Magmatism

Most copper deposits are (/) porphyry deposits and vein replacement deposits, (2) strata-bound deposits in sedimentary rocks, (J) massive sulfide deposits in volcanic rocks, (4) magmatic segregates associated with nickel in mafic intmsives, or (5) native copper, typified by the lava-associated deposits of the Keweenaw Peninsula, Michigan. 

Indium (0.24 ppm) is similar in abundance to Sb and Cd, whereas T1 (0.7 ppm) is close to Tm and somewhat less abundant than Mo, W and Tb (1.2 ppm). Both elements are chalcophiles (p. 648), indium tending to associate with the similarly sized Zn in its sulfide minerals whilst the larger T1 tends to replace Pb in galena, PbS. Thallium(I) has a similar radius to Rb and so also concentrates with this element in the late magmatic potassium minerals such as feldspars and micas. 

Volume 56 Dennis L. Hartmann. Global Physical Climatology. 1994 Volume 57 Michael P. Ryan. Magmatic Systems. 1994... 

There is another opinion on the origin of Kuroko ore fluids. Sawkins (1982) thought that intrusive felsic magmas were the source of the metals and heat in Kuroko hydrothermal systems. He stressed the contributions of magmatic fluid and seawater in... 

High salinity of Kuroko ore fluids does not solely mean magmatic contribution. Instead salinity variation can be reasonably explained by subcritical boiling of fluids of seawater origin. 

SD and 8 0 values for epithermal deposits from other countries are summarized in Fig. 1.105 (Field and Fifarek, 1985). The oxygen shift away from the meteoric water line is always observed, but 8D is similar to meteoric water value, suggesting meteoric water source of epithermal ore fluids. Magmatic contribution to ore fluids has not been found except in some ore fluids responsible for the deposits in the other countries Tui... 

The REE characterics of calcite from the Au-Ag type are variable. For example, calcites from Sado Au-Ag vein, one of the largest Au-Ag deposits in Japan have both signatures of meteric water and magmatic (or igneous) contributions. Positive Eu anomaly is only found in caleite containing low REE from Au-Ag type (Seigoshi deposit) (Shikazono, unpublished). 

The changes in stress fields, and intensities of igneous and hydrothermal activities seem to correlate to oscillatory motion of the Pacific plate (Jackson s episodes) (Jackson et al., 1975 Jackson and Shaw, 1975) (Masuda, 1984). Masuda (1984) and Takeuchi (1987) pointed out that the oscillatory motion of Pacific plate during the least 42 Ma correlates with magmatism, the intensity of tectonism, the change of stress field and the history of sedimentary basin in arc-trench system (Fig. 1.147). The above arguments also suggest that the mineralizations in arc and back-arc systems relate to the oscillatory motion of the Pacific plate. 

The chemical compositions of coexisting sphalerite and tennantite-tetrahedrite from the mines were determined. Except the Ashio polymetallic deposits, the other deposits have been formed at late Cretaceous related to felsic magmatism. 

Burnham, C.W. and Ohmoto, H. (1980) Late-stage process of felsic magmatism. Soc. Mining Geologist. Japan,... 

Giggenbach, W.F. (1997) The origin and evolution of fluids in magmatic-hydrothermal systems. In Barnes, H.L. (ed.). Geochemistry of Hydrothermal Ore Deposits. New York John Wiley and Sons, pp. 699-... 

Ishibashi, J. and Urabe, T. (1995) Hydrotheimal activity related to arc-back arc magmatism in the Western Pacific. In Taylor, B. (ed.), Backarc Basins Tectonics and Magnetism, Plenum Publ, pp. 451—496. 

Ishihara, S. and Sasaki, A. (1991) Ore deposits related to granitic magmatism in Japan A magmatic viewpoint. Episodes, 14, 286-292. 

Watanabe, Y. and Ohta, E. (1999) Late miocene magmatic-hydorthermal sy.stems in the Jozankei-Zenibako district, southwest Hokkaido, Japan. Resource Geology, 49, 59-74. 

D, 8 0 and Cl concentration data suggest the mixing of meteoric water, connate seawater and magmatic gas (Seki, 1991) (Fig. 2.20). Br/Cl and B/Cl ratios are different from those of seawater (Fig. 2.21). This difference and N2-H2-Ar gas composition indicate a contribution of magmatic gas (Seki, 1991, 1996). 

Gena et al. (2001) reported advanced argillic alteration of basaltic andesite from the Desmos caldera, Manus back-arc basin which was caused by interaction of hot acid hydrothermal fluid originated from a mixing of magmatic gas and seawater. It is noteworthy that the acid alteration is found in back-arc basins (Manus, Kuroko area) but not in midoceanic ridges. 

Aoki, M. (1992a) Magmatic fluid discharging to the surface from the Osorezan geothermal system, northern Honshu, Japan. Geol. Surv. Japan, Rep., 279, 16-21. 

Tagiri, M. and Okura, C. (1979) Metavolcanic rocks from the Hitachi and the Keisuku mountain block districts, with special reference to their magmatic series and the Tanakura Tectonic Line. J. Geol Soc. Japan, 85, 679-689 (in Japanese with English abst.). 

Stable isotopic studies of 5 0 and 8D of hydrothermal solutions venting from back-arc basins show no evidence of contribution of magmatic fluids to the hydrothermal solutions at back-arc basins and midoceanic ridges. As noted already, the stable isotopic data (S S, S C, S 0, 8D) all indicate that hydrothermal solutions in submarine hydrothermal system in back-arc basins and midoceanic ridges were generated by seawater-rock interaction at hydrothermal conditions. 

Isotopic compositions are also critical in these petrogenic modelling studies, to provide ages of the different magmatic episodes. Among the most important ones are Sr/ Sr, Pb/ Pb, Pb/ Pb, and NBS-certi-... 

Potts PJ, Hawkesworth CJ, van Casteren P, Wright IP (1993) In Pritchard H M, Alabaster X Harris NBW, Neary CD, eds. Magmatic Processes and Plate Tectonics, pp 501-520. Geological Society Special Publication No 76. 

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