Magmatic fluid

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... 

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

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. 

In our initial use of VIRS methods, we have chosen a diverse set of projects. These include epithermal-style precious metal mineralization (eastern and central Newfoundland), mesothermal gold mineralization (Central Newfoundland), syngenetic VMS mineralization and related alteration (Central Newfoundland), porphyry-style Mo-Cu mineralization (southern Newfoundland) and uranium mineralization in the Central Mineral Belt of Labrador. Space does not permit detailed discussion of results, but in all cases we were able to recognize distinctive alteration species and document their distribution. In some cases, results provided surprises, eg., the recognition of topaz in quartz-alunite alteration and possible Li-rich micas in VMS alteration influenced by magmatic fluids. In some cases, the resolution of species in mixed assemblages proved to be difficult, but the overall spectral patterns could still be used to discriminate alteration facies and demonstrate their superposition. 

Consultants Ltd., United Kingdom). The analyses were performed on pyroxene and garnet crystals of exoskarn facies. Microprobe data obtained from pyroxene shows a wide composition variation that fluctuates between 53-80 wt.% Di, 20-47 wt.% Hd, and minor amounts of Jo (0.05-0.36 wt.%). Furthermore, mineral garnet composition ranges between 68-99 wt.% Grs, 0-20 wt.% Ad, 0-8 wt.% Aim, and 0-0.75 wt.% Prp. These significant changes are mainly linked to the variations in the magmatic fluid composition of the system, where Fe, Mg, Al, and Si contents show an erratic behaviour, whereas Ca values remain constant. 

Despite the close association of intnisions with many ore deposits, there is still debate about the extent to which magmas contribute water and metals to ore-forming fluids. Many early studies of the stable isotope composition of hydrothermal minerals indicated a dominance of meteoric water (Taylor 1974), more recent studies show that magmatic fluids are commonly present, but that their isotopic compositions may be masked or erased during later events such as the influx of meteoric waters (Rye 1993 Hedenquist and Lowenstem 1994). 

Like other Roman volcanoes, the Vico pyroclastic rocks contain xeno-liths of various origin, including bedrock fragments, intrusive equivalents of lavas, and cumulate rocks. These xenoliths often contain exotic minerals, such as Zr-Ti-Th-U-REE rich phases (e.g. britholite, baddelyite, and pyrochlore), which have been interpreted to be the result of deposition from late-magmatic fluids rich in incompatible elements (e.g. Della Ventura et al. 1999). 

Figure 7 Potential physical and chemical processes occurring in a magmatic-hydrothermal system, including the influence of magma dynamics in the chamber-conduit plumbing system, and interactions between magmatic fluids and the crust. These can strongly modulate the speciation and flux of various magmatic components emitted into the atmosphere, compheating the interpretation of geochemical measurements of surface emissions.

Banks D. A., Green R., Cliff R. A., and Yardley B. W. D. (2000) Chlorine isotopes in fluid inclusions determination of the origins of salinity in magmatic fluids. Geochim. Cosmochim. Acta 64, 1785-1789. 

Porphyry copper San Manuel, Kalamazoo, Arizona Convection in response to intrusion of a stock or dike Mixing of meteoric and magmatic fluids and cooling... 

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