buffered by wall-rock minerals, so that the saturation curves of other phases not pertaining to the system of interest are scattered (figure 8.28B). 

Petrographic research is investigating the weathering paragenesis of these samples. 

Mineral paragenesis and alteration suggests the following sequence of... 

Finch. R. J. Murakami, T. 1999. Systematics and paragenesis of uranium minerals. In Burns, P. C. Finch, R. (eds) Uranium Mineralogy, Geochemistry and the Environment. Mineralogical Society of America, Reviews in Mineralogy, 38, 91-180. 

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