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Calcite factors affecting precipitation

Growth of Concretions In sedimentary rocks we commonly find concretions, that is, material formed by deposition of a precipitate, such as calcite or siderite, around a nucleus of some particular mineral grain or fossil. The origin of most concretions is not known but their often-spherical shape with concentric internal structure suggests diffusion as an important factor affecting growth. The rate of growth, if diffusion controlled, is readily amenable to mathematical... [Pg.794]

Fig. 5.59 Summary of factors affecting the observed fractionation between marine carbonate and kerogen ( sedimentary) assuming autotrophy is dominated by C3 photosynthesis (after Hayes et al. 1999). Calcite test precipitation is represented by Eppt (E J heterotrophic reworking of primary production is represented by E (e n t n.b. the effect of... Fig. 5.59 Summary of factors affecting the observed fractionation between marine carbonate and kerogen ( sedimentary) assuming autotrophy is dominated by C3 photosynthesis (after Hayes et al. 1999). Calcite test precipitation is represented by Eppt (E J heterotrophic reworking of primary production is represented by E (e n t n.b. the effect of...
The saturation state of aragonite (Fig. 24.5), on the other hand, is affected little by temperature. Aragonite remains supersaturated by a factor of about ten (one log unit) over the gamut of analyses. The supersaturation probably arises from the effect of orthophosphate, present at concentrations of about 100 mg kg-1 in Mono Lake water orthophosphate is observed in the laboratory (Bischoff et al., 1993) to inhibit the precipitation of calcite and aragonite. [Pg.365]

Surfactant adsorption on saltlike minerals, such as calcite and dolomite, is a more complex process and is less understood than adsorption on oxide surfaces. These minerals are relatively soluble and when in contact with an aqueous medium develop an interfacial region of complex composition (41—43). In addition to the two mentioned mechanisms of adsorption, covalent bonding, salt formation between surfactant and lattice ions at the solid surface, ion exchange of surfactant with lattice ions, and surface precipitation have been suggested as adsorption mechanisms (36, 43—47). The dissolution products of sparingly soluble minerals may interact with the surfactant, precipitate or adsorb at the solid surface, or lead to mineral transformations that affect surface composition and electrochemical properties (46, 48—52). All these factors can be expected to influence surfactant adsorption. [Pg.279]

Steefel Lichtner (1994) highlighted the need to take flow geometries into account when assessing the effects of host-rock alterations. They modelled diffusive and advective transport processes along a hyperalkaline fluid-filled fracture in marl and also perpendicular to it between fracture and matrix. Dolomite dissolution was found to result in increased permeability parallel to the fracture, and diffusion was responsible for the precipitation of a calcite front in the wall rock, thus isolating the fracture physically and chemically from the rock matrix. This may reduce the effective buffering and sorption capacity of the rock. The mechanisms which affect the transport properties of a host rock are shown in this work to depend on many different factors and may be far more complex than can easily be modelled or simulated in a laboratory. [Pg.200]


See other pages where Calcite factors affecting precipitation is mentioned: [Pg.153]    [Pg.492]    [Pg.296]    [Pg.447]    [Pg.366]    [Pg.97]    [Pg.167]    [Pg.2809]    [Pg.188]    [Pg.359]   
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