Cycles geochemical

In the geochemistry of fluorine, the close match in the ionic radii of fluoride (0.136 nm), hydroxide (0.140 nm), and oxide ion (0.140 nm) allows a sequential replacement of oxygen by fluorine in a wide variety of minerals. This accounts for the wide dissemination of the element in nature. The ready formation of volatile silicon tetrafluoride, the pyrohydrolysis of fluorides to hydrogen fluoride, and the low solubility of calcium fluoride and of calcium fluorophosphates, have provided a geochemical cycle in which fluorine may be stripped from solution by limestone and by apatite to form the deposits of fluorspar and of phosphate rock (fluoroapatite [1306-01 -0]) approximately CaF2 3Ca2(P0 2 which ate the world s main resources of fluorine (1). 

E. K. Berner and R. A. Berner, Global Environment Water, Air, and Geochemical Cycles, Prentice Hall, Inc., Englewood Cliffs, N.J., 1996. 

Lasaga, A. C. (1980). The kinetic treatment of geochemical cycles. Geochim. Cosmoclhm. Acta 44, 815-828. 

Fig. 9-8 Histogram of dissolved solids of samples from the Orinoco and Amazon River basins and corresponding denudation rates for morpho-tectonic regions in the humid tropics of South America (Stal-lard, 1985). The approximate denudation scale is calculated as the product of dissolved solids concentrations, mean armual runoff (1 m/yr), and a correction factor to account for large ratios of suspended load in rivers that drain mountain belts and for the greater than average annual precipitation in the lowlands close to the equator. The correction factor was treated as a linear function of dissolved solids and ranged from 2 for the most dilute rivers (dissolved solids less than lOmg/L) to 4 for the most concentrated rivers (dissolved solids more than 1000 mg/L). Bedrock density is assumed to be 2.65 g/cm. (Reproduced with permission from R. F. Stallard (1988). Weathering and erosion in the humid tropics. In A. Lerman and M. Meybeck, Physical and Chemical Weathering in Geochemical Cycles," pp. 225-246, Kluwer Academic Publishers, Dordrecht, The Netherlands.)...

Berner, R. A., Lasaga, A. C., and Garrels, R. M. (1983). The carbonate-silicate geochemical cycle and its effect on atmospheric carbon dioxide over the past 100 million years. Am. J. Sci. 283, 641-683. 

Stallard, R. F. (1988). Weathering and erosion in the humid tropics. In "Physical and Chemical Weathering in Geochemical Cycles" (A. Lerman and M. Meybeck, eds), pp. 225-246. Kluwer Academic Publishers, Dordrecht, Holland, NATO ASI Series C Mathematical and Physical Sciences 251. 

Lasaga, A. C. (1981). Dynamic treatment of geochemical cycles global kinetics. In "Kinetics of Geochemical Processes" (A. C. Lasaga and R. J. Kirkpatrick, eds), pp. 69-110. Mineral. Soc. Amer., Washington, DC. 

Hudson R. J. M. et al. (1994). Modeling the global carbon cycle Nitrogen fertilization of the terrestrial biosphere and the "missing" CO2 sink. Global Bio-geochem. Cycles 8, 307-333. 

Andreae, M. O. (1986). The ocean as a source of atmospheric sulfur compounds. In "The Role of Air-Sea Exchange in Geochemical Cycling" (P. Buat-Menard, ed.). Reidel, Dordrecht. 

Li, Y. H. (1981). Geochemical cycle of elements and human perturbation. Geochim. Cosmochim. Acta, 45, 2037-2084. 

In this final section, the global cycles of two metals, mercury and copper, are reviewed. These metals were chosen because their geochemical cycles have been studied extensively, and their chemical reactions exemplify the full gamut of reactions described earlier. In addition, the chemical forms of the two metals are sufficiently different from one another that they behave differently with respect to dominant... 

Galloway, J. N. (1979). Alteration of trace metal geochemical cycles due to the marine discharge of wastewater. Geochim. Cosmochim. Acta 43, 207-218. 

Biodegradation. Under aerobic conditions, biodegradation results in the mineralization of an organic compound to carbon dioxide and water and—if the compound contains nitrogen, sulfur, phosphorus, or chlorine—with the release of ammonium (or nitrite), sulfate, phosphate, or chloride. These inorganic products may then enter well-established geochemical cycles. Under anaerobic conditions, methane may be formed in addition to carbon dioxide, and sulfate may be reduced to sulhde. 

In section 2.3 and in Chapter 3, it is shown that the formation of back-arc basins take important role for the mineralization (back-arc deposits (Kuroko deposits), epithermal Au veins) and global geochemical cycle. Thus, it must be worth considering the formation mechanism of back-arc basins. 

Hydrothermal Flux from Back-Arc Basin and Island Arc and Global Geochemical Cycle... 

It was shown in previous chapters that intense hydrothermal activities occurred in the Neogene age in and around the Japanese Islands under the submarine and subaerial environments. In this chapter the influence of these hydrothermal activities on the seawater chemistry, and the global geochemical cycle are considered. 

The As (arsenic) concentration of seawater is controlled by input of rivers, sedimentation on the seafloor, weathering of the seafloor, exchange between atmosphere and seawater, volcanic gas input, and hydrothermal input. Previous studies on the geochemical cycle of As have not taken into account the hydrothermal flux of As. Therefore, hydrothermal flux of As from back-arc, island arc and midoceanic ridges to ocean is considered below. 

Raymo, M.E., Ruddiman, W.F. and Froelich, P.N. (1988) Influence of late Cenozoic mountain building on ocean geochemical cycles. Geology, 16, 649-653. 

Tajika, E. (1992) Evolution of the atmosphere and ocean of the Earth global geochemical cycles of C,H,0,N, and S, and degassing history coupled with thermal history. Doctoral Thesis, University Tokyo, 416 pp. 

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