Dolomites geochemistry

Dolomite is one of the most abundant sedimentary carbonate minerals but its mode of formation and its surface properties are less well known than for most other carbonate minerals. As we have mentioned, the nucleation of dolomites and its structural ordering is extremely hindered. There is a general trend for the "ideality" of dolomite to increase with the age of dolomite over geological time (Morse and Mackenzie, 1990). Most dolomites that are currently forming in surfacial sediments and that have been synthesized in the laboratory are calcium-rich and far from perfectly ordered. Such dolomites are commonly referred to as "protodolomites . Morse and Mackenzie (1990) have reviewed extensively the geochemistry (including the surface chemistry of dolomites and Mg-calcites. 

Exploration geochemistry, geochronology, and tracer isotopic data of copper mineralisation in dolomitic rocks, Dos Parecis Basin, Rondonia,... 

Land LS (1980) The isotopic and trace element geochemistry of dolomite the state of the art. In Concepts and models of dolomitization. Soc Econ Paleontol Min Spec Publ 28 87-110 Lane GA, Dole M (1956) Eractionation of oxygen isotopes during respiration. Science 123 574-576... 

Sass E. and Bein A. (1989) Dolomites and salinity A comparative geochemical study. In Sedimentology and Geochemistry of Dolostones, SEPM Spec. Pub., Tulsa, OK, (in press). 

Figure 6.14 Idealized, end-member approaches to mineral saturation of groundwater, dissolving calcite or dolomite at 12°C and 1 bar total pressure. Open-system dissolution pathways are labeled with hxed values of PCOj- Closed-system pathways are labeled no CO2 added. Reprinted from Geochim. et Cosmochim. Acta, 35, D. Langmuir, The geochemistry of some carbonate ground waters in central Pennsylvania, 1023-45, 1971, with permission from Elsevier Science Ltd, The Boulevard, Langford Lane, Kidlington 0X5 1GB, U.K.

Burns, S.J., Baker, P.A. Showers, W.J. (1988) The factors controlling the formation and chemistry of dolomite in organic-rich sediments Miocene Drakes Bay Formation, California. In Sedimentology and Geochemistry of Dolostones (Eds Shukla, V. Baker. P.A.). Spec. Pubis int. Ass. Sediment. 43,41-52. Black-well Science, Oxford. 

Searl, A. Fallick, A.E. (1990) Geochemistry of some Dinantian dolomites from East Fife hydrothermal overprinting of early mixing-zone stable isotopic and Fe/Mn compositions. J. Geol. Soc. London, 147, 623-638. 

Qing, H. Mountjoy, E.W. (1994b) Rare earth element geochemistry of dolomites in the Middle Devonian Presqu ile barrier. Western Canada Sedimentary Basin implications for fluid-rock ratios during dolomitization. Sedimentology, 41, 787-804. 

Various kinds of rocks that form the crust of the earth include igneous rocks, such as granite and basalt meta-morphic varieties, such as schist and quartzite and layered sedimentary rocks, such as sandstone and shale. Most of them consist chiefly of minerals that are compounds of silicon. Much of the inorganic geochemistry of our surroundings is linked to the properties of this one element. Of all the common rock types, only limestone and dolomite are exceptions to the rule that rocks are predominantly aggregates of silicon compoimds. 

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