Hydrothermal veins

Matsuhisa, Y., Morishita, Y. and Sato, T. (1985) Oxygen and carbon isotope variations in gold-bearing hydrothermal veins in the Kushikino mining area. Southern Kyushu, Japan. Econ. Geol, 80, 283-293. 

Shikazono, N. (1973) Sphalerite-carbonate-pyrite assemblage in hydrothermal veins and its bearing on limiting the environment of their deposition. Geochem. J. 7, 97-114. 

Hydrothermal vein deposits result from hydrothermal solutions. Hydrothermal solutions are essentially the residual hot solutions remaining after magmatic crystallisation (juvenile... 

Zinnwaldite Polylithionite Glauconite Pegmatites and high-T hydrothermal veins Marine sediments (green sands)... 

The VMS sulphides define a broadly conformable sheet 5-50 m below the base of the BLUC. This synformal surface of mineralisation generally coincides with the transition from ultramafic cumulates and strongly foliated metavolcanic rocks to an underlying sequence of metavolcanic rocks and interflow metawacke and metasiltstone rocks (Fig. 2). Sphalerite-pyrrhotite mineralisation in hydrothermal veins was also observed within the BLUC several km west of this study area. 

A U-bearing hydrothermal vein system related to the strongly peraluminous, high heat producing North Pole Stream granitic suite, north-central New Brunswick Canada... 

Higgins, N.C. 1985. Wolframite deposition in a hydrothermal vein system The Grey River tungsten prospect. Economic Geology, 80, 1297-1397. 

The minerals of the group are formed at comparatively low temperatures (less than 200°) in hydrothermal veins. 

Lumpkin, G. R., Day, R. A., McGlinn, P. J., Payne, T. E., Giere, R. Williams, C. T. 1999. Investigation of the long-term performance of betafite and zirconolite in hydrothermal veins from Adamello, Italy. Materials Research Society Symposium Proceedings, 556, 793-800. 

The apatite group minerals are the most abundant phosphorus-bearing minerals on Earth, typically as accessory minerals in basic to acidic igneous rocks, pegmatites, hydrothermal veins and cavities, carbonates, contact and regionally metamorphosed rocks, and sedimentary rocks (Deer et al. 1996). The principal members of the apatite group include fluoroapa-tite (Ca5(P04)3F), chloroapatite (Ca5(P04)3Cl), hydroxyapatite, and carbonate apatite (Ca5(P04, C03)3(F,0H)) (Deer et al. 1996). 

In natural crystals, whose growth processes cannot be directly observed, the difference in R is recorded as the difference in separation in growth banding (see Chapter 6). Based on these observations, several papers were reported in which the direction of flow of ore-forming fluid was evaluated in pegmatite and hydrothermal veins. In many cases in which the natural mineral crystals exhibited extensively malformed Habitus from that predicted by the structural form, the malformation could be considered to be due to the remarkable anisotropy involved in the environmental conditions, such as the directional flow of the solution, which is similar to the situation of growth of NaCl from solution in between two glass plates, as discussed above. 

Figure 13.2. Characteristics of chlorite crystals in hydrothermal veins using the decoration method [3].

The most effective representation for which activity-activity diagrams can be used is in geological situations where solutions are in contact with great reservoirs of fluid, such as sea-water for example. The activity of ions in solution will impose phase equilibria on the solids. In these instances, silicate mineralogy will be simple, most likely single-phase. Mono- or bi-mineral zones adjacent to hydrothermal veins can also be effectively represented on activity-activity diagrams. 

Jamesnnitc occurs in low- to moderate-temperature hydrothermal veins with other lead sulfosait minerals. Exceptional specimens arc found in Bolivia, at Poiosi and Oruro, and as choice felted masses on pyritc at Zacatecas in Mexico. Jamesonite is also found in Arkansas. Idaho, and Utah in the United Slates and in Ontario and British Columbia. Canada. It is named after the English mineralogist. Robert Jameson, from specimens obtained from Cornwall. England. It is a minor ore of lead. 

Figure 7. Local scale discriminant analysis plot ofTM model after subdividing groups into schist (S) and hydrothermal vein (V) rock types.

With the advent of stable isotope paleoaltimetry towards the turn of the millennium the stable isotope and tectonics communities have witnessed an increasing number of isotopic mineral proxies developed to address the long-term topographic histories of orogenic belts and continental plateaus. These proxies include calcite from paleosols (see for example Quade et al. 2007, this volume and references therein), fluvial and lacustrine rocks the phosphate and carbonate component of mammal teeth (Kohn and Dettman 2007, this volume and references therein), smectite and kaolinite from paleosols, weathered sediments and volcanic ashes (e.g., Chamberlain et al. 1999 Takeuchi and Larson 2005 Mulch et al. 2006a) as well as white mica from extensional shear zones and fluid inclusions in hydrothermal veins (e.g., Mulch et al. 

Several hundred phosphate minerals (see Mineralogy) are known, virtually aU of which are orthophosphates An exception is Canaphite, CaNa2P20y dHyO. The important mineral Apatite, Cas(P04)3X is found in igneous pegmatite rocks and hydrothermal veins. Fluoro-, Chloro-, and Hydroxyapatites are found (X = F, Cl, OH, respectively) as well as many substituted varieties. 

Hydrothermal ore deposits can contain local zeohtes (e.g. the Andreasburg sulfide deposit in Germany) arising from circulating hot fluids. Similarly, zeolites arise in hydrothermal veins and cavities in felspathic rocks like the Adamello granite in Italy. 

Schopf et al. (2002) and earlier work cited therein, found evidence for microbial fossils in Pilbara and Barberton material. The laser-Raman imagery reported by Schopf et al. (2002) demonstrated that the material was made of kerogen and they interpreted this as evidence for remains microbial life. Brasier et al. disputed the earlier work by Schopf and Packer (1987) and Schopf (1993) on Warrawoona material, constmcting a detailed case in which they reinterpreted the supposed microfossils of the earlier study as secondary artifacts of graphite in hydrothermal veins. However, Brasier et al. (2002) did report C isotopic results that are most easily (though not conclusively) interpreted as microbial. Thus although... 

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